How an RM Nimbus Taught Me a Hacker Mentality

What can I make it do?

It’s been said that when faced with a new piece of technology, a normal person asks “what does it do?”, but a hacker asks “what can I make it do?”.

This kind of curiosity is integral to a hacker mindset.

A 'glider', a highly-recognisable self-replicating pattern from Conway's Game of Life, sometimes used in hacker symbolism.
An RM Nimbus was not the first computer on which I played Game of Life1. But this glider is here symbolically, anyway.

I can trace my hacker roots back further than my first experience of using an RM Nimbus M-Series in circa 19922. But there was something particular about my experience of this popular piece of British edutech kit which provided me with a seminal experience that shaped my “hacker identity”. And it’s that experience about which I’d like to tell you:

Shortly after I started secondary school, they managed to upgrade their computer lab from a handful of Nimbus PC-186s to a fancy new network of M-Series PC-386s. The school were clearly very proud of this cutting-edge new acquisition, and we watched the teachers lay out the manuals and worksheets which smelled fresh and new and didn’t yet have their corners frayed nor their covers daubed in graffiti.

An RM Nimbus PC-186 at its launch menu; a DOS-based function key list menu to run a variety of different programs, alongside RM manuals.
I only got to use the schools’ older computers – this kind! – once or twice before the new ones were delivered.

Program Manager

The new ones ran Windows 3 (how fancy!). Well… kind-of. They’d been patched with a carefully-modified copy of Program Manager that imposed a variety of limitations. For example, they had removed the File > Run… menu item, along with an icon for File Manager, in order to restrict access to only the applications approved by the network administrator.

A special program was made available to copy files between floppy disks and the user’s network home directory. This allowed a student to take their work home with them if they wanted. The copying application – whose interface was vastly inferior to File Manager‘s – was limited to only copying files with extensions in its allowlist. This meant that (given that no tool was available that could rename files) the network was protected from anybody introducing any illicit file types.

Bring a .doc on a floppy? You can copy it to your home directory. Bring a .exe? You can’t even see it.

To young-teen-Dan, this felt like a challenge. What I had in front of me was a general-purpose computer with a limited selection of software but a floppy drive through which media could be introduced. What could I make it do?

This isn’t my school’s computer lab circa mid-1990s (it’s this school) but it has absolutely the same energy. Except that I think Solitaire was one of the applications that had been carefully removed from Program Manager.

Spoiler: eventually I ended up being able to execute pretty much anything I wanted, but we’ll get to that. The journey is the important part of the story. I didn’t start by asking “can I trick this locked-down computer lab into letting my friends and I play Doom deathmatches on it?” I started by asking “what can I make it do?”; everything else built up over time.

I started by playing with macros. Windows used to come with a tool called Recorder,3 which you could use to “record” your mouse clicks and keypresses and play them back.

Recorder + Paintbrush made for an interesting way to use these basic and limited tools to produce animations. Like this one, except at school I’d have put more effort in4.

Microsoft Word

Then I noticed that Microsoft Word also had a macro recorder, but this one was scriptable using a programming language called WordBasic (a predecessor to Visual Basic for Applications). So I pulled up the help and started exploring what it could do.

And as soon as I discovered the Shell function, I realised that the limitations that were being enforced on the network could be completely sidestepped.

Screenshot showing Microsoft Word's 'Macro Editor' on Windows 3.1. The subroutine being defined contains the code 'Shell("WINFILE.EXE")'; the 'Shell' command is described in the WordBasic Help file, which is also visible.
A Windows 3 computer that runs Word… can run any other executable it has access to. Thanks, macro editor.

Now that I could run any program I liked, I started poking the edges of what was possible.

  • Could I get a MS-DOS prompt/command shell? Yes, absolutely5.
  • Could I write to the hard disk drive? Yes, but any changes got wiped when the computer performed its network boot.
  • Could I store arbitrary files in my personal network storage? Yes, anything I could bring in on floppy disks6 could be persisted on the network server.

I didn’t have a proper LAN at home7 So I really enjoyed the opportunity to explore, unfettered, what I could get up to with Windows’ network stack.

