480 FOSSIL TREES OF COAL. ■ [Ch. XXIV. 



the coal. In some places, almost all the plants were calamites, in 

 others ferns.* " Some of the plants of our coal," says Dr. BncMand, 

 "grew on the identical banks of sand, silt, and mud which, being now 

 indurated to stone and shale, form the strata that accompany the coal ; 

 whilst other portions of these plants have been drifted to various dis- 

 tances from the swamps, savannahs, and forests that gave them birth, 

 particularly those that are dispersed through the sandstones, or mixed 

 with fishes in the shale beds." " At Balgray, three miles north of 

 Glasgow," says the same author, "I saw in the year 1824, as there 

 still may be seen, an unequivocal example of the stumps of several stems 

 of large trees, standing close together in their native place, in a quarry 

 of sandstone of the coal-formation." f 



Between the years 1837 and 1840, six fossil trees were discovered 

 in the coal-fields of Lancashire, where it is intersected by the Bolton 

 railway. They were all in a vertical position, with respect to the plane 

 of the bed which dips about 15° to the south. The distance between 

 the first and the last was more than 100 feet, and the roots of all were 

 imbedded in a soft argillaceous shale. In the same plane with the 

 roots is a bed of coal, eight or ten inches thick, which has been found 

 to extend across the railway, or to the distance of at least ten yards. 

 Just above the covering of the roots, yet beneath the coal-seam, so 

 large a quantity of the Lepidostrohus variabilis was discovered enclosed 

 in nodules of hard clay, that more than a bushel was collected from the 

 small openings around the base of the trees (see figure of this genus, 

 p. 471). The exterior trunk of each was marked by a coating of friable 

 coal, varying from one quarter to three quarters of an inch in thick- 

 ness ; but it crumbled away on removing the matrix. The dimensions 

 of one of the trees is 15^- feet in circumference at the base, 7-J-feet at 

 the top, its height being 11 feet. All the trees have large spreading 

 roots, solid and strong, sometimes branching, and traced to a distance 

 of several feet, and presumed to extend much farther. Mr. Hawkshaw, 

 who has described these fossils, thinks that, although they were hollow 

 when submerged, they may have consisted originally of hard wood 

 throughout ; for solid dicotyledonous trees, when prostrated in tropical 

 forests, as in Venezuela, on the shore of the Caribbean Sea, were ob- 

 served by him to be destroyed in the interior, so that little more is 

 left than an outer shell, consisting chiefly of the bark. This decay, 

 he says, goes on most rapidly in low and flat tracts, in which there is 

 a deep rich soil and excessive moisture, supporting tall forest trees and 

 large palms, below which bamboos, canes, and minor palms flourish luxu- 

 riantly. Such tracts, from their lowness, would be most easily submerged, 

 and their dense vegetation might then give rise to a seam of coal.| 



In a deep valley near Capel-Coelbren, branching from "the higher 



* Quart. Geol. Journ., vol. v., Mem., p. 17. 



f Anniv. Address to Geol. Soc, 1840. 



% Hawkshaw, Geol. Trans., Second Series, vol. vi. pp. 173, 177, pi. 17. 



