114 



FORMATION OF COAL. 



The terrestrial and marsh plants that accompany coal, and of 

 which it was probably formed, might flonrish between these succes- 

 sive inundations, their growth being sufficiently rapid to form a thick 

 bed of vegetable matter in a short period ; for, as they had not the 

 ligneous structure of wood, their decomposition by vegetable fermen« 

 tation might speedily be effected. Should it be objected, that some 

 of the coal beds are from nine to thirty feet in thickness, and that a 

 mass of vegetable matter, sufficient to form such beds, could not be 

 collected in one season, it is sufficient to reply, that we know not the 

 duration of the periods during which vegetation might proceed with- 

 out interruption ; and it deserves particular notice, in relation to this 

 subject, that all thick beds of coal are divided into several minor 

 strata, and have frequently thin strata of shale, clay, or sandstone 

 between them, but they are called by the miners one bed, as the coal 

 can be all got at the same level. The Staffordshire coal stratum, 

 which is thirty feet thick, is divided into thirteen minor strata by 

 seams of clay, &c. ; and the thirteen feet bed of coal at Ashby 

 Wolds is composed of several seams of different qualities. 



Very thin seams of coal sometimes alternate with the shale lying 

 between two large beds of coal. I have on the table before me, a 

 mass from the Dudley coal-field, in which part of two beds of coal 

 are separated by a stratum of indurated clay or shale, about two 

 inches in thickness ; this stratum of shale contains more than twenty 

 seams of coal, none of which exceed the thickness of a wafer, but 

 they are distinctly separated from each other by seams of shale. 

 These thin seams of coal and shale, were probably formed by alter- 

 nate depositions of leaves or minute aquatic plants, and of earthy 

 particles forming layers of clay or sand. These are circumstances 

 which appear to me to prove, that the formation of the coal strata 

 was effected more rapidly than those geologists have hitherto been 

 willing to admit, who have only examined coal mines, seated in an 

 easy chair in their studies. I will first advert to the state in which 

 fossil vegetables are found in coal mines, and shall give a section of 

 a coal mine, which I examined in 1811, belonging to the late Mar- 

 quis of Hastings. It is remarkable for the frequent repetition of the 

 same series of strata, of precisely the same quality and thickness ; 

 proving a periodical recurrence of the conditions under which they 

 were formed. 



Vertical stems not unfrequently occur in coal-fields ; but, from 

 the mode of working or sinking for coal, it is seldom that they can 

 be seen in that position. Where a stone quarry is open to-day in 

 coal strata, and uncovers a considerable face of rock, there we may 

 sometimes meet with fossil plants in their original position. In 1819, 

 I had an opportunity of examining Burntwood quarry, at Allhouse, 

 near Wakefield, in Yorkshire, at which time there were numerous 

 vertical stems in strata of sandstone. One stem which I measured 

 in the quarry was nine feet in length, and ten inches in diameter ; 



