Trans. N. Y. Ac. Scz. ATO Feb. 6, 
considerable diversity of composition, and graduating insensibly into 
those above and below. 
5. The evolved products are given off in all stages of the progressive 
change. They, too, are usually mixtures when eliminated, 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 arein 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, 
alge, 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. 
g. 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 (z. ¢., anthracite). Grahamite has been artifi- 
cially produced from petroleum by Mr. W. P. Jenney. 
