SALMON INVESTIGATIONS IN COLUMBIA RIVER BASIN IN 1896. 3 1 
from the shore a distance of 50 feet or more. The bottom here is very muddy aud 
covered with tule. The shore on this side of the lake is thickly strewn with logs, 
slabs, and small floating debris. Few rocks are noticeable, and none at any great 
distance from shore. 
The sandy and gravelly beaches referred to on the west side of the lake below 
Sand Point are usually narrow; only in one place observed is the beach over 10 feet 
wide; here the width from the water’s edge to the bluff is about 30 feet. The clear 
ground indicates a smooth bottom, but stumps of trees and broken limbs prevent 
seine collecting. These beaches are formed by wave action, the water having washed 
away the base of the bluffs, leaving a deposit of sand and gravel. In many places, 
particularly on the west side of the lake, bushes and small trees have taken root in the 
sand and gravel deposit. Only in a few instances does the sand and gravel formation 
extend any great distance below the water’s edge; 30 or 40 feet from the shore is soft 
muddy bottom. As is indicated by the high perpendicular bluffs, the beaches make oft’ 
at a sharp angle, deep water being found a short distance from the shore. As a 
whole, the shore of Lake Washington is not well adapted to collecting with a seine. 
Depth and character of bottom . — Soundings were taken at different times and in 
various parts of Lake Washington. It has a uniform depth in the center, ranging 
from 138 to 222 feet. The character of the bottom is generally muddy. Off' the mouth 
of Union Bay and near the boathouse at Madison street sandy bottom was found. Off 
and in the vicinity of Sand Point, 3£ miles farther north, the bottom is composed of 
sand and gravel. This kind of bottom does not extend very far from the shore, from 
500 to 800 feet being about the limit. For nearly 2 miles south of Sand Point there 
are a number of sandy places along the shore, mostly covered with an undergrowth 
of bushes. In all other parts of the lake examined the bottom is chiefly of soft mud. 
On the east side of the lake, south of Hunt Point, the water is quite deep close to 
the shore; this is also true of the west side, south of Sand Point, and in many other 
parts. A depth of from 500 to 1,800 feet was reported off the northern end of Mercer 
Island and in the vicinity of Hunt Point. Comparatively deep water was found off 
these points, as will be seen by referring to the map, but no such depths as had been 
reported. About 1 mile along the shore above Kirkland a plateau from 60 to 100 feet 
wide, covered with vegetation, makes off from the shore. The water varies in depth 
from 10 to 20 feet, but suddenly deepens into 60 and 70 feet when the edge is reached. 
Temperature of water . — It will be noticed in the table of temperatures that near 
the shore on the east side of Mercer Island the temperature of the water at the surface 
varies considerably from that taken a short distance toward the middle of the channel. 
A difference of 2J° is recorded, the bottom temperature in both soundings being the 
same. In no other part of the lake was such a marked difference found. Several 
tests of the water were made within a radius of 100 feet or more, all with the same 
result. A few hundred feet from this position, to the north, south, or east, 47° was 
found at the surface. It is said that thermal springs occur in this vicinity in a 
number of places. The temperature of the water at the bottom, however, does not 
indicate their presence. The lowest temperature found in the main body of the lake 
was 44£°, and the highest 48£° ; the first in depths of 180 and 190 feet. In Union Bay, 
in 14 feet of water, a temperature of 41° was recorded both at the surface and the 
bottom. This low temperature was due, no doubt, to the cold weather, which at this 
time was quite severe. At no other place was such a low temperature found. 
