= > ot a as era ee es ; vs ’ ; i : ; ’ . meer nen saab. : Arn rn ‘ SP te tute Be -—< oa re td ee ee “ al oe ye ptalinw-o-< f+ 4-638 5 the a te 226 PEPE none a tN F —s = oe > oad . non Pralietzh > Palle . ~ AP a af, 'f sr ht aoe) F tz 63) 5 a ae ee a , rT I , Ln ea eG eo —— - 49 jo +e 1 ' : ‘ bs aoe Vee i +e Ane. ig 20) | ae eal _ : i] Ae : ; a : a if uu i ee ie ao he aa ) "ane eae 5! Pe) ih ‘J ‘ a 4, tn MRTERLY JQURNAL & a ~~ —__ ~ oo, = = a | I ? ‘atl WF: W , F ees @ i 4 q ; ; : LAs bal aa . ue ‘ tot hea? 'e aw i a Fe * pee Ane. i tt, A ’ a “n es 1) eet A Boi: iM , twa » ae i i] 1 >. Phe A VSR OY & cs Ver™ Nee ety se ; ' a vo a a bbe Leste wee Mee, biome, Pietige 4) Hope ‘ ot ‘ i 5 : ry - ™ ‘ 7 P Py : l : ; | i s = 7 ote % | — * 7 , » LAIN DOR s LONGMAN ON, 8) ae | A i; | a) +" * 2 =~ | Ye AA AGH rae, be Bs eee" eat Aq! our Pay»! ae. t ait), * 2 oa “4 5$0. 642 Geo/ OF THE GEOLOGICAL SOCIETY OF LONDON. EDITED BY THE ASSISTANT-SECRETARY OF THE GEOLOGICAL SOCIETY. Quod si cui mortalium cordi et cure sit non tantum inventis herere, atque iis uti, sed ad uiteriorn penetrare; atque non disputando adversarium, sed opere naturam vincere; denique non belle et probabiliter opinari, sed certo et ostensive scire; tales, tanquam veri scientiarum filii, nobis (si videbitur) se adjungant. —Novum Organum, Prefatio. VOLUME THE FORTY-FOURTH, __ Ve 1888. LONDON : LONGMANS, GREEN, AND CO. PARIS: FRIED. KLINCKSIECK, 11 RUE DE LILLE; F, SAVY, 24 RUE HAUTEFEUILLE. LEIPZIG: T. 0. WEIGEL. SOLD ALSO AT THE APARTMENTS OF THE SOCIETY. MDCCCLKXXXYVIII, List OF THE OFFICERS OF THE GEOLOGICAL SOCIETY OF LONDON. SPP OAL n~ Elected February 17, 1888. President, W. T. Blanford, LL.D., F.R.S. Gice-Prestvents. Prof. J. Prestwich, M.A., F.R.S. Henry Woodward, LL.D., F.R.S. John Evans, D.C.L., LL.D., F.R.S. Prof. T. McKenny Hughes, M.A. Secretaries. W. H. Hudleston, Esq., M.A., F.R.S. | J. E. Marr, Esq., M.A. Foreign Secretary. Sir Warington W. Smyth, M.A., F.R.S. Creasurer. Prof. T. Wiltshire, M.A., F.L.S. COUNGCIL., W. T. Blanford, LL.D., F.R.S. | Major-Gen. C. A. McMahon. John Evans, D.C-L., LL.D., F.R.S. | J. E. Marr, Esg., M.A. L. Fletcher, Esq., M.A. E. Tulley Newton, Esq. A. Geikie, LL.D., F.R.S. Prof. J. Prestwich, M.A., F.R.S. Henry Hicks, M.D., F.R.S. Prof. H. G. Seeley, F.R.S. Rev. Fdwin Hill, M.A. Sir Warington W. Smyth, M.A., F.R.S. W. H. Hudleston, Esq., M.A., F.R.S. W. Topley, Esq. Prof. T. Mc¢Kenny Hughes. Rev. G. F. Whidborne, M.A. J. W. Hulke, Esgq., F.R.S. Prof. T. Wiltshire, M.A., F.L.S. Prof. T. Rupert Jones, F.R.S. Rev. H. H. Winwood, M.A. Prof. J. W. Judd, F.R.S. Henry Woodward, LL.D., F.R.S. R. Lydekker, Esq., B.A. Assistant-Secretary, Clerk, Librarian, and Curator. W. S. Dailas, Esq., F.L.S. Assistants in Office, Library, and Museum. Mr. W. Rupert Jones. Mr. Francis E. Brown. TABLE OF CONTENTS. Page ADAMSON, SAMUEL A., Esq. Notes ona recent Discovery of Stzg- maria ficoides at Clayton, Moms hivey iat iu, J eurecawae ore 3. coon 375 ATTWOOD, GEorGE, Esq. Notes on some of the Auriferous Tracts of Mysore Province, Southern India. With an Appendix by emit err aeons: eons en 300 Couns, J. H., Esq. On the Sudbury Copper-Deposits.......... 834 Davison, CHARLES, Esq. Note on the Movement of Scree-Material. 232 ——. Second Note on the Movement of Scree-Material ........ 825 Dawkins, Prof. W. Boyp. On Arluus anglicus, a new Carnivore from the Red Crag. «(Plate X_)). ve... 0.275... ee 228 Dawson, Sir J. W. On the Eozoic and Paleozoic Rocks of the Atlantic Coast of Canada, in comparison with those of Western Europe and the Interior of America. ..........0.0.000eeeens 797 Dr Rance, C. E., Esq. Note on the Cae Gwyn Cave .......... 576 FisHer, Rev. 0. On the Occurrence of Elephas meridionalis at Dewashy Wormer ei Soe. F.. fie testi Lio. eer 818 Fox, Howarp, Esq. On the Gneissic Rocks off the Lizard. With Notes on the Specimens by J. J. H. TEAux, Esq. ............ 309 GARDINER, Miss MarGareT I. The Greensand Bed at the Base of ther Mbaner Sandy. ois. 3)... » cn cages be wehbe ides ee 755 GaRrpNER, J. STARKIE, Esq., HENRY KEeEpine, Esq., and H. W. Monckton, Esq. The Upper Eocene, comprising the Barton and Upper Bagshot Formations. ..........s0+ 0.02. stele eee 578 GrIkin, ARCHIBALD, Esq. On the Age of the Altered Limestone ES LOS (i rem me Te 62 GREEN, Prof. A. H. A Contribution to the Geology and Physical Geography of the Cape Colony ......... oo ome hogan 239 Gunn, W., Esq. See “ Report.” HarkeER, ALFRED, Esq. On the Eruptive Rocks in the Neighbour- hood of sarn, Caernarvonshire .......6 se. .5 deuce Lh 449 Hatcs, Dr. F. H. On the Spheroid-bearing Granite of Mullagh- gere, Co. Donegal. (Plate X1V.).., . ,eieeuie saaiee oe ee 548 TABLE OF CONTENTS. Vv Page Hicks, Dr. H. Onthe Cae Gwyn Cave, North Wales. Witha Note Pe en ELANCE, BQ. sec eases eb ites oe eremnine pn epieco ears 561 Hitt, Wim11AM, Esq. On the Lower Beds of the Upper Cretaceous Series in Lincolnshire and Yorkshire. With the Description of anew Species of Holaster, by A. J. Jukes-BrowneE, Esq. PR LE Ya a o's suche: cages thetg ounce wangy Io % © aimenys, 00. Sinn ep mg Heard cat 320 Hinps, Dr. G. J. On the History and Characters of the Genus Septas- trea, D’Orbigny (1849), and the Identity of its Type-Species with that of Glyphastrea, Duncan (1887). (Plate IX.) ...... 200 HinxMay, L., Esq. See “ Report.” Horne, Joun, Esq. See “ Report.” Hueaess, Prof. T. M¢Kenny. On the Position of the Obermittweida MSC Rc ce gee ne She wee Vere CL eal oa oa ele Coy eee Maline Cae GimymOaveriiwkl. Jini attend. ows. caves 112 Hutton, Capt. F. W. On a Hornblende-biotite Rock from Dusky RUMEN COATES, yin Sac Sugy/evsimicig hide woe de swede ah altieatlte sige’ 745 Irvine, Rev. A. The Red Rock Series of the Devon Coast- PME eh cae alae f Sip. Paya. clscgl a 4/8 oanqueal Sv», Siypt xe driv aatienes act am 149 . Supplementary Notes on the Stratigraphy of the Bagshot peer meer et L Om OM, ASU 6! 2 se ces apo. oe qjgye @ ¥ 5 bos aarieceee sae 164 JuKres-Brownr, A. J., Esq. Description of a new Species of Ree ect Ube NEU oe aca a dieich chaivia cleo. tbie seetela phan a» Who kaas 364 Krrpine, Henry, Esq., J. S. GARDNER, Esq., and H. W. Moncx- TON, Esq. The Upper Eocene, comprising the Barton and Biper Baeshot, Formatlomsy.\. .jccasecuchs atvicrsvvberdl 578 Kirr0g, J. R., Esq. Directions of Ice-flow in the North of Ireland, as determined by the Observations of the Geological Survey .. 827 Krrxesy, James W., Esq. On the Occurrence of Marine Fossils in nee Coal-Measures OL Mie... , ' = on illeg 7 ~ 7 cat + i 6 - y a ‘ , - « <* S hy * v ‘ etx ei = ‘ x ‘ 7 4 “a “oh » LIST OF THE FOSSILS FIGURED AND DESCRIBED IN THIS VOLUME. [In this list, those fossils the names of which are printed in Roman type have been previously described. ] Name of Species. Formation. Locality. PLANTA, SRRMiaria fICOIUES ............020000000 |Carboniferous ...|Yorkshire......... RHIZOPODA. Ehrenbergina bicornis. Pl. i. f. 3... \ Ellipsoidina ellipsoides, var. oblonga. | RM ethics) nos akitwaceanigien creas: Haplophragmium rugosum. P1.i.f.2 | ; , nal Nodosaria longiscata .................. f BO a ee Spheroidina ornata. Pl.i.f.4 ... Textularia quadrilatera ............... Truncatulina mundula ............... ) C@LENTERATA. ( Actinozoa.) Septastrea Forbesi. Pl. lx. f. 1-5, Mabe Woon s ret etu ecb aew tebe ences Miocene ......... United States ... — >? hirtolamellata .................. HOGERE venice o2 sci: France ..... senses MIMIGUALEL AMIS ince sckoacnascsvese NUOCEMES secant BANCO 8 cia omits om sexpadiata. SP] ix. f. 6, 16... |Miocene .....0..: United States ... ECHINODERMATA. Holaster rotundus. PI. xii. ......+06 |Lower Chalk .../England ......... Moxivusca. (Brachiopoda.) Atrypa flexuosa. FI. xvi. f. 20...... [SilOrian \......0. HESEVGHEO, «eassaanuedecacecess. * (0. —— Woellerstorfi, Schw., ap.......ccccsssccescasescees * * x eee aneriana.d Orb: (2) 8p. <.acacaarsenadesensccie: * % (3 Mardingerii, ad Ora.) sp. (2) soceccssevcerconesevcces % 80 GU GE Ae pe MN a te coals nas anenp ste aa ted cee sai Sa or Lulvinulina coneentrica, Pf J. .....0scs00. ’ \ ’ , by = Ny \ ts Vy QA a ee BAY | NS RAY RASA CANAHATA LOIN he i \ i \\ \v ‘VY \FTNT Y VV uh ul ue dy \\a\ Vt “\ Wnt Waly \ay | z ANAC ANCA WX Weebl WAVY ALAA AAG t ch é. Blue, somewhat fetid limestones, full of broken shells (Lias). d. Limestone breccia (50-60 feet) consisting mainly of fragments of the under- lying limestones, with abundant pieces of chert and quartzite. c. Granophyre (‘‘Syenite”) of Beinn-an Dubhaich. 6. White lime- ane. a. Dark-grey limestone full of worm-casts and pieces of chert. tion of the entire separation of the Liassic strata from the more mas- sive or so-called ‘‘ unstratified” limestone of Strath. Immediately to the west of this instructive section the breccia is rapidly overlapped by higher Liassic beds, which rest directly on the Silurian series. The boundary between the two groups of rock runs down the glen, and in half a mile reaches the little ravine by which the stream discharges itself into the sea. Thence the line of sepa- 72 MR. A. GEIKIE ON THE AGE OF THE ration turns north-westward, and can be traced for some 200 yards along the steep declivity and the rocky shore until, owing to the trend of the coast, it strikes into Loch Slapin. This is the locality to which I have already referred as so deceptive in regard to the real relations of the two series of limestones. The fossiliferous Lias beds, dipping south-westwards at an angle of about 20°, con- sist of well-bedded limestone and calcareous shale, some of the layers being charged with Gryphea. Immediately underneath them, and without the intervention of any conglomerate, come the Silurian limestones, the dip of which, though not very distinct, seems to be parallel with that of the younger strata. The two groups are here, as it were, welded together at the juncture. Yet all along the slope above, the older limestone with its abundant cherts stands on end, with a north-west strike, which is maintained as it runs out to sea on the one hand, and away inland on the other. Another outcrop of the basement-beds of the Lias may be traced between Heast and Boreraig on Loch Eishort. At Heast a thick group of conglomerates and pebbly sandstones underlies the lowest of the Lias limestones. These detrital beds, with a band of lime- stone-conglomerate in the middle of them, rest on the red sandstone along the base of the escarpment on the east side of Beinn a Chairn. Butas they are followed south-westwards they disappear, and the limestone, in some places full of fragments of quartzite and black chert, lies directly upon the red sandstone and quartzite (fig. 1). (3) The Granophyre bosses.—Though it is no part of my purpose to describe the contact-metamorphism which has given to the lime- stone of Strath its place in geological literature, I may refer to the relation of the limestone to the Tertiary eruptive rocks of the district, and to the alteration which these have superinduced. In my early paper on the geology of Strath, I pointed out that the “syenites”’ of this district were easily divisible into two groups, one of which embraces disruptive bosses that ascend with steep sides through the surrounding rocks ; while the other includes overlying sheets which spread over the strata without violently disturbing them. The separation of the Silurian from the Lias limestone now enables us further to perceive that the bosses are confined to the Silurian area, and the overlying masses to the territory of the Lias. The latter have produced only a trifling alteration of the rocks. Except therefore along the flanks of the Red Hills, where, in some places, portions of the Secondary strata have been thrust up and invaded by the large eruptive masses, the Liassic beds are not seriously altered. The metamorphism for which Strath has so long been known turns out to be confined to the Silurian limestone. On the whole, it is restricted to the near neighbourhood of the bosses of granophyre, and consists in the usual marmarosis or assumption of a saccharoid crystalline texture. The white limestones become granular statuary marbles, and their bedding partially or wholly disappears. ‘The darker beds retain their dull leaden-grey hues, but . become coarsely crystalline and still expose, on weathered surfaces, their abundant rugged prominences of black chert. ALTERED LIMESTONE OF STRATH, SKYE. 73 Besides the protrusions of granophyre, innumerable basalt-dykes, likewise of Tertiary age, traverse the Silurian limestone, as well as all the other rocks of the district. The amount of alteration they have effected is trifling, notwithstanding their number and the pro- longed period during which they continued to be injected into fis- sures in the rocks. They began to be formed before the appearance of the granophyres which cut them off and send veins into them ; but their extravasation was afterwards resumed, for some of them are found running across the bosses of granophyre. It is not to the intrusion of the basic dykes, but to the uprise of the bosses of eruptive acid rocks that the Lower Silurian Limestone of Strath owes the metamorphism which has made it famous. Discussion. The PrestpEnt expressed his satisfaction at the lucid explanation of the old problem offered by Dr. Geikie. He had himself fallen into the same error as others with regard to the passage of Lias limestone into white marble in Skye. Mr. Eraeriner pointed out the close resemblance of the species exhibited from Durness and Skye. He also specially called atten- tion to some of the fossils exhibited. Dr. Hicks agreed that the similarity between the Durness and Skye limestones was unmistakable; the latter appeared to be the same as the lower beds of Durness. There was very little change in the general sequence throughout the west coast of N. Scotland. Mr. Marr observed that the Durness Limestone is precisely similar to the widely spread Orthoceras-limestone of Sweden and the Stin- char limestone of Girvan, so the occurrence of the same formation in Skye is natural. It was to be hoped that as rich a fauna would be found in Scotland as in Scandinavia. Dr. Hive pointed out the similarity of the fossils from Durness and Skye to those described by Billings from the Calciferous Lime- stones of the Mingan Islands, on the north shore of the St. Lawrence. Amongst others, the doubtful genus Archewocyathus is present at Mingan, at Newfoundland, and at Durness, and in all these localities it is associated with similar forms of Maclurea, Murchisonia, &e. Mr. Baverman had seen limestones in Matto Grosso, in Brazil, containing peculiar aggregations of quartz somewhat resembling fossils, and similar rocks were found in the province of S. Paulo, about 700 miles distant from the first locality. The latter were considered to be of Huronian age. The Presipent expressed a hope that full details of the Durness Limestoue and its fossils would be published before long. Dr. Grrxre thanked the Fellows for the reception they had given to hispaper. A preliminary sketch of the results of the recent work of the Geological Survey in the north-west of Scotland would, he hoped, be presented to the Society early next year. 74 DR. H. WOODWARD ON THE DISCOVERY OF TRILOBITES 8. On the Discovery of Tritoprres in the Upper GREEN (CAMBRIAN) States of the Penruyn Quvuarrizs, Bernespa, near Bangor, Norra Wares. By Henry Woopwarp, LL.D., F.R.S8., V.P.GS. (Read December 7, 1887.) [Prats IV.] Tur Cambrian rocks of Wales, once so barren of all evidence of organic remains, have now, thanks to the late Mr. J. W. Salter and Mr. T. Belt, to Mr. Homfray of Portmadoc, but most of all to the researches of Dr. Henry Hicks, F.R.S., at St. Davids and elsewhere, become peopled with an extensive series of organisms, amongst which the Trilobites make up a large proportion of the fauna *. It is true that the Lonemynp Gurovr elsewhere had only yielded Annelide-burrows and a portion of a Trilobite (Palwopyge Ramsayr) ; but the investigations of Dr. Hicks at St. Davids have contributed a Sponge (Protospongia major), two Ostracods (Leperditia cambrensis and L. Hicksiz), eight Trilobites (Agnostus cambrensis, Plutonia Sedg- wicku, Paradowides Harknessi, P. aurora, P. Hicksu, Conocoryphe Lyell, C. bufo, Microdiscus sculptus) ; in addition to which two Lin- gulelle and two Thece must be added. The following table shows the fauna of each formation, from the Longmynd up to the Tremadoc :— Crustacea. 2 a = : 3 = a CAMBRIAN. io) ; 3 3 : = é £ Sloe coiloei(s |S) &) 2461s | oo ae olei|s|e2|S |S) 2) \ ae a =] [oF A= S i ce] ie) — aS s/f |e (2 ele aye | sa alo;H)}/O|}Aa | a | <~/M8/H|a&/]}o 5. Tremadoc Slates.| ... | 2 | 3 ies ies a i 12 | 12) 15] 2 4. U. Lingula Flags 20) 7 bad. es 3. L. Lingula Flags 1 fg 8 4; 2 3 2. Menevian ......... = ae Viel | 25 3 ss) 1. Longmynd Group) 1 2 7 3 2 2 Dr. Hicks writes :—‘‘The Longmynd series, so well exposed in coast-sections at St. David’s, is evidently identical with that of North Wales and Shropshire, the lithological characters and the order of * No fewer than 25 genera and 85 species of Trilobites are recorded from the Longmynds to the Tremadoe Slates. IN THE UPPER GREEN SLATES OF NORTH WALES. 75 succession being strangely alike. In Shropshire, North Wales, and Treland they have yielded a few indications of life, but these districts need further exploration” *, How true was this last remark will be seen in the sequel. On the 5th August last I received a letter and box of specimens from Professor James J. Dobbie, of the University College of North Wales, Bangor, accompanied by the following statement :— “The specimens of Trilobite, Nos. 1 & 2, were found by Robert Edward Jones and Robert Lloyd, two quarrymen employed in the Penrhyn Quarry, Bethesda, near Bangor. ‘As no fossils had ever been found in this quarry before, the dis- covery excited considerable interest in the locality, and the quarry- men brought the specimens to the University College, and left them in my hands for examination. Some doubt having been thrown, by residents, upon the authenticity of the specimens, I visited the quarry along with the men on the 18th June, and examined them minutely as to the circumstances of the discovery. “The place where they allege they found the fossil is in an old working of what is known as the ‘Upper Green Bed’ of the quarry. This bed, which is about 150 feet in thickness, is the highest in the quarry. It immediately underlies the Grits forming the brow of Bronllwyd, and is itself underlain by a bed of purple slate. The fossils were found close to the junction of the ‘Green and Purple Slates.’ “The men showed me the block from which the fossil was taken, and I could detect no difference between the slate of which the block is composed, and the slate in which the fossil lies imbedded.” “Whilst searching amongst the débris close by,” writes Prof. Dobbie, “I found specimen No.3” (which has since been deter- mined to be the obliquely squeezed head of a second example of the same Trilobite, see Pl. IV. fig. 2). Prof. Dobbie adds :—‘‘ The men who found the specimen are very intelligent quarrymen, and have made some little study of geology. They were in the unused working for the purpose of examining its geology, when they discovered the Trilobite.” I think, if any doubt at all existed about the genuineness of the “find,” that is now entirely removed by the fact that Prof. Dobbie was so fortunate as to knock out a second specimen with his own hammer. The specimens have been seen and examined by Dr. Hinde and Mr. A. S. Foord, both of whom know the American Lower Palzo- zoics very well, and they do not recognize these specimens as at all resembling, lithologically, any North-American rock 7. Dr. Hinde has also pointed out that the freshness and sharpness of the specimens is opposed to their having been carried about by workmen, in which case the angles would have become abraded, and the surface of the matrix greasy from handling. Prof. Bonney was * See Proc. Geol. Assoc. 1872, vol. iii. pp. 101-103. t It had been suggested that one of the men, who had worked in slate- quarries in America, might have brought the specimens over with him, 76 DR. H. WOODWARD ON THE DISCOVERY OF TRILOBITES also so good as to look at the specimens, and considered their litho- logical character superficially to agree with the other rock-specimens of the slate sent up by Prof. Dobbie from the same bed. Lastly, Dr. Hicks, F.R.S., has seen and examined the specimens, and is quite satisfied with their genuineness, and also with my determination of the genus. . The surface of the fossil is covered with minute chlorite grains, all slightly drawn out, in the direction of the squeeze, along the friction-plane. Description of the Specimens.—The specimen from Bethesda *, found by Messrs. Jones and Lloyd on 9th April 1887, exhibits on two slabs the impression and counterpart of a Trilobite, which, when perfect, measured about 3 inches in length, and about 1¢ inch in breadth (see Pl. IV. fig. 1). The relievo side is only 23 inches long, the hinder inch having been lost in breaking the slate; but the intaglio, although injured along the side, gives us, as nearly as possible, the entire length of the whole body. The head, which is the widest part of the animal, is 12 inch in breadth by 13 inch in length; the length has, perhaps, been slightly increased by squeezing along the long axis of the specimen. The glabella is elevated and rounded in front; it is seven lines broad, and above the neck-furrow it is marked by three lateral furrows, the first or basal furrow actually crossing the glabella, and the middle and frontal furrows being each rather deeply marked and inclined somewhat backwards. The sides of the glabella are nearly parallel; it is 17 inch long, and in front of the central axial por- tion, upon its fixed margin, is a small circular raised prominence. The margin of the head-shield is rounded, and was marked by a distinct rim, and circumscribed by a furrow within the border. The cheeks are rounded and rather inflated. The posterior angles may have been produced into a short spine, but it is not preserved in the fossil before us. The facial suture appears to have run obliquely across the cheeks and united with the glabella near the anterior border, the eye (or rudimentary eye-spot) being near the centre of the cheek ; the suture emerged on the frontal border nearly in a line with the axial furrows. There are 14 free thoracic rings seen in the counterpart. The axis is 3 inch broad at its widest part next the head, and scarcely diminishes in breadth till near the pygidium, where it is 5 lines broad. Each segment of the axis appears to have been notched on its posterior border. The thoracic rings measure 14 inch across; the pleurz are straight, the extremities rounded and facetted for rolling up. The pygidium consists of about 3 coalesced segments; but the ter- mination is somewhat indistinct ; breadth 11 lines, length 4 inch. Of 25 genera of Trilobites met with from the Longmynds to the * Although the workinz is in the face of Bronllwyd, I do not think the name is ever used except for the mass of grit above the quarry (J. Dobbie). IN THE UPPER GREEN SLATES OF NORTH WALES. i Tremadoc Slates, the two most abundant forms, Conocoryphe* (with 19 species) and Olenus (with 15 species), possess many characters by which they approach one another and also the Penrhyn Trilobite. The forms of Agnostus, of which 12 have been described from these Cambrian rocks, may be dismissed here as outside the present inquiry. In Paradoxides the glabella is too much produced and globular in front, and the body-segments and the axis taper gradually to the pygidium ; there are not fewer than about 20 segments to the body. In Asaphus, Ogygia, and Niobe there are only 8 thoracic’rings ; but the caudal shield is very large, and the entire form is very broadly oval. Angelina agrees with our Penrhyn fossil very well in size, and in the number of its free thoracic segments, but its glabella is quite smooth, and the pleure are broader, and its cheek-spines are very long. Olenus has 14 free body-rings, the glabella is furrowed, but the head-shield is shorter and broader, and the ends of the pleure and margin of the caudal shield are usually more produced into spines than is the case in our fossil, and the Olenz are generally of much smaller size. | Conocoryphe, Corda, 1847 (= Conocephalites, Barr., 1852), has 14 free segments, the axis (as in the Bangor specimen) is parallel-sided, and does not diminish from the head backwards to the pygidium; each ring of the axis is notched on its posterior border; the ends of the pleurze are rounded; the glabelia is furrowed obliquely on each side; the eyes are sometimes wanting, but when present are small, and are commonly placed in the axial furrow, near the latero-ante- rior border of the glabella. Cheek-spines are sometimes absent, and when present are never very long. From these considerations I conclude to place the Penrhyn Trilo- bite in the genus Conocoryphe, and I have ventured to dedicate the species to Mrs. Dobbie, under the name of Conocoryphe Viola. It is certainly distinct from any of the 19 species already described from the Cambrian rocks of Wales or from other localities. Those who desire to consult the memoirs which have appeared on the Trilobites of this area are referred to the following papers :— J. W. Salter, 1863. Quart. Journ. Geol. Soc. vol. xix. p. 274. J. W. Salter, 1864. Mem. Geol. Surv. dec. xi. (Trilobites) chiefly Silurian. J. W. Salter, 1864. Quart. Journ. Geol. Soe. vol. xx. p. 233, pl. 13. * Conocephalus was the name originally proposed by Zenker for certain Trilobites, but it was found to have been already used by Latreille for a genus of Insects. In 1847, Corda proposed to substitute the name Conocoryphe for the first-described form of Conocephalus of Zenker, and the other species he placed under the genera Ptychoparia and Ctenocephalus. Barrande later (1852) proposed to retain Conocephalus by simply altering the termination to Cono- cephalites; but this course is not consistent with the prevalent rules of nomen- elature, and Corda’s name Conocoryphe should be adopted, even if the other two genera proposed by him are not maintained. 78 TRILOBITES FROM THE UPPER GREEN SLATES OF NORTH WALES. J. W. Salter and H. Hicks, 1869. Quart. Journ. Geol. Soc. vol. xxv. p. 51, pls. 11. & i. Henry Hicks, 1871. Quart. Journ. Geol. Soc. vol. xxvii. p. 399, Is. xv. & xvi. Henry Hicks, 1872. Quart. Journ. Geol. Soe. vol. xxviii. p. 173, pls. v.—viil. J. W. Salter and R. Etheridge. Mem. Geol. Survey. “The Geology of North Wales,” by A.C. Ramsay. Appendia on Fossils. 2nd edition, 1881. (26 plates.) London, 8vo. EXPLANATION OF PLATE IV. Fig. 1. Conocoryphe Viola, H. Woodw. Nat. size. Longmynd Group, Penrhyn Quarries, Bethesda, near Bangor. 2. Detached head of same species, squeezed obliquely by slaty cleavage (nat. size), from same locality and formation. 3. Restoration of fig. 1, by the author. (The originals of figs. 1 and 2 are in the possession of Prof. James J. Dobbie, University College of North Wales, Bangor.) Discussion. The Presipent rejoiced that the charge of barrenness had been so effectually removed from these rocks. Mr. Erneriper commented on the good work done by Dr. Hicks and others amongst the Cambrian rocks of Wales. Nothing had hitherto been found in the Bangor and Llanberis rocks. There was some question at first whether the Trilobite was more allied to the Olenidz or to the Conocephalide. Dr. Hicks said the fossils, according to the section, occurred in Lower Cambrian rocks, but the lowest fossiliferous horizon at St. David’s was yet older. The position seemed to be above the Llan- beris Slates, but at the base of the Harlech-grit series. There could be no reasonable doubt of the authenticity of the fossils. Dr. Woopwarp called attention to a diagram showing a restora- tion of the fossil. “LoDUuNg a NOL) ‘PuUMUDuUo'T “apoom HE ‘WIOIA SHAAYODONOD ‘dun ‘soig useyzupy Pe ot ee eS Se MEAG eN ileal Dy. i” i Ni iti MN n | i I I oe z oD / Fee eo ae a ON THECOSPONDYLUS DAVIESI, 79 9. On Tuxcosponpytus Davtest (Seeley), with some Remarks on the Cuasstrication of the Drnosauria. By H. G. Srutey, F.R.S., F.G.S., Professor of Geography in King’s College, London. (Read December 7, 1887.) In the Fox Collection in the British Museum is the anterior third of a vertebra, with the number = from the Wealden Beds of Brook, in the Isle of Wight, which indicates an animal of a type which hitherto has had but one other representative in Europe. With his usual acumen Mr. William Davies, F.G.S., recognized it as being the cervical vertebra of an animal closely allied to the genus Celurus of Marsh. No one would have been more competent than that veteran paleontologist to have written its history; andif I gladly undertake the task, it is because it enables me to suggest this honour to the work of a distinguished pioneer, whose labours on the Fossil Vertebrata have smoothed the way and facilitated the studies of every student of the National Collections for the last quarter of a century. Imperfect as the specimen is, it may serve as a nucleus round which knowledge will accumulate, until the genus becomes as well known as the larger Wealden reptiles. The centrum is elongated, compressed from side to side, with a flattened base, and flattened subquadrate anterior articular face, with the sides of the face prolonged backwards as subparallel sides, and as a ventral surface which is subparallel to the neural canal. The cervical ribs are co-ossified with the centrum and neural arch. The bony tissue, not unlike that of Ornithosaurs for its relative thick- ness, forms a dense external film, which defines the form of the bone, and is connected with some delicate internal supports in the cham- bered neural arch ; so that there is no solid tissue in neural arch or centrum, and the densest layer is the film around the large neural canal. The neural arch forms a long pent-house ridge, which is penetrated in front above the neural canal by a large subtriangular cavity. The only European genus hitherto described in which the ver- tebre are similarly elongated, compressed from side to side, and enveloped in a dense external film of bone, is that indicated by the sacrum named T'hecospondylus Hornert. The internal mould of that specimen, and the fragmentary vertebra of this, are confessedly scanty materials for comparison; but as they agree in characters which define them from all other animals, I believe it will be legiti- mate to refer both to the same genus, though there is the possibility of their belonging to distinct genera which are nearly allied. In the type of T'hecospondylus Hornerz the sacral vertebre are about 11 centi- metres long, andl estimate the vertebra about to be described as having been 9 centims. long, so there is no great difference in size. But since T'hecospondylus Hornerz has the sacral vertebra convex trans- 80 PROF. H. G. SEELEY ON versely on the ventral aspect, while the ventral aspect of this verte- bra is transversely subquadrate, I regard the remains as indicating distinct species, because I have often noticed among Ornithosaurs that the flattened or rounded ventral condition, as the case may be, in the cervical region also obtains in the sacrum. Fig. 1.—Anterior aspect of the vertebra, which has lost the pre-zygapophyses Fig. 2.— Right lateral aspect and cervical robs. of the same specimen. Fig. 4.—Polished vertical sec- Fig. 3.—Ventral aspect tcon of the vertebra, showing showing the base of the the chambers in the neural centrum. arch and centrum. a, articular face of centrum, showing coarse cellular tissue on its slightly worn margin ; p, attachment for the cervical ribs on the centrum; d, attach- ment for the cervical ribs on the neural arch; n.c, neural canals pn, pneumatic foramen; N, cavity in neural arch, and corresponding air- chamber in fig. 4; sn, supra-neural air-chamber; uy, lateral air- chamber in the neural arch; c, centrum. THECOSPONDYLUS DAVIESI. 81 The anterior end of the vertebra (fig. 1) is imperfectly preserved, having lost the cervical ribs and adjacent tissue of the neural arch to which they were attached, as well as the adjacent prezyga- pophyses. If these parts were restored they probably would ap- proximate in shape to those of Calwrus fragilis, Marsh, except that the lateral extension of the ribs was less, and their supra-neural development was much less, for the lateral expansion of the neural arch has a relatively higher position than in that genus. As pre- served, the anterior aspect of the bone is remarkable for narrowness relatively to its height. The articular face of the centrum (fig. 1, a) is flat or slightly concave, inclined slightly forward, subquadrate, being horizontal on the neural surface above, vertical laterally, and on the base it is concave from side to side, owing to the anterior corners having a downward development to form the basal attach- ments for the cervical ribs (fig. 1, »). The transverse width of the articular face of the centrum is 19 millim., and its vertical depth in the middle is about as much. ‘The margins are somewhat worn, and show large cells defined by delicate tissue. The subtriangular facets of the cervical ribs at the inferior anterior corners of the centrum are probably but little worn, and in a line with the original sutures. They are oblique, and look downward, forward, and outward, and measure 13 millim. long by 9 millim. wide in front, where they are separated by an interspace of half a centi- metre, which is convex as it descends from the articular surface on to the base of the centrum. The surface of the rib-facets is divided into two or three cells. Above the articular face of the centrum is the transversely ex- panded subhexagonal entrance to the neural canal, 2°5 centim. wide and half as high in the middle, where the thin transverse bony plate which forms the upper limit of the arch extends from side to side with a downward curve. The neural canal itself (fig. 1,N.c) is higher than wide. The lateral angular expansions or antrum in front of the canal contain on each side an oval transversely oblique foramen (pn), which was probably pneumatic. It is situate in the lateral angle of the arch in such a way that the bone above it ap- pears as though excavated, and that below it descends to form the stout pedicle of the neural tunnel,which has a transverse measurement of half acentimetre. The plate which limits the neural canal above is 8 millim. behind the articular face of the centrum. Upon this plate is a large aperture of a cavity in the neural arch, apparently penetrating conically, which is only inferior in size to the neural eanal. It is 12 millim. wide at the base, and about 8 millim. high, with the sides converging upward to a transverse width of halfa centimetre, while the upper border is 2 centim. behind the articular face of the centrum. The cavity penetrates far into the bone, and I regard it as having given attachments to ligaments which were attached to the extremity of the neural spine. The whole supra- neural region retreats backward as it ascends. Above this neural cavity is a circular foramen about 4 millim. in diameter, which assists in completing the triangular contour of the area above the eos. GS, No. -173, G 82 PROF. H. G. SEELEY ON neural canal (fig. 1, , sn). The lateral margins of this triangular area are approximately parallel to the external surfaces of the neural arch; only much of the external bone is broken away with the cervical rib which it supported. The interval was occupied by lateral air-cavities, one on each side, which included some delicate supporting bony films, The four supraneural chambers thus indi- cated appear to extend longitudinally throughout the neural arch. The superior external surface of the neural arch is very imperfect. In the median line it forms a longitudinal blunt ridge from which the smooth flat lateral halves of the neural arch diverge outward at a wide angle (fig. 4), becoming convex as they descend, and ter- minating outward in a blunt ridge, which ascends from the hinder border of the diapophysial attachment of the rib, and defines the upper border of a large lateral concavity on the side of the arch, like an impression of the finger (fig. 2). Its lower half rests against the upper haif of the neural arch, and its upper part, which has a thin wall, is bounded by the lateral air-chamber of the neural arch. There is a small foramen in the upper anterior part of the concavity. This concavity is bordered below by a strong longitudinal ridge, which is placed below the middle of the side of the neural canal (fig. 4). As this ridge extends forward it expands to form the anterior border of the concavity, which is 2°5 centim. behind the articular face of the centrum. It is prolonged further forward, de- creasing in height (fig. 2). Its inferior surface is horizontal and sinuous ; as preserved, it is 2 centim. long. The greatest transverse measurement on it, through the centrum, is 2°5centim. It is apparently upon the line of junction of the neural arch with the centrum, 13 centim. from the base of the centrum, and 24 centim. from the median ridge of the neural arch. The remainder of the neural arch is badly preserved, and does not admit of description. The region below the neuro-central ridge is the side of the cen= — trum. Anteriorly it rises into the bases of the pedicels of the neural arch, which curve obliquely outward and upward towards the rib (fig. 2). So much of the side of the centrum as is pre- served is approximately vertical, concave from the neuro-central ridge to the angle at the base of the centrum, and more gently concave from front to back. At more than 13 centim. behind the articular face, and half a centim. from the base, is a transversely oblique foramen, over half a centim. long, margined superiorly by a slight arched border (fig. 2, pn), which extends beyond it. This was probably covered by the cervical rib, and appears to have been pneumatic. ‘The least transverse measurement in the middle of the centrum is 8 millim. at the posterior fracture (fig. 4). There is a slight constriction anteriorly at the base of the neuro-central angle, so that the centrum bulges a little below it. The base of the centrum is elongated, flattened, with concave sides. Itis concave transversely, and widened anteriorly (fig. 3) by the development of the parapophysial tubercles for the rib, which extend the base till it is as wide as the centrum. At the posterior fracture the transverse measurement is one centimetre, so that it THECOSPONDYLUS DAVIESI. 83 has become narrowed to about one half of the anterior width. br Be H | A = = LAMELLIBRANCHIATA. R Astarte tenera, Morr. Cardium. Morbi, Arnouldy, NYSE 2. cnssanonanp ri sas * *-—— regulbiensis, Morr. ............. eae x | % % Crassatella, sp. *Cucullza crassatina, Lamk. ............ * *% % PeOypanina Moririsii, SOy: \ scssededes. -cadees * x * scutellaria, Desh.? ........ CMS eth Se * * *% «Cytherea orbicularis, Edw. ............... ? * xGlycimeris rutupiensis, Morr. ......... * Leda substriata, Morr. Lucina, sp. Modioia, sp. -xNucula Bowerbankii, Sby. ..........+.++ x ABs ve * cardioides, Kdw. Greeias, Weshs lh SE A x * % margaritacea, Lamk.? ..........+. ni ah td x sextans, Edw. thanetiana, Edw. Ostrea cymbuloides, Wood. xPanopea granulata, Morr. RxPecten Prestwichii, Morr. xPholadomya cuneata, Sby, ......... 2.666. x x— Koninckii, Nyst ........ccccceee eee * Pinna, sp. xSanguinolaria Edwardsi, Morr. ........ x * x Saxicava compressa, Hdw. Mhracia oblata, Sy soes casio: ssewenssonsenes and Mae * x G-ASTEROPODA. Calyptreea trochiformis, Lamk.? ...... be gece bok yp uge * Dentalium nitens, Sby.?.............s.0.- Biss ds Bea * Eulima, sp. Fusus, sp. Natica subdepressa, Morr, .............0. Ee a * Rostellaria, sp. ? | RxScalaria Bowerbankii, Morr. ............ % RxTrophon subnodosum, Morr, ) | 10 | 5 Ve 8 t To these are added four (marked R) from my original collection from the Reculvers. 94 PROF. J. PRESTWICH ON THE CORRELATION OF THE It would appear, therefore, that out of the 28 Pegwell-Bay species, there are 10 common to the Lower Landenian, 12 pass up into the Woolwich Beds, and 6 extend to the London Clay, while only 5 are common to the Bracheux Sands. Tuer SABLES DE BRACHEUX. The exact determination of the horizon to which these sands be- long is of importance, not only with respect to the synchronism of the Lower Eocene groups in the London and Paris Basins, but also for fixing the age of the very interesting Mammalian and Avian faunas discovered by M. Lemoine in the neighbourhood of Rheims, of the curious freshwater deposit of Rilly, and of the rich flora of Sézanne. I only regret that in putting forward my views on this subject I have to differ on many points from some of my friends abroad and at home. These differences are, however, as they know, not of recent date, and have often been discussed by us, and I should not have ventured upon expressing so wide a divergence of opinion unless I had hada long acquaintance with most of the localities concerned. It was fortunate for Tertiary geology that Beauvais possessed an excellent local geologist (M. Graves), whose work on the Depart- ment of the Oise, though without map or sections, is full of most complete and accurate details of every part of the Department, with the names of all the localities at which every fossil is found *. He divided the Lower Tertiaries of the Oise into three groups, which I give, with the names by which they have been subsequently known :— Glauconie Supérieure = Glauconie Grossiére forming the base of the Calcaire Grossier. Sands of Cuise-la-Motte, and possibly other zones. Glauconie Inférieure and Lignites = Sands of Bracheux; Lower zone of the Sables Inférieurs. | Glauconie Moyenne M. Graves makes the Lignites subordinate to the Sands, and it is the lower bed of these sands, which is about 30 feet thick, that forms the knoll at Bracheux. The Lignites and mottled clays cap this bed in other places, and they are in turn surmounted by another bed of from 10 to 20 feet of sand, with many of the same shells, such as Ostrea bellovacina, Pectunculus terebratularis, Nucula fragilis, Turritella edita, Cytherea obliqua, Natica glaucinoides, &c. The characteristic fossils of the Lignites are Cyrena cuneiformis, Palu- dina lenta, Cerithium variabile, Melania cuneiformis, Ostrea bello- vacina and O. sparnacensis. * «Essai sur la Topographie Géognostique du Département de l’Oise.’ Par L. Graves. Beauvais: 1847. EOCENE STRATA IN ENGLAND, BELGIUM, AND FRANCE. 95 The Glauconie Inférieure presents a marked analogy with the Woolwich Series, where we also have two beds of fossiliferous marine sands divided by fluviatile carbonaceous clays and thin lignites. The deposits are also alike in lithological character, that of Beauvais consisting of white and light-green sands, often very pebbly, while the carbonaceous clays form large lenticular masses in the middle of the sands. There is also the like passage, on the same level, of massive mottled clays into sands, and of sands into pebble-beds. The fossils, which abound in some places and are absent in others, are subject to similar variations, dependent upon variability of con- ditions. Further this Glauconie Inférieure is replaced in the neigh- bourhood of Paris, as the Woolwich Beds are in the neighbourhood of Reading, by red and mottled clays with a few beds of sand. There is, however, this difference, that while the bulk of the fossils in the Woolwich Series are in the sands above the fluviatile clays, those in the Paris Basin at Beauvais are in the lower division of the sands; but, as at Woolwich, while there are a few species peculiar to either bed, the greater part are common to the two. M. Graves enumerates 82 species* of Mollusca from the different localities of these sands in the Oise; but his list was made before the publication of Deshayes’s last work on the shells of the Paris Basin, in which many rectifications were made, both in the names of species and in their range. Consequently the list requires con- siderable revision. Deshayes, in that work, gives the names of all the localities from which his specimens came. It is by taking all his Bracheux specimens in combination with Graves’s specifications that the following list (p. 96) has been drawn up. It will serve as a truer term of comparison than Graves’s original lists. Here, out of 45 species, only 6 seem to be common to the Thanet Sands, and 5 to the Lower Landenian, whereas there are 10 common to the Woolwich Series. The numbers are not larget, but the balance in favour of the higher horizon is clear; and if the Lignite species are to be included with them, as by M. Graves, the case in favour of their synchronism becomes stronger. The absence in the Thanet Sands and Lower Landenian of such characteristic forms as the Cardita pectuncularis and others, is an additional piece of evi- dence that the two zones are distinct. In fact out of the 8 Bracheux species selected by M. Graves as characteristic of the Bracheux Sands, only 2 occur in the Thanet Sands and Lower Landenian. * This includes a number of freshwater species, some of which are given in the second list. t If we had taken the beds of Abbecourt and Noailles, which belong to the same zone as the Bracheux Sands, it would have increased the number of species, but would not materially have altered the proportional distribution. 96 PROF. J. PRESTWICH ON THE CORRELATION OF THE B. Mollusca of the Sands of Bracheux, near Beauvais, with their range in time. (The asterisk marks the more characteristic species according to M. Graves.) LAMELLIBRANCHIATA, *Cardita multicostata, Lamk. ......... * pectuncularis, Lamk. Cardium hybridum, Desh. ............ Edwardsit, Desh. .......0c....-- | (C. semigranulatum, Sby.?) ...... wa Corbula regulbiensis, Worr. ......... | obliquatas Desh. «04. crea +dincase xOrassitella bellovacina, Lamk. ...... xCucullea crassatina, Lamk. ......... incerta, Desh. ? | xCyprina scutellaria, Desh. ............ Cytherea bellovacina, Desh. — obliqua, Desh. ...........:.eceeeee- PLOKIMIA, PIES oon... 00 ca pecenenee fallax, Desh. Fimbria (Corbis) Davidsoni, Desh. Lueina contorta, Defr.............04 i Brata, Dry oe, Moss ls HW, oe ets, PUICLTE oo. ccc cesine ccs tte uneimata, Der. Weiss ab.dsee Nueulacitagilisy Desh. 2c. 028. doce. .0e: xOstrea bellovacina, Lamk. ............ Panopzea remensis, Desh. ............ *Pectunculus terebratularis, Laméh.... | Psammobia (Saneuinolaria) Ed- WS MGI ohn deems wbite oy GASTEROPODA. | t | Buecinum latum, Desh. Bulla angy on Desh. Calyptrza suessoniensis, D’ Orb. ...... Cerithium bellovacinum, Desh, — gibbosum, Defr. obesum, Desh. Dentalium striatum, Sby.? ............ Pyrula (Ficula) Smithit, SUL Dee eee Carried forward ..c.c.c.s keecceeecc | Thanet Sands. D Lower Landenian of Lincent. *K Ks sad Upper Landenian. Upper Landenian. Upper Landenian.| I Chalons-sur-Vesles, | Woolwich Beds. « Jonchery, &e. Sands of Cuise. Bognor. | Elsewhere. Nice. Nice. EOCENE STRATA IN ENGLAND, BELG1OM, AND FRANCF, 97 B. List of Mollusca (continued). a a ra = a |O S| os ai Bo 3 |Fs! 2 By ee al Ale Bh 3S ao s fia) O oS Hs ot a cet) Fe 3 2 Bie ol bith ence Lei, lak a eo oO |= 0) cs 3 = le) ° Sk =| Q | fo} iS 4 o il A 4 o 2) - Broucht forward .......c.....,00.: aa aa G LRG Oy GASTEROPODA (continued). Mélania plicatula, Desh. Natica abducta, Desh. .........00.. .0.. * ——— Deshayesiana, Nyst............... x * infundibulum, Wat. ............ aa * —— semiplicata, Desh. ............00. aa ee sen hee Rostellaria callosa, Desh. / Tornatella parisiensis, Desh. ......... % X Turritella bellovacina, Desh. ......... | jar: MA, ISM a2 a vem yen-omainn.daes athe | # * Voluta depressa, Lamk. .............4. me sae AGUS: jo UO A indie a me SN UN Pseudoliva fissurata, Desh............. Ph aah ut % * | | 6 5 10 | 25 6 The fossils of the fluviatile and estuarine clays and lignites, which seem to bear the same relation to the Bracheux Sands that the fluviatile beds of Woolwich do to the sand- and pebble-beds below and above them, present a still closer analogy with the fossils of the Woolwich series, as the following list of some of tae most charac- teristic of the Beauvais (Lignite) species will show :— Woolwich. | 7 Upper andenian, Cerithium funatum, Mant. (C. variabile, Desh.) ... * Mipienin nmquinatay D2... 55. ..s. cn todieed- : 5 H i ) 1 H { lech ; H 1 | z 1 i eI I = | Ht “| | : ty} ; s Hh | | i ob! ‘ Vy ! i ieee ry ed | He 1 E : i 5 ! | L i! >! : ™ : 1 ! : ie : , , iy | : : : ! 4 ' | 3 ‘se &Q rel ' rt — : , ru 2 Sica | i fiom | : 1 i} py | : no ae a 1 . 3 Quart. Journ Geol. Soc Vol. XLIV. PL. v FIG.|. TypicaL SECTIONS OF LONDON TO THAT OF BRUSSELS. Bagshot London Sundridge Upper Bagshot Mddle Bagshot Lower Bagshot olden Sands London Clay. 2 lanul aes . rl Oldhaver or- t ' Basement Bed. = = E Reading one and SS Woobeuch Beds : a Reem | Lower Ypresian. E SSeS: = an ectuncudla s as e ‘ 4 Quah. \—* = 2 be sea | Thanet : Mo a om we 7B ia ee 3 PSs) UpperLandeian wed : and Cyprina ipa ae a i Morrisii 7 ea Mons Wh KI London, Woobrich (Cea) Poteet ne 1D) ; | a Hons-cr-Pivile Upper Bagshot ; eae ee ; (Orchis) Middle Bagshot. 0} i pee | ; Lowa Bagshot a erLondon Sands London. Clay Planulatus Basenait Bed. = —— fabeih Wal maaA Game Diag niet arid Usa Heathing Bods | a ; : ae a Ee ag] Uncle hare Saruds Z i : Pholadomya : 5 poe : 4 Thanet Saruds a 4 ; Koninckii Lower Landenian Chall ; ; Vartiral. Scale, 4 inch = 100 feeb. Dancerrieto Lith 22 Beorono S'CoventGanoen, 7.88.15600. * 1 ; N } ones otrhdit weirag egpestrtadcned tevin. 40 hd tenor n= Ahan nea efoto ry aa ntnme nnd ide uy connor sows U eelin tho feb uecule a : t arty ; , 4 * , ir 2 i ; e ' hy , a" | ‘ s i é x Fi , , er 4 ~~ ’ T Ute, a y “ 5 + ’ ‘ i ’ i ’ ' ‘. : nl het A . i ox 2 a ov it , Laidnnve Hevie “it / ; re | we Aye wpe i a8 vs : MP Ty Foamy 4 { sien! iyi } h : ee ea aT TE us aii ‘ : oe 4 Vac \ ' f 4% d ; Wy SE f ‘ ey aay Le r secciaiil . ep aage ty Neil ty tbe Re 4 1 J \ Ai Me if ru EOCENE STRATA 1N ENGLAND, BELGIUM, AND FRANCE, 111 Mr. Garpyer contended that the Reading Beds should be allowed to come in as a separate formation. They were now shown to be quite distinct both in matrix and fossils from the Woolwich Beds, being characterized by a separate flora. For the sands above the London Clay in the near neighbourhood of London the proposed name was good; but these were not very extensive, as fluviatile conditions were soon reached. In classification we should separate the marine sands from the entirely freshwater series. He quite agreed that the Lower Bagshots of Alum Bay should be placed in the Lower Eocene. He was not prepared to see the Middle Eocene effaced.. In the Upper Bagshots of the London Basin, Barton forms decidedly preponderate. This has been further confirmed recently by the discoveries of Mr. Herries. The Avruor, after alluding to the friendly reception accorded to his paper, observed that with Mr. Whitaker his differences were slight, and while restricting the vertical dimensions of the Oldhaven Beds in the neighbourhood of London, he admitted their greater im- portance in East Kent, and considered the term there a better one than “ the Basement-bed of the London Clay.” Fossils might easily have been dissolved out in some of the sandy pebble-beds. He did not consider the evidence doubtful, but thought it not strong. He indicated how the mottled clays of Reading became replaced by sands and pebble-beds as they ranged past London. With regard to the Tufeau de Ciply, that was classed by the Belgian geologists at the top of the Cretaceous series. The tables exhibited were confined to the Eocene series. | 112 PROF. T. M‘KENNY HUGHES 11. On the Car Gwyn Cave. By T. M*Kenny Hueues, M.A., F.G.S., Woodwardian Professor of Geology, Cambridge. (Read November 23, 1887.) Ix a communication which I made to the Society “ On the Drifts of the Vale of Clwyd and their Relation to the Caves and Cave- deposits ” *, I considered the subject under the following heads :— (1) The Age of the Drift. (2) The Relation of the Deposits in the Caves to that Drift. In discussing the age of the drift, 1 was of course obliged to offer a tentative classification of the Pleistocene deposits of the district, in order to show the relative position and age of the St. Asaph beds, to which I referred the drift on the flanks of the hill in which the Ffynnon Beuno Caves occur. The classification I suggested has been called in question, and I have relegated the discussion of this part of the subject in its wider bearing to a separate paper. It will be desirable, however, to restate briefly the conclusions at which I then arrived. They were :— That the interpretation of the glacial phenomena of North Wales is much more simple than that suggested by most recent observers in East England. That we have evidence of the following sequence of events :— That glacier-ice came down from the Snowdon and Arenig group of mountains, riding across pre-existing north and south valleys as far at any rate as the Cheshire plain on the east, and as far as the Trish Channel, which was the corresponding north and south valley on the west. That glacier-ice came also from the north and held back the Welsh ice along the whole of the north coast; that it once sent a tongue further down the Irish Sea and, perhaps, another down the east side of Wales towards the “ Severn Straits”; that this north- country ice was melted back when the Welsh ice was receding, so that it never left any moraine matter far south of the coast-line. That there may have been interruptions in the movements, but that there is no evidence of any interglacial age. That there was a submergence of the mountain lands, southern Mollusca coming in as the sea advanced and the glaciers were melted into the recesses of the Welsh mountains, and the more northern forms following the ice as it receded to the north. That there was a great denudation of the old glacial deposits and a using up of the morainic deposits of both northern and western ice along their ancient line of contact. That there was never again any ice action in the Vale of Clwyd different from what may be seen at the present time in the estuary | of the Dee. * Quart. Journ. Geol. Soc. 1886, vol. sliii. p. 73. ON THE CAE GWYN CAVE. 118 In this paper I shall only bring forward the additional evidence which has been obtained bearing upon the age and origin of the marine drift near Ffynnon Beuno without going far into the question of the place of those beds among the Pleistocene deposits of North Wales. From an examination of its lithological character and mode of occurrence, I referred the main mass of drift outside the Cae Gwyn Cave to the second stage; that is, I considered it to be post-glacial, and of approximately the same age as the St. Asaph drift. This view, however, was disputed. It was asserted that ‘ the high-level drift at Cae Gwyn is a true undisturbed glacial deposit,” while it was allowed that the St. Asaph drift ‘‘ must certainly be considered the newest, as it is mainly remanié.” But no satisfactory expla- nation was offered of the mixture of granite and flint with the western fragments, on which I chiefly relied for the identification of the Cae Gwyn deposit with the St. Asaph Drift. The views I then put forward have been fully sustained by the observations made during the last summer. We have again to record our thanks to Mr. Morgan, of Cae Gwyn, for allowing us to carry on the work, and for much kindness during its progress. There are many caves in the Ffynnon Beuno gorge. There is the large cave (to which it has been proposed to confine the name Ffynnon Beuno), which was occupied by cattle when first I knew it. There is the upper cave, now spoken of as the Cae Gwyn Cave, along the lower or southern opening into which a small quarry has been opened. There is a cavernous mass behind the cottage on the opposite side of the gorge, two of the caves in which I have referred to and figured in illustration of the mode of formation of the Cae Gwyn Cave; and in the potato-garden behind Ffynnon Beuno Inn there is a cave, probably one of a system running down in a westerly direction with the fall of the rocks towards the Vale of Clwyd. These last are probably flushed by water in every flood, and connected with the drainage-system which feeds St. Beuno’s well. The latest excavations in Cae Gwyn Cave have shown that that cave extends in a northerly direction, dropping in all probability by swallow-holes to the level of the lower and larger cave mentioned above. The literature of the subject is beginning to assume considerable dimensions, not only because different observers approaching the phenomena from different points of view have arrived at different conclusions, but also because the progress of discovery has brought to light new evidence from time to time, and inquiries into analo- gous cases and into the sequence of events elsewhere in Pliocene and Pleistocene times have furnished arguments in support of the various interpretations put upon the facts brought to light during the excavations, The first notice is, I believe, the Report of the Excursion of the Chester Society of Natural Science, published in the ‘Chester Chro- nicle’ of July 28, 1883, when, in the course of my observations on Q.J.G.8. No. 173. r 114 PROF. T. MSKENNY HUGHES the district, | made a few remarks on the Ffynnon Beuno Caves, which appear thus in the report :— ‘They found another kind of deposit in a cave nearer to Tre- meirchion. There were recent deposits in it, and recent animals . . . (to wit a black sheep), but at the end there was a deposit of that brownish earth commonly known as cave-earth, in which they found the remains of the sheep of earlier days. In ancient times the remains of stags would be found there, and in still more ancient times those of hyzena, and of other animals of that time which the hyznas found in the woods below and dragged in there. ... If permission could be obtained, he proposed to visit that cave some day with the members . . . . perhaps they would find the remains of primeval man, and certainly some of the extinct animals.” The bone-earth had been disturbed by mining trials along the fissures which had determined the position of the caves, and thus fragments of bone from the lower cave-deposits were lying on the surface. The only recognizable remains found on that occasion belonged to Bos and Hyena. In the following month Dr. Hicks partially explored these caves, and made a further examination of them in the autumn of the next year. He gave the results of his investigations in an interesting paper read before the Geologists’ Association in Noy. 1884*. He notices the dissimilarity in the character of much of the material which had apparently filled these caverns before they were explored and that with which he was conversant in those of South Wales, pointing out that it is identical in appearance with the upper Boulder-clay in this area, especially that about St. Asaph, and that it contains the same derived boulders. The bones, he adds, are in disturbed positions, and filled by material unlike that in which they now lie. In this earth, associated with bones of reindeer, a flint flake was found, respecting which he quotes the opinion of Dr. Evans that it is of the La Madelaine or newest paleolithic type. Dr. Hicks explains that the flake, like the bones, was “evidently not in its original position, but had been disturbed by water-action and had been carried there from some other point in the cavern ”.—a fact of considerable importance undoubtedly, as it showed that the dis- turbance of the cave-deposits which he observed there was later than the reindeer age. At the meeting of the British Association at Aberdeen, Dr. Hicks read a paper on these caves, in which he gave some further details as to the character and mode of occurrence of the deposits. In the first sentence of the first paragraph in his description of the Cae Gwyn Cave, where he says that ‘all the deposits were entirely undisturbed, except by burrowing animals, when we first discovered it,” he means, of course, that the deposits had not been disturbed by man, because a few lines lower down he offers reasons for believing “ that the water-action which disturbed the original materials in the * Proc. Geol. Assoc. vol. ix. 1885, p. 1. +t Rep. Brit. Assoc. Aberdeen, 1885, Trans. Sect. C, p. 1021; Geol. Mag. 1885, dec. 3, vol. ili. p. 510. ON THE CAE GWYN CAVE, 113 cave must have been of a violent nature,” and infers “ that during a period of great submergence either during, or subsequent to, the glacial epoch, the material was introduced by marine action.” He quotes Dr. Evans’s opinion that the flint flakes found in the lower caves were “of the type of the wrought flakes found in Kent’s Cavern.” A list of the animals whose bones were discovered is given on the authority of Mr. Davies. These views were more fully set forth in a paper read before the Geological Society, in November 1885 *, in the discussion on which Dr. Evans and Professor Boyd Dawkins expressed their doubt as to the author’s conclusions respecting the evidence of marine action in the caves. Dr. Hicks communicated the results of some further excavations in a short note which appeared in ‘ Nature,’ July 1886 +, in antici- pation of the full report which he drew up for the British Asso- ciation meeting at Birmingham ¢ in the September following. In these papers he describes what he considered to be the “ abrupt termination”’ of the cave “in a plateau of glacial deposits” at what must have been the main entrance into the cavern when it was occupied by the Pleistocene animals, and states his belief that “the glacial beds in and upon it must have been deposited subse- quent to the occupation by the animals,” and “ that the contents of the cavern must have been washed out by marine action in midglacial time, and that they were afterwards covered by marine sands and by an upper Boulder-clay.” He further notices that ‘‘ within the entrance there was a greater thickness of sand, less of laminated clay, and more bone-earth than in other parts of the cavern,” and that the bone-earth seemed “to diminish in thickness rather rapidly outwards under the glacial deposits.” He also brought the matter under discussion in Section H §. At the same meeting || I pointed out the distinction between the land-ice drift of the Western Mountains and the Marine Drift, which I considered to be of much later date and due to the destruc- tion of the older glacial beds; and then offered reasons for be- levying that none of the bone-deposits yet found could be referred to as early an age as even the marine drift. I communicated the substance of this paper to the ‘ Geological * “Results of recent Researches in some Bone-caves in North Wales (Ffynnon Beuno and Cae Gwyn),” by Henry Hicks, M.D., F.R.S., F.G.S., with a Note on the Animal Remaius, by W. Davies, F.G.S., Quart. Journ. Geol. Soc. Feb. 1886, vol. xlii. p. 3; Reported in abstract, Geol. Mag. Jan. 1886, dec. 3, vol. iii. . 39. f ‘‘ Evidence of Man and Pleistocene Animals in North Wales prior to Glacial Deposits,” ‘ Nature,’ vol. xxxiv. 1886, p. 216. t “ Report of the Committee appointed for the purpose of exploring the Caves of N. Wales,”. drawn up by Dr. Hicks, Secretary. Brit. Assoc. Rep. Birmingham, Sept. 1886, p. 219. § ‘‘ Evidence of Preglacial Man in North Wales,” Brit. Assoc. Rep. Birm- ingham, 1886, Trans. Sect. H, p. 839. || “On the Pleistocene Deposits of the Vale of Clwyd,” Brit. Assoc. Rep, 1886, Trans. Sect. C, p. 6382; Notices of ditto, Geol. Mag. Nov. 1886, dec. 3, vol. iii. p. 509. 3 a 116 PROF. T. M‘KENNY HUGHES Magazine’ in November *, especially noticing that the blocking of the upper opening seemed to have taken place gradually, and that while it was going on drift-material was washed into the cave, and various objects got into the crevices of the broken limestone—my point always being that the upper opening was not stopped by undisturbed drift, but by moved and slipped portions of the drift and of the over- lying head or rainwash; and that even if it had been blocked by undisturbed drift, such as lay on the hill-side near by, that would not prove the contents to be preglacial, because that marine drift was not laid down till after glacial conditions had entirely ceased to prevail in that district. I explained my views on the subject in a lecture delivered at Chester in October 1886+, in which I pointed out that the cha- racter of the drift was not such as to allow us to refer it to an ordinary beach-deposit, but it must have crept down the hill-side either subaerially or into deep water, where there would not be the same sorting of the material as is usual on such a coast; that the drift which finally closed the cave was in its upper part superficial talus, and below that moved marine drift, but that there was a com- munication with the cave from the surface by swallow-holes down to quite late times. In November of the same year I read a papert before this Society, in which I discussed more fully the characters of the various drifts in the district, giving my reasons for assigning to the deposits outside the Cae Gwyn Cave a place among newer series which I considered not to have been laid down until after glacial conditions had passed away from that area. I gave full lists of shells from the marine drifts of that and adjoining areas, but at that time the shell- bearing bed at Cae Gwyn had not been touched. I again stated my reasons for believing that the drift-deposits outside Cae Gwyn Cave were not a true beach, but the result of the working down the slope cf débris from the drift, first into deep water, and subsequently sub- aerially ; and that “ the drift which finally c’osed the mouth of the cave” (p. 110) was not even as old as the marine drift, but that some of the material was a mere superficial talus, that some of it was the moved drift (p. 104) which had sunk into an irregular swallow-hole, and that all the drift which overlapped the bones had settled down on them in consequence of this swallow-hole action long subsequent to the deposition of that drift (p. 109). In the ‘Geological Magazine’ of December 1886, Dr. Hicks § reprinted the Report which he had drawn up for the Meeting of the British Association at Birmingham, with a long footnote commenting upon the observations I had made on the subject. He states that the accumulation against the upper side of the old - : On the Ffynnon Beuno Caves,” Geol. Mag. Nov. 1886, dec. 3, vol. iii. : ae Caves and Cave Deposits,” ‘Chester Chronicle,’ Nov. 6, 1886. + “On the Drifts of the Vale of Clwyd and their Relations to the Caves and Cave Deposits,” Quart. Journ. Geol. Soc. vol. xliii. 1887, p. 73. § “On the Ffynnon Beuno and Cae Gwyn Caves,” Geol. Mag. Dec. 1886, dee. 3, vol. iii. p. 566. ON THE CAE GWYN CAVE. T7 fence to which I had referred “is merely material conveyed there during the explorations.” He objects to the same name being applied to “the true glacial deposits” “at the entrance to Cae Gwyn Cave” and to the drift about St. Asaph, which ‘is in the main remanié.” “The Cefn and Plas Heaton Caves” are, he goes on to say, “so near to the rivers that” he does “ not think the evidence furnished by them can be quoted as of much value either way.” He combats the paleontological evidence which I had adduced from what I considered the late Pleistocene facies of the mammalian remains, on the ground that ‘a large proportion of the animals occur in the Norfolk Forest-bed.” In December 1886, Dr. Hicks* also read a paper before the Geologists’ Association in which he questions the possibility of dis- tinguishing the various drifts of the Vale of Clwyd, and quotes Mr. Strahan in support of his view. He restates the case for the preglacial age of the deposits in the Cae Gwyn Cave. In February 1887, I read before the Victoria Institute a paper in which I described the mode of formation of caves and cave-deposits, and referred to the Cae Gwyn Cave and the analogous case of the Victoria Cave in Yorkshire, in both of which I believe that beds which are the result of ordinary subaerial and subterranean agencies have been attributed to direct glacial action. . Mr. E. T. Newton + published a note on the Cae Gwyn mammals in the ‘ Geological Magazine’ of February 1887, in which he pointed out that all the Ffynnon Beuno mammals were found in undoubted Pleistocene. The Lion, Reindeer, and Woolly Rhinoceros occurred in the Ffynnon Beuno caves, but were not found in the Forest- bed, while A. etruscus, Trogontheriwm Cuviert, Myogale moschata, Elephas meridionahs, Cervus Sedgwicku, C. verticornis, C. poliqnacus, C. Savini, characteristic Forest-bed mammals, were none of them found in the Ffynnon Beuno caves t. In the following number Dr. Hicks§ replied, endeavouring to explain the discrepancy by reference to the general absence of cave animals in ordinary sedimentary deposits and vice versd. He urged that “if the Forest-bed is proved to be of preglacial age, be- cause it is covered by glacial deposits, then certainly we can claim the remains found in the Ffynnon Beuno cave to be of preglacial age, since they also were completely covered over by undoubted glacial deposits.” At the Meeting of the British Association at Manchester ||, Sep- tember 1887, Dr. Hicks presented the “Second Report on the Cae Gwyn Cave,” in which he described the progress of the further exca- vation the results of which are now being laid before the Society * Proc. Geol. Assoc. Feb. 1887, vol. x. p. 14. t+ “The Ffynnon Beuno Cave,” Geol. Mag. Feb. 1887, dec. 3, vol. iv. p. 94. A review of the subject at this stage is given by Koken, Neues Jahrbuch, 1887, Band xi. pp. 487-489. { See also Quart. Journ. Geol. Soe. vol. xliii. p. 110. § Geol. Mag. March 1887, dec. 3, vol. iv. p. 105. || Brit. Assoc. Rep. Manchester, 1887; ‘ Nature,’ vol. xxxvi. Sept. 29, 1887, p. 516. 