Jan. 6, iHSj] 



NA TURE 



2 19 



feeling which it is much to be wished were more general 

 among the students of this nest of obscurities. 



In the oldest Pahieozoic rocks (we hardly dare name 

 them, for no nomenclature can be adopted without 

 bringing a storm about one's ears from some quarter), 

 Prof. Lnpworth's triple nomenclature is adopted. It 

 would be a comfort if the term " Ordovician " could meet 

 with general acceptance, for there would then be a chance 

 of our knowing what any author meant by Cambrian and 

 what by Silurian, without long and wearisome inquiry as 

 to what camp the said author attached himself to. Our 

 author's weakness for new names, we think, shows itself 

 in the Silurian subdivisions. It is by no means obvious 

 why our old friends " Ludlow " and " Wenlock " are to be 

 displaced by " Clunian " and " Salopian." We had thought, 

 too, that it was generally admitted that the old " Tile- 

 stones '' and " Downton Sandstone " had no business in 

 the Ludlow group, and that they had better be placed by 

 themselves as "passage beds" between the Silurian and 

 Old Red. 



In his treatment of the Devonian the author displays 

 commendable caution. He reproduces on p. i 5S a fanci- 

 ful attempt to correlate the minor subdivisions of the 

 marine Devonian and lacustrine Old Red, but admits 

 that it requires " further examination." There is also a 

 good summary of the recent researches of Prof. A. Geikie 

 and Prof. Hull on the Old Red of Scotland and Ireland. 

 Here, and generally, the book is well up to date. 



There are some rather serious objections to be made 

 to the chapter on " The Carboniferous System." The 

 Lower Coal-measures and Millstone Grit are stated to be 

 "partly marine," the Middle and Upper Coal-measures to 

 be " fresh-water." Now, whatever reasons there may be 

 for calling the Lower Coal-measures and Millstone Grit 

 marine in part, apply to the Middle Coal-measures as 

 well. Marine shells occur in the Millstone Grit and 

 Lower Coal measures ; but every one who has looked at 

 the question with a critical eye takes careful note of the 

 fact that they are the exception, not the rule, for they are 

 found only in a few thin bands. Marine shells occur also 

 in the Middle Coal measures, but here again they are 

 confined to a few thin bands. In short, throughout the 

 bulk of the beds classed as Millstone Grit and Coal- 

 measures, fossils unquestionably marine are strikingly 

 conspicuous by their absence ; but from bottom to top, 

 with perhaps the exception of the very uppermost Coal- 

 measures, we every now and then come across a thin 

 band containing, often in great abundance, fossils that 

 are certainly marine, and some of them Carboniferous 

 Limestone species. The inference surely is that the 

 Millstone Grit and Coal-measures are in the main 

 estuarine or fresh-water, but that every now and then the 

 sea broke in and flooded the basin in which they were 

 formed. There are other considerations, too long to be 

 reproduced here, which seein to lead to the same conclu- 

 sion. They are summarised in " Coal, its History and 

 Uses" (Macmillan, 1878), pp. 50-53. It is hardly 

 fair, however, to blame our author for any short- 

 comings he may have been guilty of in this matter. 

 He has evidently followed Prof Hull, and knowing, 

 as he doubtless does, what unrivalled opportunities 

 Prof. Hull has had for studying the Carboniferous 

 rocks, it was only natural that he should look upon him 



as a trustworthy authority. But when Prof. Hull's state- 

 ments and tables come to be analysed, they break down 

 sadly. In his general table of the British Carboniferous 

 Series {Quart. Journ. Geol. 3'oc., xxxiii. 615), we read: 

 " :Middle Coal-measures (fresh-water and estuarine). 

 Marine species rare." " Canister Beds. Essentially marine. 

 Fossils marine." Perfectly true, but only half the truth. 

 Marine species are rare in the Middle Coal-measures, but 

 they are rare in the Canister Beds also ; in both equally 

 they are absent from the bulk of the formation, and are 

 found only in certain bands, always thin, and few in num- 

 ber. This latter fact, which seems to us to be of the 

 utmost significance, is unluckily overlooked by Prof Hull. 

 Again, in his tabular summary of Carboniferous Mol- 

 lusca, Prof. Hull has marshalled what looks like a 

 formidable list of marine forms in the column for the 

 Canister Beds, while only comparatively few occur in the 

 column headed Middle Coal-measures. But against this 

 we have to set off the fact that the marine shells of the 

 Canister Beds come almost exclusively from beds such 

 as ironstones and the roofs of coals which have been 

 largely worked ; while, with I think one exception only, 

 the marine shells of the Middle Coal-measures are not 

 found in beds economically valuable, and therefore 

 largely explored. It is only an additional instance of the 

 truth that there are two ways of looking at statistics, the 

 one arithmetical, and the other rational, and that the 

 purely arithmetical aspect is always full of risk. 



Two very interesting borings into the Permian, or, as 

 our author prefers to call them, Dyassic, beds are quoted 

 on p. 239. But it is hardly right to say that the Middles- 

 brough boring shows beds " not found anywhere along 

 the outcrop." The " Magnesian Limestone, 52 feet, and 

 Grey Limestone, 15 feet," may well be the " Brotherton 

 Limestone" of the Yorkshire section on the opposite 

 page; and the "gypsum, rock-salt, and marl" beneath, 

 fit in exactly with the " Middle Marls " of Yorkshire. In 

 the Scarle bore-hole the great thickness near the base of 

 the Permian of beds largely sedimentary (" shales and 

 dolomites, 193 feet ") indicates that we are here approach- 

 ing the eastern shore of the lake in which the Permians 

 of the north-east of England were accumulated. It seems 

 to us that perhaps rather too much stress is laid on the un- 

 conformity between the Permian and Carboniferous. It 

 is marked enough, of course, in the north-east of 

 England, but elsewhere, as in North Staffordshire and 

 Denbighshire, it does not seem to be an easy thing to say 

 exactly where the Coal-measures end and the Permian 

 begins. Now it is, to say the least, worth notice that, in 

 those localities where the unconformity is strong, the 

 Upper Coal-measures are absent or only feebly repre- 

 sented ; but that where we find Upper Coal-measures 

 in force, the unconformity is less strongly marked, 

 and perhaps in some places there may be no uncon - 

 formity at all. Can -this be the explanation? In some 

 places, the north-east of England for instance, the absence 

 of the Upper Coal-measures is not due to denudation ; 

 there never were any Upper Coal-measures there. 

 What may be called the LTpper Coal-measure period was 

 in these localities not a period of deposition, but of 

 upheaval and denudation among the Carboniferous 

 rocks ; and so, when, later on, the formation of Permian 

 rocks began, these rested on upturned and largely 



