THE TIDES. 



but there is this difference between these effects ; that where it 

 acts upon solid matter, the component parts of which are at diffe- 

 rent distances from it, and therefore subject to different attractions, 

 it will not disturb their relative arrangement, since such dis- 

 turbances or disarrangements are prevented by the cohesion which 

 characterises a solid body ; but this is not the case with fluids, 

 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 H, is greater 

 than that which it exercises upon the solid mass of the globe 

 between H and D ; consequently there will be a greater tendency 

 of this attraction to draw the fluid which rests upon the surface at 

 H towards 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 over 

 H, forming a more convex protuberance between E and I, as 

 represented in the figure. 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 remote 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 consequently will have a less 

 tendency to gravitate towards- 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 pro- 

 tuberance between L and K, similar exactly to that which we have 

 already described between E and I. As the difference 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 

 attraction on the latter and upon the waters at N, it follows that 

 the height of the fluid protuberances at z and N are nearly 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, is nearly the same. 



Now from this explanation it will 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 moon ; 



since, if that attraction were equal in all the component parts of 



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