KECENT COSMOGONIES 207 



forcibly from the earth shall never return to it again, it 

 must depart with this same velocity of 6.9 miles a second. 

 Now, according to Darwin's premises, the moon must 

 have been flung off with just that speed, since it appears 

 she is never to return to the earth. 



The query here suggests itself, what was the nature 

 of the energy that accomplished this stupendous cast? 

 It could not have been heat, because Darwin lays the 

 cause of the earth's axial acceleration to its having cooled 

 and shrunken. Furthermore, it can be shown that as 

 much flinging energy w r ould have been required as there 

 w r ould be heat generated by the reverse process of the 

 fall of the moon from infinity upon the earth; that is to 

 say, more than enough to vaporize both of these great 

 bodies completely, Plainly, then, the energy employed 

 was not physical, but magical or imaginary. 



That Darwin was not, however, entirely devoid of 

 the saving salt of common sense, in spite of the indica- 

 tions, is shown by his concluding sentence (The Tides, p. 

 284) : " There is nothing to tell us whether this theory 

 affords the true explanation of the birth of the moon, and 

 I say that it is only a wild speculation incapable of veri- 

 fication. ' ' I leave it to the reader to make his own com- 

 ments. 



THE THIRD-BODY THEORY 



In his very interesting little book, "The Birth of 

 Worlds and Systems", published in February, 1911, A. 

 W. Bickerton, Professor of Physics and Chemistry in 

 Canterbury College, of New Zealand, has collected to- 

 gether a series of papers, dating from the year 1878, set- 

 ting forth a unique speculation, to which he has given the 

 title of "Theory of the Third Body." In order that I 

 may not fail to report him correctly, I shall use his own 

 words quite freely, omitting only inessentials. For- 

 tunately his first chapter is itself a summary of his views : 



A pair of dead suns, that is to say two dark stars, colliding, 

 would possess energy sufficient, if suddenly converted into heat 

 to account for the phenomena of temporary stars. All suns pos- 

 sess proper motion. Hence it was evident that the orbits of two 



