July 31, 1890] 



NATURE 



319 



speakers, at which the following resolution was passed : 

 " That this meeting of the inhabitants of Chelsea, having 

 heard that there is a probability of the old physic garden 

 on the Chelsea Embankment being no longer kept up by 

 the Apothecaries' Company, considers that every effort 

 should be made to preserve it for the public as an open 

 space." Under these circumstances we wish to put in a 

 plea that the claims of the London students of systematic 

 botany and materia medica should not be overlooked, or 

 the scantiness of their opportunities for the study of living 

 plants forgotten. 



THE SEARCH FOR COAL IN THE SOUTH OF 

 ENGLAND.^ 



(i) 'T^HE bare facts of the recent discovery of coal- 

 J- measures at Shakespeare Cliff, near Dover, have 

 been published in the press, and the full account cannot 

 be written till the completion of the inquiry which is now 

 going on. It is, however, not unfitting that the bearing 

 of the discovery on the general question of the existence 

 of workable coal-fields in Southern England should be dis- 

 cussed within these walls, not merely on account of its 

 general interest, but because it naturally follows the paper 

 read by Mr. Godwin- Austen before the Royal Institution, 

 in 1858, " On the Probability of Coal beneath the South- 

 Eastern parts of England." In 1855 he had placed before 

 the Geological Society of London the possibility of the 

 existence of coal in South-Eastern England at a workable 

 depth. In the tw.o years which had, elapsed, "the possi- 

 bility " had grown in his mind into the " probability," and 

 in the thirty-two years which have passed between the 

 date of the paper before this Institution and the present 

 time, "the probability" has been converted into a 

 certainty by the recent discovery at Dover. In this com- 

 munication, the lines of the inquiry laid down by Godwin- 

 Austen will be strictly followed. We must first examine 

 the conditions under which the coal-measures were 

 accumulated. 



(2) The seams of coal are proved, by the surfaccrsoil 

 traversed by roots and rootlets, to which in some cases 

 the trunks are still attached, to have been formed in situ 

 by the growth and decay of innumerable generations 

 of plants {Lepidodendra, Sigillaria, Calamites), pines 

 {Trigonocarpa, Dadoxylon, Sternbergia) allied to 

 Salisburia, and a vast undergrowth of ferns, all of 

 which contributed to form a peat-like morass. Each 

 seam represents an accumulation on a land-surface, just as 

 the sandstones and shales above it point to a period of 

 depression during which sand-banks and mud-banks were 

 deposited by water. The fact also that the coal-seams in 

 a given sinking are parallel, or nearly parallel, implies 

 that they were formed on horizontal tracts of alluvium, 

 while the marine and fresh-water shells in the associated 

 sandstones and shales prove that they were near the level 

 of the sea, or within reach of a mighty river. This tract 

 of forest-clad marsh-lands, as Godwin-Austen and Prest- 

 wich have pointed out, occupied the greater part of the 

 British Isles, from the Highlands of Scotland southwards 

 as far as Brittany, and eastwards far away into the valley 

 of the Rhine, and westwards over the greater part of 

 Ireland. It swept round the hills of South Scotland and 

 the Lake district and the region of Cornwall. It occupied 

 a delta like that of the Mississippi, in which the forest- 

 growths were from time to time depressed beneath the 

 water-line, until the whole thickness of the coal-measures 

 (7200 feet thick in Lancashire, 7600 in South Wales, and 

 8400 in Somersetshire) was built up. After each depres- 

 sion the forest spread ag^in over the sand and mud of the 

 submerged parts, and another peat-layer of vegetable 



I Friday Evening Lecture delivered at the Royal Institution on Jt 

 Prof. W. Boyd Dawkins, F.R.S. 



;6, by 



matter was slowly accumulated above that buried beneath 

 the sand and mud. The great extent of this delta implies 

 the existence of a large river draining a large continent, 

 of which the Highlands of Scotland and the Scandinavian 

 peninsula formed parts, and which I have described 

 before the Royal Institution under the name of Archaia. 



(3) At the close of the Carboniferous age, this vast 

 tract of alluvium was thrown into a series of folds by 

 earth-movements. These have left their mark in the 

 south of England and the adjacent parts of France, in the 

 anticline of the English Channel, the syncline of Devon- 

 shire, the anticline of the Mendip Hills and of the lower 

 Severn, and the syncline of the South Wales coal-fields. 

 These great east and west folds have been traced from the 

 south of Ireland on the west, through 35 degrees of lati- 

 tude, through North France and Belgium, as far as the 

 region of Westphalia. Next, the upper portions of the 

 folds were attacked by the subaerial and marine agents of 

 denudation over the whole of the Carboniferous area, 

 leaving the lower parts to form the existing coal-fields 

 which lie scattered over the surface of the British Isles, 

 and are isolated from each other by exposures of older 

 rocks ; and a broad east and west ridge was carved out of 

 the folded and broken Carboniferous and older rocks, 

 extending from the anticline of the Mendip Hills east- 

 ward through Artois into Germany, and constituting the 

 ridge or axis of Artois of Godwin-Austen. 



The next stage in the history of the folded Carboniferous 

 and older rocks is marked by the deposition of the Permian 

 and Secondary rocks on their eroded and water-worn 

 edges, by which they were partially concealed or wholly 

 buried, and these newer strata thin off as they approach 

 the ridge of Artois. This barrier, also, of folded Carboni- 

 ferous and older rocks sank gradually beneath the sea in 

 the Triassic, Liassic, Oolitic, and Cretaceous ages, and 

 against it the strata of the first three named ages thin off, 

 while in France and Belgium the Cretaceous deposits 

 rest immediately upon the water-worn older rocks. 



From these general considerations it is clear that the 

 coal-measures which formerly extended over nearly the 

 whole of Southern England can now only be met with in 

 isolated basins under the newer rocks, and that these are 

 thinnest along the line of the above-mentioned barrier. 



(4) The exposed coal-fields in Britain, and on the Con- 

 tinent also, Godwin- Austen pointed out, along this line, 

 are of the same mineral character, and the pre- Carboni- 

 ferous rocks are the same. This ridge or barrier also, 

 where it is concealed by the newer rocks^ is marked by 

 the arch-like fold (anticHnal) of the chalk of Wiltshire, 

 and by the line of the North Downs in Surrey and Kent. 

 Godwin-Austen finally concluded that there are coal-fields 

 beneath the Oolitic and Cretaceous rocks in the south of 

 England, and that they are near enough to the surface 

 along the line of the ridge to be capable of being worked. 

 He mentioned the Thames Valley and the Weald of Kent 

 and Sussex as possible places where they might be 

 discovered. 



These strikingly original views gradually made their 

 way, and in the next eleven years became part of the 

 general body of geological theory. They were, however, 

 not accepted by Sir Roderick Murchison, the then head 

 of the Geological Survey, who maintained to the last that 

 there were no valuable coal-fields in Southern England. 



(5) The next important step in the direction of their 

 verification was that taken by the Coal Commission of 

 J 866-67, by whom Mr, Godwin-Austen was examined at 

 length, and the results of the inquiry embodied in the 

 Report by Mr. Prestwich. In the Report Mr. Godwin- 

 Austen's views are accepted, and fortified by , a vast 

 number of details relating both to the coal-fields of 

 Somersetshire and of France and Belgium. Mr, Prest- 

 wich also calls special attention to the physical identity 

 of the coals of these two regions, and to the fact that the 

 Carboniferous and older rocks in both are similarly dis- 



NO. 1083, VOL. 42] 



