THE TIDES. 169 



our thoughts the details of the investigation, we 

 consider its general plan and objects, we must 

 allow it to be one of the most splendid works of 

 the greatest mathematician of the past age. To 

 appreciate this, the reader must consider, first, 

 the boldness of the writer, who, having a clear 

 understanding of the gross imperfections in the 

 methods of his predecessors, had also the cour- 

 age deliberately to take up the problem on 

 grounds fundamentally correct (however it might 

 be limited by suppositions afterwards introduced) ; 

 secondly, the general difficulty of treating the 

 motion of fluids ; thirdly, the peculiar difficulty 

 of treating the motions when the fluids cover an 

 area which is not plane but convex ; and fourthly, 

 the sagacity of perceiving that it was necessary 

 to consider the earth as a revolving body, and 

 the skill of correctly introducing this considera- 

 tion. This last point alone, in our opinion, gives 

 a greater claim for reputation than the boasted 

 explanation of the long inequality of Jupiter and 

 Saturn." 



Tidal theory must be carried on along with tidal 



