274 SABLE ISLAND—MACDONALD. 
upon by the passage uf innumerable icebergs, the clay, sand and 
gravel of the drift were deposited and occasionally the frag- 
ments of rock, both large and small, that had been frozen into 
the glacier or taken up by current ice, were strewn at random over 
the bottom of the ocean wherever they happened to be detached 
from the frozen ice. 
Finally a period of re-elevation, or that intermittent upward 
movement in which the old coast lines were excavated and the 
ancient sand bars laid down. 
This process continued for an unlimited period, which has’ 
been considered to be quite sufficient to account for all the pheno- 
mena observed. 
The second theory is one advanced by Agassiz and adopted by 
a large majority of geologists who have interpreted the glacial 
period as being one in which those forces acted on a much 
grander scale, which has been so graphically described by Dana, 
Belt and others. As a time when from the then elevated frozen 
regions of the Arctic an enormous ice-cap or glacier estimated to 
be from 4,000 to 6,000 feet in depth was forging its way south- 
ward across the northern portion of this continent with terrible 
abrading power, scooping out valleys, wearing the softer rocks 
into clay, tearing asunder the harder crags, grinding and polish- 
ing and grooving the sub-adjacent rocks, pushing before it and 
incorporating with itself great masses of rock, sand and gravel 
taken from the mountains over which it passed. At length it 
reached its culmination. The summit of Mount Washington 
stood out as a lonely island in a frozen sea, while to the north 
the whole continent was covered, not a single peak rising above 
the universal pall. 
Another period was ushered in by a milder climate known 
as the Champlain period. The glacier melted at first with 
extreme slowness, but when thawed down to about 500 or 1,000 
feet to where the gravel and stone were, it went forward rapidly 
and then took place a pell-mell dumping of this material over 
hill and valley, forming what is known as the glacial drift, of 
which the islands of our harbor are formed. 
At last, owing to the rapidity of the final melting, an immense 
