68 FISHES OF THE CONNECTICUT LAKES. 
probably due to the fact that the bay has almost 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- 
perature 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 warmer 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. 
Temperature 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 “fae 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- 
erate 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 glassy sur- 
