68 FISHES OF THE CONNECTICUT LAKES. 



probably due to the fact that the ])ixy has ahiiost no tributaries and 

 is out of the direct currents entering and leaving the lake, while the 

 prevailing winds drive no cooler water into the bay. Its tempera- 

 ture together with its greater amount of fixed aquatics would indi- 

 ate a plankton of somewhat different character and quantity from the 

 rest of the lake. Some of the shallower coves, exposed to the sun, 

 registered as high as 80° F, on this same day. The surface tem- 

 l^erature held with but slight lowering to a depth of 15 feet, but 

 deeper in the later and colder part of the season. At 20 feet the 

 temperature approximated 65° F. and at 30 feet 51° F. The ther- 

 mocline lay at about 25 feet, but was not confined to a thin stratum 

 of water. From day to day, and in different parts of the lake, the 

 thermocline was found at different levels. The changes seem to be 

 most closely related to the piling up of the w^armer surface water 

 under pressure of the wind and a somewhat tardy lowering of the 

 thermocline in the lee portions of the lake. From the 30-foot level 

 the water temperature decreased uniformly to a temperature of 46° 

 F. at 60 feet, which was maintained practically to the maximum depth 

 of 140 feet. 



Te?nperatu7'e of air. — The temperature of the air shows a mean 

 much below that of the surface of the water. The mean temperature 

 of the air for July was 63.5° F., and for August 57° F., while the 

 average of the surface temperature during these months was 68.4° F. 

 and 67° F., respectively. The night temperatures show an average 

 minimum of 18.7° F. below the average for the surface for the period 

 from July 22 to September 1, and an average of the daily maxima 

 5.1° F. above the average surface temperature. 



The prevailing winds were from the west and south, the former 

 bringing fair weather and the latter clouds and rain. There was no 

 protection in these directions, and the shape of the lake permitted a 

 sweep of wind through one of the long axes at all times. The wind 

 was as a rule very regular and brisk during the day, but quieting over 

 night when from the west. The usual day breeze was 10 miles an 

 hour. During the month of August a slight drift of wind came at 

 night from the northeast, but it did not seem to affect the water 

 appreciably. 



The usual day breeze of 10 miles an hour caused waves to run 1 

 foot or more high and to form slight combs. From July 1 to Sep- 

 tember 1 the waves were rough, breaking into white caps on 24 days 

 and continuing rough on 14 nights. Smooth water or waves of mod- 

 crate height, not breaking into white caps, occurred during 38 days. 

 On 28 nights the water was relatively smooth, and on 20 occa- 

 sions the water became rough during the night. In the appended 

 table of meteorological observations but three grades of agitation of 

 surface are recorded. Under " smooth " are included all glassv sur- 



