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Prismatic

prismatic

Take a moment and try to put yourself in the shoes of someone who's just landed a job on a development team. You pored over page after page of job postings, looking for the perfect combination of challenging, rewarding, and remotely attainable. You fretted over every last little detail of your resume and cover letter. You spent countless hours brushing up on algorithms and data structures practice questions, determined to be prepared for anything they might throw at you in a technical interview. You made it through round after round of phone screenings, technical interviews, cultural interviews, and executive interviews. Finally, seemingly against all odds, they offered you the job and you quickly accepted before they could change their minds. Congratulations! You are officially The New Person™. It takes about 7 seconds for the euphoria to fade and some harsh realizations to sink in: You probably don't know much about what the product or project you'll be working on does, and almost certainly not much about how anything works. actually actually You have no historical context for why things are the way they are, so you'll likely be asking lots of questions. That can be hard when you're The New Person™. You aren't familiar with the team's choices for various processes such as code reviews, version control management, release management, and countless others. You'll be expected to pick all this stuff up quickly, as they're essential for you to be productive at your job. You don't know about random idiosyncrasies that have been adopted by the team over time, things that probably aren't documented but people just "seem to know". You'll likely run headfirst into these things, which isn't great. In short, you feel like you have no idea what you're doing. It turns out that being The New Person™ is the worst. Being The New Person™ We've all been there. For many of us, probably more than once. It's just never much fun. Thinking back to my first job out of college, which was many years ago at a small startup company, I remember feeling all these same things. The thing I felt most strongly, however, was that I just wanted to contribute . Anything! So that I got some sense of accomplishment, certainly, but also to show my teammates that I wasn't just a waste of space! something These feelings of uncertainty when I was The New Person™ were hardly unique. In fact, many of the developers I've worked with and hired over the years have shared with me that they've felt these same sorts of negative emotions when they first started, and that they too felt the best way to overcome them was to just get accomplished as quickly as possible. something meaningful Improving the Onboarding Experience One of the jobs of being a manager is to ensure that every New Person™ is set up for success to the greatest extent possible. It's tremendously expensive to find, hire, and retain great talent, so it's critical that all new employees get started off on the right track. Getting new employees engaged quickly makes it much more likely that they decide to stick around instead of just continuing to job hunt. This is of course a team effort, and it won't work very well unless you have a good plan for getting the rest of the team involved. But for the moment, if we're saying that one of the first things to tackle is to help The New Person™ overcome these negative emotions, and that the best way to do that seems to be to help them accomplish something meaningful quickly, how can we formalize that as part of the onboarding process? Time to First Commit Through the years, my teams have had great success with onboarding in part by focusing on a metric called "Time to First Commit". It's exactly as it sounds: It's the time it takes from when The New Person™ first sits down at their desk to the time when they've landed their first commit to the version control system. The target you shoot for will probably vary depending on the nature of the application, your languages, frameworks, tools, and probably quite a few other factors. In general, I consider it success if The New Person™ is able to get their first commit in by the end of their first day. This metric has a couple of properties that make it especially effective: It's Comprehensive Time to First Commit encapsulates many different aspects of the developer experience. In order to commit code, a developer must have a fully configured development machine, security credentials assigned, source code checked out, often a task assigned in whatever issue tracking system you use, and at least some of the organization's various SDLC polices understood at a basic level. The processes around all of these things must be optimized, at least in part, to account for this metric. It's Quantitative Time to First Commit is a measurable quantity, which means that it's relatively easy to figure out where your team is at now, what a reasonable target might be, and then steps the team can take to drive towards achieving that goal. It means that as new tools are adopted and processes evolved over time, you can measure whether these things have positively or negatively impacted this metric and take the necessary steps to address any problems. For example, if a developer checks in a change that brings in some new dependency and hasn't documented how to set it up (or better yet, automated the setup), it's pretty likely you'll see a regression in this metric. Optimizing For Time to First Commit At Prismatic, we've focused quite a bit on two key areas that have helped improve Time to First Commit. Documentation Documentation is by no means glamorous, and if we're honest, nobody really likes writing it or maintaining it. But likes having it around. It's especially helpful if you're The New Person™ and you're just trying to figure out which end is up. At Prismatic, we have gone to great lengths to document as many things as we reasonably can. The nature of the documentation generally falls into one of two categories: everyone Things that tend to be pretty stable get added to our wiki in Notion. These are things like: Our preferred Git workflow, specifically around commit messages, branch names, rebasing/merging, etc. How we prefer to use Clubhouse, our issue tracking system Various tips on troubleshooting specific issues, either related to the development environment or the Prismatic application Things that tend to be more fluid get documented in Markdown files and committed to version control alongside the application source code, as in these cases the documentation often depends on the source code. Some examples are: Development environment setup guide. This is the most immediately important piece of documentation for The New Person™ on the team, so it's given the honor of being our repository's main README. It's the first thing they'll see when they go to browse the repository. Makefile target descriptions. Makefiles are somewhat self-documenting already, but some of our targets are a bit "bespoke", so having some additional documentation around what they are for and why you might use them is very helpful. Instructions for running both unit and end-to-end tests Recommended tools, editor plug-ins, etc. One of the nice things about having these files committed alongside the source code is that it means the documentation automatically becomes part of the code review process. We consider it a bug if an impactful change is made to the source code but not properly reflected in the documentation. Automation Things like setting up a new development environment, keeping dependencies updated, and managing application infrastructure changes often boil down to following a series of steps. Well, guess what? It turns out that computers are at following a series of steps. So make the computer do the work! The trick of course is describing the steps that they should follow. That's where automation tooling comes in. super good We're still a pretty small team at Prismatic, so we knew that investing early on in automation would have tremendous payoff as our team continues to scale and as the application itself continues to grow in both capability and complexity. This has an additional benefit in that it significantly reduces the stress for a New Person™ joining the team, as they can be up and running with a fully configured environment in just a couple hours. A few of the more impactful examples of automation that we're using at Prismatic are: Terraform. Terraform is an incredibly powerful system and it's what we use to manage the infrastructure for all our development, CI, demo, and production systems. Applying changes is usually as simple as running a single make target. Docker. Docker provides an excellent way to programmatically describe the infrastructure for individual resources. Rather than make every developer install and manage a bunch of local instances of Postgres, Redis, etc., we have Dockerfiles that describe these resources. Updating to the latest and greatest is a simple as git pull and then running a single make target to recreate the images and redeploy. Git hooks. It's a pain having to remember to run yarn install or poetry install after pulling in somebody else's changes. If you forget to do it right away you'll likely run into strange runtime bugs, which is very frustrating. So again, make the computer do it! We use Husky to automatically download and install new library dependencies automatically after issuing git pull, thereby eliminating this class of problems from the start. Makefiles. Sure, there are about a thousand "task runner" tools these days, but it seems that Make has seen a resurgence in popularity as of late. Why? Well, maybe because it's pretty simple to use, installed by default basically everywhere, and it mostly Just Works™. Sure, targets can get complicated and the syntax can be weird. But in those cases you're better off writing a separate script and calling it from your Makefile anyway. At Prismatic, dozens of the most common development tasks are exposed via a couple different Makefiles, so our developers always have a pretty consistent user interface. This is so much simpler than trying to remember what scripts are where, what arguments they take, etc. Between having comprehensive, up-to-date documentation and automation around most common development tasks, we've been able to get Time to First Commit as quick as a few hours, with everyone thus far easily managing it on their first day. We will continue to pay close attention so that as our systems and processes scale in complexity, as they always seem to, we will keep that first day experience as painless as possible for The New Person™. Previously published at https://prismatic.io/blog/the-new-person/

