238 THE BORDERLAND OF SCIENCE. 



towards the moon, so as to fall upon her, would recruit 

 her mass. As we must assume from the known mass 

 of the earth that she was for ages in a sunlike con- 

 dition, we must believe that during those ages that 

 face of the moon which was continually directed earth- 

 wards received no inconsiderable supply of erupted 

 matter. For it must be remembered that when the 

 process began the moon was much larger in volume, 

 though considerably less in mass, than at the present 

 time. She would, therefore, at that time intercept a 

 much greater proportion of the erupted matter. More- 

 over, since, after she had shrunk into a semiplastic but 

 still growing orb, the moon must have continued for 

 a very long time subject to this rain of earth-born 

 missiles, there is reason for regarding as very consider- 

 able the quantity of matter by which her bulk was thus 

 increased. Moreover, if it be remembered that the 

 meteoric missiles thus expelled from the earth would 

 necessarily be exceedingly hot, probably liquid even be- 

 fore their fall, and certainly liquefied at the moment of 

 collision with the moon's surface, we find a priori 

 evidence for that very downfall of liquid drops, of 

 which, as mentioned above, the present aspect of the 

 moon seems to afford evidence. It is certainly a note- 

 worthy circumstance that a theory devised to explain 

 a most striking peculiarity of the moon's globe, should 

 account also for a feature, not less striking, which had 

 not been specially in view when the theory was invented. 

 We must pass, however, from these considerations, 

 because the evidence on which they have been based is 



