TERMINAL MORAINE OF PUGET SOUND GLACIER 171 



out wash gravels begin, continuing to Shelton in one direction and 

 across the Puget Sound divide to the Satsop in another. In this 

 latter direction, the outwash largely buries the moraine near Mat- 

 lock and becomes extra-morainic in its further extent. 



On the east side of Lake Cushman, the till plateau becomes 

 ridged and kettley, though a dense forest prevents satisfactory 

 examination. The morainic character is best seen along the trail 

 from the head of the lake to Lilliwaup. The material on the lake- 

 ward face of these ridged drift hills nowhere contains granite, though 

 two very careful examinations were made. In but one place are 

 granite pebbles found on the shore or in the immediate vicinity 

 of the lake, this being in the bed and delta of the largest stream 

 entering the lake from the northeast. Yet a mile back from the 

 lake, to the east, granite bowlders are found lying on the surface, 

 becoming very numerous two or three miles farther east. 



The limit of the Puget Sound drift is thus seen to lie close to 

 the lower end of Lake Cushman, the basin of which is caused by 

 the damming of the Skokomish River valley. The inner slope of 

 the drift dam is probably faced with the terminal deposits of the 

 Skokomish valley glacier, which was unable to advance farther 

 in the face of the overwhelming mass of the Vashon glacier. It 

 may have earlier deployed farther out on the plain, but if so the 

 deposits are buried beneath the Vashon drift. That a valley 

 glacier must have existed back of the drift dam of Lake Cushman 

 when the Puget Sound ice was at its maximum is evident, else the 

 lake basin would have filled with outwash. A till with very 

 angular debris, none characteristic of Puget Sound drift, lies back 

 of the drift dam on the slope of Mt. Ellinor, immediately north of 

 the lake. It is estimated to reach 500 feet higher than the lake 

 surface. 



As shown on the map, the western margin of the Puget Sound 

 glacier north of Lake Cushman is approximate only. The moun- 

 tains rise close to Hood's Canal throughout the remaining distance 

 included in the accompanying map, and in all probability there 

 existed no embayment of Puget Sound ice in the other river 

 valleys entering the Canal comparable to that of the Skokomish 

 valley. 



