THE TIDES 161 



kernel, notwithstanding its slightly greater distance from 

 the moon, should be attracted much more powerfully than 

 the oceans in front of it. He knew, also, that the resul- 

 tant effect of such action could only be to shallow the 

 seas on the earth 's moonward side instead of deepening 

 (raising) them. This conclusion, however, did not suit 

 Newton's preconceptions in the least, for it meant re- 

 tracting his previous reasoning, restoring the original, to 

 him obnoxious, ratio of 180 to 1 in the sun's favor, and, in 

 short, relinquishing altogether his cherished theory of the 

 lunar causation of tides. Unequal to this sacrifice, he 

 sought a way out of the dilemma by tampering again 

 with his own law of gravitation. As one lie leads to 

 another, so one basic misinterpretation of nature's laws 

 leads to an endless chain of absurdities. He had already 

 dared to distort the second clause of the law to read that 

 tidal forces vary, not as the inverse squares but as the 

 inverse cubes of the distances, hence he now felt driven, 

 in the interest of consistency, to go on and alter the first 

 clause to match its changed companion. Accordingly, he 

 made that to read, that gravitational attraction, when 

 operating as a tidal force, disregards differentiations of 

 density, and here it was that he introduced in support his 

 famous vacuum-tube experiment which we discussed in 

 the preceding chapter. 



Newton's next step was to invent some method, 

 favorable to his theory, for computing the tidal heights. 

 Making use of his rule of inverse cubes, he ascertained 

 the tidal force of the moon to be 1-2,871,400 of the 

 earth's gravity and that of the sun, 1-12,868,200. (Young 

 gives 1-8,640,000 and 1-19,600,000 respectively). The 

 question with him was : How are these quantities to be 

 translated into terms of tidal height so as to obtain 

 plausible results? 



It was well-known to the generation before Newton 

 that the figure of the earth is not that of a sphere, but of 

 an oblate spheroid, and her equatorial ring seems always 

 to have been assumed, as a plain matter of course, to be 

 the running effect of the centrifugal force of her axial 



