1918] 



on The Romance of °etroleum 



881 



was a recognised industry in China, and it is worthy of note that the 

 instruments employed bear a close resemljlance to modern drilling 

 appliances. 



Petroleum occurs in greater or less quantity throughout the whole 

 range of strata of the earth's crust, from the Laurentian rocks to the 

 most recent members of the Quaternary period, but it is found in 

 quantities of industrial importance almost wholly in the compara- 

 tively old Devonian and Carboniferous formations, on the one hand, 

 or in the various divisions of the comparatively young Tertiary rocks, 

 on the other. 



Its origin has been the subject of much controversy among dis- 

 tinguished geologists and cliemists who have devoted special study 

 to the subject. Berthelot and Mendeleeff lent the weight of their 

 authority to the theory that petroleum was derived from metallic 



Fig, 1,— Zante. Oil Spring. 



carbides lying far beneath the porous strata in which the oil is 

 stored, and made the attractive suggestion that the process might 

 be conceivably in operation at the present time. The view is 

 now, however, universally accepted that petroleum is of organic 

 origin, and that it has been produced from vegetable matter and tlie 

 lower forms of animal life, chiefly aggregated during the geological 

 periods referred to, when favourable conditions, which did not persist 

 through the whole period, occurred. In certain places, for instance 

 in Karabugas Bay, on the eastern side of the Caspian Sea, in Sweden, 

 in Sardiniii, and in the eastern part of the Mediterranean, there is 

 some conversion of organic matter into petroleum actually to be seen 

 in progress at the present time. 



It is not difficult to account for the formation of adequate deposits 

 of the necessary material. In the comparatively deep and quiescent 



