on Mr. hutchins’s Experiments . 317 
x his experiment, therefore, affords a freSh confirmation that 
tiie point of rhercurial congelation is — 40° on thefe thermo- 
meteis , and that quicksilver will bear being cooled a little be- 
low that point without freezing. 
As in thefe two experiments the quickfilver in the cy- 
linder and ivory thermometer bore being cooled a few de- 
grees below the freezing point without freezing, it is 11a- 
tuial to conclude, that the fame fluid in the wooden ther- 
mometer fhould do fo too ; and it may, perhaps, be fup- 
pofed that, in confequence of it, this thermometer, after hav- 
ing funk a little below the point of freezing, ought fuddentv 
to have nfen up to it, which was not obferved. But there is 
great reaSon to think, that though the quickfilver in it did bear 
cooling 111 this manner, it would not have occafioned any fuch 
appearance : for fuppofe that it is cooled below the freezing- 
point, and then fuddenly freezes, its bulk will be mcreafied, on 
account of the heat generated thereby ; but then it will be di- 
minished on account of the contraction in freezing; fo that, 
unlefs the expanfion by the heat generated exceeds the contrac- 
tion by freezing it will caufe no rife in the thermometer. I do 
not, indeed, know how much the heat generated by freezing 
in quickfilver is, but in water it is about 1 50°, and the con- 
t faction by freezing is at leaf: as much as its expanfion by 400° ; 
fo that, unlefs the heat generated by freezing is two or three 
times as great in quickfilver as in water, the thermometer 
ought not to rife on this account. 
In the fourth, fifth, Sixth, and Seventh experiments a new 
phenomenon occurred, namely, the ivory thermometer funk a 
great deal below the freezing point without ever becoming Sta- 
tionary at — 40 k Li the fifth experiment, tried with the ap- 
paratus O, it quickly funk to —424 and then, without re- 
maining Stationary at any point, funk in half a minute to 
