GLACIERS AND ICEBERGS. 73 



1. Glaciers heap up their debris in abrupt ridges. Floating ice 

 sometimes docs this, but more usually spreads its load in a more or 

 less uniform sheet. 



2. The material of moraines is all local. Icebergs carry their 

 deposits often to great distances from their sources. 



3. The stones carried by glaciers are mostly angular, except where 

 they have been acted on by torrents. Those moved by floating ice 

 are more often rounded, being acted on by the waves and by the 

 abrading action of sand drifted by currents. 



4. In the marine glacial deposits mud is mixed Avith stones and 

 boulders. In the case of land glaciers most of this mud is carried oflf 

 by streams and deposited elsewhere. 



5. The deposits of floating ice may contain marine shells. Those 

 of glaciers cannot, except where, as in Greenland and Spitzbergen, 

 glaciers push their moraines out into the sea. 



6. It is of the nature of glaciers to flow in the deepest ravines they 

 can find, and such ravines drain the ice of extensive areas of mountain 

 land. Icebergs, on the contrary, act with greatest ease on flat surfaces 

 or slight elevations in the sea bottom. 



7. Glaciers must descend slopes and must be backed by large 

 supplies of perennial suoav. Icebergs act independently, and, being 

 water-borne, may woi-k up slopes and on level surfaces. 



8. Glaciers striate the sides and bottoms of their ravines very im- 

 equally, acting with great force and effect only on those places where 

 their weight impinges most heavily. Icebergs, on the contrary, being 

 carried by constant currents and over comparatively flat surfaces, 

 must striate and grind more regularly over large areas, and with less 

 reference to local inequalities of surface. 



9. The direction of the strire and grooves produced by glaciers 

 depends on the direction of valleys. That of icebergs, on the con- 

 trary, depends upon the direction of marine currents, which is not 

 determined by the outline of the surface, but is influenced by the 

 large and wide depressions of the sea-bottom. 



10. When subsidence of the land is in progress, floating ice may 

 carry boulders from lower to higher levels. Glaciers cannot do this 

 under any circumstances, though in their progress they may leave 

 blocks perched on the tops of peaks and ridges. 



The only portion of Acadia in which stratified clays holding marine 

 shells have been found overlying the boulder clay, or in connexion 

 with it, is in the southern part of New Brunswick, where deposits of 

 this kind occur similar to those found in Canada and in Maine, though 

 apparently on a smaller scale. These deposits, as they occur near St 



