On Saturday, 24 September 2016 08:09:57 UTC+1, Weatherlawyer wrote:

It should be relatively cheap to find out. Anyone on here competent enough to make a thermoscope?

That bit about the thermoscope was absolute tosh, I'd thought he was going to use a mirror and ice presuming he knew enough about the inverse square rule for distances -but of course he may have been uninformed abou Mme du Chatelet's work:
https://en.wikipedia.org/wiki/%C3%89...Heat_and_light hard to believe though.

Impossible to believe!

Rumford was born in 1753 just after she died and must have read her translation of Newton as well as her dissertation on IR light. So when was polarised light discovered I believe it was around that time with the discovery of organic chemistry and the examination of sugar solutes.

And how would cold affect mirrors?
I can understand the temperature drop with the glass screen especially considering the quality of glass in that era. But it is a little beyond me how a bit of ice would render a tin mirror US. OTOH of course, what do I know about polarity. Nor how sensitive there measurements were.

OT: The theories about heat may well have been made more difficult if the heat source used in the day were spirit, paraffin or wax rather than charcoal. More profoundly as the flammability of liquids increases with height, whilst charcoal does not.