Screenshot from Windows 3.11; a Microsoft Paint window is partially-concealed behind a WinChat conversation with 'RMNET013'. The other participant is warning the user to look busy and stop drawing dicks in Paint because the teacher is coming. The user is responding with confusion.
The “WinNuke” NetBIOS remote-crash vulnerability was a briefly-entertaining way to troll classmates, but unlocking WinPopup/Windows Chat capability was ultimately more-rewarding.

File Manager

I started to explore the resources on the network. Each pupil had their own networked storage space, but couldn’t access one another’s. But among the directories shared between all students, I found a directory to which I had read-write access.

I created myself a subdirectory and set the hidden bit on it, and started dumping into it things that I wanted to keep on the network8.

By now my classmates were interested in what I was achieving, and I wanted in the benefits of my success. So I went back to Word and made a document template that looked superficially like a piece of coursework, but which contained macro code that would connect to the shared network drive and allow the user to select from a series of programs that they’d like to run.

Gradually, compressed over a series of floppy disks, I brought in a handful of games: Commander Keen, Prince of Persia, Wing Commander, Civilization, Wolfenstein 3D, even Dune II. I got increasingly proficient at modding games to strip out unnecessary content, e.g. the sound and music files9, minimising the number of floppy disks I needed to ZIP (or ARJ!) content to before smuggling it in via my shirt pocket, always sure not to be carrying so many floppies that it’d look suspicious.

Screenshot of Windows 3.11 File Manager connected to a network with shares rmnet, shared, and students. Shared contains a hidden directory called 'dan'.
The goldmine moment – for my friends, at least – was the point at which I found a way to persistently store files in a secret shared location, allowing me to help them run whatever they liked without passing floppy disks around the classroom (which had been my previous approach).

In a particularly bold move, I implemented a simulated login screen which wrote the entered credentials into the shared space before crashing the computer. I left it running, unattended, on computers that I thought most-likely to be used by school staff, and eventually bagged myself the network administrator’s password. I only used it twice: the first time, to validate my hypothesis about the access levels it granted; the second, right before I finished school, to confirm my suspicion that it wouldn’t have been changed during my entire time there10.

Are you sure you want to quit?

My single biggest mistake was sharing my new-found power with my classmates. When I made that Word template that let others run the software I’d introduced to the network, the game changed.

When it was just me, asking the question what can I make it do?, everything was fun and exciting.

But now half a dozen other teens were nagging me and asking “can you make it do X?”

This wasn’t exploration. This wasn’t innovation. This wasn’t using my curiosity to push at the edges of a system and its restrictions! I didn’t want to find the exploitable boundaries of computer systems so I could help make it easier for other people to do so… no: I wanted the challenge of finding more (and weirder) exploits!

I wanted out. But I didn’t want to say to my friends that I didn’t want to do something “for” them any more11.

I figured: I needed to get “caught”.

16-bit Windows screenshot with a background image from WarGames. A dialog box asks 'Are you sure you want to quit? If you quit, you will lose the ability to: (a) use network chat tools, (b) play videogames awhen you should be doing coursework, (c) impress your friends and raise your otherwise-pathetic social status'; the cursor hovers over a 'Yes, I'm out' button.
I considered just using graphics software to make these screenshots… but it turned out to be faster to spin up a network of virtual machines running Windows 3.11 and some basic tools. I actually made the stupid imaginary dialog box you’re seeing.12

I chose… to get sloppy.

I took a copy of some of the software that I’d put onto the shared network drive and put it in my own home directory, this time un-hidden. Clearly our teacher was already suspicious and investigating, because within a few days, this was all that was needed for me to get caught and disciplined13.

I was disappointed not to be asked how I did it, because I was sufficiently proud of my approach that I’d hoped to be able to brag about it to somebody who’d understand… but I guess our teacher just wanted to brush it under the carpet and move on.

Aftermath

The school’s IT admin certainly never worked-out the true scope of my work. My “hidden” files remained undiscovered, and my friends were able to continue to use my special Word template to play games that I’d introduced to the network14. I checked, and the hidden files were still there when I graduated.

The warning worked: I kept my nose clean in computing classes for the remainder of secondary school. But I would’ve been happy to, anyway: I already felt like I’d “solved” the challenge of turning the school computer network to my interests and by now I’d moved on to other things… learning how to reverse-engineer phone networks… and credit card processors… and copy-protection systems. Oh, the stories I could tell15.

