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Rh about this time, or during the 12th century, near Liége. It is said that a smith named Houillos first used coal in the village of Plenevaux, near that place, about this time, and in commemoration of this discovery the French name of coal is houille. Coal was first used in London in 1240; and in 1300 considerable quantities were made use of. A tax of from 1s. to 10s. per chaldron was imposed on coal in England during 400 years, ending in 1803. The first attempt to make pig iron with pit coal appears to have been in 1612, when a patent for this purpose was granted to Simon Sturtevant, but it was unsuccessful. Dudley also obtained patents in 1619 for the same purpose, but also failed, and was imprisoned for debt in consequence. The first successful effort appears to have been made by Mr. Darby of Coalbrookdale in 1713; and in 1747 cast iron suitable for cannon is said to have been made at this place, both the coal and iron ore used being taken from the same mine. In 1700, 64 furnaces were in blast in the forests of England, producing about 20,000 tons of pig iron annually; in 1788, only 13,000 tons of charcoal iron were made, and 61,300 of pit coal or coke iron; but during 1870, 5,963,515 tons were made with coke and coal. The aggregate steam power of Great Britain in 1860 was 38,635,214 horse power, equal to the productive laboring force of 400,000,000 men, or twice the power of the adult working population of the globe. Nothing more striking or instructive, in regard to the value of coal when utilized by an industrial community, could be stated than this fact.  COAL PLANTS. The vegetation of the globe during the different stages of its formation has undergone very great and evident changes. There is however no reason to doubt that the fossil plants known from the different formations of our earth may all be referred to the great classes of the vegetable kingdom distinguished at the present day, viz.: the thallogens, including such plants as lichens, algae, and fungi; the acrogens, such as ferns and lycopods; the gymnosperms, such as cone-bearing plants and cycads; the endogens, such as palms, lilies, and grasses; and the exogens or dicotyledons, to which belong most of our species of trees. Though the distribution of vegetable fossil remains in these great classes is easily and truly recognized, their relations to genera and species are by no means so certain. What has been said of the formation of coal and its distribution at different geological periods (see ) shows that the examination of the coal floras should not be confined to the vegetation of the carboniferous period. But this limitation is admitted here, for the reason that the fossil flora of the carboniferous is more important in its study and is better known than that of any other epoch, and that its essential characters have been recognized

in the contemporaneous floras over the whole world. Moreover, the essential facts concerning the floras of the periods subsequent to the carboniferous measures have been touched upon already.—The plants of the true carboniferous period are mostly, if not all, referable to the class of the acrogens or vascular cryptogams: ferns, lycopods or club mosses, and equisetaceæ or the horsetail family. A very few species have been considered as belonging to phænogamous gymnosperms: the conifers by 12 species known only by the structure of fossil trunks which represent them; the cycadeæ by so-called species of Noeggerathia, all except one, N. foliosa, of uncertain relation, and by the very common flabellaria or Cordaites borassifolia, mostly represented like Noeggerathia by long ribbon-like leaves only. One stem of it has been found in a silicified state and analyzed by Corda, who considers the plant as allied by its structure to the lycopodiaceous and to the cycadeaæ. The true place of these leaves in the vegetable scale is therefore not positively ascertained.



—Flabellaria borassifolia.

—It is a remarkable fact that trunks of conifers, or those referable to this family by their structure, have been found in the upper Devonian and the subcarboniferous measures of the United States, but that as yet no remains of this kind have been discovered in the true coal measures above the millstone grit. A splendid specimen from the upper Devonian of Indiana, a stem half a foot in diameter, has its surface fluted exactly like that of a calamites, while its internal structure is related to that of araucaria.—The ferns have the most abundant species of the carboniferous period; already more than 600 have been described from this formation. Of these, about 200 species have been found in the coal fields of the United States, more than 50 of which appear to be indigenous or have not till now been observed in Europe. They represent either distinct peculiar types or some analogous ones which are distinguished by less appreciable characters, and which may perhaps be eliminated by comparison with European specimens. As now known, the North American coal flora presents differences evident enough to impress it with a distinct American character, while on the other hand the numerous identical species show it to be as positively representative of the same period as that of the European or other carboniferous floras. The determination of the species of ferns of the coal measures is rendered difficult and somewhat uncertain, at least in regard