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fphere of air, cooled on one fide to 9 8°, by being in contact 
with our bodies, and on the other fide heated very flowly, 
becaule woollen is fuch a bad condudtor of heat. Ac- 
cordingly I found, tovrard the end of the firfl experiment,; 
that a thermometer put under my do aths, but not in con- 
tad with my fidn, funk down to 1 1 o”. On this princi- 
ple it was that the animals, fubjeded by M. tillet to> 
the interefiing experiments related in the Memoirs of the 
Academy of Sciences for the year 1764, bore the oven 
fo much better when they were cloathed, than when they 
were put in bare r the heat adually applied to the greatefi: 
part of their bodies was confiderably lefs in the firfi; cafe- 
than in the lafl. As animals can deftroy only a certain 
quantity of heat in a given time, fo the time they can 
continue the full exertion of this deftroying power feems 
to be alfo limited; which may be one reafon why we 
can bear for a certain time, and much longer than can 
be neceflary fo fully heat the cuticle^ a degree of heat 
which will at length prove intolerable. Probably both 
the power of deftroying heat, and the time for which it 
can be exerted, may be increafed, like mofi: other facul- 
ties of the body, by frequent exercife. It might be partly 
on this principle that, in M. tillet’s experiments, the 
girls who had been ufed to attend the oven bore, for ten 
minutes, an heat which would raife Fahrenheit’s ther- 
mometer to 280®: in our experiments, however, not 
one of us thought he fuftered the o reatefi: cleF'ree of heat 
o 00 
that he was able to fupport. 
A principal 
