232 RESEARCHES UPON THE CHEMICAL PROPERTIES OF GASES. 



to results at still higher pressure. If it is conceded that the proportion of carbon 

 monoxide and ethylene in the gas evolved during destructive distillation decreases 

 progressively vyrith increase of pressure, and that these two constituents vanish alto- 

 gether at sufficiently high j)ressures, it would still seem necessar}'" to suppose that 

 the pressure must have been at least twice as great when the process occurred in the 

 rocks, as in the case of Engler's experiments. 



Taking the specific gravity of the rocks to be about 2|, it may be assumed that 

 twelve feet of rock strata represent a pressure of 1 atmosphere, six hundred feet of 

 solid rock would then be required to produce a pressure of 50 atmospheres. This 

 would be considerably less than the depth of the same quantity of rock material in 

 the form of loose sediment, before its consolidation. 'No case can be cited in recent 

 times where sediment six hundred feet deep has been so suddenly accumulated as to 

 bury unchanged the vast quantities of animal remains necessary to account for the 

 production of oil and gas upon Engler's hypothesis, that oil and gas have resulted 

 from the action of pressure and moderate heat upon animal matters. 



There is probably no reason to suppose that the gaseous defines have, under the 

 influence of pressure, given place to others of highei- boiling point, by a process of 

 polymerization. Should the possibility of such a change be proved, the absence of 

 olefines from natural gas and their presence in peti'oleum might be explained. The 

 possibility of secondary reactions among the constituents of a complex gas mixture 

 at high temperatures and under pressure, adds difficulty to the problem, and caution 

 is needed to avoid the error of overestimating the importance of any given reaction. 



It is generally true, however, that under such conditions secondar}^ changes are 

 probable, and that unsaturated compounds — olefines, acetylenes, carbon monoxide — 

 are likely to result, especially when water vapor and carbon dioxide are present. 



It is a well-known fact, that when petroleum is distilled, considerable quantities 

 of unsaturated hydrocarbons are produced which did not exist in the original crude 

 oil. This is shown by the bromine absorption of the different products. The pro- 

 cess of " cracking " or breaking up by heat of the hydrocarbons in petroleum into 

 simpler and less saturated compounds, is familiar to all oil refiners. Chemically 

 speaking, "cracking" means the production of unsaturated hydrocarbons. 



The fact that Engler has, in his extremely interesting and important researches, 

 produced by distillation of animal matters, so great a variety of paraffins, constitutes 

 by far the strongest argument in favor of his hypothesis. 



Sorge, in an article which has been reproduced in numerous journals {J. CJi. 

 Soc, 1888, p. 31, abstract), has stated, that a strong resemblance exists between 

 Pennsylvania natural gas and gas manufactured from Westphalian coal. Similarity 



