under pressure at Temperatures below 32° F. 451 
ciation in twenty minutes, with some darkening of snow in 
five minutes. ; 
In the next five trials, from No. 12 to No. 16 inclusive, we 
Vv of only two degrees of temperature, and such a 
relation of times and p res as will throw, perhaps, some 
light on the cat under discussion. We will arra eee these 
No. 15.; 20°F. | 10m. 575to 775 Ibs. | Sub-vitreous, granuiar. 
Ss Sub-vitreous, opaque. 
No.14| 20°F. | 2m. 950 to 1275 Ibs. ; Gratis, pes white 
No. 13° | .21° F. .| 46 m. 950 to 1275 lbs. | Good vii ricng white. 
No. 12 | 22°F. 3 hours 950 to 1275 lbs. 
No. 16 | 20°F. 3 hours | 1200 to 1600 Ibs. 
Vitreous, dark, translucent. 
Ice- sharaueee well advanced, 
Good ice. 
The pressures in Nos. 14, 13, and 12 are the same, and the 
temperatures so near together as to point pretty Tiekindly: to 
ime 
assing Over the higher pressures and long times in the 
_ lower part of the table, I call attention to Nos. 21 and 25. 
ow as —2° F., under a pressure ss Reape less ae! 2,000 
points to the square inch, glaciati may be very far 
advanced ; but it is roe to be noticed ‘that ~ — pe ress- 
nature observe ey experimenting upon prisms; taken also 
process of glaciation. Dayenn: early e by observa- 
tions have grown into a strong con ee that glaciation 
would take place in a few dap under the moderate pressure of 
say 1,000 pounds to the square inch, allowed to bear _— 
and continuously on snow the temperature of which did no 
exceed that ” zero, Fahrenheit. 
The’ of these observations a now be briefly 
summed up. We tn may re fond as establishe 
(1.) That broken prisms of ice, at temperatures far below 
32° F., will firmly reunite if the faces of fracture are brought 
together and a very moderate but long continued pressure is — 
applied. 
