TRANSACTIONS OF THE SECTIONS. 49 



and violent currents. The absence or rarity of distinct traces of fructification was 

 also an argument in favour of their being drifted; as in the oolitic deposits of Gris- 

 thorpe-bay, which afforded evidence of comparatively tranquil deposition in fresh 

 water, the fronds were not merely grouped together by their rhizomas, but afforded 

 frequent indications of fructification. The prevalence of fine-grained shales imme- 

 diately over coal seams was, in the author's opinion, highly unfavourable to the 

 theory which accounted for the origin of coal by subsidences ; for if a sudden subsi- 

 dence had taken place, a deposit of water-worn pebbles would have been strewed over 

 the coal, indicating the violent action of aqueous currents; and if the submergence 

 were slow and gradual, the plants, as before argued, would be found much more per- 

 fect, as any currents sufficient to tear up the vegetation would also strew the surface 

 with detritus ; the absence of unconformability in the members of the coal-measure 

 was also hostile to the idea of partial depressions. The argillaceous partings, which 

 constantly occurred in coal seams, also favoured the supposition of a considerable 

 amount of drifting. Mr. Williamson concluded by attempting to explain the upright 

 position of the trees at Dixon-fold on the Bolton Railway, without having recourse 

 to the supposition that they grew on the spot ; one of these trees was described by 

 Mr. Bowman as having its base raised fifteen inches above the surface of the coal, the 

 roots only being in contact, which Mr. Williamson considered could not be accounted 

 for by any condensation of the vegetable remains afterwards constituting the coal 

 seam. One of the largest of these trees presented no trace of roots, which were 

 more likely to be preserved than any other portion. As to their erect position, he 

 considered the weight of their strong branching roots would be sufficient to main- 

 tain them erect in water until a deposit of sediment and drift should accumulate 

 round their bases ; whilst the absence of trunks inclined at various angles might be 

 accounted for by pressure, which would soon reduce all that were not absolutely 

 vertical to a horizontal position. One of the greatest objections in the author's 

 mind to the drift theory was, the great extent and uniformity ofsome of the thin seams 

 of coal, especially in the lower measures; he thought, however, the accumulation of 

 vegetable remains in which these seams originated might have been as great as in 

 many of the larger coal seams, but that in the chemical changes which they had un- 

 dergone, a larger proportion of the gaseous elements had escaped, leaving the 

 mass both thinner and less unequal in thickness than at first. He also mentioned the 

 laminated appearance of peat-bogs in the vicinity of Manchester, as exhibiting by 

 its illustration of the structure of coal a fact favourable to the hypothesis which he 

 had been combating; and stated that as the true explanation of the phaenomena was 

 the only end he sought, he was ready to accept that view if the difficulties attend- 

 ing it could be explained on rational grounds. 



On the Great Lancashire Coal Field. By E. W. Binney, Sec. Geol. Soc. 

 of Manchester. 



This carboniferous deposit, generally known as the Lancashire Coal Field, occu- 

 pies the chief part of the southern division of the county of Lancaster, and extends 

 into portions of the adjoining counties of Chester, Derby and York, in a line from 

 near Macclesfield to Colne it ranges about 46 miles due N. and S., and from Tarbock 

 to Todmorden about 40 miles from W.S.W. to E.N.E. It commences with the 

 lower millstone grit, and extends upwards into the limestone of Ardwick, near Man- 

 chester, now generally considered the highest portion of the coal measures hitherto 

 observed in England. The author divides this series into three groups in descending 

 order : — 1. The Manchester coal-field, containing the limestone of Ardwick, and the 

 isolated coal-measures of Clayton and Bradford, near Manchester, occupying the 

 low tract of country adjoining the new red sandstone plains.— 2. The middle field, 

 comprising the thick coal seams of Poynton, Ashton, Middleton, Worsley, Wigan, 

 &c, occupying the rising ground between the new red sandstone plains and the 

 higher parts of the country, and containing the richest portion of the field. — 3. The 

 lower coal-seams, found in the elevated parts of the country, along the sides of the 

 Penine chain, and the moorlands of the northern parts of Lancashire ; comprising 

 those of Whaley Bridge, Mellor, Glossop, Rochdale, Todmorden, Colne, Blackburn, 

 Chorley, &c. — seams of no great thickness, but valuable from their quality and po- 

 sition, and remarkable from their adjoining shales containing remains of the genera 

 IW2. a 



