August i6, 1 900 J 



NA TURE 



397 



drills acknowledjjed to be of glacial origin, and that their 

 curiously mixed assemblage of shells does not represent a 

 contemporaneous fauna.' These beds form part of the 

 " Helvetian " interglaeials of Prof. GeiUie's scheme. 



Midland Cottntics.—\n the North Midlands, Mr. R. M. 

 Deelcy," in classifying the comple.>c drifts of the Trent 

 Basin, has sought to e.\plain these deposits as the product 

 of several successive glacial and interglacial epochs, but 

 the correlation of these supposed epochs with those of Prof. 

 Geilcie is found dilVicult." All except the latest of the de- 

 posits classed as interglacial are unfossiliferous ; and the 

 evidence for glaciation later than this fossiliferous deposit 

 — an ancient river-gravel of the Derwcnt containing 

 mammalian remains (hippopotamus, rhinoceros, and 

 elephant) ' — is very questionable.' The recent work of the 

 Geological Survey in the district, in which I am taking 

 part, confirms Mr. Deeley's opinion that the basin was 

 invaded by ice-lobes from different quarters, which attained 

 their maxima at different times. It is also found that 

 there are areas which apparently lay beyond the reach of 

 these lobes, and remained unglaciated," In these circum- 

 stances, the simplest explanation of the facts seems to be 

 that the marginal area was sometimes e.xposed and some- 

 times ice-covered by the different flows in their oscillations 

 during a single prolonged period of glacial conditions. 

 There is no evidence of marine submergence in the district, 

 though the whole of it lies much below the level attained 

 by the shelly " middle glacial " stratified drifts of the 

 country to the westward. 



Farther south, Mr. W. Jerome Harrison, after a lengthy 

 investigation of a wide area centring around Birmingham, 

 finds that the drifts were the product of three great ice- 

 lobes — the " Arenig Glacier," the " Irish Sea Glacier," 

 and the "North Sea Glacier"; and he concludes that 

 there has been no marine submergence and that " the 

 district affords no proof of any ' interglacial ' period."' 



Xorth-western Counties. — The glacial deposits of West 

 Lancashire, Cheshire, and North Wales are essentially 

 analogous to those of the Isle of Man. The supposed 

 " middle glacial " submergence has figured largely in the 

 voluminous literature of this part of the country; and Prof. 

 Geikie, by supposing that certain Welsh and Yorkshire 

 cave deposits of doubtful age are interglacial, and that an 

 undefined part of the glacial sands and gravels indicates 

 interglacial submergence, is able to picture a " Saxonian " 

 glaciation, a " Helvetian " mild interglacial epoch with 

 a wide land surface succeeded by marine conditions, and 

 then a later " Polandian " glaciation from the same 

 quarter as the first." But the investigators who have 

 studied this district most closely are agreed that the inter- 

 stratification of the boulder-clay with the sands and gravels 

 is so intimate and so many times repeated that the de- 

 posits must have been practically contemporaneous and of 

 common origin ; and the differences of opinion that have 

 arisen are on the question whether these drifts as a whole 

 have been deposited by the sea or by land-ice." The case 

 for the land-ice hypothesis and for the unity of the glaci- 

 ation has been admirably summarised by Prof. P. F. 

 Kendall.'" 



The systematic researches of the late J. G. Goodchild 

 in Fdenside," and of Mr. R. H. Tiddeman in North 



1 "The Glacial Drifts of Norfolk." P,vc. G.-i>l. Assoc, vol. ix. (1887), 



n," Quart. Journ. 

 iii., vol. X. (1893), 



VV i'-ib- 



* H. H. Arnold-Bemrose and R. M. Deelev, "Mammalian Remains n 

 Der»ent River Gravels." Quart. Journ. Geol. Soc, vol. lii. (1896), 

 pp. J97-5i°- 



5 C. Fox Strangways, Mem. Ccel. .Sun'ey. "Country between Derby. ' 

 S;c. (igos), p. 41. 



^ " Summary of Progress of Geol Survey for rgn5." 



" "The Ancient Glaciers of the. Midland Counties." Proc. Geol. .Assoc. 

 vol. XV. (1898). pp. 400-408. 



» " Great Ice Age." 3rd ed., pp. ^67-374. 



9 f.f. :-G. E. De Ranee, Ref. Brit. Assoc for 1893. 779 : A. Strahan, 

 Quart. Journ. Geol. Soc, vol. xlii. (1886), p. 383 ; T. Mellard Reade. 

 Quatt. Journ. Geol. Soc, vol. xxx. (r874l, pp. 35-37 ; and ikid., vol. xxxix. 

 (i883>, pp. 123-127. 



yvi In 0. F. Wright's "Man and the Glacial Period" (London, iSqj), 

 5-153, and in H. Carvill Lewis's "Glacial Geology of Great Britain 



'- "The Pleistocene Succession in the Tri 

 Geol Soc , vol. xlii. (1S86), pp. 437-480. 



■■i"The Glacial Succession." Geo/. Ma. 



and Ireland " (London, r8Q4). pp. 394-434. 