Streamlining The Developer Onboarding Process: A How-To Guide

The Problem with Publicly Accessible AWS Resources When you first develop infrastructure for a new project, you naturally optimize for rapid development. You want to get something - anything - out the door, and you therefore want to be able to write code and debug issues quickly. Because of that, it's awfully tempting to spin up servers and databases in public subnets so that you can readily connect to them for debugging sessions. It's nice to be able to to do some live code debugging, or to assess the current state of your database. ssh my-user@my-web-server psql -U my-user -h my-database-instance Sure, AWS allows you to do that. You expose SSH on your webservers and you expose your AWS Relational Database Service (RDS) and Redis/ElastiCache servers to the internet for easy access. But should you? Exposing databases and servers publicly yields a pretty obvious security issue: your sensitive data is directly accessible to anyone on the internet. can can You might argue "it's fine; we lock down our VPC security groups so that only people from our office IP can access our EC2, RDS, or ElastiCache instances. Other people on the internet are blocked because of their IP addresses". While that's true - locking down your resources this way is better than nothing - this strategy yields two pitfalls: Allowing anyone from your office IP address to access your AWS resources is still a security issue. Should guests on your wifi, or John the junior developer really have access to production databases? By locking down your resources by public IP, it's pretty hard to discriminate between DevOps users and the rest of your organization - everyone likely uses the same public IP address. Plus, as your organization grows, more attack vectors are created. A single compromised user on your network can wreak havoc on your production systems. Your remote workers are going to struggle to hit resources. If your employees are working from home (which, in this COVID-riddled year, they very likely are), you will either need your employees to maintain a VPN connection to your office, or you will need to maintain a whitelist of all of your employees' home IP addresses. If your employees happen respond to an outage from an airport or coffee shop, they might spend minutes (hours?) manually monkeying with VPC security groups before they can even get access to address the outage. This is a problem that I've had to solve everywhere that I've worked, so I imagine it's a problem others have had to face, too. Let's look at how to do it right, optimizing for both security and accessibility at the same time. Enter AWS Systems Manager Let's suppose you've followed security protocols, and have placed your various AWS resources (EC2, RDS, ElastiCache, etc.) into private subnets and removed public access to them. How can you securely grant access to members on your team (like your senior devs and DevOps) who need them? AWS provides to let you inspect and access your AWS resources - even those residing in private subnets. With Systems Manager, users exchange their AWS credentials for temporary shell access to EC2s. They can get that access both on the CLI, and through the AWS web console. Systems Manager To enable access to your EC2s, simply install the onto the servers that you spin up. Good news - if you're building your servers off of Amazon Linux, macOS, Ubuntu Server, or some Amazon-provided Windows Server images, the SSM agent is already installed for you - you just need to turn on a machine and grant it a specific role defined in AWS's . AWS SSM agent What's the deal with the extraneous "S" in "SSM", you might ask? It's historical - Systems Manager used to be called "Simple Systems Manager" and the extra "S" stuck - just go with it. docs Once you have an EC2 with the SSM agent installed, you can open a shell into your instance with the CLI tool: aws $ aws ssm start-session --target i-0b6c737cc21dc01a9

Starting session with SessionId: treece-0bf6ff366c16d651f
sh-4.2$ whoami
ssm-user
sh-4.2$ cat /etc/system-release
Amazon Linux release 2 (Karoo) When you have the SSM agent installed, you don't need to worry about juggling IP whitelists. Your systems management teams can access resources from anywhere (the office, at home, or even a coffee shop) using their AWS credentials. And, without AWS credentials John the junior dev has no access to production databases. Sorry, John! What About Accessing RDS or ElastiCache? With AWS Systems Manager you can remote into EC2s, but what about databases like PostgreSQL/RDS or Redis/ElastiCache? AWS doesn't allow you to directly SSH into the systems running RDS or ElastiCache. Instead, I suggest spinning up a minimal EC2 instance called a in your VPC that you can remote into with Systems Manager. You can remote into the and once there you can access your databases. bastion bastion, Make sure that you assign your bastion a VPC security group, and create ingress rules so that your RDS and ElastiCache security groups allow access from your bastion security group. Once you have all that set up, you can access your databases from the command line on the bastion: $ aws ssm start-session --target i-0b6c737cc21dc01a9

Starting session with SessionId: treece-048a3bf2269ad7caf
sh-4.2$ psql -h 10.0.2.88 -U testuser postgres
Password user testuser: 
SSL connection (cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256)
Type .

postgres=> CREATE TABLE users (id INT, email VARCHAR(40));
CREATE TABLE for "help" for help You might ask, "can't I just spin up a bastion in a public subnet, and SSH into it?" Yes and no.  Yes, you can totally do that. No, it's not a good idea - that opens up the same security vulnerabilities that leaving your servers and databases in public subnets does. Tunnels... Tunnels Everywhere At this point, we have options for remoting in to EC2s directly through Systems Manager, and we can access our databases indirectly via a bastion EC2. The last thing I want to look at is leveraging SSH tunnels through the bastion to access database resources as though they're locally accessible. That way, you can connect your favorite database GUI, like to your RDS instances. pgAdmin First, we need to get an SSH public key into our bastion. I'll assume you already have a key in . We'll use the CLI to temporarily load up that key for user into our bastion: $HOME/.ssh/id_rsa.pub aws ssm-user $ aws ec2-instance-connect \
    send-ssh-public-key \
    --availability-zone us-east-1a \
    --instance-id i-0b6c737cc21dc01a9 \
    --instance-os-user ssm-user \
    --ssh-public-key file:// /.ssh/id_rsa.pub
{ : , : } $HOME "RequestId" "f8f3db2a-3107-4c0a-ae3d-94e2d7fff620" "Success" true Next, I'm going to modify my laptop's file so that servers starting with will proxy their connections through the command we used earlier. I'll add: $HOME/.ssh/config i- aws ssm start-session host i-*
    ProxyCommand sh -c "aws ssm start-session --target %h --document-name AWS-StartSSHSession --parameters 'portNumber=%p'" Now, I can simply to access my instance: ssh ssm-user@INSTANCE-ID $ ssh ssm-user@i-0b6c737cc21dc01a9
Last login: Tue Dec 15 20:27:34 2020 from localhost

       __|  __|_  )
       _|  (     /   Amazon Linux 2 AMI
      ___|\___|___|

https://aws.amazon.com/amazon-linux-2/
10 package(s) needed security, out of 22 available
Run to apply all updates.
[ssm-user@ip-10-0-0-71 ~]$ ls
file.txt system.log
[ssm-user@ip-10-0-0-71 ~]$ for "sudo yum update" Now that I have SSH access to my bastion (even though it's in a private network that's not accessible from the internet!) I can spin up SSH tunnels like I would with any other SSH connection. To create a tunnel to my RDS instance, for example, I can simply run: $ ssh ssm-user@i-0b6c737cc21dc01a9 -NL 5000:10.0.2.88:5432 And then from a separate shell I can access my database "locally" on port 5000: $ psql -h localhost -p 5000 -U testuser postgres
Password user testuser: 
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: off)
Type .

postgres=> \dt
         List of relations
 Schema | Name  | Type  |  Owner   
--------+-------+-------+----------
 public | users | table | testuser
(1 row) for "help" for help Cool, huh? Using tunnels through your bastion you can access any resources that reside in your private network without needing to expose them to hooligans on the internet... or John the junior dev. Previously published at https://prismatic.io/blog/connect-to-aws-resources-with-ssh/

Connecting Securely to Private AWS Resources by Using SSH Tunnels and Bastion Hosts

[ 🔔] goes your email notification. You’ve just been assigned a new ticket. The subject line reads “Integrate our app with Acme CRM.” The ticket’s description is pretty sparse - just a few bullet-points saying things like: ding Sync users’ appointments in Acme with our calendar app Track the number of email and phone touch-points users have in Acme on our dashboard You expected this. A lot of the businesses that use your software also use Acme CRM, and you’ve been hearing from your sales and support teams that customers keep asking for their Acme data to sync with your app. So.... it’s up to you to build the integration with Acme. Where do you even begin? I know I’m always inclined to fire up my IDE and dive right in to code, but that always results in misunderstanding expectations, missing details, and having to redo work. Let’s talk about the stuff you should do you start coding. Let’s think through the questions you should ask, requirements you should clarify, and tools you can reach for to get a feel for how the integration is going to work. before Gather Requirements for Your Integration Project In an ideal world, the person requesting the integration would provide you with a specification that details what events trigger the integration to run, what type of data gets sent over, and how the data should look when it arrives at its destination. The world’s rarely ideal, though, so you’ll probably have to go digging for clearer integration requirements. It’s incredibly helpful to have a series of “When then ” statements. For example, “When a user in Acme CRM sets an appointment with a customer, a calendar event is created in our app that contains the customer’s name, phone number, email address, and time of the appointment.” Bonus points if you can tie each step to relevant API documentation! foo bar As you think through the “when then ” statements, there are several companion questions you should be asking with regards to how data should flow from one system to another: foo bar What triggers an integration to run? Does Acme support events like webhooks (where they send data whenever it’s been changed) or are you expected to fetch data on a schedule? Is this a one-way or two-way integration (that is, will Acme just send data to your app, or does your app also need to send data back to Acme)? What’s the format of the data the source system is sending? JSON? XML? CSV? What information is included in the payload that’s sent your way? What format of data is the destination system expecting? You may need to fetch more information from other third-parties or Acme’s other API endpoints to satisfy the destination’s requirements. After you have a sense of how data will flow, ask yourself what things could go wrong, and clarify how your integration needs to behave in these common situations: How should you deal with data “collisions” where the same data gets sent over twice? Should you ignore the second request, create a second record, or update (”upsert”) the existing data? What should happen if incomplete or “bad” data is shipped (a calendar event that’s missing date, for example)? Do you need a “dead letter queue” to store data that causes your integration to error out so your devs or support folks can examine the bad data later? What happens if either API is down? Is your integration expected to hold on to data and retry later? Next, figure out how configurable you need this integration to be. (Occasionally, I’ve needed to build “one-off” integrations for a single customer. Far more often, I’ve needed to build reusable integrations that can behave differently from customer to customer and handle each customer’s credentials for the third-party app.) How do users authenticate with each system? Do users have their own credentials to Acme, or some shared key? Where are you going to store those secrets securely? What things are going to be different between customers you deploy this integration to? Do customers have different API endpoints, or data mapping requirements? What all needs to be configurable to make it so you can deploy the same integration to multiple customers? Finally, figure out deployment and support concerns. If your company has several app integrations already, you may already have answers to these questions: How will your customers activate and configure the integration? Do you need to build UX for this? What are the expectations for logging, monitoring and alerting? Where should the integration’s logs be sent, and under what conditions should someone be alerted if the integration runs into a problem? Where is the integration itself going to live? Will you need to build custom infrastructure to host this integration? As you can see, a quick bullet point spec like “Import users’ appointments into the our calendar” seems simple at first, but there’s a ton of things to think through if you want to build, deploy and support your integration thoroughly. Get Familiar With How the Third-Party App Works Once you’ve thought through all of the questions above and have a solid understanding of the task at hand, it’s time for you to familiarize yourself with the third-party app(s) involved. I recommend logging in to Acme CRM like an end user would. Figure out what exactly it means to “set an appointment” or “log a phone call with a customer” in the context of Acme. This should give you a sense of how different objects that the application stores are related. If you don’t have an Acme CRM account, ask for one. It’s mutually beneficial for both your company and Acme to have an integration between your systems, and most reasonable companies are willing to provide a free developer account or “sandbox” environment where you can toy around with dummy data, without needing to access your users’ real Acme data. You may be provided written information about how the other application will provide data to you, but I recommend that you insist on getting a real sandbox environment that at least sends fake data in the format the third party says they use. I’ve been around for plenty of integrations where a third party claims they’ll send XML in thus-and-such a format using REST calls, but informs you after you build your integration that they decided to write out JSON messages to a message broker (like Kafka or Amazon SNS) instead. Testing with an actual system is far better than mocking out fake APIs and message streams yourself. You can just change your code quick to subscribe to an SNS feed, right? It sounds silly, but also make sure to log in to your own app as well to verify that you know what it means to “create a calendar event” or “update the dashboard.” Verify with the people requesting the integration that you understand what actions should trigger the integration, and where the data should be displayed when it arrives at its destination. Explore the API with an HTTP client You’re ready to start fiddling with APIs, but it’s not quite time to code quite yet. Take a look at Acme’s developer docs. If they have an OpenAPI/Swagger or WSDL spec that defines all for their API endpoints, you’re in luck! Figure out how their auth flow works, what data their webhooks send, and what data is available for you to query. If you’re really lucky, Acme will provide a client library you can use when it’s time to start coding (but don’t get your hopes up!). Fire up your favorite HTTP client (I personally like ), and try to make some simple authenticated GET and POST requests against the Acme CRM sandbox you have access to. Verify that the third-party docs are correct, and that you can, indeed, fetch data from their appointment API endpoint. Double-check that the payload you receive has all the information you need to map data over to your app. Postman Once you have requests to Acme CRM working in Postman (or your favorite HTTP client), finally turn to code. Time to build! Now that you have a good idea of the shape of data that comes in, where additional data should be fetched from, how it should be modified and where it should wind up, it’s time to start building your integration. There’s still a lot to do - you need to write your code, make it configurable enough to handle differences between customers, deploy it, monitor and support it, make the integration available within your product, etc., but asking the right questions and taking the proper steps beforehand can make all that go faster and keep rework to a minimum.

