Temperatures of Great Lakes and St. Lawrence. 85 



surface and at the bottom. On June 14th, at noon, when 

 the air indicated 79. 75° F., the surface water in the main 

 channel, two miles from Kingston, was still as low as 57.5° 

 F. or only 5° higher than on May 23rd. On July 5th, the 

 readings at the same place and hour had increased to 69.5° 

 F., with the air at 79°F, and on July 10th to 14.75° F., with 

 the air at 92.75° F., the thermometer being always in the 

 sun. The most marked change was between June 25th 

 and July 5th, when the advance registered was 9°. The 

 bottom temperatures indicated somewhat similar results. 

 On May 23, at 13 fathoms, the deep sea thermometer 

 registered 50.25° F. ; on June 14, at 12 fathoms, 52° F. , on 

 July 10, at 11 fathoms, 62.25° F., and in another spot in 17 

 fathoms, 53° F., and on July 25, at 12 fathoms, 67° F. 



The absorption and retention of the sun's heat is most 

 noticeable in the small streams and quiet pools. There we 

 find well illustrated the general proposition that in high 

 temperatures, the surface of comparatively still water, 

 where unaffected by under currents, absorbs and retains the 

 heat of the sun to a much greater degree than the immedi- 

 ately overlying air. A remarkable illustration has already 

 been given in the case of the lightly flowing but shallow 

 Wolfe Island stream, where the surface water was 7° higher 

 than the immediately overlying air, and 10° higher than 

 the air at 3 feet above, whilst on the bottom, at 7 inches in 

 depth, the temperature fell again to 10.5° below that of the 

 surface water. The records of other creeks did not indicate 

 such extremes, but showed that each stream in its bottom, 

 current and surroundings, may have circumstances which 

 vary the temperature. In very shallow, still pools, exposed 

 freely to the sun and breeze, but almost isolated from the 

 main stream, the difference between the temperature of the 

 surface of the water and of the immediately overlying 

 stratum of air, is, however, sometimes still more marked, 

 the water on sunny afternoons in June and July showing 

 over 11° higher range. In such pools, the water, though 

 indicating variation, is tolerably uniform even to the bottom. 



