X.] BITUMENS AND PYROSCHISTS. 179 



Huron lost, by ignition in a closed vessel, 12.4 per cent, and left a 

 black residue, which was not calcareous. A portion in fine powder 

 was digested for several hours with heated benzole, which took up 

 0.8 per cent of brown combustible matter. The residue, carefully 

 dried at 200 F., then lost, by ignition in a close vessel, 11.3 per cent, 

 and by subsequent calcination 11.6 additional, equal to 23.7 per 

 cent of combustible and volatile elements. The calcined residue 

 was gray in color. By distillation in an iron retort there were 

 obtained from this shale 4.2 per cent of oily hydrocarbons, besides 

 a large quantity of inflammable gas, and a portion of ammoniacal 

 water. 



The pyroschists of Bosanquet belong to the Devonian series, and 

 contain the remains of land-plants, so that a partially decayed vege- 

 tation may be supposed to have been the source of the organic 

 matter which is intimately mingled with the earthy base of the rock. 

 Such was probably the case in the abundant pyroschists of the 

 coal period ; but in the pyroschists of the Utica formation (which 

 are Upper Cambrian) the chief organic remains to be detected are 

 graptolites, with a few brachiopods and crustaceans. No traces of 

 terrestrial vegetation are known to have existed at that time, nor do 

 the schists contain the evidences of any marine plants. The pyro- 

 schists of mesozoic age, in several parts of Europe, contain, on the 

 contrary, numerous fossil fishes, from the soft parts of which, or 

 other animal matters, the combustible substance of these rocks is 

 generally supposed to be derived. (Dufrenoy, Mineralogie, IV. p. 

 603.) Similar questions arise with regard to the origin of the bitu- 

 mens of the various geological formations already noticed ; for while 

 in some cases, as in the tertiary rocks of Trinidad, they are clearly 

 traced to a vegetable source, bitumens are also met with in Cam- 

 brian, Silurian, and Devonian limestones of marine origin, which 

 abound in shells and corals, but afford no traces of vegetable remains. 

 When, however, it is considered that the lower forms of animals 

 contain considerable portions of a non-azotized tissue analogous in its 

 composition to that of plants, and that even muscular tissue, plus 

 the elements of water, contains the elements of cellulose and ammo- 

 nia, it is easy to understand that vegetable and animal remains may, 

 by their slow decomposition, give rise to similar hydrocarbonaceous 

 bodies.* The various fermentations of which sugar is susceptible 



* This relation was first pointed out by me in 1849. (American Journal of 

 Science (2), VII. p. 109.) I then endeavored to show that the albuminoid 

 bodies might be regarded as a nitryl of cellulose, or some isomeric hydrate 

 of carbon, and represented by the formula C 24 H 17 N 3 8 . I had already pro- 