How to Build an Integration to Another App

ZUG, Switzerland, December 5th, 2024, Chainwire/--Holyheld, a leading Swiss crypto payments startup, announced today that it has secured funding to accelerate BRRR protocol with investment from Toyota Ventures, TempleDAO, Tomahawk VC, Prismatic Capital, Zee Prime Capital, Polygon, Kosmos Ventures, Moonlanding Ventures, as well as from angel investors from leading projects including Lido, Olympus, Dinero, Paragon, Superfluid, vfat, Inverse Finance, Daedalus, DCV, Generative Ventures, and Vamient. In an effort to fill the critical infrastructure necessary for users to transact globally with merchants instantly, Holyheld’s BRRR protocol aims to connect public blockchain networks, traditional payment, and card networks to create a global layer of real-time payments. “This opportunity consolidates our lead in the market, and fuels our drive to redefine how real-time clearing of payments should work,” said Anton Mozgovoy, Holyheld CEO. “With our technology of global stablecoin orchestration, we’re well-positioned to transform how users and businesses conduct business today with payments of tomorrow.” BRRR’s protocol is used to power Holyheld’s app, a leader in the European market in the segment of Web3 payments apps, which offers a cash account with a debit card available to residents of 30 European countries. Users of the Holyheld app can connect any self-custody wallet and use their cryptocurrency for daily purchases. This enables traditional consumer behaviors, like swiping or tapping a credit card or mobile device for payment, while users maintain self-custody of their funds. “This funding is an essential step as we work towards our vision of enabling crypto customers and fintechs to build new payment settlement and reconciliation solutions using crypto.” Dr. Anton Zagorodnikov, Holyheld co-founder and CTO, added. The new funding will allow Holyheld to continue expanding the protocol to more clients and payment networks globally. Holyheld has integrated over one hundred leading crypto protocols across 15 blockchain networks. The company’s BRRR has also orchestrated over $100M in volume since its launch in April of 2023. “Holyheld turns any self-custody wallet into a personal IBAN and a debit card, which enables users to have a frictionless digital wallet experience,” said Chris Abshire, principal, Toyota Ventures. “We are excited to work with Holyheld’s team as they build the leading on-chain clearing house.” To learn more about Holyheld, users can visit https://holyheld.com/ or https://holyheld.com/BRRR About Holyheld Founded in 2022, Holyheld is committed to enabling crypto customers and fintech to build new payment settlement and reconciliation solutions using stablecoins. With offices in Zug, Switzerland and Vilnius, Lithuania, the company’s first product is a Web3 debit card that allows users to make traditional payments with digital assets. Holyheld’s Blockchain Reconciliation and Remittance Record (BRRR) protocol enables consumers who are invested in blockchain-related assets to have significant purchasing power in the real world. To learn more about Holyheld, users can visit https://holyheld.com/ or https://holyheld.com/BRRR. Contact Holyheld Labs hello@holyheld.com This story was distributed as a release by Chainwire under HackerNoon’s Business Blogging Program. Learn more about the program here ZUG, Switzerland, December 5th, 2024, Chainwire/--Holyheld, a leading Swiss crypto payments startup, announced today that it has secured funding to accelerate BRRR protocol with investment from Toyota Ventures, TempleDAO, Tomahawk VC, Prismatic Capital, Zee Prime Capital, Polygon, Kosmos Ventures, Moonlanding Ventures, as well as from angel investors from leading projects including Lido, Olympus, Dinero, Paragon, Superfluid, vfat, Inverse Finance, Daedalus, DCV, Generative Ventures, and Vamient. In an effort to fill the critical infrastructure necessary for users to transact globally with merchants instantly, Holyheld’s BRRR protocol aims to connect public blockchain networks, traditional payment, and card networks to create a global layer of real-time payments. “This opportunity consolidates our lead in the market, and fuels our drive to redefine how real-time clearing of payments should work,” said Anton Mozgovoy, Holyheld CEO. “With our technology of global stablecoin orchestration, we’re well-positioned to transform how users and businesses conduct business today with payments of tomorrow.” “This opportunity consolidates our lead in the market, and fuels our drive to redefine how real-time clearing of payments should work,” said Anton Mozgovoy, Holyheld CEO. “With our technology of global stablecoin orchestration, we’re well-positioned to transform how users and businesses conduct business today with payments of tomorrow.” BRRR’s protocol is used to power Holyheld’s app, a leader in the European market in the segment of Web3 payments apps, which offers a cash account with a debit card available to residents of 30 European countries. Users of the Holyheld app can connect any self-custody wallet and use their cryptocurrency for daily purchases. This enables traditional consumer behaviors, like swiping or tapping a credit card or mobile device for payment, while users maintain self-custody of their funds. “This funding is an essential step as we work towards our vision of enabling crypto customers and fintechs to build new payment settlement and reconciliation solutions using crypto.” Dr. Anton Zagorodnikov, Holyheld co-founder and CTO, added. “This funding is an essential step as we work towards our vision of enabling crypto customers and fintechs to build new payment settlement and reconciliation solutions using crypto.” Dr. Anton Zagorodnikov, Holyheld co-founder and CTO, added. The new funding will allow Holyheld to continue expanding the protocol to more clients and payment networks globally. Holyheld has integrated over one hundred leading crypto protocols across 15 blockchain networks. The company’s BRRR has also orchestrated over $100M in volume since its launch in April of 2023. “Holyheld turns any self-custody wallet into a personal IBAN and a debit card, which enables users to have a frictionless digital wallet experience,” said Chris Abshire, principal, Toyota Ventures. “Holyheld turns any self-custody wallet into a personal IBAN and a debit card, which enables users to have a frictionless digital wallet experience,” said Chris Abshire, principal, Toyota Ventures. “We are excited to work with Holyheld’s team as they build the leading on-chain clearing house.” “We are excited to work with Holyheld’s team as they build the leading on-chain clearing house.” To learn more about Holyheld, users can visit https://holyheld.com/ or https://holyheld.com/BRRR https://holyheld.com/ https://holyheld.com/ https://holyheld.com/BRRR https://holyheld.com/BRRR About Holyheld Founded in 2022, Holyheld is committed to enabling crypto customers and fintech to build new payment settlement and reconciliation solutions using stablecoins. With offices in Zug, Switzerland and Vilnius, Lithuania, the company’s first product is a Web3 debit card that allows users to make traditional payments with digital assets. Holyheld’s Blockchain Reconciliation and Remittance Record (BRRR) protocol enables consumers who are invested in blockchain-related assets to have significant purchasing power in the real world. To learn more about Holyheld, users can visit https://holyheld.com/ or https://holyheld.com/BRRR . Blockchain Reconciliation and Remittance Record (BRRR) protocol Blockchain Reconciliation and Remittance Record (BRRR) protocol https://holyheld.com/ https://holyheld.com/ https://holyheld.com/BRRR https://holyheld.com/BRRR Contact Holyheld Labs hello@holyheld.com This story was distributed as a release by Chainwire under HackerNoon’s Business Blogging Program. Learn more about the program here This story was distributed as a release by Chainwire under HackerNoon’s Business Blogging Program. Learn more about the program here here here

