NORTHWESTERN LAKES OF THE UNITED STATES. 
71 
Table 2. — Elevation of certain laices and per cent of sea-level saturation of dissolved oxygen. 
Lake. 
Eleva- 
tion. 
Sea-level 
satura- 
tion. 
Lake. 
Eleva- 
tion. 
Sea-level 
satura- 
tion. 
Bear 
Meters. 
1,806 
Per cent. 
79.8 
Hayden 
Henry 
Payette 
Pend Oreille 
Meters. 
683 
Per cent. 
92 
79 
1,961 
1,520 
625 
78 
Coeur d'Alene 
’647 
92.3 
82 
Chelan 
96 
92.5 
Crescent 
204 
97.4 
Tahoe 
1,897 
78.6 
Fallen Leaf 
1,939 
78.9 
CARBON DIOXIDE CONTENT. 
Since the fixed carbon dioxide of these lake waters is largely combined with 
calcium and magnesium, the amount present shows the relative hardness of the 
water. 
In studying the Wisconsin lakes, Birge and Juday (1911) divided the lakes 
into three classes on the basis of the fixed carbon dioxide content. Those lakes 
containing less than 5 cc. per liter are classed as soft, those containing from 5 to 
22 cc. per liter as medium, and those above 22 cc. as hard. For the sake of com- 
parisons the same divisions will be used here. 
In the soft-water group there are 21 lakes. Western Washington has 11, includ- 
ing Martha and Ki, which are the softest, with 1.26 cc. per liter. Eastern Wash- 
ington has 9. Fallen Leaf, of California, also belongs in this class. 
In the class of medium-hard water, varying from 5 to 22 cc. per liter, there are 
24 lakes. Eastern Washington and Idaho have 8, western Washington 13. Tahoe, 
Crater, and Klamath lakes also belong in this class. Of these 24 lakes 17 have 
less than 10 cc., leaving 7 that range from 10 to 17.4 cc. 
In the hard-water class, containing more than 22 cc. per liter, there are 8 lakes, 
all in eastern Washington and Idaho. Four of these contain from 22 to 29 cc. 
and are similar to the hard-water lakes of southeastern Wisconsin, which reach a 
maximum of about 50 cc. per liter. Silver and Clear Lakes have about 75 cc.; 
Bear, 130.4; and Medical, 478.6. It should be noted that Silver and Clear were 
reported as excellent bass lakes. Bear Lake furnishes a large number of trout to 
the market fishermen, but they are not caught by angling. The shallow north 
end was reported as offering good bass fishing. Medical Lake was reported as con- 
taining no fish. 
The complete analysis of Bear Lake water (p. 64) shows 37 times as much 
magnesium as calcium present, although in most lakes there is more calcium than 
magnesium. This may be explained by the strongly alkaline water, which precipi- 
tates calcium more readily than magnesium. 
The presence of 0.65 part per million of zinc is also interesting. When this is 
compared with the small amount of copper necessary to stop the growth of algae, it 
seems that this quantity of zinc would have a similar effect. Since the low tempera- 
ture and short summer season would also retard the growth of algae, no definite 
conclusions can be drawn. 
It may be assumed that the half-bound carbon dioxide is equal to the fixed 
in all waters that are neutral or acid to phenolphthalein, and in water that is alka- 
