on the Production of artificial Cold. 28 5 
temperature of the mercury was 45 0 , fo that, the freezing point 
of that metal being - 39°, there were produced 84 degrees of cold. 
This experiment was performed as follows. Four pans, of 
fizes progreftivsly diminifhing, fo that one might be placed 
within the other, were procured. The largeft of thefe pans 
was placed in another veiled Hill larger, in which the materials 
for the fecond frigorific mixture were thinly fpread, in order to 
be cooled. The fecond pan, containing the liquor (viz. vitrio- 
lic acid, properly diluted) was placed in the largeft pan. The 
third pan, containing the falts for the third mixture, was im- 
merfed in the liquor of the fecond pan ; and the liquor for 
the third mixture was put into wide-mouthed phials, which 
were immerfed in the fecond pan likewife, and floated round 
the third pan. The fourth pan, which-was the fmalleft of 
all, containing its cooling materials, was placed in the midft of 
the falts of the third pan. 
Of the materials for the mixtures to be made in thefe four 
pans, the firftatid fecond conlifted of diluted vitriolic acid and 
Glauber’s fait, the third and fourth of diluted nitrous acid, 
Glauber’s fait and fal ammoniac, in the proportions afligned. 
The pans being adjufted in the manner above delcribed, the 
materials of the firft and largeft pan were mixed : this mixture 
reduced the thermometer to +10, and cooled the liquor in the 
fecond pan to -j- 20 ; and the falts for the fecond mixture, which 
were placed underneath in the large veflfel, nearty as much. 
The fecond mixture was then made with the materials thus 
cooled, and it reduced the thermometer to 3 0 . The ingredients 
of the third mixture, by immerfion in this, were cooled to 
+ io°, and when mixed reduced the thermometer to — 15 0 . 
The materials for the fourth mixture were cooled by immerfon 
in this third mixture to about - 1 2 0 . On mixing they made 
the mercury in the thermometer fink rapidly, and as it 
Vol. LXXVI 1 . T t ’ appeared 
