128 SIMPLER ORGANIC SUBSTANCES 



When mountain ranges are raised, cracks opening upwards 

 are formed at the summit while, at the foot of the mountains, 

 the cracks open downwards. In the course of time they are filled 

 up but the younger the rocks . . . the fresher are the cracks, and 

 through them water can obtain access to parts of the interior 

 of the earth in a way which cannot normally happen (in plains). 



Thus, according to Mendeleev, the water of the sea was 

 able to reach the red-hot central nucleus of the Earth which 

 contained large amounts of iron mixed with carbon ; and, 

 by reacting with the carbon, it gave rise to the hydrocarbons 

 of petroleum. 



This theory has now been abandoned because it is contra- 

 dicted by a number of geological observations. It is hard 

 to imagine how the water could have trickled down to reach 

 the carbides of the nucleus of the Earth from which it was 

 separated by a layer of rock formations more than a thousand 

 kilometres thick. Apart from this, all the considerations 

 which we have already put forward about the isotopic com- 

 position of petroleum, its optical activity and other physical 

 and chemical properties, as well as the way in which deposits 

 of petroleum are laid down in sedimentary formations, show, 

 without doubt, that the main mass of the organic material 

 of petroleum arose secondarily as the result of alteration of 

 the substances of animals and plants which lived on the 

 Earth at some time.^^ 



Mendeleev's main contention that hydrocarbons could be 

 formed abiogenically by the action of water on carbides is 

 completely justified by both earlier and later studies. As 

 early as 1841 Schrotter obtained a liquid similar to petroleum 

 by the action of dilute acids on pig iron. This reaction was 

 later studied by H. Hahn.^* By dissolving a large quantity of 

 white iron in acid over several weeks he obtained a very con- 

 siderable amount of petroleum-like liquid. It is interesting to 

 note that in addition to his work cited by Mendeleev, S. Cloez 

 carried out experiments in which the formation of hydro- 

 carbons occurred during the decomposition of ferromangan- 

 ese containing 5 per cent of carbon under the action of super- 

 heated steam alone.'® 



K. Kharichkov"" observed the formation of liquid and 

 gaseous hydrocarbons when aqueous solutions of chlorates 