Old photograph of Dan, then a teenager, with other teenagers. Dan is labelled 'young hacker, a.k.a. bellend', while another young man is captioned 'classmate who just wanted to play lemmings'.
I “get” it that some of my classmates – including some of those pictured – were mostly interested in the results of my hacking efforts. But for me it always was – and still is – about the journey of discovery.

But I’ll tell you what: 13-ish year-old me ought to be grateful to the RM Nimbus network at my school for providing an interesting system about which my developing “hacker brain” could ask: what can I make it do?

Which remains one of the most useful questions with which to foster a hacker mentality.

Footnotes

1 I first played Game of Life on an Amstrad CPC464, or possibly a PC1512.

2 What is the earliest experience to which I can credit my “hacker mindset”? Tron and WarGames might have played a part, as might have the “hacking” sequence in Ferris Bueller’s Day Off. And there was the videogame Hacker and its sequel (it’s funny to see their influence in modern games). Teaching myself to program so that I could make text-based adventures was another. Dissecting countless obfuscated systems to see how they worked… that’s yet another one: something I did perhaps initially to cheat at games by poking their memory addresses or hexediting their save games… before I moved onto reverse-engineering copy protection systems and working out how they could be circumvented… and then later still when I began building hardware that made it possible for me to run interesting experiments on telephone networks.

Any of all of these datapoints, which took place over a decade, could be interpreted as “the moment” that I became a hacker! But they’re not the ones I’m talking about today. Today… is the story of the RM Nimbus.

3 Whatever happened to Recorder? After it disappeared in Windows 95 I occasionally had occasion to think to myself “hey, this would be easier if I could just have the computer watch me and copy what I do a few times.” But it was not to be: Microsoft decided that this level of easy automation wasn’t for everyday folks. Strangely, it wasn’t long after Microsoft dropped macro recording as a standard OS feature that Apple decided that MacOS did need a feature like this. Clearly it’s still got value as a concept!

4 Just to clarify: I put more effort in to making animations, which were not part of my schoolwork back when I was a kid. I certainly didn’t put more effort into my education.

5 The computers had been configured to make DOS access challenging: a boot menu let you select between DOS and Windows, but both were effectively nerfed. Booting into DOS loaded an RM-provided menu that couldn’t be killed; the MS-DOS prompt icon was absent from Program Manager and quitting Windows triggered an immediate shutdown.

6 My secondary school didn’t get Internet access during the time I was enrolled there. I was recently trying to explain to one of my kids the difference between “being on a network” and “having Internet access”, and how often I found myself on a network that wasn’t internetworked, back in the day. I fear they didn’t get it.

7 I was in the habit of occasionally hooking up PCs together with null modem cables, but only much later on would I end up acquiring sufficient “thinnet” 10BASE2 kit that I could throw together a network for a LAN party.

8 Initially I was looking to sidestep the space limitation enforcement on my “home” directory, and also to put the illicit software I was bringing in somewhere that could not be trivially-easily traced back to me! But later on this “shared” directory became the repository from which I’d distribute software to my friends, too.

9 The school computer didn’t have soundcards and nobody would have wanted PC speakers beeping away in the classroom while they were trying to play a clandestine videogame anyway.

10 The admin password was concepts. For at least four years.

11 Please remember that at this point I was a young teenager and so was pretty well over-fixated on what my peers thought of me! A big part of the persona I presented was of somebody who didn’t care what others thought of him, I’m sure, but a mask that doesn’t look like a mask… is still a mask. But yeah: I had a shortage of self-confidence and didn’t feel able to say no.

12 Art is weird when your medium is software.

13 I was briefly alarmed when there was talk of banning me from the computer lab for the remainder of my time at secondary school, which scared me because I was by now half-way through my boring childhood “life plan” to become a computer programmer by what seemed to be the appropriate route, and I feared that not being able to do a GCSE in a CS-adjacent subject could jeopardise that (it wouldn’t have).

14 That is, at least, my friends who were brave enough to carry on doing so after the teacher publicly (but inaccurately) described my alleged offences, seemingly as a warning to others.