Holyheld Raises Funding To Launch Blockchain Reconciliation And Remittance Record

Holyheld تجمع التمويل لإطلاق سجل التسوية والتحويلات المالية عبر تقنية Blockchain

Holyheld, Blockchain uzlaşması və pul köçürmə rekordunu işə salmaq üçün vəsait toplayır

Holyheld recauda fondos para lanzar un sistema de reconciliación y registro de remesas basado en blockchain

Holyheld lève des fonds pour lancer un service de réconciliation et de transfert de fonds basé sur la blockchain

Holyheld raccoglie fondi per lanciare la riconciliazione blockchain e il registro delle rimesse

Holyheld が資金を調達し、ブロックチェーンによる決済と送金記録を開始

Holyheld Azwi Misolo Pona Ko Lancer Dossier Ya Reconciliation Na Remise Ya Blockchain

Holyheld piesaista finansējumu, lai uzsāktu blokķēdes saskaņošanas un pārskaitījumu ierakstu

Holyheld Qullqita Huñun Blockchain Reconciliación hinaspa Remesas Record nisqa qallarinanpaq

Holyheld барои оғози сабти мусолиҳаи Blockchain ва интиқоли маблағ маблағ ҷамъ мекунад

ሆሊሄልድ መዝገብ ዕርቂን ሓዋላን ብሎክቸይን ንምጅማር ምወላ ኣዋህሊሉ።

Holyheld збирає фінансування для запуску блокчейн-звірки та запису грошових переказів

Authors: (1) Ruohan Zhang, Department of Computer Science, Stanford University, Institute for Human-Centered AI (HAI), Stanford University & Equally contributed; zharu@stanford.edu; (2) Sharon Lee, Department of Computer Science, Stanford University & Equally contributed; zharu@stanford.edu; (3) Minjune Hwang, Department of Computer Science, Stanford University & Equally contributed; zharu@stanford.edu; (4) Ayano Hiranaka, Department of Mechanical Engineering, Stanford University & Equally contributed; zharu@stanford.edu; (5) Chen Wang, Department of Computer Science, Stanford University; (6) Wensi Ai, Department of Computer Science, Stanford University; (7) Jin Jie Ryan Tan, Department of Computer Science, Stanford University; (8) Shreya Gupta, Department of Computer Science, Stanford University; (9) Yilun Hao, Department of Computer Science, Stanford University; (10) Ruohan Gao, Department of Computer Science, Stanford University; (11) Anthony Norcia, Department of Psychology, Stanford University (12) Li Fei-Fei, 1Department of Computer Science, Stanford University & Institute for Human-Centered AI (HAI), Stanford University; (13) Jiajun Wu, Department of Computer Science, Stanford University & Institute for Human-Centered AI (HAI), Stanford University. Table of Links Abstract & Introduction Brain-Robot Interface (BRI): Background The NOIR System Experiments Results Conclusion, Limitations, and Ethical Concerns Acknowledgments & References Appendix 1: Questions and Answers about NOIR Appendix 2: Comparison between Different Brain Recording Devices Appendix 3: System Setup Appendix 4: Task Definitions Appendix 5: Experimental Procedure Appendix 6: Decoding Algorithms Details Appendix 7: Robot Learning Algorithm Details Appendix 3: System Setup The robot we use in our tabletop manipulation task is a standard Franka Emika robot arm with three RealSense cameras. For mobile manipulation, we use a Tiago++ model from PAL Robotics, with an omnidirectional base, two 7-degrees-of-freedom arms with parallel-yaw grippers, a 1-degree-of-freedom prismatic torso, two SICK LiDAR sensors (back and front of the base), and an ASUS Xtion RGB-D camera mounted on the robot’s head, which can be controlled in yaw and pitch. All sensors and actuators are connected through the Robot Operating System, ROS [74]. The code runs on a laptop with an Nvidia GTX 1070 that sends the commands to the onboard robot computer to be executed. Robot platform. A list of primitive skills along with their parameters can be found in Table 6, eight for Franka (16 tasks) and five for Tiago (four tasks). Human users can accomplish all 20 tasks, which are long-horizon and challenging, using these skills. Primitive skills list. This paper is under CC 4.0 license. available on arxiv

NOIR: Neural Signal Operated Intelligent Robots for Everyday Activities: Appendix 3

