64 



the form of repeated distillation of fish oil made under some ten 

 atmospheres of pressure, whereby he obtained fair quantities of 

 oil with ail the characteristic properties of crude petroleum — a 

 brown colour, green fluorescence, etc. , and containing 90 per cent, 

 hydrocarbons. These experiments on fish oil as a likely source 

 of petroleum had to some extent been anticipated by the work of 

 two Americans, Warren and Storrer, who in 1859 obtained a 

 petroleum by the destructive distillation of crude fish oil after 

 saponification with lime. According to Engier's theory, during 

 the decay of marine animals, taking place in a deficiency of water 5 

 dissolved air, all the protein substance was converted into gaseous 

 or soluble matter, the fat alone remaining little diminished, if any- 

 thing, in quantity. 



A striking illustration of an intensified and wholesale destruc- 

 tion and decay of animal organisms, such as might have occurred 

 during Kimmeridgian times, is given by the Russian geologist, 

 Andrussow, in a description of the bay of Adshi Darja, on the 

 eastern side of the Caspian Sea. This expanse of some 7000 

 square miles is connected with the main sea by a very narrow 

 channel. Owing to the excessive evaporation going on over this 

 ''back water," not only is the salinity raised cons:derably above 

 that of the Caspian, but a strong current is caused to run into the 

 bay, carrying with it large quantities of the varied marine fauna, 

 fish and plankton. The animals soon perish, some decaying in the 

 waters and others on the open beach. So abundant is the mass 

 of carcasses in spring that the sea-gulls then feed only on fish eyes. 



Confirmatory of the opinion that animal remains are the 

 ultimate source of petroleum is the discovery made by Donath of 

 protein decomposition derivatives in bituminous shales from South 

 Austria. Even stronger evidence is the presence in oils of optic- 

 ally active compounds affecting the plane of polarised light ; these 

 substances can only have been made by organised life. 



The next step in the course of formation of petroleum, accord- 

 ing to Engier's theory, appears to have been the saponification of 

 the surviving fats and the conversion into a wax-like matter fatty 

 acid — adipocere, the glycerine being carried off in solution by the 

 water. This adipocere or carcass wax mixed with mineral sedi- 

 ments would form the bituminous shales, limestones and sand- 

 stones. In a still later stage the earth wax would gradually lose 

 carbon di-oxide and be finally converted into the hypothetical 

 mother substance of the oils — kerogen. The last stage of all would 

 appear to be the slow distillation from thiskerogen of the free oils 

 and gases into the superincumbent absorbent sandstones and lime- 

 stones, in which, under favourable conditions of folding, they 

 remain until released by borings. Confirmatory of this last point 

 is the occurrence of thick beds of oil shales underlying the exten- 

 sive Appalachian oil-fields and of richly fossiliferous oil shales 

 beneath the Galician oil-fields. 



A further transformation of mineral oils yet remains to be 

 briefly mentioned. Under favourable -conditions oils rich in the 



