Societies and Academies

Abstract

LONDON

Geological Society, November 9.-Mr. Joseph Prestwich, F.R.S., President, in the chair. Lieutenant Reginald Clare Hart, R.E., Brompton Barracks, Chatham; Lieutenant James Frederick Lewis, R.E., Brompton Barracks, Chatham; and Mr. M. F. Maury, jun., 1300 Main Street, Richmond, Virginia, U.S., were elected Fellows of the Society. (i.) "On the Carboniferous Flora of Bear Island (lat. 74° 30' N.),“by Professor Oswald Heer, F.M.G.S. The author described the sequence of the strata supposed to belong to the Carboniferous and Devonian series in Bear Island, and indicated that the plant-bearing beds occurred immediately below those which, from their fossil contents, were to be referred to the mountain limestone. He enumerated eighteen species of plants, and stated that these indicated a close approximation of the flora to those of Tallow-bridge and Kiltorkan in Ireland, the greywacke of the Vosges and the southern Black Forest, and the frerneuiln-sliales of Aix and St. John's, New Brunswick. These concordant floras he considered to mark a peculiar set of beds, which he proposed to denominate the c Ursa-stage.“The author remarked that the flora of Bear Island has nothing to do with any Devonian flora, and that consequently it and the other floras,,which he regards as contemporaneous, must be referred to the Lower Carboniferous. Hence he argued that the line of separation between the Carboniferous and Devonian formations must be drawn below the yellow sandstones. The presence of fishes of Old Red Sandstone type in the overlying slates he regarded as furnishing no argument to invalidate this conclusion. The sandstones of Parry Island and M elville Island are also regarded by the author as belonging to the * 'Ursa- s tage,"'J which, by these additions, presents us with a flora of seventy-seven species of plants. The author remarked upon the singularity of plants of the same species having lived in regions so widely separated as to give them a range of 26° of latitude, and indicated the relations of such a luxuriant and abundant vegetation in high northern latitudes to necessary .changes in climate and in the distribution of land -and .water. Sir Charles Lyell remarked that the Yellow Sandstones of Dura Den in Fife, and of the county of Cork in Ireland, contain Glyplohpis and Asterolepis, genera of fish exclusively Devonian, or belonging to the middle parts of the Old Red Sandstone also the genus Coccosteus, which is abundantly represented in the Middle Old Red Sandstone, and sparingly, or only by one species, in the Carboniferous formation. The evidence derived from these fishes inclined him to the belief that the Yellow Sandstone, whether in Ireland or Fife, should be referred to the Upper Devonian, and not to the Lower Carboniferous, as Sir Richard Griffiths contended, and as Heer now thinks. As to the argument founded on the plants, he considered it an important and truly wonderful announcement, that many well-known Carboniferous species are common to Bear Island (in lat. 74° 30' N.), in the Arctic regions and to Ireland and other parts of Europe (26° of latitude farther south). But fossil plants are supposed to have a wider range in space and time than fossil fish; and we know that the cryptogamic flora of the ancient coal is remarkable for the wide horizontal spread of the same species, extending from North America to Europe, so that we need not be surprised if many species should extend vertically from the Devonian into the Carboniferous strata. Mr. Carruthers remarked on the bearing of the paper on the Kiltorkan beds, and considered that Dr. Heer had completely established the correlation of the deposits. He differed, however, as to the numerical proportions of the species. He could not recognise Cyclostigma as a genus, but considered it founded on insufficient, grounds, in which view Prof. Haughton now agreed. It was, in fact, founded on fragments of the bark of Lepidodendron Grijfilhsii, Brorgniart, to which species the Lepidoaendron indicated by Prof. Heer as L. adthei-mianum really belonged. Other detached portions of this same plant had been described by various authors under no less than seven different specific names, and referred to nearly an equal number of distinct genera, and Prof. Heer had reckoned these as species in his comparison of the Bear Island and Irish floras. Prof. Heer had been led, chiefly by the erroneous determination of the Kiltorkan Lepidodendron by the Irish palaeontologists, to refer these beds to the Carboniferous rather than to the Devonian formation, the Kiltorkan fossil having been established as a very distinct species by Bjongniart and Schimper. Mr. Carruthers considered that both the Irish and Bear Island deposits belonged to the Devonian. Mr. Boyd Dawkins pointed out that the proximity of land was exhibited by the presence of terrestrial plants in the deposits, and believed that this might have much to clo with the difference in the proportion in the beds. As the marine fauna decayed more rapidly than the terrestrial, it was preferable for classificatory purposes. He mentioned forms of vegetable life which had been recently discovered in America in beds of Cretaceous age. He did not believe that corals could have existed in those high latitudes under anything approaching to the present condition. Prof. Noidenskj ld had failed to discover any traces of glacial action in these beds; and the question arose whether there had been any change in the position of the Pole or in the radiated heat of the sun. -2.) "On the Evidence afforded by the Detrital beds without and within the North-eastern part of the Valley of the Weald 03 to the mode and date of the Denudation oi that Valley.