Mesozoic and Ccenozoic Geology and Palaeontology. 211 



the current, oscillating slowly with the motion of the sea, and grind- 

 ing on the rocks and stone-covered bottom, at all depths, from the cen- 

 ter of the channel, we may form some conception of the effects of these 

 huge polishers of the sea floor. 



Of the bergs which pass outside of the straits, many ground on the 

 banks off Belle- Isle. Vaughan has seen a hundred large bergs 

 aground at one time on the banks, and they ground on various parts 

 of the banks of Newfoundland, and all along the coast of that island. 

 As thej' are borne by the deep seated cold current, and are scarcely at 

 all affected by the wind, they move somewhat uniformly, in a direction 

 from N. E. to S. W., and when they touch the bottom the striation or 

 grooving which they produce must be in that direction. 



In passing through the straits in July, we saw a great number of 

 bergs, some were low and flat topped with perpendicular sides, others 

 were concave or roof-shaped like great tents pitched on the sea ; others 

 were rounded in outline or rose into towers and pinnacles. Most of 

 them were of a pure dead white, like loaf sugar, shaded with pale 

 bluish green in the great rents and recent fractures. One of them 

 seemed as if it had grounded and then overturned, presenting a flat 

 and scored surface covered with sand and earthy matter. 



After describing the glaciers of Mont Blanc, he lays down the 

 following rules : * 



1. Glaciers heap up their debris in abrupt ridges. Floating 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 de- 

 posits 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 

 bowlders. In the case of land glaciers, most of this mud is carried off' 

 by streams, and deposited elsewhere. 



5. The deposits from floating ice ma}^ contain marine shells. Those 

 of glaciers can not, except where, as in Greenland and Spitzbergen, 

 glaciers push their moraines out into the sea. 



6. It is 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 sur- 

 faces, or slight elevations in the seat bottom. 