118 PROF. T. M‘KENNY HUGHES for discussion. He gave also a list of the shells found in the drift outside the cave. In October 1887, the President of the Liverpool Geological Society, Mr. G. H. Morton, in his presidential address*, referred to the work which had been carried on in the Ffynnon Beuno Cave, during the greater part of which he had been present, and gave it as his opinion that “the bone-earth represents the preglacial period, and the bed of stalagmite the cold period, when North Wales was glaciated and uninhabited....when the land subsided....the force of the waves .. broke up the stalagmite floor... . disturbed the bone-earth, and drove the bones and teeth before it, so that these were not only found in the bone-earth, but forced into hollows and cavities at the sides, and even outside the mouth of the cave.” Mr. Worthington Smith +, in a short note published in ‘ Nature’ in November last, expressed his doubt as to the glacial age of the deposits outside the Cae Gwyn Cave, and said that from an examination of the flake itself he would be inclined to refer it to the very latest of palezolithic times, and thought it might even pass for neolithic. Mr. Morton t, in the following number, questioned the value of Mr. Worthington Smith’s observations. I have received many letters on the subject, some of my friends agreeing with me upon points which I consider most essential to my interpretation, while they do not accept my conclusion as to the age of the cave-deposits. Dr. John Evans and Gen. Pitt-Rivers saw the section in September, when there was still a considerable part of the festooned margin of the swallow-hole visible. None but the first excavators saw the central plug. Mr. Tiddeman is “at one with me in considering the Cae Gwyn drift as being late in time,’ but believes it to be ‘‘ mazine glacial.” Dr. Stolterforth and Mr. Shone cannot get over the impossibility of accounting for the presence of material derived from the drift throughout the bone-earth, except on the hypothesis that the drift is older than the cave-deposits. Dr. Geikie says “ the bone-earth projects beyond the present limits of the cave, but it probably never did so originally; hence I have no doubt that the roof or wall of the cavern has given way ;” but he believes that “‘ this fall of the roof or wall of the cave took place before the deposition of the glacial deposits.” This view is obviously inconsistent with the facts to which attention is called by Dr. Stolterforth and Mr. Shone, namely, that the bone-earth and other cave-deposits are full of material derived from the marine drift. The old excavation at the upper mouth of the Cae Gwyn Cave has been reopened, and a clear section cut through the “ Head” into the undisturbed drift, in which, at a distance of some 8 feet from the * ‘The Liverpool Courier,’ Thursd. Oct. 13, 1887. t “The Ffynnon Beuno and Cae Gwyn Caves,” ‘Nature,’ Noy. 3, 1887, vol. XxKVil. p. 7. { “The Ffynnon Beuno and Cae Gwyn Caves,” ‘ Nature,’ Nov. 10, 1887, vol. Xxxvil. p. 32. ON THE CAE GWYN CAVE. 119 rock above the cave and about 7 feet below the surface of the ground, in a bed of sandy clay (see fig. 1), 17 species of shells were found, of Fig. 1.—Portion of the north-west face of the Cutting outside the upper opening to the Cae Gwyn Cave. (From a photograph by Mr. Helsby, of Denbigh.) EN \ \ KK KX Vw KS OK KK OK OK OK OK OK eS 2 2 2K ok OK OK Ok ok Ok 2K OK KF OK OK kK OK WOK OK HO ws 7 * OK x OK KK OK OK OK KK KS KOK OK OK OK OK OK Kt > 2K OK OK OK OK OK OK OK OK kk E * OK OK OK KE Bene Balaais Sp. oo ais..s.- 02 nai sake n eee CAE DoE Se RE ee RE erg * * * * * * 5 2K All these are recorded by Gwyn Jeffreys as now occurring on the coast of the British Isles, except Astarte borealis, of which only dead and, possibly, derived shells have been found. All except Pecten varius and Fissurella greca have been found in the marine drift of St. Asaph and Colwyn; and the two exceptions go for nothing, as these shells are common on our coast at the present day. There is only the Astarte borealis which is locally extinct, and it occurs in the high and low marine terraces, from Moel Tryfan to ON THE CAR GWYN CAVE. Tou Macclesfield. It has gone north, while all the other shells still live on our coast. Somewhat analogous is the occurrence of two locally extinct shells in our postglacial river-gravels. Corbicula fluminalis and Unio littoralis have gone to the Nile and Loire, while the Mammoth and Tichorhine Rhinoceros, whose remains are found in the same gravels, seem to indicate colder conditions, and the rest of the freshwater Mollusca are still found in the Cam and other rivers of the south-east of England. In deposits of such antiquity we might expect to find some locally extinct forms; but no one who compares the shells found in the drift outside Cae Gwyn Cave with those of any of the undoubted glacial deposits, such as that at Bridlington, could allow that the Cae Gwyn shells indicate glacial conditions. Some have seen on the shells in the St. Asaph Drift, outside the Cae Gwyn Cave, and elsewhere, small strive, which they refer to glacial action. I exhibit * fragments of shell, picked up on the coast of North Wales this year, which are similarly scored by the acci- dents of a gravel beach. Some are from Deganwy, some from the Menai Straits, all too far from any shell-bearing drift to have been derived from it. It has been remarked that the shells in these marine drifts, though nearly all of existing species, are thicker than those now living on our coasts. It is natural that the thicker shells and the thicker parts of shells should have the best chance of being preserved among the stones and sand of a sea-beach; but I have failed to see any difference in this respect between the shells in the marine drift of the Vale of Clwyd, or the equivalent beds elsewhere, and those found in medern deposits of the same character on our coast at the present day. In confirmation of which I exhibit* recent specimens from the coast of North Wales or further south, quite as thick as, or rather, I should say, much thicker than any of those in the marine drift. In many cases the southern varieties are characterized by their thickness and the northern by their thinness, as, for example, in the ease of Tellina balthica, of which Gwyn Jeffreys t says: ‘ Our usual form (which may be termed solidula) abounds in all the Tertiary deposits, including the boulder-clay or ‘till’ and the Mammalian Crag. It may, therefore, be regarded in the main as a northern species; but it is likewise common in many parts of the south of Europe.” The variety attenuata, in which the shell is smaller, more compressed, and of a thinner consistency, is the Baltic form. In the var. truncata of Mactra solida the shell is thicker and the teeth stronger. This form occurs ‘ South of Devon and Cornwall, Tenby, Irish coasts, Firth of Forth, Clyde district, Orkneys, and Lerwick.” Mactra solida and the variety truncata have been chiefly noticed as littoral and in southern latitudes, their furthest limit being Sicily, where the former is also fossil; the only northern locality that appears * TI.e. at the meeting of the Geological Society. t British Conchology, vol. ii. pp. 376, 377. 122 PROF. T. M‘KENNY HUGHES to be recorded is the Scandinavian coast, on the authority of O. F. Miller. The variety elliptica (“shell invariably smaller than the © typical form, broader in proportion to its length, in consequence of the sides being more produced, and of a thinner texture”) has essentially a northern range, from Iceland to Kulla in the south of Sweden *. In the table given above (p. 120) L have indicated which of the shells found in the drift outside Cae Gwyn Cave occur also in the marine drift at St. Asaph and Colwyn; which are common to the glacial beds of Bridlington collectively ; and which are found on our coasts at the present day. These shells prove conclusively that the high-level drift at Cae Gwyn is not “a true undisturbed glacial deposit,” but that it belongs to the St. Asaph Drift, which ‘“‘is mainly remanié” f. The deposit itself consists of fine sand, clay, and gravel, with boulders of various size and origin scattered through it. It is not such as would occur along a shore lashed by the wind waves. The whole of the rocky ledges and most of the fissures and caves would have been swept clean by such a sea. But it might easily have resulted from the working-down of débris from cliffs of older drift after the land had been submerged far enough to sink these erags below the action of the waves. When it was rising from the sea, in the emergence which followed, there was such a mass of drift hanging on the hill-sides that it has not yet all been washed away, and the remaining patches protect the material first thrown down. But that a cave or terraced crag not so covered can ever have been at sea-level without being swept clean is difficult to believe. The preservation of cave-deposits under land-ice drift from Snowdon and Arenig is credible ; but an examination of the deposits shows that no part of those exposed can be referred to the land-ice drift; more- over, the discovery of the shells in the drift outside this cave con- clusively proves that it was not the land-ice drift, but a marine de- posit derived from it, some having worked down the steep slope into deep water, while part was subaerially derived from it at a much later time. The mixture of north-country boulders and flint in the same deposit with those from the west is very marked and difficult of explanation ; but this locality cannot have been far from the line along which the terminal deposits of the northern and western ice met, as a little way to the west we find the glacial drift exclusively of western origin, and a short distance to the north-east we find the drift wholly made up of material from the north and east. If that be so, we may expect that some glaciated stones of northern origin may have got washed into the marine deposits of the lower part of the Vale of Clwyd without obliterating the strie; but, for some reason or another, they have not yet been found in the drift near St. Asaph ; possibly they may occur on the higher ground to the east. The deposit inside the Cae Gwyn Cave cannot be synchronous * Gwyn Jeffrey’s ‘ British Conchology,’ vol. ii. pp. 417, 418. t Hicks, Quart. Journ. Geol. Soc. vol. xliii. 1887, p. 117. ON THE CAE GWYN CAVE. 123 with the shell-bed outside it—one is terrestrial, the other is marine ; there is no ground for the hypothesis that the sea re-sorted the ter- restrial deposits. We have to inquire, therefore, whether the cave- deposits are earlier or later than the marine deposits. If earlier, then we must carry back the cave-animals through the time when glacial conditions prevailed over all this area, and refer them to the preglacial age. But I must say I cannot get over the stratigraphical difficulty that material which was not transported into that area till after the recession of the Snowdon and Arenig ice is found in the cave-earth, nor the paleontological difficulty that the group of mammals found in the cave is of the newer postglacial type, and identical with that found in other caves known to be postglacial and in postglacial river-gravels, while there is an entire absence of distinctly preglacial forms*. This argument was combated by Dr. Hickst and Pro- fessor Boyd Dawkins +t, but their objections have recently been effectually disposed of by Mr. E. T. Newton §. Another hypothesis is that the occupation of the cave should be referred to an interglacial age ; but I know of no geological evidence in North Wales of a mild interglacial age; and if we can get over the difficulties connected with this cave, without calling in theories founded on a very forced correlation of geology with astronomy, it will be better to do so. A third hypothesis, that these cave-animals lived between the glaciers and the sea in the early age of the submergence, before the sea had reached the Cae Gwyn Cave, may be true. But that would not make them preglacial, glacial, or interglacial. It is probable that the glacier-ice came down in tongues to the sea, leaving exten- sive areas along the coast fit for man and the lower animals. It is probable that man and the large mammals followed the receding ice on one hand, and the sea-shore on the other. It is possible that they may in some places have pushed on between the ice and the sea on an area afterwards submerged; but there is no proof of it, and with so much evidence in the surrounding district that man and the early associated group of animals came in after the flints and granite and other material introduced. during the submergence, it does seem desirable to get much clearer evidence than any yet obtained from the Cae Gwyn Cave, that being the only case, before we admit that man was there before the submergence. A northern mountain region which rose the highest and sank the lowest, where the ice gathered soonest and lingered longest, is not the place where we are likely to find the earliest traces of man. These two points, then, I consider perfectly well established :— 1. That the drift on the flank of the hill near Cae Gwyn must be referred to the same division of the St. Asaph beds; and 2. That it was deposited not only after the climax of the glacial * Quart. Journ. Geol. Soe. vol. xliii. p. 110. © fords. LNT. t Ibid. p. 118. § Geol. Mag. 1887, dec. 3, vol. iv. p. 94. 124 PROF. T. M‘KENNY HUGHES age, but after glacial conditions had entirely passed away in the Vale of Clwyd—that, in fact, the deposit is postglacial. It was obvious that if the deposits in and outside the cave were of direct glacial origin, the rock-face which had been so rapidly and quietly covered that the fine earth and bones had not been swept away might be expected to show marks of glaciation ; and the wish being tather to the thought, it was stated that the rock was rounded and smoothed by ice from the north. On the contrary, however, veins and less soluble sparry portions of the rock stood out in lines and bands all over the rock in a manner never seen on any ice- worn rock. On the occasion of reading my former paper I exhibited specimens of the rock illustrating this point. Fig. 2.— View of upper opening into Cae Gwyn Cave, looking north- east. (From a water-colour sketch by Mrs. M‘Kenny Hughes.) The point of view is indicated by the arrow 7 on the ground-plan, fig. 8. (p. 135). The left-hand figure is represented looking into the cave towards the entrance. Behind him, in the direction of the handle of the pick, is the continuation of the cave not yet explored. There was sufficient evidence also that the rock did not owe its ON THE CAE GWYN CAVE. 125 present surface to the sea. Ledges and points that a man could stand on projected straight out from the rock-face just where the waves and pebbles would have hammered them all away. The character of the rock is well shown in the sketches and photograph (see figs. 2,3, and 4). Funnel-shaped cavities (as seen in fig. 2 Fig. 3.— View of the upper opening into Cae Gwyn Cave, looking north. (From a water-colour sketch by Mrs. M‘Kenny Hughes.) ISSN above the left elbow of the man in the centre), tapering down or opening out both ways like an hour-glass, told of swallow-holes under a land-surface, rather than blowholes from a sea-cave. The fretted surface of the rock, the unctuous clay lining the holes and fissures, the travertine plastering the walls of the cave and filling the cracks, the lines of sand in the crevices, all pointed to chemical decomposition and subterranean denudation only. As the result of such operations, it necessarily happened that some of the drift had moved downwards without much change, except the destruction by percolating water of any shells or frag- 126 PROF. T. MSKENNY HUGHES ments of limestone that might happen to have been in it. No distinction had been drawn between this marine drift (itself remanié from older glacial deposits) and the modified or even re-sorted upper part of this marine drift. Fig. 4.—Lower left-hand corner of Section seen in fig. 3, looking north-north-west. (From a photograph by Mr. Helsby.) a. Bedded sand belonging to marine drift which has sunk in towards the swallow-hole. b. Angular and weathered fragments of limestone from the broken-down wall and roof of the cave. c. Loam, in places standing vertical from the settlement of the mass. d. Large block of limestone (shown also in figs. 2 and 3), which barred further progress into the northerly extension of the cave. With the strong suspicion thatI had in my mind of the unsatis- factory character of the evidence that the cave-deposits were earlier than even the submergence, this was, I thought, a point of some importance, seeing that, in the first place, it bore upon the ques- tion as to whether the beds had been correctly identified ; secondly, because the removal of many feet of superficial deposit would leave the rock nearer the surface; and thirdly, because the character and ON THE CAE GWYN CAVE. 127 distribution of the surface-deposits might help us to form a judg- ment as to the position of any swallow-holes or lines of soakage into the cave. In this I was not mistaken, and the importance of the question was at once recognized by those who differed from me in the interpretation of the section. To fix a point where I considered that the re-sorted surface of the marine drift (itself remani¢) attained an appreciable thickness, I pointed out an old hedge against which the head or run of the hill had been caught. Of the existence of this old fence I might adduce other evidence, if the photographs I exhibited were not sufficient, as it was removed and a portion of the bank levelled by the present owner less than 10 years ago. It is within 16 feet of the upper opening into the cave, and runs much nearer to the rock in which the cave occurs. The last exca- vations cut across this bank, and have shown a depth of 6 feet of surface-soil here. This deposit rises to the N.E. and thickens out again at the north-east end of the pit, as indicated in fig. 5, which Fig. 5. The left-hand portion represents the section seen along the north-west face of the cutting in September 1887, and shows the festooning of the upper part of the superficial deposits at the margin of the swallow-hole. The portion included within the asterisks is that shown in the photograph, fig. 1. The right- hand portion is the section along the north-east face as exposed by the excavations carried on in October following. (Scale 20 ft. to 1 inch.) 8. 30° W. N. 30° E.N.W. S.E a. Head, Rainwash, Run-of-the-Hill. 6. Moved drift; marginal portion of that which slipped into swallow-hole, and finally closed the upper opening. ec. Cave-deposits. d. Angular limestone ; broken-down wall and roof of cave. e. Marine drift. J. Shell-bed in drift. g. Limestone. shows the section as seen by General Pitt-Rivers and Dr. John Evans in September. This face was afterwards cut back a little, but still, in October, the section given from a photograph (fig. 1) shows the margin of the looped drift cutting off the shell-bed and the surface-soil falling with it in towards the swallow-hole. The 12& PROF. T. MSKENNY HUGHES section facing the observer, looking a little east of north along the © length of the pit, showed this surface-soil about 4 feet deep, moved drift 4 feet deep, red clay a few inches; this red clay was very irregular and consisted chiefly of the earthy residuum of the decom- posed limestone, corresponding to some of the clay with flints of the Chalk districts. The surface-soil and moved drift thinned off against the rock a little further east, as shown in the diagram, fig. 6. The Fig. 6.—Diagram-section, showing the looping-down of the deposits into the swallow-hole before the Section was cut back as far as represented in fig. 5. Index as in fig. 5. (Scale about 11 ft. to 1 inch.) core of the principal swallow-hole has, of course, long gone; it was where the earth fell in in the winter of 1886 (see fig. 6), just over where, according to my view, the water soaked first through the jointed, fissured, and funnelled rock into the cave, and afterwards through the great angular masses of limestone derived from the breaking down of the wall and roof of the cave. Some of the super- ficial deposit was of so late a date that the marks of plough and harrow were found on the included stones. I produced specimens so scored, and the evidence seemed satisfactory, as I thought, to the Fellows of the Society; but these specimens were claimed by Dr. Hicks as stones marked by the picks of the excavators. I now exhibit, as further evidence upon this point, an artificially perforated stone found in the surface-soil from the part of the section above referred to, which is scored all over by similar accidental marks of agricultural implements. ; The cave had been filled in the usual way with material from superficial deposits washed in through openings, or from the decay of the rock, or carried in by beasts. The sand that occurred all along it was such as would be derived from the running sand of the drift outside, which was still being carried in in wet weather ON THE CAE GWYN CAVE. 129 even during the recent excavations. Under these circumstances there was no wonder that the cave-deposits so nearly resembled the drift as to be considered by some a continuation of the marine beds. There was no difficulty in accounting for the character of the contents of the cave on the hypothesis that the drift already covered a great part of the surface of the rock while the cave was being filled. But on the supposition that the drift sealed the mouth of a filled-up cave, how can we explain the occurrence in the cave of material which must have been derived from that drift, such as the flints which occurred in the lowest bone-earth ? Some account for this by supposing that the sea broke up stalag- mitic floors and mixed up preexisting cave-deposits with drifted sand and Bonlder-clay ; but there was no trace of such action in the cave. The principal masses of travertine were in the line of the most recent drainage to the north, where the water disappears now. This continuation of the cave is indicated by the dark shades in the lower right hand of fig. 4, and the lower left hand of figs. 2 and 3. There were no sea-shells in the cave. Curiously, we did not happen to find even one carried in through the swallow-holes. It may be that all the shells perished in that process. But had they been deposited fresh by the sea in the bone-earth, they would have been preserved. ‘The material was not arranged as it usually is in sea-caves, tossed up into sloping banks of shingle; it was an ordinary cave-deposit, and all the phenomena could be simply explained by reference to what are known to be the common pro- cesses of subterranean denudation. It has been frequently stated that the sands of the drift outside the cave passed uninterruptedly into the cave. I saw the material that closed the opening before anything was known as to the nature of the drift immediately beyond. I saw in it no such sand, except the recently scraped sand on the very top of the cave-deposits along the rabbit-burrows. I prodded vertically upwards into clay, oppo- site to where sand occurred in the section outside. Itis quite clear that sand would not have stood in such a position. The next thing that happened was that a plug of clayey sludge descended into the cave and cut off all further observations for some time. Yet, on the occasion of my last visit to the cave, the continuity of the sand with the upper beds in the cave was again asserted. I asked how that opinion could be reconciled with the admitted fact of the settlement of the plug of clay before we had got through the cave into the drift outside, but could get no satisfactory answer. ‘The fact is that the material inside the cave did much resemble the drift outside, but that was simply because it was derived from it by swallow-hole action, and is an argument in favour of the view that the drift must have been outside during the whole of the time of the accumulation of the deposits in the caves, and not that the marine-drift sealed up the mouth of a previously filled cave. The section in the Brit. Assoc. Rep. 1886, p. 219, is not a section seen at the opening of the cave, but of what was seen after the actual mouth had been cleared. It is a section of the drift which MvG.8. No. 173. K 130 PROF. 1. MSKENNY HUGHES abutted against the rock south of the opening, but was never seen running continuously into the cave as there drawn. No direct continuity between the deposits in the cave and the several beds of drift outside can have been observed. The bone- earth and other cave-deposits and the overlying great angular fragments of limestone were, of course, traced for some feet in front of what was supposed to be the upper entrance of the cave, but these were afterwards found to extend only as far as the cave itself was proved to have originally extended. The upper beds were cut off by the mass of clayey drift (see fig. 6) which was looped down over the upper opening, and fell in soon after the backing of cave- deposits had been removed during the excavations. ‘The rock rose to the surface within a short distance above the cave, and the chief percolation of water was through the re-sorted surface material down to the rock, and then along the face of the rock and through fissures in connexion with the cave. The prin- cipal line of drainage was, in later times, at any rate, outward to the north from the upper opening of the cave. As stated above, the water now disappears into a large hole in the lower left-hand corner of the cave, as shown in the sketches (figs. 2, 3, and 4). This hole was proved, by thrusting in a stick to a distance of nearly 6 feet, still in limestone; but even in June of this droughty year, the cave just within the upper opening was so wet that visitors were advised not to attempt to walk through it. And there is a fall of about two feet to the other and original entrance. Thus it appears that the cave sloped both ways from this swallow-hole. The occurrence in the cave-deposits of material which must have been derived from the marine drift, such as the flints and granites, proves that the drift is older than the cave-deposits, except on the untenable hypothesis that the cave-deposits were marine, or re-sorted by the sea that broke up stalagmitic floors, dashed great boulders about, but did not sweep away beds of cave-earth full of bones. So we must turn elsewhere, and either find along the coast con- ditions in which the sea washes terraced crags without removing the subaerial débris from them, or find some operations of nature tending to modify caves and their contents in such a manner as will explain the difficulties in Cae Gwyn. The estuary of the Conway offers the most nearly similar con-- ditions to those which must have prevailed in the estuary of the Clwyd during the submergence: if we could imagine the whole of the vale of Clwyd submerged to a depth of some 400 feet; cliffs of ancient drift being wasted in one place, and the solid rock touched in another; here banks thrown up which divert the currents, and clay and sand and gravelalternating. Fragmentary shells in exactly the same condition, the same part preserved, and most of them of the very same species as those in the Vale of Clwyd, occur in the shore-deposits of Deganwy. But wander on to where the sea rises and falls across the terraced rock, and stand there while the waves are moved by even such a breeze as would just let you sail a boat, and judge whether any loose subaerial deposit could remain. An- ON THE CAE GWYN CAVE, 131 gular talus in submerged corners, especially where covered by clay drift, has often long withstood the wind and waves, as for instance on the coast west of Llandulas Station, but that such a thing as the few feet or inches of broken rock and interstitial débris outside Cae Gwyn Cave could survive the passage of those waves 1s incon- ceivable, . A good deal of the force of the arguments here put forward depends upon the establishment of the existence of swallow-holes above the cave. ‘This is proved by the opened fissures and vertical cylindrical holes in the limestone. They communicated with the porous re-sorted drift above, and were now open, now choked with drift, or plugged by a boulder. They were filled, according to their size and position in the rock-drainage system, with coarser or finer material. The red clayey residuum of the decomposed limestone formed an important part until the opening was enlarged to allow of a free current of water carrying in material from the drift. Down in the cave the action of streams was seen in the curious manner in which bones and teeth were jammed into nearly hori- zontal fissures where they stuck, as coarse material gets caught ina sieve. Near the bottom of the last explored part of the cave, a little to the right of the pick shown in fig. 3, about 20 feet from the surface, where the drainage was outward to the north, a land-shell, Hyalina (Zonites), was found in the clayey earth close to the wall of the cave, just as we find them in fissured limestone everywhere. In other caves in this district we see clearly how the drift is carried down through swallow-holes, and arranged in the wider spaces in the cavernous rock below. On the opposite side of the valley, in the little quarry behind the cottage, there are very good examples of this. Here it will be seen that sometimes washings from the drift (fig. 7, from a photograph by Mr. Helsby), and some- times apparently masses of drift, as seen on the extreme left of the same figure, have worked down into the openings as they were from time to time enlarged by the. chemical action of the acidulated water upon the limestone. That, from the nature of the case, this sort of thing must happen is obvious, but here we can sce evidence that it has taken place in the dragging down of the infilling deposit along the walls of rock. So that the clay is pulled out, shckensided, and has, when dry, almost a cleaved look, and the flat and elongated stones are arranged with their longer axes parallel to the direction of movement (fig. 7). The surface of the limestone shows the usual fretted appearance quite different from the surface of a sea-worn limestone. When large masses get detached by this chemical weathering along the joints, and one cave breaks into another, or the mouth of a cave breaks down, or when the drainage leads into broken rock, the same process goes on among and around the great angular fragments, so that there is a kind of extension of the cave and cave-deposits into the talus. This is precisely what has taken place in the Cae Gwyn Cave, where the cave-earth penetrates also the mass of angular blocks 132 PROF. T. MSKENNY HUGHES which occur in the cave where the roof has fallen, and outside where the wall or mouth of the cave has broken down. Fig. 7.—Section in quarry behind cottage by road on hill-side south of, and opposite to F'fynnon Beuno Cave. (From a photograph by Mr. Helsby.) Here masses of drift washed down into the fissured and decomposing rock were exposed in cavities in the progress of quarrying; some of this drift was relaid horizontally, as shown behind the standing figure, while some was dragged down by its own weight, and, in places, stood vertical, as shown in the cavity on the right of the picture. | Recent excavations have conclusively proved that the upper opening now seen did not exist as an entrance to the cave during the period of its occupation, although many fissures and cylindrical holes, sometimes open sometimes choked, lead from the surface of the rock and the water-carrying strata of the overlying drift into this part of the cave. When the bone-earth was followed out from the upper opening it was found tv be overlain by a mass of broken limestone, which the floor of solid rock rose to meet, at a distance of some 6 feet more or less from the inner wall of the cave (see fig. 6). This mass of angular rock sloped in over the cave-deposits, as shown in fig. 4; and when followed to the north end of the excavation in front of the opening, it was seen to extend from the floor of the cave to meet the rock above, which again projected forward (as seen in figs. 2 and 3) to form a roof to the cave. Broken rock extended in a similar manner in front of the opening up to the exterior wall of the cave at the south end of the excavation, and immediately in front of the cave great masses of rock were found in the soil and drift that blocks the opening (as seen in figs. 2, 3, 4, and 6). It was perfectly clear that these masses of rock represented the roof and walls of a portion of ON THE CAE GWYN CAVE, 133 the cave which had yielded to subterranean denudation and gradu- ally crumbled down or collapsed more rapidly. Dr. Geikie, who visited the cave in October, quite concurred in this view (see #118). : So the bone-earth which was said to occur 4 feet beyond the entrance to the cave was really all within the original cave before this portion of it had fallen in. It was impossible that this could be an ancient mouth of a cave round which talus from the rock above had accumulated, and that the sea had afterwards crept over it and deposited the marine drift upon it, because the great angular blocks occurred at various levels in the clayey and sandy débris, and the drift was crushed in upon some of the fallen masses so as to stand vertically, with the included fragments arranged as described above in the case of the drift in the quarry on the other side of the gallery, where also it has sunk into fissures and caves of the limestone. The same thing has happened here also in the case of the Cae Gwyn Cave (as shown in figs. 2 and 4). The pebbles stood with their longer axes vertical, and the bed of grey clay was even a little reversed in places. The inclination of the beds decreased through about 4 feet of angular limestone and overlying sand and loam till the drift by degrees resumed its almost horizontal position. In the lower right-hand corner of the sketch, fig. 2, close to the right foot of the right-hand man, the flake was found ; it was under some overhanging rock, which had to be removed in the progress of the work, and was overlain by great masses of limestone. The deposit in which it occurred was a slightly sandy, red, sticky clay, like the earthy residuum of the limestone, with a little more sandy material washed in from the drift, and resembling rather the mate- rial that: filled the fissures than the stratified cave-deposits. This satisfactorily explains some difficulties connected with the flake; for instance, the curious fact that, although many flints were found in the bone-earth, their surface was in a very different state from that of the flake. It also explains the position of the flake, which was tucked into a corner far inside the recesses of the cave, instead of, as is mostly the case, somewhere near the entrance ; for it has been shown that this upper opening was not an entrance during the period of occupation of the cave. The flake is considered by Dr. John Evans * and Mr. Worthington Smith + to be of a late paleolithic type, if not newer still, and if it did occur in the true bone-earth it would go far to prove that the bone-earth is postglacial, whereas if it did not occur in the true cave-deposits (as distinguished from the swallow-hole importations) all evidence of the existence of man in this cave falls to the ground. It is more probable that the flake was carried in much later times into the position in which it was found. The Zonites had reached a still lower level, where it lay, not far off, in clay identical with that * Quart. Journ. Geol. Soe. vol. xlii. p. 11. + ‘Nature,’ vol. xxxvii. Nov. 3, 1887, p. 7. 134 PROF. T. M‘KENNY HUGHES in which the flake was found. The bones and teeth caught in the ~ fissure were only about 6 feet from where the flake lay. The overlying drifts and surface-wash were festooned over the broken opening to the cave. The core of the swallow-hole was, of course, the portion that sunk in in the winter of 1886. The looping of the beds decreased as the face of the drift was from time to time cut back; but it extended for a considerable distance, and the outside portion of the festooned beds (as shown in fig. 5) was seen by General Pitt-Rivers and Dr. John Evans in the first week in September of this year (1887). The margin of it was still to be seen in October, when the photographs exhibited were taken. See especially fig. 1, in which a indicates the shell-bed, cut off, it will be noticed, by the brown clay which slopes down towards the opening to the cave in the direction of the flat stone seen opposite the 0. When, on digging through the cave from the lower entrance, this broken place in the side of the cave was reached, it appeared as if the bone-earth extended several feet beyond what seemed to be another entrance to the cave. It was not at first an objection to this view that many cartloads of large angular masses of limestone had to be removed before the bone-earth was touched, as such angular débris, owing to the falling of masses from the roof, often occurs in such caves in and on the bone-earth, and it was to be expected that a larger quantity would be found around the mouth. But when it became clear that the cave went on, and that this mass outside the opening lay in the line of and represented the wall and roof of a portion of the cave that had fallen in, then it was evident that the bone-earth extended no further than the original cave ; and we soon ascertained that the bones were entirely confined to the beds within and under the angular blocks that represented the original outer wall of the cave. No marine deposits were found inside of it, and no cave-deposits outside of it. The broken limestone over the bone-earth contained a few foreign fragments, but they were only such as would naturally work in from the drift. If the overhanging rock were to fallin now, it would contain some such boulders, one of which is seen plugging the cylindrical hole which descends through the limestone immediately over the opening. (See fig. 2, above the elbow uf the man in the centre of the sketch.) The drift lay upon this angular débris. A priori it seemed im- probable that the sea could have been there and spared the soft cave- deposits and incoherent débris outside. This, however, was all cleared up by our finding loam standing vertically against the blocks which had fallen in, and showing that the drift, which was there before the breakdown of the roof and wall of the cave, had sunk in upon the crumbling and decomposing limestone. That the effect of this falling-in was not more marked was probably due to the fact that the cave was by that time nearly filled, and the dis- placement therefore was not so great as it would have been had the cave been empty. Still, the drag along the margin showed evidence ON THE CAE GWYN CAYE. 135 of a very considerable settlement, probably not less than 4 feet, in the section shown in the lower left-hand corner of figs. 2 and 3. Instead, therefore, of the less satisfactory task of proving that there were in the district many well-known processes connected with subterranean denudation which might explain the superposition of the marine drift upon the bone-earth, each of which had played a part in producing the results observed, we have now the clearest evidence as to the exact manner in which it has all been brought about, namely :— That the marine drift was deposited before the occupation of the cave by the animals whose remains have been found in it ; That at the time of the occupation of the cave the upper opening Fig. 8.—Plan of Cae Gwyn Cave. (Scale 34 feet to 1 inch.) Entrance to cave. Break in the side of cave known as “‘ Upper Opening,” where the bones &c., were found outside the then existing cave. ec. Cutting made after discovery of the upper opening 0. d. Débris of roof and wall of cave overlying bone-earth. e. Extension of cave to the north along which water now drains away under the drift. f indicates the point of view in fig. 2. =S (b, fig. 8) now seen did not exist, but the animals got in by the other entrance (a, fig. 8); 136 PROF. T. MSKENNY HUGHES That against the wall of the cave, where it approached nearest to | the face of the cliff, the drift lay thick, as we now see it close by. That by swallow-hole action the cave was first partially filled, and then the thinnest portion of its wall gave way gradually, bury- ing the bone-earth below it, and letting down some of the drift and newer superficial deposits above it, so that some of it now looks as if it might have been laid down by the sea upon pre-existing cave- deposits. Discussion. The PresIDENT regretted the absence of several who were well qualified to speak on this question. Dr. Hicks said the Author had acknowledged that he was thoroughly biassed against the views of the other members of the Committee when he began to criticize them. Prof. Hughes had uot been present during the most important stages of the explorations. Dr. Hicks protested strongly against the arguments of the Author, and complained that the subject was treated by him quite differently from last year, when he insisted that the whole of the drift in front of the entrance was remanié, that it contained no shells, that 1t was quite unlike the drifts in the valley, showed no evidence of sea-sorting, and resembled only rain-wash. Now that bands of marine shells had been found, Prof. Hughes was obliged to admit that it is a true marine drift, and correlate it with the St. Asaph drifts. Dr. Hicks exhibited photographs and diagrams in explanation of the points at issue, and said it was quite impossible for the enormous amount of deposit which they had removed from the cavern to have been carried in through a swallow-hole which had left no evidence whatever of its existence. Mr. Luxmoore had also shown to Prof. Hughes, in the cavern near the entrance, and before it was known that they were approaching the entrance, sands and gravels similar to those in the section in a stratified condition overlying the laminated clay and bone-earth. There was also a most distinct and undisturbed section to be seen all round the pit when it was first dug out, and when it was only five feet across at the bottom, as could be testi- fied by several witnesses. He stated that he had explained to Prof. Hughes that the land-shell was found at a spot which had been disturbed last year, and where fallen material had been thrown in. He distinctly denied that the looping down of the surface-deposits was to be seen when the section was first exposed, and regretted he had been absent when this appearance, an entirely recent change, was indicated to Dr. Evans and General Pitt-Rivers. It would not do to rely upon a drift section after a heavy shower. The bone-earth had been proved to pass under the drift section at all the points examined. Dr. Geikie, who had been asked to give his opinion on the section, found himself obliged to dissent from the Author’s views, and Dr. Hicks believed that Dr. Geikie’s views, as stated in his report to Prof. Hughes and himself, were the correct ones. The disturbance near the large block of limestone, which is imbedded in the sandy clay with bones, proved to be of no conse- ON THE CAE GWYN CAVE. LST quence, and it does not affect any of the beds immediately above. The bone-earth had been disturbed by marine action, and therefore contained irregular bands of gravel and sand and some foreign materials. Mr. De Rance had made a further exploration, in con- junction with Mr. Morgan, the owner, and one of the members of the Committee, with the result that bones of hyzna had been found overlying the block, under layers of sand which passed from the vertical drift-section well beyond the point where any pothole could possibly have occurred, and under the shelving rock to the inner wall of the cavern. His diagrams were exhibited. The whole evidence, therefore, is most distinctly opposed to Prof. Hughes’s views, and confirmatory of the statements made by those members of the Committee who have superintended the explora- tions. Mr. E. T. Newton spoke in explanation of a diagram which he exhibited in illustration of the subject. On comparing the list of Mammalia found in the cave with (1) those of the forest-bed taken as a type of a preglacial fauna, and (2) those of the presumably postglacial or interglacial fauna of the river-gravels, he concluded that the Mammalia of the cave are of the same age as those of the river-gravels. Mr. Lypexxer criticised the lists and inferences of the last speaker. The AvrHor emphasized the points which had been made by Mr. Newton. The age of the cave-deposits could only be decided by that of the deposit which finally closed it. It was certainly singular that Dr. Hicks had put everything there for him to find— the scratched stone, the land-shell, and even the old fence itself. When the cave was filled up, the swallow-hole action to which he referred was no longer in operation. Of course, there was no difficulty about the sand and gravel in the cave; that had been derived from the material outside. A plumb-line might have been let fall where the bones were found, but the original roof of the cave extended beyond them. The looped surface-deposits spoken of were part of the great slip, and he claimed that this was due to swallow-hole action. The barrier of limestone was not: paralleled in any portion of the drift; the chief mass of travertine is not floor- travertine, but wall-travertine, such as may now be seen in the cave. Dr. Geikie had allowed that the bone-earth projected beyond the present limit of the cave, but thought it probably never did so originally. Hence he had no doubt that the roof or wall of the cavern has given way, but believed that this fall took place before the deposition of the glacial deposits. To these remarks the Author would reply, that in the bone-earth, below the angular limestone, were flints and other material which only came into the district with the marine drift. Therefore the marine drift cannot have been deposited after the break-down of the wall and roof of the cave. Q@.J.G 8. No. 174. L 138 MR. A. 8. WOODWARD ON TWO GANOIDS FROM EARLY MESOZOIC 12. On two New Lerrotorp Ganorws from the Harty Mesozoic Deposits of OrancE Free Starz, Sour Arrica. By A. Sure Woopwarp, Esq., F.G.8., F.Z.8., of the British Museum (Natural History). (Read January 25, 1888.) [Prats VI.| Tux fine series of South-African fossils brought to the British Museum in 1883 by Dr. Hugh Exton, F.G.8., Curator of the Bloem- fontein Museum, Orange Free State, has already furnished two im- portant novel types of Vertebrata, made known at the meetings of this Society by Professor Sir Richard Owen*. There still remain, however, other interesting forms, adding to our knowledge of the paleontology of the early Mesozoic strata whence they were derived, and among these are some beautifully preserved examples of a Lepi- dotoid Ganoid fish. Two specimens of another new Ganoid have also been lately received from the same source, and the affinities of these types have so important a bearing upon the question of the age of the Stormberg Beds of South Africa, that it seems advisable to place on record their discovery and to offer a detailed description of their characters. J. SEMIONOTUS CAPENSIS, sp. nov.T (Pl. VI. figs. 1-5.) The first series of the fossil fishes In question comprises portions of four individuals displayed upon the surface of a slab of sandstone, mainly in counterpart. Each of these shows more or less of the scaly trunk; and, in addition, one example exhibits the head, pectoral fin, and dorsal fin; another, the dorsal and caudal fins; a third, a nearly complete tail and the anal fin; while the fourth is almost perfect behind a point a little in advance of the pelvic fins. There are thus materials for determining all the more salient features of the fish, as illustrated in the accompanying figures. In general outline the body is elongated and fusiform, the greatest depth being contained about three and a half times in the total length, and the head occupies about one fourth of the whole. Both the paired and median fins are well developed, the pelvic pair being situated a little in advance of the opposing dorsal; and all are cha- racterized by the enormous proportions of the anterior fulera. The trunk is covered with rhomboidal scales of moderate size, and these exhibit neither ornament nor marginal serrations. Head and Opercular Fold——The only specimen retaining the head and opercular bones (fig. 2) is much crushed, but the outlines of some of the elements are distinguishable, and, fortunately, these can be studied in counterpart. Viewed from the side, the roof of the skull is seen to slope rapidly downwards from a position somewhat in advance of the parieto-frontal suture, and the snout was evidently acutely pointed. The parietals( par) and frontals (fr) have been so displaced as to exhibit their shape and proportions, * Tritylodon longevus, Owen, Quart. Journ. Geol. Soc. vol. xl. (1884), p. 146, pl. vi. and Rhytidosteus capensis, Owen, ibid. p. 333, pls. xvi., xvii. + This fish has already been quoted under the MS. name of Extonichthys, Owen (J. Prestwich, ‘Stratigr. Geol.’ 1888, p. 18). DEPOSITS OF ORANGE FREE STATE, SOUTH AFRICA. 139 and the former have about half the length of the latter; the parie- tals are united by an undulating median suture, and vary little in width, but the frontals appear to taper considerably in front, and their middle sutural line is almost straight. Behind these elements one of the supratemporal bones (st) is apparently recognizable ; but in advance of the frontals nothing beyond crushed bone-fragments can be seen, with the remains of a terminal conical tooth. Of the palato-pterygoid arcade there is an undeterminable fragment ; and pertaining either to this or to the maxilla is a broken series of powerful, hollow, conical teeth. A portion of the mandible (¢) is also observed, bearing traces of a similar dentition. The operculum (0/) is of the form of a parallelogram, about once and a half as deep as broad; and the suboperculum (s.op), which must have been scarcely half as large as the operculum, shows the upwardly directed process of its antero-superior angle, so cha- racteristic of the genus Lepidotus. In front of these bones there are obscure remains of the preoperculum (p.op), and immediately anterior to this is a large superficial plate (a), situated between it and the remains of the circumorbital ring. No traces of ornamentation are visible, either on these elements or on the skull, unless a tubercle upon one of the frontal bones is an indication of this character. Vertebral Column.—Nothing can be seen of the internal skeleton of the trunk, with the exception of four of the hindermost hemapo- physes of the vertebral column, which are widened distally for the support of the caudal fin, There are no certain traces of ossified ribs, though the fossils can hardly be regarded as sufficient to de- monstrate the absence of these structures. Appendicular Skeleton.—In the pectoral arch the clavicle (fig. 2, cl) is well shown, of the ordinary Lepidotoid type; and situated posteriorly to the lower extremity of this is a small element (co.), which may probably be interpreted as coracoid. The pectoral fin consists of about 11 or 12 robust rays, which—as in all the other fins except the caudal—are unarticulated for a considerable distance proximally, though closely jointed nearer their extremities. The anterior fulcra are destroyed, but they would probably be of enor- mous size, like those of the other fins, this great development of the fulcral scales being one of the most characteristic features of the fish. The pelvic fins appear to have each comprised not more than six rays, and these, as already stated, are placed slightly in advance of the commencement of the opposing dorsal. In the dorsal fin the series of very large fulcra is sueceeded by at least 11 widely spaced rays, of which the anterior two are more closely approximated than the remainder. The anal fin shows a very strong interspinous bone supporting the fulcra, and there are eight rays rapidly shortening behind. ‘The atrophied upper lobe of the tail is fringed above with fulcral scales, which diminish as they extend upon the caudal fin; and there are also well-developed fulera upon the inferior margin of the latter. This fin is symmetrical and not forked, and the rays, in number about 14, are strong and closely articulated from near the base, dichotomously branching distally. Scales.—The scales are strong and enamelled, varying in form in L2 140 MR. A. 8S. WOODWARD ON TWO GANOIDS FROM EARLY MESOZOIC different parts of the body in the usual manner; those of the middle of the flank (fig. 4) are deeper than broad, gradually becoming rela- tively less deep dorsally and ventrally (fig. 5), and passing behind into the smaller rhomboidal lozenge-shaped scales of the caudal pedicle. The posterior border is not in any case denticulated. There is a slight median rib on the inner side of each scale, and on the more anterior portion of the flank the ordinary peg-and-socket articulation is observable. The “lateral line” is well marked, and is very slightly arched upwards. Systematic Determination.—On consideration of the foregoing ana- tomical details, it at once becomes evident that the South-African fish is an ally of the widely distributed Mesozoic genera Lepidotus and Semionotus, if, indeed, it does not belong to one of the two. The structure of the skull is essentially similar, and likewise the form and proportions of the trunk and fins. The size of the fin- fulcra is no greater than that of the fulcra met with in certain species of Lepidotus (e.g. L. minor, Ag.); but the head in the pre- sent fossil is sufficiently well preserved to show that the dentition was quite distinct from that of the last-named genus, and the scales also evidently differ in the form of the overlapped margin. From Semionotus, however, no point of divergence of generic value is ap- parently discoverable ; and the American species referred by Egerton to Ischypterus* (in allusion to the dimensions of their fin-fulera) seem to connect precisely the earlier recognized forms of the genus with the new type here made known. The South-African fossil has still larger fulcra even than the latter, and this character especially serves to distinguish it from all the species hitherto defined. It may therefore be appropriately termed Semionotus capensis, as being the first recorded example of this European and American early Mesozoic genus occurring in the region of the Cape. Formation and Locality—Stormberg Beds (Upper Karoo Series) ; the Drakensberg Range, Orange Free State, South Africa 7. * Sir Philip Egerton, quoted by Sir Charies Lyell, Quart. Journ. Geol. Soe. vol. iii. (1847), p. 277. As shown by Dr. Traquair’s description (Quart. Journ. Geol. Soc. vol. xxxiii. 1877, p. 559), Jschypterus presents no certain points of difference from the typical species of Semzonotus which can be regarded as of generic value. The fin-fulera are certainly larger than those of most forms referred to the last-named genus; but there are gradations between the ex- tremes, and there appears to be an equal variation in the development of the fulcra in the different species of the closely allied genus Lepidotus. + These particulars have been kindly furnished by Prof. T. Rupert Jones, E.RB.S., F.G.S., to whom I am indebted for the following information from the ‘Bloemfontein Gazette’ of July 5th, 1888, relating to the precise locality from which the specimens of this fish were obtained. The fossiliferous bed occurs in a precipice upon the farm of M. H. K. van der Merwe. about three-and-a-half hours’ march from Senekal, in the direction of Ficksburg. The precipice is hollowed at the base by caves and rock-shelters, and the natives, who at present use these as store-houses for their corn-baskets, first observed the fossil impres- sions, pointing them out to the neighbouring farmers. “The late Mr. Stow chiselled and split the portions of rock into fragments. and it seems probable all available specimens have been removed till another slip of rock takes place.” In his ‘ Report of the Geol. Survey of the Orange Free State,’ 1879, p. 48, Mr. Stow remarks that “the fish are evidently new to science, but of an old- world type, the scales being arranged in regular diagonal lines.” The rocks at the base of the precipice at Weltevredren are described by the same geologist DEPOSITS OF ORANGE FREE STATE, SOUTH AFRICA, 141 II. Crerrarotepis Extont, sp. nov. (Pl. VI. figs. 6 & 7.) The latest specimens received from Dr. Exton are two imperfect examples of a deep-bodied Ganoid fish from Rouxville, Orange Free State. The larger specimen (fig. 6) is destitute of most of the head and caudal fin, while the smaller exhibits only a portion of the trunk, with the operculum and postorbital bones, and the pectoral fin. The general proportions of the fish are well shown in the figure just quoted. The head is relatively small; pelvic fins are present ; the anal and dorsal fins are similar and opposite; and the upper lobe of the caudal pedicle is atrophied. Head and Opercular Fold,—An undeterminable fragment of the roof-bones is the only portion of the cranium exposed to view, and the more superficial circumorbital elements are in such a state of preservation that the sutures can only be indistinctly recognized (fig. 7). There is also some appearance of a chain of three small membrane bones extending backwards from the postero-superior angle of the circumorbitals, above the operculum, and between it and the cranial roof, and these, as in Polypterus and some other Ganoids, are perforated by the “ lateral line” as it passes upon the head. The fossil (fig. 7) shows the sensory canals very clearly ; from the second of the three ossicles, one branch is directed upwards across the occiput, while further forwards the line divaricates, one division passing over the orbit and the other downwards. There are also other portions of the “lateral line” system beyond the occipital region, the precise connexions of which are not shown. No preoperculum or interoperculum is recognizable, but the oper- culum and suboperculum are shown in both the specimens. The operculum (op) is almost square, with the postero-superior angle rounded off, and it is considerably smaller than the suboperculum (s.op), having only about two thirds the vertical extent of the latter. In the large fossil (fig. 6) there are likewise faint impres- sions of two or three short and broad branchiostegal rays beneath the suboperculum ; and all these bones, as well as those of the head, exhibit a superficial ornament of sparsely scattered ganoine tubercles, Appendicular Skeleton Of the paired fins the pectorals are placed laterally, being situated in a position almost on the level of the lower border of the suboperculum. So far as can be ascertained from the smaller fossil (fig. 7), each fin seems to have consisted of about 10 delicate rays, ornamented externally with tubercles, but the state of preservation is too imperfect to allow of determining any more precise structural features. The pelvic fins are even more indistinctly shown, though the large specimen (fig. 6) indicates that these were very small, and placed almost midway between the head and the commencement of the anal. Of the median fins, both the dorsal and anal are nearly complete. The former consists of about 18 stout rays, each articulated, at mo- derate distances, beyond a point near the base, and dividing dis- tally ; and in front of the fin there are some indistinct small fulcra. (Joc. cit.) as consisting of ‘‘a belt of ribbon sandstone, some parts of which, when worked down, show a beautiful ribbon-pattern of varying colours—red, white, yellow, and light buff.” 142 MR. A. S. WOODWARD ON TWO GANOIDS FROM EARLY MESOZOIC The first eight rays are placed close together, while those succeeding are more widely spaced, and the height of the fin rapidly diminishes posteriorly. The anal is somewhat shorter than the dorsal, its hinder end being opposite to that of the latter, but its commence- ment is slightly further back than the front rays of the same. There are about 15 rays, preceded by very distinct small fulcra and the remains of larger basal fulcra, and the first eight are closely approximated, while the remainder are more widely spaced and much the shortest. All the rays, both of this fin and the preserved fragment of the caudal, are comparatively robust, and articulated similarly to those of the dorsal, and the branching is seen to com- mence at a point quite near to the base. Scales.—The scales exhibit the vertical elongation on the flank usually met with in deep-bodied Ganoids, and are strikingly similar to those of certain Platysomide (e. g. Cheirodus or Amphicentrum) and Pycnodonts (e. g. Gyrodus). They are ornamented externally with prominent granulations, which tend to merge and form striz parallel to the margins, and the anterior border of each is thickened in the ordinary “ pleuro-lepidal manner ”—an arrangement so well known from Sir Philip Egerton’s graphic description * as to require no further explanation. The “lateral line” upon the trunk is distinct, and extends in a gentle curve from the summit of the operculum to the middle of the caudal pedicle. Systematic Determination.—A hasty glance at this interesting fish impresses one at once with its remarkable superficial resem- blance to some of the Platysomidz; and the relative dimensions of the operculum and suboperculum might also be regarded as indi- cating some affinity with that ancient tribe. One characteristic feature, however, is happily preserved, by which it is possible to definitely decide the question of relationship, namely, the semi- heterocercal tail. This (as well as the nature of the circumorbital bones) is sufficient to lead to the institution of comparisons with other deep-bodied Ganoids of a more modern type, all the Platy- somidee and their allies being markedly heterocercal, and we accord- ingly proceed to the Dapediide and the Pyenodonts. The latter are immediately excluded from consideration by the incompleteness of their opercular apparatus, which seems to consist merely of a single platet, and by the absence of fulcra on their fins. The Dapediide, however, show an agreement in almost every respect. The form of the body and the relations of the fins, the characters of the opercular bones, and the small fulcra fringing the anterior margin of the fins, are all similar; and the new South-African fossil may thus be placed in this family with but little hesitation. Having decided upon the family position, it remains to determine the genus. Dapedius, Heterostrophus, and Tetragonolepis are the only hitherto recognized Dapedioids with which it seems necessary to compare the fossil, and the first two of these are quite distinct * Sir P. Egerton, “On the Affinities of the Genus Platysomus,” Quart. Journ. Geol. Soc. vol. v. (1849), p. 331. + R. H. Traquair, “On the Structure and Affinities of the Platysomidz,” Trans. Roy. Soc. Edinb. vol. xxix. (1879), p. 383. Quart.Journ.Geol.‘Soc.Vol. XLIV. Pl. VI. : _ W.H. Crowther del.et lith. Mintern. Bros. imp. SEMIONOTUS AND CLEITHROLEFIS. EE <== = DEPOSITS OF ORANGE FREE STATE, SOUTH AFRICA, 143 in the mode of articulation of the scales. etragonolepis (Bronn, non Agassiz*), on the other hand, has a truly ‘ pleurolepidal ” squamation, the inner articulating ribs of the scales beg anterior and marginal. But the typical species of this genus are much less symmetrically shaped than the South-African form, owing to the great development of the ventral part of the abdominal region ; though, it must be admitted, at least one of the fragmentary Indian fossils referred by Egerton tf to T'etragonolepis exhibits an almost cor- responding general outline, so far asitisknown. Whether the latter is a correct determination or not remains to be decided by the dis- covery of more satisfactory materials ; but, under any circumstances, it is obvious that the fish now under discussion is quite distinct from the type defined by Broun {, and must therefore be looked upon as representing a different genus. At first sight I was inclined to regard - it as new, but Dr. Traquair has kindly reminded me of a fish from the Hawkesbury Beds (supposed Trias) of New South Wales, described many years ago by Sir Philip Egerton § under the name of Cleithro- lepis granulatus, and I am convinced that the South-African fossil is generically identical with this. Cleithrolepis, up to the present time, has been doubtfully placed either with the Platysomide or the Pyenodontide, but Sir Philip Egerton’s figures and description clearly show that its true affinities are with the family Dapediide ; and the new discoveries here recorded amply confirm this determi- nation. The South-African fish, however, is distinctly a new spe- cific type, as will be seen on comparing the figures, and I therefore venture to name it Clerthrolepis Hxtoni, in reference to Dr, Exton’s important explorations in the early Mesozoic deposits of the Cape. Formation and Locality.—Stormberg Beds (Upper Karoo Series): Rouxville, Orange Free State, South Africa. EXPLANATION OF PLATE VI. Fig. 1. Semionotus capensis, A. 8S. Woodw., hinder portion of trunk. 2. Ditto, head and pectoral fin. cl, clavicle; co, coracoid; d, dentary ; fr, frontal; op, operculum; ord,orbit ; par, parietal; p.cp, preoper- culum ; s.op, suboperculum; s¢, supratemporal; «, cheek-plate. . Ditto, caudal pedicle and fin. . Ditto, scale of flank, inner aspect, twice nat. size. . Ditto, ventral scale, inner aspect, twice nat. size. . Cleithrolepis Extoni, A. S. Woodw. . Ditto, fragment of head and trunk, with pectoral fin. All the figures, except Nos. 4 and 5, are of the natural size, and the original specimens are preserved in the British Museum. (For the Discussion on this paper, see p. 269.) “13 Ot > CO * See Sir Philip Egerton, ‘On the Affinities of the Genera Tetragonolepis and Dapedius,” Quart. Journ. Geol. Soc. vol. ix. (1853), pp. 274-277. In this paper Tetragonolepis was assigned to the Pycnodontide, but the error has sub- sequently been pointed out by both Heckel (Denkschr. k. Akad. Wiss. Wien, vol. xvii. 1855, p. 200) and Traquair (loc. czt. p. 380). Tt Sir P. Egerton ‘‘On some Remains of Ganoid Fishes from the Deccan,” Palzont. Ind. [4] vol. i. pt. 2 (1878),p. 5, pl. iii. fig. 1.— Tetragonolepis analis, Kg. { H. G. Bronn, “ Ueber zwei fossile Fischarten aus dem Gryphitenkalke bei Donau-Eschingen,” Neues Jahrb. 1830, p. 22, pl. i. fig. 2. § Sir P. Egerton, “On some Ichthyolites from New South Wales, forwarded a) = cme W. B. Clarke,” Quart. Journ. Geol. Soc. vol. xx. (1864), p. 3, pl. i. wa 2, 3. 