THE EARTH. 175 



vails tlircughout our whole planetary system. The more mat- 

 ter there is contained in any body, the more it attracts ; and its 

 influence decreases in proportion as the distance, when squared, 

 increases. This being premised, let us see what must ensue 

 upon supposing the moon in the meridian of any tract of the 

 sea. The surface of the water immediately under the moon, is 

 nearer the moon than any other part of the globe is ; and, there- 

 fore, must be more subject to its attraction, than the waters any 

 where else. The waters will, therefore, be attracted by the 

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

 where the attraction is greatest. In order to form this eminence, 

 it is obvious that the surface, as well as the depths, wdW be agi- 

 tated ; and that wherever the water runs from one part, suc- 

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

 the waters of the sea, running from all parts to attend the mo 

 tion 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 ot 

 their rising ceasing to operate, they will flow back by their na- 

 tural gravity into the lower parts from whence they had tra-- 

 velled; and this retiring of the waters will form the ebbing ot 

 the sea. 



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

 general, 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 comprehend this, it must 

 be observed, that the part of the earth and its waters 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 



