154 



BULLETIN OF THE BUREAU OF FISHERIES. 



The transparency of the water of the lakes was quickly affected by roily affluents. 

 If a heavy rain occurred in Lake Creek Canyon so as to fill the water of the creek 

 with silt, the water of the lakes soon responded with a marked decrease in trans- 

 parency. 



The maximum transparency of these lakes exceeds by 10 feet (3 meters) that 

 which the writer found in several lakes in southeastern Wisconsin in 1900, and it 

 also exceeds by 21 feet (6.5 meters) that found in Winona Lake, Indiana, in 1901. 

 These waters are not so transparent as Lake Tahoe, however. Le Conte (1883) 

 records that in August, 1873, he found that a white plate was still visible at a depth 

 of 108 feet (33 meters) in Lake Tahoe, and in June, 1901, the present writer found 

 the transparency to be 65 feet (19.8 meters). 



TEMPERATURE OF AIR AND WATER. 



The lakes are about 9,200 feet (2,804 meters) above sea level, consequently the 

 water does not attain a very high temperature during the summer because of the 

 climatic conditions at this altitude. In 1902 snow fell as late in the summer as July 

 5 and- as early in the fall as August 25. In 1903 two or three inches of snow fell on 

 June 10, and flurries were recorded for July 3. No snow was noted down as low as 

 the lakes until September 6, but some of the surrounding mountains were covered 

 as early as August 21. 



Some observations of the temperature of the air were made, but on account of 

 other work, they were not taken on some days; and it was found impracticable, also, to 

 make them each day at exactly the same hour. The average results, however, will 

 give a general idea of the daily range of temperature. The following table shows 

 the maxima, minima, and averages of readings taken between 6 and 7 a. m., 12 noon 

 and 1 p. m., 6 and 7 p. m. , and 9 and 10 p. m. 



The days are Usually warm and pleasant in summer, but the temperature falls 

 rather rapidly after sunset. The nights are very cool, generally, and hoar frost may 

 be expected every month of the year. 



These climatic conditions explain why the water of the lakes never attains a very 

 high temperature. In fact the lakes are generally covered with ice for a period of 

 a I ic nit five months each year. The following table shows the dates on which the lakes 

 became completely covered with ice early in the winter, and those on which it 

 disappeared from them in the spring, with a third column containing the number of 



