246 B. N. A. BOUNDARY COMMISSION, 
time when great nevées filled the heads of the valleys, and the mountains 
around them were completely snow-clad ; and are waiting only some 
change in the climatic conditions, to advance again down the lines of 
the old valleys, and occupy the places they formerly filled. 
General Composition of the Drift. 
570. In the subjoined table, the results of the numerical analyses of 
the drift, have been rearranged more broadly ; that a general idea of its 
composition may be arrived at. All clearly Laurentian material is 
classed under that name. In the limestone column, chert plainly derived 
from the same beds, has been included. It being impossible in all cases 
to separate the mountain drift from the Huronian, I have distinguished 
those figures in which any uncertainty of this kind may exist. It is pro- 
bable also that a small proportion of Huronian, the fragments of which 
have been included in the now preponderent Quartzite drift, runs on even 
as far as the Laurentian is found. The results here arranged, are founded 
on the travelled drift only, all local samples having been thrown out. The 
great mass too, of the lower and undisturbed drift, composed of soft 
matter mostly of local origin is, of course, here quite unrepresented ; as 
not throwing any light on the direction of travel. Crystalline quartz, 
diorite, &c., though appearing in the calculation, are not represented 
in the table, as their origin is more or less uncertain. . 
571. The limestone is all included in a single column, and has been 
almost altogether derived from the eastern limestone beds, though from 
No. 7, onward, fragments clearly referable to the mountains begin to ap- 
pear, and in some of the more western localities, material of the latter kind 
may amount to even fifty per cent. of the whole. The small quantity of 
limestone from the mountains compared with other rocks of this origin 
in the drift, except immediately on their flanks, is remarkable. The 
limestone beds, though forming so prominent a feature in the mountains, 
are, however, chiefly developed in the higher regions ; and it may be that 
the action of the waves was chiefly directed on the rocks of Series C., the 
general character of which closely resembles that of the quartzite drift, 
and which forms the lower and outer ranges. The eastern limestone, though 
from the same direction as the Laurentian debris, which appears at nearly 
the same percentage throughout; in constrast to it, runs out very rapidly 
toward the upper levels, a fact to be accounted for by its lower posi- 
tion on the flanks of the Laurentian highlands, and consequent rapid 
submergence below the line of efficient action of the ice. The constant per- 

