DURING A RECENT visit to Cambridge, I noticed a hemispherical cavity into which an electric doorbell push button had been fitted. it was at Peterhouse College. I posted a picture of it on Facebook and received the following range of replies and reactions to it. Here they are in the order they appeared:

“My guess is there used to be a handle in there to operate a mechanical bell. There would have been a brass escutcheon plate, dished like the hole to accommodate the clenched hand grasping the handle. There seems to be a void behind the current bell button, the linkage probably went through there. You can see a shadow either side, rather like a bow tie, where the escutcheon was.”

“.. pull a cord or chain?”

“That will summon David Jason.”

“A square bell in a round hole”

“This was my husband’s college (about 45 years ago). I’m sure he’ll remember this well.”

“Yes, but I would expect the bar or chain operating the original to come straight out of the back of the cone, and there’s no hint of that.”

The range of comments was from frivolous to informative. I find that posting interesting items on Facebook often elicits useful information about them. By judicious posting and cross-checking information provided, Facebook can become a useful research tool.