SIMPLE HYDROCARBONS. 323 



the rock material was in the state of a line mud ; that 

 through this mud much vegetable or animal matter was 

 distributed, almost in the condition of an emulsion ; that 

 the stratum of this mud becoming afterward overlaid by 

 other strata, the decomposition of vegetable or animal mat- 

 ter went forward without the presence of atmospheric air, 

 or with only very little of it. Under such circumstances 

 either vegetable material or animal oils might be converted, 

 as chemists have shown, into mineral oil. Dry wood con- 

 sists approximately (excluding the ash and nitrogen) of 6 

 atoms of carbon to 9 of hydrogen, and 4 of oxygen. If now 

 all the oxygen of the wood combines with a part of the car- 

 bon to form carbonic acid, and this 2 C 2 , thus made, is re- 

 moved, there will be left 4 H 9 ; twice this, C 8 H ]8 , is the 

 formula of a compound of the Marsh-gas or Naphtha series. 

 Again animal oils, by decomposition under similar cir- 

 cumstances, produce like results. Removing from oleic 

 acid its oxygen, 2 , and 1 of carbon — together equivalent to 

 1 of carbonic acid — there is left C 17 H 34 , which is an oil of 

 the Ethylene series ; and margaric acid would leave, in the 

 same way, C 16 H 34 , or a combination of oils of the Marsh-gas 

 or Naphtha series. Warren and Storer have obtained from 

 the destructive distillation of a fish-oil, after its saponifica- 

 tion by lime, several compounds of the Marsh gas series, be- 

 sides others of the Ethylene and Benzole series. The de- 

 compositions in nature may not have been as simple as those 

 in the above illustrations, yet the facts warrant the infer- 

 ence that the oils may have been derived either from vege- 

 table or animal matters. Fossil fishes are often found abun- 

 dantly in black oil-yielding shales, and Dr. Newberry has 

 suggested that fish-oil may be the most abundant source of 

 the oil and the oil-yielding hydrocarbons. 



The oil which is collected in great cavities among the 

 earth's strata, as in Western Pennsylvania, is believed by 

 most writers on the subject to have come from underlying 

 rocks, such as the black oil-yielding shales. The heat pro- 

 duced in the rocks by the friction attending movements and. 

 uplifts, is supposed to have been sufficient to have made the 

 oil from the hydrocarbon of the carbonaceous shale or other 

 rock, and co, have caused it to ascend among the strata to 

 the cavities where it was condensed, and now is found by 

 boring. 



The oils, exposed to the air and wind, undergo change in 



