A thin section of a piece of Commentry cannel coal shows that this substance consists of a yellowish-brown amorphous mass holding here and there in suspension very different plant organs, such as fragments of Cordaites, leaves, ferns, microspores, macrospores, pollen grains, rootlets, etc., exactly as would have done a gelatinous mass that upon coagulating in a liquid had carried along with it all the solid bodies that had accidentally fallen into it and that were in suspension.

It is evident (as we have demonstrated) that other cannel coals may show different plant organs, or even contain none at all, their presence appearing to be accidental.  The composition itself of cannel coal must be, in our theory, connected with the chemical nature of the materials from whence it is derived, and that were first dissolved and then became insoluble through carbonization.  Several preparations made from Australian (New South Wales), Autun, etc., boghead have shown us merely a yellowish-brown amorphous mass holding in suspension lens-shaped or radiating floccose masses which it is scarcely possible to refer to any known vegetable organism.

Among the theories that we have cited in the beginning, the one that best agrees with the facts that we have pointed out is the third, which would admit, then, two things in the formation of coal.  The first would include the different chemical reactions which cannot yet be determined, but which would have brought the vegetable matter now to the state of soft coal (with its different varieties), and now to the state of anthracite.  The second would comprehend the preservation, through burial, of the organic matter in the stage of carbonization that it had reached, and as the result of compression and gradual desiccation, the development of the physical properties that we now find in the different carbonized substances.

We annex to this article a number of figures made from preparations of various coals.  These preparations were obtained by making the fragments sufficiently thin without the aid of any chemical reagent, so as to avoid the reproach that things were made to appear that the coal did not contain.  This slow and delicate method is not capable of revealing all the organisms That the carbonaceous substance contains, but, per contra, one is riot absolutely sure of the pre-existence of everything that resembles organs or fragments of such that he distinguishes therein by means of the microscope.

Our researches, as we have above stated, have been confined to different cannel coals, anthracite, boghead, and coal plants isolated either in coal pebbles, or in schists and sandstones.

[Illustration:  12a:  FIG. 1.—­Lancashire cannel coal; longitudinal section, X200.]

[Illustration:  12b:  FIG. 2.—­Lancashire cannel coal; transverse section, X200.]