254 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



carbonic acid in solution came in contact with the alkali 

 metals. Mendelejeff likewise believes in the action of 

 subterranean water upon certain iron ores and metallic carbides 

 at high temperatures. But these theories have not been 

 accepted by geologists, as they are not in harmony with the 

 occurrences of the oil. All other hypotheses consider the 

 decay of organic substance essential to the production of 

 the series of mineral oils. Bischof in his Chemical Geology 

 derives asphalt and petroleum from the slow decay of 

 vegetable matter, an explanation which he bases upon the 

 frequent occurrence of marsh-gas in peat-mosses. Quenstedt 

 thinks the impregnating oil in the Swabian shales has been 

 originated by the decomposition of fishes and other animal 

 organisms interred in the shales. A similar explanation is 

 given by Sterry Hunt for the petroleum oils in North America. 

 While Quenstedt and Hunt regard the oil as produced in situ 

 in the strata containing the decaying organisms, many 

 geologists hold the opinion that the hydro-carbonaceous 

 products of decay collect in the stratigraphical horizons above 

 those which actually contain the decaying material. 



Engler tried experimentally to distil fish-train oils ; under a 

 pressure of 20 to 25 atmospheres, and at a temperature of 

 365 to 420, a distillate is procured which approaches the 

 characters of the natural Pennsylvania!! petroleum, and, as 

 Heusler has shown, after treatment with aluminium chloride, 

 is identical with it. 



Ochsenius argues that the mineral oils have been prepared pre- 

 eminently in shallow estuaries where animal remains and algse 

 have undergone decomposition in salt-water containing a rich 

 supply of chlorides, more particularly magnesium chloride. 



It has been observed by Andrussow, Natterer, and Barrois, 

 that petroleum in minute quantity bubbles up to the surface of 

 the water and mud in the Kara Boghaz on the shores of the 

 Caspian Sea, in Bitter Lakes of the Isthmus of Suez, and 

 in the desiccating saline basins of Brittany, all of these being 

 localities where considerable accumulations of animal remains 

 and plant detritus collect. 



E. Volcanoes. The controversy between Neptunists and 

 Volcanists, which had still continued keenly in Germany 

 during the early years of the nineteenth century, relaxed 

 after the desertion of Alexander von Humboldt and Leopold 



