264 Dr. Falconer's Remarks on the 
Galen himfelf was perfonally well acquainted 
with this effedt of boiling, in difpofing water to 
cool more rapidly, and to a greater degree. 
tc When,” fays he, “we wifh to render water as 
cool as poffible, we firft heat it, then furround with 
fnow the veffel containing it, or, if fnow be wan¬ 
ting, we place it in the well or dream of a fpring, 
and thus its temperature is more eafily changed.” 
This he afcribes to the rarefaction the water 
had before undergone, which is evidently not 
the true caufe, as, upon cooling, it would be as 
much condenfed as before. Perhaps, the true 
caufe may be, what is generally afligned, the dif- 
charge of the air. But how does this operate 
in promoting the refrigeration ? Is it, that after 
the water has been freed of its air, any part 
of its latent heat has flown off with it, and thus 
rendered it more eafily acceflible to cold ? Or, 
is the refrigeration more eafy, on account of the 
difcharge of air j as the air, being united with 
the water, and requiring to be difengaged in 
freezing, might, by its attradlion to the water, 
require more cold to difengage it, than would 
have frozen the water, had it not had that at- 
tradtion to overcome ? 
It muff, however, be remarked, that Galen not 
only fpeaks of water that has been previoufly 
heated, being more eafy to be frozen , but alfo 
fays, fuch water is more eafily cooled, even to 
any 
