THE TIDES AND TIDAL ROTATION 75 



whether Nature agreed with him or not, and that the 

 day has really lengthened. 



Since, then, he reasoned, the day is longer (or 

 ought to be longer) than it was yesterday, there must 

 have been a time many millions of years ago when the 

 day was (or ought to have been) so much shorter that 

 the earth turned on its axis in a matter of three hours 

 or so. But, he continued, if we go back so far as that 

 we should also take into account the then theoretically 

 high temperature of the earth, and consider the possi- 

 bility of earth and moon having once formed a single 

 body. 



Now. since 1 that, greater earth, he went on, was 

 (or might have been) both viscous, and rotating at a very 

 high rate of speed, the solar tides raised upon it must, 

 by theory, have been exceedingly powerful, so much so 

 indeed as perhaps to be able to pluck away a rib from 

 the earth's substance and thiereby give birth to the 

 moon as a separate planet. But this act of disruption 

 would not, he argued, lessen the plasticity of the sep- 

 arate bodies, hence when they started to revolve around 

 Their common center of gravity at approximately the 

 original rotational speed of the parent body, they must 

 have proceeded to raise tides upon each other's sur- 

 faces. The resulting protuberances or ansae, by virtue 

 of their gravitational attraction, then began, as he im- 

 agined, to exercise the double effect of retarding the 

 rotation of their own respective bodies, and that of their 

 respective opposites as well, with the result of little by 

 little causing the moon to recede from the earth, and 

 at the same time to slow up its rotation to its present 



Now, any theory that breeds mysteries faster than 

 it dispels them is ipso facto false. Having explained, 



*Compare the later chapter on the Moon. 



