the Congelation of Zhiickfiher, 
fnow and fmoaking acid of nitre, even with the advantage of 
fuch natural cold as congealed the quickfilver expofed to it, was 
only to diminifh the heat to fuch a degree as would correfpond 
with — 45 0 or - 46° of a ftandard mercurial thermometer ; and 
confequently that the cold obtained by Fahrenheit in the firft 
experiments with fuch mixtures, which eoeri-iaave ftates at 
- 40 0 *, cannot be exceeded but by a very few degrees. This refult 
is the morefurprifing, on account of braun’s pofitive aflertions, 
that his thermometer both of redtified fpirits and eflential oils 
defcended 150 or at lead 100 degrees below of. But, fmce 
that gdhtleman was ftrongly impreffed with an opinion of the 
exceffive cold neceflary to freeze quickfilver, fo much as to 
fhew evident perplexity at finding his lpirit-thermometers fink 
lefs than thofe of mercury, I fhould, from thi 3 circumftance 
alone, be inclined to place mofl confidence in the experiments 
made at Hudfoif s Bay, in which no hypothecs was adopted, 
and therefore no prejudice can be apprehended. Indeed Mr. 
Hutchins’s obfervations with regard to the degree of cold ge- 
nerated by his freezing mixtures, are lo regular, uniform, and 
numerous, as hardly to leave a doubt that it does not exceed 
_ 35° or -36° of his fpirit-thermometers* And this is, of 
itfelf, a very great additional proof, that the freezing point of 
quickfilver cannot be much lower than Mr. hutchins deter- 
mines it, fmce the mixture was incapable of diminifhing the 
heat more than fix or feven degrees further. The advantages 
arifing from a knowledge of the cold produced, were fo apparent 
in thefe experiments at Hudfon’s Bay, with refpect to many 
circumftances, both m the congelation of the quickfilver itfelf, 
* eoerhaav. Element. Chemite, tom. I. p. 164. 
4 Nov. Comment. Petrop. tom. XI. p. 290. 3 I ^ t 3 * 7 * ^6o to ^00 
of be l’ isle’s lcale. j 
A a a a 
