[ ^57 J 
But fourthly j The quantity of a body diUblved, 
and of a fluid evaporated, in a given time, depends 
(ceteris paribus) on its quantity of furface. Thus a 
body reduced to powder is fooner diflblved than 
when it is in a folid form. And thus fmoak, or 
fleam, which is water, reduced to very fmall parti- 
cles by heat, is much fooner difperfed, and incorpo-^ 
rated with air, than water in its ufual form. 
Fifthly} Chy mills obferve, that when fea fait, fal^ 
ammoniac, or nitre, is diflblved in water, or eflbn- 
tial oyls in fpirit of wine, fome degree of cold is 
produced in the immediate a£l of folution ; and the 
quicker the folution, the greater is the cold. And < 
by diflblving pounded ice, or rather fnow, (whofe 
particles have a greater furface) in fpirit of nitre, a 
degree of cold has been produced fo great as to freeze 
quick-filver. Gold is likewife produced in the adt 
of evaporation; for if fpiiit* of wine, or aether, 
having the fame temperature with the air, be rubbed 
lightly with a feather over the ball of a thermome- 
ter, it will fink as the fpirits evaporate, and the 
quicker they evaporate, the fafter will the thermo-- 
meter fink. And the fame, thing wiir happen if 
water be ufed inftead of fpirits, . provided its evapo- 
ration be promoted by a flrong current of air. And . 
thus have. I leen ice produced meerly by repeated 
evaporations of aether. 
This lafl: obfervation . fliew& a very remarkable 
agreement between the natures of folution and eva- 
poration. How the cold is produced in either cafe . 
I cannot pretend to fay ; but I. mufl beg leave juft 
to apply this fadl to account for a thing which I 
believe moft people have taken notice of. 
. < If. 
