April II, 1872] 



NATURE 



471 







iformation, only be treated on purely abstract geological reasoning. 

 Still it is one essentially within the range of inquiry, and the 

 , collateral geological data we possess are sufficient to guide and 

 I direct those inquiries. There are two primary points to be de- 

 i lonnined : — First, how much of the area under investigation re- 

 iniameJ dry land during the Carboniferous period, and was 

 I therefore never covered by Coal-strata. Secondly, supposmg 

 the Coal-strata to have spread over a portion of that area, how 

 much of them escaped subsequent denudation? With regard to the 

 first question it is comparatively easy, where the Pah^ozoic rocks 

 now form the surface, to determine the antiquity of that surface, 

 but %\'here the old rocks are covered by great masses of other 

 j strata it becomes very difficult to determine the original con- 

 ditions. Mr. Godmn-Austen has ingeniously sought to estab- 

 lish the position of the old coast-lmes of the Carboniferous 

 I and other periods, the area of the old coal-growth, and the 

 i great features of the ancient physical geography of this period 

 in Western Europe. I have given more especial attention to 

 ' relations of the Secondary and Pal.vozoic formations to one 

 another and to those points which depend upon physical condi- 

 tions connected with the nature and age of old disturbances and 

 denudations, the direction and position of the great anticlinal and 

 i synclinal lines, to the correlation of certain strata, and the dimen- 

 sions of the overlying strata. 



The great lines of disturbance traversing Central and North- 

 eastern England are subsequent to the Carboniferous period, and 

 the many detached coal-basins separated by the Penine chain 

 and the Derbyshire hills, together with the Mountain Limestone 

 forming those ranges, are held to be portions of one great 

 Carboniferous formation, \\hich, in its entirety, spread from the 

 south of Scotland to central England, and, as we shall observe 

 presently, probably still farther south. This great Carboniferous 

 deposit was originally bounded on the north either by the 

 uplands of the Scottish-border counties, or, possibly, by the 

 Grampians ; on the west by the high lands of Cumberland and 

 Wales ; while on the south we find no old exposed land-surfaces 

 of older Palreozoic age until we reach Brittany and Central 

 France. With respect to the deposits going on during the 

 Carboniferous period in this area, Professor Phillips was the first 

 to show that the lower Carboniferous series puts on, as it trends 

 north fiom Derbyshire, more sedimentary conditions — that the 

 Mountain Limestone there begins to show traces of the proximity 

 to land, which increase rapidly in proceeding northwards, — beds 

 of shale and sandstone and subordinate beds of coal gradually 

 setting in in the limestone series, and increasing in importance 

 as they approach the older border land. In the same way the 

 approach to an old barrier-land on the south and west is supposed 

 by Professor Ramsay to be indicated in the overlying Coal 

 Measures by the increase in number and thickness of the beds of 

 sandstone in the south of the Staffoidshire and Shropshrc coal- 

 field, and Mr. Hull connects that old land with the Cambrian 

 and Silurian rocks of Leicestershire. 



If such were the case, the question arises, did this form a 

 barrier which cut off the Carboniferous deposits from extending 

 over the south of England, or was it only a partial barrier which 

 in no way prevented the extension southward of the Carboniferous 

 rocks ? 



