^2 2 Mr. cavendish’s Obfervations 
freezing point on thermometers, and agreed in the fame refult, 
the quickfilver in the laft experiment being frozen by the na- 
tural cold of the atmolphere ; and in the former, by being im- 
merfed in, and in contadl with, a freezing mixture ; fo that 
this point appears to be determined in as fatisfadtory a manner 
as can be delired ; and the more fo, as it feems impollible that 
experiments Ihould be made with more care and attention, or 
more faithfully and circumftantially related than thefe have 
been. The lecond and third experiments alfo fhew, that 
quickfilver, as well as water, can bear being cooled a little be- 
low the freezing point without freezing, and is fuddenly heated 
to that point as foon as it begins to congeal. 
On the contra ft ion of quickfher in freezing. 
All thefe experiments prove, that quickfilver contracts or 
diminifhes in bulk by freezing ; and that the very low degrees 
to which the thermometers have been made to link, is owing to 
this contra&ion, and not to the cold having been in any degree 
equal to that fhewn by the thermometer. In the fourth expe- 
riment the thermometer A funk to - 450°, though it appeared by 
the fpirit thermometers that the cold of the mixture was not 
more than 5 0 or 6° below the point of freezing quickfilver. In 
the firfl experiment alfo, it funk to — 448°, at a time when the 
cold of the mixture was only z°\ below that point ; fo that it 
appears, that the contradlion of quickfilver, by freezing, muff 
be at leaf: equal to its expanfion by 404° of heat *. This, how- 
* The numbers here given are thofe fhewn by the thermometer without any 
correction; but if a proper allowance is made for the erroi of that inftrument it 
will appear, thet the true, contraction was 25° lefs than here fet clown, and from 
the manner in which thermometers have been ufually ndjufted, it is likely, that in 
the following experiment of Mr. hutchins, as well as thofe of Profeffor bRacn, 
true contraction might equally fall fhort of that fhewn by ohfervation, 
4 ever, 
