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ferns, gigantic equiseta, and other plants belonging to the herba- 

 rium of the ancient coal-fields, grew on the land, and were some- 

 times swept down into the sea, before the elevation of the grey- 

 waeke chains of one portion of the British Isles — that in after times, 

 the same families of plants were swept down into the sea, in immense 

 abundance, and spread out, here and there, in beds alternating 

 with mud, sand, and banks of zoophytes and sea-shells, during the 

 whole period of the deposit of mountain-limestone, from its beginning 

 to its end — lastly, that these mechanical accumulations continued 

 to go on in shallow seas and estuaries (and perhaps also in inland 

 lakes), till the whole process of degradation was interrupted by the 

 elevation of the carboniferous chain, producing the enormous breaks 

 and dislocations above described, and succeeded by the conglomerates 

 of the new red sandstone. 



Before I leave this subject, 1 may notice a work, just published by 

 Mr. Witham of Edinburgh, containing many beautiful illustrations of 

 the internal structure of fossil plants derived from the old coal-fields 

 of the Tweed, and from various parts of Scotland. By submitting 

 extremely thin, polished slices of these fossils to microscopic observa- 

 tion, he has been enabled to detect the minutest traces of organic 

 texture ; and he has proved the existence of so large a number of 

 phanerogamic plants, in the lowest part of the carboniferous series, 

 as greatly to modify one of the positions laid down in the Prodromus 

 of M. Adolphe Brongniart. 



A paper, by Dr. Buckland and Mr. de la Beche, on the Geology of 

 Weymouth and the adjacent parts of the coast of Dorsetshire, brought 

 before us all the secondary deposits of this island, from the lower divi- 

 sion of the oolites to the chalk. It is so rich in its details, and adorned 

 with such admirable illustrations, that the structure of the whole 

 region, though crowded with formations, dislocated, contorted, and 

 traversed by enormous and complicated faults, will hereafter be 

 comprehended at a single glance ; and the country will be visited 

 as classic ground, where the most perfect types of our newer secon- 

 dary groups may be studied under every variety of position and 

 combination. Without attempting to follow the authors in their de- 

 scription of twelve of these successive groups, I may be permitted 

 to remind you of the extraordinary bed between the Purbeck and Port- 

 land formations (first noticed by Mr. Webster), containing silicified 

 trunks of coniferous trees and stems of Cycadeoidese. From this 

 paper, we learn, that these trunks lie partly sunk in black earth, 

 like fallen trees in a peat-bog, and partly imbedded in the incum- 

 bent limestone ; and that many of the stumps remain erect, with 

 their roots in the black soil, and their upper portions in the lime- 

 stone : and from these facts the authors conclude — that the surface 

 of the Portland rock was once dry land — and that on it grew a 

 forest containing plants of a tropical form — that this forest was 

 submerged under the waters of an estuary or a lake, but with a 

 movement so gentle, that neither the plants nor the soil were swept 

 away — that upon this ancient forest were accumulated the mixed 

 formations of the Wealds, not much less than 1000 feet in thickness — 



