THE MOON 381 



the middle of its thickness, or, by calculation, 1250 F., 

 abs., while the average temperature for the entire planet 

 should be no less than 80,000 degrees! Now, Darwin's 

 idea was not that the moon was explosively ejected out of 

 the heart of the earth, but that she was flung off from its 

 periphery by centrifugal force. Had the former act been 

 postulated, it would be good logic to say that she bore 

 with her the average temperature of the planet, but inas- 

 much as she was flung off from the outside, her hotness 

 could not have been greater than that of the crust, the 

 very coldest part of the planet, and theoretically very 

 little above what the satellite should have possessed had 

 she separately agglomerated! 



Finally, to cut short a long list of criticisms, it is not 

 true that, even had the moon originally possessed the 

 same temperature as the earth, her volcanic displays 

 would have been more devastating in the ratio of six to 

 one. The solar gravity is 27.6 times that of the earth 

 and 165 times that of the moon, yet he ejects matter at 

 times as far above his photosphere as the moon is from 

 the earth. Anyone who has ever watched quarrymen at 

 work knows that " tamping" is a very important part of 

 the blasting process. A heavier charge lightly tamped 

 will not begin to create as much havoc as a lighter one 

 well tamped. Bamming the charge too tight has ruined 

 many a good gun and robbed its owner of his life. The 

 heavier the weight of the superincumbent materials the 

 longer are the explosions delayed and the severer when 

 they come. 



The biggest crater on the earth is said to be that of 

 Haleakla, Hawaii, possessing a diameter of less than 

 seven miles; and there are not more than a half dozen 

 terrestrial craters that could be made out by a lunar 

 observer, though armed with our best telescopic instru- 

 ments. On the moon, on the contrary, there are literally 

 thousands such, a half dozen of the largest being upwards 

 of a hundred miles in diameter, and thence dwindling to 

 invisible sizes. To account for all these dynamically and 

 adequately, Darwin should have accouched his moon 



