456 /. HARLEN BRETZ 



A swamp at the col drains both north and south. Within two miles 

 of Puget Sound drainage from this swamp flows south to the Chehalis 

 River and thence to the Pacific Ocean, 50 miles distant. 



The narrowest place in the channel of the glacial stream which 

 discharged over the divide is close to its inception, about ij miles 

 from Budd's Inlet. Here the width of the 120-foot channel is less 

 than one-fourth of a mile. This is cut in the bed of a considerably 

 wider channel, whose floor is 160 feet A.T. A definite terrace 

 occurs here, and also in the swamp a mile distant at 140 feet. These 

 three levels are seen repeatedly in the 17 miles of channel length, 

 though their altitude descends and their distinctness is less marked 

 farther south. The ancient outlet today contains Percival Creek 

 north of the col, and Black Lake and Black River south of it. 



At Gate, the Black Lake outlet channel joins the wide Chehalis 

 Valley. At the debouchure occurs a considerable area of gravel 

 spreading out into the larger valley from the north. The deposit 

 presents a rather abrupt face down the valley. Its surface altitude 

 is approximately 100 feet above sea-level. Farther down the Che- 

 halis Valley, glacial gravels occur only at the mouths of tributary 

 valleys from the north, none being found in a careful search for 

 five miles immediately below Gate. 



The genesis of the Gate gravels is evidently associated with the 

 operation of the Black Lake outlet and their deposit here suggests 

 slack water in the Chehalis Valley, standing at an altitude at Gate 

 of about 100 feet. 



The suggestion of standing water at Gate and in the Chehalis 

 Valley, much beyond the limits of glaciation, and so topographically 

 placed that ice could not close it if it were glaciated, turns one to a 

 consideration of the sea -level at the time of Vashon glaciation and 

 retreat. 



In the study of the physiography of Puget Sound, various shell- 

 bearing terrace fragments have been observed. Willis notes the 

 occurrence of the lowest, 15-20 feet above present mean tide,' and 

 Arnold has recorded one 40 feet above sea-level on the west side of 

 the Olympic Mountains.^ Terraces at both of these levels have 



1 Bailey Willis and G. O. Smith, op. cit. 



2 Ralph Arnold, "Geological Reconnaissance of the Olympic Peninsula," Bull. 

 Geol. Soc. Am., XVII. 



