542 The Rev. S. Haughton on Physical Geology. [Dec. 20 ; 



we shall have 



Maximum "Westerly Current at B and D = ^, 



4w 



35 



Maximum Easterly Current at A and C =-— , 



4o> 



Difference =^ e. 



4w 



Prom (14) we have, 



3r 



vd(h = — cos 20 cty ; 

 4&> 



but 



r = a(l— ecos 2 0), (15) 



therefore 



vd(f) = — cos 20(1 — e cos 2 (f)dd>. 

 4w 



This is to be integrated all round the circumference, in which process 

 the periodic terms disappear, and we find 



^0=|^| ^l-0cos20c?0-|^l+ cos4^cty} ; 



and, finally, 



J o ^=-4^ X l> (16) 



The mean radius of the earth is 



3958 miles = 3958x5280 ft. = 20,898240 ; 

 say 21 million ft. ; hence, assuming a — 6=3 ft., 



7,000000 



therefore 



1'53 7T 



Eesidual Tidal Current = x - ft. per second. 



( j\J\J\JyJ\J\J «= 



The angular velocity of the Eesidual Tidal Current will therefore be 



1-53 



7,000000x21,000000 2 



The retardation of angular velocity caused by friction is equal to 



F x time x angular velocity , ~. 



moment of inertia ' 



or 



F l'odt 7T 



C X 7,000000 x 21,000000 X 2* 



