under pressure at Temperatures below 32° F. 439 
w any moisture can intervene to assist in restoring the con- 
aay of the faces of broken prisms. In discussing the effects 
-of heavy pressure upon snow, this subject will come up again. 
But in the prisms, exposed to temperatures such as some of 
result. Tei is very true that Mr. Tyndall. whose howinitel ex- 
periments upon ice have attracted the admiration of all readers, 
found lines of moisture developed transversely to the direction 
-of pressure in masses of ice. But these observations were 
ys ogee Somes upon 32°, it is scarcely necessary to say, was 
due to the liquefaction of ice under pressure, domo: to 
the tise given by the brothers Thomson. Inasmuch as water 
expands in freezing, : was observed that by parenting the 
expansion of water through pressure, that fluid could be re- 
duced ohana degrees in temperature and still be kept in the 
fluid state. The brothers Thomson have given us the numer- 
the prisms were exposed (2 heed would a a ee of 
it is only by special contrivances that the conversion of snow 
into ice can be watched. My earlier trials, those to which 
allusion was made at Burlington and Chicago, were conducted 
with wooden moulds, into which the snow was packed, aud the 
UR. p+ edna Serres, Vou. XXIII, No. 138.—Junz, 1882. 
2 
