1^*68.] ^ciT LPeckhatii. 



nsplialtic minerals by ca change whicli renders tliem less soliil)le 

 and l'iisil)le, and more nearly rescm1)lin<2: coals. 



Tlie derivation of solid forms of bitumen from the class A, 

 presupposes the possibility of forming aspluiltum b}' the int^pii^- 

 i^alion of petroleum. There are many small deposits filling 

 cavities in rocks, both of asphalts and pyroasphalts, mentioned 

 b_y Dr. Hunt and others, which maij have been formed in this 

 manner.* I am however extremely doubtful if the veins of so- 

 called inspissated petroleum, of which albertite is an example, 

 are not more probably the jjroduct of the distillation of asphaltic 

 or pyroasphaltic schists, at a very low temperature, resulting 

 from their metamorphosis. This view obtains additional force, 

 if the theory be admitted that metamorphic action has taken 

 place through the agency of watery vapor, as the distillation 

 Avould then have taken place at the lowest temperature, under 

 conditions favorable to the production of the largest quantity of 

 distillate, of the greatest density possible. The enormous quan- 

 tity of petroleum of ordinar}^ density, w4iich would upon inspis- 

 sation furnish a solid residue, sufficient to form a deposit equal 

 in extent to that of the albertite, can scarcely be conceived of 

 even when compared Avith such vast accumulations as those of 

 Pennsylvania and Rangoon. 



Enormous deposits of asphaltum have been formed in Califor- 

 nia b}^ the decomposition of petroleums of the class //. As- 

 l)haltic schists of the same class are also numerous in that 

 region. 



The classification of bitumens which I have adopted, was sug. 

 gcstcd by the results of many months' study of the formation 

 of asphaltum in California, by natural causes, and by the results 

 of analysis and experiments upon California and Penns^'lvania 

 petroleums, made in the laboratory of Brown Universit}'. 



Throughout the oil-belt of Southern California, every form of 

 bitumen derived from petroleum of the class />, is found, with 

 the exception of naphtha, pyroasphalts and pyroschists. Light 

 petroleums of a beautiful green color, pass through ever}- degree 

 of blackness and densitj' to solid asphaltum. None of the 

 natural forms, nor distillates produced from them, contain a 

 trace of paraffine. The green oils upon exposure to atmos- 



* Rep. Geo. Sur. of Canada, 186(!, pp. 252 and '20.2; Vanuxem Rep. Geo. Sur. 

 of New York. 



VOL. X 3k 



