220 ACCOUNT OF THE AtlCTlC IIEGIONS. 



proceed to the other extremity, with a velocity pro- 

 portionate to the degree of tension. If, by put- 

 ting the thumb above the cord, and a finger below, 

 a small portion of it be made to assume the form 

 of the letter S, and then the hand be suddenly 

 withdrawn, a vibration of the very form produced 

 by the hand will proceed to the opposite end, and 

 from thence be reflected back, and then forward 

 again for several successive times ; and indeed, 

 whatever impression be made on the cord, if in the 

 form of two or three waves, the same will advance 

 from end to end, preserving continually the same 

 form. In this case, as well as in the case of waves, 

 though the cord has itself no progressive motion, 

 yet the undulations move with great freedom and 

 celerity ; not in proportion to their height, indeed, 

 but, what operates in the same way as gravity on 

 the water, namely, in proportion to the degree of 

 tension of the cord. In cords of different thicknesses, 

 with the same tension, the velocity of the vibra- 

 tion will of course be the greatest in the smallest 

 cords. 



As there is nothing very remarkable in the waves 

 that occur in the Greenland Sea, excepting as to the 

 effects produced on ice, hereafter to be noticed, any 

 observations on this subject will equally apply to 

 the waves in other seas. 



Waves, though the entire product of the wind, 

 are dependent, as to their magnitude, on the nature 



