Glacier Work. — Scott. 22g 
From what has been said, a reason is indicated as to why 
the crevasses never extend completely through the larger and 
deeper glaciers, although they may be immense openings at the 
surface. 
Col. Ludlow says in regard to the series of 12 inch cubes 
which he tested, "It was found that when subjected to pres- 
sure from whatever direction, the ice almost invariably re- 
solved itself into small vertical columns, which, when the pres- 
sure v\-as continued, buckled slightly and compressed, until 
in several cases, under a further increase of pressure, the block- 
exploded with a loud report ; this, however, only in the case 
of the better and more compact specimens. By vertical col- 
umns is meant columns normal to the natural surface of the 
ice." * The results of Beach, Munn, and Reeves arc very 
similar in this respect, t for they say: 'Tee, when subjected 
to pressure, is resolved into columns whose direction is nor- 
mal to the surface which was in contact with the water while 
freezing." 
The same experimenters show, in a table, that when the 
temperature of the testing laboratory, as well as that of the 
ice-block tested, were well below 32"F., viz., 21.2T. for the 
laboratory, and 12.2'^F. for the ice block, the specimen always 
"broke suddenly" and usually with report, but when the tem- 
perature of the laboratory and test blocks were but a few de- 
grees below 32''F., many of the specimens "gave i^'ay grad- 
iially:'' 
These results indicate an inherent tendency in ice masses 
to rupture along planes normal to the natural surface of the 
ice. and also to exhibit brittleness under conditions where the 
temperature is well below 32° F. They further show that the 
breaking of ice at a low temperature is of the nature of a 
shock. Prof. Russell has observed in connection with glaciers, 
that the formation of cracks which later open as crevasses i? 
attended by rumbling noises and sharp crashes, with vibrations 
of the ice-mass as though an earthquake wave acted upc>n 
it. t 
Gravity, the dominant force in glacier motion, acting to 
urge forward the ice mass accomplishes the greatest movement 
♦Proceedings of Kng. Club of Phil.idelphia, cit. 
tDigest of Pliysioal Tests, cit. 
JGiaciers of Xorth America. Professor I. C. Russell, 1S97, p. -8. 
