THE MOON 367 



during which she would gradually become more and more 

 distinctly "retrograde" in character. In order for the 

 sun to succeed in "wrenching" the earth and moon 

 apart in this way, his leverage on the moon must, of 

 course, be increased relatively to that of the earth, and 

 as leverage varies inversely with distance, we easily per- 

 ceive that the moon will become a planet when 



in which M represents the mass of the sun, D his lunar 

 distance ; and m and d the mass and lunar distance of our 

 earth respectively. Substituting the known values for 

 M, D, and m and performing the operation, we obtain for 

 the value of d, 1,330,000 miles. 



In a former chapter I explained how the earth and 

 moon together are kept revolving around the sun by the 

 action of the Prime Resultant, so that, including it, we 

 have three rival forces continually pulling at the moon, 

 all together being capable of accounting from instant to 

 instant for all her varying movements. If, now, to these 

 were added an inherent arbitrary rotation, as predicated 

 by current theory, it is plain that the moon's safety 

 would be imperilled. Like a weather vane she has to be, 

 and she is, free to respond automatically to the eddying 

 currents continually playing upon her, only in this case 

 the "currents" are gravitational instead of atmospheric 

 in their nature. 



PROBLEM OF THE LUNAR SURFACE 



Generally speaking, the moon has a mottled appear- 

 ance, consisting of great drab splotches on a silver shield. 

 In Galileo's lifetime, and for many years afterward, 

 these splotches were looked upon as seas, and they are 

 still so called by the Latin equivalent, maria. However, 

 they are no longer regarded by scientists in this light, 

 owing to the fact that the improvement of the telescope 

 long ago revealed many permanent markings on the beds 

 of the supposed oceans which, of course, could not exist 