Scientific American Supplement, No. 365, December 30, 1882 by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book . APPARATUS FOR MEASURING ELECTRICITY AT THE UPPER SCHOOL OF TELEGRAPHY. here APPARATUS FOR MEASURING ELECTRICITY AT THE UPPER SCHOOL OF TELEGRAPHY. —On a former occasion I described an instrument to which, in 1873, I gave the name , and which is nothing else than a tuning fork whose motion is kept up electrically in such a way as to last indefinitely, provided that the elements of the pile are renewed gradually, and that from time to time the metallic contact is changed, which causes, at every oscillation, the current to pass from the pile into the magnet, which keeps up the vibration. Electro Tuning Forks and their Uses. Electro-Tuning Fork We reproduce herewith, in Fig. 1, a cut showing in projection one of the simplest forms of the apparatus. If we imagine the platinum or steel style, , of the figure to be done away with, as well as the platinized plate, I, and its communication with the negative pole of the pile, P, we shall have the ordinary instrument kept in operation electrically by the aid of the electro-magnet, E, the style, , the interrupting plate, I, and the pile. s s If we preserve the parts above mentioned, the instrument will possess the property of having vibrations of a constant amplitude if sufficient energy be kept up in the pile. In fact, when the amplitude is sufficiently great to cause the style, , to touch the plate, I, it will be seen that at such a moment the current no longer passes through the electromagnet, and the vibration is no longer maintained. The amplitude cannot exceed an extent which shall permit the style, , to touch I. s s Under such conditions, the duration of the vibrations remains exactly constant, as does also the vibratory intensity of the entire instrument. The measurement of time, then, by an instrument of this kind is, indeed, as perfect as it could well be. This complication in the arrangement of the apparatus has no importance as regards those tuning forks the number of whose vibrations exceeds a hundred per second, for in such a case these are given an amplitude of a few millimeters only; but it would be of importance with regard to instruments whose number of vibrations is very small, and to which it might be desirable to give great amplitude; for then, as I have long ago shown, the duration of the oscillation would depend a little on the amplitude, but a very little, it is true. I shall not refer now to the applications of these instruments in chronography, but will rather point out first the applications in which they are destined to produce an effective power. For this purpose it is necessary to make them pretty massive. The number of the vibrations depends upon such massiveness, and it is necessity to know the relation which exists between these two quantities in order to be able to construct an instrument under determinate conditions. I made in former years such a research with regard to tuning forks of prismatic form, that is to say, of a constant rectangular section continuing even into the bent portion where the parallel branches are united by a semicylinder, at the middle of which is the wrought iron rod as well as the branches. The of the instrument is the dimension parallel to the vibrations; its is the dimension which is perpendicular to them, and its is reckoned from the extremity of the branches up to the middle of the curved portion. thickness width length It is found that the number of vibrations is independent of the width, proportional to the thickness, and very nearly inverse ratio of the square of the length, provided the latter exceeds ten centimeters. If we represent the length by , the thickness by , and the number of vibrations by , we shall have the following formula: l e n = × ( / 2) n k e l in which is a constant quantity whose value depends upon the nature of the metal of which the tuning fork is made. k This constant varies very little from steel to malleable cast iron, and it may be taken as equal to 818270. Thus, then, we have a means of constructing a tuning fork in which two of the three quantities, , , , are given in advance. Experience proves that no errors are committed exceeding one or two per cent. n e l It is seen from this that there is a means of increasing the mass of the instrument without changing anything in the thickness, the length or, consequently, the number of vibrations, and this is by increasing the . breadth It is in this way that I have succeeded in having long massive tuning forks made of malleable iron, giving no more than 12 to 15 vibrations per second, and vibrating with perfect regularity. Fig. 2, annexed, shows one of these instruments of about 55 centimeters length, whose breadth, E, is from 5 to 6 centimeters, and which makes about fifteen double vibrations per second only. This number might be still further reduced, but at the expense of our being led to exaggerate the longitudinal dimensions of the apparatus in such a way as to make it inconvenient. The object may be attained more simply by loading the branches with slides supporting leaden weights, M, of 500 grammes each. By fixing these slides at different points on the branches, the number of vibrations can be made to vary from simple to double, and even triple. Thus, by fixing them at the extremity of the branches the number of the vibrations is reduced to 5 or 6. There will be seen in the figure the electro-magnet which keeps up the vibration. This is formed of three simple electro-magnets, whose bobbins have a resistance of no more than 10 ohms, and which are united in series. The interrupting plate, P, against which the style, , rests at each vibration, is capable of a forward movement, or one of recoil, by the aid of a screw, V, and of an eccentric movement which is produced by a small handle, , and during which its plane remains invariable. This arrangement permits the point of contact of the style and plate to be varied without changing the precision with which the contact takes place, and all the points of the plate to be slowly used in succession before replacing it. The motion is produced by means of a relatively weak pile, whose poles are connected to the terminals, A and A'. Three Callaud elements of triple surface, renewed one after the other every month at the most, are sufficient to keep up the vibrations continuously, day and night, without interruption, and that too even when the instrument is employed in producing a small mechanical power, as we shall see further on. s m We have now seen how electro-tuning forks may be constructed of large dimensions, of large mass, and giving a small number of vibrations per second. Such instruments are well fitted to perform the role of electrical interrupters, and it was in such a character that one of them figured in the Exhibition of the Upper School of Telegraphy as a type of an interrupter for testing piles. When it is desired to test a pile to ascertain the practicability of employing it in telegraphy, it is necessary to make it perform a work which shall be as nearly as possible identical with that which it will be called on to do, until it is used up, to estimate the duration of such work, to measure regularly the constants of the pile, the electro-motive power, and the internal resistance. Usually, in telegraphy, this work consists in sending over a line of a certain resistance intermittent currents, through the intermedium of suitable manipulators. It suffices then to cause the branches of the electro tuning fork to play the role of one of these manipulators. For doing this the tuning fork carries two insulating ebonite or ivory strips, B B (Fig. 3), which, at every oscillation, abut against vertical brass springs, . Each of these latter is located in front of the platinized point of a screw, , which is affixed to a small metallic tongue. The springs and tongues are insulated from each other, and are mounted on a piece which may be moved by a screw, V, so as to cause the springs of the strips, B B', to approach or recede according to the amplitude of the instrument's vibrations. Each spring and tongue is connected with terminals affixed to the base of the apparatus. One of the poles of one element, P, of the pile is connected with the tongue and corresponding screw, while the other pole is connected with the screw in front of it through the intermedium of a galvanometer, 2, which gives the intensity of the intermittent current, and of a resistance coil, 2, which performs the role of an artificial telegraph line. The apparatus being set in operation, it will be seen that the current from the pile is emitted once at every vibration. r v g b Thus there may be exhausted as many pile elements as there are springs, and that, too, simultaneously; and the contacts of the screws and springs can be regulated in such a way that the duration of the emissions shall be the same for all. At the laboratory of the School of Telegraphy one of these instruments has operated without interruption, day and night, during eighteen months. The apparatus shown in Fig. 4 is also an interrupting electro-tuning fork, but it makes a much greater number of vibrations than the preceding, and may serve for other electric tests. The operation of the tuning fork is kept up electrically by the aid of the screw, , and the corresponding plate; of the style, , and of the fine wire spiral spring, , both insulated from the fork, from the electro-magnet, N, and from the two wires, F F', which communicate with a pile. v s f The interrupting system is symmetrical with the first. It consists of the style, , of the spiral spring, , of the screw, , and of the plate that this carries at its extremity. The terminal, B, which carries the spring, , and the rod which carries the screw being insulated from each other, it is only necessary to cause to terminate therein the extremities of a circuit comprising one pile, in order to produce in the circuit a number of interruptions equal to that of the tuning fork's vibrations. Provided the lengths of the springs, and , are proper, such vibrations will not be altered. s f v f f f' Moreover, the instrument is so arranged as to produce vibrations whose during the whole time the experiments last. This is done by modifying the of the vibrations; for the greater the amplitude, the longer likewise the duration of the contact of the style, , on the corresponding plate, and the shorter the duration of the interruption. In order to modify the amplitude, the action of the electro-magnet on the branches of the apparatus is made to vary. To effect this, the electro-magnet is made movable perpendicularly by the aid of a screw, V, between two slides, so that the core, N, may be moved with respect to the median line of the branches, and even be raised above them. Its action diminishes, necessarily, while it is being raised, and the amplitude of the vibrations likewise diminishes gradually and continuously. It may thus be made, without difficulty, to vary from two to three tenths of a millimeter to three or four millimeters or more. duration can be varied at pleasure and kept constant amplitude s But it is not sufficient to cause the amplitude to vary; it is necessary to measure it and to keep it constant at the value desired. The measurement is effected by the aid of a very simple apparatus that I have before described under the name of the . This is a small square of paper carrving a design like that shown in Fig. 5, and which is seen in Fig. 4 glued to one of the masses, M, which serve to vary the number of the instrument's vibrations. This figure is in fact, an angle, one of whose sides is graduated into millimeters, for example, and the other forms the edge of a wide black band. The apex of the angle is above and the divided side is perpendicular to the direction of the vibrations. vibrating micrometer Under such conditions, when the fork is vibrating, the apex of the angle, by virtue of the persistence of impressions upon the retina, to advance along the graduation in measure as the amplitude of the vibrations increases. If an angle has been drawn such that the slope of one of its sides to the other is one-tenth, it is easy to see that for each millimeter passed over by the apex of the angle, the amplitude will increase by two-tenths of a millimeter. seems apparently This is the way, then, that the amplitude is measured. On another hand, it suffices to keep the apex of the angle of the micrometer immovable, in order to be sure of the constancy of the tuning fork's amplitude; and this is done, when necessary, by causing the screw, V, to move slightly. The instrument represented in Fig. 4 is, moreover, fixed to a support devised by Mr. A. Duboscq, so as to make it possible to give the tuning fork every position possible with respect to a vertical plane; to raise it or lower it, and to move it backward or forward so that it may be employed for chimography, and in all those experiments in which electro-tuning folks are used. E. MERCADIER. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Various (2006). Scientific American Supplement, No. 365, December 30, 1882. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/18763/pg18763-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