144 MR. A. S. WOODWARD ON SQUATINA CRANEI AND 13. On some Rematns of Sevatina CRANET, sp. nov., and the MANDIBLE of BrLonostomus crnctus, from the CHALK of Sussex, preserved in the Collection of Henry Witter, Esq., F.G.S., Brienron Museum. By A. Surra Woopwarp, Esq., F.G.S., F.Z.8., of the British Museum (Natural History). (Read February 8, 1888.) - [Puare VII] Last year, when attempting to elucidate the dentition of the Creta- ceous Selachian genus Ptychodus, I had the honour of bringing before the notice of the Society an important specimen from the cabinet of Henry Willett, Esq., F.G.8., of Brighton ; and in subsequent studies both of this and of contemporaneous ichthyie types I have been favoured by the same gentleman’s kind permission to make use of the whole of his valuable collection. Among the fossils there are two, bearing upon the subject of recent inquiries, which seem to reveal points of considerable interest and significance; and of these I propose to offer a brief notice in the present communication. The one specimen adds the “ Angel-fish ” (Squatina) to the list of English Chalk Fishes, and apparently indicates a new species; the other makes known some hitherto unrecognized features in one of the most singular of Cretaceous Ganoids, Belonostomus cinctus. I. Sevatina Cranezl, sp. nov. (Pl. VII. figs. 1-6.) The remains referable to the Selachian genus Squatina consist ot a crushed skull, with the mandibular and hyoid arches, and an associated fragment of the pectoral fin, with dermal tubercles. The fossil indicates a small animal, probably not more than thirty inches in length, and the most important of the features it presents are ijlustrated in figs. 1-6 of the accompanying Plate. The skull has been crushed somewhat obliquely from above downwards, the jaws of the right side being displaced to a position beneath the middle of the cranium, and the right hyomandibular cartilage, thrown outwards, is completely severed from these. The difficulties of interpretation are, moreover, increased by the un- fortunate chance-fracture of the specimen on its discovery. One half of the block of chalk (fig. 1) retains the left hyomandibular (hm) and pterygo-quadrate ( ptq) cartilages, with a portion of the lett mandibular (md) and ceratohyal (ch) viewed from the inner side ; in addition to numerous scattered teeth, and the impression of the left half of the cranial roof, to which some of the cartilage adheres. The counterpart block shows the remainder of the left mandibular and ceratohyal cartilages, the complete right hyo- mandibular, and a fragment of the right mandibular; while there are also undeterminable portions of the cranium itself, besides the associated dermal shagreen already referred to. The form and relative proportions of the cranium and its ap- pended arches are very similar to those of the living representative of the genus, so far as they are recognizable. ‘The antorbital pro- BELONOSIOMUS CINCTUS, FROM THE CHALK OF SUSSEX. 145 cess of the skull (wo) presents its usual aspect, and there is the same excavation of the middle of the anterior extremity (ea) of the cranial “ box.” ‘The postorbital process seems to be buried in the matrix, but the contour of the postero-lateral angle of the skull (pla) is quite normal, and the depression in the roof in advance of the occiput is apparently of its accustomed proportions. The pterygo-quadrate cartilage (ptq) is stout and narrow, with the large pterygo-trabecular process ; the precise outlines of the mandibular element are not seen. The left hyomandibular (Am) is perfect, in - position, of the ordinary shape and size; and the large ceratohyal (ch) is shown in pieces upon both halves of the fossil, about two thirds the length of the mandible. There are also apparently some obscure remains of the well-developed labial cartilages. The dentition is not completely preserved, but the anterior teeth of both the upper and lower jaw are exposed to view. Those near the symphysis of the mandible are relatively high and slender (fig. 3), while the opposing teeth attain but small dimensions (fig. 2); more posteriorly, both above and below, the teeth begin to exhibit the usual lateral elongation (fig. 4) characteristic of the sides of the mouth. The minute dermal tubercles (fig. 5) are mostly of an oval form, having the outer enamelled surface ornamented with longitudinal or radiating ridges. They were probably scattered over almost the entire trunk. The larger tubercles, like those occurring upon the margins of the paired fins of the existing Squatina, are also oval in shape, with a slightly crenulated margin (fig. 6). From the middle of each there rises a large backwardly-directed spine, laterally com- pressed, and well enamelled. On comparing the fish, thus fragmentarily indicated, with the species of Squatina already satisfactorily known, it is readily distin- guished by the great relative size of the spinous dermal tubercles. No defences of this character have hitherto been observed in the extinct forms, and those of the living species are considerably smaller in proportion to the size of the fish. The anterior lower teeth are also more slender than in the existing Squatina angelus. I would therefore venture to designate the new English fossil Squatina Crane, associating with it the name of my friend Edward Crane, Ksq., F.G.S., Chairman of the Brighton Museum Committee, as a sight acknowledgment of the services he has rendered to the cause of Paleontology and the Institution over which he now presides. II. Betonosromus crnetus, Agass. (Pl. VII. figs. 7-13.) The lower jaw of Belonostomus has already been, to some extent, elucidated by the. researches of Otto Reis*; but no specimen hitherto described has revealed the precise characters of the denti- tion, or the relations of the hindermost bones. Mr. Willett’s fine * O. Reis, “ Ueber Belonostomus, Aspidorhynchus und ihre Beziehungen zum lebenden Lepidosteus,” Sitzb. math.-phys. Cl. konigl.-bay. Akad. Wiss. Minchen, 1887, pp. 169-172, pl. i. fig. 4. 146 MR. A. S. WOODWARD ON SQUATINA CRANEI AND examples of Belonostomus cinctus supply this deficiency in our know-— ledge of the genus to a considerable extent, and explain the peculi- arities of the fragmentary fossils described by Agassiz, besides making known more completely than before the largest presymphysial bone recorded in the annals of vertebrate anatomy. The principal specimen is shown two thirds of the natural size in fig. 7, and exhibits the mandible and dentition tolerably well preserved, except at the anterior and posterior extremities. The two rami occupy only one half the entire length of the jaw, the anterior half being formed by the enormously elongated presym- physial bone. Each ramus is narrow and deep, gradually tapering in front, and the upper border rises behind, immediately beyond the posterior termination of the tooth-bearing portion. The two rami meet in front at a very acute angle, but imperfections in the fossil do not permit of a determination of the precise characters of the union: the symphysis is elongate, gradually diminishing to a thin edge below, and the enormous presymphysial bone is articu- lated to the sloping triangular surface thus formed (fig. 8). The last-mentioned bone is a median unpaired element, very gradually tapering to a point anteriorly ; it is hollow, compressed below (fig. 9 a), keeled inferiorly in the anterior portion, and marked by a shallow longitudinal channel above. As shown both by this specimen and by another less perfect fossil (fig. 9), originally figured by Dixon, the presymphysial bone is pro- vided with a powerful prehensile dentition. There is a median row of large conical teeth, widely and irregularly spaced, but smaller and more closely approximated in front than behind. These teeth are nearly thirty in number, and each has the form of a hollow cone, enamelled to within a very short distance of the base (fig. 10). The greater length of the enamelled portion is delicately striated, but near the tip the tooth suddenly tapers more rapidly and is smooth. A great number of similar teeth of small size—the largest being little more than one sixth the height of the largest of the median series—are placed irregularly upon the lateral margins of the bone; they are closely clustered together in more than one row, and perhaps somewhat more pointed than the median teeth. Like the latter, they are not placed in sockets, but merely anchylosed to the bone. The large median teeth end abruptly at the posterior extremity of the presymphysial element ; but the small lateral teeth are con- tinued backwards upon the rami of the jaw, increasing in size and at the same time becoming relatively shorter and adapted for crush- ing. Anteriorly, for a very short space, the dentigerous margin is evidently formed by the true dentary (d@); but this bone is soon ex- cluded from the upper border, and the large splenial element (spl) takes its place. The suture between the two bones is well shown in the side view (fig. 8s). Minute teeth extend far downwards upon the inner side of the splenial, and as the dentition becomes still more adapted for crushing behind, the upper margin of the element is considerably widened, until the anterior width of 2-5 millim. has BELONOSTOMUS CINCTUS, FROM THE CHALK OF SUSSEX. 147 passed into a horizontal extent measuring 8 millim. across. The teeth upon this surface are quite mamilliform—somewhat suggestive of the tubercles upon the test of certain Kchinoids, like Cidaris ; and some of the stages by which this extreme form is reached are illustrated in figs. 11-138. It thus becomes evident that the original specimens described by Agassiz as portions of the mandibular rami of Belonostomus cinctus are really fragments of the presymphysial bone of this species. In the closely allied genus, Aspidorhynchus, a relatively small, dentigerous, presymphysial bone has been known for some years, and its homologies have already been discussed, in conjunction with the corresponding element in certain Dinosaurs, by Messrs. Dollo* and Hulkey. It is only lately, however, that the same bone has been discovered in Belonostomus. A specimen of B. speciosus, Wagn., from the Lithographic Stone of Bavaria, described last year by Otto Reis (loc. cit.), reveals a presymphysial bone of considerable size, articulating with the mandible by a < - shaped suture; and a de- tached example of the same bone of the Liassic B. Anningie ¢, in the British Museum (no. P. 513), exhibits the same peculiarities (fig. 14). In B. cinctus, as described above—and as is especially well shown in the original of fig. 9—the surface of sutural union with the symphysis is one plane without angulation ; and the pre- symphysial element itself may perhaps be relatively larger than in the earlier species. It may also be added that the mandibular rami of Aspidorhynchus present a very close approximation to those of Belonostomus, although the splenial, in the last-named genus, assumes greater importauce as a dentigerous element, and the teeth it sup- ports appear to be more adapted for crushing. Some interesting general considerations are suggested by the foregoing brief study of the detached mandible, when taken together with certain other known points in the skeletal anatomy of Belono- stomus ; but these questions have been so recently discussed in the memoir by Otto Reis already quoted, that it will suffice in conclu- sion merely to note that he has treated the subject in detail. EXPLANATION OF PLATE VII. Fig. 1. Crushed head of Squatina Cranei, A. 8S. Woodw., natural size. Lower Chalk, Clayton, near Brighton: ao, antorbital process of cranium ; ch, portion of ceratohyal ; ex, excavated anterior extremity of cranium; km, hyomandibular ; md, portion of mandibular ramus; pla, postero- lateral angle of skull; pg, pterygo-quadrate. 2. Anterior upper tooth of ditto, side view, twice natural size. 2a. Base of another, under view. 3. Anterior lower tooth of ditto, inner aspect, twice natural size. 3a. Base of another, under view. * L. Dollo, “ Quatriéme Note sur les Dinosauriens de Bernissart,” Bull. Mus. Roy. d’ Hist. Nat. Belg. vol. ii. (1883), pp. 226-229. tT J. W. Hulke, Presidential Address, Proc. Geol. Soc. 1884, pp. 47-51. { Since the reading of this paper I have discovered that this species is truly referable to Belonorhynchus, Bronn, and is not improbably identical with B. acutus, Agass. sp. 148 ON SQUATINA CRANEI AND BELONOSTOMUS CINCTUS. Fig. 4. Posterior side teeth of ditto, twice natural size. 4a. Base of another, under view. . Minute dermal tubercles of ditto, four times natural size. . Large spinous dermal tubercle of ditto, twice natural size. . Mandible of Belonostomus cinctus, Agass., viewed from above, two thirds natural size. Upper Chalk, Brighton. . Side view of portion of ditto, natural size: d, dentary ; prs, presym- physial bone ; s, sutures; sp/, splenial. . Another presymphysial bone of ditto, showing suture, natural size. Upper Chalk, Brighton. 9 a. Transverse section of presymphysial bone. 10. Median presymphysial tooth of ditto, twice natural size. 11. Lateral presymphysial tooth of ditto, thrice natural size. 12,13. Teeth of splenial bone of ditto, side view, thrice natural size. 13 a. The second, viewed from above. 14. Presympbysial bone of Belonorhynchus Anningie, Ag. sp., natural size. Lower Lias, Lyme Regis. [Brit. Mus. no, P. 513.] The originals of all the figures, except the last, are in the collection of Henry Willett, Esq., F.G.S., Brighton Museum. Oo OC TIO or Discussion. The Presipent spoke of the clear manner in which the Author had laid before the Society the salient points of his paper, with the conclusions of which there appeared to be general agreement. “SNONLOLSONOTHS’ ANY VNIIVAOS SNORDVIAYD “dunt *Soag Ulery “UU Pp teyyMo7) pT 'M TIA Id ‘ATX 19A 2°99 Joep; ump 42en, ON THE RED-ROCK SERIES OF THE DEVON COAST-SECTION, 149 14. The Rev-Rock Serres of the Devon Coast-sxcrion. By the Rev. A. Irvine, B.Sc., B.A., F.G.S. (Read January 11, 1888.) A stay at Sidmouth during the past summer (supplemented by a second visit to the county in the Christmas holidays) has afforded me the long-wished-for opportunity of forming a personal acquaint- ance with the Red-Rock series of the Devon region, rocks which were described many years ago by Mr. Godwin-Austen * under the name of New Red Sandstone, and have been more fully described since by Mr. Ussher t. The paper by the latter author is of great value, as it is a very mine of facts and observations. In working along the coast-sections, however, I saw reasons for doubting the correctness of including the whole series in the Trias, and as I went on and compared what I observed with the results of the work of former yearst in the Dyas and Trias of Germany and of the northern and midland counties of England, I was forced to the con- clusion that in the Devon region we have those two systems re- presented. I propose to lay before the Society in this paper an account of the observations which I have made, and to state the conclusions which (on comparative grounds) I have drawn from them. SrpMourH (East). (1) The escarpment of the Sid, for some 300 yards from its mouth, consists of about 50 feet of thick-bedded coarse sandstones, of a prevalent peppery-grey colour, in fresh sections, the general red colour of their weathered surfaces being due to rain-wash from above and- subsequent infiltration. They exhibit magnificent current-bedding, such as we commonly meet with in the Bunter. They are slightly brecciated. Intercalated with these and quite subordinated to them stratigraphically are current-bedded breccias in a marly matrix, the contained fragments being mostly of indurated red marl. This series is seen dipping east in the coast-section and passing under (2) A series of massive beds of sandstone of finer texture, of a pale French-grey (except on their weathered exterior$), containing occasional fragments of red marl from which the calcareous matter has gone, and from the surfaces of which the iron has been leached out, so that they have acquired a superficial tint lke that of the mass of the sandstone in which they are found. Only the very feeblest current-bedding is seen in these sandstones. Subordinated * “The Geology of the South-east of Devon,” Trans. Geol. Soc. vol. vi. + “The Triassic Rocks of Somerset and Devon,” Quart. Journ. Geol. Soc. November 1876. { Vide Geol. Mag. dec. ii. vol. ix. (1882), dee. iii. vol. i. (July 1884); Quart. Journ. Geol. Soc. November 1876, i+¢d. August 1884; Proc. Geol. Assoc. vol. iy. “ Notes on the Geology of the Nottingham District.” § The irony colouring-matter has penetrated in some cases to a depth of 3 or 4 inches. 150 REY. A. IRVING ON THE RED-ROCK to them, and increasing in importance as we ascend the series, proper Keuper marls occur, mostly brown-red, but variegated with pale-grey layers and irregular patches. The first important marl- bed is from 10 to 12 feet thick. The sandstone bed next above this is 10 feet thick. In some of these marls there are included well- rolled blocks of an older marl, the parent rock of which we shall perhaps be able to identify as we proceed. (8) Next, in ascending order, comes on, by a gradual transition, a Series in which marls predominate, the sandstones (although pretty persistent) being much more fully developed and quite subordinated to the marl-beds. These marls occur in very massive, well differen- tiated beds, with little or no lamination, very hard and tough, split- ting on the face of the cliff in a rude prismatic and subcuboidal fashion, the fallen masses weathering subspherically. In the more fine-grained and compact varieties, where masses haye been split off by frost action, the rock shows what one must be allowed to call ‘“conchoidal ” combined with “splintery fracture” on a large scale. This character of the beds is maintained through a vertical range of about 150 feet. Throughout this range the marls are characterized by the presence of numerous calcareous concretions *, many of these being geodes lined with crystals of calcite. I saw one rock mass on the shore, partly buried in shingle, of a decided tufaceous character ; but this I regard as the result of deposition from the calcareous springs which escape from these beds on the clifi-face. Regular layers of the concretions described (like the layers of flints in the Upper Chalk) run through the more compact marls in parallel lines of bedding. Passing from east to west (7. e. towards Sidmouth), the concre- tionary masses first crop out on the cliff-face about 3 mile west of Salcombe Dingle, in a bed of rather sandy marl about 2 feet thick. From the pale-grey colour of this bed, it marks a very defi- nite horizon, which can he followed with the eye all along the face of the cliff as it rises to the west, until it is cut off on the hill-flank. This gives us a very good upward limit for the concretionary cal- careous series. So far as I could see, all the beds above this are more uniformly marly and devoid of these concretions. (4) East of Salcombe Dingle the marls become gypsiferous for about 150 feet; and as they are continued upwards subordinate beds of pale green marls begin to appear. These become more pro- nounced higher up the cliff, until at last they supersede the deep red marls altogether. These pale-green marls were examined in numerous fallen blocks at the foot of the cliff, weathering sub- cuboidal (occasionally shaly). Traces of pseudomorphs after sodium- chloride crystals were noted, but time didnot permit a thoroughsearch for these. They are probably soon obliterated by the attrition of sand and shingle driven by the waves at high tides. The gypsum is only * An analysis of the more compact portion of one of these nodules in my laboratory failed to detect any trace of magnesia. A further quantitative ana- lysis gave 11-01 per cent. of carbonate of lime, and 1:01 per cent. of Fe,O,. The residue was for the most part a fine earthy powder, very little sand. SS See ee SERIES OF THE DEVON COAST-SECTION. 151 seen in veins, none apparently more than from 1” to 2'’thick. There seems to be an entire absence of massive beds of anhydrite, such as occur at Newark and elsewhere in the Midlands; but the relation of the gypsiferous beds to the green mars is the same. In this cliff-section to the east of Sidmouth we have the most complete development of the normal Keuper formation of the Mid- lands. I saw no trace of the Rheetic formation (properly so called) as represented in this country by the Avicula-contorta shales *. The pale-green marls here as elsewhere T cannot -be separated on physical or stratigraphical grounds from the Keuper, of which they form the uppermost portion, though for purposes of mapping it may be convenient to include them in the “‘ Penarth Series.” Beneath the Upper Greensand beds which cap the hills between. Salcombe and Weston Dingles, the pale green marls are developed in such force as to mark the uppermost horizon of the Keuper. Owing to their inaccessibility on the face of the cliff, I could not determine their actual thickness above the highest red-marl bed, nor could I ascertain to what extent they may have been disguised by the down-wash of material from the Upper Greensand beds above. Estimating the thickness of the Keuper exposed in this portion of the cliff at 300 feet, and adding to this another 100 feet for the beds which crop out in the cliff below them to the west and above the calcareous series, we get about 400 feet of marls in which marked beds of sandstone seem to be of rare occurrence t. This, for some reasons, we might take as the approximate thickness of the Upper Keuper here; or, if we include in this division the 150 feet _ of beds marked by the prevalence of calcareous concretions, we get 550 feet. Then the Lower Keuper series of massive sandstones and red and variegated marls gives us another 60 feet. We thus get an estimate of 610 feet for the Keuper as against the 1350 feet estimated by Mr. Ussher §; or, if we allow, say, 50 feet for removal by denudation of pale-green marls at the top, an outside estimate of 660 feet. There is very little faulting in this part of the cliff ; two small faults with an aggregate downthrow to the east of about 15 feet are cancelled by an apparent fault with a downthrow to the west of from 15 to 20 feet at Salcombe Dingle. The red marls at Seaton, which I examined about four years ago, I take to be a repe- tition of the beds in the middle part of the cliff between Salcombe Dingle and Branscombe Mouth, by the faulting which has let down the Chalk at Beer Head, just as in the beds east of the Sid those in the Peak and High Peak hills are repeated by the faulting at Sidmouth. * By this is intended the series of paper-shales and thin-bedded sandstones, marked by the occurrence of the “bone-bed,” of Cardiwm rheticuwm, Pecten valoniensis, Avicula contorta, and Pullastra arenicola. t+ E.g. at Newark and Edwalton (Notts), and in the Garden Cliff at West- bury-on-Severn. ¢ I saw on the beach a solitary block of ripple-marked sandstone, to the great abundance of which in the Upper Keuper of Notts I have previously drawn attention (Quart. Journ. Geol. Soc. November 1876, p. 515). § Loe. cit. p. 392. 152 REY. A, IRVING ON THE RED-ROCK SrpmMoutH (WEst). The Chit Rock at the western end of the Esplanade is a portion of the same coarse, strongly current-bedded series which is exposed in part in the escarpment of the Sid, near the eastern end. The projection of this rock towards the sea is obviously explained by a ereat fault on its western face, by which it is brought against the calcareous concretionary series in its upper portion. Its “throw” cannot be less than 200 feet. The beds dip west from this fault for about 200 yards, when another fault of about 50 feet down- throw to the west occurs. From this point they gradually rise west- wards, so as to form a gentle faulted synclinal. In consequence of this the dip of the Keuper beds in Peak and High Peak Hills is to the east, concordantly with the dip of those in Salcombe Hill to the east of the Sid. The highest beds accessible from the beach are marked by the same concretionary calcareous nodules as in the eastern cliff; there appears to be a similar upward limitation of them; and as the beds below crop out in succession along the shore, these conditions are maintained until their downward limit is reached on the outcrop of a massive marly bed, with many included lumps of grey and red marl (such as those described in the marls about the same horizon to the east); and to these a somewhat con- centric laminated structure has been imparted, as if they had been rolled about in water while in a pasty state. This well-marked bed (on both sides of Sidmouth) makes a convenient horizon for separating the Upper Keuper marls from the Lower Keuper Sand- stone series. The latter, with their interstratified red and varie- gated marls, attain here about the same dimensions (60 feet) as in the cliffs to the east; but the marls are more feebly developed. Such massive sandstone beds are (as is well known) a common fea- ture of the Lower Keuper in other districts, as, for example, near Nottingham (Quart. Journ. Geol. Soc. Novy. 1876, p. 515), at Grins- hill, Salop, and in the Severn country. The Grinshill stone, one of the most durable of sandstones, is quarried in them. Beneath the beds just described as forming the Lower Keuper, the massive, strongly current-bedded (Bunter) sandstones, with intercalated marly breccias, crop out; and these are continued to the mouth of the Otter and Budleigh Salterton. As they are fol- lowed to the west they continue to rise steadily until Ladram Bay is reached, where a considerable (nearly vertical) fault occurs. The downthrow to the west cannot be less than 100 feet, since it has let down the Lower Keuper sandstone series of beds and a portion of the marls above them to a level with beds of rather a low horizon in the Bunter series. These Lower Keuper sandstones form the Lade Rock, the promontory on which the coastguard station is placed; and it is the boring of the sea through the weaker, current- bedded Bunter beds at the base which has formed the “natural arch,” an object of curiosity to tourists and others. The beds then rise again westwards; but in the higher partof the cliff above the smaller bay to the west (separated from Ladram Bay by Bad- “ie Se ee a OS SERIES OF THE DEVON COAST-SECTION. 1ba field’s Point) the Lower Keuper series is recognized again. This is their last appearance in the coast-section as we work west. The very unequal weathering of these Bunter beds, owing in part to their being slightly but very unequally calcareous in places, has given to the cliffs and the outstanding “stacks” a very weird and grotesque appearance all along to Otterton Point *. ‘ Tur Orrer Mourn anp BupreicH SALTERTON. On the east side of the mouth of the Otter the deeply eroded Bunter cliffs are well worthy of study. Here we seem to come across the first traces of reconstructed materials from the great breccia series which occupies such a large extent of country further to the west and south. An irregular band of breccia f occurs inter- calated with the sandstones, just above high-water mark. I searched the exposed portion of this minutely, but failed to find more than one or two fragments sufficiently rounded to be called pebbles; nearly all the fragments appeared to be slightly subangular. Among them I noted fragments of slate slightly cleaved (such as occurs around the granite on Dartmoor), vein-quartz, trap (various), reddish granite (the felspar slightly kaolinized), an older grit containing felspathic fragments, quartzite (dark grey, red, and yellow). The few pebbles which formed the exceptions to the rule were composed of either trap, quartz, or quartzite. A second breccia occurs here- abouts, in which all the contained fragments are of hard red marl. The matrix of both these breccias is fairly hard, owing to cal- careous cementation. On following the river escarpment inland for about a mile, this breccia-bed is met with frequently; and in some places I saw over- lying it a fairly indurated sandstone, with pebbles and subangular fragments scattered rather freely through it, as so often happens in beds of the Middle Bunter. These beds are to be identified on the other side of the mouth of the Otter at the eastern end of the Esplanade, where 12 feet (vertical) of them are exposed, with the same breccia at their base, lying on an eroded surface of more homogeneous sandstone, a capital instance of ‘“‘ contemporaneous erosion.” The same beds appear again (evidently on the same horizon by the dip) about 100 feet above the principal pebble-bed, west of the Rolle Hotel (see infra). A striking feature on both sides of the Otter is the occurrence of hard, liver-coloured, calcareous sandstone, in regular layers several inches thick, while the same material occurs as (apparently) infillings of curious irregular tubes in the sand rock, in such a manner as to suggest the ramifications of roots of trees in a soil, and the possible traces here of a Triassic “ submerged forest.” In all the sections in which I have identified these coarse current- * It is possible that these rocks on the cliff-face have undergone some ‘ hyper- phoric’ change, from the long-continued action of the spray of the sea. t These I take to be the “Conglomeratic beds” of Mr. Ussher, Joc. cit. p. 380. Q.J.G.8. No. 174. M 154° REY. A. IRVING ON THE RED-ROCK bedded sandstones inland, they have a prevailing colour of yellowish white with streaks of red, becoming, of course, more reddened by exposure in road- and railway-cuttings, especially where (as it often happens) the surface-soil contains much red marl; and eyen in the cliff-section their variegated (bunt) coloration is in places obser- vable. The magnificent pebble-bed cut through in the coast-section at Budleigh Salterton has had so much attention bestowed upon it that it would be superfluous to attempt to describe it here minutely. While the ‘‘ pebbles ” are for the most part of quartzite, it should be noted that I observed in it occasional fragments of Dartmoor granite in an advanced stage of disintegration ; but the important point is the index as to their origin (in many cases) furnished by their contained fossils of Silurian age. The bed thus appears to consist of a mixture of detrital material derived partly from the rocks of the ancient Devon highlands, and partly (mostly) from strata lying at a greater distance (perhaps in Cornwall or Brittany, or the intermediate region*). Whether the latter came directly from such sources or were brought into their present locale indirectly by the waste of older pebble-beds of Old Red age, we have, perhaps, no means of deter- mining. It leads to the necessary inference that considerable changes in the physiography of the region must have taken place in order to bring into the basin materials from more distant sources than those from which the materials of the older breccias and conglomerates were derived. It seems pretty clear that the two series were deposited in dif- ferent hydrographic basins which were far from being conterminous with one another, the later (the Triassic) having been very much the more extensive. I have inspected the collection of Silurian fossils from the Salterton pebble-bed in the Exeter Museum, and have had the privilege of seeing the private collection of Mr. Vicary. The presence of these fossils in the pebbles, added to the extremely smooth and worn condition (the pebbly roundness) of some 90 per cent. of the Salterton pebble-bed (the materials which can be traced to the breccia series further to the west not exceeding, I should say, 10 per cent), together with the recognition in the fossils of a strong French type by Salter, argue strongly for the view which is here put forward. | Whatever their source, there is to my mind very little difficulty in recognizing in the beds which contain them representatives of the great Middle Bunter pebble-beds, as these are splendidly developed at Sutton Coldfield and elsewhere in the Midlands; even the pitting of the pebbles by the crunching effect of mutual pressure is as common in the one case as in the other; but they are not the sole representative of that division of the Bunter. In the strata which occur for about 100 feet above the main pebble-bed, and are in part parallel and interdigitate with it, I recognized the pebbly sandstone of the Middle Bunter, as this is exhibited in the Castle * Compare Bonney, Quart. Journ. Geol. Soc. vol. xl. p. 25. OO ————— ——— SERIES OF THE DEVON COAST-SECTION. fi /3) Rock at Nottingham, on the Nottingham Forest, at Sneinton *, and in many other places in that district. We thus get about 200 feet of beds in the Devon coast-section, with a distinctly Middle Bunter facies, just in the position, with reference to the Keuper, in which we should be prepared to find them, if we recog- nized in the current-bedded sandstone series between them and the Keuper basement-beds the equivalents of Prof. Hull’s Upper Bunter. The Deep Red Marls which crop out beneath the pebble-bed in the cliff at Budleigh Salterton differ, so far as I have observed them, in some respects from the undoubted Keuper Marls to the east. There appears to be just that difference which those who are familiar with them could hardly fail to recognize between the Keuper and ‘‘Permian ” marls of Nottinghamshire. Of these latter I consider the red marls at Budleigh Salterton the representatives. In colour, in their fine argillaceous composition t, in their way of weathering, in the frequent occurrence of small grey-green specks of more calcareous material, in the apparent absence of any very distinct stratification, there is, to say the least, a strong similarity between these and the Permian Marls which are associated with the Magnesian Limestone in Nottinghamshire. I have but little doubt that the weathering Diagram-section showing junction of the Budleigh-Salterton Pebble-bed and Permian Marls. Ss. of Ww. N.of E Od T= =o" a. Maris of deep purple-red, referred to the Post-Carboniferous (Permian). 6, The Budleigh-Salterton Pebble-bed, strongly current-bedded in parts, with strong bands of coarse irony current-bedded sands intercalated. ¢. Coarse current-bedded irony sandstone, with pebbles of quartz and quartzite and angular and subangular fragments of (in some cases) younger rocks scattered through it (fragments of the marls @ very common). A type of pebbly sandstone very frequent in the Middle Bunter of the Midland Counties. * There is at present (Sept. 1887) a very fine exposure of these beds in the railway extension works in progress at this place. Above them lie about 8 feet of thin-bedded sandstones which, I think, Prof. Hull would call Upper Bunter. + This comes out in the superior qualities (compactness, hardness, density) of the bricks made from them. ‘This is well known in the Nottingham district ; and at the Society’s meeting I exhibited a portion of a very fine-grained paving- brick made from these (Permian) marls at brick-works situated just below the boundary of the pebble-bed, on the Exmouth road. M2 156 REY. A. IRVING ON THE RED-ROCK and disintegration of these marls has furnished the numerous indurated fragments of precisely similar marl which are found (as described above) throughout the series of beds which I have ventured to identify as the Bunter; and it would be difficult to deny that it is to these marls that we may look for the finer marly detritus which constitutes the material of the intercalated (often lenticular) marly bands of that formation in Devon as in the Midlands. At the base of the Salterton pebble-bed we have, I believe, direct evidence of a physical break in the series. It may be summarized thus :— (a) Stratigraphical.—N ot very direct or conclusive. Taking the sandstone-beds as indicating the dip of the pebble-bed as a whole, a careful measurement gave a dip 4° N.N.E. An equally careful measurement of the dip of the underlying marls along the line of one of the even pale-grey bands, where the marls first appear from beneath the pebble-bed on the shore, gave a dip 5° N.N.E. Half a mile west of Budleigh Salterton is a fine gorge in which the horizontal strike of the pebble-bed is seen running due N. and 8.; the dip noted above must be therefore very nearly the true dip of the pebble- bed. There is a considerable discordancy of dip among the marl- beds themselves, so that it is not easy to say what the general dip of that formation may be. Beyond the gorge just mentioned both they and the pebble-bed are nearly horizontal in the upper part of the cliff; and west of the coastguard station I measured the dip of the marls and found it nz7 on both the converging sides of a cove about 300 feet above the shore. (b) Physical.—This I consider to be strong. (i.) The pebble-bed at Budleigh Salterton lies on an eroded surface of the marls. This is not always seen on the cliff-face, owing to the lodgment of fallen débris from the pebble-bed above on the projecting ledge formed by the more coherent marls; but at and near the easternmost portion, where the loose débris is swept away by the waves, it is very clear (see diagram, p. 155). At the eastern end I found a surface of several square yards, showing erosion into a wave-like form, exactly as in the Reading Clays (¢.g.) beneath the quaternary gravels. This surface was coated over with a limonitic paste, which followed the mequalities of the surface, and filled up the interstices between the pebbles above, sometimes for as much as a foot or more. It is undoubtedly a deposit by infiltration through the pebble-bed. At one place a layer of reconstructed marl was seen about two yards up in the pebble-bed—evidence, as I take it, of contemporaneous denudation of these marls. ‘The erosion of the marls at the base of the pebble-bed may be seen by the side of the footpath up the gorge. (ii.) Thereis no trace whatever of a passage. The Red Marls (an indurated silt of the finest powder) give place suddenly and abruptly (without any sign whatever of approaching change in the marls) to a deposit of the coarsest rolled detritus, as strongly current-bedded as any I ever saw. ‘The change is in fact such as can only be explained by pre- vious induration and planing-off of the marls, contemporaneously SERIES OF THE DEVON COAST-SECTION. 157 with such changes in the physiography of the region as must imply a considerable lapse of time. Taking the evidence altogether, there appears to be about as great a break as that insisted on by Mr. Aveline in the Nottingham and Yorkshire area; not quite so great perhaps as that described by me at the same horizon in Central Germany (Thiiringen, Meerane), but certainly as great as has been recognized by our sub-committee (Permian and Trias) at this stage of the British geological series. Here, then, we seem to have recorded a certain definite break in time, and to have reached the lowest limit of the Trias, as it is exhi- bited in the coast-section ; and if we recognize in the 200 feet of the sandy series next above (including the chief pebble-bed) the equivalent of the Middle Bunter of the Midland and Cheshire Area, it will be seen that the absence here of the whole of the Lower Bunter marks a stratigraphical as well as a physical break in the serves. One thing I assert with some degree of confidence, namely, that the rocks of the Devon coast-section, from the base of the Budleigh-Salterton pebble-bed to the base of the Keuper (as it is defined in this paper), are the Devon equivalents (taken as a whole) of the Bunter series, as worked out and demonstrated many years ago by Prof. Hull * in numerous sections. THE BREccrIA-SERIES. In this are included the “ Lower Sandstone” group of Mr. Ussher; for in these true breccias seem to form a very large proportion of the rocks, and even the interbedded sandstones are often markedly brecciated, as may be seen in the railway-sections between Star Cross and Dawlish. They form apparently the upward extension (with a more sandy facies) of the more uniformly brecciated series which is so splendidly developed in the bold cliff-sections between Dawlish and Teignmouth. The following points seem to me specially worthy of note, by way of contrast between these breccias and the strata which I have recognized above ‘as constituting the Trias of Devon :— (1) They are distinctly brecciated (more or less) throughout, with a very crude stratification, and appear to be a series of terres- trial and littoral deposits on the flanks and near the shore-line, probably in land-locked bays, of the Paleozoic and Archean moun- tain-region, of which Devon, Cornwall, Brittany, Wales, the Isle of Man, Cumberland, the Scottish Highlands, the Outer Hebrides, the Shetlands and the Orkneys are but the ‘‘ worn-down stumps,” as I have previously suggested elsewhere ‘. (2) Their high inclination (the dip being, I believe, never less than 10°, though often 20° or more) is a fact to be perhaps explained by their being mainly composed of the detritus of a mountain- system (somewhat as the Rigi Conglomerates are related to the * Vide ‘Permian and Triassic Rocks of the Midland Counties,’ figs. 28, 41, 45, 47, et passim. +t Quart. Journ. Geol. Soc. Feb. 1883, p. 79; also August 1884, p. 400. 158 REY. A. IRVING ON THE RED-ROCK higher and older Alps) undergoing subaérial waste, and not of necessity resulting altogether from subsequent upheaval. For the most part the (false) dip is probably only current-bedding on a large scale. Vast accumulations of such detrital matter are not unfre- quently met with-in the wider parts of modern Alpine valleys as the work of great downpours in the mountains *. (3) These breccias, as compared with the softer rocks of the Trias (even though the matrix is much less calcareous), are much more indurated. This may not appear so manifestly on the weathered surface of the rocks as where the rock is quarried and used for building-stone. (4) As pointed out long ago by Mr. Godwin-Austen 7, and more recently by Mr. Ussher +, the materials of the breccia-series appear to have been derived wholly from the adjacent primeval land, exactly as those of the Rothliegendes are traceable to the older porphyritic and other rocks of Thiringen, where they flank that ancient mountain-island, and to the syenitic rocks of the Dresden region further to the east §. On the other hand, the materials of the Triassic series (as that term is limited in the present paper) do not admit of such a distinct derivation; they are rather admixtures of reconstructed materials from the breccia-series with materials brought from other and probably more distant sources. The dis- tinction holds good in the Devonian region as in that of the Thiringerwald and other parts of Central Germany. (5) The larger fragments (boulders, in fact) included in these breccias seemed, so far as I observed them, to be just about as much rounded off by the rolling action of water as we commonly observe in the diluvial detritus which is frequently met with where great mountain-gorges terminate in lakes. The valleys, moreover, which intersect the Northern Alps often exhibit just such accumulations of detritus for miles, in the clean sections cut by the erosive action of the present (and, in some cases, of older) rivers. On the other hand, I failed to observe a single “ pebble ” of the Salterton type in any of the sections of these breccias or in the blocks of fallen débris on the shore, though constantly on the look- out for them; and inquiries made of intelligent residents at Teign- mouth led to the same negative result ||. * A few summers ago I observed such a widespread sloping mass of material brought down from the mountains by a single storm, and spreading (with a general slope of about 10°) right across the wide valley below Davos-am-Platz ; fields and gardens were all obliterated, and the high,road had to be re- excavated, a good example of a Schlammstrom. Similar work was done in the Puster Thal in the autumn of 1885. Cf also Liyell, ‘ Student’s Elements, 3rd ed. pp. 19, 20, and fig. 7. ft Trans. Geol. Soc. vol. vi. pp. 453-7. t Loe. cit. p. 388. § See Quart. Journ. Geol. Soc. August 1884. Compare also the derivation of the “ Brockram” of the Vale of Eden from the Carboniferous Limestone (Geikie, ‘ Textbook,’ p. 758). || I made a special, though fruitless, search for them in the enormous quan- tities of fallen material of the more conglomeratic strata between the Ness and the inn known as Labrador. ” SERIES OF THE DEVON COAST-SECTION. 159 (6) The deep rich red colour of the rocks of the breccia-series and the marls, as compared with the comparative absence of colour in the Bunter (except on weathered surfaces), is another (though minor) point of distinction. This difference extends even to the colour of the soils, the deep crimson-red of the fresh-ploughed fields over the area occupied by these rocks being (as in the Thiiringen country) at once distinguished by the eye from the reddish-brown colour of the soils of the Triassic region *. (7) The admixture (as pointed out above) of materials derived in all probability from these breccias with materials from more distant sources in the Budleigh-Salterton pebble-bed. (8) Whatis perhaps the most significant fact of all after (7) is the difference between the general direction (if there is one) of the dip (and consequently of the strike) of the breccia-series as compared with that of the true Triassic series. In the study of the diagram (fig. 1) which accompanies Mr. Ussher’s paper (Quart. Journ. Geol. Soc. loc. cit.) it is obviously necessary to bear in mind the fact that the coast-line at the mouth of the Exe takes a turn to the south, and the general dip for that portion of the section is nearly in the direction north. In the upper part of the Crediton Valley about a mile above Yeo- ford Station, some fine railway-sections show a dip of 10° W. (20°S.). It is well seen in the cutting on the Plymouth line, which is in the plane of dip, as proved by the horizontal strike of the beds (1) in the vertical weathered face of an older section at right angles to this line, (2) in the cutting near by on the Barnstaple line, which by the compass is at right angles to the Plymouth line. The direction of the dip and the nature of the detritus both point to the great felspathic outburst of the Posbury Hills to the east as the source of the materials. Mr. Ussher records a similar local dip of 10° 8. on the north side of the valley (p. 391). There is a very fine fresh section just south of Dawlish, the cliff having been recently shorn down to a smooth surface, where the fall of the cliff happened some twe years ago. A comparison of the beds, here laid bare in the most perfect fashion, with the beds which rise to the south on the other side of the gorge reveals the presence of a fault with a downthrow of about 150 feet to the south, the several beds being easily identified on either side of it. CoNCLUSIONS. I. The rocks which have been described as a sort of reduplicated Trias (recognizing six divisions) seem to fall into two separate and * Cf. Jukes, ‘Manual of Geology,’ p. 608; Geikie, ‘ Textbook, p. 751. t With reference to the importance here attached to the very brecciated character of this lower series, as compared with the “ pebble-beds” of the Bunter, attention may be drawn to the value assigned by Sir Charles Lyell to such evidence. See ‘ Student’s Elements,’ p. 381, 3rd ed. 160 REY. A. IRVING ON THE RED-ROCK independent systems *—the Post-Carboniferous and the Trias— between which a certain break seems to be indicated at the base of the Budleigh-Salterton pebble-bed. II. The Post-carboniterous (Permian) of Devon seems to maintain, in broad outlines, the Dyassic order of the German series. The great breccio-conglomeratic series (including the Lower Sandstones of Mr. Ussher) is recognized as the equivalent of the Unter-Rothlie- gendes of Germany, even to the extent of assuming a more sandy facies in the higher beds, as that formation does, e. g. near Gera, where it visibly underlies the Zechstein and overlies the contorted Culm-Measures with seams of anthracite; and again at the base of the Wartburg Hills, where it is seen underlying the Zechstein series in the splendid sections at Eppigsnellen on the one side, and on the other side in the sand-pits by the Frankfort road beneath the Wartburg (as well as in Wilhemsthal below the Hohe Sonne), subjacent to the granitoid breccio-conglomeratic series of the Ober- Rothliegendes. The ‘‘ Lower Marls” of Mr. Ussher appear to be the southern equivalents of the Magnesian Limestone series of Durham, and the representatives of the ‘‘ Permian” Marls of Warwickshire and Staf- fordshire, an intermediate facies of the upper division of the Dyas appearing in the interstratified series of Magnesian Limestones and Red Marls of Nottinghamshire. The Lower Sands of Mr. Ussher must be regarded as merely the transitional assortment of materials between the breccias and the marls; they are thus all three closely linked together in one and the same geological system. III. From the base of the Budleigh-Salterton pebble-bed upwards we have the English Trias (properly so called) of the Midlands repeated in outline. While there may be room for difference of opinion as to the correlation of the several divisions of the Bunter of Devon with those of the Bunter of the Midlands and of Salop and Cheshire +, the Keuper of Devon (as the term is limited in this paper) presents quite the normal facies of the Keuper of those regions. IV. The much lower estimates given in this paper for the groups of strata here recognized as Keuper and Bunter respectively than those given by Mr. Ussher, owing to repetition of the beds by faults, compare very well with those of Prof. Hull for the same formations (Keuper 500 or 600 feet) as they are developed in Nottinghamshire aud Gloucestershire £. V. I need hardly say that Mr. Ussher’s suggestion that the Salterton pebble-bed may be the homotaxic equivalent of the Muschelkalk must appear to me altogether inadmissible. It is far * No objection could perhaps be urged to the comprehension of the whole Devon series under the older term ‘New Red Sandstone,’ as was done by De la Beche and Godwin-Austen; and this, if admitted, is a condemnation of their inclusion under the name T7ias, a term of much more restricted range. t See Jukes, ‘Manual of Geology,’ p. 608, fig. 160. ¢ ‘Permian and Triassic Rocks of the Midland Counties,’ p. 103. SERIES OF THE DEVON COAST-SECTION. 161 more likely that this is to be found in the lower part of the sand- stone-marl series of the Keuper (as here defined) ; and those who are familiar with the succession in continuous sections of the Bunter, Muschelkalk, and Keuper of the German area (é.g. in the hills about Jena, in the Ramsberg and Horselberg on the north side of Thiiringen, and in the valley of the Upper Neckar) will not, I think, be prepared to deny that such a partial equivalency may exist. But when all this is admitted, it is of high importance not to forget the great attenuation of the Muschelkalk and its gradual assumption of a more arenaceous character in the direction of the British area *, It would not be right to overlook the fact that there is much less clearness of definition (stratigraphically) between the Bunter and Keuper of the Devon area than there is between the same two formations in those parts of the Midlands (e. g. about Nottingham) where the Upper Bunter is wholly, or for the most part, wanting. When this is taken into account along with the fact of the unusually calcareous nature of the 150 feet or so of strata above the Lower Keuper sandstones, and with the further fact that many of the limestones of the Muschelkalk contain more or less clay (Credner, Elem. der Geol. p. 497), it does not seem unreasonable to recognize a possible homotaxial equivalency between this group of beds and the Muschelkalk. The suggestion of Mr. J. H. Blake, with reference to another portion of this region which Mr. Ussher has quoted 7, is therefore probably deserving of more consideration than he seems willing to allow. VI. I stated four years ago (Quart. Journ. Geol. Soc., August 1884), after my work in Central Germany, with reference to the Dyas and Trias of Central Europe, that “ not only is there a strati- graphical break, but a marked petrological contrast between the two groups” (p. 396); and, again, ‘‘ The direct relation of the Rothlie- gendes to the character of the adjacent (older) land, which is so marked throughout that formation, and is generally wanting in the formations of the Trias, serves to establish a general broad physical distinction between the two groups of strata, as they are developed in Central Europe” (pp. 397, 398). These statements (mutates mutandis) I consider applicable to the Devon Red Rock Series. The great breccia-marl series consists of the roughly assorted direct products of atmospheric waste and degra~ dation of the Devon paleozoic land, the true Trias of the region being derived partly from these older sediments, and partly com- posed of materials brought into the basin from other areas, owing to some of those changes in physiography of which the Post-Car- boniferous rocks contain such plain records over great parts of the European area. Some remarks of Mr. Ussher himself (Quart. Journ. Geol. Soc. yol. xxxil. pp. 393, 394) show that the difficulties of grouping the * Vide Geol. Mag. dec. ii. vol. ix. p. 276; also Quart. Journ. Geol. Soc. August 1884, p. 401. t Loc. cit. p. 380. 162 REY. A. IRVING ON THE RED-ROCK whole Red Rock series of Devon in the Triassic System were not altogether unperceived by him; and I have little doubt that on further consideration he will be led to suspect, as Sir A. Ramsay was inclined to do (Joc. cit. p. 394), that the Lower Breccia-series may be of Permian age. We certainly are ‘‘at a loss to account for them,” gué members of the Trias, as Mr. Ussher saw, from their absence in the Somerset area, and, as he has shown in a subsequent paper (Quart. Journ. Geol. Soc. vol. xxxv. pp. 240 @ seg.), in Normandy, where the marginal conditions of the Triassic basin proper of the south-west seem to be recorded. As the Thiringen conglomerates are the land- and shore-deposits accumulated from the degradation-products of the adjacent paleeozoic land; as the great Permian breccias of the west of England are related to the older land further to the west; as (to my mind at least) the so-called basement-beds of the Carboniferous series of Northumberland are but the still older local degradation-products of the old Cheviot mountain-island; and as, lastly, the great conglo- meratic Nagelfluh of the northern Alps (e.g. of the Rigi) shows the clearest evidence of direct derivation, by subaérial waste and the transporting-agency of mountain streams, from the highlands ex- posed by the great elevation which followed the period of the Nummulitic Limestone, the terrestrial conditions under which they were accumulated being shown (in some cases) by the inclusion in them of seams of coal; so, it appears, in the Devon area a record of similar physical conditions may be recognized as marking the Post-Carboniferous period, with which the palzeozoie history of the globe terminated. Then as to the deep-red marls, which in this paper are assigned to the Permian, these bear a relation to the breccia-series remarkably similar in some respects to that which the Léss bears to the older and coarser detritus of the valleys of the Danube, the Rhine, and other rivers of Central Europe. Recent investigations by Dr. Jentsch and other observers quoted by von Hauer, in his masterly work ‘ Die Geologie’ (pp. 706-707), have led to the rejection of Richthofen’s theory as to the eolian origin of the European Léss, without denying its application to that of Central Asia. The marls, with which we are here concerned, are not supposed to be a Permian normal Léss. They agree with it petrographically in the extreme fineness of their material (a grain of 4 millim. in diameter having never been found in the true Loss), in their homogeneity, and in the general want of definite stratification; but they differ from it in the large proportion of argillaceous material they contain, the Loss being essentially an extremely fine sand. But on the lower slopes of the Carpathians, contiguous to the trachytic regions of these mountains, there is a lower member of the Liss, known to the Austrian geologists under the vernacular name of “ Nyirok,” a “for the most part reddish, tough, plastic clay, which contains no trace of organic remains, and is always found at higher elevations on the mountain-slopes than the true Loss.” This j is considered by Szabo, who has most fully SERIES OF THE DEVON COAST-SECTION. 163 investigated it, to be “ the final product of the weathering of different trachytic rocks, and to be essentially related to laterite.” Wolf distinguishes in Northern Hungary the diluvial marginal deposits of the mountains from the contemporaneous deposits formed in aqueous basins. The former he describes in ascending order as breccias (Schétter), Nyirok, and Loss—the latter as drift-clay, drift-sand, and Léss-sand. Stur, again, draws a distinction between the ‘“‘moun- tain-liéss” and the “ valley-léss,” the latter containing freshwater molluscan remains *. By comparative reasoning it is not difficult to assign a similar terrestrial origin to the Permian Marls; and this is a sufficient explanation of their entirely unfossiliferous character. The siliceous rocks of the ancient mountain-system, of which the paleozoic land of Devon, Cornwall, and Brittany are the remains, would furnish by their subaérial destruction the materials for both the breccias and the marls, the intrusion of the Dartmoor granite massif being in all probability connected with the great upheaval, which would give us both the supply of materials and the conditions for rapid disintegration and degradation of the mountain-land of the south-west which our hypothesis requires. The intensely ferruginous character also of the breccias, sands, and marls alike (the state of the irony investment indicating con- temporaneous precipitation by oxidation) points indirectly to immediate Post-Carboniferous times, for the extensive waste of vegetation which would be required to furnish the natural solvents which produced the solutions from which precipitation was effected. Discussion. The Presrprent pointed out the interest attaching to the question. The absence of Prof. Hull and Mr. Ussher was to be regretted. Mr. Suita Woopwarp called attention to a supposed spine figured by Mr. Metcalfe in the last contribution to the present subject, published in the Society’s Journal (vol. xl. p. 260). Prof. Huxley’s recent researches upon Triassic Rhynchocephalians enabled this fossil to be determined as a portion of the premaxilla of Hypero- dapedon. _* See also Senft’s description of the formation (Bildungsmassen) of the Roth- liegendes of North-western Thiringen, ‘Gaea, Flora und Fauna der Umgegend Eisenachs,’ pp. 29, 30. 164 REY. A. IRVING ON THE STRATIGRAPHY 15. Supprementary Notss on the StraticRapHy of the Bagsnor Beps of the Lonpon Bastin. By the Rev. A. Irvine, B.Se. (Lond.), B,A., F.G.S., Senior Science Master in Wellington College. (Read January 11, 1888.) In this paper it is intended to lay before the Society the results of additional work in this Formation done during the year 1887. It deals with the succession of the beds all along the northern margin of the district, from Farley Hill near Reading to Englefield Green, and with the development of the formation in the more westerly portion of the area (basin of the Kennet). Parr I, In this part of the paper I shall attempt to show from the description of numerous sections that the inference as to marginal conditions in my last paper is found to hold all along the northern flank of the district. In the recent discussion of this subject some ambiguity has crept into the use of the term “ Middle Bagshot.” For my part I have, as I believe, consistently used the term throughout with the exact connotation which I gave to it in the year 1883*, and in the Quarterly Journal of the year 1885 (vol. xl. p. 494). In the Wellington-College section it is seen to include beds of the horizons Nos. 3-10; and whenever I have found a complexus of beds answering in general physical character to these, I have assigned them to the Middle Stage without taking the empirical consideration of mere thickness into account; since in none of the deep-well sections of the interior of the district have we anything approaching to a recurrence of such a series in either the Upper or Lower stages. Norra Frank or EKAstHAMPstTEAD PLAIN AND CHoBHAM RiIDGEs. Referring now to fig. 1 and section E of my last paper T, I proceed to consider a series of sections in which we can recognize (wholly * Proc. Geol. Assoc. vol. viii. pp. 144, 146. On this point I am, I believe, quite in harmony with the Survey, and with Prof. Prestwich (see Quart. Journ. Geol. Soc. vol. xliv. ‘On the Correlation of the Horene Strata ”). t During this winter the basement-line of the beds Nos. 9 and 10, with fine whitish quartz sands (No. 11), current-bedded below, has been exposed to open day in a sand-pit 470 yards east of the new Wokingham road, and 120 yards north of Nine-mile Ride, at 230'O.D. This is found, when scaled, to be in perfect stratigraphical alignment with the altitudes given for that horizon in the table on p. 384 (Quart. Journ. Geol. Soc. vol. xlii.). In the clay-pit further to the east the dark grey sandy shales (of which about 6 ft. are exposed in the sand-pit just mentioned) are reached beneath 7 ft. of the “mild clay” (with ferruginous concretions), a very good brick-material, over which there lies 6 ft. ofdrift, consisting of contorted sands and pebbly gravel. Taking into account the altitude of the base of No. 10 (230' O.D.), the depth of several wells, and the fall of the ground until the London Clay crops out, the 40 ft. obtained by scaling appears to be an outside limit of the thickness of the quartz-sand series (Nos. 11 and 12) as compared with the 92 ft. of them in the well-section at Wellington College. OF THE BAGSHOT BEDS OF THE LONDON BASIN. 165 or in part) the beds of the Middle Group. These sections will be found to lie almost in a straight line (nearly parallel to the general strike) with the outcrop of these beds three-quarters of a mile north of Wellington College (section E). Their outcrop on the northern flank of Ceesar’s Camp is half a mile north of this line, and will be noticed in its proper place. Section K *. South side of Bull-Brook, near Red Lodge. a. Pebble-bed in situ, seen in the ditch near the corner of South Hill Park (800'0.D.) No. 3. 6. Loam and stiff clay, passing down into MRCON CATE SANT os... .is6 75005 saa scmncne sy Nos. 4 and 5. BASRCU on sweeten cigace ssene gapiavid mans No. 6. d. Green earthy sands and loams ............ Nos. 7 and 8. e. Clay and loamy ferruginous sand (250'0.D.) Nos. 9 and 10. am ame Quartz Said 3iiscel)2 Si8sivossde ewes vous No: 11% Bed d apparently thins out entirely in the hill, on the north flank of which (N.E. of South Hill Park) only the clays appear to crop out. The altitudes give us atotal thickness of about 50 feet for the group of beds which, on comparative lithological grounds, we can assign with a pretty high degree of certainty to the Middle Group, though the section is not sufficiently open to give us the several thicknesses of the individual beds. The hill near the Deer Park, with a plentiful Weneaae of flint pebbles on its summit, owes its fine timber-bearing capacity to the clays of horizons Nos. 4 and 5, which are powerfully developed here and in the section last and next to be described. There is a good exposure of the Lower Sands, with thin seams of pipe-clay, in a sand-pit at the northern foot of the Deer Park hill; and on the south side of this pit the base of the Middle Group is seen, overlain ‘by from 1 to 2 feet of the drift of the hill-slope (mixture of pebbles and reconstructed clay). Section L. Mr. T. Lawrence's Brick-field, Swrnley. a. Upper Sands of Tower Hill (about 60’) with a good fresh exposure of 20! in a new sand-pit (base 300’ O.D.). 6. Loamy clay (a much-prized brick- material), passing down into a strong + Nos. 4 and 5. laminated clay (12' to 14’) ............ c. Dark-green earthy sand full of flint ebbles at the top ; proved beneath } a trial-holes, eal cropping out at Rios) Givic the north end of the brickfield......... d. Mixed clay and sand bed, exposed in a pit close to the tramway (base about + Nos. 9 and 10. AGL) POO 9 8) PAPAS Nee ree Ba Aro Sor : e. Fine quartz sand in the valley ......... Nos. 11 and 12. * It is convenient to make the sections of this paper form a continuous series with those of my last paper (Quart. Journ. Geol. Soe. vol. xliii. August 1887). All the numerical references to the sectional order of the beds are (as i : the last paper) to the section on p. 494 of vol. xli. of the Quart. Journ. Geol. Soc. 166 REY. A. IRVING ON THE STRATIGRAPHY Section M. Brick-pit in Hagthorn Hill, Ascot *. feet. a. Clayey drift-material of the hill-slope ............ 2 6. Laminated clay-and-sand bed with irony concre- LGHS ( ING.) Sone dose eds can odp euch sae ¢. Laminated purplish clay with subordinated layers of greensand (No. 7) ...2...5.25:-.seeneeshe 14 [On the east side of the pit c thickens to 4 feet and becomes a normal green earthy sand. | d,. Laminated layers of purplish clay with very Little sands 2.ct wcss:s3ey> hen snes specaee aoe d,. Grey and green sand with subordinated layers Saat purplish Clay <0... c.-<<< pea e= saa ore eee 2 b. Coarse sands with seams of strong grey clay, marked by very pronounced current-bedding with a nor-+ 6 therly false ip of nearly 3°, . jc-00~2- 200s ene ¢. Mild clay (brick material), more sandy below, strongly laminated, with no appreciable dip in good sec- } 20 tions at right angles (215'-235', O.D.) .............. d, Grey-green dirty quartz-sand (proved in 2 wells)...... 6 Total exposure in pits and well-sections ......... 34 The plentiful supply of water in the wells here points to the probable presence of London Clay at no great depth. The car- bonaceous character of the under strata (d) is confirmed by the character of the water, its action on iron{, and analysis in my laboratory. In a sand-pit a little way to the north, in the wood, * Compare Section M, where a similar lateral transition is noted. _t I doubt this being an Hocene deposit without excavating further into the hill. ¢ Cf. Geol. Mag. for September 1883 and January 1885; papers by the author on “‘ Water Supply.” OF THE BAGSHOT BEDS OF THE LONDON BASIN. 173 these sands are seen as clean fine quartz-sand, finely current- bedded, and overlain by the irony loam which often occurs at the base of No. 10, from the admixture of clay material with the sands next below. No. 10 can be traced in ditch-sections a good way to the west towards Longmoor, an extensive lake-basin dug partly in London Clay, just below the 200-foot contour. Near this a well at a higher level gave the following :— Section R. Well at Longmoor, Finchampstead. feet. REVEL TING, cop oc cnt coscngscqneatcdgneursaascacaresss cs 1 b. Soft loamy particoloured clay (laminated), ‘“ ed 3 (= No. 10) that dug at California, but not quite so strong ” a erie PEM USOR ESAT, |. silnigsisiida's Soin awaloaitn ecsiawssane nes dee arose 12(= No, Et), 16 Bed No. 10 is seen in a road-cutting on Nine-mile Ride, above the 200-foot contour, three-quarters of a mile west of California ; and at another three-quarters of a mile west we come to the end of Nine-mile Ride, where London Clay is dug at 185’ O.D. Western Spur of The Ridges. (The Church Hill.)\—As this hill presents some rather puzzling points of structure, I may be excused for going more into details here. 1. By the levels of the new six-inch Map of the Ordnance Survey *, the highest point of this hill is 330 feet above O.D. The Upper Sands which cap this hill appear to be a continuation of those of The Ridges, not an outlier of them, as mapped by the Geological Survey. 2. A pebble-bed (2 feet thick) at the base of these sands is exposed, at 300’ O.D., at the first turn of the road behind the White Horse Inn and north of the church. It was proved (13 foot thick) at 280! O.D., 500 yards south-east of this point, by excavations made for me in the roadside, giving a dip 8.E. of 1 in 717, or rather less than 1°. In both cases the pebbles are imbedded in clay, and the underlying bed is clay. In The Ridges the clay of No. 5 seems generally to thicken and cut out the loamy sands of bed No. 4 of the College sections. 3. The lane turns sharply north of west from the above-men- tioneds point for 120 yards and descends 20 feet (as determined by levelling) to the small alder-swamp, fed by springs evidently from the base of the Upper Sands. This gives a dip of about 1 in 174 (2. ¢. from 3° to 4°) in this direction. 4. From this point the lane runs due west on these clays along the hill-flank for nearly 300 yards (showing absence of any * The discovery of a discrepancy of some 20 feet in the levels around the crest of this hill as they are given on the older and the newer six-inch maps has necessitated the re-writing of this portion of the paper after communica- tion with the Director of the Ordnance Survey, whose courtesy I have the pleasure of acknowledging here. t Correcting this for the true dip, presumably towards the Blackwater, we get about | in 50, or rather more than 1°. 