29^ Mr. wilson’s farther 
If the air, at low temperatures, had any pbwer of a&ing 
upon the fnow or hoar-froft, fo as to produce a gradual melt- 
ing, this circumftance, according to the known laws of heat, 
might occafion the difference of temperature under con fi de- 
ration. And what renders this idea not altogether improbable, 
is the peculiar cohefion among the parts of the fnow above de- 
fcribed. Perhaps a gentle melting might take place without 
much altering the appearance of the fnow or hoar-froft at the 
fur face, as the parts, when diflolved, might be gradually 
fucked downwards, and be afterwards diftributed through the 
whole drier mafs. It may alfo be worthy of an experimental 
inquiry to determine, how far that fort of concretion, ob- 
fervable all over the furface of fnow which has been long fro- 
zen, bears any marks of a flow procefs of this kind. From a 
hill, a little way to the N.E. of the town, and which was to 
windward during the froft, there were gathered two portions of 
fnow, the one from the furface, and the other feven inches 
below it. The water produced from the two kinds is preferved 
in very clean phials, in order to be compared together by fome 
> chemical trials, which, perhaps, may throw fome light upon 
the whole of this matter. 
At prefent I fhall conclude this letter, perhaps already much 
too long, with juft mentioning one other faft which was new 
to me ; namely, the power of ardent fpirits of diflolving fnow, 
and confequently of producing with it a freezing mixture. 
The alcohol and fnow feparately were at eight degrees below the 
freezing point, and vchen mixed fuddenly and intimately, the 
temperature became in the fpace of twenty feconds 28° below 
o. This is a cold only 12 0 fhort of that which Fahrenheit 
f^rft produced by ufing fpirit of nitre for the experiment ; and 
it 