“By Mr. S. V. Wood, jun., F.G.S. The author commenced by discussing the various hypotheses that have been proposed to explain the denudation of the Weal-d Valley. In his opinion the upheaval of the district took place in Posr-glacial times, and subsequently ito .the deposition of the gravels of -the Thames Valley, of East Essex, and of the Canterbury heights; .and the denudation was effected chiefly by tidal erosion during gradual?upheaval in an inlet of the sea, aided by the action of fresh water flowing into this inlet from the north by streams draining the land which now .constitutes the counties of Middlesex and Essex. The chief evidence in favour of his views is as follows:-i. The absence from the glacial beds of Essex.of any d'bris representing a considerable denudation of the Weald during the glacial'period, and the probability that the Wealden ar_a was beneath the sea during the deposition of the Boulder Clay. 2. The comparative absence of Lower Cretaceous or Hastings-sand 'materials-rom the Post-glacial gravel-sheets outside the north of the Weald. 3. The impossibility of reconciling the presence of Tertiary pebbles in certain Weald-gravels with an origin by means of streams flowing in the direction of the present rivers. 4. The antagonism between the character of the major valley of the Weald and that of any excavation producible by the agency of rivers. 5. The persistence of the old coast contour with the river-drainage entering it from the north. 6. The existence of a cause, in the shape:of .an isthmus at Dover, sufficient to induce a strong tidal scour, Mr. Godwin-Austen thought that the author had done his theory injustice in presenting only a portion of the Wealden area for consideration. He remarked that phenomena similar to those of the WTeald were to be found in various parts of Western Europe. He was glad to find that Mr. Searles Wood did not regard the escarpment as representing marine cliffs; but he did not attach sufficient weight to the absence of any material of marine origin at their base, so that there was no evidence of the presence of the sea within the Wealden area. He differed wholly from the author as to the age of the gravels, for beneath the gravels were silty beds containing elephant remains. These gravels he was inclined to refer to a glacial period, as they contain blocks such as cotild only have been transported by the agency of ice. The elephants found in the valley of the Wey are of the species (E. primigenius) which also occurs in the Selsea beds; and he believed both to be of glacial age. As to the theory of the denudation of the Weald, he professed himself a convert to the views of Messrs. Foster and Topley, and cited what was now going on in Heligoland in illustration of atmospheric denudation. Mr. Whitaker observed that the present absence of gravels along parts of the valley of the Thames affords no proof of their not having formerly existed. He pointed out the soft and friable nature of most of the rocks of the Wealden, which would account for their absence in the gravels. The only really hard rock was the Chert of the Lower Greensand, which was abundant in the gravels of West Kent. Angular flints occurred at the base of the chalk escarpment wherever it had been carried back by denudation. The major valley of the Weald had been spoken of, but he denied that any such valley existed; it was merely a series of numerous small valleys. He could not conceive the livers flowing against the dip of the strata, as supposed by Mr. Wood. He did not agree in the view of the denudation of the Weald being such an enormous affair, but thought that it might be due to comparatively small causes. The President pointed out that bevond Southend there was a section precisely similar to that of Grays. It was a mistake to suppose pebbles from the Wealden area did not occur in the Thames gravels.He thought that much of the denudation of the Wealden area might have taken place before the glacial period. The presence of Tertiary pebbles in the Wealden area might readily be accounted for by their presence at the edge of the escarpment Mr. Searles V. Wood, jun., in reply, justified himself for having limited his observations to the northern part of the Weald, as it was there only that it could be brought into juxtaposition with the glacial beds. He maintained that, under certain circumstances, no beaches or marine beds were formed at the base of sea-cliffs. He pointed out that in Post-glacial gravels large blocks of rock were frequently found, and protested against limiting all ice-transport to the glacial period. He could not recognise the Selsea beds, with 150 living species, some of southern character, and none extinct, as glacial. He did not acknowledge the alleged softness of the Wealden rocks. The Earl of Enniskillen sent for exhibition a fragment of Lias Limestone from Lyme R'gis perforated by Pholades.