X.] BITUMENS AND PYROSCHISTS. 175 



APPENDIX. 



ON BITUMENS AND PYROSOHISTS. 



(1861-1863.) 



This paper is reprinted from the American Journal of Science for March, 1863, but 

 many of the facts and deductions which it contains appeared in an earlier paper, 

 entitled Notes on the History of Petroleum, in the Canadian Naturalist for July, 1861, 

 reprinted in the Chemical News, and also in the Report of the Smithonian Institution 

 for 1862. I had for some time previously maintained that the source of the petroleum 

 of the West was not, as was generally thought, to be found in the Devonian pyro- 

 schists, but in the underlying fossiliferous limestones, and had shown the relation of 

 the oil-springs to anticlinals. See a report of my lecture before the Board of Arts of 

 Lower Canada, in the Montreal Gazette of March 1, 1861. 



IT is proposed in the following pages to bring together some facts 

 and theoretical considerations bearing upon the nature, origin, and 

 distribution of bitumens, together with a few remarks on the rocks 

 commonly called bituminous shales. Under the general name of 

 bitumen, as is well known, are included both the liquid forms, 

 petroleum and naphtha, and the solid varieties known as asphalt or 

 mineral pitch. The related substances guayaquillite and berenge- 

 lite, and the substance known as idrialine, seem from the modes of 

 their occurrence to have a similar origin to asphalt, and thus to be 

 distinct from fossil resins. The characters of fusibility and solu- 

 bility in liquids like benzole and sulphuret of carbon, serve to dis- 

 tinguish the solid bitumens from coal and some other matters about 

 to be noticed. It is to be remarked that the chemical composition 

 of these bodies varies considerably ; the earlier analyses of petro- 

 leum and naphtha give a composition which approaches C n H n ; but 

 the later investigations of De la Rue and Muller on the products 

 distilled from the petroleum of Rangoon, and those of Uelsmann on 

 that from Sehnde, show a slight excess of hydrogen, the various 

 hydrocarbons having, for the most part, the formula C n H n+2 . The 

 first formula C n H n may however be adopted, as expressing approxi- 

 matively the composition of the liquid bitumens. The different 

 analyses of asphalt show a diminished quantity of hydrogen, and 

 small quantities of oxygen. Thus the elastic bitumen from Der- 

 byshire gave to Johnston results which may be represented by 

 C^H^O^g ; * of two varieties of asphalt analyzed by Ebelmann, the 



* In these formulas, which have been calculated for twenty-four equivalents 

 of carbon, to compare with cellulose, C 24 H 20 20 , I have designed to represent 