174 REV. A. IRVING ON THE STRATIGRAPHY general dip in this direction), when we come to Section S (see below); but at the white gate an occupation-road strikes almost due north down the steep flank of the hill, evidently crossmg the unexposed green earthy beds of Section S, since, at a distance of 275 yards, by the map, and at an altitude of 238! O.D. by level- ling, the clays of the California type, referred to Nos. 9 and 10, crop out, and these can be traced a good distance along a clean ditch to the north. They are seen again in the lower part of the lane leading east to Warren Lodge; and they are well ex- posed in the cutting on the Nine-mile Ride (referred to above, p. 173), 300 yards further to the north, with their base exposed in a ditch-section at 207' O.D., below which the fine quartz- sands (No. 11) crop out plainly enough. I draw particular atten- tion to the approximate agreement of levels of the clays which crop out beneath the green-earth series on the north flank of this western spur of the hills with those of the same clays in the California clay-pits (Section Q). In considering the above facts, we have to choose between three possible explanations of the altitude (300! O.D.) of the pebble-bed at the corner of the lane north of the church. Hither (1) the clays of the horizon, No. 5, are suddenly developed to a thickness of from 30 to 40 feet; or (2) a clay witha strong pebble- bed occurs 20 feet or more above the base of the Upper Sands ; or (3) there is a strong local northerly dip on the north flank of this hill. Opinions may differ: I prefer the third explanation as most probable. Such a local feature might easily result from some post-Eocene faulting in the Secondary Rocks below and a consequent flexure of the more yielding Kocene beds. Assuming the true dip here to be north, I have estimated, from approxi- mate data, a dip of 1 in 6°6, or nearly 9°, in the upper hill-flank, the dip diminishing as we descend the hill. Section 8. Jn lane north of Finchampstead Church. a. Strong clay, distinctly laminated at the base ......... 3 (No. 5). [Thin layer of bog-iron-ore. | b. Green earthy sands, laminated purplish seams of clay, and below these strong loamy sands, with a much green sand in pipes ad layers, as in bed f 183 (Nos. 7&8). Sechion P. .. <..i.2..755- de, eee Bee eee eee : c. Clays and loams * (more clayey in upper part)...... ? (Nos. 9 & 10). 30 feet or more. The lane trends from this point nearly due north to Nine-mile Ride, within a quarter of a mile of the open pit in London Clay mentioned above. Taking into account the depth of the water- bearing line in the wells in the neighbourhood, and the altitudes of the respective outcrops of the Lower Sands (No. 11) and of the London Clay, the sands below No. 10 cannot be here much more * These, it will be observed, crop out on the same level as at 300 yards to the east, and as at California, nearly 1 mile to the east. OF THE BAGSHOT BEDS OF THE LONDON BASIN, 175 than about 30 feet thick, as compared with the 92 feet of the Col- lege-Well Section, a marked instance of attenuation. Obyicusly enough the determination of this horizon is very impor- tant, so far as concerns the actual thickness of the lower quartz-sand series (Nos. 11 and 12) on the margin of the area; and, as 1 showed in my former paper, the lithological character of bed No. 10 varies sufficiently within certain not very wide limits to introduce an ele- ment of uncertainty, if inferences were drawn from a few discon- nected and small exposures taken at random. ‘But I think it must also be equally obvious to any one who peruses carefully this and my former paper, that the lithological evidence is strengthened and controlled by the stratigraphical, the beds recognized as on the horizons of Nos. 9 and 10 of the typical well-section being found either cropping out from beneath the green-earth series or in direct stratigraphical alignment with beds that do thus visibly crop out from beneath them. Section 8 will be seen to be on the same contour with Section P at Wick Hill. Finchampstead Rectory, at 250' O.D., is on beds which crop out also on the same contour from beneath the Upper Sands, which cap the Church Hill, and the well here (50 feet deep) showed that the green beds become very feeble also in that direction, very little green sand having been brought up in the digging of it, within the lifetime of the present Rector *. At the foot of this hill beds Nos. 9 and 10 crop out, and they can be traced all along the road to near Eversley Bridge. There are many exposures of these in small sections ; they are cut through by a small transverse valley of erosion between the Rectory and Bannister’s Farm, which stands on an outlier of them, and some fifteen years ago they were worked for bricks near the lower road, at about the 200-foot contour. Their passage down into the dirty fine quartz-sands of No. 11 is well shown in some rather large ditch-sections in the fields below the Curate’s house, only a few feet above the Blackwater, and above the place where the London Clay is marked on the Survey Map. On the south flank of The Ridges the clays of No. 5 crop out in the road-cutting below Sunnyside, and continue down to Hast Court. The green earthy sands (Nos. 7 & 8) crop out next below, and below these the clays and loams (Nos. 9 & 10) are exposed in many small sections about the village. In 1886 a new well was dug at the village school by John Walter, Esq., of Bearwood, who kindly drew my attention to it. Section T. Well at Village School, Finchampstead (210' O.D.). feet. a. Laminated hard clayey sand ............seeeeeeee 10); €No. 10). b. Dirty blackish-green quartz-sand, with pyrites. 5 (No. 11) c. The same dirty sand mixed with black clay ... 5 i % Potalnt.io 20 _ * The assignment of the beds in the Rectory Hill to the Upper Bagshot (Geol. Mag., January 1885) was a mistake based on the reported non-appearance of green sands in the well-section. 176 REY. A. IRVING ON THE STRATIGRAPHY The apparently excessive thickness of the Middle Group on this hill-side is explained by a dip towards the Blackwater Valley, of which evidence is given above. Bearwood Hills.—In addition to the facts already described (Geol. Mag. dec. ii. vol. iv. pp. 111 ef seg.) the following require con- sideration. (a) The flank of the hill is very much obscured by a vast amount of débris (mixture of sand and pebbles) from the higher beds, the phenomena presented at St. Anne’s Hill, Chertsey *, being here repeated. There are several old, overgrown gravel-pits, in which these materials have been worked in former years. (6) In the latter part of the summer Mr. Walter was good enough to have a second and deeper square pit dug through the pebble-bed. On descending the pit by a ladder, I made the following observations and measurements, while the section was fresh and not obscured by rain-wash. Section U. Pit on the flank of Barkham Hill (260' 0.D.). ft. in. a. Drift (coarse sand and flint fragments) ............... Pel U:* Loamny Sands 2.0. 525.405. ee ae See ee eee Bute c. Pebble-bed in greenish and brown sand............... 5 0 d.. Coarse, brown OAM . Palas | ‘ (EL 2 y [ Bint ge: ba ‘ ie Nasal hig kent ‘ *% 7 ~ x f . : ae colin f e F A . AND GLYPHASTRHA, DUNCAN (1887). 227 Fig. 11. Another portion of the inner layer, showing small holes in the spaces between the ridges. Enlarged forty diameters. 12. A portion of the exterior, lateral surface of the wall or theca of a corallite of S. Forbesi, showing transverse growth-lines crossing the pseudo-costal spaces, and the longitudinal furrows along the lines of the septa. Hnlarged twenty diameters. 13. Part of a transverse section of the upper portion of a corallite of S. Forbesi, showing the disposition of successive layers of stereo- plasm, with which the interlocular spaces are completely filled. Enlarged twenty diameters. From the type specimen in the British Museum. 14. A longitudinal section of the upper portion of a corallite of S. Forbesi, showing the limitation of the deposit of stereoplasm to the space immediately above the uppermost horizontal dissepi- ments, and the arched lines of deposition of this material within the corallite. Enlarged seven diameters. 15, A single interlocular space in a corallite of S. Forbesi, viewed from beneath, showing the development of the horizontal dissepiment from the bounding walls of the septa, and the sutural lines at the meeting of the membrane. Enlarged fifteen diameters. 16. A transversely fractured corallite of S. sexradiata, viewed from beneath, showing the complete enclosure of the individual inter- locular spaces by the septal laminz. Enlarged sixteen diameters. 17. A calice of S. Forbesi, showing impressed longitudinal grooves in the inner surface of the wall, between the principal septa, for the insertion of the mesenterial muscles. Enlarged six diameters. Discussion. The Prestpent remarked upon the complicated question of nomen- clature which was raised in the case brought before the Society by the Author. The latter part of his paper added valuable informa- tion on the structure of corals, and was a striking instance of the aid that might be afforded by paleontological research to the studies of biologists. Mr. Atrrep Foorp said the drawings in Prof. Duncan’s memoir had been carefully made from the original specimens, and that the existence of a columella in Glyphastrea was distinctly visible, as shown in several of the figures. Mr. Erueriper was well acquainted with the specimens, and called attention to the great difficulty there was in correctly deter- mining their species from the appearances presented. The research relative to the present species was almost unprecedented. Dr. Hinde had taken great pains in unravelling the history of these corals, and his investigation of their microscopic structure was of great im- portance, and would probably lead to valuable results in the future classification of the Coelenterata. Dr. Woopwarp agreed with Dr. Hinde as to the distinctive cha- racters of S. Forbest and S. sexradiata, and complimented him on the clearness of his description. Dr. Hrype, in reply, said he had not questioned the general accu- racy of Mr. Foord’s drawings; but in two instances, in the plate referred to, the figures were admittedly diagrammatic, and the crucial feature in another figure had been exaggerated, no doubt unintentionally on the artist’s part. The speaker considered the use of the microscope essential for the correct determination of coral structure. 228 PROF. W. BOYD DAWKINS ON AILURUS ANGLICUS. 18. On AILURUS ANGLICUS, a new CaRNIvoRE from the Rep Crae. By W. Borp Dawxuns, F.R.S., Professor of Geology and Pale- ontology in Owens College. (Read January 25, 1888.) § 1. Introductory. § 2. Description and Comparison with Alurus fulgens. § 3. Measurements. § 4, Range of Ailurus in Space and in Time. [Puate X.] § 1. Lyrropucrory. In the fine collection of fossils from the Crag of Norfolk and Suffolk, presented to the Museum of the Yorkshire Philosophical Society at York by Dr. Reed, is a battered and water-worn spe- cimen, which is of singular interest, because it carries the range of one of the most restricted of the genera of the Oriental Province far to the west and to the north of its present habitat. It is a small fragment of the right lower jaw, with the last true molar in position, found in the Red Crag of Felixstowe, the rest of the ramus and the angle and articular and coronoid processes being broken away (see figs. 1 and 2). § 2. Description AND CoMPARISON WITH AILURUS FULGENS. After a long and careful study, I find that the lower jaw in ques- tion differs in a marked degree from all the European fossil Car- nivores, and presents no important points of difference when com- pared with the series of jaws of recent Av/urus in the British Museum. The last true molar in the fossil is implanted in the jaw by two fangs, the anterior being the smaller, and supporting the anterior cusps, A and p of figures 1, 2, 3,4. The multicuspid crown is com- posed of three small, obtusely pointed cusps, 4, B, c of figs. 1, 3, and 4, on the outer side, while the inner (figs. 2 and 3) is occupied by the large cusp D and a smaller hind cusp Ff, connected by a line of low tubercles, from which the enamel has been stripped. The outer series of cusps is separated from the inner by a shallow longitudinal groove (fig. 3) traversing the crown nearer the inner than the outer side, and causing the inner cusps to be narrower than the outer. They are also the higher. The crown is also divided by two trans- verse valleys into three lobes (figs. 3, 4), of which the anterior, a, p, is the higher and larger. In all these points the fossil agrees with the living Azlurus (figs. 5, 6, and 7), with the exception that the longitudinal depression is not so strongly marked in the former. Nor are differences of any value to be noted on a comparison of the fossil specimen with the recent teeth cusp by cusp. The antero- outer cusp 4 of figs. 38 and 4 occupies the greater part of the front lobe, and has in front a small talon or tubercular cingulum. In five specimens of living -Azlurus the cusp a is in the same relative posi- tion (figs. 6 and 7), and a tubercular cingulum or slight talon is traceable in four. The accessory cusp 4’ of figs. 3 and 4 is present in ——" ae PROF. W. BOYD DAWKINS ON AILURUS ANGLICUS. 229 the interspace between a and B, in both the fossil and the recent (figs. 6and 7). The cusp 8 of the fossil is obtusely pointed and sepa- rated by a cleft from the third cusp co. Behind this cleft in the fossil is a small accessory cusp B’ (fig. 4), which I have only been able to note aS a mere rudiment in one recent tooth belonging to an Adlurus shot by Mr. B. H. Hodgson in Nepaul. The third cusp, ©, is small and mapped off from the back cusp F by a slight valley. In all these points the fossil agrees with the recent specimens. On the inner side, the front lobe p of fig. 3 is mapped off from a by acleft, and bears a talon infront. In the living A:lurus (fig. 6), the talon has developed into a basal cusp p’. The fractured surface of the tooth (figs. 2 and 3) behind p renders it impossible to compare the inner margin mi- nutely with the recent specimens; enough, however, remains to prove that it is composed of small tubercles running from p to F, like those in Azlurus fulgens (fig. 6,8). The cusps of the fossil are, as a whole, larger, blunter, and less clearly defined from one another than in recent A:luri. On a comparison of the fossil with the recent jaws of =} =f Field Quarry Conglomerate Twl Hill — me ee a A Black Shales conglomerate runs obliquely against the porphyry along a line run- ning 8.W. to N.E., and the edges of the beds are cut off by a perpen- dicular line. Here the conglomerate is said to dip, as at Twt, to E.S.E. Ata disused quarry in a field by Tygwyn is another expo- sure of conglomerate and grit, here dipping at 45° to the 8.S.E., the line of strike leading directly to the Menai Straits, while the por- phyry is seen eight yards away towards the north. The surface of junction, therefore, curves about in a most extra- ordinary manner ; and seeing that the porphyry has the aspect of an intrusive rock, these observations would certainly suggest an intru- sion. Nevertheless they could not have led the Survey to their conclusions, since the line is incorrectly drawn on their map. The alternative hypothesis is a rather complicated group of faults. Other considerations must be brought to bear upon the question before we can decide it. The most important of these is the nature of the Twt-Hill rock. * Quart. Journ. Geol. Soc. vol. xxxv. 1879. ROCKS IN N.W. CAERNARVONSHIRE. Zio Prof. Hughes boldly writes down “ Twt-Hill beds,” and speaks of “the most conspicuous divisional planes suggestive of bedding.” On this I must point out that if a bedded rock could be so metamor- phosed as to produce a quartz-porphyry, the first thing to disap- pear, as such, would be the planes of bedding ; and if there are any such planes to be found in a metamorphic rock, we must look for them, not in the most conspicuous, but in the most obscure sub- divisions of the rock-mass. Prof. Bonney brings the microscope to bear upon the question, and declares he can distinguish between a granite and a granitoid rock. The only points of difference that can be tested are given in a note in Quart. Journ. Geol. Soc. vol. xxxy. p. 306. One is that in a granitoid rock the quartzes and felspars show more irregularity in their outlines, size, and distribution ; and another that an indefinite felsitic matrix may be seen. This latter point is surely more suggestive of a porphyry, and there is little use in discussing the former, since it does not cover half the structures found in rocks of the Twt-Hill type. In various parts they put on various aspects, but it is impossible to trace the changes; they come in sporadically and die out gradually, after the manner of a granitic intrusive mass, varying its character according to its circumstances of cooling, and so merging into a quartz- porphyry. From the great similarity of the structures to those in undoubtedly intrusive masses, I conclude that the Twt-Hill rock must be of an intrusive character. But that it was intrusive into the conglomerate is another matter altogether. True, the edge of the conglomerate looks burnt in the Twt-Hill field-quarry, but under the microscope this is shown to be due only to infiltration of ferric oxide along the junction. Again, the lowest portion of the conglomerate here is very remarkable. Its quartz-fragments are quite angular, and even irregular; they are sometimes complex, as if they had come from such a rock as the neighbouring granite, and then show signs of very severe pressure. There are fragments also of quartz-schist* and other altered rocks, while the matrix is composed of secondary quartz and sericite. The rock would cer- tainly appear to be derived from others in the immediate neigh- bourhood, one of which would have to be practically identical with the granite here exposed. We must also consider what is the true age of the conglomerate. It is always spoken of as the Cambrian conglomerate, though at Twt-Hill field-quarry the succeeding rocks are scarcely exposed ; but the same conglomerate is, or was, seen, by the new church, and not fifty yards away, down the sloping street, black shales are seen (fig. 4), and these are continuous for the rest of the distance to the point, quite close at hand, where Mr. Marr found Arenig fossils *. Any fault supposed to lie between Arenigs and Cambrians here is entirely hypothetical, and when the beds are traced north is found to be practically impossible. Hence it is that I conclude that this conglomerate cannot be of Cambrian, but must be of Arenig age. * Callaway, Geol. Mag. 1881. T Quart. Journ. Geol. Soc. vol. xxxii. 1876. 276 PROF. J. F. BLAKE ON THE CAMBRIAN So it is coloured by the Survey, and every consideration tends to prove them right. It is at the base of the Arenig that palzonto- logists have suggested a break in the strata. It is the base of the Arenig that contains the overlapping conglomerates in Anglesey and Ireland*, and this is the lowest series that is most widely spread in Europet. Hence it is nothing extraordinary that Arenig rocks should here have a conglomerate at their base, and should be asso- ciated with the porphyry (all Cambrian rocks being absent), and so it is that we find here the key to the interpretation of the district. My explanation, therefore, of the rocks near Caernaryon is as follows:—The granite is intrusive into older rocks than the Arenig, now hidden from view, though perhaps their fragments may be recognized in the conglomerate. This conglomerate once rested on the surface of these rocks, perhaps not far from the curved and bay-like line which now forms the junction with the granite; but in the upheavals of the district the union has been broken, and slippings have taken place, producing faults. Passing now to the north-east of Caernarvon, the undulations of this base-line of the Arenig are found to be very considerable. They are traced on the Map, fig. 1, p. 272. The conglomerate almost cuts out the porphyry behind Ty-coch, where it actually dips towards it. It then passes rapidly eastward, to be found near the river-side south of Pengelli. It then apparently curves back till it runs nearly north to Careg Goch, and all the fields to the east are covered with the Ordovician shale. Then we come tothe great grit-beds south-south- east of Tan-y-maes, and the conglomerate, which must be almost welded to the porphyry at the cottages, and certainly overlies it. East of this we find it thrown out to the farm at Wern, where the junction with the shaleis seen. It must then be thrown east again, to curve round the farm at Cefn and undulate along the road to Gorsbach. Here we come upon a different set of underlying beds, and the conglomerate gets finer and gradually degenerates into a grit—we find this grit in the valley to the east of Gorsbach, to the south-west of Ty-mawr, and further on in a quarry near the cross roads on the western side. JI have not traced it for the next 14 mile to the north, but find it again at Caer-hun, in quarries to the east of the road, again on the west of Pen-yr-allt, and on the east of Cae Seri, then cutting the road by the “i” in ‘ Bryniau,” and after crossing this it rises into a good escarpment of massive grit in a wood running parallel to the road which branches off to the right, After the crossing of the next lane, and so on to the Holy- head road, very little sign of grit can be found—it may be concealed or have died out, or there may be a slight fault here. In tracing this line it will be perceived that the portion on the Bangor sheet is very accurately laid down on the map, but the part on the Caer- narvon sheet has not previously been surveyed with precision. It. will be seen also that the conglomerate and grit base of the series is much thicker south of Gorsbach, where it is in contact with the * See Ramsay, Mem. Geol. Surv. vol. iii. Tt See Hicks, Quart. Journ. Geol. Soe. vol. xxxi. 1875. ROCKS IN N.W. CAERNARVUNSHIRE. Qe igneous rock, than to the north, where it abuts against the sedi- mentary, and is thickest in the bays of the curve, probably indicating that this curve is near the true line of deposition. The most critical part of this line is at Gorsbach, where an older conglomerate comes in, which we are only prevented from mistaking for the Arenig by carefully tracing the line on both sides and comparing the character of the rock step by step, as is done below. We have thus marked off for our study a definite area of rocks, of which as yet we only know that they are Pre-Arenig, This area We must now examine. The southern portion, as marked off by Prof. Bonney *, is cer- tainly distinct from the rest, but it loses its character as we pass northwards. Thus, at Ty-coch the section shows a coarse-crys- talled granite, only cracked and disturbed. As we pass into the so-called ‘* Crug beds” of Prof. Hughes, 7. e. at Crug Farm, we find a beautiful radiating granophyr, much cracked and filled with quartz. In the ravine west of Tan-y-maes the rock is porphyritic, with idiomorphic quartz-crystals, and a matrix partly micropeg- matitic, partly mosaic; and at the extreme tongue by Tafarn-y- grisiau only the latter matrix is left, and the whole is very dirty. All these have a family likeness, and may well be considered parts of the same intrusive mass. In the side of the main road south of Dinorwic, between the two branches of the road which goes over the hill, is seen the rock into which we may suppose this porphyry intrudes. It has a dirty unstratified aspect, like an indurated mud, but really consists of irregular fragments of quartz, in a quartzose but dusty matrix, much lined and infiltrated. Immediately we cross Prof. Bonney’s line and pass to the east over Dinorwic, the change in the character of the rock, as seen under the microscope, is marvellous and complete. Whether close above Dinorwic or at Pant-yr-fallan-fach, on the eastern slope of the kills, or in the valley to the east, or still further east near Tan-yr-allt, every rock is a fresh quartz-porphyry, whose ground-mass is crowded with streaming microliths, exhibiting fluxion-structure to perfection. The contrast between these and the Caernarvon group of rocks is all the more marked from the latter being in their most altered state and the former in their freshest, where they are found side by side. The subdivision, therefore, of the great mass of quartz-porphyry in this district into two distinct parts, of different ages, we owe entirely to the microscopic researches of Prof. Bonney. I do not think that these felsites all belong to one outburst, whether as an intrusion or a flow: first, because there are varieties of the porphyry, some containing only scattered quartzes, others crowded with quartz and felspar, and some, as in the ravine near the “d” of the Tyn-y-coed, with a spherulitic matrix. Moreover, as pointed out by Prof. Hughes, there are breccia-beds, though I have only found one, running north-eastwards by Tan-yr-allt. Probably the most important point to determine with regard to this porphyry is the nature and cause of the long tongue which is * Quart. Journ. Geol. Soc. vol. xxxy. 1879. 278 PROF. J. F. BLAKE ON THE CAMBRIAN drawn on the Survey Map running up from Pen-y-swintan to Friddod (see Map, fig. 1), as its distribution would suggest intrusion. This tongue is not correctly laid down in the map either of Prof. Bonney or of Prof. Hughes, but is drawn on the Survey Map with considerable accuracy. I think, however, the probability is that it is not intrusive. In the first place the structure of the rock, as obtained at Pen-y- swintan or at the extreme end at Friddod, is not that of a dyke, which such a tongue would practically be, but the matrix shows flow-structure, and it is crowded with crystalline fragments, the rock itself not being much fractured, thus suggesting a faulted original flow. Again, as will be seen by the stratigraphy of the higher beds, the country here must be much broken up by faults, one of which, on its north-western side, might easily bring it to its present position ; and lastly, it is followed = several places on the south-east side by a small conglomerate, some fragments in which, in one specimen at least, are similar in structure to the porphyry. The beds, however, which lie between the porphyry and the Arenig grit are perhaps the most important, at all events in their relation to the rocks of Anglesey. They are divided into two areas by the fault which runs along the Bangor valley; and if we can be certain of them in one area, the stratigraphy of the other becomes more of a geological puzzle than a matter of general interest. Fig. 5.—Plan north of Gorsbach. 7 Mn? 6 \ es > Z oe as TE = S- Ss Fo i DT sAZZ A\ = un SLY ——=s Ti \ =a17} ESZ i a eu Ty mawr EB Oneal ii es amin 1. Felsite. 4, Felsite conglomerate. 7. Breccia. 2. Quartz-felspar grit. 5, 8. Green Bangor Beds. 9. Arenig grit, 3. Grit. 6. Halleflinta. Taking the eastern area, we find the first incoming of these beds just north of Gorsbach, near Llandeiniolen, where the geology is rather complicated. The ground-plan is given in fig. 5*. On the western side of the Arenig grit, which can be traced all along here, we find, next to the porphyry, a coarse quartz-felspar grit, which forms a knob at Fachell, and is scarcely to be distinguished from the porphyry, except under the microscope; next comes a band of grit, and then the dark muddy conglomerate, full of large pebbles of red felsite. Higher still is a thick mass of compact green-banded rock, such as occurs so abundantly at Bangor, and then finer material * The Map, fig. 1, is not quite accurate here. ROCKS IN N.W. CAERNARVONSHIRE. 279 still, with lines curving about almost like a vitreous lava, but actually a hiilleflinta. The beds above are breccias, and finally a green-banded rock again. We seem to have here, in miniature, the whole series as seen further north near Bangor, but this may not be so really. The red felsite-conglomerate, indeed, appears to die out, no trace of it appearing in the fields a little to the north as we walk across the strike of the series. Seen under the microscope, Nos. 2, 5, 6, 7, seem all of the same type, the fragments in the several rocks differing only in size. Most of them are mineral fragments, but there are some characteristic rock fragments of a basaltic type, consisting of long transparent erystals scattered irregularly in a black opaque ground-mass. I know of no rock in this district, except in Anglesey, from which such fragments could be derived. The red felsites in No. 4 are very like those below ; but one fragment I take to be an altered pumice, since it contains long cavities drawn out into fantastic shapes, and lined by a coat of inward-growing crystals; if such is its nature, it no doubt formed the surface of the felsites. Passing north we come to the region so carefully examined by Prof. Bonney. I have, I trust, examined it with equal care, and ean fully confirm the accuracy of his observations, particularly in those points in which he differs from Prof. Hughes. I have traced the quartz-felsite grit by Rhos fawr, Brithdir, round by Wern into the valley, where it curves westward round the edge of the felsite. Then the green laminated beds on the summit of the hills, and the porcellanites by Penhower, as far as the commencement of the Tair- ffynon lane; then the great agglomerates, jasper conglomerates, and grits at Tair-ffynon, and the quarry by the side of the main road, where, however, the dip is turned round, probably in the neighbourhood of the fault; then the finer beds at Perfeddgoed, which include a quantity of purple slate, near Caer-hun and to the north of it; then a bluish breccia at the corner south of Cae Seri, which may be well matched at the poor-house, and another to the north, which may or may not be the same as that at Hendrewen ; and finally the great hialleflintoid mass which, commencing with Mniffordd and Nant Gwtherin, forms the western slopes of Bryniau Bangor. I have nothing to add in this region to the proofs adduced by Prof. Bonney in support of his statements of the succession, which, to those who have examined the ground, should be perfectly con- vineing. (See the Map, fig. 1.) Here, however, we part company. There lies to the north a conglomerate of large stones which, for some reason I have never discovered, has been called by everyone in latter days the basal Cambrian conglomerate. Now the last few of the grits having had a pretty persistent strike of N.N.W., we find in the fields by Nant Gwtherin another coarse grit, its strike still N.N.W. This seems to have been identified with the so-called “Cambrian conglomerate” by Prof. Hughes; but a careful survey will show that this cannot be right, for we can follow this grit for some dis- tance along its strike, and find to the east of it, 7. e. above it, 280 PROF. J. F. BLAKE ON THE CAMBRIAN in the sequence, some more hilleflintoid rock (well shown in a quarry by the roadside), and we must go to the east again to find the conglomerate of large stones in the nearest spot of the adjacent field. This can scarcely be brought about by a fault, since the Arenig is undisturbed ; and moreover the coarse grit does not resemble the conglomerate, but resembles more closely a grit seen where its continuation should be, to the west of the conglomerate on Bryniau Bangor. The great conglomerate appears to die out on the south, as conglomerates do; but we may trace it from a knob at about the “‘n” of Rryniau, in a north-north-west direction, to the west of, and nearly parallel to, the road; and this strike leads exactly to the spot where it is found in the road, as noticed by Prof. Hughes. It is therefore strictly conformable to the underlying beds. It is just near its southern termination, but on the opposite side of the road, that the escarpment of Arenig grit is seen striking N.N.E., in other words making an angle of 45° between the two. There is there- fore no conformity with the overlying beds. Moreover, if the great conglomerate were the base of a new series, the beds above ought to be decidedly different. There are certainly a few purple beds in the road, but so there are far away to the south; but the main mass is difficult to distinguish from the hilleflinta below—so diffi- cult, it appears, that Prof. Bonney, by curving round the conglo- merate, has made beds, which really lie above it, appear to lie below, thereby unconsciously testifying to their identity. I can therefore regard this so-called basal Cambrian conglomerate as nothing else than another and the most remarkable of the series of conglomerates which characterize these ‘‘ Bangor beds.” It is clear, then, that above the porphyry we have an ascending con- formable series of conglomerates, grits, and more or less banded halleflintas, alternating with each other and overlapped uncon- formably along their eastern side by the Arenig grit. I have also carefully examined the country on the western side of the fault, but I am afraid it is more or less labour lost; we learn nothing further as to the succession, and cannot hope to tell whether a rock is conformable or not, especially when, like the great con- glomerate, it changes its strike by more than 45° in the course of its 1 mile run. But I am not in the least certain that this is on the same horizon as the great conglomerate on the other side of the valley. To begin with, the pebbles are not the same, those on the east being far more quartzose; but the rock is most like one of the beds at Tairffynon and the dark conglomerate of Fachell, a corre- lation made by Prof. Hughes. It would require the least number of faults to bring this about, and the beds actually seen below it are similar to those which occur below the Tairffynon conglomerate, while the beds above are more comparable on the two sides of the valley than they would be if we identified it with the conglomerate of Bryniau Bangor. I think the most probable stratigraphy here would be to draw a line of fault with an upthrow on the east, making a very small angle with the main fault, and running from near the “Inn,” opposite Treborth, to beyond the Baths at Garth, ROCKS IN N.W. CAERNARVONSHIRE, 281 thus bounding the felsite on the west, and running through the corner of the road where the great conglomerate changes its strike. A small fault does come out on the shore between the Baths and the Ferry. Thus the general strike of the beds on the east side of this fault would be to the east of north, instead of to the west of north, as on the other side of Bangor valley. But if my view be correct, all this is a matter of little consequence. The puzzle is to account for the very large pebbles of felsite and other volcanic products when the felsite near at hand must have been covered up by earlier de- posits, and there is none other near to choose from, Thus the Pre-Arenig rocks near Bangor form one indivisible series, but what is their age? Are they also Pre-Cambrian? The supposed proof of this has rested on the assumption of a basal Cam- brian conglomerate, and the assumption is not justified. With Prof. Ramsay the only question was between what we now call Upper or Lower Cambrian, 7. e. between “a” and “6,” and he concluded, from a comparison of these rocks with others in Glyn- lifon Park, that they were Cambrian rather than Lingula-flags. Another reason that led him to this conclusion was the similarity of the conglomerates near Bangor to those near Llanberis, which are undoubtedly Cambrian. Any difference between these was ac- counted for by metamorphism. We can, however, dispense with much metamorphism, and yet compare these rocks with Cambrians. There is little to choose, microscopically or otherwise, between some of the rocks near Gorsbach and some near Llyn Padarn, nor between some varieties near Bangor and the rocks in the heart of the Cam- brian near Llandwrog, nor between the grits north of Perfeddgoed and some west of Dinas Dinorwic. The included fragments may be somewhat different, but they are exactly the same type of rock. The great peculiarities of these Bangor beds are their great total thickness without reaching the great workable slates, and the presence of numerous and various conglomerates. They are called volcanic, but they are arranged in beds after the manner of sub- aqueous deposits, and can only be said to be volcanic as having been derived from the denudation of volcanic products. They are, of course, of later date than the volcanic eruption whose remains are seen in the porphyries. Thus their general features attach them to the Cambrian, and their peculiarities are what we might expect at the base of such a series. Is not the cause of any minor dif- ferences from other Cambrian rocks simply that we never see the base of the Cambrian elsewhere in North Wales ? This opens up another question, and forces us to the study of the rocks by Llyn Padarn, since these are supposed to represent the basal Cambrian, and to lie upon a Pre-Cambrian axis. Llyn Padarn and Mcel Tryfaen. The great conglomerates which lie on the east of the masses of porphyry, on either side of Llyn Padarn, are considered by every one to be the base-bed of the Cambrian. According to Prof. Ramsay, as Q.J.G.8. No. 174. u 282 PROF. J. F, BLAKE ON THE CAMBRIAN I understand him, the conglomerates first lay on the hidden land from whose denudation they are derived. Then came an eruption of porphyry, which crept between the two and absorbed into its substance the lower part of the conglomerate. According to Prof. Bonney and Dr. Hicks, the porphyry. was poured out as a lava, and the conglomerate was derived from its denudation. The proofs of this latter view are numerous. First, there are the abundant pebbles of felsite found in the conglomerate, which are certainly like the porphyry below; and it seems unnecessarily going out of the way when Prof. Ramsay says they are like some Bala felsites. Another argument may be derived from the way in which these conglomerates cling to the porphyries all along their range. They are seen in contact on Clegyr and on the south of Llyn Padarn, and though Dr. Hicks supposes there are some schists between them at Moel Tryfaen, his dark porphyritic-looking rock, which comes in the adit next the felsite, has been recognized by Prof. Bonney as the conglomerate itself; and in a small cutting of the slate railway on the west-south-west of the summit of the hill, the conglomerate is actually seen side by side with the felsite, neither passing into it, as supposed by Prof. Ramsay, nor unconformable to it, since there is no bedding in the felsite. Furthermore Prof. Bonney has pointed out the flow-structure inthe porphyry. I may add that, as observed by Prof. Hughes, to the west of Clegyr, and in immediate contact with the conglomerate, there are great masses of agglomerate, and these are repeated in connexion with another flow at a domes level, having a nose of breccia at its termination near Llys Dinorwic. We can scarcely, therefore, hesitate to admit, in the light of such observations, that these are really, practically at least, subaerial flows, and that the conglomerates have been derived in part from their denudation. But the next question is, what is the age of the porphyry? in other words, what did it flow upon? Prof. Bonney and Dr. Hicks do not seem to have inquired into this. They take it to be Pre- Cambrian, and are apparently hopeless of finding any base or floor for it. If such a floor is to be found, it must be on the western side, since the conglomerate lies to the east; but here there is a great mass of Cambrian strata, and it 1s the relation of the felsite to these which we must examine. In some parts the junction is marked as a fault, but in the rest it is not. On examining the ground we soon find that the western boundary is for the greater part hypothetical, as it is confessed to be in the explanatory memoir*. The ground is covered by drift, and no junction can generally be seen. The only exception to this is on the north-east side of the river Rothell, where the drift is absent. This, then, is the crucial spot. If there is a fault here, our question must remain unanswered ; but if there is not, and the felsite is older than this western Cambrian, as well as the eastern conglomerate, then the beds on the western margin must turn up and be found lying upon, or dipping away from it, and so * Mem. Geol. Surv. vol. iii. 1866. ROCKS IN N.W. CAERNARVONSHIRE. 283 Prof. Ramsay and, after him, Dr. Hicks draw the section, though they introduce a fault as well. But is this so? On the north-west side of the felsite there is a low alluvial valley, about 200 yards wide. On the opposite side, quite close to the valley, there are exposures of rock; but it is not a con- glomerate, but ordinary fine slates, with vertical cleavage, but dip- ping towards the felsite at an angle of about 20°. This is suggestive, but affords no certain datum; our only chance is on the edge of the felsite itself. It is ill founding a determination on one section, but in this case a single proof could scarcely be more decisive. On the west side of the road from the bridge to Bryn Efail, and exactly on the letter “ E” of that word in the map, there is a quarry in the felsite, which here shows a precipitous face towards the valley. The plan of this quarry is shown in fig. 6. The edge of the felsite Fig. 6.—Plan of Quarry at Bryn Efail. 1. Porphyry. 2. Slate. 3. Grit. 4. Greenstone. is ragged and irregular, but perfectly clean. In the centre of the quarry it runs against a boss of greenstone, and cuts it into pro- montories and twisting tongues. At the sides of this the junction is, for the most part, with a vertical bed of slate, which is followed on the west by a bed of grit, with which also the felsite occasionally comes in contact. The strike of these beds is nearly parallel to that of the Cambrians just noticed. The felsite is so welded with the slate that it is easy to obtain a junction specimen, and two such have been examined. In one the line of junction is perfectly: straight. The felsite shows the quartz-crystals somewhat broken and exhibiting signs of pressure, and the ground-mass is crypto-crystal- Ime and of varying coarseness; the whole is singularly like the band at the edge of the Twt-Hill mass in the Field-quarry, and I have no doubt they were formed under similar circumstances. Towards the junction both felsite and slate are infused with ferric oxide, which produces a coloured band in the slate of about 2 inch in width. In the slate are developed abundant crystals of chias- tolite, to judge from their long shape, their rhombic cross-section, and their dark line down the centre, and their being broken up into an infinitude of small low-polarizing crystals, which refuse to extin- guish as a whole. ‘There are also anumber of small high-polarizing crystals which I cannot identify. In other words, the slate is altered by contact with the felsite. The same phenomena are v2 284 PROF, J. F. BLAKE ON THE CAMBRIAN observable in the other specimen, where the felsite runs in veins into the slate. In the road outside the quarry, beneath some cottages, there are again phenomena which point to the same conclusion (see fig. 7). In the mass of rock, on which a brick wall is built, are seen the felsite and baked slate renning into each other in a way which proves intrusion, in this case, of course, on the part of the felsite. Fig. 7.—Section in Road near Bryn Efail. PEEP ROA TE eo Te ee on SE Oe, | + ae I /; Mn: 1. Porphyry. 2. Baked Slate. . peel This spot is so important in its teaching as to the age of the felsite, that I can only suppose that it has escaped the attention of previous observers. It provides a crucial test, and thus a decisive proof, that this great flow of acid lava was, like the 99 per cent. of which Prof. Sedgwick speaks*, contemporaneous with the Cambrian rocks amongst which it is found. The Cambrians to the west are of earlier, and those to the east of later date than this. The question being thus apparently settled, it is necessary to see how this con- clusion fits with other facts that may be observed in the neighbour- hood. In the first place, the conglomerates ought to contain not only felsites, but also fragments of the Cambrian rocks to the west. At Clegyr, where the top of the felsite is an agglomerate of felsitic frag- ments (and nothing would be easier than to round them into pebbles), the conglomerate is mostly, though not entirely, made of such stones. But at Moel Tryfaen, where the top of the felsite, for some reason, is clean, the majority areslate. On this, Prof. Ramsay says7, ‘“ the pebbles of purple slate resemble those of the very strata amidst which they are found; the quartz-rock and jaspers resemble some of the metamorphic rocks of Anglesey.” It is remarkable that Dr. Hickst, who thinks this conglomerate is derived from Pre- Cambrian rocks alone, omits all mention of the purple slates, and enumerates only ‘‘ quartz, quartz-felsites, porphyritic rocks, and - schists.” Now these fragments of slate are large and scarcely * Quart. Journ. Geol. Soc. vol. iii. 1847. + Ibid. vol. xxxiv. 1878. t Ibid. vol ix. 1853. ROCKS IN N.W. CAERNARVONSHIRE. 985 rounded, and cannot have come from far; and no such large slate- fragments, as far as I have been able to discover, are to be found in any of the conglomerates of Bangor, which must be nearer to their source if they come from Anglesey. The quartz- and jasper- pebbles at Moel Tryfaen, on the contrary, are rounded and not so large ; and when we remember the large quartz-pebbles at Bangor and the jasper-fragments at Tairffynon, and also at Llandwrog, we may well believe that these pebbles have come from their original home by two stages, and that their previous resting-place was in the earlier Cambrian conglomerates. It is true that the majority of these ‘‘slates” are so indurated and compact that they are more comparable to the lower beds near Bangor, which are regarded by Dr. Hicks as Pre-Cambrian; but among them there is a minority showing that peculiar banding of purple and green which can scarcely be matched in any bed near Bangor, but only further up the series. Thus, in any case the pebbles are consonant with, and they may be considered to confirm the Mid-Cambrian age of, the conglomerate, and therefore the possibly still Cambrian age of the Llyn-Padarn and Moel-Tryfaen porphyry. But on the ground of a supposed uncon- formity, a long interval is claimed to have elapsed between the two rocks: and this idea is likely to militate against the view of these porphyries and their companions being mere incidents in the Cam- brian succession. As, however, the underlying beds are volcanic breccias, they are naturally irregular, and I will therefore quote the words of Prof. Green in describing them :—‘“‘ The unconformity ... does not necessarily indicate any great difference in age... The breccias are of volcanic origin, and the irregular and restricted upheavals and disturbances, which are always liable to occur where volcanic activity is going on, are quite competent to bring about unconformities quite as marked as those of the present section.” I may quote also the words of Prof. Hughes, which exactly express my view of the matter :—“ In the Llyn-Padarn section the frag- mants in the agglomerates are much rounded, so as to suggest that towards the close of the period of volcanic activity a larger and larger proportion of the volcanic ejectamenta got worked up by the action of the sea, until, at a subsequent (but perhaps not long sub- sequent) period, they were all sea-washed and rolled, forming, with the waste of rocky shores, the coarse conglomerate which we have taken for the base of the Cambrian.” These words are just as true, whether we take the conglomerate as the base of the Cambrian, or as a bed some distance up in the series. But, again, if the beds, as we find them, are approximately in chronological order, the series to the west of the porphyry ought to be distinct from the series on the east. As to this there is a differ- ence that must at once strike every one; on the west side there is not that great mass of workable slate which is so remarkable on the east, and which clings so closely to this old porphyry, coming in with it at Penrhyn and going out with it at Nant-y-llef. To go further it is necessary to enter into some detailed stratigraphy, espe- cially as I regret to find myself in disaccord with the distinct words 286 PROF: J. F. BLAKE ON THE CAMBRIAN of Prof. Ramsay, who says* that the beds “ on the west of the por- phyry are the same in number, arrangement, and lithological character as those on the east.” This point, therefore, must be carefully considered. Prof. Ramsay draws a section from Dinas Dinorwic to Clegyr (fig. 55), in which the two lowest members of the Cambrian undulate at low angles for two miles from Dinas as far as Bryn Efail, where they are cut off by a fault, and these two lowest members are also found on the top of Clegyr. In spite of the undulations, however, he has to make the western portion seven times as thick as the eastern to make a section at all. Then we have seen that the beds nearest Byrn Efail do not dip west, and that there is no fault. At Dinas Dinorwic Dr. Hicks says he has found large one-inch pebbles ina conglomerate. This is not mentioned by Prof. Ramsay, and after twice knocking all over the hili, I failed to find it. If it be there, it is followed by a tough grit, almost lke a felstone, which forms the mass of the hill, and must be of great thickness. There is a dip of 70° inserted on the map. Then at Tyn-y-cleout we have a mass of purple-banded slate, not unlike the Bangor series, which appears to continue a long way. ‘Then we reach the mass of Dinas Mawr, a lofty hill composed of coarse jasper-grit, most like that near Brithdir; to the east of this we have purple slates again, with interbedded grits, gently undulating for the first time, but on the whole not turning up again. Such is the western series (see fig. 8); the eastern has been described by Prof. Bonney. On the railway-section north-east of Llyn Padarn he supposes a fault between the porphyry and the conglomerate; but there is really none; the two may be traced clinging to one another in an irregular line up on to the western slope of Clegyr. On the rail- way the conglomerate is not so distinct from the agglomerate as above (perhaps there is no agglomerate here), and under the low anticlinal further east there is only left a fissile breccia to repre- sent it. After a greenstone-dyke comes a remarkable series of beds, namely, banded hilleflinta, as seen at Bangor, perhaps 50 feet, becoming more slaty at the top, then a remarkable false-bedded band, the lines being made of purple grains and the matrix felsite dust. This is so compacted that it looks quite like afelsite. Itis intensely cleaved across the bedding and false-bedding. This is followed by a one-foot band of purple-slate conglomerate pulled out into lenticules, and interosculating with finer material. Then are seen for 100 ft. greenish slates, getting purple by degrees, and often con- taining another thin band of cleaved felsite-grit, and then the purple slate, which, after an interrupting fold, is seen to be the base of the great roofing-slates. There is not, therefore, really much between the conglomerate and the roofing-slate, and when we compare it with the western beds, the series could not well be more distinet, considering that they are both Cambrian. It is interesting also to note that hilleflinta is not peculiar to the rocks near Bangor, but is rather in relation, as it appears, with a previous volcanic outburst. * Mem. Geol. Surv. vol. iii. 1886, p. 154. ROCKS IN N.W. CARRNARVONSHIRE. From this examination I can- not understand on what Prof. Ramsay’s statement is based. I fear it cannot be maintained. Much of the mapping, too, here is acknowledged to be hypothe- tical, and leads, as I conceive, to too great importance being at- tached to these felsites. Thus the porphyry west of Clegyr, which itself consists of two different flows, separated here and there by deposits of slate *, is never seen to cross the road at Llanbabo, and its occurrence beyond, to- gether with the fault, is entirely conjectural, as the whole country is covered deeply in drift, a cir- cumstance in itself suggestive that the underlying rock is not lkely to be so hard a rock as felsite. Then the felsite of Moel Gronw is not apparently connected with the former, nor can it be traced beyond the road called Cefn-y- waun. ‘The basal conglomerate does not wrap round it, but forms a band clinging to the east of Clegyr only, and leaving Moel Gronw some distance further east. The Moel-Gronw felsite is thus a later outburst, which is separated from the purple slate above by only a band of grit, which perhaps is represented in the form of a thin band of conglomerate seen in the railway at a higher level than the great one. The limits of the felsite, as actually seen, are also very much smaller than drawn on the south-west. The line is carried out as far west as Glan- rafon, on the Gorfai River, where there is an exposure of rocks in the deep river-gorge; but these are quite different from those of Moel Swtan, which is the nearest exposure of the true Llanberis * See Bonney, Quart. Journ. Geol. Soe. vol. xxxv. p. 312. G ‘JIS OSIVOD *¢E "q112 yoed woo ysoMOrT *T ‘9]R[S popueg "QJVIOMLOTSUOD ESIVOD “9 ‘oqetoulojsse yim Arkydaog °*G "OYCS-SuUOOY *¢G So}VIS UeeL *Q v “RIG “YoOt PloqurIpel[eH “LZ *OTMIOUICE svulq ‘qnoejo-£-us J, athsoTO Tey” udag “IMBI, SVUIC. jo odojg ‘urepeg uATT 7o.8RIS 8 29 287 “MSN ic Ms) ‘Uppy UhYT 07 NUNrLOUNT sour mou UonIg—"g “SIT (‘optu [="Ul Z 9[BIg) 288 PROF. J. F. BLAKE ON THE CAMBRIAN felsite. There are three varieties, close together and of small size, probably insignificant intrusions. Then the mapping round Moel Tryfaen is shown by the adit and cutting on that hill to be wrong. There can be no fault between the conglomerate and the slate. The great mass of felsite represented as occurring to the west is all under drift-covered country, while the conglomerate wraps round the felsite between Moel Tryfaen and Pen-y-groes. These correc- tions would curtail the importance of the porphyry and make a great fault unnecessary. Thus the Cambrian age of this mass of porphyry, as determined by the nature of its under and its upper surface, is consonant with, and confirmed by, the other tests to which the conclusion can be submitted. We must now apply this determination to the question of the age of the rocks near Bangor. Since the conglomerates of Llyn Padarn and Moel Tryfaen are not the base of the Cambrian, there is no reason why they should correspond with any particular band in the series at Bangor, either towards the top or at the bottom. But if these Padarn conglomerates are not the base, where is it? Nowhere in this particular area. We go downwards as we go westwards till interrupted by a pair of trough faults, letting down the Ordovician. When we get over this and come upon the older beds again, what should they be but the continuations westward of the Cambrian series? There is scarcely a bed amongst them that we cannot match somewhere or other in the higher parts of the series, though on a smaller scale. Considering the lateral changes that may take place in rocks, and the frequent dying-out of conglo- merates, we cannot safely say that all the Bangor beds underlie all those from Dinas Dinorwie east: the correlation of bed with bed, or the proof of their independence, if it were thought of importance, would require a further long series of stratigraphical researches. All we can say is, that we see to the south of Bangor the base of the Cambrian down to a great felsite lava-flow; but whether this, like that at Llyn Padarn, was contemporaneous and followed below by earlier deposits still, or was erupted at a date that may be fairly separated from the Cambrian period, there is not enough evidence in this district to show. Conclusions. The results of the examination in the areas between Bangor and Caernarvon, and from Llyn Padarn to Moel Tryfaen, of the rocks which are found within them, are not very confirmatory of the views of recent observers, but lead us back, with certain important modi- fications, to the earlier teachings of the Survey on the district. They may be summarized as follows :— 1. In the Bangor to Caernarvon area: three distinct conglomerates have been confounded together. The only one which, by its uncon- formable overlap, sets an upper limit to the age of the rocks below ROCKS IN N.W. CAERNARVONSHIRE. 289 is of Arenig, z.¢. of Ordovician age, and can only be called Cam- brian by the misleading use of the term, which embraces all rocks up to the Bala series. 2. The rocks of the southern and central portion are essentially of igneous origin. 3. These may clearly be distinguished into two groups, of which the southern is probably intrusive, and the northern is certainly eruptive. 4. There is an interval of time between their production; but how great an interval, there is no evidence to show. That the southern mass is of later date than the Arenig, and intrusive into it, is a tenable hypothesis; but that it is of earlier date and over- lain by the northern portion, is far more probable. 5. The Bangor beds are derived from the denudation of the volcanic series and of rocks which may have been associated with it. 6. These beds contain a series of conformable conglomerates, of which the great conglomerates near Bangor are members. 7. They are the continuation downwards of the Cambrian rocks seen to the east, and have not undergone very serious alteration compared with the latter. 8. The porphyries of Llyn Padarn and Moel Tryfaen are contem- poraneous lava-flows in the midst of the Cambrian series, the over- lying conglomerates being derived from them and from the Cam- brian sedimentary rocks to the west. And hence, finally, there is no certain proof of there being any Pre-Cambrian rocks in the whole district, though there is great probability that the rock near Caernarvon belongs to a distinct epoch anterior to the Cambrian. I may add that nothing here observed invalidates former con- clusions as to the essential independence of the group which lies below the true basal Cambrian conglomerate in the St. David’s dis- trict. That group does not bear sufficient resemblance to the series in north-west Caernarvonshire to justify their correlation, and the unconformity there observed is of a totally different order, and com- parable rather to the overlap of the Ordovician beds in this district. Discussion. Prof. T. M°K. Hues said the question was too large and in- tricate to discuss thoroughly at so late an hour. His reading of the stratigraphy of the Twt-Hill quarry and of the sections near Llandeiniolen and Bangor differed altogether from that of Prof. Blake, whose correlation of the various conglomerates appeared very doubtful. Dr. Hicks felt the same difficulty. In his opinion Prof. Blake had misunderstood the beds and had not sufficiently considered the effects produced by the faults. The pebbles of felsite in the Cambrian conglomerates showed a cleavage produced before they were broken 290 ON THE CAMBRIAN ROCKS IN N.W. CAERNARVONSHIRE. from the parent rock. At Llyn Padarn the Cambrian conglomerates rest on the cleaved edges of the underlying felsitic rocks, therefore the latter cannot be intrusive in the Cambrian. Prof. Brake, in reply, said he had the advantage of having read Prof. Hughes’s and Dr. Hicks’s papers. He showed that if Prof. Hughes’s view of the Twt-Huill quarry-section were correct, the change would not be opposed to his (Prof. Blake’s) contention. Some other objections were answered in detail. MR. T, M. READE—AN ESTIMATE OF POST-GLACIAL TIME. 291 22. An Estimate of Post-Gractat Tore. By T. Metrarp Reanp, Esq., C.E., F.G.8., F.R.LB.A. (Read February 29, 1888.) Or late several attempts have been made to show that the close of the Glacial period was very recent*. Having personally devoted considerable attention to what is called Post-glacial or “superficial” geology, I am much struck with the imperfect knowledge with which the question of Post- glacial time is frequently approached. The writers seem to be unaware of, or to insufficiently appreciate, the grand sequence of events recorded in the deposits on the Lan- cashire and Cheshire coasts which have taken place since the snow and ice of the Glacial period disappeared rf. On the borders of the coast-line between the Dee, the Mersey, and the Ribble, the student who cares to pursue the subject can do so with great advantage. But through the horizontality of the deposits, and their general low level, none occurring above the level of the 25 feet Ordnance datum and all reaching down to below the level of the lowest spring-tides, the study has to be pursued through the medium of excavations and borings. This I have done in observa- tions extending over many years, and I now propose to show their bearing upon the absorbing question of recent geological time. Denudation of the Low-Level Marine Boulder-clay. The whole of the country to which these notes specially refer was formerly entirely covered with a mantle of Low-level marine Boulder- clay and sands. These I have described at length in several papers ¢. That the valleys of the Dee, Mersey, and Ribble were at one time filied with Low-level marine Boulder-clay, we have, I think,in- dubitable evidence. The ancient or Pre-glacial course of the Mersey was, as I have shown, under the site of the town of Widnes in Lan- cashire, and, as numerous borings have disclosed, it is now, with the exception of some superficial deposits of estuarine mnd, entirely filled with Low-level marine Boulder-clay and sands. There is strong reason to believe that even here a considerable amount of Boulder-clay was removed before the deposit of the recent silt ; but, * Professor Prestwich estimates that the final melting away of the ice of the Glacial period took place within from 8000 to 10,000 years of the present time (Q. J. G. S. vol. xliii. 1887, p. 407). Mr. Mackintosh estimated it at not more than 6000 years (see Geol. Mag. 1883, p. 189 and pp. 191, 192). t Professor James Geikie, in ‘Pre-historic Hurope,’ is one of the few who appear to have made themselves acquainted with the remarkable and important . changes it is attempted in this paper to explain. . { “Drift beds of the North-west of England,” Q. J. G. S., part 1, 1874, part 2, 1883. Seealso C. E. De Rance, Q. J. G. S. vol. xxvi. p. 657 ; ‘ Memoirs of the Geological Survey,’ &c. ; G. H. Morton, ‘ Geology of the Neighbourhood of Liverpool ;’ and various papers by D. Mackintosh, Robert Bostock, Dr. Ricketts, and several local archzologists and geologists. 292 MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME. in the present course of the river, the Boulder-clay has been scoured out in places down to the bed-rock. That the Mersey Valley was filled with Boulder-clay, at least to the level of that in the pre- glacial channel at Widnes, will not, I think, be disputed by any- one who knows the locality. There can be little doubt that the Boulder-clay originally filled up the channel of the estuary between Liverpool and Birkenhead. A remnant of it lying ina Pre-glacial channel, the existence of which I ventured in 1872 to predict, was bored through in 1884 by the Mersey Tunnel Works. That Wallasey Pool, now occupied by the Birkenhead Docks, was formerly levelled up with Boulder-clay is equally evident. The Boulder-clay also exists, or formerly existed, in a thickness sufficient for brickmaking, at Edgehill, on the Lancashire side of the Mersey, at a level of 200 feet above Ordnance datum. When we consider the proximity of this locality to the Mersey, and the tendency of deposits to work down to and accumulate at lower levels, together with the proved instance of levelling up at Widnes, we can hardly refuse to believe that the Mersey Valley was formerly filled with Boulder-clay. To be assured that such a levelling up takes place in a sea-bottom, we have only to examine a chart of the Trish Sea, which represents a slightly undulating floor or vast plain having no irregularities of level even approximating to those of the valley of the Mersey. That there exist in this sea-area, could we bare it down to the bottom rock, river-valleys or considerable irregularities of contour, is shown by the “ditch” opposite Wigton- shire, where the tide, which here flows very fast, has scooped out a channel from 400 feet to 600 feet deep. The evidences that the Mersey Valley was once levelled up with Boulder-clay is further confirmed by the boring at Halewood, about three quarters of a mile from Hunts-Cross Railway Station, which penetrated 137 feet of drift presumably lying in a former tributary of the Mersey, of which there was no evidence on the surface. The same may be said of that at Hooton, Cheshire, which went through 169 feet of drift, lying in a valley. A bore-hole at Iches- ter wharf, Birkenhead float, penetrated 166 feet of alluvium and drift, and I have little doubt that these are only a few out of many examples of the general levelling up that took place during the submergence of the Glacial period. It is thus quite clear that an enormous mass of glacial deposits has been swept out of the Mersey Valley. That this was mainly done by subaerial agents, when the land was at a higher level than at present, is proved by the numerous tributary streams which ~ branched into it and are now partially filled with Post-glacial deposits. Everywhere below the Post-glacial deposits, to be pre- sently described, the Glacial beds are deeply eroded and show evidences of long subaerial waste. How much time can be reasonably put down for these changes will be presently discussed. Post-glacial Beds.—In a few places on the Boulder-clay surface are found remains of vegetation, and above them a series of estuarine MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME, 293 deposits containing marine shells, such as Tellina, Mytilus, Turritella, &c., and in certain laminated clays Scrobicularia piperata in the vertical position in which it lived. These Post-glacial deposits, where they occur, have levelled up the inequalities produced by the pre- vious subaerial erosion of the Boulder-clay, and they cover an exten- sive area amounting to some 75 square miles between the Ribble and the Mersey. It is difficult to say what their maximum thick- ness is, but they are known to be, in places, 50 feet deep. The deposits thin out landwards towards the ancient shore-line, so that the borings in the centre of the Moss-lands show less than this thickness *. None of these deposits, which are very general and are found even as high up the river as Warrington, reach above the level of the 25 feet Ordnance contour. It is manifest that they represent a period of subsidence probably long continued. Mammalian remains are found in these beds, but no extinct animal is represented. Lying upon these silts and blue laminated clays is a very exten- sive peat-bed containing the stools of trees with the roots ramifying into the clays or silts below. They are mostly oak, birch, and pine. That these trees have grown in the position in which they are now found we have ample evidence. It therefore follows that the Post-glacial estuarine beds in which they are rooted, after being laid down, were elevated sufficiently for the efficient drainage of the land, and there is strong reason to believe that at this time Great Britain was united to the continent of Europe. Similar submarine forests can be traced all round Great Britain and Ireland, the Isle of Man, and the north coast of France, and I believe that most of them are synchronous with our Lancashire and Cheshire submarine forests. These forests represent, then, a period of general elevation extensive in area, but of unknown vertical range. Since the growth of these extensive forests, there has again been a subsidence, so that many of them became submerged beneath the sea, and it is to this cause that we owe their partial preservation. Along the littoral margin they are frequently found beneath blown sand, and have, in places, recent estuarine silts deposited upon them. That all these changes occurred, there is evidence amply sufficient to satisfy any unprejudiced mind. I know of few events in geology more clearly recorded than those just detailed 7. The channel of the Mersey, as proved by borings made during the opposition to the Manchester Canal, is largely filled with Post- glacial gravels. The precise age of these it is difficult to determine, but probably they are the remnants of the Boulder-clay washed out during the subaerial excavation of the present channel. Some of * See “ Borings on the Southport and Cheshire Lines Extension Railway,” Proce. of Liverpool Geol. Soc. 1884-5, p. 93. T See ‘ Post-glacial Geology of Lancashire and Cheshire,” Proc. of Liverpool Geol. Soc. 1871-2; “The buried valley of the Mersey,” ibid. 1872-3; “On a section at Hightown,” ibid. 1881-2; “The Mersey Tunnel, its Geological Aspects and Results,” ibid. 1884-5; “Some further Notes on the submarine forest at the Alt Mouth,” ibid. 1877-8 ; ‘‘ A problem for Irish geologists in Post-glacial Geology,” Scientific Proceedings of the Royal Dublin Society, 1879. 