280 ON THE TRANSMUTATION OF ROCKS, &o., 



Now, in order to ascertain under what temperatures such 

 substances become transmuted, M. Delesse employed M. 

 Jacequelaine to subject them to distillation, and from the notes 

 made by the latter (which I will abridge) we shall see how trans- 

 mutation may be produced at a lower temperature than is 

 generally believed. We find, then, the following results : 



Turf threw off its odour at from 220 to 230 C., and distilled 

 at 260, = 516 F. 



Lignite became empyreumatic at 220, and distilled at from 

 260 to 285. 



Coal from St. Etienne threw off its odour at 150, that from 

 Dresden at 205, and English coal at 295, distilling at 400, 

 which was also the point of distillation of Swansea anthracite, 

 though it became odorous at 310. 



We may therefore take the point of distillation of bituminous 

 matters in such combustibles as, respectively, 260, 300, and 

 400 = 752 F. This is far below red heat. 



Now, taking the scale of temperature of the earth at 1 F. for 

 fifty feet vertical, the above temperature will correspond to a little 

 more than seven English miles, so that a basalt or trap coming 

 up from that depth would be sufficiently hot to convert coal into 

 coke. And inasmuch as at a little more than a quarter of the 

 temperature mentioned, or about 212 Fahrenheit, the water in 

 the combustible would pass off, it is certain that a basaltic outburst 

 coming from a depth of little more than two miles would be quite 

 sufficient to produce considerable change. 



M. Jacequelaine says that other processes besides that of heat 

 can volatilise combustibles. 



Thus heated alkaline solutions percolating to a great depth 

 may dissolve the bitumen and increase the proportion of carbon, 

 and so we have one explanation of the cause why the deepest 

 and oldest coals are richest in carbon ; and we may also thus 

 understand why dissolution and not dry distillation may be sup- 

 posed capable of producing the change from lignite to graphite. 



Whilst on this topic it is only natural to express an opinion 

 on the occurrence of the Mineral Oil so abundant in America, and 

 in various parts of Europe and Asia. 



That it maj originate in a natural distillation of combustible 



