EFFECT OF KESIDUAL CURRENT WESTWARD. 29 



elevation also is diminished by friction in the proportion 

 of cos 28 to 1. Eemembering this, it is easy to see that 

 the figure just given should he multiplied by ^ sin 48, so 

 that with the greatest possible displacement, the result would 

 be practically 0. In order that 8 should be = 22 J, since 



tan 28 = 7000 /, / should be = -- (which is far beyond 



its value) . We should then have 1 '83 f Jsin 48 = 7 nearly. 



The retardation in this case would therefore be less than 

 one second in 700 million years. It will be seen here- 

 after that /is millions of times less than this. 



There is another way of viewing the matter, which 

 does not introduce /. The following consideration explains 

 this : 



4. Of the effect of the residual current westward due 

 to the change in the time of high water. 



The constant force found above, = \He sin 28, produces 

 an accumulating westward tendency in the water. This 

 once impressed will continue to increase until the increase 

 is checked by friction, that is, until friction becomes equal 

 to this constant force. This occurs when 



sin 28 x t x/= He sin 28, 



that is, when t = -. After this the velocity of this west- 



t/ 



ward current is constant, the constant force being expended 

 on counteracting friction. Therefore when we take a 

 sufficiently long time we may assume that the total moment 



