104 A HISTORY OF 



immediately antier the moon, is nearer the moon than any other part 

 of the globe is ; and, therefore, must be more subject to its attraction 

 than the waters any where else. The waters will, therefore, be at- 

 tracted by the moon, and rise in a heap ; whose eminence will be the 

 highest where the attraction is greatest. In order to form this emi- 

 nence, it is obvious that the surface, as well as the depths, will be 

 agitated; and that wherever the waters run from one part, succeeding 

 waters must run to fill up the space it has left. Thus the waters of 

 the sea, running from all parts, to attend the motion of the moon, 

 produce the flowing of the tide ; and it is high tide at that part wherever 

 the moon comes over it, or to its meridian. 



But when the moon travels onward, and ceases to point over the 

 place where the waters were just risen, the cause here of their rising 

 ceasing to operate, they will flow back by their natural gravity into 

 the lower parts from whence they had travelled ; and this retiring oi 

 the waters will form the ebbing of the sea. 



Thus the first part of the demonstration is obvious; since, in gene- 

 ral, it requires no great sagacity to conceive that the waters nearest 

 the moon are most attracted, or raised highest by the moon. But the 

 other part of the demonstration, namely, how there come to be high 

 tides at the same time, on the opposite side of the globe, and where the 

 waters are farthest from the moon, is not so easy to conceive. To com 

 prehend this, it must be observed, that the part of the earth and its wa- 

 ters that are farthest from the moon, are the parts of all others that 

 are least attracted by the moon : it must also be observed, that all the 

 waters, when the moon is on the opposite side of the earth, must be 

 attracted by it in the same direction that the earth itself attracts 

 them ; that is, if I may so say, quite through the body of the earth, 

 towards the moon itself. This, therefore, being conceived, it is 

 plain that those waters which are farthest from the moon, will have 

 less weight than those of any other part, on the same side of the 

 globe; because the moon's attraction, which conspires with the earth's 

 attraction, is there least. Now, therefore, the waters farthest from 

 the moon, having less weight, and being lightest, will be pressed on 

 all sides, by those that, having more attraction, are heavier: they will 

 be pressed, I say, on all sides; and the heavier waters flowing in, 

 will make them swell and rise, in an eminence directly opposite to 

 that on the other side of the globe, caused by the more immediate 

 influence of the moon. 



In this manner, the moon, in one diurnal revolution, produces two 

 tides; one raised immediately under the sphere of its influence, and 

 the other directly opposite to it. As the moon travels, this vast body 

 of waters rears upward, as if to watch its motions ; and pursues the 

 same constant rotation. However, in this great work of raising the 

 tides, the sun has no small share ; it produces its-wn tides constantly 

 every day, just as the moon does, but in a much >- ss degree, because 

 the sun is at an immensely greater distance. Tb*'* there are solai 

 tides, and lunar tides. When the forces of these wo great luminn- 

 ries concur, which they always do when ' they are ei*r<er in the same, 

 or in opposite parts of the heavens, they jointly produ'** a much great- 

 Hi tide, than when they are so situated in the heavens, a* ich to make 



