under pressure at Temperatures below 32° F. 445 
ag guaa seems wholly unwarranted. I have only to refer 
ction of ice in the iron press, with its slow and 
Moreover, I have endeavored by actual — to obtain the 
-extreme effect of such pressures as have been used—pressures 
not so great indeed as the highest of those state with the iron 
press—but great enough to convert snow into ice at very low 
temperatures. 
The most reliable of these observations have been made 
upon not very cold snow with pressures rising from 580 Ibs. 
to the square sare to a possible maximum of 2,000 Ibs. to the 
square inch. shall hereafter give cases of the glaciation of 
snow of low temperature under the latter pressure. The 
method of testing has been as follows: The temperature of the 
air, and the snow before pressure is noted, and in some cases, 
also, the temperature of the moulds. Then pressure is rapidly 
applied to the snow in the moulds by sudden impact of the 
crew. A wire in the bottom of the plunger leaves a fine bore 
in the pressed snow for the insertion of a thermometer, and the 
-of the plunger. In some instances pains have been taken to 
aggravate the rise of temperature by sudden and violent im- 
pact; throwing myself on to the handles of the screw with all 
my might. Now the highest elevation I have been able to 
obtain by this violent method of applying a pressure of 1,500 
to 2,000 lbs. to the square inch, sat only one minute, was 
32°F. The pressure exerted was my whole strength applied 
to the handles of the screw by sudden and violent efforts. 
pica ne 2 the temperature of the moulds before pressure 
not o d. 
ee the cae next observation recorded, I find the same opera- 
tion gone through with, except that the violent impulses were 
repeated, at intervals, during twenty minutes. The gape 
He) the same as before, but the elevation effected w ] 
1 
pressure was applied, only two minutes, to a mo ould 
tilled with bits of ice. The temperate of the air and of the 
moulds before arr ee ‘gov at 27° F. The ice before 
pressure measures 25° F = Brebae esse 27° F. The eleva- 
tion in this case was deabiien « ed by that of the moulds, 
-and in the case before given, as the temperature after pres- 
sure rose to 32° F., it is very probable that the temperature of 
e moulds was higher than that of the snow; while in the 
second case, there is reason to think it was lower than that of 
