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171   COMMISSION OF CONSERVATION

ravines have been worn by ice and water action. The result is a topography of low rounded ridges and depressions. The monotony of this plain is relieved by a few granite hills, rising from 100 feet to 150 feet above the general level. The highest of these hills lies half way between Clear lake and Bass lake. Another stands about a mile southeast of Sandy lake. Kasshabog lake, on the southern side, is hemmed in by a high granite ridge, which increases in elevation in going westward. The eastern and south-eastern margins of the granite outcrop are bordered by amphibolite rock, whose ridges are, for the most part, higher and sharper, and, as there are more of them, their topography is much rougher than that of the granitic areas. At Oak Lake and Van Sickle settlements there are two detached plateaus of sedimentary limestone of Trenton age.

The depressions between the ridges are a very noticeable phase of the topography. They are abundant in both townships, but are more abundant in Methuen. At least one-quarter of the region is occupied by these depressions, and they vary from a few yards to a thousand yards across. Some of them may be traced continuously for several miles and are evidently former stream channels; others are the bottoms of former small lakes and ponds.

The soil on the crests of the ridges is very thin, and

Rapid Erosion often entirely lacking, although there are crevices and of the Soil

pockets on most of them with soil deep enough for

scattered tree growth. In studying the conditions on these ridges, one cannot but be convinced that the soil was, at one time, much more generally distributed and deeper than at present. One frequently finds stumps of trees from one foot to two feet in diameter on bare rock, in such a position that the roots could not have penetrated crevices. The trees could not have germinated and lived for many years on bare rock. Then, too, trees still standing on bare rock are held up by roots extending into crevices several feet from the base of the tree. There must have been soil at the base of the trees when they started in life. One needs only to note, after a heavy rain, the accumulations of soil washed down from above, to be impressed by the rapidity of the soil-erosion on these ridges. The soil-washing is the result of the repeated fires, which kill and loosen the natural retainers, the roots of the trees and shrubs, and the decaying vegetable matter.

The soil on the lower slopes and about the bases of the granite ridges varies in composition from gravel to sand, not uniformly distributed, but in alternate deep and shallow patches, owing to the minor undulations in the topography. The wider depressions between the ridges are often filled with sand to the depth of many feet, and there-


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