SOURCES OF ENERGY 167 



made their appearance there could accumulate and be 

 further transformed in the waters of the hydrosphere. Under 

 these circumstances we must expect a considerable variety 

 of organic substances on the surface of the Earth. There 

 might, indeed, have arisen representatives of all such com- 

 pounds known to us. The difficulty which faces us when we 

 try to give a concrete account of the course of organic evolu- 

 tion on the Earth lies not so much in the absence or insuffici- 

 ency of chemical possibilities, as in the number of alternative 

 intersecting routes along which any particular organic mole- 

 cule could have been transformed. 



As was shown in Chapter IV, the main source from which 

 the abiogenic hydrocarbons of the surface of the Earth were 

 derived was the lithosphere. 



As early as 1889 V. Sokolov^^ put forward the hypothesis 

 that the primary hydrocarbons of the Earth ^vere taken up 

 by molten magmata and that when these cooled and solidified 

 the hydrocarbons could once more separate out and that 

 they are still separating out in fissures in the lithosphere. 

 Such a hypothesis, however, seems extremely improbable in 

 the light of present-day astronomical and geological evidence. 

 The main forms in which carbon was retained on the Earth 

 during its formation were, as we have already seen, native 

 carbon and carbides. During the development of the litho- 

 sphere they interacted with geological formations incorporat- 

 ing hydrates or other forms of constitutional water. Accord- 

 ing to R. Goranson" molten magma contains 5 per cent or 

 more of water. The geological formations of the primaeval 

 Earth must have been e\en richer in water, for the hydro- 

 sphere contained only one-tenth as much water then as it 

 does now and the rest of the water was still bound in the 

 lithosphere. 



It is well known that, on reaction with water, carbides of 

 calcium, barium, strontium and lithium give rise to acety- 

 lene, those of aluminium and beryllium to methane, that 

 of manganese to mixtures of methane and hydrogen, those of 

 the rare metals to mixtures of acetylene and methane, while 

 carbides of uranium give rise to mixtures of methane, hydro- 

 gen, ethylene, and liquid and solid hydrocarbons, etc.®^ 



Many carbides are not decomposed by water at ordinary 



