158 



BULLETIN OF THE BUREAU OF FISHERIES. 



•I' ir 13° 15' 17' 



16 



Upper Lake. August 7. 1903 

 Lower Lake. August 7. 19Q3. 

 Fl<:. 5. 



Upper Lake. August 28. 7903. 

 Lower Lake. August 28. 1903. 

 Fio. B. 



Figures 5 and 6 arc coiiiparisoii.s of the temperature readings obtained for the 

 two lakes on August 7 and 28, 1903. During these three weeks the thermocline 

 moved down about 3 meters (10 feet) in each lake. Both summers the temperature 

 of Lower Lake throughout its entire depth was somewhat higher than that of Upper 

 Lake. This condition may be attributed to the following factors: 



By far the greater part of the water which flows into Lower Lake during the 

 summer comes from Upper Lake and thus has about the same temperature as the 

 surface of the latter. The water flowing into Upper Lake, however, through all 

 except one of its atfluents was found to be 3*- to 4 C. colder than the water above 

 the thermocline. In l!t03, for instance, the temperature of the water in Lake Creek, 

 which is the chief affluent of Upper Lake, was 13.6° C. (56..5° F.) on August 7 and 

 11.2" C. (.52.2- F.) on August 28. On these dates the surface temperatures of Upper 

 Lake were, respectively, 10.1= C. (61- F.) and 15.4"- C. (59.7' F.). On August 7 the 