294 MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME. the gravel may have been reworked up by the sea. Borings from Weston Point to Hale Head showed the presence of gravel, peat, and sand below the present bottom *. Length of Time represented by the foregoing Post-glacial Geologie Changes. That these changes represent a very considerable lapse of time, seems to me almost self-evident; but how can we obtain a true scale with which to measure it? In making the attemptit will be better to reverse the order in which we have described the events, and begin with the latest deposits. In a paper on “The date of the last Change of Level in Lan- cashire” 7, I have attempted to show, from observations made of the rate of accumulation of blown sand at Blundellsands, that the minimum time required for the accumulation of the 22 square miles of blown sand between Liverpool and the Ribble must be put down at 2500 years, and that no appreciable change of level has taken place in the coast-line within that period. History does not go quite that far back; but so far as it does (that is to the time of the Roman occupation of Britain), there is no evidence of any value pointing to any change of level having taken place; nay, what evidence there is is strongly the other way. The Roman fords on the river Dee show plainly that the state of things then was much as it is now ft. The Roman remains found at Hoylake came from a stratum of soil above the peat-and-forest bed. It is evident from this that the peat-and-forest bed was in existence in Roman times in much the same condition in which it appears now. It is in consequence of being buried by blown sand that such numerous evidences of Roman» tenancy have been preserved at Hoylake. The Roman station was probably situated just inside of the sand-dunes, which have since encroached upon it and entombed its remains. I know of no implements or other evidences of human handiwork haying been. found either imbedded in the superior peat or in the silts below, but I have found them in the superficial layers lying on the peat. I am satisfied that 2500 years is a reasonable minimum limit to the beginning of the present condition of level of land and water; but it may be much older. The superior peat-and-forest bed represents, as I have attempted to show §, a continental connexion with these islands, and if so, the land must have subsided not less than 200 ft. since the connexion existed. Now comes our difficulty: What rate must we allow for the sub- * “The Mersey Tunnel, its Geological Aspects and Results,” Proc. of Liverpool Geol. Soc. for 1884-5. t Quart. Journ. Geol. Soc, Aug. 1881, vol. xxxvii. pp. 436-9. t See paper by the late Mr. R. Bostock, Proc. of Liverpool Geol. Soc., March 8th, 1870. An examination of the Roman Wall lately disclosed by excavations in the Roodeye has satisfied me that the level of Chester, in relation to the sea, is practically now what it was in Roman times. § See “ Post-glacial Gevlogy of Lancashire and Cheshire,” before referred to. MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME. 295 sidence? We have really very little evidence to go upon excepting that regional changes of land and sea are extremely slow. If we put it down at 2 feet per century, the subsidence would be com- pleted in 10,000 years ; let us, however, be generous and say 4 feet per century, which would give 5000 years. But then land-movements are not always going on; we have seen that the land has been practically stationary for the last 2500 years. If we allow another 2500 years for a pause before the subsidence began, we shall, I think, make a very low estimate. The elevation of the estuarine silts (Formby and Leasowe beds) must have preceded the depression, and as they were mainly laid down at approximately the same relative level of land and sea as now obtains, we shall have to allow 5000 years for the elevatory movement, estimated at the same rate as the subsidence *. Working backwards from the present time we arrive at the conclusion that (2500 + 5000 + 2500+5000=) 15,000 years is a very moderate estimate for the time which has elapsed since the completion of the laying down of the Formby and Leasowe estuarine silts. Working still backwards in time, if we allow another 2500 years for the pause during which the estuarine silts underlying the peat- and forest-bed were laid down, a parsimonious estimate I consider, we shall arrive at a total of 17,500 years for the time occupied by the Post-glacial changes represented by the Formby and Leasowe and accompanying forest-beds. But, as I have indicated, the denudation of the Boulder-clay upon which these deposits lieis very great and represents a much greater lapse of time. Measured in the centre of the valley, at least 100 feet, and probably more, of glacial deposits had been swept out of the Mersey Valley before these Post-glacial beds were laiddown. Again we are in a difficulty for a time-modulus to apply to the excavation of the valley, which would be more rapid than the general lowering of average ground, the rate of which may be taken at 1 foot in 4000 yearst. Let us assume that the valley was swept of its -deposits at the mean rate of 1 foot in 400 years, or 10 times the general mean rate; the time occupied in the denudation of 100 feet would be 40,000 years. Considering that the Mersey Valley was widened out to nearly its present extent before the estuarine beds were laid down, a mean rate of 1 foot in 400 years is, to my mind, very rapid. As there are no indications of glacial action during the course of these events, I think that the estimate of 57,500 + years (17,500 + 40,000), say in round figures 60,000 years, for Post-glacial time a reasonable one and, as represented by these changes, well within the mark. The calculation includes the time occupied in the elevation of the glacial deposits from beneath the sea, as it is assumed that the * There are no known instances affecting so large an area of a rate of elevation or subsidence so great as this. The observations in Sweden showed a mean rise of 3 ft. 6 in. in 134 years. ‘ Nature,’ Dec. 18, 1884, p. 150. + “A Delta in miniature,’ Quart. Journ. Geol. Soc. May, 1884. “ Denu- dation of the two Americas,” Presidential Address, Liverpool Geol. Soc. 1884-5. ¢ Dr. Croll, from entirely different data, estimates it at 80,000 years. 296 MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME. denudation went on part passu with the elevation. It may be urged that the mean lowering of the ground in a Boulder-clay area would proceed much more rapidly than in average ground composed of a variety of rocks. Jam not prepared to admit this. Boulder-clay is a very tenacious substance, and, if only attacked from the top surface, takes long to denude. The valleys would be excavated at a greater rate than in rock, provided there were a sufficient gradient, as the clay is more readily undermined. This I have allowed for in the increased rate of valley- excavation. No ordinary rock would be worn down so quickly as 1 foot in 400 years. Again the rate of vertical excavation by a river would not be uniform ; it would proceed with greater rapidity at first and decrease as it reached the base-level of erosion, then it would cease entirely. All this time the valley would be widening and would continue to widen, though the vertical excavation ceased. Other things being alike, the widest valley must be the oldest. The Mersey Valley is distinguished for its width in the upper estuary, and, in this, tidal action has helped. When we look at the River Ribble below Ribchester, we cannot help being impressed with the idea that there has been little change since the Roman times. I found in 1882 Roman tiles 3 feet below the surface-soil, on the river-cliffs, resting on the Boulder-clay. There are Boulder-clay cliffs on either bank, so that the lateral movement of the river at this part since Roman times cannot have been great. It is quite apparent that there has been in the area under con- sideration considerable general denudation of the Boulder-clay. Rocky knolls once covered have been laid bare. Here and there we find patches of Boulder-clay as indications of its former pre- sence. The surface of the clay below the soil is full of ramified channels and holes filled with the sand left from the destruction of the clay above *. Unfortunately there are no zones in the clay by which we might be enabled to say how much of it has been removed in particular areas. We are thus driven to the valleys for an answer. They are in many cases remarkably wide, with Boulder- clay at the bottom and on the plateau above, while the flanks often display the rock surface. This is the case at many points in the Mersey Valley and in its tributaries. When we consider that at the rate of 1 foot in 4000 years the mean general lowering would only amount to 10 feet in 40,000 years, we may well consider our estimate based on valley-denudation a moderate one. When first investigating the Post-glacial deposits of south-west Lancashire and Cheshire, I was much impressed with the great lapse of time they indicate; and a long acquaintance with this class of geological investigation has not lessened the impression. As I have before stated, in none of the Post-glacial beds have any remains of extinct animals been found. If at a future time any * See “ Subsoil Denudation of Boulder-clay,” Geol. Mag. 1882, p. 265. ‘MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME, 997 should be found, it will probably be below the estuarine: beds on the surface of the Boulder-clay. There is little doubt that this surface was occupied by a fauna now partially extinct ; but the subaerial conditions, which lasted so great a length of time, were apparently unfavourable to the preser- vation of their remains, Sir Charles Lyell states that the skulls of two Mammoths were taken out of the excavation made for the Holyhead Railway, near the harbour, two feet below the surface of a bed of peat, which was covered with stiff blue clay. This peat was continuous with that exposed at low water in the harbour of Holy- head, in which were seen stumps and roots of trees *. The basis on which we have had to construct our estimate is naturally imperfect ; but against any possible overestimate of time which may have crept in from the imperfection of the time-measures applied to the events, is to be set the possibility of other events having happened which are unrecorded or unreadable in the deposits which we have been considering. Discussion. The Present anticipated a considerable amount of discussion on a question which had already engaged the attention of so many writers. Prof. Presrwich thought the sections of much interest, but wanted to know the terms of the discussion. What was meant by the so-called post-glacial deposits indicated in the column? There was no evidence of their being of post-glacial age, either in the presence of extinct Mammalia or of boreal Mollusca. The AvutHor explained that all the deposits between the Marine Low-level Boulder-clay and the recent deposits were included in his “ post-glacial.” Prof. Presrwicu remarked that these deposits contain only recent shells: they are in fact merely ordinary alluvial deposits with the submerged forests, so common round many of our coasts. The dates the Author proposed to assign to these neolithic deposits were founded on estimates entirely his own. But little reliance was to be placed on the thickness of beds accumulated at the mouth of a river. Mr. Dz Rance observed that his first paper before the Society dealt with this area and subject. It was a satisfaction to him to agree with Mr. Reade’s descriptions, though their conclusions were at variance. The Mersey was a case ofa valley within a valley, a pre- glacial valley filled in with glacial deposits, a post-glacial one fringed with river-terraces. The case was somewhat different as regards the Ribble, west of Preston. He pointed out the great thickness of the drift in the Fylde,its base being below sea-level for many miles. He described the position of the peat-bed and its vertical range, and the amount of excavation effected in the valley since the period of the Upper Boulder-clay, the several stages being marked by terraces, * ‘Principles,’ 10th ed. vol. i. p. 545. Q.J.G.8. No. 174. Me 298 MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME, the last being the alluvial flat. He corroborated Mr. Reade’s statement as to the small change of level since the time of the Romans, but thought that in arguing with respect to the amount of time, he was reckoning without his host; for the valleys had reached their negative gradient before the Roman period. There were no links for the calculation of time for the formation of deposits older than the Roman era. Dr. Evans had himself abstained from reducing geological time to years, but he admired the Author’s ingenuity. However, he had left out of his calculation certain stages. There was no evidence as to the time elapsed between the Boulder-clay and the base of these deposits, and very little as to whether they were marine or alluvial. If marine shells are absent these beds are probably alluvial and comparatively modern. He contrasted the estimate of the time ~ required for their deposition with the short period allowed by some recent authors for the interval between the Glacial epoch and the present day. Mr. Crewent Rez remarked that there was a very similar succession in the deposits of the Humber. A rough calculation had shown that the highest buried forest in that district may have been submerged about 3000 years ago; and the pile-dwelling at Ulrome seemed to prove that it occurred before part of the Neolithic period. He thought that the Author had overlooked the fact that when the land was higher, denudation, and consequently deposition, would be more rapid. This seemed to invalidate any calculations based on the present rate of deposition of silt. He had found it impossible to make any estimate of the time represented by the deposits below the highest submerged forest. Mr. Wurraxrer thought that Mr. Reade’s post-glacial beds were newer than the valley-gravels of the south-east of England. The terms post-glacial and glacial have a different meaning in different places; some of the post-glacial drift of one district may be as old as some of the glacial drift of another district ; thus southern post- glacial drift may be as old as the Boulder-clay in the column. He spoke cf the rapid accumulation of alluvial marsh-clays and peat- beds, as at Tilbury Docks. © Mr. Torrey pointed out that the beds under discussion, which upon any view of the case represented a long period of time, were later in date than those of the Cae-Gwyn Caves. Prof. Prestwich remarked that there was considerable corre- spondence between Mr. Reade’s section and that at Tilbury Dock, but at the latter place the alluvial deposits were under 100 feet thick, and rested, not on Boulder-clay, but on the latest of the valley gravels, or true so-called post-glacial beds. The AvrHor scarcely expected that any one would fully agree with him on the question of lapse of time. There had been some misapprehension amongst the speakers, who had confined their remarks mainly to the time occupied in the formation of what he called the post-glacial deposits. But he had largely relied upon the time occupied in the clearing out of enormous quantities of marine MR. T. M. READE—AN ESTIMATE OF POST-GLACIAL TIME, 299 Boulder-clay in the valleys of the Mersey, Dee, and Ribble. This post-glacial erosion preceded the deposition of the estuarine and Peat- and Forest-beds, which lie on the denuded surfaces of the remnants of Boulder-clay now occupying the valleys. His estimate of 1 foot in 400 years for the valley-erosion was not excessive, being ten times more than the present general rate of denudation. He referred to the proofs of the surface of the Boulder-clay being much eroded. He only pretended to give an approximate estimate, which was really below the mark. He thought it possible to apply a time-scale to certain beds. x2 300 MR. G. A. J. COLE ON SOME ADDITIONAL 23. On some ADDITIONAL OccURRENCES of TACHYLYTE. By Grenvinte A.J. Corz, Esq., F.G.S. (Read February 29, 1888.) [Puate XTI.] Since the spring of 1883, when I had the honour of being associated with Prof. Judd in a paper on the Basalt-glass of the Western Isles of Scotland*, a few additional occurrences of tachylyte in the British Isles have come under my notice in the field. Specimens have been thus collected from Ardtun in Mull, Kilmelfort in Argyll, from near Bryansford, County Down, in Ireland, and among certain older rocks of the Welsh border. JI am also enabled, by the kindness of my friend Mr. A. W. Dymond, to give an account of the micro- scopic characters of the tachylyte of the Quiraing in Skye. The Duke of Argyll, in his classic description of the leaf-beds of Ardtun in Mullt, refers to a glassy layer between two of the basaltic masses of the headland; and the same occurrence was mentioned by Mr. Koch during the discussion on the paper dealing with Scottish basalt-glass. Mr. J. Starkie Gardner, who called my attention to the rock upon the ground itself, has described and figured the course of an intrusive sheet that forms a very conspicuous feature at Ardtun{. At its most accessible portion it is about 8 ft. thick, and in the centre still retains, as shown by microscopic examination, a considerable amount of colourless glassy matter. In this matrix cumulites and belonites are developed; plagioclase felspar is abundant, interspersed with brown prismatic augite, while the magnetite is collected into crystals that are often well defined. On a sea-face so exposed the rock has naturally suffered, and the black lustrous specks visible in it to the naked eye prove to be soft products of alteration$. I1tdoes not appear, however, that they are pseudomorphs after olivine, a mineral which is in this case rare, if not altogether absent. On the other hand, the few specks of quartz that occur are clearly of secondary origin. The upper and lower surfaces of this intrusive sheet have, by rapid cooling against the surrounding basalt-flows, become coated with a black glassy selvage, which is seldom more than an inch in thickness. This tachylyte adheres more firmly to the contact-rocks than to the mass from which it was developed; but microscopic examination opposes the idea that an intermingling through fusion has taken place along the planes of junction. The crystals of the overlying basalt are, indeed, seen to be sharply broken through, and abut un- altered against the intrusive glass. The tachyly te itself is fairly fresh, though traversed by the numerous joint-planes characteristic of this class of rock. Its * Quart. Journ. Geol. Soc. vol. xxxix. p. 444. + Ibid. vol. vii. (1851), p. 94. { Lbid. vol. xliii. (1887) pp. 271, 272. g Compare the chlorophzite of Macculloch, ‘ Western Islands of Scotland, vol. i. p. 504. — OCCURRENCES OF TACHYLYTE. 301 colour is a rich blue-black. Its high specific gravity, which reaches 2°83, may be explained by the crowding of spherulites in many parts and the consequent approach to a crystalline condition. The rock, however, that forms the centre of the intrusive sheet has a specific gravity of only 2°79, as determined both by the chemical balance and by Attwood’s instrument on a large and representative specimen. This anomaly parallels the examples cited by Delesse *, who himself recognized how the density of different portions of an intrusive mass might be affected by decomposition at the centre rather than at the margins 7. The hardness of the glass of Ardtun is 6, and its fusibility equals 2°5 of von Kobell’s scale, the product of fusion being a brown glass full of bubbles, which is blown out almost to a pumice when treated in the blast of a Herapath blowpipe. ‘The powder of the rock is not attracted even by a powerful bar-magnet. Under the microscope this tachylyte is found to repeat in the basic series the transition from glassy to completely spherulitic forms which is so familiar among acid lavas. Near the surfaces of junction the glass, rich orange-brown when thinly ground, is full of crystal- dust and shadowy aggregations. A few minute amygdaloidal vesicles, elliptical in section, are scattered here and there, the glass being lightest round them, this zone of different hue being very likely due to alteration spreading inwards. .During the infilling of such cavities, the surrounding glass may often undergo a change, this being notably the case in the tuff of Aci Reale, Sicily, where every vesicle in the fragments of basalt-glass is bordered by a ring of brown palagonite. By gradual extension these rings unite, and effect the alteration of whole areas. The Ardtun glass contains spherulites in all stages of development ; and the brown globulitic matter of which they are composed is more and more condensed towards their centres, where they become practically opaque. A layer of spherules has formed in places on the very surface of the intrusive sheet, and the condensation of material towards the flattened side of these has given rise to a dark band along the plane of contact. A similar instance of the separating-out of materials on the plane of junction is described by Mr. Rutley {, who has kindly allowed me the use of his original slides. In both of these cases, the artificial and the natural, I take it that no very sudden chilling has occurred, and in the sub- sequent gradual cooling the crystallites have utilized the surface presented to them as a basis of aggregation, just as they cluster round a porphyritic crystal or any similar inclusion (Pl. XI. fig. 1). Further from and parallel to the edge of the intrusive sheet, bands of brown spherulites traverse the darker glass, which is here more opaque through accumulation of minutely separated matter; and finally the glass is practically eliminated, the spherulites assuming polygonal outlines as they come in contact with one another * Métamorphisme des Roches, pp. 403-407. t Ibid. p. 406. t Proc. Roy. Soc. vol. xl. (1886), p. 438. 302 MR. G. A. J. COLE ON SOME ADDITIONAL (Pl. XI. fig. 2), At the same time the material of the spherulites, settling into a crystallized condition, becomes greyish in certain sectors and richly brown in others. A minute vesicle, filled with secondary minerals, occurs frequently at the centre of the spheru- lite, and may perhaps be a feature of alteration, extending inwards from the point of weakness; but, on the other hand, the regular outline of these vesicles gives support to the view of several writers, that such gas-bubbles may, like included bodies, serve as centres of devitrification *. The radial structure in the Ardtun spherulites is seldom regular, though clearly seen; and the black cross, its arms parallel to the vibration-planes of the crossed nicols, is frequently much disturbed. With a single nicol the spherulites, when well developed, show remarkable phenomena of absorption. The browner fibres become of a darker hue when their longer axes are placed parallel to the shorter diagonal of the nicol; while the greyer groups, in the same spherulite, are at their darkest in the reverse position. Since this change of hue is very striking, a dark bar like one half of the cross, and due to brown or greyer fibres, is frequently seen traversing the spherulite when only one nicol is employed: and, if grey and brown sectors are suitably grouped in the same example, a complete dark cross may be shadowed out in one position, rotation of the slide through 90° reversing the conditions, and showing both vertically and horizontally placed fibres at their lightest +. While Iam not prepared to explain the pleochroism of the greyer sectors, it seems probable that, among the fibres of these basic spherulites, a separation into distinct mineral substances has oc- curred t. The greater tendency to crystallization in basaltic rocks may, indeed, cause a granophyric structure to arise under conditions that would, in acid lavas, produce spherulites practically isotropic. The surface of a section of the Ardtun rock, when etched with hydrofluoric acid, gives no very definite evidence; but somewhat greater resistance to the acid is offered by the browner rays. It must be borne in mind that the minerals composing such a grano- phyric spherule—a “ pseudospherulite ” of Rosenbusch—may he far different from those that separate during a less hurried process of crystallization, and that combinations may indeed be formed unknown to the cabinets of collectors. In augites rich in alkalies, however, such as are developed in many glassy rocks, the axis of maximum elasticity approximates to the vertical crystallographic axis, and a prismatic section exhibits its darkest tint when the * The possible liberation of gas during the formation of a spherulite is discussed by Iddings (Amer. Journ. of Sci. vol. xxxiii. (1887), p. 48). +t Such phenomena of absorption seem to be by no means rare. They occur, for example, in a spherulitic tachylyte from Tasmania, and in the spherulites developed in artificial basalt-glass, as in the fused product of the “ Rowley Rag.” Even some acid lavas, as the perlitic rocks of Hlinik and of Puszti Hrad in Hungary, contain spherulites with pleochroic rays. ¢ Iam glad to find that Dr. Wenjukoff holds the same opinion with regard to the spherulitic tachylyte of Sichota Alin (Bull. Soc. Belge de Géologie, tome 1. (1887), p. 174)... OCCURRENCES OF TACHYLYTE. 303 light entering it vibrates parallel to this same direction. It will be seen that the extinctions and pleochroism of the browner rays, as described above, are not opposed to the suggestion that they are of pyroxenic character. Two and a half inches from its outer surface, the Ardtun basalt has given rise toa multitude of interlacing rods, with here and there traces of a radial arrangement. These rods, like those in the tachy- lyte of Lamlash *, are themselves composed of individualized granules grouped along definite lines. In this instance the constitu~ ent crystallites are of prismatic outline, and may be measured with a high magnifying-power, being about ‘004 of a millimetre long. As we trace this structure towards the interior of the mass, long skeletons of colourless felspar are evolved, and round these are clustered numberless little prisms and granules, the embryos of the pyroxenes that abound at the centre of the sheet. A glassy selvage of even an inch in thickness would seem in itself to indicate a basalt rich in silica and the alkalies, a rock, in fact, on the threshold of the andesitic series. A determination of the chief chemical constituents of the Ardtun tachylyte has yielded me the following result, the specimen selected being from the lower selvage of the intrusive sheet :— Ra Gradiy ohh) Corecess wea aNb ya Wide Kad 53°03 ON MARIN R tad, hice Bi ral sharia hea abe Rie about 20:09 ANE coagia Gay a ca ca! ap 5 1286) api) t'aime asta) 9°43 MiGs Sl tvttjan int. ayy gd @aabl dio as «| GeO MORIA ry, dt dyeys, arm phobia x Fauard id Wi lone 2°63 les ites ch ite dant a tnt tj diane hy iets witd 2 4-52 eh G Eien paca) acc dace duentiiiennanal de ¢ LOT ass OR) FAMMAGM ccd sieeve ward cca ms 2°64 99-66 The rock thus corresponds closely in composition with the basalt- glass of the Beal in Skyet, and is another addition to the more highly silicated and more aluminous examples, as distinct from the lavas of Hawaii, which are far richer in magnesia and lime. The next occurrence of tachylyte to be described is at Kilmelfort, on the Argyll coast, where, in 1883, in a quarry just north of the Cuilfail Hotel and opposite a tiny lake, I noticed a dyke, fringed with glass, giving off a vein into the surrounding greyer rock. This dyke was only from one to two feet across, and had merely a film of glass upon its surfaces; the vein connected with it, about two inches in width, showed also a thin tachylytic selvage. In another part of * Quart. Journ. Geol. Soe. vol. xxxix. pl. xiv. fig. 2. t I am aware of the objection raised by Stecher to this inference (Tscher- mak’s Mittheilungen, 1887, p. 198); but almost all the tachylytic dykes de- scribed from Scotland traverse basaltic masses, and the similarity of con- Ng at the immediate edge has prompted the comparisons that have been made. { Quart. Journ. Geol. Soc. vol. xxxix. p. 455. 304 MR. G, A. J. COLE ON SOME ADDITIONAL the quarry a sharply-defined little dyke or vein, perhaps connected with the other below the surface, and 27 inches wide at the most, was similarly bounded by black glass. In section this last-named tachylyte appears brown, but its nar- rowness diminishes its interest. ‘The development of felspars in the adjacent basalt is, however, well displayed, the colourless prisms being often incomplete or bifurcated at the ends. This basalt is of normal character, with porphyritic olivines, a fact that may in itself explain, when ordinary temperatures are concerned, the small de- velopment of the glass. The surrounding rock is a rudely columnar hornblende-mica-porphyrite, with inclusions of mica-slate, and shows in section a very thin film, as if of partial fusion, at its junction with the invading basalt *. - I am indebted, as already mentioned, to Mr. A. W. Dymond, of the Royal School of Mines, for a specimen of tachylyte from the Quiraing in Skye. Although this fragment was found upon the talus, it probably formed part of the layer described and analyzed by Prof. Heddle t, and this fact must be my excuse for dealing with a rock with which I have no acquaintance in the field. The glass in its present condition is easily scratched with a knife, and is, in fact, as its analysis sufficiently indicates, verging on palagonite. It retains, however, when viewed in microscopic section, all the delicate structure produced by devitrification during cooling. ‘The matrix is of a yellow-brown tint, and includes nume- rous small spherulitic aggregations, about 1 millimetre in diameter. The first-formed fibres of these are frequently arranged in sheaves, recalling the “ chiasmolites” of Krukenberg {, which are in this case converted by subsequent additions from without into double or single spherulites and axiolites. In comparison with their rich brown colour, the surrounding glass looks almost grey. The steam- vesicles in this rock seem to have had no influence whatever on the development of the spherulites. The residual glass abounds in transparent globulites, and in spherical groups of these minute bodies, forming the cumulites of Vogelsang. There are also little bunches of dark crystallite-fibres, grouped so as to form right-angled figures with hollow sides. These, together with more defined crystals, probably represent the * Through the kindness of Mr. F. H. Butler, M.A., I am able to record here the following occurrences of tachylyte, which were noticed by himself and Mr. P. F. Kendall, during a visit to the Isle of Mull. A columnar dyke below a waterfall in the Tobermory Burn, about three feet across, and a fine-grained columnar dyke at Rudha nan Gall, are bordered by basalt-glass. Another basalt, near the Erray Burn, west-north-west of this last point, and containing porphyritic felspars, has also vitreous selvages. t Min. Mag. vol. v. p. 8. In the errata of the same volume, Prof. Heddle directs attention to the old term “ Gallinase.” It is of interest to find that in Buffon’s ‘ Histoire Naturelle’ (edition of 1801 &c., vol. ix. p. 349), Gadlinace is carefully described as a black semi-transparent glass occurring in Iceland, Ktna, Peru, &c., amid volcanic matter, in a manner that suggests its identity with the sideromelane and palagonite of von Waltershausen. The name is derived from the Gallinazo, a black carrion-bird of the Andes. ¢ Mikrographie der Glasbasalte von Hawaii (Tubingen, 1877), p. 8. ee 2: OCCURRENCES OF TACHYLYTE. 305 magnetite of the rock, the glass being, for a tachylyte, unusually clear. The sections also show the passage of the rock into a stony con- dition by the dense accumulation of spherulites, though alteration has here gone considerably farther than in the vitreous portions. Altogether, this Quiraing fragment presents, in its wealth of detail, the most beautiful example of basalt-glass with which I am ac- quainted (Pl. XI. fig. 3). If we find, however, that this instance exhibits certain phases of alteration, the next example has advanced several stages on the downward path. At an elevated point of the highroad trom New- castle, County Down, west of Bryansford and near the park of Tollymore, a columnar basalt-dyke traverses the Ordovician strata of the district, and is bounded on both surfaces by decomposing tachylyte. This selvage, however, must have at one time resem- bled closely the rock of the Quiraing, although the glassy interspaces are now green in section, and the spherulites a ruddy brown. Cumulites are observable in the thinnest portion of the slide, the magnetite is aggregated into little cubes, and the fibrous structure of the spherulites still remains, the characteristic black crosses with polarized light being easily apparent. A rude perlitic structure and traces of banding traverse the rock; and a few corroded porphyritic felspars have been seized on as centres of devitrification. The numerous vesicles, on the other hand, seem to have had a very partial connexion with the arrangement of the crystallizing par- ticles (Pl. XI. fig. 4). The basalt at the centre of the dyke contains some biotite and a fair residuum of glassy matter; like the rock of Ardtun headland, it has closer relations with the augite-andesites than with the basalts rich in olivine. The extent to which alteration has proceeded in this last case, without the fundamental characters of the rock becoming obscured, and the corresponding retention of original structure among the most ancient and devitrified of acid glasses, leads one to inquire whether tachylytes may not -be identified among the relics of our older volcanic areas. Already Mr. Rutley* has given detailed evidence that the rocks of St. Minver, Cornwall, include vesicular andesite-glass in a state of considerable alteration. As has been often pointed out +, the surface-products and other glassy portions of ancient and denuded lavas are frequently to be recovered among the ashes and detrital deposits formed during the eruptive period. Thus at Snead, near Bishop’s Castle, on the outskirts of the Corn- don volcano, a tuff of Ordovician age occurs, containing numerous black and blue-black fragments which at once recall the glass-particles of more recent areas. The palagonite-tuffs of Sicily, the Kaiser- stuhl, and Iceland, or the glassy tuff of Hilzingen in the Hegau, may be cited as examples of such deposits of later age. The black * Quart. Journ. Geol. Soe. vol. xlii. (1886), p. 392. t H. 9. Jukes, Journ. Geol. Soc. Dublin, vol. viii. p. 32. 306 MR. G. A. J. COLE ON SOME ADDITIONAL fragments at Snead are soft, and devoid of vitreous lustre; but sections go far to prove that they were formerly more distinctly glassy than the tachylytes of Mull or Skye. They are, indeed, from their associations, referable rather to andesite-glass, like the matrix of the well-known rock of Eskdale, than to the rarer and more basic group of tachylytes. Their colour under the microscope varies from a warm brown to yellow, and the relation of this material to the included porphyritic crystals affords very satisfactory evidence. The plagioclase felspars, of the broad type common in andesitic lavas, are corroded and perforated by the yellow matrix; this matrix, moreover, though it now polarizes in streaky irregular areas, has given rise only to minute brown aggregations resembling the magnetite- and pyroxene- microlites formed during the consolidation of basic glass. Some particles of the yellow substance are pumiceous ; and similar material occupies the interstices between the other ejected fragments in the ash (Pl. XI. fig. 5). A comparison with the tuff of Aci Reale, Sicily, in which “ sidero- melane” and palagonite fragments abound, greatly aids one in assigning a vitreous origin to the soft dark particles of Snead. If, further, we examine the andesites associated with this Ordovician tuff, we find an anisotropic substance, clear yellow in thin section, taking the place that in modern examples is occupied by the glassy matrix. Thus in the Corndon area, and, to take another example, in the andesites of the Carneddau Hills near Builth, the cavities of the corroded felspars, and the interstices of the crystalline mesh- work of the ground-mass, are filled with this yellow alteration- product. ‘The interesting augite-andesites of Iceland and the Faroe Islands, with their areas of yellow-brown residual glass, form an admirable series for comparison. It may be claimed, theu, that the tachylytes thus brought together add in some measure to our knowledge of the spherulitic forms; while we have evidence of the persistence of similar types from early Paleozoic up to Tertiary days—evidence, indeed, of the detailed similarity of causes operating at various periods, however far apart intime. I would, in conclusion, call attention to a rock as — yet, I believe, unrecognized in Britain, the Variolite of continental authors. Little need be added to the fulland excellent discussion of its characters given by Prof. Rosenbusch*. The well-known pebbles of the Durance, which are to be found in most old collec- tions, are referred by M. Lory ¢ to the selvages of the euphotides of Mont Genévre, the age of their intrusion being later than the Infra-lias. Delesse ¢ has analyzed the included spherules, and regarded them as a form of triclinic felspar; while M. Lévy § has determined that the fibres of which they are composed are elongated crystals of oligoclase. He points out, moreover, that the * Mikro. Physiog. der massigen Gesteine, 2te Aufiage, p, 227, &c. t Descript. géol. du Dauphiné, p. 577. ¢ Comptes Rendus, tome xxx. (1850), p. 741. § Bull. de la Soe. géol. de France, 1876-77, p. 238. OCCURRENCES OF TACHYLYTE. 307 surrounding matrix possesses a perlitic structure *. The discussion that has arisen as to the amorphous or crystalline condition of the matrix of variolite may be explained if we admit the efficacy of secondary devitrification, and if we regard the rock as having been originally a massive tachylyte. The perlitic cracks, filled with minerals of alteration, are admirably shown in one of the specimens that I have to hand (Pl. XI. fig. 6); and the works published on the selvages of various “ diabase”’ dykes, such as the recent paper on Sordawalite by F. Lcewinson-Lessing +, convince one that developments of basic glass, and even coarsely spherulitic tachylytes, have occurred on the margin of such intrusive masses in the past. In Britain the search for variolite may not be vain; and its dis- covery will give us an indubitably basic rock to set beside the “ nyromerides” that are so well represented in our Isles. I am much indebted to Profs. Judd and Bonney for kind assistance in correlating the foregoing observations. Almost all the sections have been prepared, and the chemical work has been carried out, in the Geological Laboratory of the Normal School of Science and Royal School of Mines. EXPLANATION OF PLATE XI. [The numerator of the fraction expressing the degree of enlargement of an _ object represents the magnifying-power of the objective with which it was viewed. | Fig. 1. Junction of the intrusive sheet of Ardtun with the basalt above it. Section showing bands of spherulites formed in the tachylyte on and parallel to the plane of contact. x22. 2. Section of spherulites with polygonal outlines in the tachylyte of Ardtun. The rays showing the more fibrous structure are of various tints of brown, the intervening areas being greyish. 192. 3. Section showing small spherulites, cumulites, &c., in the tachylyte of the Quiraing. x 292. 4. Section of red-brown spherulites and green-mottled matrix in the altered tachylyte of Tollymore, County Down. x 432. 5. Section of the Ordovician Ash of Snead, near Bishop’s Castle, showing fragments of altered basic glass, which contain porphyritic and corroded crystals of felspar. x %°. 6. Section of pebble of variolite, from an old collection, showing per- litic structure ; the cracks being marked by alteration-products, and the former glassy character of the rock being obscured by secon- dary devitrification. x %. Discussion. Dr. Sorsy referred to the changes which had occurred since he first took up the subject of rocks, and congratulated the Society on the reading of papers like this one. Prof. Bonney also expressed his approval of the paper. He had not been fortunate in finding tachylytes. He could corroborate the Author’s views as to the existence of these basic glasses in the * Ibid. p. 255; also Minéralogie micrographique, planche xxiv. Tt Tschermak’s Mittheilungen, 1887, p. 61. 308 ON SOME ADDITIONAL OCCURRENCES OF TACHYLYTE. older tuffs, but the latter were generally of a more acid character. The specimen of variolite was unusual. This rock occurs wm sztu on the east side of the Durance, near Briangon, in thin dykes. Col. McManon also expressed his gratification at hearing the paper. Prof, Jupp was pleased to think that he had suggested the study of this class of rocks to Mr. Cole. There were, in the paper, many interesting points of comparison between the basic and the better- known acid glasses. Mr. Tratt observed that there was very little to criticize in the paper. He spoke of the interesting generalization to which the Author made his facts point. Mr. Rottey said that the remarkable opacity of this group of rocks, due to disseminated magnetite, often rendered microscopic observations very difficult. He contrasted the structure of the Ardtun rock with that of certain artificially devitrified glasses. It would be interesting to ascertain the relative specific gravity of the spherulitic and non-spherulitic portions. He had seen structure somewhat similar to that of the Ardtun specimen in rocks of the same class from one or two other localities. The AvutHor thanked the speakers for their kind resepttes of his paper. He believed that the occurrence of tachylyte-fragments in the old rocks was no new point. The observation of perlitic structure in variolite was due to MM. Fouqué and Lévy. To Mr. Rutley he replied that spherulites, apparently similar, occur in tachylytes of different compositions. The question of the specific gravity of these bodies presents considerable difficulties. Quart.dourn.Geol. Soe. Vol. XLIV. PLXL. GA J Cole del. West, Newman dz Co.imp. Parker & Coward hth TERTIARY anp OLDER TACHYLYTES. ON THE GNEISSIC ROCKS OFF THE LIZARD, 309 24. On the Gyutssic Rocks off the Lizarp. By Howarpv Fox, Esq., F.G.8. With Norns on the Specimens, by J. J. H. Teatz, Esq., M.A., F.G.8. (Read March 14, 1888.) Ar Mr. Teall’s suggestion, I made, during the past autumn, a methodical examination of the outlying rocks at the Lizard, and forwarded to him series of specimens from the various rocks. They may be classed under three heads :—the coarse gneisses or ‘“‘ Mén Hyr” type, the light banded granulitic gneisses or “ Wiltshire ” tvpe, and the transition micaceous rocks of ‘‘ Labham-Reefs ” type. The annexed map (fig. 7, facing p. 316) shows how these rocks lie with respect to each other and the mainland. The coarse gneisses compose the outer rocks, and the fine gneisses the inner rocks. The transition rocks associate the gneisses with the typical schists of the mainland. Beginning at the extreme west, we find the ‘“ Mulvin ” composed of a dark granulitic gneiss with a strike and dip both clearly con- formable with the rocks of the Lizard Head, the strike being about N.N.W. and $.8.E., the dip E.N.E. The “ Taylor” rocks are a group of three coarse gneissic rocks. The outer of these has a basic porphyritic dyke running across it from the 8.W. to the N.E. with aS.E. dip. This dyke varies in width from one to four feet, and branches at the western end. The middle or main “ Taylor” rock has a small gully on its southern extremity. At low-water spring-tide a basic porphyritic dyke, 18 inches wide, is seen to traverse this gully in an E.N.E. and W.S.W. direction, dipping 8.S.E. The inner “Taylor” rock is mostly composed of a coarse gneiss with some basic bands. The most conspicuous of the outlying rocks are the ‘ Man-of- War ” series, the western end of which towers high above the sea- level and is separated from the next highest, locally known as the “Spire,” by a cleft or gully. The annexed rough diagram, fig. 1, Fig. 1.—“ Man-of-War” Rocks, as seen from the east. S. | N. The black marks represent dykes. A. The cleft in which landing is most easily effected. a is known as the “ Spire.” 310 MR. HOWARD FOX ON THE gives the general outline of the rock and dykes as seen from the east at extreme low water, and fig. 2 as seen from the west. The Fig. 2.—*‘ Man-of-War” Rocks, as seen from the west. Sw K BIS eer b, c. Basic dykes. cleft A is the best place on which to land. A basic porphyritic dyke, from four to five feet wide, is seen to cut the high rock on the left hand. This dyke can be traced round the back of the rock (0, fig. 2), and appears again after a great fault on the south near the water’s edge (c, fig. 2), It has a 8.8.E. dip of about 50°. On the north and western side it is thickly studded with crystals of felspar which occasionally weather outside the ground-mass. On the right hand of the cleft A (fig. 1) stands the “Spire” (a, fig. 1). A basic porphyritic dyke, originally several feet thick, cuts the southern end of this rock. At the top of the “Spire” the strike of the gneiss and dyke appear to be conformable, viz., about N.N.W. and §.S.E. Below this the dyke cuts the gneiss. The dyke weathers out in huge blocks near the top, and in other places forks and branches into veins thinning away to mere threads. Veins of _gneiss occasionally appear to traverse the dyke (see fig. 3), whilst both the gneiss and the dyke are in some places much weathered and altered. Quartz-veins run through both the gneiss and the dykes at right angles. Patches of the dyke are seen adhering to the gneiss on the western summit of this rock, the remainder of the dyke having in that spot jointed out. The gneiss composing the “¢ Man-of-War” rocks is mostly coarse. After repeated and careful observations I believe both strike and dip to be conformable with the Lizard Head schists. When the “ Man-of-War” rocks are viewed from the east or west the strike appears to be about east and west, and this is especially the case with the low ledges to the north of the “Spire.” When, however, they are viewed from the south in a line with the Lizard Head the conformability of the two is seen pretty clearly. The three rocks marked on the 25-inch Parish Map as the “ Stags ” are composed of coarse gneiss. 7 An isolated rock, immediately south of the “ Quadrant,” is locally known as “ Sanspareil.” It is composed of somewhat coarse gneiss with a basic porphyritic dyke running about N.W. and S.E. GNEISSIC ROCKS OFF THE LIZARD. 311 with a S.W. dip. This dyke is thickly studded with crystals of felspar, and it branches and cuts the gneiss in an intricate manner. The original dyke appears to have been about 18 inches wide, and by jointing out to have caused a cleft on the east side of the rock. ! Fig. 3.—Portion of Basic Dyke in the “ Man-of-War” Rocks, traversed by veins of gneiss. fa 4 Ey pice Sas The shaded part is the dyke. The high isolated mass of rock immediately south-west of the mainland is the ‘“‘ Quadrant.” When the sea is calm this island is easily climbed, and the relations of the two basic porphyritic dykes which traverse it can be well studied, free from the barnacles which completely cover most of the other dykes. Approaching it from the south-east the ‘‘ Quadrant ” appears, as roughly sketched in fig. 4, with a dyke cutting the middle, faulted and almost perpendicular. When seen from the north-north-west the rock appears somewhat as in fig. 5. Both dykes are seen here, each about two feet wide, running E.N.E. and W.S.W. with an average 8.S.E. dip of 50°. The northern dyke is a dark basic rock studded thickly with small crystals of felspar. In some places it weathers a glossy black ; in other places she crystals project outside the weathered surface as if peppered on the rock. On the north-east it is abruptly cut off by an open fault or cleft (a, fig. 5). The southern dyke is seen to traverse the highest point in the centre of the island. At the extreme top it appears to be conformable with its gneissic surroundings and to dip at a very high angle towards the east-north-east. It weathers dark grey at this point with crowded projecting crystals, and is itself traversed by a gneissic band 17 inch wide at b, fig. 5. This dyke 512 MR. HOWARD FOX ON THE Fig. 4.—The “ Quadrant” Island, as seen from the south-east. The black bands represent porphyritic basic dykes cutting the gneiss. Fig. 5.—The “ Quadrant” Island, as seen from the north-north-west. The black bands represent porphyritic basic dykes. a, northern dyke cut off by cleft ; b, southern dyke traversed by thin gneissic vein. is faulted below as seen in fig. 6, and resumes its normal diP- The “ Quadrant” is composed mostly of somewhat coarse gneiss, but also of granulitic gneisses and of apparently transition-rocks intermediate between granulitic and actinolitic schists. From the top it appears to be conformable with the Lizard Head schists. The rocks exposed at low water north-east of the narrow channel called Quadrant Drang are known as the ‘‘ Quadrant Shoals.” They are accessible from the mainland at extreme low spring-tides and are conformable with the Lizard Head rocks. Their composition is more basic than that of the “‘ Quadrant.” A dyke two feet wide similar to those on the “ Quadrant” cuts the south-west rocks of these shoals. North-east of the “ Quadrant Shoals” we have ‘‘ Canker Drang,” which is covered with boulders and is dry at spring-tides, and on the north-east of the Drang we have the “ Canker ledges.” The ROCKS OFF THE LIZARD. ole south-west extremity of these ledges shows a fine granulitie rock approaching the “* Wiltshire ” type. Fig. 6.—Southern Dyke in “ Quadrant” Island, faulted on north- west side of extreme summit, The “ Wiltshire” Rock is accessible from the mainland at dead low water. This and the surrounding rocks are composed of a light~ banded granulitic gneiss with sundry exposures of basic porphyritic rocks in their immediate vicinity. The strike of these ‘“ Wiltshire rocks” appears to be north of east and south of west with a southerly dip. “ Shag Rock” is partially gneissic. ‘‘ Mén Par” is an isolated rock of coarse gneiss 450 yards south of Pistil Ogo. The “Clidgas ” are a group of three rocks from 650 to 800 yards south of Pistil Ogo. The inner of these, marked No. 1 on the map, is traversed by two almost parallel basic dykes with erystals of fel- spar scattered sparingly through their ground-mass. These dykes are from 18 inches to 24 inches wide, running N.N.E. and 8.8.W. with an E.S.E. dip of about 50°. These three rocks are all com- prised of coarse gneiss. “ Mén Hyr” and “ Vasiler” are about 900 yards due south of Polpeor Cove, and are both composed of typically coarse gneiss. ** Pen Ervan ” is a boss of somewhat coarse gneiss, with a band of softer micaceous rock at its extreme base on the west. ‘** Enoch Rock,” or ‘“ St. Enoch,” as the fishermen call it, and the Q.J.G.8. No. 174. Y 314 MR. J. J. H. TEALL ON ROCK-SPECIMENS COLLECTED ledges to the north of it, are more basic than the other rocks, and appear to dip 8.W. by W. ‘“‘Labham Rock ” is distinctly gneissic. ‘‘ Labham Reefs,” which can be reached at extreme low water without a boat, are apparently transition rocks, and present in close association rocks in yarious stages of transition from the brown micaceous schists of Polpeor to the distinctly gneissic rocks. The “ Labham Reefs” appear to be conformable with the Lizard-Head schists. All the foregoing rocks are covered at high water excepting Mulvin, Man of War, Quadrant, Wiltshire, Shag rock, and Labham. Some are uncovered only at extremely low spring-tides. Nores on Rock-sPECIMENS COLLECTED by Mr. Fox from the Istanps off the Lizanp Heap. By J.J. H. TEatt, Esq., M.A., F.G.S. Tur two small islands of Mén Hyr and Vasiler lie half a mile due south of Polpeor. A line drawn between these islands in a N.W. by W. direction passes through the Clidgas Rocks, the Man-of-War Rocks, and the Stags. These islands, together with Taylor’s Rocks and Mulvin, which lie slightly to the south-west of the above line, con- stitute what may be termed the Outer Group. Inside these we have Enoch Rock, Pen Ervan, Labham Reefs, Labham Rocks, Mén Par, the Shag Rock, Wiltshire, the Quadrant, and Sanspareil. We will now describe the rocks from the different islands, taking the latter in the order mentioned. Outer GRovupP. Mén Hyr.—A coarse gneissose rock showing a marked foliation. Dark lenticular patches, rich in ferro-magnesian minerals, alter- nate with light-coloured patches of similar form composed of quartz and felspar or pseudomorphous substances after felspar. Under the microscope the rock is seen to be composed essentially of felspar, quartz, dark mica, and hornblende. ‘The felspar is so altered in places as to have lost all individual action on polarized light ; it is then represented either by aggregates of a vividly polarizing scaly mineral (mica) or by patches which appear opaque by trans- mitted, and snow-white by reflected light. The unaltered felspar is abundant in certain portions of the slide; the larger grains are mostly striated. Quartz occurs in grains and granular aggregates. The quartz and felspar in certain portions of the slide exhibit the relations characteristic of igneous rocks ; in others they form a fine- grained granulitic aggregate. Brown mica occurs in scales which are often arranged with their fiat surfaces lying roughly parallel to each other. Hornblende occurs in grains, often elongated in the direction of the vertical axis, but without definite crystalline outline:—a, pale brown ; 3, green; y, bluish-green. Iron-ores and a few small garnets occur as accessory constituents. The rock possesses the mineralogical composition of quartz-diorite FROM THE ISLANDS OFF THE LIZARD. 815 or tonalite, and may be described as a tonalite-gneiss. The granu- lation of the quartz and the felspar in certain portions of the rock is probably a consequence of the dynamic metamorphism which has affected the district. Vasiler.—The specimens are similar to those from Mén Hyr. Clidgas Rocks.—(1) Coarse tonalite-gneiss of the Mén Hyr type. (2) A greenish-black rock (greenstone) with occasional crystals of porphyritic felspar. Under the microscope the porphyritic felspars are turbid and without individual action on polarized light; they lie in a ground-mass of hornblende and granulitic water-clear felspar. Grains of iron-ore and a few yellow prisms and twins of rutile are also present. The hornblende forms the greater portion of the mass; it occurs in extremely ragged patches and only here and there shows traces of crystalline form. The terminations of the longer patches sometimes run out into actinolitic needles. The granulitic felspar plays the réle of matrix to the hornblende. The individual grains are as a rule untwinned, but the larger of them occasionally show striation. The hornblende is probably secondary after augite, and the rock may be termed a porphyritic epidiorite. _ Man of War.—(1) Coarse tonalite-gneiss. A specimen from the east end of the Post differs from the one described from Mén Hyr only in containing more hornblende and garnet. The latter mineral occurs in well-formed crystals. (2) Porphyritic greenstone (epidiorite) and actinolite-schist. Mr. Fox’s sk@tches show that the rock-masses have been deformed since the dykes were intruded. We find evidence of this in the dykes themselves. In one specimen the greenstone, near its junction with the gneiss, has become a felspathic actinolite-schist. The actinolite-schist differs from the epidiorite of the Clidgas in possessing very perfect schistosity and foliation, and in having the whole of its hornblende in the condition of actinolite. The porphyritic felspars form “eyes” in the actinolitic schist. Tayior’s ock.—(1) Gneiss. A section of one of the coarser gneisses from this island shows an irregular granulitic aggregate of quartz and felspar, the latter often striated, and actinolitic horn- _ blende, which may be either brown, green, or nearly colourless. lron-ores, garnets, and zircons occur as accessories. This rock differs from the tonalite-gneiss of the Mén-Hyr type in the extent to which the granulation of the quartz and felspar has been carried on. It might on this account be designated a granulitic gneiss, ‘reserving the term granulite for a rock in which the quartz and felspar are present wholly in the form of a micro-crystalline mosaic of fairly uniform grain. (2) Porphyritic greenstone (epidiorite). The Stags.—(1) Moderately coarse-grained tonalite-gneiss con- taining garnet and sphene as accessories, and having the foliation imperfectly developed. (2) Light-coloured, fine-grained granulite or granulitic gneiss, with well-marked foliation. 316 MR. J. J. H. TEALL ON ROCK-SPECIMENS COLLECTED (3) Dark-coloured, fine-grained granulite or granulitic gneiss. The last-mentioned rock is largely composed of a fine-grained micro-crystalline mosaic of quartz and felspar, in which needles of actinolite lie imbedded. Iron-ores are fairly abundant. Certain bands are rich in turbid felspar-pseudomorphs and larger grains of hornblende, so that the rock is not a typical granulite. Mulvin.—Dark-coloured, fine-grained granulite or granulitic gneiss similar to the rock just described from the Stags. Inner GRovP. Enoch fock.—Coarse hornblendic schist and gneiss (without quartz), quite distinct from the tonalite-gneiss and having elose affinities with the hornblende-schist of the mainland. Pen Ervan.—(1) A somewhat fine-grained, evenly foliated tonalite- neiss. : (2) Brown micaceous rock, similar to the transition rocks of Labham Reefs. Labham Reefs—(1) Light-coloured or brewnish granulite or granulitie gneiss. (2) Brown micaceous schistose rocks intermediate in character between the granulitie rocks of the islands and the mica-schists of the mainland. Labham Rock.—(1) A finely crystalline pinkish granulitie rock without well-marked foliation. Under the microscope this rock is seen to consist principally of quartz and turbid felspar. It contains also a very little hornblende and a few grains of epidote. The granulitic structure is well developed in places. A narrow vein containing much epidote traverses the slide. (2) A rock similar to the above, but somewhat richer in the darker constituents. Under the microscope turbid felspars (original ?) are seen to lie in a granulitic aggregate of colourless quartz and felspar (secondary?). Long needles of actinolite le in the granulitic material, This rock possesses, in a certain sense, the ‘“ mortar- structure” of Térnebohm. It is, however, the “ mortar” and not the ‘‘ stones ” that constitutes the greater portion of the mass. (3) A banded and corrugated granulite or granulitic gneiss. Mén Par.—Tonalite-gneiss of the Mén-Hyr type. The Shag Rocks.—Rocks similar to those from Labham. Wiltshire.—(1) Light-coloured, banded granulite, showing a finer foliation than that of Labham, but belonging to the same type. (2) Granulite of the same colour, but without conspicuous banding. Under the microscope this rock is seen to consist principally of quartz and felspar, the latter mostly unstriated. Ferro-magnesian coustituents are sparingly represented by a little green mica. The micro-structure of the rock is thoroughly granulitic. The Quadrant.—(1) Granulite of the Wiltshire type. One spe- cimen contains garnets and a little hornblende. (2) Porphyritic greenstone (epidiorite). Sanspareid.—(1) Granulite without well-marked banding, com- ©. J. G. S. vol. [To face p. 316. d Reefs. The Scale " (IN ,HYR Z o THE DALES S a Q. J. G. §, vol. xliv.] [To face p. 316, Fig. 7.—Sketch Map of the Lizard and adjacent Rocks and Reefs.. LIZARD HEAD UADRANT SHO! A % -f; Q S eS. ue = se oa? Ox uk SZ KW 4 az EC inteny Ns ) y S D ( A’ Ay das De Ps Dol (a) WILTSHIRE ? QUADRANT Yy 3° & % () 7) .ys 9, 6 SANSPAREIL dQ» 4, fc) MULVIN 3 a S Pe “Dp ee OF WAR Bes ‘ENOCH E oss 7 Ww .o) Xp é | ® | CLIDGAS ro or] S a The Scale is 8 Inches to the Mile MEN HYR ——eeeee———— £2 P 4 THE DALES VASILER, 5 2g7 o = - eo ee Se a et FROM THE ISLANDS OFF THE LIZARD. S17 posed of a granulitic sEurSEpe of quartz and felspar, actinolite, and garnet. (2) Porphyritic Re pe (epidiorite) precisely pimullar to that described from the Clidgas. GENERAL CoNCLUSIONS. (1) The outer islands consist largely of coarse gneisses. (2) The parent rock of these gneisses may have been an eruptive quartz-diorite or tonalite. (3) The inner islands consist largely of granulites and granulitic gneiss. (4) Associated with the gneisses and granulites are metamor- phosed basic eruptive rocks in which porphyritic crystals of felspar are frequently present. (5) The relations of these basic eruptives to the surrounding rocks have been much disturbed by the forces which have deformed the rock-masses in this district. (6) The petrographical characters of the rocks themselves have been affected by these deforming forces, and actinolite-schist has been locally developed out of the intrusive greenstone. (7) Some of the rocks of the Labham Reefs are intermediate in character between the granulitic rocks of the inner group of islands and the mica-schists of Polpeor. (8) The period of dynamic metamorphism, of which the most striking results are seen in the schists of the south-western portion of the Lizard peninsula, was posterior to the formation of the basic dykes. There is no evidence of igneous action in this district since the period of metamorphism. Discussion. Prof. Bonyry spoke in high terms of the value of the work, done, as it was, in a region accessible with difficulty, which time did not permit him to explore when working at the rocks of the main- land. The gneissose rocks are such as he would on @ priort grounds have expected to find there, and somewhat resemble the gneiss of the Eddystone Rock. He considered that two structures occurred in the Lizard rocks—an older one, to which some would refer the apparent stratification of the rocks of the country, of a date long anterior to Ordovician times; and a later one, whose exact age is unknown, which seems to have acted with much energy nearly parallel with the coast-line, which very possibly is near a fault. The Rev. E. Hitt added his testimony to the extreme diligence required to elucidate an area such as that described. 318 MR. H. J. CARTER ON SOME VERTEBRATE REMAINS IN THE 25. On some VERTEBRATE Rematns in the Triasstc Srrata of the Sour Coast of DevonsHire between BuDiEteH SALTERTON and Srpmourn. By H.J. Carrer, Esq., F.R.S. (Read February 29, 1888.) (Communicated by A. T. Mzrcatre, Esq., F.G.S.*) [ Abridged. ] In August last my attention was particularly called by the late Dr. John Millar, F.G.S., to the microscopic structure of the remains noticed by Mr. Metcalfe under No. 11 in his paper ‘“* On further dis- coveries of Vertebrate Remains in the Triassic Strata of the South Coast of Devonshire” 7. These are small pellet-like amorphous bodies, averaging from } to 4 inch in diameter, composed of white calcareous matter, traversed in all directions by semitransparent crystalline plates showing bone-structure. These pellets occur plentifully in the fallen blocks of Triassic rock on the beach, which contain the remains of Labyrinthodonts &c. Dr. Millar remarked that they very much resembled coprolites and were identical in appearance with some in his possession from the Lias, which he would send me for comparison. T had previously observed that the contained plates, when examined in water under the microscope, presented the same bone-structure as the scales of the Bony Pike of North America (Lepidosteus osseus), as shown by Prof. Quekett in his ‘ Lectures on Histology’; and on grinding down a fossilized Lepidostean scale from Hordwell, Hants, I found its structure to be exactly like that of the recent species. On breaking up some of the pellets (which are formed of concentric layers), I found a fragment representing the angular part of a scale, on which the same agatoid lines of growth were visible as on the ganoid scales from Hordwell. The slides of Ichthyosaurian coprolites sent to me by Dr. Millar showed sections of the same kind of plates with the same character- istic bone-structure, so that it became evident that the Ichthyosau- rians of the Lias and the Amphibians of the Triassic age fed upon the same kind of Ganoid fish, whose scales, being too hard for digestion, have remained in the coprolites. The plates of the Sturgeon present the same kind of bone-struc- ture, viz. large lacunze, which, when compared with those of Reptiles, Amphibia, &c., are seen to be provided with longer and less numerous canaliculi, elegantly waved and dendritically branched. As regards the bone-structure of the so-called “Spine,” No. 1 (loc. cit. p. 260, fig. 2), and that of the middle part of the jaw-bone * This paper is supplementary to one on the same subject read by Mr. A. T. Metcalfe before the Society on January 9, 1384, and published in the Quarterly Journal of the Society, vol. xl. p. 257. T Loc. cif, p./261. { Vol. i. p. 174, fig. 136. TRIASSIC STRATA OF THE SOUTH COAST Of DEVONSHIRE, 319 of a Labyrinthodont, No. 2, there appears to me to be no difference between this and Reptilian bone-structure generally. It is totally different from that of the Lepidostean scale. Lastly, as regards the above-mentioned spine, having examined generally and microscopically the spines of two species of Hybodus, I have to state that not only are the latter hollow and the former solid, but the bone-structure is quite different in the two cases ; thus I can see no lacune at all in the spines of Hybodus, although there are canaliculi. Hence, whatever this fossil may be, we have no grounds for regarding it as a “ spine.” Discussion. The PresipEnt observed that perhaps the most interesting remark in the paper was that relating to the so-called spine of Mr. Metcalfe’s paper. Mr. Smita Woopwarp said that or a former occasion he had suggested that the spine was the premaxilla of Wyperodapedon (see p. 163). He still adhered to that view. Mr. Wairaxer commented upon the complete destruction of the fish by the reptiles of the Triassic age. Q.J.G.8. No. 175. Z 320 MR. W. HILL ON THE LOWER BEDS OF THE UPPER 26. On the LowER Bens of the Upper Cretaceous Serres in Lin- COLNSHIRE and YorKsHIRE. By Wittiam Hit, Esq., F.G.S. With the Description of a New Species of Hotaster, by A. J. JuKES-Browne, Esq., F.G.8. (Read April 11, 1888.) [Puate XIT.| Unit recently no attempt had been made to describe the zonal divisions of the lower beds of the upper part of the Cretaceous series in Lincolnshire. Indeed, Prof. Judd remarked in 1869, “ The time has not yet come for separating the great mass of the Chalk forma- tion in this county into zones,....such a task not having been accomplished in the best-explored districts of the Chalk” *. In 1876 Dr. Charles Barrois tT, having been unable to visit this county, follows, in his well-known work, the description given by Prof. Judd. It was not until the publication, in the spring of 1887, of the “ Geology of part of East Lincolnshire,” a memoir of the Geological Survey, that a systematic attempt was made to correlate any part of the Chalk of Lincolnshire with that of the more southern counties of Cambridgeshire, Hertfordshire, &c. But the author of this memoir laboured under a disadvantage ; for, as he remarks (p. 28), ‘The zones of the latter county [Cambridge] have not yet been traced northward into Norfolk, where the Chalk begins to put on what may be termed the northern or Lincolnshire facies; the data requisite for the proper correlation of the two areas are therefore incomplete.” And again (p. 31), ‘‘ As yet we know nothing of the changes which the Chalk zones undergo in their passage from Cambridge to Norfolk; and in the absence of this connecting stratigraphical evidence, the correlations now suggested are not to be received as a decided expression of opinion.” But while this memoir was in the press, Mr. Jukes-Browne and myself undertook the investigation of the lower part of the Chalk in Suffolk and Norfolk, the results of which have already been published f. We therefore now possess that connecting-link of stratigraphical evidence which was wanting when my friend and colleague in the Norfolk paper completed the Memoir for the Geological Survey on East Lincolnshire ; and it seemed to me almost as much a duty as a pleasure to carry forward the knowledge obtained by the study of the Chalk in Suffolk and Norfolk, and apply it to the same series of the Cretaceous system in Lincolnshire and Yorkshire. The Chalk of Yorkshire has been the subject of several papers. The Rev. Prof. Wiltshire § has given a brief description of the Speeton cliffs, written before the main divisions of the Chalk were * Prof. J. W. Judd on “The Lincolnshire Wolds,” Q. J. G. S. vol. xxiii. p. 235. + C. Barrois, “ Recherches,” &c. Mém. Soc. Géol. du Nord, vol. i. p- 189. t “ On the Lower Beds of the Upper Cretaceous Series in Suffolk and Norfolk,” a A. J. Jukes-Browne and W. Hill, Q. J. G. S. vol. xliii. p. 544. § Wright's ‘Mon. Brit. Fossil Cretaceous Echinodermata,’ p. 8. CRETACEOUS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 3821 Fig. 1.