15 Oh, the stories I probably shouldn’t tell! But here’s a teaser: when I built my first “beige box” (analogue phone tap hardware) I experimented with tapping into the phone line at my dad’s house from the outside. I carefully shaved off some of the outer insulation of the phone line that snaked down the wall from the telegraph pole and into the house through the wall to expose the wires inside, identified each, and then croc-clipped my box onto it and was delighted to discovered that I could make and receive calls “for” the house. And then, just out of curiosity to see what kinds of protections were in place to prevent short-circuiting, I experimented with introducing one to the ringer line… and took out all the phones on the street. Presumably I threw a circuit breaker in the roadside utility cabinet. Anyway, I patched-up my damage and – fearing that my dad would be furious on his return at the non-functioning telecomms – walked to the nearest functioning payphone to call the operator and claim that the phone had stopped working and I had no idea why. It was fixed within three hours. Phew!

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BingO Bakery

This is a repost promoting content originally published elsewhere. See more things Dan's reposted.

Don’t understand why Web accessibility is important? Need a quick and easily-digestible guide to the top things you should be looking into in order to make your web applications screenreader ready? Try this fun, video-game-themed 5 minute video from Microsoft.

There’s a lot more to accessibility than is covered here, and it’s perhaps a little over-focussed on screenreaders, but it’s still a pretty awesome introduction.

Risking a Homogeneous Web

This is a repost promoting content originally published elsewhere. See more things Dan's reposted.

I don’t think Microsoft using Chromium is the end of the world, but it is another step down a slippery slope. It’s one more way of bolstering the influence Google currently has on the web.

We need Google to keep pushing the web forward. But it’s critical that we have other voices, with different viewpoints, to maintain some sense of balance. Monocultures don’t benefit anyone.

This essay follows-up nicely on my concerns about Microsoft’s move from EdgeHTML to Chromium in Edge, but goes further to discuss some of the bigger problems of a homogeneous web, especially one under Google’s influence.

Edge may be becoming Chromium-powered, and that’s terrible

Microsoft engineers have been spotted committing code to Chromium, the backend of Google Chrome and many other web browsers. This, among other things, has lead to speculation that Microsoft’s browser, Edge, might be planned to switch from its current rendering engine (EdgeHTML) to Blink (Chromium’s). This is bad news.

This page in Microsoft Edge
This post, as it would appear if you were looking at it in Edge. Which you might be, I suppose.

The younger generation of web developers are likely to hail this as good news: one fewer engine to develop for and test in, they’re all already using Chrome or something similar (and certainly not Edge) for development and debugging anyway, etc. The problem comes perhaps because they’re too young to remember the First Browser War and its aftermath. Let me summarise:

  1. Once upon a time – let’s call it the mid-1990s – there were several web browsers: Netscape Navigator, Internet Explorer, Opera, etc. They all used different rendering engines and so development was sometimes a bit of a pain, but only if you wanted to use the latest most cutting-edge features: if you were happy with the standard, established features of the Web then your site would work anywhere, as has always been the case.
    Best viewed with... any damn browser
  2. Then, everybody starting using just one browser: following some shady dealings and monopoly abuse, 90%+ of Web users started using just one web browser, Internet Explorer. By the time anybody took notice, their rivals had been economically crippled beyond any reasonable chance of recovery, but the worst had yet to come…
    Best viewed with Internet Explorer
  3. Developers started targeting only that one browser: instead of making websites, developers started making “Internet Explorer sites” which were only tested in that one browser or, worse yet, only worked at all in that browser, actively undermining the Web’s position as an open platform. As the grip of the monopoly grew tighter, technological innovation was centred around this single platform, leading to decade-long knock-on effects.
  4. The Web ceased to grow new features: from the release of Internet Explorer 6 there were no significant developments in the technology of the Web for many years. The lack of competition pushed us into a period of stagnation. A decade and a half later, we’re only just (finally) finishing shaking off this unpleasant bit of our history.
    "Netscape sux"

History looks set to repeat itself. Substitute Chrome in place of Internet Explorer and update the references to other web browsers and the steps above could be our future history, too. Right now, we’re somewhere in or around step #2 – Chrome is the dominant browser – and we’re starting to see the beginnings of step #3: more and more “Chrome only” sites. More-alarmingly this time around, Google’s position in providing many major Web services allows them to “push” even harder for this kind of change, even just subtly: if you make the switch from Chrome to e.g. Firefox (and you absolutely should) you might find that YouTube runs slower for you because YouTube’s (Google) engineers favour Google’s web browser.

