76 GLACIAL GEAVELS OF MAINE. 



and this over an exposure 40 feet long and 6 feet higli. A small brook 

 flows northward into the lake at this point, but it is only about 1 mile in 

 length, and could never carry much sediment into the lake ; still less could 

 it give its sediments a southward dip. The gravel on the beach of the 

 lake, as well as the small amount of gravel brought down by this brook, 

 has very nearly the till shape, and is nowhere well rounded like the gravel 

 of the two-sided ridge at the foot of the lake. It thus becomes evident 

 that this ridge is the osar. A short distance south of the foot of the lake 

 the ridge becomes low, and the stratified sand and gravel are almost 

 covered from sight by a pellmell mass resembling a stony till containing 

 numerous till bowlders. But for road excavations one would hardly sus- 

 pect the existence of this hidden gravel. 



This till-like mass might be accounted for in several ways. (1) It 

 might be due to a landslide; but I could discover no place bare of till, or 

 any other sign of a landslip, at least on the lower slopes of the hills. 



(2) It might be due to ice floes stranded at a time when the lake stood 

 about 10 or 15 feet higher than at present. Nowhere else on the shore of 

 the lake did I discover such proofs of the water having stood at a higher 

 level. It must be admitted, however, that the shape of the Arm of the 

 Lake is very well adapted to cause a convergence of floes to this place. 



(3) The till may have tumbled down upon the sediment of the glacial 

 stream, either into a subglacial tunnel or from the sides into a superficial 

 channel. 



My brief ^-isit did not permit me to explore the shore of the lake very 

 far. The gravel ridge becomes less conspicuous as we go southward from 

 the lake, and disappears within tlu-ee-fou.rths of a mile, at an elevation of 

 not more than 30 feet above the lake. The ground continues to rise very 

 gently for somewhat more than a mile, and then slopes southward down the 

 valley of the east branch of the Tomah Stream. The highest part of this 

 divide is hardly more than 50 feet higher than the lake. It is certain that 

 an osar stream flowed southward from the Arm of Grand Lake through 

 this very low pass, where it was for 2 miles or more hemmed in by high 

 hills on each side. But the gravel is rather fine and the ridge is not large. 

 This indicates a stream of moderate velocity and size. The course of this 

 stream must have been somewhere to the south or southeast. Its most 

 nattu-al route lay down the valley of the east branch of Tomah Stream, 



