on Mr. hutchins’s Experiments. 327 
is as great a degree of cold, within i°, as was produced in any 
of Mr. Hutchins’s experiments. 
In this experiment the thermometer G funk very rapidly, 
and, as iai as I could perceive, without hopping at any inter- 
mediate point, till it came to the above-mentioned degree of 
-iio°, where it buck. The materials ufed in making the 
mixture were previoufly cooled, by means of fait and fnow, to 
near nothing ; the temper of the air was between 20° and 25 0 ; 
the quantity of acid ufed was 44 oz. ; and the glafs in which 
the mixture was made was furrounded with wool, and placed 
in a wooden box, to prevent its lofing its cold fo faff as it would 
otherwife have done. 
Some weeks before this, 1 made a freezing mixture with 
fome fpirit of nitre, much hronger than that ufed in the fore- 
going experiment, though not quite fo ftrong as the undiluted 
acid, in which the cold was lefs intenfe by 4 °|, as the thermo- 
meter G funk to — 40°! . It is true, that the temper of the 
air was much lefs cold, namely, 35 0 ; but the fpirit of nitre 
was at lead: as cold, and the fnow not much lefs fo. The ex- 
periment was tried in the fame veflel and with the fame precau- 
tions as the former. 
The cold produced by mixing oil of vitriol, properly diluted 
with fnow, is not fo great as that procured by fpirit of nitre, 
though it feems not to differ from it by fo much as 8° ; for a 
freezing mixture* prepared with diluted oil of vitriol, whofe 
faid to be — 35 0 , and the temper of the air above -f-20. Therefore, the cor- 
rection nnift be equal to the expanfion of a column of fpirits 155° long, by an 
alteration of heat equal to 55 0 on this thermometer, which, if i° on the fcalc 
^ ^ ICC 
anfwers to -^V^th of the bulk of the fpirit, is equal to or 5 
Vol* LXX 11 I. X x 
fpecific 