Chrome is becoming the new Internet Explorer 6, and that’s a huge problem. Rachel Nabors wrote in her excellent article The Ecological Impact of Browser Diversity:

So these are the three browser engines we have: WebKit/Blink, Gecko, and EdgeHTML. We are unlikely to get any brand new bloodlines in the foreseeable future. This is it.

If we lose one of those browser engines, we lose its lineage, every permutation of that engine that would follow, and the unique takes on the Web it could allow for.

And it’s not likely to be replaced.

The Circle of Browsers, by Rachel Nabors

Imagine a planet populated only by hummingbirds, dolphins, and horses. Say all the dolphins died out. In the far, far future, hummingbirds or horses could evolve into something that could swim in the ocean like a dolphin. Indeed, ichthyosaurs in the era of dinosaurs looked much like dolphins. But that creature would be very different from a true dolphin: even ichthyosaurs never developed echolocation. We would wait a very long time (possibly forever) for a bloodline to evolve the traits we already have present in other bloodlines today. So, why is it ok to stand by or even encourage the extinction of one of these valuable, unique lineages?

We have already lost one.

We used to have four major rendering engines, but Opera halted development of its own rendering engine Presto before adopting Blink.

Three left. Spend them wisely.

As much as I don’t like having to work-around the quirks in all of the different browsers I test in, daily, it’s way preferable to a return to the dark days of the Web circa most of the first decade of this century. Please help keep browsers diverse: nobody wants to start seeing this shit –

Best viewed with Google Chrome

Update: this is now confirmed. A sad day for the Web.

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How Edge Follows In IE’s Security Failings

I’ve generally been pretty defensive of Microsoft Edge, the default web browser in Windows 10. Unlike its much-mocked predecessor Internet Explorer, Edge is fast, clean, modern, and boasts good standards-compliance: all of the things that Internet Explorer infamously failed at! I was genuinely surprised to see Edge fail to gain a significant market share in its first few years: it seemed to me that everyday Windows users installed other browsers (mostly Chrome, which is causing its own problems) specifically because Internet Explorer was so terrible, and that once their default browser was replaced with something moderately-good this would no longer be the case. But that’s not what’s happened. Maybe it’s because Edge’s branding is too-remiscient of its terrible predecessor or maybe just because Windows users have grown culturally-used to the idea that the first thing they should do on a new PC is download a different browser, but whatever the reason, Edge is neglected. And for the most part, I’ve argued, that’s a shame.

Edge's minimalistic Certificate View.
I ranted at an Edge developer I met at a conference, once, about Edge’s weak TLS debugging tools that couldn’t identify an OCSP stapling issue that only affected Edge, but I thought that was the worse of its bugs… until now…

But I’ve changed my tune this week after doing some research that demonstrates that a long-standing security issue of Internet Explorer is alive and well in Edge. This particular issue, billed as a “feature” by Microsoft, is deliberately absent from virtually every other web browser.

About 5 years ago, Steve Gibson observed a special feature of EV (Extended Validation) SSL certificates used on HTTPS websites: that their extra-special “green bar”/company name feature only appears if the root CA (certificate authority) is among the browser’s default trust store for EV certificate signing. That’s a pretty-cool feature! It means that if you’re on a website where you’d expect to see a “green bar”, like Three Rings, PayPal, or HSBC, then if you don’t see the green bar one day it most-likely means that your connection is being intercepted in the kind of way I described earlier this year, and everything you see or send including passwords and credit card numbers could be at risk. This could be malicious software (or nonmalicious software: some antivirus software breaks EV certificates!) or it could be your friendly local network admin’s middlebox (you trust your IT team, right?), but either way: at least you have a chance of noticing, right?

Firefox address bars showing EV certificates of Three Rings CIC (GB), PayPal, Inc. (US), and HSBC Holdings plc (GB)
Firefox, like most browsers, shows the company name in the address bar when valid EV certificates are presented, and hides it when the validity of that certificate is put into question by e.g. network sniffing tools set up by your IT department.

