Lake and River Temperatures. 17 
presented a comparatively unrufiled surface, which favored 
the taking of temperatures. 
In a shallow river like the Yamaska, whose waters are 
readily swollen by very heavy rains, and whose course is 
broken here and there by milldams, the temperature of the 
water is necessarily somewhat uniform, excepting so far as 
the surface may be influenced by the sun’s rays by day or 
by the coolness of the night air. Thus, on days when the 
sky was continuously overcast, this uniformity was fre- 
quently observable, whilst in the bright sunshine of early 
August, the surface would indicate from 1° to 2° higher 
than at about four feet depth. The general temperature of 
the water at that depth in the earlier part of the month 
was about 77°, but by September 8th it had fallen gradually 
to 68°. ’ 
INFLUENCE OF TEMPERATURE OF WATER ON THE IMME- 
DIATELY OVERLYING AIR. 
The temperature of the river water was about 6° to 7° 
higher than Lake Ontario waters at about the same depth 
and the same period in August would be, but the protection 
which the river banks: afforded from the wind, and the, at 
oft times, comparatively unruffied surface, aided in render- 
ing the tests made here more definite than, on the open 
lake, they could generally have been. The readings were 
taken (1) at one inch below the surface of the water, (2) in 
the air one inch above the surface, (8) at one foot and one 
foot and a-half above the surface, and (4) on the top of the 
bank at about sixteen feet above the river level. Cloudy 
days were selected, though some tests were made at sunset. 
The features of interest which from the first presented 
themselves were, as might be expected, the much higher 
temperature of the surface water over the immediately over- 
lying stratum of air, and the extreme variation in this dif 
ference of temperature. It was not uncommon to find this 
difference amounting to 6° @ 8°, although it sometimes was 
as low as half a degree, and on one occasion, at 7.45 p.m. 
on the 13th August, rose to nearly 18°, and was then accom- 
2 
