14 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 2, 



abounding in Stigmaria, but having no beds of coal resting on them. 

 In two instances, beds of bituminous limestone constituted Stigmaria 

 understones, and the rootlets of Stigmaria are seen intermixed with 

 well-preserved shells of Ci/pris and Modiola. These beds in their 

 recent state must have been extremely rich marly soils. Nearly 

 one half of the underclays have no coal resting on them, or have 

 mere films of coaly matter intermixed with bituminous shale. Most 

 of these beds, however, support either erect plants, or shales and 

 sandstones filled with prostrate trunks of Sigillaria and other trees, 

 remains of which are also found plentifully in some of the thinner 

 coals. From this we may infer with certainty that the growth of a. 

 bed of coal usually occupied a much longer time than that required 

 for the growth of a forest oi Sigillaria, and that the growth of such a 

 forest was the almost invariable preparation for the formation of 

 coal ; but that in many instances, especially in the more light and 

 sandy soils, no accumulation of coaly vegetable matter occurred, such 

 accumulations occurring most frequently at the surface of beds of 

 clay, and more especially of those which were of no great thickness 

 and rested on sandy subsoils. The conditions, therefore, which 

 favoured the accumulation of coal were very similar to those which 

 in modern times occasion the formation of peaty matter in swamps 

 and bogs. 



All the underclays have the bleached appearance seen in the sub- 

 soils of modern swamps, and no doubt from the same cause *, — the 

 removal or change of the ferruginous colouring matters by the 

 deoxidizing and solvent agency of decomposing organic matter and 

 organic acids. A few of them are traversed by numerous slickenside 

 fissures, probabiv in consequence of the movement of their mass 

 imder pressure, as the roots which they contained became softened or 

 disappeared through decay. To this cause also, as well as to the 

 penetration of roots, and to atmospheric influences, may be due the 

 removal of the lamination which many of them, especially those 

 resting on laminated shales, in all probability originally possessed. 

 Few of the underclays contain much vegetable matter, except in the 

 form of Stigmaria-xootB and irregular coaly veins, which may have 

 been the roots of other trees. It is, however, observable that the 

 Stigmarice and their rootlets often penetrate to considerable depths to 

 reach coals, or other beds rich in organic matter. With the ex- 

 ception of the bituminous limestones already mentioned, the lowest 

 underclay in the "Queen's Vein" is richer in organic matter than 

 any other in the section. 



There is no distinct evidence in this section of the formation of 

 coal from drifted materials. Two of the three coals not observed to 

 rest on (S^^/f/mrtr/a-underclays consisted almost entirely of leaves of 

 Poacites, which may have grown on the spot, and could scarcely 

 have drifted far. There are two instances of coals based on Stigmaria- 

 underclays which became submerged in such circumstances as to 

 permit Spirorhis and scales of Fishes to be intermixed with the 

 vegetable matter. This does not, however, necessarily imply driftage. 

 * [See also Report Brit. Assoc. 1853, Trans. Sect.] 



