124 PECKHAM — THE GENESIS OF BITUMENS. [April 1, 



nothing but decomposition products are found in the distillate, 

 while coke remains in the still. These decomposition products are 

 very varied. Those that are geologically old yield paraffine, while 

 those that are recent do not.^ 



Prof. Mabery has remarked that all petroleums contain the same 

 proximate principles in different proportion. While this statement 

 may be absolutely true, it is not so relatively. The palaeozoic 

 bitumens have been most carefully studied and they consist mainly 

 of paraffines. The Tertiary bitumens have been less carefully studied, 

 and they consist principally of benzoles and their derivatives in 

 great variety. Mingled with these are the olefines and other series 

 of hydrocarbons in small proportion, with an immense number of 

 oxygen, sulphur and nitrogen derivatives and substitution com- 

 pounds, the existence of which has been only recently suspected. 



It can, therefore, be asserted that the natural bitumens and the 

 substances resembling therh that are obtained by the destructive 

 distillation of mineral and organic substances, are strikingly similar. 

 The palaeozoic bitumens bear a resemblance to the simple distil- 

 lates produced in the presence of steam, at low temperatures, when 

 nitrogen is practically absent. The Tertiary bitumens resemble the 

 distillates obtained at higher temperatures and when the raw mate- 

 rial is rich in animal remains. There are, however, a large number 

 of bitumens that have been too little investigated to admit of any 

 generalizations concerning them. In illustration of this statement 

 I would call attention to the valuable papers of Prof. Henry Wurtz, 

 in which he shows that many so-called native paraffines are probably 

 olefines.'"^ I would suggest that some of them may be the higher 

 naphtenes, that have the same percentage composition as ole- 

 fines. The solution of these problems awaits a vast amount of 

 research. 



14. In the preceding pages I have given an outline of the views 

 generally held by chemical and physical geologists concerning the 

 chemical phenomena attending the cooling of the earth and its 

 shrinking and contracting crust. To these I have added a resuf?ie 

 of the technical and chemical knowlege we possess concerning bitu- 

 mens. I shall now proceed to discuss, in the light of these facts, 



^ S. F. Peckham and L, A. Linton, Atner, Jour. Sci. (4), i, 193. S. F. and 

 H. E. Peckham, Jour. Soc. Chem. Industry^ xvi, 424; H. Endemann, ibid, xv, 

 871 ; xvi, 121. 



2 II. Wurtz, Eng. and Min. Jour., xlviii, 25, 114 ; li, 326, 376, 



