694 T. C. CHAMBERLIN 



it may be well to forestall misapprehension by making clear our 

 view that such an origin of the craters of the moon is in itself 

 improbable, for bodies moving in orbits under the control of the 

 sun should plunge into the moon, if they strike it at all. at various 

 angles to the vertical. In many cases the stroke should be quite 

 oblique to the surface and should leave elongated pits, unsymmetri- 

 cal rims, unequal dispersions of debris, and other tell-tale features; 

 all the more so because the moon had no atmosphere to retard and 

 turn downward the path of the bolides. Apparently the only 

 escape from these grave objections lies in supposing that the explo- 

 sive reaction was so great that it completely overwhelmed the effects 

 of the direct stroke. If this assumption were tenable, it would seem 

 to imply that the explosive dispersion was so great that it must 

 have scattered all mobile matter, and especially all liquid matter so 

 effectually as to insure its cooling while in flight. 



THE SIGNIFICANCE OF THE EXPLOSIVE PHENOMENA OF THE MOON 



The moon seems to have been a paradise of Krakatoas and 

 Katmais. Interpreted as the product of gaseous explosion, the 

 abundance and the greatness of the craters of the moon carry 

 special significance. They have commonly been thought to imply 

 a once molten state of the moon. I think the argument lies in 

 precisely the opposite direction. If the moon, in its formative 

 stage had been a molten globe, its high temperature should have 

 set free all gases susceptible of being freed by any temperature 

 that ever arose afterward. Its liquid state and its convective cir- 

 culation would have brought these gases to the surface and given 

 them opportunities of escape never equaled later, for the high 

 temperature of the surface would have forced unsurpassed molec- 

 ular activity and have insured their escape from the control of 

 the moon. Even the cold full-grown moon cannot hold the vol- 

 canic gases. After all such gases had been boiled out of the moon 

 and had escaped, and the gas-free lava had cooled, the moon should 

 have been devoid of the means of explosive action. 



On the other hand, if the moon were built up of minute clastic 

 particles which carried such amounts of occluded and combined 

 gases as meteorites do, and as they naturally would from their 



