WW2 Air Raid Shelter at Reading University

This image from Google Street View of 2023 September shows what I think was a World War 2 air raid shelter that used to exist on the Reading University Whiteknights Park campus. It was probably built along with the so-called 'temporary' office buildings in the background for the Ministry of Works who were moved out of central London in 1940 to avoid the bombing. The door of the shelter is to the left of the (modern) light fitting, behind the little wall. The 'little wall' is a blast wall designed to collapse and absorb the force of a bomb explosion which would otherwise blow in the door and sent fragments into the shelter. (The main aim of these shelters was to protect from flying debris, not from direct hits which would have been much more expensive to do.) There is another air raid shelter in the wall of the car park of the local public house, the Three Tuns, which is about a quarter of a mile in the direction that the person in the image is walking. I like to speculate that this was the Ministry of Works protecting their employees both while they were at work and during their lunch breaks. Unfortunately, the above shelter and the office buildings were recently demolished to make way for ECMWF. However, I understand that the Three Tuns shelter is still there, though I haven't checked up on it for several years.

Multiple accounts with the same hosting provider over SSH

It is fairly common to want to set up two SSH connections from a given machine to the same remote host. For example you might have both a work and a personal account on Github and you might want to pull and push changes from work and personal repositories on your machine.

If you just follow the instructions for setting up a single SSH connection and repeat it twice, your scond connection will probably not work because SSH on your machine will use the first account name to try to connect to the second account.

The way to fix this is to set up a .ssh/config file in which you define aliases for your two accounts, for example: github.com_work and github.com_personal. Then you use these aliases in the git config remote.origin.url in the respective repositories, for example:

git config remote.origin.url git@github.com_work:account_name_work/project_name

git config remote.origin.url git@github.com_personal:account_name_personal/project_name

For an example of the .ssh/config file see the Git FAQ.

The Origin of Henge Monuments

The following is a comment I posted on mathstodon.xyz:

My personal theory for the origin of henge monuments and stone circles is that they evolved from the rituals performed by seminomadic people during the mesolithic when they returned to their summer camp site in the spring (or to their winter camp site in the autumn). All they find left of their previous home is the circle of wooden posts which held up the walls and the circular drip trench outside them. They repair the posts where necessary and then construct the framework of a conical roof above the posts and cover it and the walls with hides. They also clear out any foliage from the drip trench and redig it where necessary. They then go around and tend to the graves of those who died on previous visits to that camp. At the end of the season they dismantle the roof and pack up the hides and take them with them to their alternate camp site. After thousands of years of this, the people settle down at a permanent camp site, but they keep up the rituals ("because that is what we've always done!"). After a few more thousand years of rivalry between neighbouring families you end up with something like Stonehenge.

Although I haven't seen this theory mentioned anywhere, it does seem to explain several of the key features of henge monuments: the circle of wooden posts (stone posts only came later); the circular ditch outside the posts; the association with graves; and the association with processional ways.

This idea was partly inspired by memories of a childhood visits to an excavated Iron Age famstead on the North York Moors, near where we lived. The farmstead consisted of three or four round-houses of which only the base of the stone walls and central hearth-stones remained. The excavators had scooped out the drip-trenches around the walls, leaving only the entry path in front of the door-ways. As a child, I was fascinated by the thought that I was running in and out of the door-ways in the same way that children must have done two thousand years before.

Books

I am currently reading:

• The Buried Giant by Kazuo Ishiguro
• Doomsday Book by Connie Willis
• The Sorcerer's Apprentice by David Bronstein and Tom Fürstenberg (a chess book)

Simula 67 as a successor to Algol 60

From "Software Engineering: As it was in 1968" by Brian Randall:

In the more rarified ALGOL world in which I moved, 1968 was something of a watershed. The IFIP ALGOL Committee (Working Group 2.1) which had been set up following the publication of the original ALGOL 60 Report, met in Munich not long after the Software Engineering Conference. A week-long debate of remarkable intensity culminated in a majority decision to approve the ALGOL 68 report that had been prepared by van Wijngaarden, Mailloux, Peck and Koster (41). In response, a renegade group (of which I was a member) produced a brief Minority Report (18), in which we stated that "it will be required from an adequate programming tool that it assists, by structure, the programmer in the most difficult aspects of his job, viz. in the reliable creation of sophisticated programs. In this respect we fail to see how the language proposed here is a significant step forward". My own recollection in fact is that several of us felt even then that the recently proposed SIMULA 67 Common Base Language (12) came closer to our ideal, and would perhaps turn out to have at least as much impact as an officially promulgated ALGOL 68.

I have known a long time (mainly from the writings of Edsger Dijkstra) about how in 1968 the Algol Committee split over the decision to approve van Wijngaarden's Algol 68 language, with a significant minority issuing their own report saying it was too complex to create reliable software with. I had always assumed that the minority would have preferred something like Wirth's Algol W, but from what Randall says above they might have actually gone for Simula 67. Now that would have been something. It would probably have brought forward the flourishing of object-oriented programming by over a decade