lakEkS of the lahontan basin. 71 



in the study of the recent and fossil lakes of the Far West it is fre- 

 quently desirable to know the present rate of evajjoration, and the charac- 

 ter of the seasonal and secular variations in precipitation that are taking- 

 place. Attempts have been made to determine the rate of evaporation by 

 experimenting with artificial evaporating pans, but owing to the difficulty 

 of imitating the conditions of nature, these observations have been of little 

 value. Gauges have been established in Great Salt Lake, and accurate 

 records of its annual and secular fluctuations have been secured for a num- 

 ber of years, but in this instance the variations of the lake are influenced by 

 irrigation, and the sources of supply for the waters of the lake are too numer- 

 ous to be definitely measured. Of all the lakes of the Far West with whioli 

 we are acquainted, excepting Abert Lake, Oregon, the most favorable for 

 determining the questions indicated above is Walker Lake. As this lake 

 receives its entire supply from a single source and is without outlet, the rate 

 of evaporation from a large water surface could be determined with great 

 accuracy. Observations intended to show tlie secular variations in precip- 

 itation would be more difficult because the waters of Walker River are 

 largely used for irrigation. 



LAKE TAHOE. 



As Lake Tahoe is the grandest of the Sierra Nevada lakes, and the 

 largest that discharged into Lake Lahontan, we insert a brief account of it, 

 compiled principally from the investigations of Prof John Le Conte, of the 

 University of California.^^ 



The lake is situated in latitude 39° N., and lies part in California and 

 part in Nevada, at an elevation of 6,247 feet, as determined by railroad 

 surveys. Its drainage area, including the lake surface, is about 500 square 

 miles. The water surface is 21.6 miles long from north to south, with an 

 extreme breadth of 12 miles; its area being between 192 and 195 square 

 miles. Its outlet is the Truckee River, which leaves the lake through a 

 magnificent gorge, at a point on its northwestern shore. 



32 "Physical Studies of Lake Tahoe," published iu the Free Press and the Mining and Scientific 

 Press of San Francisco, during 1880 ajid 1881. Reprinted in the Overland Monthly for November and 

 Drcniilicr, 188), and .I:iini.ii.v, le84. 