APPARATUS FOR MEASURING ELECTRICITY AT THE UPPER SCHOOL OF TELEGRAPHY

ATOMS, MOLECULES, AND ETHER WAVES

How it Works by Archibald Williams is part of the HackerNoon Books Series. You can jump to any chapter in this book . THE MICROSCOPE, THE TELESCOPE, AND THE MAGIC-LANTERN. here Chapter XIII. THE MICROSCOPE, THE TELESCOPE, AND THE MAGIC-LANTERN. The simple microscope—Use of the simple microscope in the telescope—The terrestrial telescope—The Galilean telescope—The prismatic telescope—The reflecting telescope—The parabolic mirror—The compound microscope—The magic-lantern—The bioscope—The plane mirror. IN Fig. 119 is represented an eye looking at a vase, three inches high, situated at a, a foot away. If we were to place another vase, b, six inches high, at a distance of two feet; or c, nine inches high, at three feet; or d, a foot high, at four feet, the image on the retina would in every case be of the same size as that cast by a. We can therefore lay down the rule that . the apparent size of an object depends on the angle that it subtends at the eye To see a thing more plainly, we go nearer to it; and if it be very small, we hold it close to the eye. There is, however, a limit to the nearness to which it can be brought with advantage. The normal eye is unable to adapt its focus to an object less than about ten inches away, termed the "least distance of distinct vision." THE SIMPLE MICROSCOPE. A magnifying glass comes in useful when we want to examine an object very closely. The glass is a lens of short focus, held at a distance somewhat less than its principal focal length, f ( ), from the object. The rays from the head and tip of the pin which enter the eye are denoted by continuous lines. As they are deflected by the glass the eye gets the that a much longer pin is situated a considerable distance behind the real object in the plane in which the refracted rays would meet if produced backwards (shown by the dotted lines). The effect of the glass, practically, is to remove it (the object) to beyond the least distance of distinct vision, and at the same time to retain undiminished the angle it subtends at the eye, or, what amounts to the same thing, the actual size of the image formed on the retina. It follows, therefore, that if a lens be of such short focus that it allows us to see an object clearly at a distance of two inches—that is, one-fifth of the least distance of distinct vision—we shall get an image on the retina five times larger in diameter than would be possible without the lens. see Fig. 120 impression The two simple diagrams (Figs. 121 and 122) show why the image to be magnified should be nearer to the lens than the principal focus, f. We have already seen (Fig. 109) that rays coming from a point in the principal focal plane emerge as a parallel pencil. These the eye can bring to a focus, because it normally has a curvature for focussing parallel rays. But, owing to the power of "accommodation," it can also focus rays (Fig. 121), the eye lens thickening the necessary amount, and we therefore put our magnifying glass a bit nearer than f to get full advantage of proximity. If we had the object the principal focus, as in Fig. 122, the rays from it would converge, and these could not be gathered to a sharp point by the eye lens, as it cannot more than is required for focussing parallel rays. diverging outside flatten USE OF THE SIMPLE MICROSCOPE IN THE TELESCOPE. Let us now turn to Fig. 123. At a is a distant object, say, a hundred yards away. b is a double convex lens, which has a focal length of twenty inches. We may suppose that it is a lens in a camera. An inverted image of the object is cast by the lens at c. If the eye were placed at c, it would distinguish nothing. But if withdrawn to d, the least distance of distinct vision, behind c, the image is seen clearly. That the image really is at c is proved by letting down the focussing screen, which at once catches it. Now, as the focus of the lens is twice , the image will be twice as large as the object would appear if viewed directly without the lens. We may put this into a very simple formula:— d In Fig. 124 we have interposed between the eye and the object a small magnifying glass of 2½-inch focus, so that the eye can now clearly see the image when one-quarter away from it. b already magnifies the image twice; the eye-piece again magnifies it four times; so that the total magnification is 2 × 4 = 8 times. This result is arrived at quickly by dividing the focus of b (which corresponds to the object-glass of a telescope) by the focus of the eye-piece, thus:— d The ordinary astronomical telescope has a very long focus object-glass at one end of the tube, and a very short focus eye-piece at the other. To see an object clearly one merely has to push in or pull out the eye-piece until its focus exactly corresponds with that of the object-glass. THE TERRESTRIAL TELESCOPE. An astronomical telescope inverts images. This inversion is inconvenient for other purposes. So the terrestrial telescope (such as is commonly used by sailors) has an eye-piece compounded of four convex lenses which erect as well as magnify the image. Fig. 125 shows the simplest form of compound erecting eye-piece. THE GALILEAN TELESCOPE. A third form of telescope is that invented by the great Italian astronomer, Galileo, in 1609. Its principle is shown in Fig. 126. The rays transmitted by the object-glass are caught, coming to a focus, on a concave lens which separates them so that they appear to meet in the paths of convergence denoted by the dotted lines. The image is erect. Opera-glasses are constructed on the Galilean principle. before THE PRISMATIC TELESCOPE. In order to be able to use a long-focus object-glass without a long focussing-tube, a system of glass reflecting prisms is sometimes employed, as in Fig. 127. A ray passing through the object-glass is reflected from one posterior surface of prism a on to the other posterior surface, and by it out through the front on to a second prism arranged at right angles to it, which passes the ray on to the compound eye-piece. The distance between object-glass and eye-piece is thus practically trebled. The best-known prismatic telescopes are the Zeiss field-glasses. THE REFLECTING TELESCOPE. We must not omit reference to the telescope, so largely used by astronomers. The front end of the telescope is open, there being no object-glass. Rays from the object fall on a parabolic mirror situated in the rear end of the tube. This reflects them forwards to a focus. In the Newtonian reflector a plane mirror or prism is situated in the axis of the tube, at the focus, to reflect the rays through an eye-piece projecting through the side of the tube. Herschel's form of reflector has the mirror set at an angle to the axis, so that the rays are reflected direct into an eye-piece pointing through the side of the tube towards the mirror. reflecting THE PARABOLIC MIRROR. This mirror (Fig. 128) is of such a shape that all rays parallel to the axis are reflected to a common point. In the marine searchlight a powerful arc lamp is arranged with the arc at the focus of a parabolic reflector, which sends all reflected light forward in a pencil of parallel rays. The most powerful searchlight in existence gives a light equal to that of 350 million candles. THE COMPOUND MICROSCOPE. We have already observed (Fig. 110) that the nearer an object approaches a lens the further off behind it is the real image formed, until the object has reached the focal distance, when no image at all is cast, as it is an infinite distance behind the lens. We will assume that a certain lens has a focus of six inches. We place a lighted candle four feet in front of it, and find that a diminished image is cast on a ground-glass screen held seven inches behind it. If we now exchange the positions of the candle and the screen, we shall get an enlarged image of the candle. This is a simple demonstration of the law of —namely, that the distance between the lens and an object on one side and that between the lens and the corresponding image on the other bear a definite relation to each other; and an object placed at either focus will cast an image at the other. Whether the image is larger or smaller than the object depends on which focus it occupies. In the case of the object-glass of a telescope the image was at what we may call the focus. sharp conjugate foci short Now, a compound microscope is practically a telescope with the object at the focus, very close to a short-focus lens. A greatly enlarged image is thrown ( ) at the conjugate focus, and this is caught and still further magnified by the eye-piece. We may add that the object-glass, or , of a microscope is usually compounded of several lenses, as is also the eye-piece. long see Fig. 129 objective THE MAGIC-LANTERN. The most essential features of a magic-lantern are:—(1) The ; (2) the for concentrating the light rays on to the slide; (3) the for projecting a magnified image on to a screen. source of light condenser lens Fig. 130 shows these diagrammatically. The is most commonly an oil-lamp, or an acetylene gas jet, or a cylinder of lime heated to intense luminosity by an oxy-hydrogen flame. The natural combustion of hydrogen is attended by a great heat, and when the supply of oxygen is artificially increased the temperature of the flame rises enormously. The nozzle of an oxy-hydrogen jet has an interior pipe connected with the cylinder holding one gas, and an exterior, and somewhat larger, pipe leading from that containing the other, the two being arranged concentrically at the nozzle. By means of valves the proportions of the gases can be regulated to give the best results. illuminant The is set somewhat further from the illuminant than the principal focal length of the lenses, so that the rays falling on them are bent inwards, or to the slide. condenser The , or object lens, stands in front of the slide. Its position is adjustable by means of a rack and a draw-tube. The nearer it is brought to the slide the further away is the conjugate focus ( ), and consequently the image. The exhibitor first sets up his screen and lantern, and then finds the conjugate foci of slide and image by racking the lens in or out. objective see p. 239 If a very short focus objective be used, subjects of microscopic proportions can be projected on the screen enormously magnified. During the siege of Paris in 1870–71 the Parisians established a balloon and pigeon post to carry letters which had been copied in a minute size by photography. These copies could be enclosed in a quill and attached to a pigeon's wing. On receipt, the copies were placed in a special lantern and thrown as large writing on the screen. Micro-photography has since then made great strides, and is now widely used for scientific purposes, one of the most important being the study of the crystalline formations of metals under different conditions. THE BIOSCOPE. "Living pictures" are the most recent improvement in magic-lantern entertainments. The negatives from which the lantern films are printed are made by passing a ribbon of sensitized celluloid through a special form of camera, which feeds the ribbon past the lens in a series of jerks, an exposure being made automatically by a revolving shutter during each rest. The positive film is placed in a lantern, and the intermittent movement is repeated; but now the source of illumination is behind the film, and light passes outwards through the shutter to the screen. In the Urban bioscope the film travels at the rate of fifteen miles an hour, upwards of one hundred exposures being made every second. The impression of continuous movement arises from the fact that the eye cannot get rid of a visual impression in less than one-tenth of a second. So that if a series of impressions follow one another more rapidly than the eye can rid itself of them the impressions will overlap, and give one of , if the position of some of the objects, or parts of the objects, varies slightly in each succeeding picture. motion THE PLANE MIRROR. This chapter may conclude with a glance at the common looking-glass. Why do we see a reflection in it? The answer is given graphically by Fig. 131. Two rays, a , a , from a point a strike the mirror m at the points and . Lines n, o, drawn from these points perpendicular to the mirror are called their . The angles a n, a o are the of rays a , a . The paths which the rays take after reflection must make angles with n and o respectively equal to a n, a o. These are the . If the eye is so situated that the rays enter it as in our illustration, an image of the point a is seen at the point a1, in which the lines d , e meet when produced backwards. b c b c b c normals b c angles of incidence b c b c b c angles of reflection b c When the vertical mirror is replaced by a horizontal reflecting surface, such as a pond (Fig. 132), the same thing happens. The point at which the ray from the reflection of the spire's tip to the eye appears to pass through the surface of the water must be so situated that if a line were drawn perpendicular to it from the surface the angles made by lines drawn from the real spire tip and from the observer's eye to the base of the perpendicular would be equal. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Archibald Williams (2009). How it Works. Urbana, Illinois: Project Gutenberg. Retrieved https://www.gutenberg.org/cache/epub/28553/pg28553-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

THE MICROSCOPE, THE TELESCOPE, AND THE MAGIC-LANTERN.

