108 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



dred feet, measured from the bottom, have not been formed 

 in the same way as those which are broken off from an ice- 

 sheet one or two hundred feet thick, but that the glaciers 

 which originate the great icebergs have almost entirely the 

 character of the great glaciers that covered Norway during 

 the glacial epoch, and scraped out the fiords, and that, by 

 reason of their great dimensions, they must necessarily have 

 been shoved out under the surface of the sea. 7 C, 1874, 248. 



INFLUENCE OF OCEAN CURRENTS ON TEMPERATURE. 



Professor Mohn, of the Meteorological Observatory of 

 Christiania, has been paying much attention to the relation 

 between the temperature of the air and that of the ocean, 

 and also to the influence of the currents of the sea as affect- 

 ing the temperature of the sea-surface and that of the adja- 

 cent coasts. As a general rule, he finds that the water is 

 remarkably cold where there is a current running in a sound ; 

 but where there is a broader sheet of water, and where the 

 surface presents no trace of a current, the temperature is 

 higher. Also that the temperature is higher the deeper the 

 fiords penetrate into the land, or the farther from the open 

 sea the observation is made. 



The cause of this greater coolness of narrow surface cur- 

 rents is supposed to lie in the fact that in this case the water 

 wells up from the bottom so as continually to bring a fresh 

 exposure to the air, the bottom temperature, of course, being 

 much colder than that at the top. In certain instances, too, 

 the temperature as noted at the stern of a vessel was found 

 to be lower than that at the bow, in consequence of the stir- 

 ring up of the lower strata by the screw of the steamer from 

 which the observations were made. 



Although he has not had an opportunity of testing the 

 question by direct experiment, Professor Mohn is under the 

 impression that the temperature of the surface currents in 

 winter is warmer than that of quiet water, owing to the fact 

 that the stratum immediately in contact with the air is likely 

 to be cooled below the mean of the upper layers of water. 

 Compared with the temperature of the air, the water in sum- 

 mer, according to Professor Mohn, decreases at an average 

 of about one degree Fahrenheit for each increasing depth of 

 a fathom ; but in winter it increases only at an average of 



