the Production of artificial Cold. 
127 
Series I. 
Exp. 1st. Muriate of lime 3, Snow 2, - - at -f 32° - - gave — 50 0 * 
2d. 2, 1, - - - o - - - — 66 * 
3 d. 3, 1, 4 °° 73 ° 
4th. Diluted vitriolic acid 10, t 8, - - — 68° - - — 91°^; 
• This experiment being repeated, using ice-powder, (instead of snow,) gave — 5 1°; 
——that is, ice ground to very fine powder with the instrument described in Phil, 
Trans, for 1795, page 288. 
f Concentrated vitriolic acid 8 parts, water 4 parts, and rectified spirit of wine I 
part, mixed and cooled previously to the temperature of the air. 
J This experiment was made on the 10th of March last, and conducted by a series 
of three mixtures, thus. The materials for the second mixture, consisting of muriate 
of lime and snow, separated from each other by an intervening stratum of fine sand, 
were cooled in a large vessel, having a partition in the middle forming it into two com- 
partments, to near 40° below o, by means of a prior mixture of the same materials. 
The materials for the second mixture, cooled as above mentioned, were then mixed in 
each compartment of this double vessel, and let through an aperture at the bottom of 
each, (closed till then by a temporary partition,) into such an apparatus as that repre- 
sented in the drawing, which contained the materials for the third or last mixture, 
consisting of the diluted vitriolic acid and snow, which had already been separately 
cooled in their respective vessels, to near 40° below o. 
The thermometer represented in the drawing was then placed in the tube of the 
upper vessel ; and, when the snow was cooled to the utmost, viz. to near 70 below o, 
the cooled snow was forced through into the cup containing the acid, the vessels were 
separated, and the snow and liquor thoroughly mixed by means of the thermometer 
contained in its glass tube ; the thermometer was then withdrawn from the tube,, and 
stirred about in this last or third mixture, which, in ten seconds of time, indicated a 
cold of 91 s ! below o; twenty seconds more elapsed before the thermometer began to 
rise. The mouth of the cup in the vessel B was, in this instance, closed with waxed 
paper, in order that I might invert the vessel occasionally, to renew the mixture in it; 
and the cup itself was coated within-side with wax, in order to defend it from the 
action of the acid. 
