Volatile Fixed Coke.
matters. residue.
Calamodendron 35.5 64.7 Well agglomerated.
Cordaites 42.1 57.8 Quite porous.
Lepidodendron 34.7 55.3 Well agglomerated.
Psaronius 29.4 60.5 Slightly porous.
Ptychopteris 39.4 60.5
Megaphyton 35.5 64.5 Well agglomerated.
Coal of the Great Bed 40.5 59.5 Slightly porous.

These differences in the proportions of volatile substances, of fixed
residua, and of density in the coke obtained seem to be in harmony with
the primitive organic nature of the carbonized tissues. We know, in fact,
that the wood of the Calamodendrons is composed of alternately radiating
bands formed of ligneous and thick walled prosenchymatous tissue, while
the wood of Cordaites, which is less dense, recalls that of certain
coniferae of the present day (Araucariae).

We have remarked above that the portions of Lepidodendron analyzed
belonged to that part of the bark that was considerably thickened and
lignefied. So too the portion of the Megaphyton that was submitted to
distillation was the external part of the hard bark, formed of hypodermic
fibers and traversed by small roots. The Psaronius, on the contrary, was
represented by a mixture of roots and of parenchymatous tissue in which
they descend along the trunk.

It results from these remarks that we may admit that those parts of the
vegetable that are ordinarily hard, compact, and profoundly lignefied
furnish a compact coke and relatively less volatile matter, while the
tissues that are usually not much lignefied, or are parenchymatous, give a
bubbly, porous coke and a larger quantity of gas. The influence of the
varied mode of grouping of the elements in the primitive tissues is again
found, then, even after carbonization, and is shown by the notable
differences in the quantities and physical properties of the products of
distillation.

The elementary chemical composition, which is perceptibly the same in the
specimens isolated in the sandstones and in those taken from the great
deposit, demonstrates that the difference in composition of the
environment serving as gangue did not have a great influence upon the
definitive state of the coal, a conclusion that we had already reached
upon examining the structure and properties of the coal pebbles.

We may get an idea of the nearly similar composition of the