APPENDIX. 287 



Java ; on that of Sumatra ; at Ceylon ; at the Laccadiva Islands ; 

 at the Seychelles ; on the coast of Madagascar ; and at Amsterdam 

 Island, at twelve : but at the Chagos Islands and Mauritius it is 

 high water at about nine, and at the Keeling Isles about eleven. 

 Here, then, it would seem that there is cause for much perplexity. 



Having now stated the principal facts which occur to my mind, I 

 will mention the conclusions drawn from them, and then attempt to 

 explain the anomalies. 



Let E G (fig. 1.) represent a section of our globe, of which A B 

 C D is supposed to be land, and E F G H water. Let H M show 

 the direction in which the moon's attraction would operate. The 

 effect of her attraction, according to Newton's demonstration, would 

 be to raise the water at F by positive attraction of the water, and at 

 H by attracting the earth more than the water : — let the dotted line 

 represent the consequent figure of the ocean. 



In fig. 2, let the ocean be supposed 90° or six hours wide ; let the 

 moon act in the direction M F ; and let the dotted line represent the 

 altered position of the water when moved out of its natural position 

 (with respect to the earth) by the moon's attraction. 



Again, in fig. 3, suppose the moon acting in the line M K, and 

 the dotted line representing the figure taken in that case by the 

 ocean. 



It will occur to the reader that but little water can rise at F 

 and H (fig. 1), at F (fig. 2), or at K (fig. 3), unless water falls or 

 sinks, at E and G (fig. 1), G (fig. 2), F and G (fig. 3). because 

 water is but slightly compressible, except under extraordinary pressure, 

 and because it is incapable of being stretched ; therefore, if at any 

 place the sea is raised above its natural level, the excess must be 

 supplied by a sinking taking place elsewhere. There cannot be a 

 void space left under the sea between the water and its bed ; and 

 there is no lateral movement of the particles at the surface only 

 of the ocean sufficient to cause high tides on either shore : — 

 therefore the conclusion may be drawTi, that the whole mass librates 

 or oscillates. 



By librating I mean such a movement as that which a large jelly 

 would have, if its upper part were pushed on one side,, and then 

 allo-wed to vibrate while the base remained fixed : and by oscillating 

 I mean a movement like that of water in a basin, after the basin is 

 gently tilted and let down again : and that such a motion would be 



