62 Discovery of Stone Implements in [January, 
district, on the contrary, the decomposed crust has been 
removed, and the hard unaltered rock laid bare. 
It has been shown that the decomposition of the rocks 
has been caused by the slow percolation of rain-water con- 
taining a little carbonic acid. It follows that the surface 
rocks had been exposed for long ages to this influence, and 
that the time that those of the glaciated districts have been 
subjected to the same aCtion, since the Glacial period, is 
exceedingly short in comparison. 
Another mark by which the glaciated may be distinguished 
from the non-glaciated country is by the occurrence of a 
deposit long known in Scotland under the name of “ till,” 
and on the Continent as “ grund morane ” and “ moraine 
profonde.” It is generally a stiff clay, full of small angular 
fragments of the rocks over which the ice has passed, and 
sometimes with large angular and subangular stones. It 
always more or less reflects the characteristics of the strata 
immediately in the neighbourhood and in the direction from 
which the ice has come. Thus in the vicinity of Toronto I 
noticed, as Mr. G. J. Hinde had before remarked,* that the 
till is packed with small fragments of black Utica shale and 
blue Trenton limestone — strata that the ice had passed over 
in its passage from the eastward. Along with these were 
larger fragments and slabs of the underlying Hudson River 
group, and a few rounded boulders of gneiss that were far 
travelled. Around New York many patches of till are left 
on the glaciated rocks. I visited Marion, near the city of 
New Jersey, by the advice of Prof. Cook, and found very 
fine sections of the glacial beds. The till is there not a 
stiff clay, but a rather sandy deposit, of a dark reddish 
brown colour, packed with the angular debris of the red tri- 
assic sandstones that form a large portion of the bed-rocks 
of eastern New Jersey. A few of the contained stones may 
have been brought from a distance, but the great bulk of 
them, as well as the sandy matrix, are of local origin. 
The deposition of the till probably took place during the 
melting back of the ice-sheet. Dr. Dana has shown that 
the ice was very thick over New England, and that the 
pressure at its base would be so great as to force the plastic 
mass into the crevices of the rocks below, so as to tear off 
fragments from them, which, with any loose material it met 
with in its progress, would be gathered up and borne along 
in the lower portion of the ice-sheet, t Prof. Joseph Le Conte, 
* Canadian Journal, April, 1877, p. 8. 
f “ On the Glacial and Champlain Eras in New England.” Amer. Journ. 
Sci., March, 1873. 
