144 METEOROLOGICAL OBSERVATIONS. 
poration produces cold, Hamilton, in his excellent ef- 
fay upon the afcent of vapors, {peaking of the natures of 
folution and evaporation, has thefe words, ‘ how cold is 
‘¢ produced in either cafe, I cannot pretend to fay.’ The 
doctor has given the moft probable explanation of the 
manner in which it is. produced by folution, and I think 
the following, which is collected from his general dodtrine 
‘may be applied to evaporation. It is admitted that there 
is a ftronger attraction between heat and water, or fuch like 
fluid, than between heat and any other body, for on this 
account it is that bodies are cooled when plunged into wa- 
ter. When ever therefore, water for inftance, is put upon 
any part of the human body, its natural heat is more at= 
tracted in that part by the water, than by the flefh, and 
therefore, the water in going off in the form of vapour 
carries with it part of the heat, and confequently leaves 
that place in a negative ftate, or with lefs than its natural 
quantity. It is the fame with the thermometer. Hence 
it is, that we are much hotter frequently when the ther- 
mometer {carcely exceeds 82 or 83, there being no current 
of air to carry off the moifture from the furface of the body, 
than when it even ftands as high as go or gs. 
Iam, with the greateft refpect,. 
Your fervant and friend, 
J. MADISON. 
JULY, 