—Sketch-Map of the Outcrop of Cretaceous Rocks in Lincoln- shire and Yorkshire. (Scale 15 miles to 1 inch.) \ S\N ES \ BAK behade! Siiisiiisii? \ AK Alluvium. [Ea Challe. “] Neocomian. Jurassic. Trias. o22 MR. W. HILL ON THE LOWER BEDS OF THE UPPER understood. It contains, however, valuable information. Mr. Meyer* has also contributed a short paper on the Red Chalk of Speeton. Dr. C. Barrois + visited Yorkshire in 1875, but he states that his time was limited. He describes very briefly the interior of the county, but speaks at greater length of the section at Speeton. He correlates the lower beds of the Upper Cretaceous series with those of the South of England; but the absence of information concerning the changes which these beds undergo as they are followed north from Cambridge, and the misconception (since corrected) which he formed as to the position of the Totternhoe Stone, appear to have affected his judgment as to the thickness and sequence of these beds both at Hunstanton and in Lincolnshire and Yorkshire. He appears, however, to acquiesce in the greater extension of the zone of Holaster subglobosus at Speeton in his criticisms t on the paper by Prof. J. F. Blake. Prof. J. F. Blake § has contributed a valuable paper in which he describes the whole of the Chalk of Yorkshire. He correlates it with the divisions of the South of England in a general way and discusses the classification of it as adopted by Dr. Barrois, for whose criticisms thereon see note +. Much information on the Lower Chalk of Yorkshire is given in three small Memoirs of the Geological Survey ||, but the correlation of it with that of Lincolnshire is not attempted. A detailed description of the lower part of the Speeton cliffs may be found in Phillips’s ‘ Geology of Yorkshire.’ The measurements given differ but slightly from my own, but no two observers seem to agree exactly in the amount of coloured and uncoloured Chalk seen here. This may be the result of taking colour-lines as the basis of measurement; they will be shown in the sequel to be un- trustworthy guides. I must thank Mr. Jukes-Browne for his cooperation in the correlation of the Norfolk and Lincolnshire series, and for giving me the benefit of his knowledge of the latter county, thereby saving me much time and labour in the field, and also for the description appended of a new species of Holaster. And I am also much indebted to Mr. C. Fox-Strangways, who gave me every assistance in the investigation of the Lower Chalk of Yorkshire, and to Mr. Goodchild for the accompanying sketch map (fig. 1). § I. LincotnsHire. Stratigraphy. From the results of recent work in Suffolk and Norfolk] it * Geol. Mag. vol. vi. p 169. t ©. Barrois, “ Recherches sur le terrain Cretacé Supérieur de l’Angleterre et de ’Irlande,” Mém. Soe. Géol. du Nord, vol. i. p. 191. t Proc. Geol. Assoc. vol. vi. p. 165. 5 ac J. F. Blake, ‘On the Chalk of Yorkshire,” Proc. Geol. Assoc. vol. v. r || Geol. of York and Hull, Geol. of Driffield, Geol. of ‘Scarboro’: Mems. Geol. Survey. 4 Q.J.G.S8. vol. slit. p. 544. CRETACEOUS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 323 appears that, in spite of greatly reduced thickness and considerable lithological change, the zonal divisions of the lower beds of the Upper Cretaceous series in these counties agree with those established in the Midlands and South of England. It is shown, in the paper referred to, that the Melbourn Rock is continuous from Newmarket to Hunstanton, thus defining the upper limit of the Lower Chalk, although the Belemnite-marls were found to die out; that the Grey Chalk became thinner and harder as it was followed northwards; that the Chalk Marl passed laterally into a pure and very hard chalk, its summit, however, still marked by the Totternhoe Stone, which, like the whole series, shared in a general attenuation. The Cambridge Greensand was found to die out gradually, and the Gault, also thinning and becoming more cal- careous, appears to be represented in the extreme north-west corner of Norfolk by the Red Chalk or Hunstanton Limestone, the so-called ** Sponge-bed ” overlying it being included in the Chalk Marl (see Section I. p. 366). The very full and minute details concerning the Chalk, published in the “* Geology of part of Hast Lincolnshire” *, render it scarcely necessary to do more than review the Lower Chalk of this county, adding only the results of my own work which confirm and strengthen the opinions of Mr. Jukes-Browne, and noting such facts as may be of service in the correlation of the series in Yorkshire. The Lower Chalk of Lincolnshire is divided in the Memoir into two portions, which are considered separately, viz. a lower, which includes, besides the basement-bed of Red Chalk or Hunstanton Limestone, some 36 feet of rough greyish-white chalk, and an upper portion, about 40 feet, which contains locally some pink bands, the line being drawn about 7 feet below the lowest of these f. The summit of the Lower Chalk is fixed at certain marly bands which are considered to be the representatives of the Belemnite- marls of Cambridge, Hertfordshire, &c. This division so nearly corresponds with my own reading of the strata, that it will be convenient to follow the Memoir in discussing the Lower Chalk of this county, separating only the basement-bed of Red Chalk, which has been shown to be the probable equivalent of the Gault. It is fortunate that in South Lincolnshire, near Welton, at a point nearest to the Hunstanton cliff, there are pits which give almost a complete section of the lower beds of the Upper Cretaceous series. It will be seen from the accompanying diagrams (facing p. 366), and by reference to the text, that there is a remarkable similarity in the Sequence of the beds at both places; certain points of difference will be noted in the sequel. The sequence and general character of the various beds seen in * Mem. Geol. Survey, Sheet 84. + This division was only adopted for the sake of convenience in describing the exposures. In the fossil lists the Lower Chalk is divided into three portions, a lower, central, and upper, the division-line between the central and upper parts being taken at the base of the pink band. 324 MR, W. HILL ON THE LOWER BEDS OF THE UPPER ~ the chalk here extends throughout Lincolnshire and Yorkshire. I propose, in this county, to deal with each separately, and note any important difference which may occur further to the north, or help in the correlation of the Yorkshire series. The diagram No. II. is drawn up from sections exposed in the following pits :—that worked by Mr. Rutter 7 mile 8.8. W. of Welton Mill, at the cross roads on the west side of the road to Candlesby (page 44 of the Memoir); the pit on the opposite side of the road to the Cross Keys Inn, close by the first and forming with it a continuous section ; lastly, a pit 4 mile west of Welton and 7 mile N.N.H. of the Mill (page 51 of the Memoir). (A.) Red Chalk or Hunstanton Limestone. This bed, continuous throughout Lincolnshire, is about 11 feet thick at the southern extremity of the Wolds. It retains this thickness to the north of Louth, but diminishes to 4 feet in the northern part of the county. It is the “ amplified counterpart” of the Hunstanton Limestone. Its base seems invariably to partake of the nature of the underlying material, and it is frequently difficult to say exactly where the Red Chalk begins. It passes up into rough and rather nodular chalk with marly partings, and its summit is frequently, though not always, marked by a thin band of red clay, which separates it from the pinkish or yellowish-grey chalk, the equivalent of the so-called Sponge-bed of Hunstanton, which over- lies it. The list of fossils given in the Memoir from this bed is a short one, and I can, with one important exception, add little to it. Belemnites minimus, which occurs commonly in the Gault and Hunstanton Limestone of Norfolk, is also abundant in the Red Chalk of this county, occurring throughout it, though individuals are more abundant near the base. Jam fortunate, however, in being able to add to the list Ammonites interruptus from Witheall, a fact which considerably strengthens our expressed opinion that this bed is the equivalent of the Gault. (B.) Lower Chatk.—Chalk Marl. The Chalk Marl, as before noted, alters its lithological characters and becomes thinner as it is followed northward. At Hunstanton its base is recognized in the so-called Sponge-bed, which is followed by the grey and gritty Inoceramus-bed, with a layer of green-coated nodules at its base. This, passing up into hard whitish chalk, is finally overlain by a marked course of grey-coloured chalk, also with green-coated nodules at its base. This bed, the representative of the Totternhoe Stone, marks the summit of the Chalk Marl, and the fauna obtained from this division will compare with that from the upper part of it in Cambridgeshire, Hertfordshire, &c. ‘¢ Sponge-bed.”—The pinkish or yellowish-white chalk which im- mediately overlies tle Hunstanton Limestone in Lincolnshire, and is CRETACEOUS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 325 the equivalent of the “‘Sponge-bed,” retains its character as a thin band of compact limestone, differing somewhat in appearance and fracture from the overlying beds, not only through this county but far into Yorkshire. It is generally thicker in Lincolnshire than at Hunstanton, and the line of separation from the underlying bed is not always so well marked as in the Hunstanton cliffs. Inoceramus-beds.—Grey in colour and gritty to the touch, the next 5 or 6 feet of the Chalk are usually compared with the [nocera- mus-beds of Hunstanton. Here the bed appears to me rather more nodular in its character than its. Norfolk equivalent, the nodules being of a less gritty material than the surrounding matrix. A marked layer of green-coated nodules occurs about 6 inches above the top of the Sponge-bed in the various pits near Welton. The base of the Chalk appears to retain this gritty character throughout the county. The greater part of the Chalk, for some 30 feet above the basement-bed in this county, may be described as rough and nodular ; this division, however, contains courses of smoother chalk, for ex- ample, the ‘‘ blue course” (Mem. page 43), near the base, and others near the summit, where the chalk is divided into courses by more or less marked bands of greenish-grey marl. The section recorded in the Survey Memoir at Mr. Rutter’s pit near Welton (see Section II. p. 366) is that of the face of the quarry which is still worked ; but a little to the north of this, in the older part of the workings further up the slope of the hill, the section can be carried higher. The platy chalk with marked marly bands, the uppermost bed in the section given, can be followed round the pit and seen to continue for about 4 feet more upwards. (C.) The Grey Bed.—The equivalent of the Totternhoe Stone. Overlying the Chalk just described a bed with strongly marked characters occurs. This is about 3 feet thick, sometimes in more than one course, and of rough rather nodular massively bedded chalk, its darker grey colour showing plainly by contrast with the whiter material above and below. Its base, in which there are many pale yellowish green-coated nodules, is here not well defined, the greyer material being let down in pipes and mottlings into the whiter chalk below; in Central Lincolnshire the lower 6 inches will frequently weather and split into thin flaky pieces, and a band of grey marl forms a line of division from the underlying chalk, which for about a foot down is often hard and “knobbly.” It passes up into a course of hard, nodular, and whiter chalk, the top of the bed not being well marked. It is very fossiliferous, and the fauna which I have collected from it is characteristic of the Totternhoe Stone (see page 349), and its structure, when seen in thin sections under the microscope, will compare with that of this stone. The ‘Grey Bed ” I believe to be without doubt the continuation of that which marks the summit of the Chalk Marl at Hunstanton, and therefore it is the representative in Lincolnshire of the Tottern- 326 MR. W. HILL ON THE LOWER BEDS OF THE UPPER hoe Stone. This bed, which is formed by the basal courses of ‘‘ nodular grey chalk underlying the lower pink course” *, is always well marked throughout the county by the characters noted above, as well as by the chalk which lies beneath and above it. In the following details I indicate its position in the sections described in the Memoir, and give other sections to the north of the_ area included in it. Besides Mr. Rutter’s pit at Welton, the “Grey Bed” is seen in a pit just on the other side of the road, opposite the Cross Keys Inn, at the north corner of which the following succession was measured (page 44 in the Memoir) :— ft. Thin-bedded rubbly chalk with persistent layers of shaly buff-coloured marl, containing Tere- DratWind Gracies” ig ..0.a.000 000+ onae BEN UIONE GLASVEN HEAD oF OCLENBEG RECENT WORK OF THE GEOLOGICAL SURVEY : S = iS) = Silurian zones from the basal quartzites up to the limestone are repeated by thrusts of more or less magnitude, till we reach the maximum thrust which brings in the green schists and sheared gneiss with strips of highly altered quartzites, These are overridden in turn by the micaceous flagstones above the Moine Thrust-plane. | On the southern slope of Quinaig (fig. 13) the unconformability between the quartzites and the Cambrian sandstones is well exposed in the great escarpment skirting Loch Assynt, the sandstones being nearly flat, while the quartzites are inclined to the E.S.E. at angles varying from 15°-20°. Both zones are succeeded by the ‘‘ Fucoid-beds” and Serpulite-grit in natural order ; but close © to the highroad leading to Kylesku the strata are truncated by a major thrust- plane, along which the “ Fucoid-beds,” Serpulite-grit, and basal limestones have been driven, repeated by numerous minor thrusts. Generally the piled-up strata belonging to these horizons are tilted at high angles to the plane of the major thrust. Owing to the extraordinary number of these minor thrusts, there are no fewer than thirteen outcrops of the Serpulite-grit in the course of one third of a mile. Close to Achumore another powerful major thrust ushers in the basal limestones, lying at gentle angles and resting on the highly in- clined thrust-strata just described. They are repeated by numerous minor and major thrusts, and thrown into a series of arches and troughs, as shown in sec- tion, till they are overridden by the materials brought forward by the Glen- coul Thrust-plane. The outcrop of this thrust-plane has been traced con- tinuously from the shore of Loch Glen- coul, southwards by Loch na Gainmhich along the base of the western slope of Glasven, to the Poll an Droighinn burn, thence by the base of Ben Fhuarain and Coinne-mheall of Ben More, till it is eventually overlapped by the Ben-More os IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 419 Thrust-plane. For several miles of its course, from a point near Loch na Gainmhich to Cnoc an Droighinn, this maximum thrust brings various members of the quartzites to overlie different sub- divisions of the Ghrudaidh and Eilean Dubh limestones. These quartzites have been driven westwards with the great slice of Archean rocks above this thrust-plane, the latter rocks being ex- posed, with their characteristic basic dykes, to the north of the Chalda Lochs. But it ought to be borne in mind that the quartz- ites along the western face of the disrupted gneiss do not lie in regular inverted order: they are traversed by numerous thrusts, bringing different subdivisions of the quartzites with their intrusive sheets against each other. The extreme complications resulting from these minor thrusts and subsequent folding in the quartzites and their associated igneous rocks are splendidly displayed in Cnoc an Droighinn near Inchnadamff. Between Glasven and Ben Uidhe there is a powerful maximum thrust driving westwards the Archean gneiss with the basal quart- zites and the “ pipe-rock,” while on the crest of the latter mountain both zones of the quartzites are repeated by various thrusts. On the northern shoulder of Mullach an Leathaid Riabhaich several powerful thrusts and extraordinary flexures of the strata are met with, until we reach the horizon of the Ben-More Thrust-plane, at the head of Glenbeg. The Limestone Plateau at Inchnadamff.—The great development of Silurian limestone at Inchnadamff occurs almost wholly within the area affected by the Post-Lower-Silurian movements. Indeed it is rather remarkable that only one small patch, belonging to the lower subdivision of the Ghrudaidh group, lies in the undisturbed area, viz. on the north shore of Loch Assynt near the mouth of the Skiag burn. Between Achumore and Inchnadamff the belt of limestone is nearly a mile wide, but to the east of the great Stronechrubie cliff it forms a broad plateau about two and a half milesin width. As indicated in the foregoing vertical Section II. (p. 406), the beds belong mainly to the two lowest groups of the Durness limestones, only a small portion of the Sailmhor group being represented. Owing to the extraordinary complications of the strata, due to the number of minor and major thrusts, it is difficult to estimate accurately the thickness of the lime- stones, but 1t cannot exceed 450 ft. or 500 ft. That the calcareous beds are not arranged in an inverted synclinal fold can be demonstrated in the most conclusive manner. Taking first that portion of the plateau between Inchnadamff and Achumore, the following horizontal section (fig. 14) shows the general relations of the strata. Starting from the shore of Loch Assynt, about half a mile north of the mouth of the Traligill, the “ Fucoid-beds,” Serpulite- grit, and a portion of the basal limestones are repeated by numerous minor thrusts, till we reach a powerful major thrust-plane, along which the Eilean Dubh hmestones have been driven westwards, over the underlying Ghrudaidh Group. Within a distance of half a mile of the shores of the Loch, the piled up limestones are trun- cated by another major thrust, bringing up the ‘“ Fucoid-beds,” Ser- pulite-grit, and basal limestones to overlie the Hilean Dubh beds. 420 RECENT WORK OF THE GEOLOGICAL SURVEY This powerful thrust can be traced northwards to the Chalda burn and southwards across the Poll an Droighinn and Traligill burns to the great plateau east of Stronechrubie. Following the line of " Fig. 14.—Horizontal Section from Loch Assynt, across the Silurian Limestones, to Croc an Droighinn. (About 2 mile in length.) ; cnoc an DRL \t sw LOCH ASSTNT ( AVS Tis > section east to Cnoc an Droighinn, various subdivisions of both the lowest limestone groups with their dykes are repeated by reversed faults, till they are overlapped by the “‘ pipe-rock” above the Glencoul — Thrust-plane. Between Ardvreck Castle and Achumore the relations of the strata are still more complicated. Briefly stated, the principles involved in the structure are as follows:—(1) the occurrence of a series of major thrusts running roughly parallel with each other, producing great horizontal displacement ; (2) the piling up of the limestones along the planes of these thrusts by minor reversed faults; (3) the subsequent arrangement of the strata in a series of gentle arches and troughs, the axes of the folds being quite independent of the trend of the major thrust-planes. Precisely the same principles are illustrated in the broad plateau east of Stronechrubie. The first great major thrust in the limestone is well seen in dip-section in the great cliff about half a mile south of the Inchnadamff Hotel, where it drives forward the Eilean Dubh limestones, the latter dipping at a high angle to the plane. Again, on the slope south of the Traligill burn at Glenbain about six major thrusts are admirably seen in dip-section, the beds between these planes being piled up by minor reversed faults. Occasionally outliers of the “ Fucoid-beds ” and Serpulite-grit are found, capping the Eilean Dubh limestones in the north-east part of the plateau, se- parated from each other by major thrusts. But subsequent to these various displacements driving the strata together, the area along the north-eastern and eastern margins of the limestone-plateau was elevated in the form of a great dome; and hence we find, at inter- vals, various sections showing the natural passage from the “ pipe- rock ” to the “Fucoid-beds,” Serpulite-grit, and basal limestones, the strata being inclined towards the west. This feature has given rise to the belief, advocated by several observers, that the limestones were arranged ina great synclinal fold. But the examination of the great quartzite range of Braebag, to the east of the limestone plateau, points to the conclusion that the quartzites were piled on each other by numerous thrusts prior to the formation of the great IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 491 anticline. Along the western side of the arch, where the quartzites and limestones dip to the west, the thrust-planes are inverted, so that the observer has, metaphorically, to stand on his head to realize the effect of the displacements. Geological Structure of Ben More.—Along the line of complicated structure between Eriboll and Ullapool, Ben More stands unrivalled for the extreme intricacy of the geological relations of the strata, for the striking evidence in proof of the existence of two maximum thrust-planes, and finally for the brilliant light which it throws on the metamorphism induced by these mechanical movements. This mountain has two peaks, one, Ben More (3278 ft.), the other, about a mile to the west, named Coinne-mheall (Coniveall) (3234 feet). Between the latter peak and Braebag there is a col or narrow pass termed the Bealloch, separating the head-waters of the Oykel from the sources of the Traligill. In order to illustrate the structure of the mountain, we propose to describe three horizontal sections traversing it in various directions (figs. 15, 16, 17). Fig. 15.—Seetion across Coinne-mheall from one of the sources of the Traligill east to Corrie Mhadaidh. (About 14 mile in length.) S.W. Coinne-mheall. N.E. Fig. 16.—Horizontal Section from the Bealloch across Coinne-mheall , to Corrie Mhadaidh. (About 14 mile in length.) 8.S.W. Coinne-mheall. N.N.E. K Sate. SSO alle k El |S mn het ; SS Aahanaat ER te ag LUNA TEATS TUT TN et We \ YE AN SOs. SOS SX; ASS > 6 € CH7t5s6 HESS 5 r] Beginning at the base of the western slope (fig. 15), both the zones of the quartzite, the false-bedded grits, and “‘ pipe-rock” are driven on to the Silurian limestone by the Glencoul Thrust. Ascending the slope, the false-bedded grits are made to overlie the ‘‘ pipe-rock ” by means of a reversed fault, and for some distance upwards, to near 4992 RECENT WORK OF THE GEOLOGICAL SURVEY the 2500 feet contour-line, the strata exposed in the stream-section consist wholly of the lower zone of quartzites with their dykes, repeated by inverted folds and minor thrusts. Indeed, from the various arches exposed, it is clear that the basal quartzites only form a thin veneer over the concealed Archean rocks. Were the slope denuded further back, there can be no doubt that the latter. would be revealed. About the 2500 feet contour-line the basal quartzites are followed in regular order by the various subdivisions of the “pipe-rock,” with their intrusive sheets, and the “ Fucoid-beds,” until they are abruptly truncated by the great Ben-More Thrust- plane. At the point where this line of section is drawn the effect of this maximum thrust is to bring the basal quartzites to overlie the highest zone of the “‘ pipe-rock” and “ Fucoid-beds.” When the false- bedded quartzites (Zone 1) are traced along the crest of the moun- tain they are found to overlie unconformably both the Cambrian sandstones and the Archean rocks. The false-bedded quartzites are succeeded by. the lowest subdivision of the ‘“‘ pipe-rock,” ex- posed on the mountain top. Descending the north-eastern slope of Coinne-mheall (fig. 15), the observer crosses (1) the unconformable junction of the basal quartzites and the Cambrian sandstones, and (2) the boundary line between the latter and the Archean gneiss. Owing to the high inclination of the Ben-More Thrust-plane at — this point, the outcrop descends from the crest of the mountain to the Bealloch, where it is well seen on the great cliff in dip- section. As a result of the friction along the unyielding “sole” of the thrust, causing the upper layers to move more rapidly than the lower, we find that the Cambrian sandstones fold over the western face of the disrupted gneiss, as shown in the foregoing section (fig. 15). By means of the local conglomerate (‘‘ the Button-stone ”) at the base, the line of junction with the old Archean platform is easily traced, and the proof of inversion is beyond all doubt. The basal conglomerate and the overlying grits, sandstones, and shales can be followed continuously from the Bealloch, round the south-eastern spur of Coinne-mheall, to the southern shoulder of Ben More, where they are unconformably overlain by a cake of the basal quartzites. That these grits and sandstones are really a portion of the Cambrian sandstones to the west, as originally maintained by Prof. Nicol, is apparent from the fact that the double unconformability is admirably seen along the ridge between Coinne-mheall and Ben More, and further from the presence of the various intrusive dykes on their proper horizons. The area occupied by the Cambrian strata is about half a square mile, about half of which is buried under the basal quartzites. In the corrie on the north-east side of the mountain they reappear with the conglomerate at the base, resting on the old platform. The general inclination of the Cambrian strata is towards the W.N.W., at an average angle of 20°; the greatest thickness is about 1500 feet. In the Bealloch of Coinne-mheall (fig. 16), the hade of the Ben- More thrust-plane becomes almost flat, and hence the outcrop can be followed for two and a half miles down the river Oykel. Along the line of outcrop, the Cambrian sandstones reappear above the IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 423 thrust-plane, dipping underneath the Archean gneiss in inverted order (see section), as previously described by Mr. Callaway. There can be no doubt, however, that this strip of Cambrian strata, extending nearly two miles down the valley, is merely a continuation of the mass on Coinne-mheall, as shown in section. Fig. 17.—Horizontal Section from the Oykel Valley (About 2 miles in length.) Ben More. accross Ben More. THE PLAT REID Se FE Se: hus === a as Y ——— —S Uf f fe nd CAN) HUN ‘nig NM IHU ANALT NANA) i i Pu Na i Ih Ai i Ni pe SS NT ~ <2 ZSSS Su a i i i) bia RAN SAA erst AT NI eee ma Su NAAN } us oF - The slice of Archean rocks bearing these nee sn deo and Silurian strata, driven westwards by the Ben-More ‘Thrust, is of large dimensions. The Archean gneiss and basic dykes form a grand cliff about 1500 feet high overlooking Dubh Loch More, and they sweep across the lofty peaks separating the Oykel from the Gorm Lochs. Though still recognizable as a part of the old Archzean platform, the rocks have undergone important changes due to the movements, as will be shown further on. The outcrop of this great thrust-plane can be followed southwards from the Oykel valley, round the western slope of Sgonnan More, by Strathsheaskich, thence to Allt an Loin Dubh, curving round Cnoe na Glas Choille to the base of the Cromalt Hills, where it is overlapped by the Moine Thrust-plane. Of special interest, however, are the numerous outliers of the materials lying above this thrust-plane, left by denudation in the most extraordinary situations. The most important oceur on Cnoc an Leathaid Bhuidhe west of Loch Awe, on the moor south of Loch Urigill, and on the limestone plateau south-east of Stronechrubie. The two isolated masses, resting on the limestones to the north and south of Allt nan Uamh, are of great importance, as they show the original folding of the Ben-More Thrust-plane over the quartzite range of Braebag, and the overlap of the Glencoul Thrust-plane by the former (see fig. 18). Descending the slopes of Canisp the double unconformability of the quartzites on the Cambrian sandstones and Archean rocks is well exposed, the lower zone being overlain by the “ pipe-rock ” in natural sequence. Crossing the Loanan, the “ pipe-rock ” is followed by the “ Fucoid-beds,” Serpulite-grit, and basal limestone, the latter three zones being repeated by reversed faults. Ascending the west declivity of Beinn’an Fhuarain, the two lowest groups of limestone are repeated by minor thrusts till we reach the outcrop of the Ben- More Thrust-plane. Just above the plane, on the north-west face c = ESh SCOWAN Male EBREBAG (About 8 miles in length.) ‘ig. 18.—Horizontal Section from Canisp east by the River Loanan, Ben Fhuarain, Braebag to Sgonnan More. CANISP WNM. . RECENT WORK OF THE GEOLOGICAL SURVEY SOR ot og tip E ys % 3 r ty 125 2 IN tm mse ‘ ; Mh i Cos if a of the hill, the “pipe-rock” appears with an inverted dip, plunging under- neath the basal quartzites, the beds being inclined to the E.S.E. at tolerably high angles. Near the hill-top the uncon- formable junction of the basal quartzites on the Cambrian sandstones is exposed, and when followed southwards the false- bedded quartzites pass transgressively across the. Cambrian strata and’ rest directly on the Archean gneiss. Only a small exposure of the gneiss is met with, but it presents the normal charac- teristics and contains one of the basic dykes. This remarkable outlier is about a mile in length, from north to south, the outcrop of the thrust-plane forming a striking feature round the hill. The limestones are exposed in the various swallow-holes adjoining the plane, and the actual] disruption-line is seen in dip-section on the north-west shoulder of the ridge. The Allt nan Uamh has carved a deep channel through the underlying limestones and has isolated the outlier on Beinn Fhuarain from that on Beinn nan Cnaimhseag on the north side of the stream. In the case of the latter, the Archean rocks are not ex- posed, but the basal quartzites rest un- conformably on the Cambrian sand- stones. By means of these and other outliers, originally continuous with the strata lying above the main outcrop on Sgonnan More, we can form a clear conception of the enormous extent of these terrestrial displacements and also of the vast amount of denudation which has since taken place. Only a brief reference can be made to the large number of thrust-planes repeating the Silurian strata, with occa- sional wedges of Archzean rocks, to the east of the Ben-More Thrust-plane. The alteration produced by these move- ments in advance of the Moine Thrust- plane is remarkable. So striking is the change, as will be shown presently, that Mr. Callaway grouped the Loch-Ailsh IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 425 limestones with the Caledonian series, thus regarding them as of Pre-Cambrian age. But in the course of the survey of that region we found that the false-bedded quartzites, the ‘“ pipe-rock,” the “ Fucoid-beds,” the Serpulite-grit (with the Serpulites) are associated with the crystalline limestones and the intrusive sheets, the whole series being intersected by numerous thrusts which develop new structures of an important kind. Advancing southwards to the confines of Assynt, we find evidence of an extraordinary overlap of the Moine Thrust-plane, along the base of the Cromalt Hills to the south of Elphin and Loch Urigill, From the base of the Stack of Glencoul the outcrop of this thrust-plane can be traced continuously, southwards by Loch Ailsh, thence crossing the Oykel and Allt Halag in a 8.S.W. direction. From the latter point i runs west for a distance of six miles, along the base of the north slope of the Cromalt Hills to the famous Knockan cliff south of Elphin, passing transgressively across the Ben-More Thrust-plane and all underlying thrusts, till the mica- ceous flagstones rest at various localities on the undisturbed Silurian strata. Between Loch More and Glencoul the belt of complicated ground extending from the outcrop of the Moine Thrust westward to the edge of the undisturbed Silurian strata varies from two to four miles ; while from Glencoul to the base of the Cromalt Hills, the belt averages about six miles in width. When we reach the Knockan cliff, the southern prolongation of this complicated ground is buried underneath the materials borne along the plane of the Moine Thrust. Indeed, had it not been for the extensive denudation of the strata above the latter thrust-plane, we should never have been able to study the sequence of these terrestrial movements, or the various stages in the production of the Moine schists. With the view of showing the belt of complicated ground, com- prising displaced Archean, Cambrian, and Silurian strata, along the northern margin of this great overlap, the accompanying horizontal section (fig. 19) has been drawn from Elphin eastwards by Am Pollan and Cnoc na Glas Choille, to the outcrop of the Moine Thrust-plane in Allt Ealag. At Elphin, close to the road leading to Ullapool, the “ Fucoid- beds ” and Serpulite-grit are truncated by a powerful major thrust, bringing forward the piled-up ‘“ Fucoid-beds,” Serpulite-grit, and basal limestone. The latter are abruptly cut off by another major thrust-plane, along which the Hilean Dubh limestones have been driven, repeated by innumerable minor thrusts, for a distance of two miles. At Am Pollan, these displaced limestones are capped by an outlier of the materials lying above the Ben-More Thrust-plane, consisting of Archzean rocks covered unconformably by the Cam- brian sandstones and the basal quartzites, the latter resting uncon- formably on both. Advancing eastwards, the strata are mainly composed of piled-up limestones, which, at the base of the west slope of Cnoc na Glas Choille, are overlapped by the Silurian strata lying above the main outcrop of the Ben-More Thrust-plane. In the 426 (About 6 miles in length.) Fig. 19.—Horizontal Section from Elphin to Allt Halag. NW CROMALT POLLAN ELPHIN ALLT EALAG RECENT WORK OF THE GEOLOGICAL SURVEY heart of the latter displaced materials a small patch of Archzan rocks has been exposed by the denudation of the basal quartzites. In ad- dition to the latter, all the Silurian zones, up to the horizon of the Eilean Dubh limestones, have been borne westwards along this disruption- plane, comparatively unaltered in places, till we approach the micaceous flagstones above the Moine Thrust-plane, where the quartzites have been converted into quartz-schists, and the dykes have also been rendered schistose. Advancing southwards to the Knockan cliff, about two miles to the south of the foregoing line of section, there is a remarkable difference in the order of succession of the strata. On the eastern slope of Coul More the basal quartzites rest uncenformably on the Cambrian sandstones, followed in natural order by the ‘‘ pipe-rock,” ‘* Fucoid-beds,” and Serpulite-grit, the latter being exposed on the Knockan cliff east of Lochan Fasaig. Overlying the Serpulite- grit in natural sequence, there is a small portion of the basal limestone of the Ghrudaidh group, which is abruptly truncated by a major thrust- plane, bringing forward the white limestones and marble of the Eilean Dubh group. The latter are succeeded by the finely laminated micaceous flagstones above the Moine Thrust-plane. Following the outcrop of this thrust-plane southwards to Strath Kanaird, a distance of nearly six miles, the Moine micaceous flagstones rest, now on the basal limestones, now on the Serpulite-grit, and again on the “ Fucoid-beds,” passing transgressively from one horizon to the other, thus showing the complete discordance between the materials above and below the thrust-plane (fig. 20). As the flagstones lie on the undisturbed beds, there seems at first sight to be a natural passage from the Silurian strata into the eastern schists; but the apparent conformity is entirely deceptive. That such is the true explanation of the rela- tions of the strata along this line of section is still further confirmed by the remarkable evi- dence in Strath Kanaird, near Langwell. About a mile to the east of the normal outcrop of the Moine Thrust, the river has cut down through the thin cake of micaceous flagstones, and eaposed on the south side of the valley a large mass of Archean gneiss, covered unconformably by the IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. basal quartzites (fig. 21). There can be little doubt, from the evidence obtained at Am Pollan (Loch Uri- gill), in the valley of the Achall, and at Ullapool, that this mass of Archean rocks and basal quartzite has been borne along by the Ben More Thrust, and that the materials rest on the piled-up Silurian strata underneath. Passing southwards to the Achall valley, there is a regular ascending series from the basal quart- zites, resting unconform- ably on the Cambrian sandstones, up to the Ser- pulite-grit and a portion of the basal limestone. The latter zones are abruptly truncated by a powerful major thrust driving forward nearly all the zones of the Ghrudaidh and Eilean Dubh lme- stone-groups, repeated by numerous reversed faults. The limestones are over- lapped in turn by the materials lying above the Ben-More Thrust-plane, consisting of a great deve- lopment of Archean gneiss with the basic dykes covered unconformably by the Cambrian conglome- rate and sandstones, with the basal quartzites resting unconformably on _ the latter. The serpentine re- ferred to by Prof. Nicol as occurring in the Achall valley is one of the ultra- basic dykes in the thrust Archeean gneiss. The Ben- More Thrust-plane in the Achall valley is inclined to nh | FS co sie Rh. AARC NE UN NE ‘ a ee ee ne om enn senien eras os of ’ ‘ OUWNIN YS ‘souojyshoy y aucopy ayp fo pspru ayn ur uounpnuap fig 1PS0Q PUD SsuD UnaYoy 242 Ym yambunT yn panuny ywurg buojn uoyoay powWozr.L0fJ—"1Z “Si (yysu9] ur satu g ynoqy) pasodxa sazj,unne ZIVNOYD ‘SIUT 2ynuorg ayn 07 Ig unyoouy ayn woif woroog ynauozuojyJ— 0g “Sty S77T/IH (‘Y4SU9] UT soTtuE g ynoqy) 498 RECENT WORK OF THE GEOLOGICAL SURVEY ~ the east at an angle of 35°; but in placesit has been folded, and the materials lying above it have been denuded away. Hence we find, to the west of Glastullich, that it is overlapped by the Moine flagstones, which there rest directly on the thrust Silurian lime- stones. From the Achall valley southwards to Ullapool the outcrop of the Ben-More Thrust-plane can be traced almost continuously by means of the Archean rocks. In two places, however, it is over- _ lapped by the Moine Thrust, which ushers in the micaceous flagstones. To the east of Ullapool there is an undisturbed order of succession from the basal quartzites to the Serpulite-grit. Along this latter horizon there is a powerful major thrust, bringing in a portion of the Cambrian sandstones overlain unconformably by the basal quartzites and succeeded by the various members of the Silurian series up to the limestone. Following the line of outcrop of this major thrust, southwards by the Braes of Ullapool to the shore of Loch Broom, a large mass of Cambrian sandstone appears above the plane, resting on the Serpulite-grit and spreading over a considerable area to the north of Corry Point. Near the latter locality the basal quartzites, in several places, rest unconformably on the Cam- brian sandstones (fig. 22). Fig. 22.— Horizontal Section south of Ullapool. (About 1 mile in length.) Passing eastwards, the Cambrian and Silurian strata borne along by this major thrust are abruptly truncated by the Ben-More Thrust-plane, well exposed at various localities. Along the western face of the disrupted gneiss, small patches of Cambrian strata rest unconformably on the latter with an inverted dip towards the plane of disruption. Eventually within a short distance the Archean gneiss is overlapped by the micaceous flagstones above the Moine Thrust-plane. To the south of Loch Broom the major thrust, which forms such an important feature in the geological structure of the Ullapool and Achall districts, is entirely overlapped by the Ben-More Thrust- plane, bringing forward a large slice of the old Archean platform, consisting of gneiss with numerous basic dykes, covered unconform- ably by patches of Cambrian conglomerate and _ sandstone. Advancing southwards towards Little Loch Broom, the materials lying above the Ben More Thrust-plane consist almost wholly of Cambrian strata, which, at Dundonald, have been converted into schists. Indeed, so striking is the metamorphism developed by IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 429 these movements in the Cambrian strata near- Dundonald that it is difficult to trace the line between the schistose sandstones and the eastern schists. VI. MeraMORPHISM RESULTING FROM THE Post-LowER- SiLtuRIAN Movemen's. Having described the evidence in proof of enormous terrestrial movements along the chain of mountains between Eriboll and Ullapool, we now proceed to consider the relation of these dis- placements to regional metamorphism *, In reviewing the effects of these movements, we will describe the evidence furnished by (1) the Archean, (2) the Cambrian, (3) the Silurian, and (4) the igneous rocks intrusive in the Cambrian and Silurian strata. From these various lines of evidence it will be seen that with each successive maximum thrust there is a progressive alteration in the displaced materials as we pass eastwards to the horizon of the micaceous flagstones overlying the Moine Thrust-plane. 1. Metamorphism of Archean Rocks. The great slice of Archzean rocks brought forward by the Glencoul Thrust does not present any striking evidence of deformation except close to the lines of disruption. To the north of Glencoul the original banding of the gneiss is as distinct as that in the Archean area to the west of the Post-Lower-Silurian displacements, the general strike being W.N.W.., and the dip of the foliation being 8. W., at high angles. It is a significant fact that although the north-west dolerite-dykes are numerous in the undisturbed Archean area between Ben Stack and Glencoul, none is met with in the thrust- eneiss, above this thrust-plane, till we pass southwards to Glencoul. Indeed the absence of these basic dykes and the presence of broad veins of red pegmatite point to the conclusion that the displaced gneiss between Strathcarran and Glencoul resembles that in the Archean area to the north of Ben Stack. By protracting the angle which the basic dykes in the undisturbed gneiss on Ben Stack make with the direction of movement in the displaced masses, it is clear that the disrupted rocks must have travelled for several miles from the east. Overlying the thrust-plane, a thin band of slaty schist or highly sheared gneiss is frequently met with, the strike of the foliation being more or less parallel with that of the thrust-plane. Ad- vancing eastwards towards the limit of the displaced mass, these new divisional planes are more strikingly developed, owing to the number of more or less powerful thrusts. In the latter case, the new planes of schistosity may be either parallel with those of the * It ought to be borne in mind that, though the movements affecting the Cambrian sandstones and the fossiliferous quartzites and limestones are now regarded as of Post-Lower-Silurian date, it may ultimately be possible to fix their age with greater precision, when the fossils from the Durness Limestone have been correlated with those of other countries. 430 . RECENT WORK OF THE GEOLOGICAL SURVEY thrust-planes or inclined at a higher angle. The basic dykes on the northern slope of Glasven show no perceptible alteration except where they have been traversed by some of the powerful Post-Lower- Silurian disruption-lines; but they show in a marked degree the foliation produced by the Pre-Cambrian movements. The alteration of the Archean rocks is more pronounced above the horizon of the Ben-More Thrust in Assynt. Along the uncon- formable junction of the gneiss with the Cambrian and Silurian strata, the former has entirely lost its original structure, and has been converted into greenish epidotic schist, the dip of the foliation being E.S.E. In one remarkable case, to be immediately described, where the gneiss is overlain by the Cambrian conglomerate, the schistosity developed in the latter passes downwards into the former, irrespective of the original bedding of the Cambrian beds or the original foliation of the gneiss. The new structures in the gneiss, along the junction-line, have been produced by the more rapid movemeut of the upper layers of displaced materials, without destroying the geological relation between the two. In other words, there has been a differential movement of the several layers of the thrust-masses as well as of the constituent particles over each other. Along the eastern slope of the Ben-More range, northwards to Glendhu, where powerful thrusts follow each other in rapid succession, bearing forward slices of the old Archean platform with the quart- zites, the new divisional planes are very prominent. Further, in the case of the dolerite dykes, new foliation-planes have been pro- duced along the disruption lines, which are much more conspicuous than in the displaced dykes above the Glencoul Thrust-plane. Advancing eastwards to the belt of sheared gneiss and green schist underlying the Moine Thrust-plane the evidence relating to regional metamorphism is of a most remarkable kind. The gneiss occupying this horizon between Loch More and Strathcarran possesses new divisional planes, the old ones having been almost wholly effaced. The dip of the foliation is E.S.E., being more or less parallel with that of the thrust-plane. On the foliation- surfaces close parallel lines, like those of slickensides, are met with, indicating the direction of movement, varying from 20° to 40° S. of E. The divisional planes are also coated with a thin film of sericite-mica, while “eyes” of felspar are drawn out in the direction of the movement. The pegmatites, too, have been sheared, so that their foliation-planes coincide with those of the gneiss, the original quartz and felspar appearing now as thin, close, red and white parallel streaks in the direction of the movement lines. Notwith- standing this extreme alteration of the Archean rocks south of Loch More, the patch of limestone occurring in the heart of the mass is still recognizable as belonging to the two lowest limestone groups of Durness. Along this same belt of sheared gneiss and green schist between Assynt and Loch Eriboll the Archean gneiss has been rolled out into a finely laminated slate or slaty schist (mylonite), breaking into thin folia like leaves of paper. All the various stages of deformation, IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 431 from the crushed Archean gneiss on the one hand, to the lami- nated slate on the other, can be clearly traced. The original constituents of the gneiss have been comminuted, but here and there broken fragments of the felspars occur, which are invariably drawn out in the direction of movement. The colour of the slaty schists has been determined by the nature of the materials out of which they have been made. Where the Archean gneiss contained much epidote, the slates or “‘ crush-rocks ” are light green ; where it contained much hornblende, they are dark green ; where pegmatites or granitoid gneiss have been the chief materials employed, the resultant slates are red or pink. These finely laminated schists or slates show beautiful examples of fluxion-structure; and their foliation-surfaces display closely set lines or ‘ striping,” indicating the direction of movement of the particles over each other, the general trend of the latter being E.S.E. Associated with these slates are certain belts of “ frilled” dark-green schists, of precisely the same character as those so well exposed on the coast-section east of Whitten Head, Loch Eriboll. A detailed study of the remarkable structure presented by these “frilled” schists points to the conclusion that they have been formed by Post-Lower- Silurian movements mainly out of dark hornblendic gneiss, the folia having been piled on each other by minute major and minor thrusts. Occasionally, along this belt of sheared gneiss and schist, there are lenticular masses of the original Archean rocks, which only show partial deformation, and, in addition to these, strips and wedges of Silurian and Cambrian strata which have been completely con- verted into schists. 2. Metamorphism of Cambrian Strata. It is interesting to note that no Cambrian strata occur among the displaced masses brought forward by the Glencoul Thrust in Sutherlandshire. They do not appear till we reach the horizon of the materials lying above the Ben-More Thrust-plane. The various changes produced by these movements in the Cambrian conglo- merates, sandstones, and shales are strikingly exemplified on Ben More, on the north side of the Oykel valley, and on Sgonnan More. Beginning with the basal conglomerate, or ‘‘ Button-stone,” we find that it has undergone extraordinary changes, both where it underlies the gneiss in the Oykel valley and where it overlies that rock in Corrie Mhadaidh. In its unaltered form, throughout the undisturbed Cambrian areas, this characteristic band of conglo- merate is composed of more or less well-rounded pebbles of quartz- rock, gneiss, pegmatite, diorite, &c., imbedded in a loose, gritty matrix. But where it has been subjected to mechanical movement, the softer pebbles of gneiss and the fragments of the basic Archean dykes have been crushed, flattened, and elongated in the direction of movement. Indeed, in some cases, they have been drawn out to such an extent as to form thin lenticular bands of micaceous or Q.J.G.8. No. 175. 24 3 er me oS —_ 432 RECENT WORK OF THE GEOLOGICAL SURVEY hornblende-schist flowing round the harder pebbles of quartz-rock. The latter still preserve their rounded form, but they are traversed by small “ step” faults, tending to elongate them in the direction of movement. The original gritty matrix has been converted into a fine micaceous or green chloritic schist, showing exquisite ‘ flow- structure,” winding round the elongated pebbles in wavy lines. In short the matrix has been converted into a fine crystalline schist, and but for the presence of the deformed schistose pebbles it would probably be impossible to tell that the schist had a clastic origin. No less remarkable is the phenomenon displayed in Corrie Mha- daidh (see fig. 23), where the foliation passes downwards from the Cambrian conglomerate into the underlying gneiss, irrespective of the bedding-planes of the former and the original foliation of the latter. The conglomerate is inclined to the W.N.W. at an angle of 20°. Along the line of junction it is welded to the old Archean platform, so that rocks of widely different geological age practi- cally form onemass. The planes of schistosity in the conglomerate dip to the E.S.E., more or less parallel with the plane of the Ben- More Thrust, and they are continued downwards into the gneiss, the © original structures of which have been entirely effaced. The Cambrian grits, sandstones, and shales have also been pro- foundly affected by these movements. Throughout them all cleavage- planes have been developed, dipping towards the E.S.E., more or less parallel with the plane of the Ben-More Thrust, at an average angle of 45°; while the original lines of bedding dip towards the W.N.W. Owing to the variable nature of the Cambrian strata, however, the cleavage is very unequally distributed, the teds of coarse grit being less distinctly cleaved, and the planes being more highly inclined than those in the finer sandstones and shaly bands. In fact, there seems to be a constant relation between the inclination of the cleavage-planes and the texture of the strata. The fine flags and shales behave, so to speak, like lines of weakness, their consti- tuent particles having been drawn out or dragged much further than those of the grits. The planes of schistosity in the grits, flags, and shales form a series of sigmoidal curves, as represented in the accompanying section (fig. 23). In addition to the cleavage, new minerals have been developed in the Cambrian strata. Sericite is abundant in the finer bands, so much so, indeed, that they might fitly be termed sericite-schists. At regular intervals too, along finer bands between the grits, lenticular veins of pegmatite occur, more or less parallel with the new schis- tose planes. Again, on the slopes of Sgonnan More, the Cambrian flags and shales have been rendered schistose and show minute spots or knots resembling those in the knotted schists. This phenomenon is observable above the outcrop of the Ben-More Thrust-plane. Finally, in the neighbourhood of Little Loch Broom, along the margin of the eastern schists, the Cambrian sandstones have been converted into schists, in which mica has been developed, and wherein the folia show beautiful wavy lines analogous to those in IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 433 the belt of green schist already described. At this locality these Cambrian schists seem to merge into the eastern schists without any well-marked boundary line. Fig. 23.—Diagram of Cambrian Strata on Coinne-mheall, dlus- trating differential cleavage, schistosity, and formation of peg- matite in Cambrian Grits and Shales above Ben-More Thrust- plane as seen in Coinne-mheaell and River Oykel. (Area shown about 12 yards square.) . Coarse Grits or Arkose. . Finer Grits or Arkose. . Shales. . Pegmatites. The arrow shows the direction of movement. a9 &8 3. Metamorphism of the Silurian Strata. The various meinbers of the Silurian series underlying the Glencoul Thrust-plane show little alteration, even where they have been piled on each other by minor and major thrusts. The ‘“‘ Fucoid-beds” are oc- casionally cleaved, the planes being determined by the adjacent thrusts. Not till we pass eastwards to the horizon of the materials above the Ben-More Thrust-plane is much change observable: The various powerful thrusts above this horizon, repeating wedges of the Archxan platform with various members of the Silurian series, produce marked changes in the latter. Both zones of the quartzite have been attenuated by the elongation or dragging-out of their constituent mineral particles. In the case of the false-bedded grits, the small pebbles of quartz and felspar have been drawn out to a length of three inches near Loch Strath nan Asinteach. The felspar pebbles are ofteu cracked in the direction of the movement and the fissures are filled with secondary quartz. Again, in the “ pipe-rock,” the quartz-grains have been elongated and the vertical “pipes” or Annelide-tubes have been bent over, flattened, and drawn out into ribands parallel with the direction of movement. Along the 2a2 434 RECENT WORK OF THE GEOLOGICAL SURVEY divisional planes sericite has been abundantly developed, so that the strata lose all their normal characters and merge into quartz- schists. As a result of these changes, the quartzites have been reduced to a third of their usual thickness. At the base of the Stack of Glencoul and near Loch Ailsh, underneath the outcrop of the Moine Thrust-plane, these new structures are strikingly dis- played. At the latter locality other members of the Silurian series share in the metamorphism. Advancing outwards from the Loch- Ailsh road to Cnoc Chaoruinn, the Silurian zones, from the false- bedded quartzites to the basal limestones, are repeated by thrusts at - Intervals of a few yards. At first the various zones are quite recognizable, the pipes in the quartzite being slightly bent over and the Serpulite-grit yielding Serpulites after a careful search; but with each successive displacement their characters are gradually modified, till it is impossible to distinguish them from some of the members of the eastern schists. The false-bedded quartzites merge into quartzose sericite-schists; the “ pipe-rock” passes into a fine quartz-schist, in which the pipes are flattened like stfips of paper, parallel with the foliation-surfaces; the original lines of bedding of the “ Fucoid-beds ” wholly disappear and are replaced by divisional planes, coated with white mica; the Serpulite-grit, no longer yielding Serpulites, becomes a quartz-schist, and, finally, the lime- stone becomes crystalline. On the new divisional planes numerous fine parallel lines are met with, indicating the direction of move- ment, trending generally E.S.E.; indeed this “ striping” is equally apparent in the quartzites at the base of the Stack of Glencoul, at the head of Glendubh, and other localities. 4, Metamorphism of the Igneous Rocks intrusive in the Cambrian and Silurian Strata. The evidence relating to regional metamorphism furnished by the great series of intrusive sheets in Assynt likewise indicates progressive alteration as we pass eastward to the Moine Thrust- plane. In the undisturbed area to the west of the Post-Lower- Silurian movements the igneous rocks of a granitoid type never show the slightest trace of a foliated or banded arrangement. The felsites, on the other hand, frequently show fluxion and sphe- rulitic structures, where they traverse the old Archean platform, along the margins of the dykes. Passing eastwards to the displaced Silurian zones underlying the Glencoul Thrust-plane, hardly any change is observable in the sheets, except in those instances where they have been driven along the “ sole” of a major thrust. In the latter case the diorites in the limestones have been slightly cleaved and rendered schistose. @rossing the outcrop of the Glencoul Thrust to the slopes of Coinne-mheall, we observe that some of the porphyritic felsites show a flow-structure like that of the rhyolites, and that in one case the rock has been completely reconstructed so as to become a fine- grained schist. On the crest of Coinne-mheall, just above the Ben- IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 435 More Thrust-plane, the sheets of felsite injected along the bedding- planes of the basal quartzites have been converted into soft sericite- schists, which can be cut with a penknife; and in Corrie Mhadaidh a felsite dyke on the same horizon has been cleaved parallel with the planes of schistosity in the Cambrian strata and with the plane of the Ben-More Thrust. All these changes have been developed in the dykes without much alteration in the quartzites in which they occur. Again, on the north side of the Oykel valley, a dyke of porphyritic felsite in the inverted Cambrian strata, above the Ben- More Thrust-plane, has been converted into a mica-schist, showing that peculiar ‘“frilled” structure so marked in the green “ frilled schists ” of Eriboll. Still further eastwards, in the belt of thrust and sheared Silurian strata stretching southwards from the Stack of Glencoul by the Gorm Lochs to Loch Ailsh and Allt Ealag, nearly all the dykes and sheets are beautifully foliated, the planes of schistosity being parallel with the planes of thrust. The fine-grained diorites in the lime- stones are now represented by green hornblende-schists and chlorite- schists ; the holocrystalline rocks with porphyritic felspars set in a micro-crystalline base appear as bands of ‘‘augen-gneiss ” and “ au- gen-schist ” ; and finally, along a line of powerful thrust in the great granitoid sheet east of Loch Borrolan there is a belt of ‘‘ augen-gneiss” with pyroxenes, which, existing originally as porphyritic crystals, now appear as “‘ eyes” in the foliated rock. Indeed, so striking are the changes in these intrusive sheets close to the Moine Thrust- plane, that it would be almost impossible to identify them, were it not for the still recognizable zones in which they occur. Where the latter lose their distinctive characters, bands of white quartz- schist are then found, alternating with grey or green hornblende- schist. | | From these various lines of evidence it is quite apparent that there is progressive metamorphism on a grand scale as the observer passes eastwards from the undisturbed western belt of ground to the horizon of the Moine Thrust-plane. It is also obvious that the crystalline rocks, where they occur in thin sheets, become schistose much more readily than the clastic rocks, and that the Cambrian sandstones and shales are more easily cleaved than the Silurian quartzites. It is also probable that the great thickness of the slice of Archean rocks above the Glencoul thrust-plane, together with the heterogeneous character of its materials, prevented the develop- ment of new divisional planes in the thrust-gneiss, the deformation showing itself mainly in the fracture and crushing of the crystals. Not till we reach the point where powerful thrusts follow each other in rapid succession, repeating thinner slices of the old Archean platform in the overlying quartzites, is the Post-Lower-Silurian shearing strongly marked in the Archzan rocks. At length in the zone of green schist and sheared gneiss underlying the Moine Thrust each divisional plane or foliation-surface is a shear-plane developed by these Post-Lower-Silurian movements. 436 RECENT WORK OF THE GEOLOGICAL SURVEY 5. Succession of Strata above the Moine Thrust-plane. We must now describe briefly the strata overlying the Moine Thrust- plane, stretching eastwards by the Kyle of Tongue to Strathnaver. For nearly six miles there is a belt of strata of remarkably uniform character, consisting of flaggy quartzose mica-schists or fine-grained gneiss, typically developed on the Moine between Loch Eriboll and the Kyle of Tongue. These strata (the “younger gneiss”. and ‘‘ quartzose flagstones ” of Murchison) have been traced continuously from the north coast of Sutherland to Loch Broom, showing little variation in lithological character. Inthe heart of the mass there is a prominent zone of hornblendic and micaceous schist, studded with garnets, traceable from the north coast to the Kyle of Tongue and thence round the north and west slopes of Ben Hope. There can be little doubt that this zone has once been an extensive sheet of igneous rock, because at various localities patches of the original igneous mass are still met with, consisting of diorite or diabase. Overlying this belt of garnetiferous schist, bands which can still be recognized as sheared Archean gneiss can be followed for some distance. Like the crushed slates, schists, and sheared gneiss (mylonites) un- derlying the Moine Thrust-plane, these flaggy crystalline schists and eneisses are inclined at gentle angles to the E.S.E. That they form an enormous pile of material is evident from the fact that they rise from the sea-level to the crest of Ben Hope (3040 feet). Buta careful examination of the path along which they have travelled shows that the divisional planes or foliation-surfaces lie at an oblique angle to the thrust-plane (see fig. 20, where the Moine schists are represented as lying at an oblique angle to the plane of the Moine Thrust). It is obvious, therefore, that the thickness of the Moine schists cannot be estimated after the manner of ordinary sedimen- tary strata. This conclusion is confirmed by a study of the struc- tures presented by these schists) The main divisional planes truncate minor planes, like the major and minor thrusts in the dis- placed Silurian strata. In other words, as the schists were being driven forward the materials were piled on each other to an enor- mous thickness. Further, on closer examination, it is observable that the different mineral constituents lie at an angle to the main foliation-planes. There is also evidence to show that the terrestrial movements were intermittent, because the first divisional planes in the Moine schists are frequently truncated by subsequent thrusts. During pauses in the disturbances dykes and thin sheets of various — igneous (granitoid) rocks were injected across the foliation-planes, and these intrusions have been in turn sheared by later movements. These crystalline schists and flaggy gneisses display parallel lines on the foliation-surfaces, indicating the same direction of moyement as those in the sheared Silurian strata and crushed slates and schists (mylonites), while the constituent minerals are orientated along these lines. It is obvious, therefore, that the present strike, dip, and lithological characters of these crystalline schists and flaggy gneisses IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 437 were developed by movements after the Lower Silurian period. They differ, however, from the mylonites underlying the Moine Thrust-plane in one important feature, viz., that their matrix is holocrystalline. In other words, the formation of the Moine schists, as Professor Lapworth has shown, has been attended by greater molecular changes. Throughout the crystalline matrix numerous “eyes” of felspars and quartz occur, belonging to the original rock out of which the schists have been formed. ‘The holocrystalline character of the Moine schists points in all proba- bility to the conclusion that in their case the movements took place at a more rapid rate, thus producing a higher temperature and giving rise to greater chemical changes after the movements had ceased. To the east of the Kyle of Tongue, the Moine flaggy schists alternate with occasional bands of hornblende-schist as far as Strathan, where they are succeeded by a belt of undoubted Archean rocks, two miles in width, stretching eastwards nearly to the river Borgie. Consisting mainly of hornblendic gneiss with masses of rudely foliated diorite and dykes of ultra-basic materials (perido- tites, &c.), these rocks present many of the typical features of the Archeean gneiss west of Durness. When followed southwards, this belt thins away till it disappears to the north of Loch Creagach, near Ben Loyal. To the south of Tongue another belt of Archean rocks has under- gone a great amount of deformation by the Post-Lower-Silurian movements, the foliation-planes coinciding in direction with those of the Moine schists. But here and there throughout the belt patches of gneiss and pegmatite, showing the Pre-Cambrian foliation, may be detected. Advancing eastwards to the Borgie River, we find alternations of flagey Moine schist and gneiss, Archean hornblendic gneiss striking generally north and south and dipping to the east, overlain by a peculiar type of gneiss in Strathnaver. Consisting mainly of black micaceous gneiss in which the mica is very abundant, this zone contains ‘‘eyes,” “cores,” or oval-shaped masses of diorite, whereof the longer axes lie parallel with the strike of the foliation. Round these “cores,” both mica and hornblende curve in wavy lines, the latter disappearing as they are followed outwards into the well-foliated gneiss. There can be little doubt that these lenti- cular masses, or “ cores,” are patches of a once continuous sheet of igneous rock, out of which the Strathnaver gneiss has been formed. A remarkable characteristic of this foliated mass is the development in it of pegmatites, mainly along the lines of foliation. Beginning as isolated knots of felspar, they gradually become continuous, giving rise to thin strings or veins and eventually increasing in size till they form bands a hundred yards across. The formation of these pegmatites evidently formed a part of the process of metamor- phism whereby the eruptive igneous mass was converted into a micaceous gneiss. From the fact that bands of Moine schist or flagey micaceous gneiss are intercalated with the Naver gneiss, it is 438 RECENT WORK OF THE GEOLOGICAL SURVEY highly probable that the deformation of this Archean mass was mainly effected by the Post-Lower-Silurian movements. From Bettyhill to Kirktomy there stretches a belt of flaggy micaceous gneiss, resembling part of the Moine gneiss; but to the east of the latter locality lies an area of undoubtedly Archean rocks, several miles broad, which have only been slightly affected by the Post-Lower-Silurian movements. ‘They consist of coarse hornblendic and micaceous gneiss with bands of diorite and gabbro, similar to the Pre-Cambrian crystalline rocks at Cape Wrath. Though the area to the east of Strathnaver has not been mapped in detail, we are at present inclined to believe that this broad belt of Archean rocks resembles the mass of Pre-Cambrian strata at Strathan Skerray in its mode of occurrence. ‘The latter, as we have shown, is intercalated in micaceous Moine schist or flaggy gneiss. The Archean rocks east of the Naver are traversed by dykes of pink and grey granite, which have been converted into granitoid gneiss by mechanical movements. After the Moine schists and gneiss to the south of Tongue had acquired their present strike, dip, and lithological characters, in con- sequence of the terrestrial movements after the Lower Silurian period, the great sheet of syenite now constituting Ben Loyal was erupted, mainly along the foliation-planes. On the western slope of the mountain the schists and gneiss plunge underneath the intrusive mass with an E.