372 On the prohUble importance of Tide Observations, S^c. 



luminaries, but to the position at some time before. The time 

 which the ocean thus takes in accommodating itself to the 

 action of the tidal forces, appears in the form of what I have 

 called — the age of the tide. 



But still a part of this age is owing to a real transfer of the 

 tidal wave. In some cases, the whole difference of the age of 

 the tide at different places, is owing to this transfer ; thus on 

 the shores of England, the age of the tide goes on increasing 

 from the Scilly Isles to London. This increase is not owing to 

 the action of the moon on the water in the channel, but to the 

 time employed by the motion of a tide wave produced by the 

 moon in the Atlantic or Antarctic ocean. 



The Cape of Good Hope and Southern ocean generally, 

 are likely to have the least portion of the apparent age of tide, 

 owing to the time employed in transfer; and, therefore, the 

 age of the tide there will be the original lagging of the tide 

 after the corresponding positions of the moon and sun. On 

 this account, the age of the tide at the Cape of Good Hope is 

 an interesting subject of inquiry. 



14. The age of the tide at any place, is the sum of the 

 original lagging and of the time of travelling. But there 

 appears to be indisputable evidence (in my tide observations 

 shortly to be published, and in others already published) that 

 the time of travelling of the tide is different at different periods 

 of the moon's age. Hence, in crder to know the time of 

 travelling of the tide from the Cape of Good Hope to any other 

 place, we ought to know it for the complete semilunation ; 

 which will make it necessary to observe the time of high water 

 at all the tides, and not merely at springs. 



For these reasons, observations of the tides, and especially 

 of the times of high water, carefully and constantly made, 

 will be of great value and interest ; even if they are made only 

 at one station. But if corresponding observations can be made 

 at several stations, distant from each other by a considerable 

 length of coast or sea, the utility and importance of the 

 observations will be greatly increased. 



W. W, 



Trinity College, Cambridge, January 1, 18.35. 



