;{18 The American Geologist. May, istt? 
elevation of 25 feet, as measured at the portage between the 
two lakes, has served to divert the whole discharge of the 
system along with the Cedar into the Duwamish. Evidence 
has been brought forward to show a general participation in 
such a recent elevation of all parts of the sound area which 
I have had an opportunity to study. The road bed of the 
northern division of the Seattle, Lake Shore and Eastern Rail- 
road, occupies a succession of drained lake basins, all of 
which were excavated from the drift mass. 
In order to take advantage of the slight differences of level 
between the upper and the lower parts of these fresh- water 
basins and tide water, a ship canal has been projected by the 
government to connect them with Puget sound,— namely, 
2,600 feet long, and 26 feet deep, through the portage between 
lakes Union and Washington, with a lock lift of 7^ feet.* 
The elevation of the several lakes above extreme low water 
in Puget sound is reported as follows: lake Union, 25.5 feet, 
(depth 60 feet) ; lake Washington, 33 feet, (depth 600 feet) ; 
lake Samamish 41.2 feet. The usual level of lake Union is 
7.8 feet higher than extreme high tide in its outlet (Salmon 
bay). 
It is unnecessary to instance the great number of examples, 
both on the Pacific and Atlantic coasts, of harbor formation 
at the mouths of rivers by subsidence of shore land — often 
to great depths, incidental to oscillations of level dining the 
Glacial and post-Glacial epochs. The most important havens 
on the Atlantic coast from New York to the Rio Grande owe 
their existence primarily to fluvial erosion, and in the higher 
latitudes in a secondary way to submergence, often followed 
by partial re-elevation. j- 
According to Davidson, as cited by Dana, the sub-marine 
river channels of California indicate submergence to depths 
* Report of Bd. of Engineers, etc., Ex. Doc. No. 40, 52d Cong. Ist 
Ses. 
Alternative routes coincident in alignment from lake Washington to 
Salmon bay have been surveyed — one connecting with the sound from 
the head of that bay, and thence through the estuary of Smith's cover: 
the other through the mouth of the bay. The two estuaries named are 
separated by a narrow divide, 2.5 feet above tide, a hight corresponding, 
it will be noticed, to the uniform measure of regional elevation as above 
indicated on both sides of the sound. (Ex. Doc, p. 6.) 
tShaler, Thirteenth An. Rep., U. S. G. S., pp. 109, 111. 
