NOTES ON LAKE TAHOE, ITS TROUT AND TROUT-FISHING. 



139 



than usual in June, 1904:, and was the highest since L861. Powell records a fluctua- 

 tion of 5.5 feet (1891, p. 171). 



Origin oftht lake. — In discussing the origin of Lake Tahoe, Le Conte states that 

 it is highly improbable that the basin was scooped out by glacial agencies; that, 

 rather, the lake was once wholly occupied by ice, a huge mer de glace. He is 

 inclined to the belief (1884, p. 45) that— 



* * * the small lakt-s near the southern and southwestern margin of Lake Tahoe are really 

 glacier-scooped rock basins, yet the position of the principal lake, countersunk between two ridges of 

 the Sierra Nevada, seems to render it probable that its basin may, in reality, be a "plication-hollow" 

 or a trough produced by the formation of two parallel mountain ridges and afterwards modified by 

 glacial agency that it is, in fact, a feature of mountain formation and not of glacial sculpture. 



Tenijx riihir,.— No attempt was made to obtain the temperature of the water at 

 any considerable depth; that is, beyond a depth of 425 feet. The following table 

 shows the results obtained by Le Conte (1883, p. 509) and those obtained in this 

 investigation: 



The letter B indicates bottom temperatures. Le ( 'unto states that he obtained the 

 same general results in all parts of the lake and thai his tabic is an abstract of his 

 average results. It will be noted that he obtained higher temperatures than those 



obtained by me. This may !»• accounted fur chiefly by the fad that hi- observations 

 were made between the 11th and L8th of August, or about the time the water had 

 reached its maximum temperature for the summer, while mine were made on -lime 

 27, or before the water of the lake had been exposed very long to the warming 

 influence of the summer's sun. The temperature of the water in three of the creek- 

 was as follows: Blackwood Creek, 50 F.: McKinney Creek, 46.5-; Taylor Creek, 

 55.75". 



There are some thermal springs at the northern end of the lake, one of which, at 

 Broekway, had a temperature of 130 F. The temperature of this water as it came 

 from the ground was probably somewhat higher, for this reading was made in a large 

 basin about 5 feet in diameter and several feet deep, and the warm water entered 

 the bottom of tin 1 basin. This thermal spring is one of the attractive features of the 

 resort, as its water is palatable and is also utilized for bathing purposes. Le ('onto 

 records a temperature of L31 F. for some id' these thermal springs. 



The temperature of the air probably remains several degrees below the freezing- 

 point for a considerable period of time each winter, yet ice never forms on the lake 

 except in shallow, detached bays. "The true explanation of the phenomenon may. 



