396 Prof, Bischoff on the Temperature of 



and five days were made in shallower places. The greatest excess 

 of the mean temperature of the air over that of the sea in those 

 seventeen days was, however, only 1°.3 ; whilst, on the other 

 hand, the greatest excess of the mean temperature of the sea over 

 that of the atmosphere, in the 128 days, amounted to 7°.87. 

 Had Dr J. Davy added the depth of the sea, which however 

 would have been attended with many inconveniences to his 

 numerous and valuable observations, it might have been decided 

 with certainty, whether the excess of the mean temperature of 

 the sea over that of the atmosphere, becomes really greater in 

 proportion as the depth increases, and vice versa, whether the 

 hypothesis that the mean temperature of the sea in shallows is 

 lower than that of the air, has any foundation. If we take the 

 mean of the thermometrical observations in the sea and in the 

 atmosphere, between latitudes 5° N. and 5° S., we find for the 

 former 79°.607, and for the latter 78°. 226, making a difference 

 here also in favour of the former, of 1°.454. 



The above observations include the latter half of the winter 

 and a part of the summer in the northern atmosphere, and the 

 whole autumn with the first half of the winter in the southern 

 hemisphere, comprising more of the cold than of the warm sea- 

 sons. However, if we only take the average of the summer ob- 

 servations in the northern hemisphere, from the 1st to the 12th 

 of August, we find the mean temperature for the sea 79°.953 ; 

 for the air 780.353, which even thus gives a difference of 1°.575- 

 The higher mean temperature of the sea as compared with that 

 of the air, seems, therefore, to be by no means confined to the 

 cold season. 



Should the water of the sea reach its maximum of density at 

 a certain low degree of temperature, the circumstances would be 

 similar to those above developed relative to lakes in elevated 

 situations. Namely, in high latitudes, where the temperature 

 of the bottom of the sea would be as low as that corresponding 

 to the maximum of density of the sea-water, the sea would 

 neither impart heat to, nor receive heat from, the bottom. In 

 such places there could consequently be no ascending current 

 of water. 



If iho sea was a motionless mass of water, its temperature in 



