Although the chemical composition is nearly the same, the manner in which the different species or fragments of vegetables behave under distillation is quite different. In fact, according to Mr. Carnot, the plants already cited furnish the following results on distillation: 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 coniferæ of the present day (Araucariæ). 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.