11 O/: cit., and Quart. Journ. Geol. Soc, vol. 



NO. 1920, VOL. 74] 



• ("875). pp. 55-99- 



Lancashire and Vorkshiie,' failed to bring to light any 

 evidence for this great " Helvetian " break in the glaci- 

 ation ; nor have the later investigations farther southward, 

 among which we may mention those of Prof. T. J. Jehu 

 in Peinbrokeshire," and of the Geological Survey in South 

 Wales, shown any other result. 



In support of the hypothetical Helvetian land surface in 

 the north-western region, Prof. Geikie lays stress upon the 

 discovery of a muddy deposit containing undetermined 

 vegetable remains and diatoms in the boulder-clay near 

 Ulverston, in North Lancashire. This material, pene- 

 trated in borings for iron ore, was first described by Mr. 

 J. Bolton,' more than forty years ago, as occurring beneath 

 the " pinel " (boulder-clay) and just above the Carbon- 

 iferous Limestone; Miss E. Hodgson' shortly afterwards 

 gave reasons for believing that the " muck " had been 

 introduced into the cavernous top of the limestone by 

 recent streams which drain underground ; and eighteen years 

 later Mr. J. D. Kendall '' recorded further borings, which 

 seem to show that the material sometimes occurs a few 

 feet above the base of the boulder-clay ; but his suggestion 

 that the outcrop of the bed in question may be represented 

 by the submerged forests occurring above the boulder-clay 

 on the foreshore at Walney, Dring, and St. Bees indicates 

 a misapprehension of the evidence. Prof. Geikie infers 

 that the great mass of boulder-clay, in one place 70 feet 

 thick, above the " muck " represents the Polandian 

 boulder-clay, and the bottom clay, rarely more than 3 or 

 4 feet thick, the Saxonian glaciation ; but this reading is 

 quite contrary to the usual relations of the boulder-clays 

 assigned to these epochs ; and, indeed, the whole case is 

 too indefinite to carry any weight. 



Another peaty deposit to which an interglacial age has 

 been assigned was observed many years ago near Maccles- 

 field by Dr. J. D. Sainter," but in this instance the bed 

 occurred above all the boulder-clays, and was covered only 

 by a few feet of coarse bouldery gravel, which, from its 

 topographical position, is probably of fluviatile origin and 

 of late-glacial or post-glacial age. 



Northern Counties. — In Northumberland and Durham, 

 so far as I am aware, no indication of the Helvetian inter- 

 glacial epoch is forthcoming. The boulder-clays, with their 

 intcrbedded sands and gravels, are like those of the North 

 Yorkshire coast, and have received similar explanation. 

 Dr. D. Woolacott,' in his recent description of glacial 

 sections in Northumberland, remarks : " So far as the 

 available evidence . . . goes there does not seem to be 

 anything pointing to an interglacial period or periods. 

 The deposits of sand and sandy clay intercalated in the 

 true boulder-clay are, as a rule, most irregular in position, 

 and vary laterally in thickness." 



Southern Enf;land. — In the South of England, beyond 

 the area of actu,il glaciation, evidence for an interglacial 

 epoch has been brought forward from two or three locali- 

 ties, where deposits of very limited extent, partly of marine 

 and partly of freshwater origin, have yielded a fauna and 

 flora indicative of comparatively warm conditions. 



Of these, the most important is a marine deposit, con- 

 taining a molluscan fauna of southerly facies, which occurs 

 on the coast of Sussex near .Selsey. The case for its inter- 

 glacial age has been stated by my colleague, Mr. Clement 

 Reid," who observed numerous large erratic boulders rest- 

 ing on a floor of Eocene beds in a temporary exposure 

 on the foreshore, and infers that these boulders represent 

 a period of glacial conditions anterior to the deposition of 

 the bed containing the temperate-climate shells, while a 

 later period of glaciation is inferred from the presence of 

 the " Coombe-rock," or chalky rubble, overlying the shell- 

 bed. This interpretation of the section has, however, 



1 Quart. Journ. Geol. Soc, vol. xxviii. (1872). pp. 47i-4or. 



'- "The Glacial Deposits of Northern Pembrokeshire." Trans. Koy 

 Soc Edinburgh, vol. xli. fr904), pp 53-97. 



•1 Quart. Journ. Gfol- Soc, vol. xviii. (1862), pp. 274-7. 



•• Quart. Journ. Geol. Soc, vol. xix. (1863). pp. 19-31. 



s Quart. Jourti. Geol. .'Soc, vol. xxxvii. (1881), pp. 29-39. 



1 "Geological Rambles round Macclesfield" (Macclesfield, 1878), 

 PP.- (>\-,. 



' Quart, lourn. Geol. Soc, vol. Ixi. (1905). p. 68. 



s "On the Pleistocene Deposits of the Sussex Coast." Quarl. Journ. 

 Geol. Soc. vol. xlvii!. (1S92). pp. 344-6t. See also "The Origin of the 

 British Flora" (London, 1899), chap. iv. et seq. 