It has been supposed that during the Carboniferous period a 

 spur from the Silurian district of Wales extended eastward from 

 Herefordshire into central England, dividing the coal-fields of 

 Shropshire and Staffordshire from those of Gloucestershire ; and 

 that against this old Silurian tract ihe Coal Measures of South 

 Staffordshire die out. If carried farther eastward it would limit 

 the southern prolongation of the Coal Measures of Leicestershire, 

 and then pass imder the Oolites of Northamptonshire and the 

 Cretaceous series of Norfolk ; and so gieat an expansion has 

 been given it southward, that it would equally exclude the Coal 

 Measures from the area of the south east of England. We have, 

 however, no sufficient evidence of the continuous extension of 

 these old rocks eastward of Staffoidshire. Palrcozoic rocks 

 show, it is true, in Leicestershire ; but there the Coal Measuies 

 wrap round them, and the older rocks seem merely to be an 

 island in their midst. At those spots in the southern counties 

 where they have been proved underground, I imagine they were 

 raised by disturbances of a later date than the Coal Measures, 

 and did not form part of the land surface of the Carboniferous 

 period. As just mentioned, the older Carboniferous rocks show 

 deeper-sea conditions as they trend from north to south, and the 

 same deep-sea conditions existing in Derbyshire are found to 

 prevail in the Mountain Limestone of Belgium, while, at the 



same time, similar slight indications of distant land, in the 

 presence of intercalated shales and imperfect coal, reappear and 

 increase westward in their range into the district of the 

 Boulonnais, in France. There is nothing to show but that the 

 spur of old land stretching eastward from Herefordshire was 

 m.erely a promontory ending in Warwickshire, and rcund w'hicli 

 the Carboniferous sea passed and extended southward uninter- 

 ruptedly to Belgium and the north of France, and westward to 

 Somersetshire and South of Wales, spreading over all this wide 

 area first the Mountain Limestone and then, in due order, the 

 Coal Measures. Of the existence of these formations over the 

 south-western and south-eastern portions of this area we have 

 proof in Wales, Somersetshire, and Belgium. The intermediate 

 area is covered by Jurassic, Cretaceous, and Tertiary formations, 

 which hide from us the older rocks whose position it is our 

 object to determine. 



Just as with the disturbance which at a later period caused the 

 Mountain Limestone of the Penine chain to break through the 

 great expanse of Coal Measures originally spread over the central 

 and northern counties of England, and brought up to the surface 

 the disturbed and disjointed coal-strata, of which, after subse- 

 quent denudation, we have the isolated portions remaining in the 

 existing coal-fields, so was the area of Southern England 

 traversed by the earlier axis of Palaeozoic rocks of the Ardennes 

 and Mendips, bringing up the Coal Measures in like manner 

 along their northern flanks in separate basins and troughs, some 

 of which are uncovered by newer strata, while other basins not 

 exposed on the surface may still possibly exist beneath the newer 

 strata of the south-east of England. They have in fact been 

 proved to exist under considerable portions of those newer strata 

 of north-western France and of Belgium, and under some of the 

 older Secondary strata in the south-west of England. 



The probable continuation of this great range of PaU-eozoic 

 rocks from the Rhine to South Wales, passing underground in 

 the south of England, was shadowed out by Buckland and 

 Conybcare in 1826, commented on by Dufresnoy and Elie de 

 Beaumont in 1841, by M. Meugy in 1S51, and more fully 

 investigated and discussed by Mr. Godwin-Austen in 1855. 

 These views having been controverted, the subject was fully dis- 

 cussed by the Commission, and again in the separate report 

 drawn up by myself. 



All geologists are agreed upon the age of this great east-and- 

 west axis of disturbance. It took place after deposition of the 

 Coal Measures, and before the deposition of the Permian strata. 

 Its effects, all through its range, are singularly alike. It was not 

 so much a great mountain-elevation, as a crumpling up and 

 contortion of the strata for a breadth of many miles, and along 

 a length of above eight hundred miles. The Silurian and 

 Devonian rocks are thrown up by it into a number of narrow 

 anticlinals, and the flanking coal-strata are tilted, turned back 

 on themselves, squeezed and contorted in the most remarkable 

 manner, — the same type of disturbance being apparent whether 

 in Westphalia, Belgium, France, Somerset, or Pembroke. These 

 great flexures have also resulted in throwing the Coal Measures 

 into deep narrow troughs, having a length of many miles and a 

 width of but very few. 



In France, these disturbed old strata are covered transgressively 

 by Jurassic, Cretaceous, and Tertiary strata, and in Somerset by 

 Permian, Liassic, and Jurassic strata ; they sink beneath the 

 Oolites at Frome, and reappear in Belgium from beneath the 

 Cretaceous strata. What becomes of them in the intermediate 

 area ? It is not to be supposed that a line of disturbance of 

 such great magnitude could have been intermittent. The coal- 

 trough has, in fact, been followed from near Charleroi, where it 

 passes under the Cretaceous and Tertiary strata, to Mons, 

 Valenciennes, and Bethune, a distance of eighty-six miles. Along 

 the whole of this fine, the Chalk and overlying beds extend, with 

 a thicknes~ varying from 500 to 900 feet around Mons, decreasing 

 to from 250 to 300 near Valenciennes, and inert asing again 

 towards Bethune. At Guines the Chalk was found to be 

 670 feet thick, and at Calais 762 feet. On the other side, the 

 coal-trough of Somerset passes eastward under the older 

 Secondary rocks, which in their turn pass under the Cretaceous 

 and Tertiary strata of Wdtshire ; but no attempt has been made 

 to foUowCoal Measures leyond a distance of six miles from their 

 outcrop, where the overlying strata have been found to attain a 

 thickness of about 450 fest. 



The original supposition that the Secondary strata maintained, 

 in the main, their regular sequence, and, to a certain extent, their 

 thickness over large areas has long been proved to be erroneous ; 



