124 
IOWA ACADEMY OF SCIENCE 
of the lake is about two square miles. From the power house, about 
three miles below the lake, to the intake, ten miles down stream, the 
river falls 35 to 40 feet per mile. Its principal tributary is Taylor 
Creek, flowing into the river near Barneston, and contributing 
about 20 per cent of the entire flow at that point. Other smaller 
creeks and large springs swell the volume flowing during the low 
water season from 30 cubic feet per second at the power house to 
160 cubic feet per second at the intake — a volume sufficient to supply 
1,000,000 people if taken direct from the running stream, and suf- 
ficient for three or four million people if the total capacity of the 
water shed could be stored. Its purity at the present time is almost 
unquestioned. The entire water shed was heavily timbered until 
certain portions were logged off and burned over. The city of 
Seattle has acquired about 11,000 acres contiguous to the river and 
lake shores in order to the better protect her interests in this source 
of supply. 
“The major portion of the valley from power house to intake is of 
glacial drift: boulders, gravel and sand, interspersed with beds 
of clay and strata of cement gravel and hard-pan. Occasional dikes 
of trap and porphyry have intruded, and in the lower part of the 
valley broken blocks of basalt lie en masse.” 
Originally, the region was heavily timbered, but from a portion of 
the water shed, the timber has been removed. Logging roads have 
been constructed through the region. In regard to the nature of 
the material from which the railroad passes, the following report 
was made by Professors Abbott, Sedgwick and Harrington: 
“It appears that along much of the proposed location, gravel and 
sand are not to be found. The forest floor appears to be reasonably 
thick, but at most points it consists almost wholly of combustible 
matter ; and where fires have occurred the soil is shown to be chiefly 
loose rock, with neither sand nor gravel, and consequently not 
porous and suitable for effective filtration. At some points along 
the route clay and silt deposits are evident ; but these materials are 
not suitable filtering media, for they do not permit percolation. In 
view of these facts, special provision will be necessary for proper 
disposal of such waste matters as may find their way to the surface 
of the ground within and near the limits of the right-of-way during 
construction and operation of the road ; for without such provisions, 
the said wastes would inevitably be washed into the river in times 
of heavy rainfall,, and, in the event of their containing pathogenic 
organisms, might lead to disastrous outbreaks of infective diseases. 
The fact is, however, that the character of the water can be ade- 
