COA L. 311 tables resembling equisetums, accompanied by others analogous to ferns and lycopodiums, and, as it is thought, to palms ; with some which appear to pos sess no exact living analogies. The fluted and the scaly stems and trunks, distinguished by the terms Lepidodendron and Syringodendron, are the most re markable, as they are the most obscure. The genera seem to be very limited, as far ns they can be deter mined from such imperfect specimens ; but it is ima gined that the species exceed three hundred, or ap proach to four. How far they may he considered as tropical plants, I have already had occasion to en quire ; while, when it is said that at this period of the earth no dicotyledonous plants existed, and that the chief vegetable creation was a cryptogamous one, we cannot but be surprised at the minute progress which philosophy has hitherto made among the cultivators of this science. The Geologists of a future world, whose researches may begin and end in a rock formed out of the Sheppey clay, will perchance determine, under similar reasoning powers, that the world pro duced no plants but hazels. In the sandstones, the most frequent vegetable ap pearance is that of concretions of sand bearing the impression of the trunks just noticed ; and, in these cases, while the woody matter of the tree has disap peared, the bark is sometimes converted into coal. These are often compressed, as if by the superincum bent weight, and are also recumbent ; but, there have also been found remains of trees similarly changed, in an erect position, with the branches attached. Such are the organic appearances connected with coal ; all of them bespeaking a terrestrial, not a sub marine origin, for the general series in which it is found. Their aquatic nature equally indicates the