450 



NATURE 



\Sept. 4, 1879 



even tracw of tome of the riven of the age are to be found 

 l>rencliing the neami. The more the lubject, oommonplace as it 

 may be thoucht, U conHldered, the more aatonlKhini; cloea it 

 become, for tne regularity of the nubiiiJence and its nmuuiit iiiuiit 

 liave l<ept pace with the thiclcneiia of the accumulating deposits. 

 That there were many long intervals of quietude in the earth's 

 crust may be ijlcaned, not only from the tliickne.ss of many coal 

 Mama, but aluo from the tubacrial dcjiudatioii which occurred, 

 For instance, hleh up in the series in this di .trict, is a mats of 

 red sandstone which covers the denuded middle measures beneath ; 

 and this red rocli of Rotberham, the result of coal measure 

 denudation and removal, accumulated during the early days of 

 the upper coal measures, for it is lower in the geological series 

 than some memljcrs of the uppermost coal measures. 



Dcfore the close of the age, marine conditions occurred in the 

 rocli, and a limestone with gonlatitei was formed ; but still coal 

 seam fornmlion j^nceeded until a totally dilTerent series of crust 

 movements commenced in this country, 



'I'he (IcxurcH which were produced nt the close of the carboni- 

 ferous n^e, had their long axes east ami west ; tliey sunTurcd 

 denudation and on the worn edges of their strata the "used-up 

 carboniferoui " — the lower Permian, Ksewlierc, resting appa- 

 rently and often really conform.ably on tlie carbimifcrous strata, 

 the iV-rmian'. acriiimifatcd until great north and south curvatures 

 ueouueil imil in'oilnccd the rcnnine cliain. 



The deiuiil.ilioii of the aniiclinal or upward curves of the north 

 and soulli llnxuics profjiesseil, and llie coal measures, once 

 continuous aeioss ICiii^land, were worn off along the back-l)one 

 of the coniilry and from off tlie east ami west ridges also. Vast 

 ns was thedeslruclion anil reinuval, there was still more compen- 

 sation in nature, lor faulting occnrred on a large scale, and the 

 measures were in many places sunken down below the level of 

 possible subacrlal ilcnudalion. It is to tlic pre- and post- Permian 

 crust movcinenis in prixluclng basins and in uptllling the formerly 

 horizontal seams, and to the subsi-cjucnl faulting, that we owe 

 the prcservailon and the possibility of reauhing and working 

 much of the coal of this country. 



It appears that the position of this town refers quite as nuich 

 to some remarkable faults, and the results of the post Permian 

 uptilling, as to llic presence of the river Don. Two important 

 lines of fault run almost parallel, the one traveraing the centre of 

 Shellicid, ami the other being to the north of the outcrop of the 

 Sllkstone coal. They pass in a north-easlerly direction, 

 and the country between them is jnnch broken. Moreover, 

 by a combination of the results of nptilt and faulting, the 

 strike of important coal scams has been so altered that they 

 encircle the town on the south, west, and north. The mineral 

 products have thus been brought wiiliin the reach of lliise by 

 whose Industry this town has increased in size and population. 



With regard to the lilhology of some of the great scries just 

 mcniioned, it may be suggested that (he condition umler which 

 the beautiful limeatoneaof the Avon, and the dark, shaly, nmddy, 

 calcareous deposit* of the corres|>ondijig age aceunudated in 

 Scotland, were very different. The stone in the southern example 

 la many coloured and Is nearly an organic deposit, whilst the 

 shaly strata of the northern series have crowds of calcareous fossils 

 \\\ ilicm. Uemovo the sbaly substance, however, and consider 

 and compare the fossils of both localities, and no satisfactory 

 distinction can be drawn between the depths at which they may 

 have accunnilated. 



lloih depr)siis contain crinolda, polvzoa, brachiopoda, and 

 simple an 1 eonqiouud hydro-oorals. The tame occur in the 

 llmcHtones to the north of the central barrier, which are inter- 

 mediate In the arenaceous condition between tho»e just mentioned. 

 It is admitted that the mineral condition of the original deposits 

 has altered, and it is possible that much impurity may have been 

 removed l)y percolating oarl>onated waters, from tlie purest of the 

 llmestonea. And, Indeed, unless this la credited, it is impossible 

 to compare some of these old marine aedlmenta with any now 

 fornung on the floor of the lea. AH the known calcareous sea 

 Moor deposits contain a very considerable iiercentage of silica 

 and oilier matters, and if the carboniferous limestones were ever 

 in the condition of modern deep-sea ooze, in order that they 

 should have looked like the chalk they must have lost In some 

 manner or other more than ^5 per cent, of impurities. So 

 far as T can underHtand, much of the carboniferous limestone 

 may have aeeumulated at no very great depth and on banks 

 within the scour of currents, and their prevalence would account 

 far the comparative absence of sandy sediments In some situa- 

 tions. No traces of atoll formation exist. 



