Experiments on freezing Mixtures* zyf 
Though the foregoing experiments confirm the truth of 
what I faid, in the account of Mr, Hutchi&s’s experiments, 
concerning the caufe of the cold produced by mixing fliow 
with different liquors, and intirely clear up the difficulty re- ' 
lating to it which I mentioned in Art. i. yet feveral queftions 
may naturally occur $ fuch as, why the cold produced by the 
oil of vitriol was fo much greater than that obtained by the 
fpirit of nitre, notwithftanding that in warmer climates the 
nitrous acid feems to produce more cold ? and why the cold 
produced by the nitrous acid, notwithftanding its previous dilu- 
tion, which might naturally be expe&ed to be of fervice, was 
not greater than has been obtained by other perfons without 
that precaution ? But as this would lead me into difquifitions 
of confiderable length, without my being able to fay any 
thing very fatisfadtory on the fubjedt, I fhall forbear entering 
into it. I will only obferve, that in moft of the foregoing 
experiments, Mr. M c Nab would probably have produced 
more cold, if he had added the fnow fafter. We ought 
not, however, to regret that he did not, as its effedts on the 
acids would then have been lefs fenfible. 
The natural cold, when thefe experiments were made, is re- 
markable ; as there were at leaft nine mornings in which the 
cold was not lefs than that of freezing mercury ; four in which 
it was at leaft eight degrees below that point, or -47 0 ;. and 
one in which it was - 50°. Whereas out of nine winters, 
during which Mr. Hutchins obferved the thermometer at 
Albany Fort, there were only twelve days in which the cold 
was equal to that of freezing mercury, and the greateft cold 
feems to have been — 45 0 . I cannot learn whether the laft 
winter was more fevere than ufual at Hudfon’s Bay u r or whe- 
ther Henley-Houfe is a colder fit nation than Albany, which 
