In the words of Professor Ansted, we add: “This account of the coal-beds gives a very imperfect notion of the quantity of vegetable matter required to form them; and, on the other hand, the rate of increase of vegetables, and the quantity annually brought down by some great rivers both of the eastern and western continents, is beyond all measure greater than is the case in our drier and colder climates. Certain kinds of trees which contributed largely to the formation of the coal, seem to have been almost entirely succulent,[59] and capable of being squeezed into a small compass during partial decomposition. This squeezing process must have been conducted on a grand scale, and each bed in succession was probably soon covered up by muddy and sandy accumulations, now alternating with the coal in the form of shale and gritstone. Sometimes the trunks of trees caught in the mud would be retained in a slanting or nearly vertical position, while the sands were accumulating around them; sometimes the whole would be quietly buried, and soon cease to exhibit any external marks of vegetable origin.”[60] There are various kinds of coal on which we may bestow a few words. There is _anthracite_, or non-bituminous coal, and which, therefore, burns without flame or smoke, and is extensively used in malting; and _sea-coal_, which is highly bituminous, and which gives forth so much flame and smoke, that in the good old times of 1306, Parliament forbad its use in London by fine and by demolition of all furnaces in which it was burnt, because “this coal did corrupt the air with its great smoke and stink;” and _cannel-coal_, the etymology of which, they say, is firm the word candle, because in many parts of Lancashire the poor use it in place of oil or tallow for lights; and _jet_, sometimes called black amber, which in France employs about 1,200 men in one district, in making earrings, rosaries, and other ornaments; and last of all, there is wood passing into coal called _lignite_, found only in the Devonshire culms. Having thus glanced at the natural history and varieties of coal, we may here try and realize the flora of the carboniferous era. An examination of the fossils of this period enables us to come to undoubted conclusions concerning the trees and plants of that era, so that it is no mere dream to look upon a picture like the following, and see in it a landscape of the coal-forming time of the British islands. [Illustration: FLORA OF THE COAL MEASURES RESTORED. ]