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WII. Account of an Experiment 7nade with 
a "Thermometer^ whofe Bulb was painted 
black, and expofed to the direSl Rays of the 
Sun : In a Letter from Richard Watfon, 
D. D. Regius Profeffor of Divinity at 
Cambridge, and F. R. S. to Mathew 
Maty, M. D. Sec. R. S. 
Heverfham, September 18, 1772. 
Dear Sir, 
Read Dec. 1, '|~^URING the hot weather, which 
I/?2 ' J / we had in the latter end of June 
and the beginning of July laft, I made an experi- 
ment at Cambridge, which 1 then thought no more 
of, but which an accident hath brought to my mind 
again ; and I now venture to fend you an account of 
it, in hopes that fome of your philofophical friends 
will take the trouble of profecuting it. I expofed 
the bulb of an excellent thermometer to the diredt 
rays of the Sun, when the fky was perfectly free from 
clouds: the mercury rofe to 108 0 of Fahrenheit’s 
fcale, and continued hationary. A fancy (buck me, 
to give the bulb a black covering ; this was eafily 
eifedted by a camel’s hair pencil and Indian ink ; the 
mercury 