Lasers by Hal Hellman, is part of the HackerNoon Books Series. You can jump to any chapter in this book . THE ELECTROMAGNETIC SPECTRUM here THE ELECTROMAGNETIC SPECTRUM Some 85% of what man learns comes to him through his vision in response to the medium of light. Yet, ironically, it wasn’t until the end of the 17th century that he first began to get an inkling of what light really is. It took the great scientific genius Isaac Newton to show that so-called white light is really a combination of all the colors of the rainbow. A few years later the Dutch astronomer Christiaan Huygens introduced the idea that light is a wave motion, a concept finally validated in 1803 when the British physician Thomas Young ingeniously demonstrated interference effects in waves. Thus it was finally realized that the only difference between the various colors of light was one of wavelength. For light was indeed found to be a wave phenomenon, no different in principle from the water waves you have seen a thousand times. If you stand at the seashore, you can easily count the number of waves that approach the shore in a minute. Divide that number by 60 and you have the frequency of the wave motion in the familiar unit, cycles-per-second (cps). You would have to count pretty quickly to do this for light, however. Light waves vibrate or oscillate at the rate of some 400 million million times a second. That’s the vibration rate of waves of red light; violet results from vibrations that are just about twice that fast. With frequencies of this magnitude, discussion and handling of data and dimensions are cumbersome and rather awkward. Fortunately there is another approach. Let’s look again at our ocean waves. We see that there is a regularity about them (before they begin to break on the shore). The distance from one crest to the next is significant and is called the . Water waves are measured in feet, and in comparable units light waves are recorded in ten-millionths of an inch—again a very cumbersome number. Scientists therefore use the metric system and have standardized a unit called the angstrom, which is equal to the one-hundred-millionth part of a centimeter (10⁻⁸ cm). Thus we find, as shown in , that the visible light range runs from the violet at about 4000 angstroms to red at about 7000 angstroms. wavelength Figure 3 Figure 3 The visible light spectrum ranges between approximately 4000 and 7000 angstroms. At roughly the same time that the wavelength of light was being determined, the German-British astronomer William Herschel performed an interesting experiment. He held a thermometer in turn in the various colors of light that had been spread out by an optical prism. As he moved the thermometer from the violet to the red, the temperature reading rose—and it continued to rise as he moved the instrument the red area, where no prismatic light could be seen. beyond Thus Herschel discovered infrared rays (the kind of heat we get from the sun) adjoining the visible red light, and at the same time found that they were merely a continuation of the visible spectrum. Shortly thereafter, ultraviolet rays were found on the other end of the visible light band. One of the most fascinating movements in science has been the constant expansion since then of both ends of the radiating-wave spectrum. The result has come to be called the , which, as we see in , encompasses a wide variety of apparently different kinds of radiation. Above the visible band (the higher frequencies), we find ultraviolet light, X rays, gamma rays, and some cosmic rays; below it are infrared radiation, microwaves, and radio waves. Only a small proportion of the total spectrum is occupied by the visible band. Another point of interest is the inverse relationship between wavelength and frequency. As one goes up the other goes down. electromagnetic spectrum Figure 4 Figure 4 Visible light region spans a tiny portion of the total electromagnetic spectrum. These many kinds of rays and waves vary tremendously in the ways they interact with matter. But they are all part of a single family. The only difference among them, as with the colors of the rainbow, lies in their wavelengths. In a few cases, as we shall see later, the mode of generation is also different. The band of radiation stretching from the infrared to cosmic rays has been, up to now, largely the concern of physical scientists. Because of their high frequencies, these radiations are generally handled, when calculations or measurements must be made, in terms of wavelength. Radio and microwaves, on the other hand, have been more in the domain of communications engineers and are more likely to be discussed in terms of frequency. Thus it is that your radio is marked off in kilocycles, or thousands of cycles per second, while light is described as radiation in the 4000 to 7000 angstrom band. The relative newness of the various radiations has kept scientists busy learning about them and, as information and experience have accumulated, putting them to work. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Hal Hellman (2021). Laser. Urbana, Illinois: Project Gutenberg. Retrieved October 2022 https://www.gutenberg.org/cache/epub/65512/pg65512-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