§.E. dip, while along the north and south margins of the area they also pass underneath it. To the east of Ben Loyal the main body of syenite divides into several branching sheets, which are likewise intruded more or less along the foliation-planes. The boundary line traverses the western slope of Ben Loyal at a height of about 1000 feet, while the peak rises to a height of 2504 feet, so that this great intrusive mass is upwards of 1500 feet thick. Other intrusive igneous rocks pierce the micaceous flagstones of the Moine series, consisting of dykes of diabase and mica-trap. The latter have been followed for miles through the Cromalt Hills, and in one case a dyke traverses both the Moine schists and the under- lying Silurian strata of the Knockan cliff. It is obvious that the facts now brought forward furnish a large amount of evidence in support of the theory that regional metamor- phism is due to the dynamical and chemical effects of mechanical movement acting alike on crystalline and clastic rocks. It is further obvious that regional metamorphism need not be confined to any particular geological period, because in the North-west Highlands it occurred on a yast scale both in Pre-Cambrian time and at some period subsequent to that in which the Durness limestones were deposited. 6. Denudation of the Land-surface before the time of the Oid Red Sandstone. In the neighbourhood of Tongue remarkable evidence is ob- tained regarding the denudation of the old land-surface before IN THE NORTH-WEST HIGHLANDS OF SCOTLAND. 439 the deposition of the Old Red Sandstone. Between Ben Loyal and the Kyle of Tongue various outliers of this formation, de- scribed by the present Director-General of the Geological Survey, rest on a highly eroded platform of the crystalline schists. The deposits are also met with in the islands at the mouth of the Kyle. One of these outliers, at Cnoc Craggy (1043 feet), about a mile and a quarter to the north of the northern margin of the Ben-Loyal syenite, was grouped by Professor Nicol with the Torridon sand- stones, and was believed by him to be overlain by quartzite*. The platform on which it rests is about 800 feet high. Upwards of 40 per cent. of the pebbles in the conglomerate are composed of the syenite of Ben Loyal. It follows, therefore, that the latter intru- sive sheet was stripped of the overlying schists, thus proving enor- mous denudation before the deposition of the Old Red Sandstone. Some of these outliers, on the east side of the Kyle of Tongue, rest on the Moine flagstones produced by the Post-Lower-Silurian movements, and they contain numerous fragments of these schists. Hence it is obvious that the changes must have been completed before the time of the Lower Old Red Sandstone. Further evidence that the outliers really belong to the Old Red Sandstone is furnished by their numerous pebbles derived from the Cambrian and Silurian formations. Amongst these, we noted Cam- brian sandstones, false-bedded quartzite, “ pipe-rock,” Serpulite-grit, and limestone belonging to several groups of the Durness limestone, some of the blocks containing Murchisonia. From the inclination of the layers in the conglomerate it is evident that the pebbles were borne by currents from the W.N.W. The detailed examination of the north-west of Sutherland has furnished important evidence regarding the glaciation of the region, showing, for example, that during the greatest extension of the ice the centre of dispersion did not coincide with the existing range of high ground. It has also thrown light on the excavation of the present valley-system, on the relation of disruption-lines and the trend of basic dykes to surface-features, and, finally, on the formation of lofty mountains by denudation. But the description of these and other phenomena is reserved for the detailed official memoirs of the Geological Survey. Discussion, The Prusipent observed that the communication just made to the Society was remarkable, not only for its importance, but for the mass of details it contained ; it was, in fact, four or five papers rolled into one. Professor LapwortH commented on the wonderfully descriptive character of the paper. The general conclusions arrived at were very similar to those he had himself indicated. There was this difference that when he brought forward his views such notions were novelties and were consequently regarded with suspicion. But so much has the question been ventilated within the last four years that he pre- * Quart. Journ. Geol. Soc. vol. xvii. p. 92. 440 RECENT WORK OF THE GEOLOGICAL SURVEY dicted for this paper a hearty reception. So well had the subject been worked out by Messrs. Peach and Horne and their col- leagues, that it had been made clear that our own country con- tained structures which were practically unequalled as types of metamorphism. So far from lagging behind, we were now fully abreast of foreign investigation; and when the paper came to be printed, with no stint as to illustrations, it must rank as one of the highest value. Such sections are to a certain extent astounding, yet they do occur. He spoke of the fascination of these studies, and felt sure that they gave promise of a great future for British geology. He was only acquainted with the Durness-Eriboll district ; but from his knowledge of the accuracy of the Authors’ work there, he had every confidence in their interpretation of the other districts. The paper will also add to our knowledge as regards the theory of the origin of the Archzan rocks. He complimented the officers of the Survey on the interest and excellence of their work. Dr. Hicxs considered that the interest attaching to the district under discussion will hold as far as Loch Carron. One point in respect of the origin of the Archzean rocks he particularly noticed in the paper was the amount of alteration these rocks had undergone in Pre-Cambrian times. These features were seldom obliterated by the new movements. It would be interesting to know to what extent the central area of the Highlands was made up of the old and the new rocks. He imagined that comparatively little of the latter would be found there. He spoke of the evidence afforded in the paper of rocks other than those now known to occur in the area, testifying to an enormous amount of denudation prior to the deposition of the Torridon Sandstone. He had also noticed and referred to the presence of such rocks in the Torridon series further south. He thought the paper a credit to the Survey and to British geologists generally. Professor Jupp also congratulated the Survey on this important piece of work. Before offering any criticisms we must wait till we have an opportunity of studying it in detail. It supplied important evidence in support of a principle which had been maintained by many of the most distinguished members of the Geological Society in past times—namely, that foliation is not coincident with strati- fication. Mr. Treat commented on the many points opened up, and on the immense amount of work embodied in the paper. He could say but little. What was the Archean gneiss originally ? what is its most original rock? In many instances the divisional planes are not vertical, but described as rolling at gentle angles. In such cases the strike is represented as being about N.E.; hence the so-called normal, or N.W. strike must be secondary. What do the original planes of division represent? Are they lines of segregation in a plutonic magma? He was glad to find that his petrographical work, more especially in connexion with the development of hornblende-schist out of dolerite, had been confirmed. Mr. Hupzzston said that every one who had paid any attention , : ‘ IN THE NORTH-WEST HIGHLANDS OF SCOTLAND, 441 to the difficult subject with which this paper deals must have listened with genuine pleasure to the story of the solving of these mysteries, which even a few years ago seemed almost to defy the attempts of geologists. Persons who lived before the discovery of “ thrust-planes ” might well be excused for not having read aright the section at Craig-a-Knockan. It was to be hoped that in the great future which was promised to British geology some attempt would be made to explain the dynamics of these phenomena. He ventured to point out what seemed to him a discordance between certain sections through the Ben More range and the generalized section through Assynt. Mr. Prac explained that the apparent discrepancies alluded to by Mr. Hudleston were due to a difference in the direction of the sections and in the level of the datum-line. He thanked the Society for the way in which the paper had been received, and in reply to Mr. Teall assured him that they had thought about these things, but their solution, he considered, must be left mainly to the microscopist. Mr. Horne alluded to the value of Professor Lapworth’s work, of which they had the highest appreciation, seeing that their conclusions were practically identical. Dr. Gurxte also expressed his satisfaction at the reception accorded to the paper. Referring to a remark by Dr. Hicks, the survey of the country had not yet got so far as Gairloch, where Dr. Hicks’s observations had been made. He was both ready and anxious to do justice to the work of previous writers. Referring to the future progress of the Survey, he held out hopes that another paper, giving the results of the detailed study of the southern half of the belt of great complication, might be presented to the Society ere long in anticipation of the Survey Memoirs. 442 MR, A. HARKER ON THE ERUPTIVE ROCKS IN THE 31. On the Enurrive Rocks in the Neighbourhood of Sarn, CAERNAR- VONSHIRE. By Atrrep Harker, Hsq., M.A., F.G.S., Fellow of St. John’s College, Cambridge. (Read May 9, 1888.) I. Introductory. II. The Granite and Gneissic Granite. IIIf. The Gabbro, Diorite, and Gneissice Diorite. TV. The Diabase. V. The Hornblende-Diabase. VI. The Hornblende-Picrite. VII. The Dolerite Dykes. I. InrrRopvuctoRY. Tue district to be treated lies to the west and south of the village of Sarn *, near the south-western extremity of Caernarvonshire. The eruptive rocks there exposed, excluding outlying patches, occupy an area of irregular shape, which extends about 52 miles from north to south, and has a greatest breadth of about 23 miles. This part of the country has received but brief notice from Sir A. Ramsay in his memoir on the “Geology of North Wales” +, and from Dr. Hicks ¢, who claims a portion of the area for his Pre-Cambrian systems. Several specimens from the district have been described by Professor Bonney § and the late Mr. Tawney||, and the latter has also made a few observations on the field-relations of some of the rocks; but with these exceptions we have no published information about the western part of the Lleyn peninsula, though there are probably few districts of equal size in Britain where so many interesting rock-types are to be met with. The rocks will be discussed in the following order :—Granite and Gneissic Granite; Gabbro, Diorite, and Gneissic Diorite; Diabase ; Hornblende-Diabase ; Hornblende-Picrite; and Dolerite. Some of these, however, are but little developed, and, for most purposes, the rocks of the district may be divided into two groups—an acidic, de- veloped in the north and west, and a basic and intermediate in the east and south. Mr. Tawney and Dr. Hicks have pointed out that the map of the Geological Survey does not correctly indicate the separation between the two groups, the extent of the “ green- stone” being unduly enlarged at the expense of the “syenite.” The accompanying sketch-map (fig. 1) is intended to show roughly the limits of the two sets of rocks; but much of the country is obscured by drift, and accuracy is impossible without better topographical maps to serve as a basis. * Sarn Meyllteyrn on the Survey Map, one-inch scale, sheet 76. Tt Mem. Geol. Sury. Gr. Brit. vol. iii. 2nd edit. (1881). t Quart. Journ. Geol. Soc. vol. xxxv. p. 298 (1879). § Geol. Mag. dee. ii. vol. vii. p. 207 (1880) ; Quart. Journ. Geol. Soc. vol. xxxy. p- 306 (1879). || Geol. Mag. dee. 2, vol. vii. pp. 207-215, and p. 456 (1880) ; vol. x. pp. 65- 68 (1883) ; see also Teall, ‘British Petrography,’ 1888. NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE. 443 Fig. 1.—Sketch-map of the Sarn district. (Scale 2 inch=1 mile.) ain dit 6 \ 1 i i SL See —— r>wsSs A \Y A 4 < S. Shale. S'. Indurated and spotted Shale. SS. Sandstone. G. Granite. Sf. Faults, a different version of the section. The actual contact of the two rocks is easily found, and the granite is seen to send out little tongues between the lamine of the shale. Specimens of the latter rock, in- durated and firmly adhering to the granite, may be obtained. At the back of the quarry the shale is clearly altered, and exhibits the little spots and nodules supposed to represent the incipient develop- ment of chiastolite. Another quarry, well within the boundary of the granite, shows entangled masses of baked shales. This is partly due to faulting; but here, too, good junction-specimens of the two rocks were procured. The granite in these quarries is quite typical of that which forms Mynydd Cefn-amwlch, and extends towards Sarn, Bryn-croes, and Llangwnadl. . At Meillionydd the junction is not exposed; but the quarry must be near the boundary, and the presence of fragments of indurated shale included in the granite is sufficient proof of the intrusive cha- racter of the latter rock. The granite is therefore of more recent age than the Upper Arenig strata. To assign an upper limit to the date of its intrusion is a * Rhos Hirwain is the low-lying tract to the west, and the conjunction of this name with the word Syenite on the Survey map is apparently uninten- tional. t Report Brit. Assoc. (Birmingham meeting) 1885, p. 669. NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE. 447 matter of mere conjecture; but the relation of the rock to subsequent earth-movements, of probably pre-Llandovery times, renders it likely that the granite belongs to the Bala age. It is impossible to say whether this plutonic mass was connected with volcanic centres ; acidic lavas and ashes are found, however, less than five miles to the east, and are associated with Bala strata. III. Tae Gassro, Diortre, anp Gnersstc Drortte. These rocks, grouped together for reasons which will appear, have not been noticed before. They occur only in two small patches, and are quarried in both places, viz. in the little hill of Craig-y-fael, two miles south-west of Sarn, and on the banks of the stream at Plas Llangwnadl. The Oraig-y-fael rock is, to the eye, a medium- or rather coarse- grained rock of granitic habit, apparently either a diorite or a gabbro. A similar or identical type is exposed above Plas Llang- wnadl; but going north we find the rock assuming a more or less gneissic and even almost a schistose appearance, becoming, as it seems, a hornblendic gneiss. The microscope explains clearly the relations of these various types. The typical rock of Craig-y-fael may be described as a partially amphibolized gabbro. It consists mainly of an aggregate of some- what altered felspars and grass-green grains of hornblende and augite, none of the constituents ever showing idiomorphic contours. The minerals seen in the thin sections are augite and diallage, horn- blende and actinolite, felspar, and a black opaque mineral, pre- sumably an iron-ore, with some pale green decomposition-products, which mostly present the characters of chloritoid. The black mineral forms shapeless patches without any indication of leucoxenic alteration, and is probably magnetite. The felspar is a plagioclase, showing the usual albite-twinning, sometimes crossed by twin lamelle on the pericline-law; the extinction-angles are those proper to labradorite. The crystalline plates are much strained and bent, so that the lamell are curved; it is possible, though not clear from the specimens examined, that the twinning may be in part induced by the strain. The augite is in long plates of a very pale greenish tint. It shows sometimes the ordinary augite-cleavages, but other plates have a very marked diallagic structure. In spite of decomposition, it can be seen that both augite and diallage are converted at the margins into hornblende. The hornblende is of a dull green colour, and the pleochroism is expressed by :—a, very pale to almost colour- less; 6, grass-green, rather pale; y, a rather deeper and bluish green. The usual prismatic cleavage-traces are seen in the more compact portions ; but a part of the amphibole is in granular masses or in blade-like imperfect crystals with actinolitic structure. There appears to be no augite or diallage in the Llangwnadl rocks, but their essential identity with the amphibolized g gabbro of Craig-y-fael can eer be doubted after an examination of the ted.G.5. No. 175 Qu 448 MR. A. HARKER ON THE ERUPTIVE ROCKS IN THE specimens and the slides. The process of alteration has proceeded further in the rocks on the edge of the district than in those of the central part. The rock exposed near the bridge where the main-road crosses the stream may be taken as a type of the massive diorite. The microscope shows but little of the black iron-ores, but there is a considerable quantity of sphene in brownish granules. These granules, with cleavage-traces and irregular fissures, are aggregated in small patches and strings between the grains of felspar and hornblende. The felspar is partly in granular patches, too much decomposed to show any structure. The hornblende is of a greenish- brown or brownish-green colour, and gives for the three axes of elasticity :—a, very pale to almost colourless; 6, rather deep brown with greenish tinge; y, slightly deeper tint of greenish brown. There are also very pale greenish actinolite-looking shreds amongst the felspar-grains. Near Plas Llangwnad1 the rock is more altered, and has in places a quasi-porphyritic appearance, owing to the granular felspar forming large patches. Here there is very little of the opaque iron-ore, but sphene is more abundant. The felspar has undergone a seemingly saussuritic change, but a little of it still preserves the original structure and appears to be labradorite. Still further down the stream, approaching the boundary of the area, the schistose appearance becomes more pronounced. A slide from this portion shows no new characters, except that the black iron-ore has entirely disappeared. The mode of occurrence of all these rocks, both at Craig-y-fael and near Llangwnadl, proves that they were intruded through the granite, doubtless in the form of gabbro. The hornblende may be supposed to be entirely of pseudomorphic origin, the change being probably assisted by the mechanical stress to which must be ascribed the schistose structure of the rocks about Llangwnadl. At Craig- y-fael, where the gabbro was protected by a large mass of surround- ing granite, the amphibolization is still imperfect. In the other mass, Where the conversion is complete, the schistose character becomes more marked towards the boundary, and it may reasonably be ascribed to the movements which produced the assumed fault. In confirmation of this, it may be remarked that the strike of the eneissic and schistose structures is the same as that of the fault, and the schistosity is shared on the other side of the boundary by the ashy-looking beds which represent, near Llangwnadl church, the so- called green schists. The production of sphene in connexion with this kind of metamorphism is too well known to require comment. The date of the gabbro and diorites is, then, more recent than that of the granite, but earlier probably than the fault; the rocks may be referred with some doubt to the Bala age. IV. Tae DraBase. The main mass of diabase in the district forms the curious conical hill named Clipiau-cilfinhir, half a mile west of Rhiw, rises in the NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE, 449 long ridge of Mynydd-y-Rhiw to a height of 1000 feet, is quarried further north near Cadern-y-groes, and extends in a north-north- easterly direction to 'yn-y-coed, half a mile south of Sarn village. Besides this, several sheets and dykes occur just west of Sarn ; and further west, at Ty-rutten, a tongue-shaped mass runs with the strike of the strata, leaving a narrow strip of shales between itself and the granite (fig. 3). This mass must abut at its southern extremity on Fig. 3.—Section from Pen-Craig to south of Sarn. (Length about 2 mile.) Pen- Road to Road to W. Craig. Aberdaran. Rhiw. HE. S. Shales, Upper Arenig or Lower Bala. G. Granite. D. Diabase, tongue at Ty-ratten, dyke and sheets near Sarn. f. Probable faults. the tongue of granite a little north of Miriau; but unfortunately their junction, on the right slope of the little valley, is not exposed. There are numerous diabase sheets and small bosses in western Lleyn, which will not be considered here, though some of them, such as the sheets at Llanfaelrhys and Tyn-y-rhedyn, have probably a cognate origin with the diabase of the Sarn district. The rocks are sufficiently alike to be described together, and present no very striking peculiarities. In hand-specimens the rock appears as a diabase of medium grain, greenish from decomposition- products, and showing distinct crystals of felspar. The microscope shows the original constituent minerals to be the usual iron-ores, plagioclase felspar, and augite; the secondary pro- ducts, leucoxene, calcite, zeolites, quartz, chloritoid minerals, and ferric oxide, do not require special notice. The magnetite and ilmenite, constantly the first-formed minerals, are fairly plentiful in rods and skeleton crystals. One or other of these constituents is always present, and frequently both in the same slide: there are not wanting signs of an intergrowth of the two minerals, or per- haps of magnetite and titaniferous magnetite. The plagioclase occurs in lath-shaped or, at least, elongated sec- tions, showing twin-lamellation on the albite-law. In the dykes and sheets near Sarn the felspars are often once twinned only, but in general a fine striation is seen between crossed nicols. The ex- tinction-angles agree with those of oligoclase and labradorite. The augite is very pale brown or almost colourless in thin sections, with the prismatic cleavage pronounced, and rarely traces of a pina- 2H 2 450 MR. A. HARKER ON THE ERUPTIVE ROCKS IN THE coidal cleavage. The well-known “hour-glass” structure is not uncommon. The mineral is either in ophitic plates or in grains between the felspars. Only occasionally, as at Castell Carron, does it appear with idiomorphic boundaries ; sometimes it shows twinning on the orthopinacoid. The structure of these diabases is rather variable. Sometimes they are ophitic, but the augite-plates are never of great size, and the more usual texture rather approaches the granulitic type. It does not appear that the basic rocks of this area bear out any rule associating the ophitic structure with the larger masses, and the granulitic with small dykes and sheets.- The types of structure seem rather to be connected with the relative proportions of the two minerals, the ophitic rocks being those which have the most abundant augite. These diabases afford fine examples of spheroidal jointing and the consequent weathering in concentric crusts. The spheroids vary in diameter from two or three inches to as many feet; often a cluster of small ones is included in one large shell. The spheroids are sometimes formed in the interspaces marked out by plane joints, but ~ the most regular examples often have no such relation. The great mass of Mynydd-y-Rhiw, especially in its northern and southern portions, is largely built up of spheroidally jointed rock. The contact-effects of the diabase upon the adjacent strata usually present no special features. In one case the strata of indurated shale show a curious modification. They are broken by joints parallel and perpendicular to the bedding into small rectangular blocks, in each of which lies an ellipsoidal nucleus. The ellipsoidal joints are from an inch or two to a foot in diameter. This is at the contact with a dyke 35 yards wide, about a quarter of a mile west of Sarn. The relations of the diabase to the other intrusive rocks can nowhere be demonstrated by actual sections, and the age of the mass is a matter for conjecture. It can only be said that the diabase cuts through Arenig or Lower Bala strata, while no rock of similar type is certainly known in Caernarvonshire of later age than the Bala. The presumption is therefore in favour of assigning the intrusion of the rock to the Bala age. V. Tue HornpienDE-DIABASE. Rocks of this family are largely developed in the southern part of the district. They are seen everywhere on Mynydd Penarfynydd, with the exception of the outcrop of hornblende-picrite on the west and south-west slopes. They form the whole of Mynydd-y-graig and its outlying spurs, the extent from south-west to north-east being about 12 mile. Hornblende-diabase may occur under the low ground north-west of Mynydd-y-graig, but probably the diabase extends as far as this. The same rock is found in force in the neighbourhood of Rhiw: it occurs a few hundred yards north of the NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE, 451 church, on the east side of the diabase-ridge, and can be traced southward to the coast at Tyn-y-borth, being quarried at Treheli. The microscopic study of these rocks reveals features of consider- able interest, and they will accordingly be treated in rather more detail than the foregoing rocks. Taking the hornblende-diabases of the district as a whole, the original constituent minerals are apatite, magnetite, picotite, ilmenite, felspar, olivine, augite, and hornblende. Among the secondary products we find in various slides leucoxene, kaolin, serpentine, magnetite, actinolite, a chloritoid substance, a radiating zeolite, calcite, and quartz. Apatite occurs but rarely, in large cross-jointed prisms. Original magnetite grains are frequent, and belong to an early stage of the consolidation. A few rounded grains, brown and slightly translucent, which accompany the magnetite, are referred to picotite. Ilmenite, in skeletons of intersecting rods, is found in one variety, otherwise abnormal. On the whole these rocks are poor in accessory minerals. A felspar of the plagioclase series is always abundant in good crystals, showing the usual forms. The crystals are sometimes simple, generally twinned once or twice, sometimes finely lamellated, and very rarely showing a cross-twinning corresponding to the pericline-law. The extinction-angles are usually nearest to those of labradorite, but some symmetrical sections extinguish at 40° from the twin-plane, indicating anorthite. Only one rock, that of Mynydd Penarfynydd, shows in places two distinct generations of felspar. With this exception the felspar is always of earlier formation than any of the augite or hornblende. Olivine has probably been an occasional constituent of the horn- blende-diabases here as elsewhere, but it is not now detected in any of the slides, and serpentine-grains which seem to result from it are not often seen. ‘There is, indeed, plentiful serpentine in many of the slides; but in some cases this substance clearly results from the alteration of hornblende, in others it probably comes from a rhombic pyroxene, while the mesh-structure so characteristic of pseudomorphs after olivine is rarely indicated. The augite is found either in good crystals or in ophitic plates and shapeless grains, the latter mode of occurrence being by far the more common. When crystals occur, they show in cross-section the usual octagon, the pinacoids being rather more developed than the prism- faces, while the terminal planes seem to belong to (111) and (001). The extinction-angle in a section parallel to the clinopinacoid is 39° or 40°. The prismatic cleavage is constantly well marked, and in a few cases pinacoidal cleavages were noticed, but never any diallagic structure. The augite is colourless or extremely pale brown in thin sections: only in one rock (summit of Mynydd-y-graig) is this seen to pass into augite of a deeper violet-brown with slight pleochroism. This and the occasional hour-glass structure recall the augite of some of the teschenites. Twinning on the usual law is sometimes ob- served, the orthopinacoid being twin-plane and face of composition. The hornblende rarely forms imperfect crystals, contained by the clinopinacoid and prism-faces, without terminations: in the large 452 MR. A. HARKER ON THE ERUPTIVE ROCKS IN THE majority of cases it occurs as ophitic plates, commonly including grains, cores, or nuclei of augite, as well as felspars and magnetite. The mineral is almost always deep brown in colour, with the usual pleochroism, the absorption being indicated by y> G>+>a. The maximum extinction-angle in vertical sections is 18° or 20°. A greenish-brown tint is occasionally seen with the brown. The horn- blende is normally “‘ compact ” and well-cleaved, the green portions sometimes fibrous. The relations of the hornblende and augite are worthy of notice, and prove that the same brown, compact hornblende may be either original or a product of amphibolization. When augite is included in the hornblende, there are three cases to be distinguished. In the first place, original hornblende may include augite-grains in the same way as it includes felspar-crystals or magnetite. When this is so, the enclosed grains are generally of rounded shape with a very definite and comparatively smooth boundary; there is no crystallo- graphic relation between the two minerals, and if two or more grains occur in the same plate of hornblende, they are differently orientated. Rarely, asin the quarry on Mynydd Penarfynydd,‘good — idiomorphic crystals of augite are included in the hornblende. Secondly, a crystal or plate of augite becomes partially converted into hornblende, chiefly round its margin, the two minerals then having the vertical axis and plane of symmetry common. Since this amphibolization probably involves a change of chemical com- position, the term paramorphism is not strictly applicable, and we must call the process pseudomorphism, or where only the border is affected, perimorphism. If the original augite had crystal-contours the secondary character of the hornblende is obvious; in other cases it can generally be inferred from the extremely intricate and ragged appearance of the boundary between the augite-core and the investing hornblende. If the augite is twinned, the resulting hornblende is twinned about the same plane. Where several cores of augite are included in one hornblende-plate, they all have, of course, one orientation. ‘The pseudomorphic or perimorphic horn- blende has precisely the same characters as the original hornblende. Sometimes we may see a crystal of augite both moulded by horn- blende and partially psendomorphosed, the two kinds of hornblende being undistinguishable from one another. There is a third way in which hornblende may include augite, and this has rarely, I believe, been specifically described in British rocks*. It appears that while a nucleus of augite was growing the magma became so altered that after a certain point of time hornblende-substance was deposited instead of augite, this hornblende growing upon the augite kernel with the usual crystallo- graphic relation between the two minerals. This, if I understand aright, is what Rohrbacht has described in the teschenites of Silesia under the name of ‘“‘erganzende” or complementary horn- * The picrite of Inchcolm exhibits good examples; see, e. g., Teall, ‘ British Petrography,’ plate vii. (1888). Tt Tschermak’s ‘ Mittheilungen,’ 1886, p. 84. NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE. 453 blende. It appears to differ from the more ordinary “ intergrowth,” in that the whole of the augite was formed before any part of the hornblende. When both the augite-nucleus and the hornblende- border are twinned, the twin-planes, though of course parallel, are not necessarily coincident. Sometimes, as on the south-east side of the crest of Mynydd-y-graig, the hornblende thus formed has idio- morphic crystal-boundaries, and its original nature is conclusively demonstrated. But when once admitted and looked for, this complementary hornblende is found to be by no means uncommon : it is distinguished from the perimorphic hornblende by its boundary against the augite being much less irregular, and from original hornblende enclosing augite-grains by the correspondence in crys- tallographic orientation of the two minerals. We must recognize, then, as distinct cases :— 1. Original hornblende enclosing augite-grains, without crystallo- graphic relation ; 2. Perimorphic hornblende (secondary) bordering augite-cores, with crystallographic relation ; and 3. Complementary hornblende (original) surrounding augite- nuclei, with crystallographic relation. One or more of these is found in all the slides examined; but I have not yet certainly recognized the first and third in the same specimen. ‘This is, perhaps, in accordance with what might be expected ; for we must suppose in the former case a pause between the consolidation of the augite and that of the enclosing hornblende, and such a pause would presumably be unfavourable to the formation of complementary hornblende upon nuclei of augite. Another kind of amphibole may also be mentioned, though it is less common here than in some other hornblende-diabases, such as those of Pen-y-rhiwiau, near Clynog-fawr, Caernarvonshire, of Jersey, of Little Knott in Cumberland, and from near Llanerchymedd, in Anglesey*. This is the ‘“‘secondary enlargement” hornblende of Van Hise‘, first described in eruptive rocks by Becket. It is a growth of hornblende-substance entirely posterior to the con- solidation of the rock, but proceeding in crystalline continuity with preexisting hornblende, so as to border the original crystals, fill the interstices between them, or form a narrow and ragged fringe inside the walls of an included grain of serpentine. Evidently its deposi- tion can only proceed concurrently with the destruction of some other mineral. This later growth of amphibole is clear and colour- less or pale green; it constantly gives rather higher polarization- tints than the brown hornblende: frequently it has the cleavage- traces but little pronounced. Such hornblende, forming a “ secondary enlargement” of original and perimorphic crystals, is found in several parts of the district. Becke also describes a similar horn- blende-growth bordering original augite-crystals ; but of this I have found no evidence in the Sarn district, though it is well seen in a * ‘Geol. Mag.’ dec. 3, vol. iv. p. 552. t ‘Amer. Journ. Sci.’ ser. 3, vol. xxxiii. p. 385 (1887). { Tschermak’s ‘ Mittheilungen,’ vol. v. part ii. (1883). 454 MR. A. HARKER ON THE ERUPTIVE ROCKS IN THE diabase from Bodowen, Anglesey, and in many of the diabases of central Caernarvonshire. The chief secondary products of the hornblende are magnetite, in dust and in granules, serpentine, often preserving something of the structure of the parent mineral, and sometimes a feebly polarizing pale green substance of the chloritoid family. One slide from Mynydd-y-graig shows, however, the brown compact hornblende passing over into a fibrous mineral presumably actinolite. The hornblende first becomes pale and greenish, and then breaks up into erass-green fibres, which from parallel become divergent, and are seen to be imbedded in a colourless, brightly polarizing mineral which has all the properties of the “‘ secondary enlargement” horn- blende already described. The change is accompanied by a copious separation of granular magnetite, which finally forms a dense border to the altered crystal. The augite of these rocks, being protected by the hornblende, is usually quite fresh. All the rocks here described contain augite, as a rule partially amphibolized, and most, if not all, have original hornblende in addition. As some confusion exists with reference to the application — of such terms as proterobase and epidiorite, I have judged it advisable to group all these rocks together under the more general title of hornblende-diabase. Their structure is almost without exception that of an ordinary ophitic diabase, but specimens taken at the summit of Mynydd Penarfynydd show a structure which must be called porphyritic in the sense of Rosenbusch*. There are not only two sets of felspars, but the augite also appears of two generations, the earlier one being in idiomorphic crystals. A peculiar aspect is given to some of the more felspathic varieties by a tendency of the larger felspars to collect in patches; this type of structure is, perhaps, comparable with that which Professor Judd has termed “ glomero-porphyritic.” The hornblende-diabase often contains coarsely crystalline con- temporaneous or segregation-veins. ‘They are on the whole more felspathic than the surrounding rock, and contain crystals of horn- blende up to one inch in length, often very perfectly formed. The geological relations of these rocks will be considered in connexion with those of the hornblende-picrite, which is intimately associated with them. VI. Tur HornBLenpDE-PIcRItTE. The rock which forms the western slopes of Mynydd Penarfynydd is unique in the district. Professor Bonney has given it the name of hornblende-picrite, and it must be regarded as the type of this well-marked and interesting species. The rock occurs in distinct parallel banks to a total thickness of 200 or 250 feet, with a dip of 35° or 40° towards S. 30° E., the same as that of the neighbouring Arenig shales. Owing to ‘this inclination, the picrite emerges from the sea under the precipitous cliffs of Trwyn-talfarach, rises on the south-west slope to a little * ‘Massigen Gesteine,’ new ed., 1886. NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE. 455 below the signal-staff, follows the trend of the hill-side in a north- easterly direction, and crosses over the ridge, where it begins to sink towards its northern extremity. The topmost banks are overlain by the hornblende-diabase, which forms the greater part of the hill, and hornblende-diabase also occurs at the very base, thus intervening between the picrite and the subjacent strata. In the field and in hand-specimens the appearance of this hand- some rock is very striking. Most conspicuous is hornblende in large black crystals with lustrous cleavage-planes. On _ closer examination these planes are seen to be studded with rounded, dull spots, which represent grains of olivine more or less serpentinized. Besides this, flakes of a golden-brown mica are often plentiful, lying on the cleavage-planes of the hornblende, and some parts of the rock show white crystals of felspar. The microscope shows the original minerals of the hornblende- picrite to be magnetite, olivine, felspar, augite, hornblende, and biotite: among the secondary products are magnetite, serpentine, hornblende, biotite, asbestos, a mineral of the chloritoid family, calcite, and dolomite, with rarely an aggregate similar to that which has been named saussurite. Original magnetite is not common ; it sometimes occurs in cubes, and is the earliest-formed constituent. Picotite has not been observed. Olivine is always one of the most abundant minerals present; it rarely shows crystal-contours, and is almost always in rounded grains imbedded in augite or hornblende. Twinning is rare. The grains sometimes show fissures corresponding to the two pinacoidal cleavages, but more commonly are traversed by irregular cracks. Under a high magnifying-power some of the olivine shows flat rectangular cavities or “negative crystals” containing dendrites of magnetite, identical with those figured by Professor Judd in a picrite from the Isle of Rum*. As the Penarfynydd rock is probably of Upper Cambrian (Bala) age, its resemblance to a Tertiary rock, extending to such minute details, is a point of some interest. The conversion of the olivine into serpentine is seen in every stage from fresh grains of olivine to complete pseudomorphs. The process begins along the fissures with the separation of mag- netite dust, which, when plentiful, collects in clotted granules and strings. Serpentine is next formed on the borders of the fissures in fibres perpendicular to the walls. This serpentine is doubly refracting and apparently uniaxal: the remaining kernels of olivine are then gradually converted into serpentine, which either shows a confused structure or is sensibly isotropic. Sometimes, as a last stage, there is a seeming reabsorption of the deposited magnetite as described by Wadswortht. Irregular fissures sometimes radiate from the altered grains, traversing the surrounding minerals, and these fissures are injected with serpentinous matter: they may be * Quart. Journ. Geol. Soc. vol. xli. p. 385, pl. xii. fig. 5 (1885). t ‘ Lithological Studies,’ p. 172, &. (1884). 456 MR. A. HARKER ON THE ERUPTIVE ROCKS IN THE ascribed to the increase in bulk of the grains consequent upon the process of serpentinization*. Felspar, when it occurs in the hornblende-picrite, is either in small slender crystals, simple or once twinned, or in large irregular plates enclosing olivine. The extinction-angles observed agree with anorthite. The mineral is probably always of earlier con- solidation than the augite, and is moulded by the plates of horn- blende. The augite is of the usual very pale brown tint or almost colour- less, and has the prismatic cleavage well marked. It is almost always in the form of irregular plates, or forms a core to the horn- blende. In rare cases, however, it has erystal-outlines, the cross section being a regular octagon due to the equal development of the prism and pinacoids. The hornblende is of the same rich brown colour as in the hornblende-diabases, but this passes occasionally into green, which gives, for vibrations parallel to the axes of elasticity :—a, very pale brown; £6, pale olive-green; y, rather pale grass-green. The brown hornblende also passes, in places, into a colourless variety. The usual prismatic cleavage is well seen in the slides, and occasionally a cleavage parallel to the clinopinacoid. Twinning on the orthopinacoid is only rarely seen. The hornblende never shows idiomorphic boundaries, and it usually occurs in close relation with augite. Either a plate of augite has a partial or complete border of hornblende, or a horn- blende plate encloses a core of augite, the boundary between the two being often exceedingly ragged and labyrinthine. The horn- blende and augite of each plate have the vertical or c-axis and the plane of symmetry common, but are apparently in reverse position to one another. This appears from the fact, verified in several instances, that in a clinopinacoidal section the extinction-angles are about 40° for the augite and 20° for the hornblende on the same side of the cleavage-traces. Some slides show little or no augite. The relations of the two minerals are, on the whole, in accord with the idea that the bulk of the hornblende is a later formation at the expense of augite; but itis not safe to conclude that this is so of all. Indeed, that some of the hornblende is original, is evident from the fact that it not unfrequently encloses distinct grains of augite without any definite crystallographic relation. A brown mica with the characters of biotite is almost always present, and sometimes in such quantity as to give a distinct varietal character to the rock in which it occurs. Normally the mineral is brown, with the usual intense dichroism, but it often becomes paler and even almost bleached. It also passes at the edges of the flakes into a mineral which gives a grass-green colour for vibrations parallel to the cleavage-traces and a golden-brown for the perpendicular direction: this seems to be the substance which Mr. Teall identifies as chlorite+. The biotite has two modes of origin. It is in part original, being then usually later than the * Cf. Judd, Quart. Journ. Geol. Soe. vol. xlii. p. 86 (1886). t British Petrography, p. 98, 1888. NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE. 457 felspar and earlier than the hornblende. Another portion seems to be of secondary origin, and connected with a special mode of alteration of the hornblende. In some cases this mineral, as a first stage, takes on a lamellar structure parallel to the orthopinacoid, and from this the biotite-flakes are developed*. More commonly the mica is developed on the cleavage-planes of the hornblende. It is possible that this should be regarded as an original intergrowth of the two minerals, the law of association being that given by Rosenbusch and others. The ordinary secondary products from the felspar, hornblende, and biotite demand no special notice. We may remark, however, the presence in some slides of a rather pale-green actinolite in blade-like crystals with a pinacoidal cleavage. The hornblende-picrite presents some peculiarities of structure due to the arrangement of its constituent minerals, and these variations are much more striking in the field than in hand- specimens or thin sections. The smooth surface of boulders, both of hornblende-diabase and hornblende-picrite on the beach below Mynydd Penarfynydd and at Y Graig-ddu, often show a curious mottled aspect, which consists in a mingling of dark and light patches or a separation of white spots on a black ground. This kind of aggregation of the several constituents produces on the rock-surfaces in situ a pitted or honeycombed appearance due to differential weathering. When the component minerals are more evenly distributed, the rock either weathers into compact blocks, or in some parts of the picrite-mass shows a fluted or grooved aspect. This last-mentioned appearance seems to be caused by the difference between bands alternately rich and poor in olivine, a character noted by Reusch in the saussurite-gabbros of the Bergen districty. There are even distinct dark bands less than an inch in width, which under the microscope appear as veins entirely composed of partially serpentinized olivine with much secondary magnetite. The fine section of hornblende-picrite below the trigonometrical signal-staff on Mynydd Penartynydd shows very clearly the strati- form alternation of the honeycombed and the compact and fluted varieties. The former is in greatest force in the middle half of the section. The picrite often contains coarse segregation-veins similar to those of the hornblende-diabase. The intrusive nature of the basic rocks of this district has never been disputed. Wherever the Arenig strata are seen in the vicinity of the eruptive rocks, their contact-alteration is very evident. The shales become hard and flaggy, losing their finely laminated structure and changing colour, while grey spots and yellowish-grey granular streaks make their appearance. The Mynydd Penarfynydd mass, exhibiting, as it does, the picrite as well as the hornblende-diabase, may conveniently be considered first. The boundary between these two rocks is a very definite one. * This is well exhibited also in the hernblende-picrite of Schriesheim, where, however, both hornblende and mica are bleached. t Fossilien-fiihrenden krystallinischen Schiefer, &c., 1883. 458 MR, A. HARKER ON THE ERUPTIVE ROCKS IN THE We pass at once from perfectly typical hornblende-picrite to a rock in which no olivine can be detected, while felspar, instead of being locally and rather sparingly present, becomes essential and abundant. Nevertheless it cannot be doubted that the two rocks form parts of one and the same intrusive mass. Mr. Tawney, who noticed that the hornblende-diabase (“ diabase” in his description) occurs both below and above the hornblende-picrite (his “ olivine-diabase ”’), suggested doubtfully that the olivine-bearing rock was intruded into the other ; but his examination of the locality was rather a cursory one, and he appears not to have distinguished between the hornblende- diabase and the felspathic variety of the picrite. The rocks have, indeed, many characters in common; but what unites most clearly the picrite and the hornblende-diabase as the products of one igneous intrusion or set of intrusions is the behaviour of the segregation- veins at the junction. These veins, already mentioned, pass from one rock to the other, so that it is impossible, where they occur, to draw any line of demarcation. The direction of the plane of division of the hornblende-diabase and hornblende-picrite is also the direction of the banks or quasi- strata of the latter rock, marked by the alternation of different lithological types ; also of the thin olivine-veins, and of the coarse segregation-veins when these show any regularity of disposition. Further, the base of the whole igneous mass is a plane parallel to the above and agreeing with the stratification of the sedimentary rocks below, so that the actual junction is a definite bedding-plane of the shales (fig. 4). The mode of occurrence of the mass is there- Fig. 4.—Ideal section through the southern end of Mynydd Penarfynydd. (Length % mile.) N.N.W. 8.8.E. Se ee ee. ~ ~ x . s x . ~ . ~ . s, . A. Upper Arenig strata. D. Diabase of Tyn-y-rhedyn sheet. HD, Hornblende-diabase, and P, Hornblende-picrite of the Penarfynydd laecolite. fore similar to that of the well-known “laccolites” of Southern Utah *, with the difference that, instead of being homogeneous, it * « Geology of the Henry Mountains,” U.S. Geol. Surv. 1880. NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE. 459 presents a stratified: arrangement of varying lithological types. Judging by the outcrop and observed dip, the Penarfynydd laccolite must have a diameter of not less than three quarters of a mile and a thickness of more than a thousand feet. These dimensions are exceeded by many of the trachytic laccolites described by Gilbert. On Mynydd Penarfynydd the beds which formerly arched over the roof of this great “ stone-cistern” have been entirely removed by denudation. There are also complications arising from the effects of the subsequent earth-movements by which the rocks of North Wales were disturbed from their horizontal position. The injection of the laccolite between Upper Arenig strata, doubtless a process accomplished by many successive influxes of magma of varying composition, clearly took place when the strata were horizontal ; and the whole mass was afterwards tilted over into an inclined posi- tion without other disturbance. Under the laccolite the shales have been protected from the lateral pressure by the stubborn resistance of the overlying eruptive mass, and present accordingly a uniform inclination. ‘To the west of Penarfynydd, on the other hand, the strata are much disturbed, with conflicting dips at high angles, the rocks here haying been crushed by the thrust from the north-west against the unyielding igneous mass. The Penarfynydd laccolite is the only one which can be clearly made out in the field. It is, however, a reasonable conjecture that the mass of hornblende-diabase constituting Mynydd-y-graig is another and larger laccolite, injected at a later time and on a slightly higher horizon, and modified in form at its south-western edge by the mass of Mynydd Penarfynydd. The field-relations of the rocks about Rhiw are too much obscured by surface-deposits to admit of any definite conclusions. Though the hornblende-diabase never exhibits the strikingly stratiform appearance of the hornblende- picrite, there seems to be a certain constant difference between different parts of the large masses. The rock which extends from Careg-llefain along the ridge of Mynydd-y-graig is readily dis- tinguishable from that exposed on the south-eastern slopes. The hornblende-diabase north of Rhiw resembles that of the base of the Penarfynydd laccolite, while the rock of Plas Rhiw and Treheli is of the Careg-llefain type *. The date of the picrite and hornblende-diabase intrusions is a matter for inference only. If wesuppose, with Sir A. Ramsay, that the disturbance of the strata was effected in pre-Llandovery times, these eruptive masses, which share that disturbance, must be referred to some part of the Bala age. Assuming this, the absence from the district of any contemporaneous lavas of like composition is best explained by supposing that the whole of the hornblende-diabases were injected in the form of laccolites. * Specimens from Treheli and from Mynydd-y-graig have been described by Mr. Tawney. 460 MR. A. HARKER ON THE ERUPTIVE ROCKS IN THE VII. Tue DotEertre-Dyxes. The last rocks to be described, and that very briefly, occur as dykes of no great width cutting through the larger igneous intru- sions of the district. These dykes are seen in various localities to intersect the granite, the diorite, and the hornblende-diabase ; and although I have not recognized them as yet in the diabase, this is owing, in all probability, to the difficulty of distinguishing in the field between the latter rock and the dolerite, The larger intrusive masses and the dykes and sheets of diabase we have seen reason to assign to the Bala age; the dolerite is most likely referable to a much later period. In hand-specimens the dolerite is of medium or fine grain, with well-pronounced ophitic structure, and of a dark colour, becoming greenish in the most weathered parts. It appears to consist of felspar, magnetite, and augite, and the microscope does not discover any other constituents. The magnetite, either in granules or in octahedral crystals, is one of the first-formed products of consolidation, though occasionally it is seen to be penetrated by some of the smaller felspars. Of ilmenite there is no indication in the slides examined. The felspar is constantly of two distinct generations. Of these the earlier is clearly anterior to the augite in the order of consoli- dation. It offers elongated sections with a fine lamellation on the albite-type and frequently Carlsbad-twinning in the same crystals. Judged by the extinction-angles the felspars are between oligoclase and labradorite. The later generation of felspars occurs in more equidimensional crystals, with rarely any trace of idiomorphic boun- daries. ‘They are never so closely lamellated as the earlier felspars, but are marked by astrong zonary banding or shading in polarized light. They belong to about the same stage of consolidation as the augite. The augite, though pale brown, is never so nearly colourless as the augite of the diabases and hornblende-diabases of the district. It even shows in some cases a scarcely perceptible dichroism, chang- ing from a rosy to a yellowish tint. The mineral, with the usual cleavage well pronounced, occurs in crystalline grains or ophitic plates moulding and enclosing the earlier felspars, and occasionally moulding to some extent the later felspars also. The structure of the rocks is commonly ophitic, though there is sometimes a tendency to pass into a partly granulitic type. Not recognizing geological age as an essential factor in lithological classification, I have applied the name dolerite to these rocks, because, by the development of a later generation of felspars, they exhibit the “‘ norphyritic ” structure of Rosenbusch, and are thus separable from the diabases, in which the felspars belong all to one stage of consoli- dation. rom the type of diabase so largely represented in the Sarn district these rocks differ, not only in this recurrence of felspar in a second generation, but also in the characters of the felspars, in the deeper colour of the augite, and its frequent occurrence in ophitic NEIGHBOURHOOD OF SARN, CAERNARVONSHIRE. 461 plates of considerable extent, and in the absence or rarity of ilmenite in the dolerites. In all these and other characters the rocks in question have close affinity with the dolerites of other parts of Caernarvonshire and Anglesey. Similar dykes on the shores of the Menai Straits cut through Carboniferous strata *; and others in the Anglesey coal-field are demonstrably post-Carboniferous and pre- Permian t. Such evidence as is obtainable points, then, to the con- clusion that the dolerite-dykes of the Sarn district, to which we may add some of those which intersect the neighbouring “ green schists” +, were injected in the interval between the deposition of the Carboniferous and the Permian formations. Waiving this point, however, and excluding the dykes and minor eruptive masses from consideration, we find that the district of Sarn, probably during the age in which the Bala rocks were laid down, was the theatre of igneous activity on a large scale. The strata were invaded by eruptive magmas of very different chemical consti- tutions, and rocks of widely diverse characters have resulted from the consolidation of those magmas ; so that we find, speaking broadly, acidic rocks occupying the northern and western portions of the district, intermediate or sub-basic forming a broad band across the middle, and basic and ultra-basic developed in the south. These latter, the heavier materials, appear to have spread in the form of laccolites, possibly at a considerable depth ; the magma which was the origin of the granite may, on the other hand, have been in con- nexion with some of the extrusive or volcanic outflows which are so striking a feature of the Bala stage in Caernarvonshire. The isolated intrusions of gabbro cannot safely be correlated with other rocks in the area: their passage into hornblendic rocks, and the evident relation of that change to the coming in of the schistose character, though points of novelty in North Wales, are closely paralleled in many other districts with which geologists have been made familiar. [ Note.—The specimens and slides illustrating this paper are in the Woodwardian Museum at Cambridge. | Discussion. Mr. Tzatt would have been glad to have heard more of the details of the paper before attempting to criticize it. As a point of nomenclature it would be satisfactory to know if we should have different names for rocks containing primary or secondary horn- blende. In the mass of diabase and picrite there seemed to be a differentiation and coming in of parallel structures ; in this direc- tion we may hope for a solution of the problem of the origin of eneilsses. * Geol. Mag. dec. 3, vol. iv. p. 409 (1887). t Ramsay, loc. cit. p. 264. + The igneous mass south-west of Aberdaron, terminating in the headland of Pen-y-cil, also has two generations of felspars, but differs in other respects from the dolerite of the dykes in question. 462 ON THE ERUPTIVE ROCKS OF SARN, CAERNARVONSHIRE. Prof. Brake had already committed himself as regards these particular rocks. His views and those of the Author in the main agreed and were adverse to Dr. Hicks’s interpretation, but he had not previously known of the evidence of their being intrusive into the later formations. He doubted if the difference between the granite and the diorite was well made out. The “granite” becomes a hornblende-gneiss near the ashy series, where he thought the junction was not a faulted one. He also had his doubts as to the diabase being strictly intrusive. On the whole his conclusions were not very different from those of the Author. Mr. Warts regarded the paper as a description of a petrographical complex, of the nature required by modern theories of meta- morphism. He agreed in the making use of cleavage to ascertain the age of the rocks. As regards structural relations, he rather doubted the analogy with laccolites, which generally occur in the main anticlines of strata. The question of segregation towards the bottom of the mass was interesting if the same intrusion is really more basic towards the bottom, but there may have been distinct intrusions. Judging from recent experience in Shropshire, there appeared to be evidence of a sequence in rock-series with a regular fall in the percentage of silica. Prof. Hueuexs referred to the protrusion of solid granite in ex- planation of some marginal faults, and to certain fossiliferous zones which defined the stratigraphical position of the sedimentary series in which the rocks described by Mr. Harker occurred. He spoke of the intermixing of the hornblende-diabase and the picrite, and thought that the boulders of hornblende-picrite of North Wales represented only portions of the well-known hornblende-diabase- dykes of the district. Mr. Rurisy said that the comparison with laccolite rather troubled him. These might be lenticular patches rather than laccolites. The AvtHor was disposed to accept Mr. Teall’s suggestion with respect to nomenclature. The schistose granite mentioned by Prof. Blake he had not seen; he thought it might be simply fluxion-struc- ture. Referring to thestratified appearance in the hornblende-diabase and hornblende-picrite, he thought there was no great division in time. Some small masses resembling laccolites do occur in relation to earth-movements elsewhere in Wales. His section was an ideal one; the pipes were not always laid down even in exposed lacco- lites. The Anglesey rocks were only locally picrites. THE MONIAN SYSTEM OF ROCKS. 463 32. On the Montan System of Rocks. By the Rey. J. F. Braxz, M.A., F.G.8S. (Read March 14, 1888.) [Puatz XIII. ] INTRODUCTION. Is there no order in Pre-Cambrian rocks? Do they consist in one area of great undulating masses of gneiss, in which those who have studied them refuse to recognize any stratigraphical sequence, and in another of tiny fragments of formations, two or three of which may be contained within an area of a few square miles? and are these types in no way connected? Such were the questions which forced themselves upon me after brief consecutive visits to the High- lands and St. David’s. Consulting my friend Dr. Callaway on these points, he advised me to go to Anglesey, where I should find rocks that might fairly be compared with the gneiss of the Highlands in character, in close proximity to, if not associated with, volcanic rocks of the type of St. David’s. J went; and after three years’ work in summer and spring vacations have arrived at conclusions which I now venture to lay before the Society. But in the forefront of this inquiry we are met by the fact that Sir Andrew Ramsay, who knows the district as one knows one’s native hills, has declared that there are no Pre-Cambrian rocks in Anglesey at all*. Can we ignore this fact? or must we not first ascertain the reasons which have led to this conclusion? If after a study of the area, sufficiently prolonged to place one’s self somewhat on a level with his knowledge of the rocks, one reads his words, they strike one as so masterly, that if his conclusions are not correct, the correction of them must be undertaken on the spots whence they were drawn, and the cause of error pointed out. To prove the existence of Pre-Cambrian rocks in Anglesey it is necessary to establish two points. First, that the rocks we assign to that age are overlain, unconformably if possible, by true Cam- brian strata; and secondly, that they are so important in develop- ment, and so distinct in character, that we cannot consider them merely lower and metamorphosed portions of the same system, separated by a mere local unconformity 7. In the examination of the question, the second of the above points is naturally taken first, since it is necessary to become acquainted with the lower rocks themselves, in order to appreciate any unconformity or overlap of the Cambrian that may exist. And as the examination goes on, the importance of this point becomes so impressed upon the mind, and its proof becomes so thorough, that one is convinced that the first point must be true, whether it can actually be proved or not. But in the demonstration to others it is best to take them in the logical order. * Mem. Geol. Survey, vol. iii. t See Dr. A. Geikie, Quart. Journ. Geol. Soc. vol. xxxix. p. 291. ew. Go. Ss, No, £75. aT A64 REV. J. F. BLAKE ON THE Pre-Camprian AGE oF AnGLESEY Rocks. It may well be considered that recent literature has already proved this point, so far as the direct evidence of unconformity is concerned. This evidence may be of two kinds, that derived from actual stratigraphical relations, and that derived from included ~ fragments. Of the former kind we have an example in Prof. Hughes’s admirable description of the basement-beds of the over- lying series*. Of the latter kind, are the statements by several authors that the conglomerates near Llanfaelog contain a large pro- portion of pebbles derived from the neighbouring rockst. The bearing of these observations depends on the age of the conglome- rate. Now on this matter Sir A. Ramsay says, on the authority of Mr. Salter, that the “ fossiliferous grits do not necessarily represent the very base of the Bala” t. Prof. Hughes, however, has shown that the fauna may be more correctly referred to the Arenig§. He would even introduce the Tremadoc, though Dr. Callaway has, I think, conclusively shown that this is not warranted by the facts ||. Even so, however, another statement by Sir A. Ramsay remains | untouched, that ‘no Lingula-flags have yet been detected in the country, and it is probable that they have been unconformably overlapped before reaching this northern area. .for they are reduced ....between Merionethshire and Llanberis, and seem to have almost or altogether thinned away before reaching Bangor.” The whole of the above-mentioned observations, therefore, only go to prove that the rocks in question are Pre-Ordovician, a result freely admitted by Sir A. Ramsay as perfectly consistent with their Cambrian age; though he undoubtedly regarded the granite as of Post-Cambrian, though ef Pre-Bala age, which is all that the con- glomerates, if themselves of Bala age, would prove. It would seem as if misunderstanding had been introduced here by the use of the name Cambrian for strata which Murchison had already defined as Lower Silurian, at a time when the geology of “Cambria” was still in confusion, and which have a distinct and unconformable base-line. Thus, the Pre-Cambrian age of the Anglesey rocks is not proved by these writers. Prof. Bonney 4], however, in a recent paper does supply the needful proof, though he appears to rely more on differences in amount of metamorphism than on the stratigraphy. He describes the section now exposed in Baron-Hill Park, near Beaumaris. Here, in the roadside cutting, the schistose masses are seen to be suddenly re- placed by a group of rocks which may with perfect safety be iden- tified with some of the Cambrian rocks of Bangor, which lie below the felsitic conglomerate. They consist, as Prof. Bonney states, of grits, porcellanites, and hilleflintas, and, at the summit, of a red * Quart. Journ. Geol. Soc. vol. xxxviii. t Callaway, Quart. Journ. Geol. Soc. vol. xxxvii.; Hicks, zbid. vol. xl. t Mem. Geol. Surv. vol. iii. 1866, p. 193. § Quart. Journ. Geol. Soc. vol. xxxyi. || Zbcd. vol. xxxvii. 4 Jbid. vol. xxxix. MONIAN SYSTEM OF ROCKS. 