68 
BULLETIN OF THE BUREAU OF FISHERIES. 
near the surface, which is accounted for by several hot, calm days previous to time 
of taking temperatures. This also shows slightly in the dissolved gases, but all 
of the conditions near the bottom prove that the whole body of water had been 
circulated. The oxygen content of these lakes is near the saturation point. In no 
case did we find marked supersaturation near the surface. In Liberty, Upper Twin, 
and Steilacoom there is less oxygen at the bottom, and the free carbon dioxide 
increases there, thus showing the results of decomposition and respiration. Henry 
Lake has a lower surface temperature, which would increase the solubility of oxygen, 
but the altitude decreases the solubility in about the same proportion, so that the 
average amount of oxygen, 5.2 cc. per liter, is 97.5 per cent of saturation at that 
altitude. 
Most of the lakes investigated fall into Group II, division 1; that is, those 
having a definite thermocline and oxygen present in the bottom water during the 
whole of the summer. This series includes the following lakes, arranged according 
to depth: 
Crater. 
Coeur d ’Alene. 
Sammamish. 
Tahoe. 
Stevens. 
Williams. 
Chelan. 
Clear. 
Silver. 
Pend Oreille. 
Loon. 
Chaplain. 
Crescent. 
Upper Priest. 
Calvert. 
Priest. 
Sutherland. 
Padden. 
Fallen Leaf. 
Spirit. 
Martha. 
Whatcom. 
Deer. 
Newman. 
Sullivan. 
Swan. 
Cottage. 
Payette. 
Samish. 
Goodwin. 
Hayden. 
Ki. 
Spanaway. 
Bear. 
Lower Twin. 
The first four lakes in this list are the deepest known lakes in the United States. 
Crater is 608 m. deep; Tahoe, 516; Chelan, 458; and Pend Oreille, 371. We hoped 
that these lakes would furnish some new gas and thermal conditions. Excepting 
the minimum temperature of Crater Lake (see p. 107) the conditions in these deep 
lakes are very similar to those found in Crescent, Priest, Fallen Leaf, Whatcom, 
Sullivan, and Bear Lakes. All of these lakes, except Bear, are over 95 m. deep. 
The fact that they all have more dissolved oxygen at the bottom than at the surface 
differentiates them from the rest of the series. This is easily accounted for by the 
immense volume of water in the hypolimnion and the low temperature, which tends 
to retard decomposition at or near the bottom. Therefore, the oxygen which the 
water dissolved during the vernal overturn is very largely retained throughout the 
summer. 
Most of the very deep lakes do not freeze during the winter. This is accounted 
for by the large volume of water that must.be cooled to approximately 1° C. before 
the surface will freeze. No data are at hand regarding the winter temperatures of 
these lakes. When a lake does not freeze, circulation continues through the winter, 
and the water probably reaches a temperature near freezing, except in mild climates. 
Crater Lake, which is reported as not freezing, is the most striking example. 
With a summer surface temperature of approximately 12° C. and with 500 m. of 
its 608 m. of depth with temperatures between 3.5° and 4°, it must be cooled to 
