126 COMPOSITIOX OF AMERICAN PETROLEUM. [Feb. 5, 



cavities, where its solid condition would tend to its permanent pres- 

 ervation. 



The sedimentary limestones contain frequently crystalline calcite 

 cementing together the grains of amorphous mineral matter. 

 Changes in temperature, causing unequal expansion of this calcite 

 in different directions, by reason of the form of its crystals, might 

 in the course of time modify the process by changing the internal 

 structure of the rock. The presence of salt in solution and the 

 solvent action of carbonic acid would no doubt exert an important 

 influence, although its nature could not be foreseen. 



The occurrence of petroleum in the fossil shells of mollusks and 

 in the cells of corals would then have no more geological signi- 

 ficance than its occurrence in geodes, or in cavities in rocks, or the 

 presence of solid bitumen in hollow quartz crystals or in sphalerite, 

 as all such cases are perhaps attributable to one and the same 

 source, namely, to its presence formerly in a state of wide distribu- 

 tion in the pores of the rock. 



ON THE COMPOSITION OF AMERICAN PETROLEUM. 



BY CHARLES F. MABERY. 



{Read February 5, 1S97.) 



Petroleum is found in Pennsylvania in sandstones of various 

 formations ; in southern Ohio in the Berea grit and other sands ; in 

 Ohio in the Trenton limestone ; in Canada in the Corniferous sand- 

 stone ; in California, Texas, Colorado, and other American fields in 

 shales and sandstone formations, which represent in general the 

 geological strata in which are the various oil fields in Russia, 

 Roumania, Germany and Austria, Japan, India, etc. Crude oils show 

 great variation in their physical properties, such as color, specific 

 gravity and odor, and differences in their chemical reactions de- 

 pending on variation in composition. 



The first systematic investigation for the purpose of ascertaining 

 the composition of American petroleum was made by Pelouze and 

 Cahours, who referred the entire body of crude oil, including paraf- 

 fine, to the series homologous with marsh gas, CnH2n+2- At about 

 the same time, 1862, C. M. Warren began a study of Pennsylvania 