Browsers requiring that the EV certificate be signed by a one of a trusted list of CAs and not allowing that list to be manipulated (short of recompiling the browser from scratch) is a great feature that – were it properly publicised and supported by good user interface design, which it isn’t – would go a long way to protecting web users from unwanted surveillance by network administrators working for their employers, Internet service providers, and governments. Great! Except Internet Explorer went and fucked it up. As Gibson reported, not only does Internet Explorer ignore the rule of not allowing administrators to override the contents of the trusted list but Microsoft even provides a tool to help them do it!

Address bars from major browsers connecting to a spoofed site, with EV certificate "green bars" showing only in Internet Explorer and Edge.
From top to bottom: Internet Explorer 11, Edge 17, Firefox 61, Chrome 68. Only Internet Explorer and Edge show the (illegitimate) certificate for “Barclays PLC”. Sorry, Barclays; I had to spoof somebody.

I decided to replicate Gibson’s experiment to confirm his results with today’s browsers: I was also interested to see whether Edge had resolved this problem in Internet Explorer. My full code and configuration can be found here. As is doubtless clear from the title of this post and the screenshot above, Edge failed the test: it exhibits exactly the same troubling behaviour as Internet Explorer.

Thanks, Microsoft.

Safari doesn't fall for it, either.
I also tried Safari (both on MacOS, above, and iOS, below) and it behaved as the other non-Microsoft browsers do (i.e. arguably more-correctly than IE or Edge).

I shan’t for a moment pretend that our current certification model isn’t without it’s problems – it’s deeply flawed; more on that in a future post – but that doesn’t give anybody an excuse to get away with making it worse. When it became apparent that Internet Explorer was affected by the “feature” described above, we all collectively rolled our eyes because we didn’t expect better of everybody’s least-favourite web browser. But for Edge to inherit this deliberate-fault, despite every other browser (even those that share its certificate store) going in the opposite direction, is just insulting.

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The Latest Stupidity From The Internet Explorer Team

Have you seen the latest stupidity that the Windows Internet Explorer team have come up with? Ten Grand Is Buried Here.

The idea is that they encourage you to give up whatever browser you’re using (assuming it’s not Internet Explorer 8), calling it names (like “old Firefox” if you’re using Firefox, “boring Safari” if you’re using Safari, “tarnished Chrome” if you’re using Chrome, and… “that browser” if you’re using Opera) and upgrade to Internet Explorer 8, and they’ll be giving out clues on their Twitter feed about some secret website that’ll only work in IE8 at which you can register and win $10,000AUS (yes, this is an Australian competition).

After looking at the site in Firefox, Safari, Chrome, and Opera, I thought I’d give it a go in Internet Explorer 8. But it didn’t work – it mis-detected my installation of IE8 as being IE7 (no, I didn’t have Compatability Mode on).

In the end, though, I just used User Agent Switcher to make my copy of Firefox pretend to be Internet Explorer 8. Then it worked. So basically, all that I’ve learned is that Firefox does a better job of everything that Internet Explorer does, including viewing websites designed to only work in Internet Explorer. Good work, Microsoft. Have a slow clap.

Microsoft Visual Studio 2005

Would you like to share your setup experience with Microsoft?

What is a “setup experience”? And why do Microsoft want to share it with me, anyway?

Improved performant!

I can’t actually find a definition of the word “performant” – can anybody help?

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The Right To Read

[this post was lost during a server failure on Sunday 11th July 2004; it was partially recovered on 21st March 2012]

If you haven’t already read it, take a look at The Right To Read, a very short story written in 1997 and updated in 2002 – it’ll only take you a few minutes to read; it’s not ‘techie’ (anybody would understand it!), and it is relevant. The kind of things that are expressed in the story – while futuristic (and facist) sounding now, are being put into effect… slowly, quietly… by companies such as Sony, Phillips, Apple, and Microsoft: not to mention the manufactors of CDs and DVDs.

It’s been circulating the ‘net for years, but recent events such as InterTrust’s Universal Digital Rights Management System (report: The Register), which they claim will be ready within 6 months, and Microsoft’s ongoing work on the ‘Palladium’ project (report: BBC News) – topical events which mark the beginning of what could be the most important thing ever to happen in the history of copyright law, computing, and freedom of information.

So, go on – go read… [the remainder of this post, and three comments, have been lost]