Hot brain

This to notice a curious visual event - at a time when temperatures outside were in the high 20s (C). That is to say, far too hot for my comfort. 

The room concerned had a pair of French windows with a pair of curtains on a pole, one of which is suggested in the figure above; a white pole and a yellow curtain against a dark blue background. The top edge of the curtain has large eyelets through which the pole is threaded, in one eyelet and out the next. None of the white plastic 'Swish' fittings that we have been using for our own curtains since the 1970s - and which are now starting to rot.

One draws the curtain by simply pushing it all together, concertina fashion. Thus adding, as the décor people on daytime television would say, vertical interest to the scene.

The actual curtains are snapped above. The pole being much closer in colour to that of the curtain than to that of the beam of attachment, cutting across the top half of the snap.

The event was that while idly eyeing the curtains, chunks of the pole disappeared, as if while threading the pole through the eyelets, the threader had missed a few, with the curtain being more or less held up by the stiffness of the material from which it was made.

This is suggested in the figure above.

Eventually BH convinced me that there was nothing wrong with the curtains and that I was seeing things. This included going upstairs to make sure that I had got the right curtains.

I decided that what was happening was that the pole, which was shiny and reflective, was picking up the colour of the background, that is to say the colour of the curtains. The brain then tidied things up and tidied away the chunk of pole concerned altogether. This, even though, some other part of the brain knew all about how the pole was threaded through the curtain: communications had broken down. Or at the very least, degraded. Lost bandwidth.

But it all depended on how the light was doing, so the result was not very consistent. Some chunks of pole vanished, some survived. But the two ends, against a darker background, always survived.

Which is going to have to do, until some cunning reader comes up with a better suggestion.

PS 1: OS has just offered me what looked like a nice map of South London, from the very beginning of the 20th century, for a tenner or so. Unfortunately, Epsom is only just included, at the confluence of the railway lines, just left of bottom middle. One of the eventually five asylums is visible. Even so, I would pay a tenner for a full-on image, the sort of thing that some museums in the US offer for free - but I have so far failed to find a way to do that. And, not so unreasonably in this context, the version you can download for free, snapped above, is of rather low resolution. 

References

Reference 1: https://shop.osmaps.com/south-london-1896-1904/.