The Tides. 349 



feet, and brings it to t ; that the part E being 

 nearer to the moon, and still more forcibly at- 

 tracted, is carried to the extent of 30 feet ; and 

 that the point G being more distant from the 

 moon and more feebly attracted than the centre T, 

 is only drawn as far as g to the extent of 1 feet ; 

 it is evident that the radii * t e and t g must be 

 longer by 10 feet than the radii TE and TG. 

 The waters therefore must appear elevated to 

 that extent, while they are lowered at p and h. 

 Thus the fluid (as appears evidently by the 

 figure) will be elevated at two opposite points 

 in the line AG, in which line are the centres of 

 the earth and the moon. -If further the at- 

 traction of the sun is added to that of the moon, 

 the former being about a third of the latter, 

 the effect will be proportionably greater ; but if 

 these two attractions are placed in counterpoise 

 to each other, the effect will be proportionably 

 less. 



The motion of the waters of the sea (at least 

 that of which we are sensible, and which is not 

 common to them with the whole mass of the 

 terrestrial globe), is not the effect of the entire 

 action of the sun and moon, but of the difference 

 between the action of these luminaries upon the 

 centre of the earth, and upon the fluid with 

 which it is covered, as well on the upper as the 

 lower surface. It is v this difference which we ' 



* The radius is a line from the centre to the circu.m* 

 ference of any circular figure. 



