INTRODUCTION. 609 



Also their direction both on the east and on the west of G-reen- 

 land is precisely the direction of the currents which may be re- 

 garded as the continuation of the Gulf Stream. 



From the evidence of Parry and others it appears that sounds 

 travel very long distances in the Arctic regions during winter, 

 when the atmosphere is no doubt very homogeneous ; it would be 

 interesting to test whether sounds can be heard equally and with 

 equal clearness over the same distance in opposite directions, or 

 whether at times sounds seem to travel farther in one direction 

 than in the opposite. 



Making allowance for the wind, the theory of Sound requires 

 that any sound shall travel with equal speed and equal intensity 

 between two points, whether it be going in one direction or in the 

 opposite. It may be expected that, in experiments over the ice- 

 floe, spaces of open water intervening will tend to deaden sounds 

 by producing changes of density of the atmosphere, even when to 

 the eye the atmosphere may be perfectly clear. That sounds are 

 sometimes deadened in a clear atmosphere is clearly shown by the 

 experiments of Dr. Tyndall in the English Channel, which also 

 show that even in a thick fog which light cannot penetrate sounds 

 may be distinctly heard for long distances ; under such circum- 

 stances the atmosphere may probably be regarded as consisting of 

 a homogeneous fog. The mists which sometimes prevail over 

 open water will probably afford opportunities for testing these 

 interesting questions. 



W. Gr. Adams. 



Physical Laboratory, King's College, 

 May 1875. 



The under-mentioned Physical Subjects are treated incidentally 



in Part I. 



1. J. Taylor. Temperature of the Kickertine Islands, in Cumber- 

 land Gulf (Inlet or Sound), Davis Strait, p. 243. 



2. P. C. Sutherland. (1.) Glacial Conditions and Temperature of 

 Davis' Strait, Baffin's Bay, and Barrow Strait, p. 356, (2.) Glaciers of 

 their Coasts, and Remarks on Ice, p. 358. (3.) Icebergs and Coast-ice, 

 p. 360. (4.) Polar Currents, and Specific Gravity of Sea-water, p. 363. 



3. D. Walker. Temperature of the Soil at Port Kennedy, Boothia, 

 p. 628. 



4. W. Flight. Aurorse, p. 4C5. 



36122. 



QQ 



