FINGER LAKES OF NEW YORK. 



213 



of maximum density for the depth. Hamberg (loc. cit.) quotes examples of similar 

 temperatures from Lakes Ladoga and Mjosen. It is worth noting that the temperature 

 in both these lakes at the depth of 190 m. was between 3.8 and 3.9°. The observations of 

 Huitfeld-Kaas (1905, p. 4) in Mjosen give temperatures at 200 m. which rise as high as 

 4.1° in November and as low as 3.65 or 3.75° in April and May. At the bottom, 400 

 m. or more, 3.60 and 3.75° were 

 found. At this depth the tempera- 

 ture of maximum density is slightly 

 above 3.3°. 



It is very probable that the 

 temperature of Seneca Lake, record- 

 ed in 19 10 as 4.2°, was really close to 

 4.0°, and that all readings of 4.0° at 

 the bottom indicate temperatures as 

 low as 3.8 or 3.9°. It is not worth 

 while, however, to apply an estimated 

 correction to these readings. There 

 is no reason to believe that the bot- 

 tom temperature of Cayuga Lake is 

 below 4.0° in late summer. 



THERMAL REGIONS. 



Table 2 shows the thermal 

 regions of the several lakes. The 

 epilimnion of Canandaigua Lake was 

 II or 12 m. thick; the thermocline 

 was 4 to 8 m. thick, averaging 6 m. 

 In Cayuga Lake the epilimnion was 

 13 to 15 m. thick and the thermocline 

 4 to 5 m. thick. 



There was more variation in 

 Seneca Lake. The epilimnion was 

 15 to 19 m. thick and the thermocline 

 4 to 6 m. On August i, 191 8, the 

 epilimnion at Hector Point was only 

 10 m. thick; on August 29, at Kashong, it was determined at 20 m. But since Kashong 

 is near the north end of the lake and the readings were taken on the day following a hard 

 south wind, the epilimnion was no doubt thicker there than observations at the center of 

 the lake would have shown. In computing gains of heat, therefore, the thickness of 

 the epilimnion for 1918 was taken as 15 m. 



On July 24, 1918, at the north end of the lake in 40 m. of water the epilimnion was 

 only 7 m. thick. This was at the end of nine days of hot and calm weather and is an 

 exceptional condition. The thickness of the epilimnion rapidly increased to 14 or 15 m. 

 in the course of the follomng week and was subject to considerable fluctuations. 



Fig. I. — Curves of mean temperature to 34 m. depth. .A , Canandaigua 

 Lake; B. Cayuga Lake; C. Seneca Lake. (See Table i, p. 212.) 



