subject to different attractions, it will not disturb the relative arrangement of 

 these particles, since such disturbances or disarrangements are prevented by 

 the cohesion which characterizes a solid body ; but this is not the case with 

 fluid, the particles of which are mobile, and which, when solicited by different 

 forces, will have their relative arrangements disturbed in a corresponding 

 manner. 



The attraction which the moon exercises upon the shell of water which is 

 collected immediately under it near the point Z, is greater than that which it 

 exercises upon the solid mass of the globe at H and D ; consequently there 

 will be a greater tendency of this attraction to draw the fluid which rests upon 

 the surface at H toward the moon, than to draw the solid mass of the earth 

 which is more distant. 



As the fluid, by its nature, is free to obey this excess of attraction, it will 

 necessarily heap itself up in a pile or wave at H, forming a more convex pro- 

 tuberance, as represented in the figure between R and I. Thus high water 

 will take place at H, immediately under the moon. The water which thus 

 collects at H, will necessarily flow from the regions B and F, where, there- 

 fore, there will be a diminished quantity of water in the same proportion. 



But let us now consider what happens to that part of the earth, D, most re- 

 mote from the moon. Here the waters being more remote from the moon than 

 the solid mass of the earth under them, will be less attracted ; and consequent- 

 ly will have a less tendency to gravitate toward the moon. The solid mass of 

 the earth, D H, will, as it were, recede from the waters at N, in virtue of the 

 excess of attraction, leaving these waters behind it, which will thus be heaped 

 up at N, so as to form a convex protuberance between L and K, similar, ex- 

 actly to that which we have already described between R and I. As the dif- 

 ference between the attraction of the moon on the waters at Z and the solid 

 earth under the waters, is nearly the same as the difference between its attrac- 

 tion on the latter and upon the waters at N, it follows that the height of the 

 fluid protuberances at Z and N are equal. In other words, the height of the 

 tides on opposite sides of the earth, the one being under the moon and the other 

 most remote from it, are equal. 



Now from this explanation, it will, we trust, be apparent, that the cause of 

 the tides, so far as the action of the moon is concerned, is not, as is vulgarly 

 supposed, due to the mere attraction of the earth ; since, if that attraction 

 were equal in all the component parts of the earth, there would assuredly be 

 no tides. We are to look for the cause, then, not in the attraction of the moon, 

 but in the inequality of its attraction on different parts of the earth. The greater 

 this inequality is, the greater will be the tides. Hence, as the moon is sub- 

 ject to a slight variation of distance from the earth, it will follow, that when it 

 is at its least distance, or at the point called perigee, the tides will be greatest ; and 



