Hygrometry . 3 
not conceiving yet any known limit to the intenfity of heat > 
I could not expefl any limit to drynefs , nor even a fixed degree 
of it. 
2. I remained at that point, with however a comparable hy- 
grometer laboriously conftrufted, till I came to conceive, that 
heat mult be at its maximum in a body, when it is mean - 
defeent ; which opinion I have explained in my work, Idees fur 
la Meteorologie . From that firft idea I foon after concluded ; 
that every hygrofcopic fubftance, which could retain that pro- 
perty after having been brought into incandefcence , would 
anfwer my firft purpofe, The following Is the theory refult- 
ing from the whole of the above considerations, ift, The 
hygrofcopic fubftance which has the moft capacity for moijlure , 
and receives it the moft readily, being placed in any quantity in 
a given fpace, cannot bring that fpace to a degree of drynefs 
greater than its own ; and if that degree is undetermined, it 
cannot afford any fixed point for the hygrometer . 2d, The 
hygrofcopic fubftance which has the fmalleft capacity for moifi 
ture , and is the flowed in receiving it, if it is really reduced to 
extreme drynefs , will have the power of producing it in a given 
fpace, provided its fmall capacity be compenfated by a greater 
quantity, and its flownefs by more time. 3d, Every hygro - 
fcopic fubftance, which may be brought to white heat without 
lofing its property, is fit to produce extreme drynefs in a dole 
fpace. 4th, It is indifferent for that purpofe, that the fub- 
ftance ufed be of the clafs which has a chemical ajfinity with 
water , it being fufficient that, after having been reduced to 
extreme drynefs it be ftill capable of receiving it from the am- 
bient medium , as may every porous fubftance. 5th, But for 
the praflical purpofe of fixing the point of extreme drynefs on 
hygrometers , luch a fubftance muft be chofen as, with a great 
B 2 capacity 
