THE EARTH 141 



white nebulae ? These and many other questions 

 seem to require answer before we can rest satisfied 

 with the ordinary theory of the production of the 

 atmosphere. To us it seems much more likely 

 that the water and carbonic acid were a gradual 

 product of volcanic action, and that a great part 

 of the oxygen was later in origin, and was formed 

 by the chemical action of plant-life. 



Wherever there are volcanoes, hydrogen is 

 ejected and steam is formed ; and it is at least 

 suggestive to find that the great seas are ringed 

 with volcanoes. No doubt, too, the ocean-beds, 

 where the crust of the Earth would be thinner, 

 were also sites of volcanic eruption ; and such a 

 multitude of volcanoes in full action for a few 

 million years could easily account for most of the 

 water in the sea. It is very likely that in the early 

 days of the Earth volcanoes were much more 

 plentiful and active than now. We find in the 

 Moon twenty thousand or thirty thousand extinct 

 volcanoes (some with craters 1 5,000 feet high), and 

 it is quite possible that at one time the Earth had 

 volcanoes as numerous and vigorous. It is true 

 that the usual theory supposes that the steam of 

 volcanoes is caused by a leakage from the sea into 

 the hot crust of the Earth ; but considering the 

 pressure and heat of the crust, such leakage is 

 surely unlikely. 



