Trans. N. V. Ac. Sa. 110 jFe&. 6, 



considerable diversity of composition, and graduating insensibly into 

 those above and below. 



5. The evolved products are given ofif in all stages of the progressive 

 change. They, too, are usually mixtures when elimmated, and are con- 

 stantly changing by the absorption of oxygen and conversion into their 

 final state, carbonic acid. 



6. The escape of the evolved products is constantly taking place 

 from all great accumulations of carbonaceous matter ; the gases com- 

 monly and the liquids occasionally are seen escaping from beds of coal ; 

 and both abundantly from the much greater accumulations of carbon- 

 aceous matter in bituminous shales, gas and oil springs being in- 

 separably connected with the outcrops of all these great deposits. Coal 

 and petroleum also spontaneously change when exposed to the air, the 

 coal rapidly losing its volatile constituents, and with them its value for 

 the manufacture of gas and coke ; petroleums becoming by evapora- 

 tion and oxidation thicker and darker, finally forming asphalt, or with- 

 out oxidation, paraffine, ozokerite, etc. 



7. The differences which we observe in the residual and evolved 

 products are in part due to peculiarities in the organic tissue from which 

 they are formed, and in greater degree to the stage of distillation that 

 they have reached. Different kinds of vegetation, as oaks, pines, ferns, 

 algce, etc., having somewhat different compositions, yield diversified 

 products in distillation ; and petroleums, though mainly derived from 

 cellular plants (seaweeds, etc.), are in part the products of the distilla- 

 tion of animal matter, and owe some of their characteristics to that 

 fact. 



8. Every step in the process described above is abundantly illus- 

 trated in our coal and oil fields, all of which have been studied by 

 the speaker. The views presented are not the coinage of the imagina- 

 tion, but a simple transcript from nature ; and they are sustained by 

 such an array of facts as to compel their acceptance. Instances were 

 given of the conversion of lignite into coal, anthracite and graphite, 

 by volcanic action, and of the natural derivation of asphalt, as- 

 phaltic coals, and anthracite, from petroleums. 



9. Further the great work going on in nature's laboratory may be 

 closely imitated by art ; the differences in the results being simply the 

 consequence of differing conditions in the experiments. Vegetable 

 tissue has been converted artificially into the equivalents of lignite, 

 peat, anthracite and graphite, with the emission of vapors, gases and 

 oils, closely resembling those evolved in natural processes. So 

 petroleum may be distilled to form asphalt, and this in turn converted 

 into Albertite and coke (/. e., anthracite), Grahamite has been artifi- 

 cially produced from petroleum by Mr. W, P. Jenney. 



