SEQUEL TO THE EPOCH OF NEWTON. 259 



be allowable to mention here Mr. Whewell's at- 

 tempts to trace the progress of the tide into all 

 the seas of the globe, by drawing on maps of the 

 ocean what he calls Cotidal Lines ; lines marking 

 the contemporaneous position of the various points 

 of the great wave which carries high water from 

 shore to shore 43 . This is necessarily a task of labour 

 and difficulty, since it requires us to know the 

 time of high water on the same day in every part 

 of the world ; but in proportion as it is completed, 

 it supplies steps between our general view of the 

 movements of the ocean and the phenomena of 

 particular ports. 



Looking at this subject by the light which the 

 exampl^ of the history of astronomy affords, we 

 may venture to repeat, that it will never have 

 justice done it till it is treated as other parts of 

 astronomy are treated ; that is, till Tables of all the 

 phenomena which can be observed, are calculated 

 by means of the best knowledge which we at pre- 

 sent possess, and till these Tables are constantly 

 improved by a comparison of the predicted with 

 the observed fact. A set of Tide-observations and 

 Tide-ephemerides of this kind, would soon give to 

 this subject that precision which marks the other 

 parts of astronomy; and would leave an assemblage 

 of unexplained residual phenomena, in which a 

 careful research might find the materials of other 

 truths as yet unsuspected (s). 



3 Essays towards an Approximation to a Map of Cotidal 

 Lines. Phil. Trans. 1833, ia36. 



S2 