THE ELECTROMAGNETIC SPECTRUM

Abandoned by Jules Verne, is part of the HackerNoon Books Series. You can jump to any chapter in this book . CHAPTER XIX here CHAPTER XIX Recollections of their Native Land—Probable Future—Project for surveying the Coasts of the Island—Departure on the 16th of April—Sea-view of Reptile End—The basaltic Rocks of the Western Coast—Bad Weather—Night comes on—New Incident. Two years already! and for two years the colonists had had no communication with their fellow-creatures! They were without news from the civilised world, lost on this island, as completely as if they had been on the most minute star of the celestial hemisphere! What was now happening in their country? The picture of their native land was always before their eyes, the land torn by civil war at the time they left it, and which the Southern rebellion was perhaps still staining with blood! It was a great sorrow to them, and they often talked together of these things, without ever doubting however that the cause of the North must triumph, for the honour of the American Confederation. During these two years not a vessel had passed in sight of the island; or, at least, not a sail had been seen. It was evident that Lincoln Island was out of the usual track, and also that it was unknown,—as was besides proved by the maps,—for though there was no port, vessels might have visited it for the purpose of renewing their store of water. But the surrounding ocean was deserted as far as the eye could reach, and the colonists must rely on themselves for regaining their native land. However, one chance of rescue existed, and this chance was discussed one day in the first week of April, when the colonists were gathered together in the dining-room of Granite House. They had been talking of America, of their native country, which they had so little hope of ever seeing again. "Decidedly we have only one way," said Spilett, "one single way for leaving Lincoln Island, and that is, to build a vessel large enough to sail several hundred miles. It appears to me, that when one has built a boat it is just as easy to build a ship!" "And in which we might go to the Pomatous," added Herbert, "just as easily as we went to Tabor Island." "I do not say no," replied Pencroft, who had always the casting vote in maritime questions; "I do not say no, although it is not exactly the same thing to make a long as a short voyage! If our little craft had been caught in any heavy gale of wind during the voyage to Tabor Island, we should have known that land was at no great distance either way; but twelve hundred miles is a pretty long way, and the nearest land is at least that distance!" "Would you not, in that case, Pencroft, attempt the adventure?" asked the reporter. "I will attempt anything that is desired, Mr. Spilett," answered the sailor, "and you know well that I am not a man to flinch!" "Remember, besides, that we number another sailor amongst us now," remarked Neb. "Who is that?" asked Pencroft. "Ayrton." "That is true," replied Herbert. "If he will consent to come," said Pencroft. "Nonsense!" returned the reporter; "do you think that if Lord Glenarvan's yacht had appeared at Tabor Island, whilst he was still living there, Ayrton would have refused to depart?" "You forget, my friends," then said Cyrus Harding, "that Ayrton was not in possession of his reason during the last years of his stay there. But that is not the question. The point is to know if we may count among our chances of being rescued, the return of the Scotch vessel. Now, Lord Glenarvan promised Ayrton that he would return to take him off Tabor Island when he considered that his crimes were expiated, and I believe that he will return." "Yes," said the reporter, "and I will add that he will return soon, for it is twelve years since Ayrton was abandoned!" "Well!" answered Pencroft, "I agree with you that the nobleman will return, and soon too. But where will he touch? At Tabor Island, and not at Lincoln Island." "That is the more certain," replied Herbert, "as Lincoln Island is not even marked on the map." "Therefore, my friends," said the engineer, "we ought to take the necessary precautions for making our presence, and that of Ayrton on Lincoln Island known at Tabor Island." "Certainly," answered the reporter, "and nothing is easier than to place in the hut, which was Captain Grant's and Ayrton's dwelling, a notice which Lord Glenarvan and his crew cannot help finding, giving the position of our island." "It is a pity," remarked the sailor, "that we forgot to take that precaution on our first visit to Tabor Island." "And why should we have done it?" asked Herbert. "At that time we did not know Ayrton's history; we did not know that any one was likely to come some day to fetch him; and when we did know his history, the season was too advanced to allow us to return then to Tabor Island." "Yes," replied Harding, "it was too late, and we must put off the voyage until next spring." "But suppose the Scotch yacht comes before that," said Pencroft. "That is not probable," replied the engineer, "for Lord Glenarvan would not choose the winter season to venture into these seas. Either he has already returned to Tabor Island, since Ayrton has been with us, that is to say, during the last five months and has left again; or he will not come till later, and it will be time enough in the first fine October days to go to Tabor Island, and leave a notice there." "We must allow," said Neb, "that it will be very unfortunate if the has returned to these parts only a few months ago!" Duncan "I hope that it is not so," replied Cyrus Harding, "and that Heaven has not deprived us of the best chance which remains to us." "I think," observed the reporter, "that at any rate we shall know what we have to depend on when we have been to Tabor Island, for if the yacht has returned there, they will necessarily have left some traces of their visit." "That is evident," answered the engineer. "So then, my friends, since we have this chance of returning to our country, we must wait patiently, and if it is taken from us we shall see what will be best to do." "At any rate," remarked Pencroft, "it is well understood that if we do leave Lincoln Island in some way or another, it will not be because we were uncomfortable there!" "No, Pencroft," replied the engineer, "it will be because we are far from all that a man holds dearest in this world, his family, his friends, his native land!" Matters being thus decided, the building of a vessel large enough to sail either to the Archipelagos in the north, or to New Zealand in the west, was no longer talked of, and they busied themselves in their accustomed occupations, with a view to wintering a third time in Granite House. However, it was agreed that before the stormy weather came on, their little vessel should be employed in making a voyage round the island. A complete survey of the coast had not yet been made, and the colonists had but an imperfect idea of the shore to the west and north, from the mouth of Falls River to the Mandible Capes, as well as of the narrow bay between them, which opened like a shark's jaws. The plan of this excursion was proposed by Pencroft, and Cyrus Harding fully acquiesced in it, for he himself wished to see this part of his domain. The weather was variable, but the barometer did not fluctuate by sudden movements, and they could therefore count on tolerable weather. However, during the first week of April, after a sudden barometrical fall, a renewed rise was marked by a heavy gale of wind, lasting five or six days; then the needle of the instrument remained stationary at a height of twenty-nine inches and nine-tenths, and the weather appeared propitious for an excursion. The departure was fixed for the 16th of April, and the , anchored in Port Balloon, was provisioned for a voyage which might be of some duration. Bonadventure Cyrus Harding informed Ayrton of the projected expedition, and proposed that he should take part in it; but Ayrton preferring to remain on shore, it was decided that he should come to Granite House during the absence of his companions. Master Jup was ordered to keep him company, and made no remonstrance. On the morning of the 16th of April all the colonists, including Top, embarked. A fine breeze blew from the south-west, and the tacked on leaving Port Balloon so as to reach Reptile End. Of the ninety miles which the perimeter of the island measured, twenty included the south coast between the port and the promontory. The wind being right ahead, it was necessary to hug the shore. Bonadventure It took the whole day to reach the promontory, for the vessel on leaving port had only two hours of the ebb tide, and had therefore to make way for six hours against the flood. It was nightfall before the promontory was doubled. The sailor then proposed to the engineer that they should continue sailing slowly with two reefs in the sail. But Harding preferred to anchor a few cable-lengths from the shore, so as to survey that part of the coast during the day. It was agreed also that as they were anxious for a minute exploration of the coast they should not sail during the night, but would always, when the weather permitted it, be at anchor near the shore. The night was passed under the promontory, and the wind having fallen, nothing disturbed the silence. The passengers, with the exception of the sailor, scarcely slept as well on board the as they would have done in their rooms at Granite House, but they did sleep however. Pencroft set sail at break of day, and by going on the larboard tack they could keep close to the shore. Bonadventure The colonists knew this beautiful wooded coast, since they had already explored it on foot, and yet it again excited their admiration. They coasted along as close in as possible, so as to notice everything, avoiding always the trunks of trees which floated here and there. Several times also they anchored, and Gideon Spilett took photographs of the superb scenery. About noon the arrived at the mouth of Falls River. Beyond, on the left bank, a few scattered trees appeared, and three miles further even these dwindled into solitary groups among the western spurs of the mountain, whose arid ridge sloped down to the shore. Bonadventure What a contrast between the northern and southern part of the coast! In proportion as one was woody and fertile so was the other rugged and barren! It might have been designated as one of those iron coasts, as they are called in some countries, and its wild confusion appeared to indicate that a sudden crystallisation had been produced in the yet liquid basalt of some distant geological sea. These stupendous masses would have terrified the settlers if they had been cast at first on this part of the island! They had not been able to perceive the sinister aspect of this shore from the summit of Mount Franklin, for they overlooked it from too great a height, but viewed from the sea it presented a wild appearance which could not perhaps be equalled in any corner of the globe. The sailed along this coast for the distance of half a mile. It was easy to see that it was composed of blocks of all sizes, from twenty to three hundred feet in height, and of all shapes, round like towers, prismatic like steeples, pyramidal like obelisks, conical like factory chimneys. An iceberg of the Polar seas could not have been more capricious in its terrible sublimity! Here, bridges were thrown from one rock to another; there, arches like those of a wave, into the depths of which the eye could not penetrate; in one place, large vaulted excavations presented a monumental aspect; in another, a crowd of columns, spires, and arches, such as no Gothic cathedral ever possessed. Every caprice of nature, still more varied than those of the imagination, appeared on this grand coast, which extended over a length of eight or nine miles. Bonadventure Cyrus Harding and his companions gazed, with a feeling of surprise bordering on stupefaction. But, although they remained silent, Top, not being troubled with feelings of this sort, uttered barks which were repeated by the thousand echoes of the basaltic cliff. The engineer even observed that these barks had something strange in them, like those which the dog had uttered at the mouth of the well in Granite House. "Let us go close in," said he. And the sailed as near as possible to the rocky shore. Perhaps some cave, which it would be advisable to explore, existed there? But Harding saw nothing, not a cavern, not a cleft which could serve as a retreat to any being whatever, for the foot of the cliff was washed by the surf. Soon Top's barks ceased, and the vessel continued her course at a few cable-lengths from the coast. Bonadventure In the north-west part of the island the shore became again flat and sandy. A few trees here and there rose above a low, marshy ground, which the colonists had already surveyed; and in violent contrast to the other desert shore, life was again manifested by the presence of myriads of water-fowl. That evening the anchored in a small bay to the north of the island, near the land, such was the depth of water there. The night passed quietly, for the breeze died away with the last light of day, and only rose again with the first streaks of dawn. Bonadventure As it was easy to land, the usual hunters of the colony, that is to say, Herbert and Gideon Spilett, went for a ramble of two hours or so, and returned with several strings of wild duck and snipe. Top had done wonders, and not a bird had been lost, thanks to his zeal and cleverness. At eight o'clock in the morning the set sail, and ran rapidly towards North Mandible Cape, for the wind was right astern and freshening rapidly. Bonadventure "However," observed Pencroft, "I should not be surprised if a gale came up from the west. Yesterday the sun set in a very red-looking horizon, and now, this morning, those mares-tails don't forebode anything good." These mares-tails are cirrus clouds, scattered in the zenith, their height from the sea being less than five thousand feet. They look like light pieces of cotton wool, and their presence usually announces some sudden change in the weather. "Well," said Harding, "let us carry as much sail as possible, and run for shelter into Shark Gulf. I think that the will be safe there." Bonadventure "Perfectly," replied Pencroft, "and besides, the north coast is merely sand, very uninteresting to look at." "I shall not be sorry," resumed the engineer, "to pass not only to-night but to-morrow in that bay, which is worth being carefully explored." "I think that we shall be obliged to do so, whether we like it or not," answered Pencroft, "for the sky looks very threatening towards the west. Dirty weather is coming on!" "At any rate we have a favourable wind for reaching Cape Mandible," observed the reporter. "A very fine wind," replied the sailor; "but we must tack to enter the gulf, and I should like to see my way clear in these unknown quarters." "Quarters which appear to be filled with rocks," added Herbert, "if we judge by what we saw on the south coast of Shark Gulf." "Pencroft," said Cyrus Harding, "do as you think best, we will leave it to you." "Don't make your mind uneasy, captain," replied the sailor, "I shall not expose myself needlessly! I would rather a knife were run into my ribs than a sharp rock into those of my !" Bonadventure That which Pencroft called ribs was the part of his vessel under water, and he valued it more than his own skin. "What o'clock is it?" asked Pencroft. "Ten o'clock," replied Gideon Spilett. "And what distance is it to the Cape, captain?" "About fifteen miles," replied the engineer. "That's a matter of two hours and a half," said the sailor, "and we shall be off the Cape between twelve and one o'clock. Unluckily, the tide will be turning at that moment, and will be ebbing out of the gulf. I am afraid that it will be very difficult to get in, having both wind and tide against us." "And the more so that it is a full moon to-day," remarked Herbert, "and these April tides are very strong." "Well, Pencroft," asked Cyrus Harding, "can you not anchor off the Cape?" "Anchor near land, with bad weather coming on!" exclaimed the sailor. "What are you thinking of, captain? We should run aground to a certainty!" "What will you do then?" "I shall try to keep in the offing until the flood, that is to say, till about seven in the evening, and if there is still light enough I will try to enter the gulf; if not, we must stand off and on during the night, and we will enter to-morrow at sunrise." "As I told you, Pencroft, we will leave it to you," answered Harding. "Ah!" said Pencroft, "if there was only a light-house on the coast, it would be much more convenient for sailors." "Yes," replied Herbert, "and this time we shall have no obliging engineer to light a fire to guide us into port!" "Why, indeed, my dear Cyrus," said Spilett, "we have never thanked you for it, but frankly, without that fire we should never have been able to reach—" "A fire?" asked Harding, much astonished at the reporter's words. "We mean, captain," answered Pencroft, "that on board the we were very anxious during the few hours before our return, and we should have passed to windward of the island, if it had not been for the precaution you took of lighting a fire in the night of the 19th of October, on Prospect Heights." Bonadventure "Yes, yes! That was a lucky idea of mine!" replied the engineer. "And this time," continued the sailor, "unless the idea occurs to Ayrton, there will be no one to do us that little service!" "No! no one!" answered Cyrus Harding. A few minutes after, finding himself alone in the bows of the vessel with the reporter, the engineer bent down and whispered,— "If there is one thing certain in this world, Spilett, it is that I never lighted any fire during the night of the 19th of October, neither on Prospect Heights nor on any other part of the island!" About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Jules Verne (2010). Abandoned. Urbana, Illinois: Project Gutenberg. Retrieved October 2022 https://www.gutenberg.org/cache/epub/33516/pg33516-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at , located at . www.gutenberg.org https://www.gutenberg.org/policy/license.html

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