156 



BULLETIN OF THE BUREAU OF FISHERIES. 



In the accompanying- temperature curves the vertical spaces represent the depth 

 of the water in meters, and the horizontal spaces show the temperature iu degrees 

 centigrade. 



Upper Lake, 



July B. 1902 

 August 26. 1902 



Fig. l. 



12 



16 



18 



22 



2d 



8° 10' 12' 14" 



Upper Lake. 



July 14. 1903. 

 August 28. 1903. 



Fig 



Figures 1 and 2 indicate the temperature changes that occurred in Upper Lake 

 in 1902 and 1903 during the time of the observations. It will be noted that the 

 superthermocline was not so thick in 1903 as in 1902, but that the thermocline was 

 more sharply defined in the former year. In 1902 the upper 5 meters (16 feet) of 

 water reached the summer maximum of 16.6° C. (62^ F.) on August 4-, remained 

 practically the same for ten days, and then gradually decreased. In 11>(>3 a maximum 

 of 16.1 - C. (61^ F.) was noted on August 7. The bottom temperature was about the 

 same both summers and changed very little during the two months, averaging about 

 6.5- 0. (13.8° F.). 



