HULLETIN OF THE NATURAL HISTORY SOCIETY, 
of terminal moraines. Some of the points of the main shore are also 
rocky islands connected with the shore by bog. The greater abund- 
ance of islands and the greater shallowness of the water on the north- 
westeiTi side of the lake, and the greater depths of all of these lakes at 
their south-eastern angles, is no doubt correlated with the general 
south-easterly movement of the glacial ice, and is to be explained by 
the tendency of the drift to accumulate in the immediate lee of the 
bounding ridges or walls of the old valley. This entire lake is very 
typical of the sort formed by the partial filling rather than the damming 
of a valley by drift. Immediately to the southward of this lake rises 
Braithwaites Mountain, a fine mountain of some 500 to 600 feet above 
the lake. Off to the westward the edge of the great central pene- 
plain can be seen resembling a fiat-topped ridge, and to the north- 
eastward runs the ridge of Lyles Mountain, while, from some points, 
other hills are to be seen in the distance, including Cow Mountain, 
Big Bald, and others. These hill views give a considerable charm to 
the scenery of the lake. 
Jacks Lake, separated by a low ridge from Big Lake, is very 
shallow, and a typical mud lake, having almost no water, but much 
new bog at its upper end, where it is rapidly filling up. It is quite 
possible that the stream now emptying near its head into Big Lake 
was in pre-glacial times an inlet to it. 
The lake is held permanently some fifteen inches above its natural 
level by an old beaver dam. The organic mud must, therefore, have 
formed in the lake to the depth of over a foot since this dam was 
built ; and since its sticks are still undecayed, we have evidence that 
the formation of this mud can be comparatively rapid. On the north- 
east this lake is bounded by an abrupt ridge (Berton’s Ridge) some three 
liundred feet high which separates it from the’ Big Dead water. 
Holmes Lake is very pretty, the deepest of the group, and is not 
a mud lake. I do not understand at all the conditions which determine 
the formation of this organic mud* in some lakes and its absence 
from others apparently as favorable. Pocket and Jacks Lakes contain 
it abundantly, while Holmes does not, although the physical conditions 
appear to be about the same in both cases. Between Holmes and 
* The nature of this mud in our lakes is discussed in an earlier note [No. 17, Bulletin No 
17, 126]. Its presence does not appear to depend, as might be supposed, upon the al)senc© 
of lime from the water. 
