Drift near Seattle, Tacoina and Olympia. — Upham. 207 
is mostly sand in the lower j)arts of its deepest sections, but 
includes gravel beds nearly everywhere for the highest 5 to 
10 feet next to the surface, with rounded cobbles up to 6 to 8 
inches in diameter. Boulders are very rare or wholly absent. 
Only in one place on this hill was any till observed, that 
being- in a street cut on the northwest slope of the eastern sum- 
mit, about forty rods from the city w^ater works tower, which 
stands on the top of this east part. There, 25 to 30 feet below 
the top of the hill, a lenticular mass of true till, 30 feet long, 
with a maximum thickness of 5 feet, was seen inclosed in an 
exceptionally coarse gravel deposit, the till mass being 5 to 10 
feet below the original surface. All around it was very coarse 
gravel, in part showing a gradual transition, but mostly with 
a definite and abrupt line of separation. The explanation that 
seems most satisfactory would refer the modified drift of this 
large and high double-topi^ed hill to deposition under the edge 
of the departing ice, when it had become thin and drift-covered 
on account of its surface melting. Streams gathering the 
superglacial drift from parts of the icefields a little farther north 
probably poured down through crevasses near the ice front, 
amassing the great hill in a two-parted cavity melted beneath 
the ice. The deposition of the modified drift progressed as the 
subglacial cavity was melted and enlarged ; and the mass of 
till mentioned appears to have been derived from superglacial 
drift that was allowed to fall by the full melting of the ice be- 
neath it, without becoming modified by water assorting and 
stratification. 
Duwamish head, and the plateau extending from it south- 
ward, a mile wide between Elliott bay and the main sound, 
rising 250 to 300 feet above the sea level, reached by a ferry 
trip of two miles west from the docks of Seattle, are, in the 
lower 100 to 150 feet, horizontally bedded clay, or very fine 
silt, light gray and nearly uniform in color, mostly exhibiting 
very fine lamination, evidently laid down in still water. The 
next higher 100 feet, or more, are sand, yellowish gray, hori- 
zontally stratified in the lower part, but very irregularly bed- 
ded, with evidence of strong flow and counter currents of the 
depositing waters, in the upper part, where the sand be- 
comes coarser, with some layers of fine gravel. Above these 
verv thick stratified beds is a sandv till, with little or no strati- 
