THE CARBONIFEROUS SYSTEM. 1Y1 
This is the condition in which we find most of the beds of peat and 
lignite that accumulated in what is called the Carboniferous age, millions 
of years ago, and which, deeply buried, have been subjected to a slow 
and general distillation, resulting in the different varieties of bitumin- 
ous coal. Where exposed to peculiar influences, as to heat from volcanic 
eruptions, or from the elevation of mountain chains, where all the strata 
are metamorphosed, the volatile constituents of bituminous coal are par- 
tially or perfectly driven off, giving us, first, semz-bituminous coal, then 
anthracite, and finally graphite. The process by which graphite and 
anthracite are formed from ordinary bituminous coal is indicated in the 
succeeding formule: 
Bituminous Coal. Loss. Anthracite. 
(OBITANOIN ‘ccdehoncticachoo eR bace nec Hac RE aseEL ae eee 18.10 3.07 14.53 
Hele GOS O MM camarcrstyns ice aon aeate oon ssiaeals dels esle dre scsiee 1.20 0.93 0.27 
(ORS REET as5eBi Aa SOSeRUBAUS GUE RE Hees Seno aan ene 2.07 E32 0.65 
Anthracite.  . Loss. Graphite. 
CATO renee nee mioad octets cations otsear Cees LAOS 1.42 13.11 
Heliy clin OG Teen rer as een ahaa tas ccs ccameasce ste S27. 0.14 0.18 
Oxey COMP erotics wee Sosetciosserslesseveeeeavesearey OGD, 0.65 0.00 
All the varieties of coal mentioned above shade into each other, and 
we have lignites that exhibit every degree of approach to bituminous 
coals; semi-bituminous coals intermediate between bituminous coal and 
anthracite and graphitic anthracite, by which the anthracites are con- 
nected with graphite. 
The geological portion of the different varieties of coal accords with 
the theory of their origin given above. For example: the oldest rocks 
known, contain only the residual products of the distillation of vegetable 
tissue, graphite and anthracite. In the Carboniferous age the terrestrial 
vegetation was luxuriant over large areas, and conditions prevailed 
favorable to the formation of beds of peat.** These, submerged and deeply 
buried under sediments which were deposited upon them, have, as a 
* Judging from the circumstances in which the most extensive deposits of peat are 
produced at the present time, we may infer that the climate was moist and equable, 
but neither very hot nor cold, since in tropical climates vegetable tissue runs through 
all its changes so rapidly that but but little accumulates in a bituminized state, while 
in a cold climate vegetation is stinted, and there is but little of it to be preserved. It 
has been suggested that in the Carboniferous age the atmosphere contained much 
more carbonic acid than now. But of this no proof is given except the succulent and 
luxuriant vegetation, while the great numbers of air-breathing animals represented 
by remains found in the Carboniferous rocks indicate that the atmosphere was not 
greatly different from what it now is. 
