372 COAL — EEECT FOSSIL TEEES. [Ch. XXIV. 



Coal, how formed — Erect trees. — I shall now consider the mannei in 

 which the above-mentioned plants are imbedded in the strata, and how 

 they may have contributed to produce coal. Professor Goppert, after 

 examining the fossil vegetables of the coal-fields of Germany, has 

 detected, in beds of pure coal, remains of plants of every family hitherto 

 known to occur fossil in the coal. Many seams, he remarks, are rich 

 in Siffillarice, Lepidodendra, and Stigmarice, the latter in such abun- 

 dance, as to appear to form the bulk of the coal. In some places, almost 

 all the plants were calamities, in others ferns.* " Some of the plants of 

 our coal," says Dr. Buckland, " 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 distances 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 sev- 

 eral stems of large trees, standing close together in their native place, in 

 a quarry of sandstone of the coal formation."! 



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

 the coal-field of Lancashire, where it is intersected by the Bolton rail- 

 way. 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 im- 

 bedded 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 ascertained 

 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 Lejridostrobus variabilis was discovered inclosed in nod- 

 ules 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. 363). 

 The exterior trunk of each was marked by a coating of friable coal, va- 

 rying from one-quarter to three-quarters of an inch in thickness ; but it 

 crumbled away on removing the matrix. The dimensions of one of 

 the trees is 15 h feet in circumference at the base, *l\ 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 through- 

 out ; for solid dicotyledonous trees, when prostrated in tropical forests, 

 as in Venezuela, on the shore of the Caribbean Sea, were observed 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 



* Quart. GeoL Joura, vol. v., Mem., p. 17. 

 + Anuiv. Address toGeol. Soc, 1840. 