With regard to one or two late discoveries relating to the 

 organic remains of the carboniferous limestones, it is necessary 

 to refer you to Moseley's important work amongst the 'I'abulata. 

 'I'licse must now be removed from the true stony corals, and ]■ 

 some will be relegated to the llydrozoa, and otlicrs to the 

 Alcyonaria, It is a fact of great interest that .Sorby shoukl 

 have noticed that whilst the modern true corals are built up of 

 carbonate of lime in the form of arragonite, the great tabulated 

 forms of old are composed of calcile, 



(^uitc lately Mr, Jlusk has been investigating the large polyzoa 

 of the genus Heteropora, and I saw, under his manipulation, 

 that this recent and Crag group, with strong paUeozoic affinitic!', 

 la so constructcil that the l>ranching tubular organisms of the 

 oldest rocks with jierforations in their walls and labidie must be 

 included amongst species of genera closely allied to it, 



A host of ill-deHncd tubular forms, such as the Stenoporrc, 

 will thus find a final zoological resting- |)lacc. 



The arenaceous aeries of the carboniferous formation in 

 I'Ingland are not less wonderful than the calcareous. They thin 

 out very rapidly from 10,000 feet in the liurnlcy district to 

 100 close to the central barrier in Leicestershire, and it would 

 appear that the sea drift was from the present region of the 

 North Atlantic, along the shores of the swampy coal plant- 

 growing-land. 



Tlie arenaceous deposits to the south of the central barrier 

 have the same general relation as those to tli ; north, and 

 the grits of the Welsh and Dristol coal-fields are siliciou', 

 anil were in all probability derived from the .Silurian and old 

 red rocks to their north-west. The culm measures of .Somerset- 

 shire and Devonshire — those thick deposits with impure thin 

 coals with limestones towards the bases —are of the age of 

 the upper parts of the carboniferous limestones and of the grits 

 of the central area. The evidences in this age of the denudalio:i 

 of granite and other silicious lands, and of more or less distant 

 diU'usion of the sediment, extend far and wide from the United 

 Kingdom, a belt of similar rocks being found in soiuh-westerii 

 and central Kurojje. It is, moreover, very ]irobable that the 

 upper Vindhyan rocks of Ilindostan, those fine sandstones and 

 grits which have yielded the liuilding-stones to the great 

 Uangetlc cities, are of the same relative age (or slightly older). 

 at the strata of which so many Yorkshire towns are mainly 

 built. 



Whence came the thousands of feet of the sands and shales of 

 the coal measures ? is as yet a question which cannot be 

 answered. It appears that veiy widely distributed deposits of 

 the same kind are comiJaiatively rare amongst them, and that 

 most of the organic deposits, as well as the inorganic sedi- 

 mentary, do not exiend over great breadths, but are more or Ics 

 leiiticular in shape, or thin imt or become changed in tlieir 

 lilhology. This fact and Sorby's suggestion that the currenis 

 which (leposited the strata had not any definite course rather 

 tend to the belief in the former presence of a vast delta during 

 that ancient aspect of nature. It is certain that some of the 

 vegetation which subse<iuently bectime cixil, and many feet of 

 the roof above, were not always formed with great .sluwness, fori! 

 stumps and trunks of trees have been foun<l standing where theyjl 

 grew, with tlieir roots in their under-cliiy and their stems wrappedjl 

 roun i with coal, and the shale and gravel above. MoreovcrJ" 

 in some ]ilaces, a scries of these interesting relics exists, one stfl 

 being placed aliovc the others. J 



Willi regard to the coal Itself, varying as it does in its physical 



fieculiaritics, all that has an undcr-clay grew as vegetation oH;| 

 and. It is at present rather difficult to believe that where »l\ 

 coal-seam is found upon a liard silicious bed without n vestige oBl 

 cUy or of old soil, its plants were rooted there. Hut the stigJl 

 niarian roots arc not unfreijuent in the ganister, and at the pre»!| 

 sent time a peculiar vegetation is growing on the grits to the wesfc| 

 of this town with a very small amount of humus intervening. 

 Some coal seams, especially the cannels, would appear, however, 

 not to have been i)roduced by plants which grew on the rocks 

 beneath, and they are the result of vegetation drifting and 

 becoming waler-loggcd. 



In rcllecting upon the history of those carboniferous deposits 

 in relation to the subsequent great changes in the physical geo- 

 graphy of the earth, the idea that geological histories repeat 

 themselves does not obtain that importance with which it is 

 credited in relatiim to human events. It is true that there were 

 important triassic, oolitic, wealden, neocomian, and tertiary 

 lands, whose vegetation has been metamorphosed into a kind of 

 coal. But the wonderful depth and the extraordinary vertical 



