638 SCIENCE PROGRESS 



be paralleled by those of oil-fields. Nitrogen and sulphur com- 

 pounds become concentrated in the most inspissated orweathered 

 products of petroliferous material, and this agrees with the 

 production of ammonium sulphate from oil-shales, but not from 

 oil rocks. The tendency of oil-shales to become richer at the 

 summits of anticlines also agrees with the anticlinal concentra- 

 tion of oil in oil-fields. 



Mr. Cunningham-Craig has dealt with the problem from a 

 geological standpoint. Mr. H. R. J. Conacher, however, in an 

 important paper read before the Glasgow Geological Society, 

 and to be published immediately (Trans. Geol. Soc. Glasgow, 

 191 7, 16, Pt. 2), has attacked it from a microscopic point of view. 

 By means of an improved technique he has been able to make 

 very thin sections of Scottish and other oil-shales, and related 

 materials. His principal conclusion is that the oil-yielding 

 matter consists of resin fragments (" yellow bodies," " spores," 

 " algae," of other investigators), which owe their external forms 

 to their original sites in plants, or to attrition in transport, 

 modified by subsequent pressure ; whilst the internal structure 

 has been developed by shrinkage or pressure, by flow around 

 resistant grains, or by distortion of vacuoles or gas cavities. 

 The objection that very little resinous material can be extracted 

 from oil-shales by organic solvents is met by the facts that there 

 is not only great variation in the behaviour of resins with 

 solvents, but that their solubility decreases with the age and 

 exposure of the material. He does not countenance the view 

 that inspissated petroleum plays any part in the production of 

 torbanites or the Lothian oil-shales, as it is difficult to under- 

 stand how, in the case of torbanites, 10 or 20 per cent, of mineral 

 matter could retain 80 or 90 per cent, of inspissated petroleum. 

 Moreover rocks containing unquestionable inspissated petroleum 

 show no structures comparable with the " yellow bodies." The 

 Scottish oil-shales are believed to have originated as quiet 

 estuarine mudflats, to which an abundant supply of finely 

 macerated vegetable matter was contributed by water flowing 

 from swamp areas. 



A paper of some interest in relation to this subject is one on 

 the chemical composition of petroleum in relation to its genesis 

 and geological occurrence, by C. F. Mabery (Econ. Geol. 19 16, 

 11, 511). The presence of sulphur and nitrogen compounds in 

 oil is discussed, and the author concludes that the quality of a 



