Page:Popular Science Monthly Volume 23.djvu/71

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HOW THE ANCIENT FORESTS BECAME COAL.

a book. A close examination of coal and its texture under the microscope will show that only water could have taken all the fragments of such different sizes and consistencies and arranged them in this way. The disposition is the same as is always shown when leaves and fragments of plants, having become thoroughly soaked, sink and form stratifications at the bottom of ponds. In the coal, the elements continue visible, and their arrangement in superposed lamina? is evident, while the interstices between the planes of junction appear to have been filled up in the course of the formation of the beds. These facts, with the perfect condition of the organization of many of the fragments; their agglomeration in an amorphous pulp, the resultant of the previous maceration of a host of fragments; and the reduction of the whole mass by compression to half of its primitive thickness—all parts of one and the same phenomenon—point to the action and weight of the bed of water at the bottom of which the stratification took place. The perfect uniformity which reigned over the formation of coal has given it generally a schistous structure, in thin leaves disposed in a parallel fashion and fissile in the direction of the plane of deposition. It is also found, on attentive examination, to be somewhat varied in constituency, according to the varying character of the elements of which it is composed, and the different stages of freshness and maturity in which they were deposited. One kind, which M. Grand' Eury calls "fusaine," from its resemblance to a stick-charcoal, comes from the decomposition of stems from which the anatomical structure has disappeared while they preserve their form. The green parts appear as crystalline laminæ, or scales, or black particles in the amorphous mass. This mass, the result of the maceration of wholly decomposed particles, constitutes the amorphous coal in which, besides "fusaine," we can always discover some remains of vegetable structure testifying to the common origin of all the coal products. Within these differences of type are innumerable variations passing from one to another, the existence of which prevents our establishing a clear distinction between the coals most homogeneous in appearance and those which show the multifarious and manifest traces of hardly altered organized elements.

M. Grand' Eury's sketches introduce us to the depths of the carboniferous forests, into regions of dense moisture, at the feet of gentle slopes where are accumulating in stagnant ponds immense drifts of the remains of constantly active, exuberant, and quickly exhausted vegetation. Masses of this kind may even now be observed in the midst of the virgin forests of hot countries; how much more might we have expected to find them in ancient epochs, when the trees made no wood, but sent up spontaneous, ungainly shoots, sudden growths in green columns, the function of which was as ephemeral as their texture was weak! Most of the carboniferous stems, hollow or filled with pith only, fell by the sheer exaggeration of their growth; the tree-ferns