388 
REVIEW. 
ter of our floes, to determine pretty accurately before- 
hand the type of the approaching hummock. 
Sometimes a hummock is as complete a jumble of 
confused tables as if Titans had been emptying rub- 
bish carts of marble upon the floes. Sometimes they 
are so crumbled by the excessive action, that they look 
like crushed sugar ; and, again, I have seen neatly- 
squared blocks piled regularly one above the other in 
a Cyclopean wall. 
These pressures sometimes develop grotesque and 
singular forms. One of the most simple, an arch of 
ice four feet in thickness, bridging a fissure, is pictured 
literally in a former chapter. My friend, Mr. Mur- 
daugh, pointed out to me two narrow tables forming 
