Ragnarok : the age of fire and gravel

20 THE DRIFT,

progress and retreat, of glaciers in former times. Suppose, for instance, that a glacier were to disappear entirely. For ages it has been a gigantic ice-raft, receiving all sorts of materials on its surface as it traveled onward, and bearing them along with it ; while the hard particles of rocks set in its lower surface have been polishing and fashioning the whole surface over which it extended. As it now melts it drops its various burdens to the ground ; bowlders are the milestones marking the different stages of its journey ; the terminal and lateral moraines are the frame-work which it erected around itself as if moved forward, and which define its boundaries centuries aiter it has yanishe.” *

Terminal Morarne.

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And Professor Agassiz gives us, on page 307 of the same work, the above representation of a “terminal moraine.” he reader can see at once that these semicircular

wane Geological Sketches,” p. 30S.