84 THE ANTARCTIC MANUAL. 
equal proportions would be somewhere near the middle, or about 
—18°8 C. But this is not so. The cryohydric temperature of a 
mixture of the two salts lies below that of either of the salts; and 
the same is the case even with the mixtures of the chlorides of 
sodium and of potassium, the cryohydric temperatures of which are 
so far apart. 
The following rough observations (Table II.) were made in the 
Engadine on September 20, 1897, when a heavy snowfall occurred. 
Taste II. 
Siow Salt a. Salt 0. Cryohydric 
Weight. : Temperature. 
Formula. Weight. Formula. Weight. 
grms. grins. grms. °C. 
20 NaCl 32 we os —21:0 
32 KCl 38 a me —11°0 
34 NH,Cl 22 is . -15'8 
36 NaCl 11:7 KCl 14:9 —23°0 
42 NaCl 11:7 NH,Cl 10°7 —24°8 
i BaCl,2H,O 25 re A -~ 7:9 
48 Ba(NO,), 27 oh FS — 10 
73 BaCl,2H,O 12-2 Ba(NO,), 13:07 — 86 
The temperatures were all observed with the same thermometer 
and no correction has been applied. The temperature marked 
—0°°3 C. in melting snow, which makes the determined cryo- 
hydric temperature of nitrate of barium agree with that found by 
de Coppet, namely —0°°7C. The thermometer was one of ordinary 
German manufacture divided into whole degrees. The observa- 
tions illustrate the fact that the cryohydric temperature of a 
mixture of two salts is lower than that of the salt which separately 
has the lower cryohydric temperature of the two. The mixtures 
experimented on were of equal molecular proportions, in fine 
powder, intimately mixed with dry powdery snow. Perhaps the 
most remarkable mixture in the table is that of the chloride and 
nitrate of barium : the cryohydric temperature of the mixture is nearly 
the sum of the separate cryohydric temperatures. In almost every 
case where accurate observations have been made, it has been found 
that the melting temperature of a mixture is lower than that of the 
most fusible of its components. The frequency of this observation 
has justified its enunciation as a law, and the recognition and elabo- 
ration of this law have done much for the advancement of physical 
