42 THE CANADIAN NATURALIST. [Feb. 



ice sometimes does 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 with stones 

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

 carried off by streams and deposited elsewhere. 



5. — The deposits from floating ice may contain marine shells. 

 Those of glaciers cannot, except where, as in Greenland and Spits- 

 bergen, 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 snow. Icebergs act independently, and being 

 water-borne may work up slopes and on level sufaces. 



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

 unequally, acting with great force and effect only on those places 

 where their weight impinges most heavily. Icebergs on the con- 

 trary 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 stria? and grooves produced by glaciers 

 depends on the direction of valleys. That of icebergs on the 

 contrary 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. 



I believe that in all these points of difference the boulder clay 

 and drift of Canada and other parts of North America, correspond 

 rather with the action of floating ice than of land ice. More 

 especially is this the case in the character of the striated surfaces, 

 the bedded distribution of the deposits, the transport of material 



