UNDKR FM.AXKTKSIMAI. HYl'f miKSIS 311 



struck tin- earth, added to the at mosphere. Thus tin- atmosphere 

 grew as the earth-body it. sell grew. Volcanoes, when they came 

 into action, also added to the atmosphere, for they discharge much 

 IMS. This picture of the early atmosphere is very different from the 

 va>t hot vaporous atmosphere of the supposed molten earth. 



3. Initial volcanic stage. As the earth grew and its gravity 

 increased, its interior became more and more compressed and 

 therefore more and more heated. Radio-active matter was no 

 doubt gathered in with the other matter, and this developed heat. 

 When the heat from these two sources became sufficient to liquefy 

 the most fusible portions of the earth matter in particular spots, 

 the fluid parts began to work their way toward the surface by fluxing. 

 Other fusible matter was picked up on the way, and the radio-active 

 matter in particular joined the rising threads of lava. When this 

 rising lava reached the surface, volcanic action was inaugurated. 

 According to this view, volcanoes do not originate from a "molten 

 interior," or from "reservoirs" of molten matter left over from a 

 general molten state, but the lava is generated from time to time 

 by the continued action of radio-active substances, conjoined with 

 the effects of compression and molecular rearrangement within the 

 earth. The heat of the interior of the earth is thus carried outward 

 about as fast as it liquefies the more fusible parts within its reach. 

 Thus the interior of the earth only reaches the temperature neces- 

 sary to melt the more fusible parts, leaving the earth as a whole solid 

 all the time. 



4. Initial hydrospheric stage. Water in the form of vapor is 

 light and active, and probably was not the first gas to be held by 

 the growing earth; but when the earth became large enough, water- 

 vapor was held in the atmosphere, and when at length saturation 

 was reached, it condensed into water and initiated the hydrosphere. 

 The source of water, according to the hypothesis, was the same 

 as that of atmospheric gases. 



It may be added that the hypothesis gives a simple explanation 

 of ocean basins and continental protuberances. Because of unequal 

 growth, the surface of the earth may never have been perfectly 

 spheroidal, so that when water began to accumulate on its surface, 

 it gathered in depressions. The planetesimal material which after- 

 wards fell into the water was protected from weathering, while that 

 which fell on the higher land was exposed to weathering, with its 

 attendant lessening of specific gravity. Thus the depressed areas 