465 felsitic conglomerate with large pebbles. The exposure of these rocks is not a large one. ‘They form a superficial patch for about half a mile. At their northern end the schistose masses reappear within a few yards of the uppermost conglomerate, so that the junction can scarcely be anything but afault. At the southern end, however, described by Prof. Bonney, the lowest blue grit may now be seen to have its base continuous with the surface of the older rock from which it has been taken off up to a joint face. The junction here, therefore, is not a fault, but the grit lies on the surface of the other rock, and is as much unconformable as it can be, seeing there is no definite bedding in the schistose mass. These schists are, therefore, definitely Pre-Cambrian. Similar and confirmatory evidence can now be brought forward from the neighbourhood of Red-Wharf Bay. On the east side of this bay may be seen a “‘ feature ” which runs, on the Ordnance map, from Wern to Llaniestyn. On the south-west of this line, and forming the escarpment, we find the schistose rocks, with the orien- tation of their folia striking directly at the line. On the north- east, and generally at a lower level, forming another feature running thence towards Llandona, we find the same grits, halleflintas, and conglomerates as at Beaumaris, with their bedding parallel, or nearly so, to the escarpment. For more perfect satisfaction I have examined microscopically the rocks from these two localities, and compared them with those of Bangor, and they are found to agree in character. But there is really no need for this; no one could mistake their common character, even in the field. To my own mind, however, the most perfect proof of unconformity is derived, not from isolated sections, but from the same basal rocks lying in different localities upon different members of the older series, without the latter in any way dying out. This proof can only be afforded after obtaining an acquaintance with the sequence of the older rocks ; when this has been done, it is seen that the northern patch lies on the older, and the southern on the younger portion of the series. I cannot conceive a more perfect stratigraphical proof of the point in question. Yet it appears to me that it is the observation of a portion of these facts that led Sir A. Ramsay to exactly the opposite conclusion. He states that the ‘‘ grounds on which the larger part of Anglesey is considered to consist of Cambrian rocks” are as follows :—“ If we prolong the strike [of the Bangor rocks] and of the overlying Silurian beds from Bangor, under the Lavan Sands to Beaumaris, and from thence to Glan-y-ffynon at the east point of Red-Wharf Bay [exactly the two localities above described], we find an associa- tion similar to that of Bangor, black slates resting on green, grey, and purple schists and grits, which, however much foliated and contorted, still bear a strong resemblance to the Cambrian rocks of Bangor.” Hence it is evident that Sir A. Ramsay has seen these Cambrian rocks in Anglesey, has recognized their resemblance to those of Bangor, but has conceived that there was a passage from these rocks into the schists, instead of an unconformity between re a 466 REV. J. F. BLAKE ON THE them. It is here, then, that the whole difference lies. Given this starting-point, and the consequences which would naturally follow, however remarkable, might be loyally accepted. Whether the clearer section now exposed in Baron-Hill Park would have modified his views I cannot say. We may suppose from his words that he worked this district from the east, and by the gradual changes ob- served in descending the rocks of Bangor he was prepared for a further change into schist, and this change would be subsequently discounted in ali his researches to the west. Had he commenced on the west instead, and, wearied with the monotony of the schists, come suddenly on these grits and halleflintas, he would have been more struck by the change, and would perhaps have inquired more closely whether they were conformable or not. Nor could he have assigned the differences to metamorphism without a much freer belief in its power to change the constitution of a rock than the teachings of the microscope will now permit. DEscRIPTION OF THE PRE-CAMBRIAN Rocks oF ANGLESEY. INTRODUCTION. The second point to be proved is the importance and distinctness of the series of rocks which thus underlie the Cambrian. From such a point of view they require a fuller and more pictorial description than if they were merely altered forms of beds well known elsewhere. It may be thought, however, that they have been adequately de- scribed already, and certainly there are two descriptions extant, one from a Cambrian, the other from a Pre-Cambrian standpoint. The first of these, contained in vol. iii. of the Memoirs of the Geological Survey, is chiefly devoted to the illustration and explanation of the contortions and metamorphism to which the rocks have been sub- jected ; so that, full as it is of beautiful touches which recall vividly to the reader the facts he has observed in the field, it is quite inadequate as an account of an important system of rocks. The second, by Dr. Callaway, published in the Quarterly Journal of this Society, vol. Xxxvli., approximates much more closely in its general cha- racter to what is required, and were it possible to assent to his statements, this memoir might never have been written, at all events in its present form. But my interpretation of the facts observable differs so widely from his, and the resulting order of succession, both vertically and horizontally, requires so radical a change, that the only feasible plan is to begin the description again de novo, referring only to his descriptions and those of Sir A. Ramsay when they can be accepted so completely as to require no change. The Pre-Cambrian rocks of Anglesey, supposing all that are about to be described are accepted as such, are divided, partly by upheaval, and partly by faulting, into no less than six distinct areas. Four of these are coloured as altered Cambrian on the Survey Map, and two as altered Silurian. These four may be called respectively the MONIAN SYSTEM OF ROCKS. 467 Western, Central, Eastern, and Northern districts. Of the other two, one which lies south of Traeth Dulas and near Bodafon Moun- tain is naturally in association with the Central district, and the other, which lies east of Parys Mountain and north of Llanwenllwyfo, is most connected with the Northern district. It will be found most convenient to arrange the descriptions in the order thus given. Tur Western District. Hotyuean Istanp.—This island is divided geologically into two parts by a master-fault which runs in a N.W. and 8.E. direction, and separates a newer series on the 8. W. from the older portion on the N.E. Confining our attention at present to the latter portion, we find an order of succession very clearly made out, the well-known quartzite of Holyhead Mountain being lowest in the sequence. In this there is very clear cleavage, and on the seaward slopes every yard is shivered into a thousand fragments. Along the direction of cleavage, congregating as best they may in the intervals between the larger grains of quartz, are innumerable flakes of mica, or feebly coloured chlorite, producing a foliated rock ; but there is no obvious connexion here between the foliation and bedding. ‘The actual direc- tion of any minor beds in this great mass is not easy to determine ; but standing on one of the eminences in the wild country to the S.W., and seeing scarp after scarp descend in giant steps from the summit to the sea, one fancies a bedding on a large scale with a dip to the 8.E. If these are really beds, the dip is a gentle one, whereas the cleavage is vertical. In any case it is in the direction of this dip that we must proceed to find any higher beds, and when we do find them the dip is confirmed. On the 8.E. slopes of the mountain the quartzite becomes dirty and of finer grain, and gives place, where the road is reached, to solid micaceous foliated grits. These and alternating more quartzose beds rise into the summits of the low hills in the same direction, and then somewhat suddenly change into the chloritic schists, so that a clear line can be drawn after which no quartzites appear. This is rendered more evident by the occurrence of two minor faults, somewhat parallel to the master one and to the running of the greenstone-dykes. The smaller of these, on the 8. W. side, brings the chloritic schists with their wavy lines close beside the massive quartzose rocks and emphasizes the contrast. The larger fault on the N.E, limits the mountain in that direction, and substitutes for it the low ground that terminates in Penryn Garw. This headland consists of the upper part of the quartzitic group, with its bands of micaceous grit, and is succeeded immediately by the chloritic schists, which are seen lying on its sur- face to the west of Porth-yr-ogof, thereby proving that there is no fault in that inlet, as supposed by Dr. Callaway. All things are here in regular succession, and the fault which separates them from the mountain may be clearly traced to the neighbourhood of the town. The chloritic schists of Holyhead are very remarkable rocks. They were originally laminated, as is evidenced by the parallel lines of dust 468 REV. J. F. BLAKE ON THE and fragments which are still foundinthem. The welding together of alternating ingredients in the process of crystallization has pro- duced a very tough material, and subjected as it has been to enormous pressure, it refuses to cleave ; it will not be faulted or broken, or bend bodily into massive folds; all it will do is to crumple, or, as Prof. Hughes calls it, to “‘ gnarl.” When seen, as it often is, on the surface of a rugged boss of rock, it gives the boss a damascened appearance by the fine and intricate patterns of its various lines. When it has been less compressed, as in the road-cutting near Porth- yr-ogof, we can follow the lines on their crinkly path and obtain the general direction of the dip. When the pressure has been mostly perpendicular to the laminz, the rock becomes massive and slaty, and the materials are less altered, though some foliation has taken place. ‘Thus the gnarling is a subsequent process. As we pass eastwards from Holyhead several more massive zones are encountered, containing more quartzose grains ; but with this slight variation, the remainder of the island, as exposed inland on the N.E. side of the main fault, shows only these schists belonging to a stratified series. It is to be noted, however, that our general means of observation are limited to the bosses that protrude through the fields, and these, from their very mode of occurrence, are probably the more indurated and thoroughly crystalline portions of the rock, while any softer or less altered part would be hidden beneath the soil. But the sea- shore knows no such rule, and accordingly between the railway and Gorsedd-y-Penryn on the island shore the more crystalline masses are interbedded with more slaty and purple varieties, and there is a band of browner rock containing angular fragments of quartz and felspar of comparatively large size. Before leaving Holyhead Island, we may notice a remarkable out- lier of coarse conglomerate which lies on the west side of the great quarries, and forms the foundation for some buildings. The frag- ments are so large and the deposit so local that one thinks at first of an artificial concrete ; but the matrix, on examination, is seen to be inimitable by man. The fragments are not those of the neigh- bouring rocks, but resemble the higher heds of the Pre-Cambrian to be presently described. This seems to die out suddenly, as by a fault, towards the sea; but towards the rifle-pits it tails off gradually, and contains more of the local quartzite. We can scarcely fail to re- cognize in this deposit a basal Ordovician beach-breccia, the in- terest of which lies in the proof it affords that the Pre-Cambrian rocks were worn down in this district to near their base during the continuance of the Cambrian era. Tur AREA Nortu or tHE Hotynxap Srrarrs.—At Porth-y-defaid, about four miles north of Valley, Dr. Callaway draws an important fault, running inland with an E.N.E. trend, which, he says, separates entirely a ‘“‘slaty” series on the north from a “ gneissose ” series on the south. At this point also on the coast, the legend on the Survey Map is changed, the country on the south being characterized as “ oreen and purple schists, often micaceous,” while that on the MONIAN SYSTEM OF ROCKS. 469 north is described as “ soft brown and felspathic schist with beds of quartz-rock and conglomerate.” It is obvious therefore that the most important point here to determine is whether there are really two distinct series of rocks in this area, or whether one class merges gradually into another. For this purpose I have examined microsco- pically a considerable number (24) of the rocks which are referred to the chloritic schist, and have collected some forty other examples ; but the country is so wide that even these seem hardly adequate. Nor are matters so simple as Dr. Callaway’s statement that ‘ true schists with a south-west strike occur everywhere to the south ” would lead one to suppose. In the first place a large number of the exposures show no strike at all, but the lines of division run in almost any direction, and where the strikes can apparently be determined, they are discordant from place to place. Thus, on the south of the river Alaw near Llangynghenell, it is N. 20° W., at the church E. 8° N., at Bodedern E., south of Bodedern E. 20° N., and a little further south N.30° E. It is plain, then, that the rocks have suffered so much local dis- turbance as to destroy the value of the strike and to drive us to consider surface-distribution only. The larger number of exposures inland show us fine chloritic schists, which differ considerably from those of Holyhead in being composed of much more minute particles, whether crystalline or original, and thus possessing a much more slaty aspect, though often actually foliated*. But in several places there are bands of grit of irregular development, as near Llanfihangel and near Llanddeu- sant. ‘These can hardly be said to be foliated at all. At Abersant, near Llanddeusant, the other extreme is met with in a regular mica- schist. The constituents are almost entirely mica and quartz, the former in large folia, the latter completely recrystallized, and all thoroughly orientated. This is the only place in the western district in which I have met with a rock of this description; and the cause of its appearance here, unless the granite of the central district is continuous in this direction, is not easy to see. The occurrence, however, is of some importance for the correlation with other districts. Besides the ordinary metamorphism which has produced the chlorite, we find in places proof of much change of dynamic origin, bringing about a peculiar fibrous aspect, as near Bodedern, in the valley west of Llanddeusant, and at Llanddeusant itself, where the beds are also very slaty and a large proportion of the material consists of unaltered dust. The roads between this village and Llantrisant are mended with a purplish slate, which is mixed with green in the small openings that have been made. These observations already prove that there are considerable differences in the amount of metamorphism which the rocks have undergone, and that in some cases there is scarcely any change. * To distinguish these from the coarser laminated rocks near Holyhead, I have called them chloritoid schists, not meaning thereby that they contain the mineral ‘ chloritoid.” 470 REV. J. F. BLAKE ON THE But it is to the sea-coast that we must go to see the true character of the series. Leaving the turnpike road between Valley and Holyhead, we hardly get foot on the rocks which the sea has exposed, before we receive a somewhat astonishing lesson. At first we walk on the ordinary chloritic schist, but soon this begins to have a mixed appearance, being more slaty and touched with purple ; and then in little space the same bed has changed into a regular purple slate. Sometimes the change may be traced vertically, and sometimes horizontally ; but by one way or the other, before the mouth of the Alaw is reached, the whole shore is a mass of purple slate. It ought rather perhaps to be called shale, since there is no definite cleavage, though the rock is divided by lines of pressure parallel to the bedding. In structure it consists of very fine dust, and, with the exception of fine flakes of sericite here and there, is in no way altered. Here, then, in the very midst of the chloritic schists, and forming part and parcel of them, we have a slate that is entirely comparable to the Cambrian. The colour, however, of the latter is usually a bluish purple, while this, like the rocks of the Long- _ mynd, is of a reddish purple. We must certainly excuse any author who had observed these facts for being led to consider the whole of these most ancient rocks to be only altered Cambrian. On crossing the Alaw we come again to chloritic schists which are nearly horizontal, and are associated seawards with massive grits and epidotic rocks. In these begin to be seen some scattered fragments of quartz and felspar, which are not of the same order of magnitude as the remainder of the rock, and, being quite angular, suggest a volcanic origin. The grits especially are full of these. Amongst the fragments thus contained in a rock essentially of the lower part of the series are some which may be described as quartz with many chlorite inclusions, but which are not to be confounded with chloritic schists. . Following the rocks containing these, we find, as we go north, a new type consisting apparently of the finest dust in lenticular patches, coloured brown and green, and showing no stratification beyond these lenticles. Under the microscope these are seen to consist of an excessively fine mosaic of crystalline particles with very little that is opaque, separated by segregation lines of a coarser mosaic of quartz. As the total result is a slaty rock, I propose to refer to this, which is of wide distribution, as a marbled slate. I conceive that it must be produced by the accumulation of volcanic dust. Further north at Peniel, we come to grey ashy beds dipping to the S.E., and these are followed on the north side of Porth-penryn-mawr by laminated schists, changing, as we have seen them do before, into purple slates, the boundaries of the latter in one instance being a pair of joints. We thus have a synclinal with the volcanic dust and ashy beds lying on the chloritic schists and their unaltered representatives. After a sharp anticlinal turning the beds over to the N.W., we find a disturbance and a fault, and then chloritic schists come on «gain horizontally, and are only disturbed again at Porth Delise, where there is an intrusion of epidote-rock, and a curious MONTAN SYSTEM OF ROCKS. 471 tongue of calcareous rock terminating like an intrusive rock amongst the schists. Hence to Porth-y-defaid the chloritic schists con- tinue, with only minor disturbances, and mostly with beautifully ruled horizontal lines. Near that place there is a kind of pustule of hard dolomite and quartz, with specks of copper-green, which runs across the bedding, and seems to be produced by an infiltration of the mineral which has forced the lamine asunder. Allthese phenomena, which otherwise might not have required so much detail, prove how inextricably the chloritic schists are con- nected with the types of rock, and even with their accidents, which we shall meet with further north on the other side of Porth-y-defaid. The synclinal of ashy rocks may be also traced inland by the Holland Arms Inn, Llanfachreth, and at the crossing of the Alaw by the high road from Valley, after which it seems to die away. At Porth-y-defaid there is undoubtedly a disturbance and a fault, as stated by Dr. Callaway, and after this we do not meet, for some time at least, with anything even remotely resembling the chloritic schists. At first the rock is soft and tufaceous; then harder green ashy rocks appear, and are succeeded as we pass into the bay by the typical marbled slate. By the occurrence of this rock we are able to trace the group inland, in a southern direction near Plas-y-glyn, as far as the Llanfwrog smithy. Hence this fault is apparently lost inland, and to the east there is no trace of it in the line of junction, which becomes less and less marked, following nearly the course of the northern branch of the river Alaw. Thus at Pont Scyphydd, on the eastern side, there is chloritic schist with a few sporadic chips ; on the western, at Caerdeon, the rock is unfoliated, and contains many chips, while near at hand is a knob and reef of quartz, characteristic of the upper portion of the series. These observations do away with the importance of the Porth-y-defaid fault, and show that though we can distinguish an upper more ashy portion from a lower more schistose, one passes into the other after the manner of parts of a single series, and is not separated from it, as members of two different groups would be. Tar Norta-western Arna.—On the northern side of the line just defined the whole of the rocks appear to have a partly volcanic origin, and thus to possess characteristic irregularity of development. Only at Camaweg, one mile E.S.E. of Rhydwen, have I seen any rocks resembling the foliated rocks of the south by the existence in them of continuous parallel lines. This small patch may serve to show from the other side the real continuity of the whole series. As explained before, we are only likely to meet the more indurated masses in the projecting knobs which still characterize the inland country, but are now more rare. These show a new type of rock. The rocks are dark in hue, with a sort of indigo-purple tinge, and are somewhat slaty in aspect ; but there is no lamination or bedding, the whole is a solid mass in which the only separating surfaces are of subsequent origin, which may be wanting altogether or divide the rock into concave lenticles, like thickened watch-glasses. These A72 BEY. J. F. BLAKE ON THE are doubtless due to the induration of a volcanic mud, and are nearly allied to the marbled slates, but of more earthy material and quite different appearance. They are occasionally full of angular fragments of over an inch in diameter, forming a local agglomerate, and at one place they appear to be cleaved. I call them pelite, and when in lenticles lenticular pelite. Considerable quantities of chlorite or sericite in small specks are developed in many parts, so that they are as altered as their nature permits, far more so in fact than the slaty portions of the underlying series ; but they are not constantin this respect. With the exception of certain peculiar developments to be noticed later, this is all we can see inland to the south of Llanrhyddlad. The coast is more instructive. Very little of value can be made out at Porth-y-defaid itself. It is a spot of great confusion, in which the grey schists have ended in contortions along a zigzag line, beyond which we find a broken area of marbled slate, purple slate, hard blue grit, and epidote knobs. Passing north over the coarse green ashes, we find the marbled slate at the corner undisturbed. The bay is formed of softer ashy | rocks, and the headland beyond Trefadog is of very tough material, weathering into honeycombed masses, as though by the solution of some mineral that had segregated into lumps. In this there is not the vestige of a dividing line of any sort beyond the modern cracks. More than a mile of sea-coast, studded with these tooth-like pro- jections, and cliffs continuous with them, in which no stratification can be seen, and which are yet not crystalline, serves more than any place in Anglesey to impress upon the geologist the volcanic origin of these tufts. In the scarped sides of such a modern volcano as that of Ischia, similar phenomena may be admirably seen, but in no other circumstances can they even be imagined. In the southern part of Church Bay, and also in the northern, the tuffs are very soft and earthy, and quite modern in appearance, though here and there compressed into a banded rock; but in the centre from Porth Crug- mor to Porth Sutan are the lenticular pelites, passing into the marbled slates. In these variations we see the essentially local character of the several deposits. We might of course imagine that they lay in bands which we could trace inland; but this is not the case ; whichever way the bands may be supposed to run, we fina the supposition contradicted by the occurrence of the pelite. The softer parts, at least, are in isolated patches, which the sea has nearly consumed. Not only in their character, but also in their distribution, these deposits are of a volcanic nature, and the dif- ferent masses are dependent not so much on time as the localization of successive outbursts. In one direction may be carried the finer dust, producing the marbled slates; in another the coarser, more basic mud, producing the pelites; in a third the still coarser, pro- ducing the grits; and in a fourth the ejection of large fragments may produce the agglomerates. The country north of Llanrhyddlad is of much higher elevation ; the accumulation has probably been thicker; we are nearer the centre of eruption, and the ground is cut up by pairs of trough- MONIAN SYSTEM OF ROCKS. 473 faults, letting in vertical wedges of black Ordovician shales. The most abundant rock here is the marbled slate, though pelites are found at the base, and form the mass of the isolated hill, the highest in these parts, and visible from all parts of the island, called the Garn. This is capped by a massive breccia, which at first I took to be an agglomerate of the series; but I am now convinced it is Ordovician, from the character of the rocks of which it is composed, and which seem to pass up on the eastern side of the hill through grits and finer breccias into ordinary shales. We now pass to the extreme north-west beyond the trough-fault introducing the Ordovician at Yuys-y-fyddlyn. This area is much cut up, and there are signs of our being near the centre of eruption in the general coarseness of the pelites, which become recognizable ashes, in the occurrence of large masses of agglomerate, and in the intrusions of the granite and other rocks. Of this granite, which is said by Sir A. Ramsay to ramify in all directions, Dr. Callaway says it is a granitoid band of the gneiss, and he asserts that the greenish felspathic beds when followed across the strike to the north are seen gradually to change and ultimately to pass into thoroughly foliated gneiss and granitoidite. To this I cannot assent. After a careful search I can only find one band of granite in Pen-bryn-yr-Eglwys itself, and this runs from the summit of the hill towards the “ sea- mark,” that is, across any supposed strike of the rocks, which, however, are not sufficiently bedded to have any strike at all. This is associated on its eastern side with a hornblendic rock, which rises into the southern summit and is somewhat foliated. Much of the material surrounding these consists of brecciated rocks of similar material, much impregnated with mica or chlorite, which, being arranged in more or less parallelism, may be said to produce a mica- schist, but itis one of quite a different character from the true foliated rocks. I think there can be little question that these rocks are derived from the breaking up of coarsely crystalline igneous rocks, and are not a stage of metamorphism towards granite. Moreover there is really no passage. It may be difficult in some places to draw the exact line of junction, owing to the fracturing of the granite itself and the subsequent metamorphism ; but elsewhere in the same mass we can find a vein of clean granite, bounded on both sides with chloritic — breccia of a similar rock, and elsewhere a clear line of junction can be traced in the field. The granite is a fairly clean crystalline rock of large elements, and with comparatively little mica; but in places it changes into a greenish felsite very like that of St. David’s, but with very few scattered crystals, and these not of quartz. Although the clean granite is limited to the line described, the whole material of the hill is composed of the breccia, which becomes more micaceous or chloritic as it nears the granite, and gets finer and finer towards the south. A little further in this direction, near Pant-yr-Eglwys, is another intrusive mass running at right angles to the first, asso- ciated with large agglomerates and ashes, shading off into the finest unaltered dust. This mass is not granite, but a true quartz-felsite with large eroded quartz- and other crystals, and with a granophyric ground-mass, and at its margin it becomes pseudoperlitic. ATA BEV, J. F. BLAKE ON THE A third mass of granite occurs towards the east, behind the farm called Monachty. Here also the surrounding rock, away from the immediate contact, is an ashy pelite, and the line of junction is clean ;. but in the boss of rock exposed to the east of the farm the granite may be seen passing in strings into the pelite. It is sometimes granophyric in structure, and the quartzes have been very much squeezed. There is occasionally a difficulty in drawing the line between the two rocks, owing to the granite having been brecciated im situ and the cracks filled with mica, while the pelite itself develops mica in the neighbourhood of the granite. These observations leave no doubt on my mind thatthe granite is an intrusive rock, of the same general age as the ashes into which it intrudes, related as the dykes of Etna might be to the mass of the mountain. And the so-called schists are alteration-products of the ashes, due practically to contact-metamorphism acting on material of a less sorted kind than usual. Later observations will be found to confirm this and yield even more decisive proofs of in- trusion ; yet the rock, the origin of which is thus determined by field- observations, is of the same character, presents the same differences. from ordinary more recent granites, and has the same felsitic asso- ciates as at St. David’s or Caernarvon, where the stratigraphy leaves it open to geologists to account for these differences by considering” it an altered sedimentary rock under the name of “ granitoidite.” There is no very determinate order of sequence in these rocks, and some of these central masses may be older than the circum- ferential; but when the volcanic débris 7s mixed with the chloritic schists, it is with their uppermost part, and even in this corner the most slaty portions, which may be considered in part sedimentary, occupy the lower positions. We may therefore conclude that the volcanic group forms the higher portion of the series, and the granite is therefore one of the youngest rocks in the district. With regard to the relations of the series to the Ordovician, they are not always brought together by faults. There is reason to: believe, as already stated, that the capping of the Garn is really a beach-breccia; but more decided and ordinary Ordovician con- glomerates are found on the slopes of Pen-bryn-yr-Eglwys. These are met with on the road from Monachty, where it turns north to go to Porth Geon. They are of various kinds. One portion, which lies upon an old agglomerate, is made up of its pebbles rounded, and approximates to it in appearance*. Another portion is of large quartz-pebbles with ferruginous matrix, the size gradually decreasing till they are the size of peas, or less; and another is a compacted,. perhaps less weathered, hard, bluish rock, not at all unlike that at Twt Hill. These may be traced on the ground over a limited area, bounded on two sides by faults, and passing up into brown grits, — and then into hard blue slate. I have not found fossils in these rocks, but their general resemblance to the basal Ordovician in the rest of * Very much as is the case with the agglomerates and conglomerates om Clegyr by Llyn Padarn. MONIAN SYSTEM OF ROCKS. . “ATS the island, and the absence of Cambrian rocks in the trough-faults close at hand, points to their being of Ordovician age, and they thus supply a proof of the absence of true Cambrian deposits in this area. I expect it must be continuations of these that occur in the skerries, which I have not been able to visit, but which are marked on the Survey Map as “ hard conglomerates and grits.” In the portions of the Western District now described there are three classes of rock, which from their wide distribution in the island, and their special and characteristic nature, I have reserved for particular description. They all occur isolated, and are due to actions which are limited to a small area. These are :— 1. Epidote Infusions.—Certain parts, both of the chloritic schists andof the higher rocks, are found to be more indurated, and to weather into round outstanding knobs, or portions of beds. They differ from the surrounding mass by being dark green in colour and finely crystalline in fracture, but without orientation of the crystals. These, on examination, turn out to be full of minute crystals of epidote scattered uniformly through the rock. I can think of no better explanation of them than that the rock has been locally saturated with some mineral water, the reaction of which on the surrounding material has produced the epidote crystals, and hence I call them “ epidote infusions.” They are seen at Porth Delise, north of the river Alaw, north of Porth-y-defaid, at Porth-y-corwegl, at Borth Wen, Roscolyn, and elsewhere. 2. Quartz Knobs.—These are the most remarkable features of all the Anglesey rocks, and their origin is a matter of great difficulty. In their characteristic form they stand up.as isolated hummocks on the surface of the country, and are often nearly as high as they are long or broad. They may be merely low mounds, or may rise as high as a house, or form a good-sized hill. Usually they are elliptical in outline, but may be narrow and long, though it is doubtful whether we should refer the latter to the same category, ' or consider them as ordinary veins. In structure they may possess scarcely any clastic elements, or they may contain many very rounded pebbles of pure quartz, the whole or the remainder being composed of clear quartz in dusty-looking polygons of growth separated by clear lines, the dusty appearance being due to exces- sively fine cavities, the largest of which may possess fluid-enclosures. The only impurity is a little occasional sericite which may form round the larger pebbles where the matrix is not quite close. The purity and structure of the rock, together with its mode of occur- rence, forces me to the conclusion that it has been formed on the spot where it is now found, though the pebbles may have been brought there along with the formative material. They are not veins in form or in structure, but they may have had a similar origin. The only suggestion I can offer is that they are the result’ of the cooling of hot water which has bubbled up and eaten away the rock into a cavity, then deposited quartz on the sides, in some cases has broken up again the first deposits, and rounded the A476 REV. J. F. BLAKE ON THE fragments into pebbles, and has finally filled up the cavity by the deposition of its quartz. In other words, they are the bases of Pre- Cambrian geysers, which may, or may not, have succeeded in reaching the surface and erupting. In the western district these are seen at Yr-ogo-r-arian and south of Porth-yr-hwch in the area round Pen-bryn-yr-Eglwys, on the east side of the road near Llanfaethlu, and near the river by Clwch-hir, north of Lland- deusant; but much more characteristic and important examples are found in other districts. They are always associated with the rocks which we have other reasons for concluding are of volcanic origin ; and this is one reason for looking to the phenomena of such regions for their cause. 3. Sporadic Limestones.—These are elongated bands of crystalline limestone filling lenticular spaces in the pelites; as they are quite isolated and irregular and have no constant strike, we cannot con- sider them as beds which are now placed on end, but must look on them as products of infiltration or segregation. They are composed of a mosaic of small crystals, in which there may be larger crystals with abundant rhombohedral cleavage. In other districts and higher in the series we meet with limestones of more bedded character, but these may have been produced on the surface by the same waters which caused the present ones below. These sporadic limestones are seen at Llanfaethlu, where nests of umber occur in the rock; also at the telegraph-station near the same place, and on the hill-slopes to the west of Ogo Lowry. They must not be confounded with the calcitic bands in the older rocks, nor with the remarkable inburst at Porth Delise already described. Tue Souru-Srack Serres.—On the south-western side of the main fault that divides Holyhead Island into two parts, the rocks are of a different character from any we have yet seen, and ought to be more sharply marked off from the Holyhead group than they have hitherto been. I therefore designate them the South-Stack Series, as they are well seen at the South-Stack Lighthouse. In certain parts, no doubt, as at the lighthouse itself, their splendid contortions and their rugged aspect defying the stormy sea, give them an appearance of great antiquity, and it is on this account that Sir A. Ramsay con- siders the fault to have a downthrow on the N.E., by which the rocks of Holyhead mountain are made the younger. Much colour is lent to this view by the fact that throughout the long succession which we can elsewhere trace in the island, nothing like them is to be found. Nevertheless, the entire absence of metamorphism in con- siderable parts, and their resemblance to the bedded rocks of Bray, and even to some portions of the Cambrian of Wales (a resemblance which would have no weight with Sir A. Ramsay, who considered all to be Cambrian), inclined me.from the very first to the opposite ‘view, and I believe I can now prove that they are younger. The argument from the degree of metamorphism amounts to very little. We have already seen that on the north-eastern side of the fault the chloritic schists, which are thoroughly foliated, are one MONIAN SYSTEM OF ROCKS. 477 with the purple slates which are not foliated at all; and on the south-western side there are parts which are both cleaved and foliated, and others which are neither. The disturbance and con- tortion are much greater on this side, because the rocks have yielded to the pressure. They are also cleaved in parts, because they are of suitable material. The accidents to which both parts have been subjected since their formation have affected them in different ways and in a different order; but this throws no light on their relative age, which must be determined, if possible, by stratigraphy ; and if not, by correlation with deposits whose order is known. The South-Stack Series is divided by the erosion of the sea into two distinct parts, the one from Gogarth below the Holyhead moun- tain to Porth-y-corwgl, the other near Roscolyn from Bwa-du to Borth Wen. ‘The two halves do not correspond, and it is not clear whether they are alternative or consecutive. In the Roscolyn mass we find their junction with the chloritic schists. The bounding fault comes out in the centre of Borth Wen, and an epidote-infusion marks the boundary of the chloritic schists towards the north-east. On the other side a mass of grit is brought against these schists in a low cliff in the hollow of the bay. When, now, the series is traced eastwards into the promontory, this grit is seen to lie upon a more micaceous variety, and this passes down, on the small peninsula, into a rock, which can be distinguished neither macroscopically nor microscopically from the typical chloritic schist of Holyhead. So unprepared was I for this passage, that I labelled the rock when first found ‘‘ pseudochloritic,” and paid a second visit to the spot to find, if possible, some fault which had been over- looked. No fault, however, occurs, and it 1s certain that the South- Stack Series succeeds conformably, and must therefore be the non- yoleanic equivalent of the pelites of the north. This Roscolyn area must contain the lower beds of the series, whatever the other area may be. In it we meet for the first time the phenomenon of cleavage in these rocks. As soon as we leave the chloritic schists this cleavage sets in, and along the planes of it abun- dant chlorite or mica is developod, so that the rock is also foliated, and on the surface of the ground the bedding is entirely masked. Under the weathering of the sea all looks alike, with vertical lines of subdivision, and stratigraphy has to be abandoned as hopeless, But in a deep cleft of the cliff, marked by a fault on the Survey Map, sudden light is afforded, and we learn that in spite of the cleavage and foliation we are dealing with well-bedded rocks, each with its distinct character and dipping in a northerly direction, 7. ¢. partly towards the fault and partly in the direction that will bring in higher beds as we proceed north-westward (see fig. 1). It is the lower beds of this section that we have been passing over since leaying the chloritic schists of Borth Wen and the higher beds that rise into the summit of Mynydd Roscolyn. Thence they have already come down to the level of the top of the cliff, and shortly they occupy the whole of it. Special attention may be drawn to A778 REY, J. F. BLAKE ON THE SEES Slope of beach. certain beds in which there are zigzag lines of quartz dying out on either side and lying obliquely to the bedding. These are referred to by Sir A. Ramsay as “foliated interlaminations of quartz and quartzose schist”; and Dr. Callaway appears to quote this when he says “there is evidence from the folding of quartz-veins that — the rock has been squeezed to the fourth of its original bulk.” Ido not know that we have any evidence that these were ever any straighter than they are. I interpret them as cracks produced by the irregular oscillation of the overlying quartzite on the more yielding rocks below, and a subsequent infilling by silica. As seen in the promontory of Maen-yr-esgyll, the quartzite must be 80 feet in thickness; it here has a N.W. dip of 45°, and is cleaved in the same direction at 60°. I give these details to show that we are now dealing with rocks in which such points can be determined. 80 feet more of mixed beds lie above it before we come to a second white quartzite. The series is repeated again on the other side of the fault which runs out at Borth Saint, and the upper quartzite is succeeded by grey and yellow cleaved sandstones, and so the series comes to an end against the main fault at Bwa-du. These quartzites, of which the upper may reach to more than 100 feet, are thus proved, stratigraphically, to have no connexion with that of Holyhead, but to be developments higher in the series. The undu- lations of these upper rocks and the development of the quartz- cracks in the beds below the quartzite are well seen in Borth Saint (see fig. 2). It is on the base of this quartzite that Dr. Callaway thinks ripple-marks are to beseen. [I interpret the ridges seen, both here and elsewhere, where a massive bed overlies a softer one, to the squeezing-out produced by the cleavage-pressure, festooning the harder in the more plastic mass. The other area, which includes the South-Stack island itself, has been well described by Sir A. Ramsay, though there are some im- portant points still to notice. As in the Roscolyn area, the cleavage is for the most part so intense that it is difficult to make out any succession inland on the broad rolling area by the side of Holy- head mountain. West of the lighthouse there seem to be two deve- lopments of quartz, some of which are worked for china-stone ; but MONIAN SYSTEM OF ROCKS. 479 Fig. 2.—View in Borth Saint, Roscolyn. 9 Nh J Lia 1. Upper quartzite. 2. Quartz-vein bed. 3. Red Beds. 4. Lower purplish beds. 5. Broken red slates &c. The nearly vertical lines are lines of cleavage. these seem to be very local; and though under the action of the weather all the surface looks quartzitic, there is no quartzite proper to be seen in either section or cliff. There is no other bed in the Roscolyn series sufficiently characteristic for correlation, so we are left in doubt whether all these northern beds are newer, or changed in the new area from their old form. On the whole, I regard the series as ascending from the South-Stack end, thus forming a great synclinal, of which the trough is occupied by the sea and the two ends are exposed. On this supposition we may see the succession of the lowest beds in a deep gorge in the cliff at Gogarth. Here the beds lie in a great fold, rising on the whole to the S.E., though there is very clear cleavage tothe N.W. The beds are alternately soft and hard, the softer being a massive felspathic rock, more like volcanic dust than any yet seen, and several of the harder ones showing the festoon- ings of the lower side from pressure. The changing character of the rocks can best be seen by looking at the cliff from the light- house island, where more than 80 beds, of thicknesses varying from 8 inches to 3 feet, can be counted. The undulations are here so strong that the actual dip may be doubted; but its average can be obtained by following a single bed in its passage along the cliff (see fig. 3). So far the average dip is to the S.E.. The magnificent bird-gorge, where the gulls, the kittiwakes, the razorbills, and the cormorants assemble in thousands, is occupied by a synclinal, and beyond this the shore is inaccessible; but in the deep gorges of the cliff the crests of the anticlinals of contortions point S.E., which indicates an average dip to the same point of the compass. In the nameless bay which now succeeds, the rocks are still beautifully Q.3.G.8. No. 175. ou ‘480 REY. J. F. BLAKE ON THE contorted, but they are neither altered nor cleaved. The thin bands of hard shale, with their cappings of indurated rock, often tinged with iron, remind one of the Lias—the rocks are somewhat harder, and I could find no fossils, but there is little further difference. The direction of the crests is here somewhat reversed. Fig. 3.— Running of one Bed at South Stack. N.W. 8.E. Sea-level. Passing to the next headland, the first rocks seen are sericitic slates, and these are worked inland in close proximity to the chlo- ritic schists, to which they form a striking contrast; then succeeds a series in which cleavage and foliation have gone so far as to obliterate the bedding, except as seen from a distance. We can trace, however, the same general §.E. dip as before, varied by spaces where the contortions run more nearly horizontally. The rocks remain thoroughly bedded, when actually seen; but, as at Roscolyn, the weathering of the cleaved masses gives a uniform appearance to the whole, and there is no true quartzite. Towards Porth-y-corwgl the cleavage becomes less marked; and inland, near Porth-na-march, it is entirely absent, and unaltered grit is found in well-marked folds *. These bedded rocks have, of course, a definite thickness, but it would not be worth the labour to determine it accurately. I should estimate it (allowing for the horizontal portions) at not more than from 2000 to 3000 feet in all. Sir A. Ramsay states matters quite differently from all the above description. He says that for three miles south of the Stack there is a high dip to the N.W., whereas I say it is to the 8.E. and variable. His estimate would give from 13,000 to 14,000 feet to the rocks. It would seem rash to accuse Sir A. Ramsay of having mistaken cleavage for bedding here; but he makes no mention of cleavage in the area, though it is certainly intense; and there are several spots where the dip inserted on the map exactly describes the direction and amount of the cleavage. Perhaps the clearest of these is at a promontory east of Porth Rhyffydd (see fig. 4). In any case I am pretty certain of my own observations as above, and cannot allow an extraordinary thickness to the series. * The greenstone dyke at Porth-y-corwgl, which runs near the fault, is beautifully jointed both in the columnar and the spheroidal style, like the pillars at the Giant’s Causeway —- <2 aie eee MONIAN SYSTEM OF ROCKS. 481 Fig. 4.—Promontory east of Porth Rhyffydd, showing Cleavage and Contortion. 8.8.5. N.N.W. Tue Mass or “ Serpentine.”—Much is already known about this from the researches of Prof. Bonney, published in vol. xxxvii. of the Journal of the Society, and it does not concern the present memoir to discuss its general points of interest. The name applied to the rocks which are coloured as “Serpentine” on the Survey Map must be taken in a very general sense as equivalent to “‘ some- thing peculiar, related in some way to the presence of serpentine,” and even then the mapping is not quite correct*. From the mode of occurrence of the rock, and from the teaching of the junction mentioned by Prof. Bonney, it is certain we are here dealing with intrusive masses. The actual masses of igneous rock are more sporadic and isolated than marked on the map. In particular the gabbro is confined to upstanding bosses, which have the aspect of necks, and much of it is foliated on the large scale, though the diallage crystals are sufficiently irregularly distributed in its sub- stance. These bosses are found at Ty newydd, Morfa-coeg near Cruglas, Melin Carnau, Dinas Fawr in two places, and at Ceryg- moelion. To the north this rock is drawn out into schist by dynamic agencies, and is not easily recognizable. The lower eminences are almost entirely serpentine, and this seems almost always to be inter- polated between the gabbro and the schist. There are limestones also at Cruglas, behind Ceryg-moelion, and in the inlet west of Dinas Fawr ; and these, when they occur, are always between the serpen- tine and the schist. The largest mass of true serpentine stretches southward from round the above-named inlet as far as the Roscolyn road. It would be rather remarkable if the serpentine and the gabbro were entirely independent, but they may only be related as outbursts from a common focus. In only one place is the serpentine of crystalline aspect, as in the Lizard, and in this the positions of the original olivine crystals are easily discerned. The remainder is * There are, however, some green-coloured boundaries marked within the serpentine, which show that more than one kind of rock was recognized, 2x2 482 . REV, J. F, BLAKE ON THE nearly pure fibrous serpentine with isolated spots of black dust. The water necessary for its production must have carried away with it the superfluous magnesia; and this we find impregnating the schists all round, in most places partially, but at the southern end so thoroughly as to produce soapstone. The limestones have every appearance of belonging to the original series and of not being connected with subsequent infiltrations from Carboniferous Lime- stone, which we have no reason to believe ever lay directly above them. We have seen limestone in the older part of the series at Porth Delise; other occurrences will be noticed in the central dis- trict, and in the higher portions sporadic limestones of similar mode of occurrence are common, in association with volcanic pro- ducts, so we may expect them at this spot. The action of magnesian waters on them was a subsequent process, and they yielded to them some of their own materials ; for on the one hand we find the lime- stones impregnated, especially in the cracks, with serpentine, and on the other the serpentine in their neighbourhood is highly charged with dolomite (?). Tse GRANITE NEAR Liyn Trerwit.—tThis is the spot on which Dr. Callaway chiefly relies for proof that there are two Pre-Cambrian series in Anglesey, the one unconformable to the other. He states that here, “within a quarter of an acre,” there are “ outcrops of three rock-systems—Gneissic, Pebidian, and Palzozoic, with proof of succession in the order here given.” My interpretation of the district is entirely different, and much more nearly coincides with that of the Survey ; though I cannot quite agree with the words of Sir A. Ramsay, who simply says “there is a small patch of granite, around which the rocks are much altered, being interlaced by numerous granite veins.” The spot is a very interesting one, and, prima facie, appears to countenance Dr. Callaway’s description. But the notion of three systems occurring in this way within a quarter of an acre is so incongruous that one is bound to inquire more closely, and then it is soon seen that appearances are delusive. I present a plan of the place (fig. 5), which, if not quite correct, is certainly more so than Dr. Callaway’s. The rocks stand out of a grassy surface in long irregular hummocks. On the west side are continuous exposures of the ordinary, not very highly altered, ehloritic schists. The next boss on the east is a tolerably high one, composed of diabase. This is marked greenstone on the Survey Map. It is somewhat foliated here and there, but its character is perfectly distinct under the microscope. To the east of this, and separated from it, is a narrow ridge, of which the central part is granite, and the western and part of the eastern side, at least, is diabase. Dr. Callaway says there are greenish grits on the eastern side; there may be, but I did not observe them. The granite is of the same type as that seen at Pen-bryn-yr-Eglwys, but is broken up in places, and tinged with infusions of chlorite. A larger ridge appears on the S.E. side; on the western side of. which there is a continuation of the diabase, and on the eastern side MONIAN SYSTEM. OF ROCKS, 483 Fig. 5.— Plan of Ground west of Llyn Trefwll. 1. Chloritic schist. 2. Diabase. 3. Granite. 4. Beach-breccia. 5. Conglomerate. 6. Lake. it is a beach-breccia of large gneissic fragments. Close upon the junction at one spot, over an area not more than 3 feet long by 8 inches wide, the diabase becomes very slaty, and contains frag- ments of granite ; but its true character is seen, under the microscope, to be retained. Near here, also, and enclosed in the diabase, is a small mass of diorite, with granite bands in it. To the east, again, are two smaller ridges of coarse granite-conglomerate passing into grit, and still further east, by the lake side, two tall bosses of finer conglomerate. This is all that is seen. Thus some of the slates of Dr. Callaway are diabase; and, if there is any slate at all, it is in the beach-breccia, which may very well contain such material, en- closing, it might be, even pebbles of granite*. Thus there is no part of the later series here at all, except in the form of fragments, * T have little doubt that it was really part of this series tha yieldea the rocks examined by Prof. Bonney (Quart. Journ. Geol. Soc. vol. xl. p. 584). 484 REV, J. F. BLAKE ON THE unless we assign, as is most natural, the granite to this epoch. The granite is anterior to the conglomerate, and the diabase is posterior to the granite, and, possibly, also to the conglomerate. This last rock is the most interesting in the locality, since it is composed of fragments not represented elsewhere in the district. This Ordo- vician breccia contains many kinds of rocks, some almost approach- ing red sandstone, and others like an unaltered portion of the chloritic-schist group. The difficulty of assigning an early origin to all these seems to have led the surveyors to suggest a Carbo- niferous age for the conglomerate. However, to the east it passes into typical Ordovician shales, and most of the materials could probably be found in an extension of the South-Stack series. At the northern end, by the lake, however, the fragments are of gneiss and granite, and of other rocks such as we shall find within the granitic area in the central district. We thus learn that a similar group of rocks must have occurred here also, not far removed from sight. In other words, the synclinal which separates the two dis- tricts affects the lower rocks also, which are continuous across it at some depth. Summary of the Western District. The rocks in this district commence at their base with a vast development of quartzite, which more or less gradually changes, through micaceous and gritty rocks, into laminated chloritic schists, which are so sporadically metamorphosed as to remain in certain places as purple slates. These, with occasional bands of grit and isolated areas of sericitic schists, occupy a wide country to the east. Into this is intruded a large mass of gabbro and serpentine, and patches of limestone and of epidosite are occasionally found. The upward continuation of the rocks on the north is different from that on the south. In the former they pass continuously but rather rapidly into a vast accumulation of unstratified tuff and ashes, which increase in bulk as we go north, and ultimately come to a climax by the development of agglomerates and the intrusion of granite and felsite. In this volcanic material are found narrow lenticular bands of limestone, with mosaic crystallization, and also rounded upstanding knobs of quartz, which it is suggested are the bases or pipes of ancient geysers. The metamorphism of the rocks is very variable, in some much chlorite being developed. The coarser material is often compressed into lenticles, forming a lenti- cular pelite. The finer makes a mottled rock or marbled slate. In the southern direction the volcanic material is absent, but the chloritie schists pass up intoa series of well-bedded rocks, including two thick bands of quartzite. In some parts these rocks are in- tensely cleaved, with foliation along the cleavage-planes ; in others there is neither cleavage nor foliation, but in all there are vast undulations and contortions, forming a synclinal on the whole. They may be called the South-Stack series. At the extreme east of the district a small mass of granite is found, overlain by the Ordo- vician breccia, and not connected with the chloritic schists; it is MONIAN SYSTEM OF ROCKS. 485 probably intermediate in age between these two. The Ordovician basement-beds are found also at Holyhead, where they lie on the quartzite, at Garn, where they lie on the pelite, and at Pen-bryn- yr-Eglwys, where they lie on agglomerate. Nowhere is there found any rock like the Cambrians of Bangor. The whole series is thus proved to be a continuous Pre-Ordovician one, with two different developments in an upward direction. Tuer Centrat District. This district is the largest and most difficult to understand. In it Dr. Callaway thinks he finds representatives of all the subdivisions of his gneissic series. My principal difficulty is with the rocks which he calls ‘“ Hiilleflinta”; on these I have twice changed opi- nions, now reverting to that which the field-work suggested. It may be wrong, but, if so, the stratigraphy is almost infinitely complicated. According to this we must take particular notice of a line which is marked on the Survey map, and which runs from Porth-y-ly-wod on the coast nearly straight to the eastern mass of granite at Gualchmai, and thence to Bodwrog church. This is a line of fault. Its further course is doubtful, since in any case there must be a second disturbance beyond the railway. This line divides the district into an eastern and a western region. Tur Eastern Reaton.—The basal rock in this region, occurring next to the fault, is what Dr. Callaway calls quartz-schist, and it is succeeded by a type of rock which we have not seen before, to which he gives the very descriptive name of the grey gneiss, inasmuch as it contains felspar as well as mica and quartz. I can see no necessity for distinguishing a quartz-schist, since there is felspar, though less abundant, in the most westerly samples. The rock is, for the most part, more thoroughly metamorphosed than any in the western district, so that it is difficult to distinguish any lines of original dust. The foliation, however, is very fine and well marked, not only by the chlorite but by the long axes of the other minerals. Dr. Callaway has given a good description of the development of these rocks from Porth Nobla to Aberffraw, which need not be repeated at length ; suffice it to say, that more quartzose bands and more chloritic bands come on irregularly, the latter especially on the eastern side of Llangwfen Bay; but everywhere the beautiful foliation is well marked, and nowhere better than when the series is about to close on its meeting a fault close to the western promontory of Aberffraw Bay. For some distance here the lines are horizontal, but on ap- proaching the fault they become wonderfully contorted. The rock is easily traced inland, as in the railway-cutting and to the north of it, and soon either side of the stream at Gualchmai up to the granite, and beside Bodwrog church and the old Holyhead road. The limestones, which have been noticed at Trecastle and Bodwrog, and which are truly foliated with the rest of the gneiss, are impor- tant evidence of the unity of the series. Like those around the 486 REY. J. F, BLAKE ON THE serpentine of Valley, they are in the older portion, but they have the same sporadic character as those in the younger. In the correlation of this group with the western district I quite agree with Dr. Callaway. Though the metamorphism is more com- plete, and the ingredients more minute, they are of the same cha- racter as the chloritic schists. Their more quartzose base and their more chloritic termination show that they must be conceived to cor- respond generally to the whole of the lower group, and no marked line can be drawn between grey gneiss and chloritic schist. In all the district northwards from within a mile of Gualchmai, the eastern boundary of the gneiss and associated rocks is formed by basal Ordovician conglomerates and grits, which, at the crossing of the old Holyhead road, form a beautiful white rock, and these are soon followed by the ordinary black shales standing at a high angle. Still, therefore, no Cambrian rocks intervene, but the older rocks were denuded to their base in Cambrian times. ‘These Ordo- vician shales are bounded on the east by a well-marked fault, bring- ing in again the Pre-Cambrian series. We cannot suppose that this important fault dies out exactly where it cuts off the Ordovician and > brings the two portions of the Pre-Cambrian series together, as it has hitherto been inferentially represented as doing; yet there is this strange circumstance about it, that it represents a downthrow on the east as against the gneiss, and an upthrow as against the Ordo- vician. ‘There are only three ways of accounting for this: either (1) the grey gneiss is really the younger rock (an untenable suppo- sition), or (2) the fault coincides with the bedding-planes, which it does not, or (3) there was a Pre-Ordovician as well as a Post- Ordovician fault along the line, with opposite throws, which shows that the fault must be a well-marked one, but the balance of displace- ment need not be great. The continuation of the fault to the south can be traced on the Holyhead road between the a milestone and the slopes of the hill by Glan-gors-du Fawr. ‘Two miles to the south it passes between Tyn-y-gong and Cwlrwm, and is next seen in the railway-cutting near Bodgedwydd. A wall is built over it on the south side, all the rest of the cutting being rock. But on the north side solid green rock on the east comes suddenly to an end on a nearly vertical line, next to which is a foot or two of broken rubbish, and then we find thin-bedded micaceous rocks of the grey- gneiss series, which continue for the rest of the cutting. I give these details because Dr. Callaway says there is here a passage from the grey gneiss into the “dark schist,’ and the fault runs much further east, where it cannot be traced. Thence the fault passes west of the road to Aberffraw, near the church and west of the small promontory of Trwyn-du, where the rocks on the two sides are in strong contrast. We are thus prevented from following the sequence upwards, and must start afresh with the rocks on the east side of the fault. It is not easy to make certain of their stratigraphy. Dr. Callaway divides them into two independent halves by a fault which passes from the Aberffraw sands into the eastern boundary of the Ordovician MONIAN SYSTEM OF ROCKS. 487 belt. This must be wrong in the north. The only possible line of division that is not immediately contradicted on the ground would run along the western branch of the river Gwna, and thence across the old Holyhead road along the N.E. branch of the river Cefni. On one side of this line most of the dips recorded are towards the east, on the other side they are mostly to the west. Since the rocks on the two sides are not the same, if any reliance is to be placed on the dips, we have the choice between an overturn to the east and a faulted synclinal. Dr. Callaway chooses the latter. The former commends itself to me—first, because no sudden change of rock, except where the grey gneiss comes on, indicates any fault; and, secondly, because, unless there is an inversion, the order of the upper part in this district would be different from that which obtains in the others. Moreover, of the many bosses of rock exposed, only a few show any recognizable dip, and hence it is not certain how far those that are observed are reliable. I take, then, the rocks on the east of the fault to show a pretty continuous upward succession. We have seen that the throw of the fault may not be great, and the lowest rocks exposed may not be far above the grey gneiss, and they are so chloritic that they do not differ much from the lower schists to which Dr. Callaway refers them. The rock at Careg-engan-fawr, which he refers to the slaty series, is quite of the same type. Some part of these may be best placed as chloritic schist ; but the point of the whole matter is that they so gradually change upwards by the intreduction of scattered angular fragments that no dividing line canbedrawn. ‘Thus, though the material of the railway-cutting is very chloritic, so is the material by the Mona Inn. A green grit in the cutting is just like one at Nant-yr-lowddy, on the east of the Ordovician of the north. There are breccias on the shore close to Aberffraw, and finer breccias on the east of Llyn Coron. As a whole the rocks are more allied to the lenticular pelites than to the chloritic schists. Passing to the east they become rapidly more ashy and irregular, especially about Llangadwaladr and to the south, while to the north slates become more abundant, and great agglomerates set in on either side of the Llangefni railway. The whole set become more and more irregular, as though produced by volcanic agencies, and in so far agree with the north-west. But the materials are coarser and more mixed with stratified deposits. As I look upon the beds as inverted, I place the grits and porcellanites of Ceryg ddwyffordd, near Llangefni, at the top of the series. After the admirable description of this portion by Dr. Callaway, under the head of the “ Llangefni synclinal,” I need not enter into any further details on the general development, but only call attention to points of special interest. Amongst them are:—1. The great agglomerates, so well seen in the railway north of Llangefni, and on the coast on the south. These contain huge masses of quartzose and igneous rocks, in the wildest confusion: we cannot call them conglomerates and look to more ancient land for their source ; they are not disposed after the manner “such rocks, but they contain ejected blocks from a volcano, con- 488 REV. J. F. BLAKE ON THE sisting for the most part of rocks only recently formed and belonging to the same series. As these occur towards the east, and beyond them in that direction we have nothing that could so break up, whereas we can find similar rock to the west, we are led to the conclusion that these agglomerates, which actually stand vertically, are the higher portions of the series. 2. The quartz-knobs. These have thesame: form and character as in the western district, but some at least are much fuller of rounded pieces; still they are nearly pure quartz, with polygonal network and sericite in the intervals, but no folia- tion. Perhaps any one seeing one of these in this district for the first time would consider it a grit, but the above characters are not those of a grit. In the case of the mass at the Llangefni Mill, marked “ greenstone” on the Survey Map, it is so large, and shows such apparent traces of bedding, and here and there in its substance small flakes of foreign material, that we may conceive that this at least was an external deposit whose last origin at least was sedi- mentary ; but the others at Bethel, near Bodorgan, at Twll-y-mwg, one mile north of Bethel, and on the railway south of Llangefni, are typical isolated mounds of pure material. It will be noticed that — all these four masses are nearly on a line coinciding with the strike. Other very quartzose knobs occur north of Cerrig Ceinwen, but they do not perhaps belong to this type of formation. 3. The sporadic limestones. The lowest of these, near the Druid Inn, on the Holy- head road, though similar to that at Bodwrog in appearance, is quite distinct in structure, and corresponds to the type found among the ashy series. It is a white massive rock, occupying a lenticle transverse to the general bedding, and most resembles in nature and occurrence the mass at Llanfaethlu. On either side of Cerrig Ceinwen there are also masses of limestone, but these at the present time are of different character. Though very local in development, they are bedded while they last ; they are associated with reddish strata and with breccias of their own substance mixed with similar material (see fig. 6) and producing umber in nests. Amongst these reddish Fig. 6.— Quarry 1; mile south of Cerrig Cenwen. 1. Crystalline limestone. 2. Reddish slates. | 3. Nests of umber. slates are some that are marked all over with nearly parallel, branching, calcareous, crystalline, cylindrical tubes, suggesting such MONIAN SYSTEM .OF ROCKS. 489 a coral as Syringopora ; but whether these are really the remains of corals with their internal structure obliterated itis impossible to say. South of Cerrig Ceinwen I have found no jasper associated with these limestones in mass, though most of the limestone is “jaspery:” but in the masses to the north there are bands and isolated pieces of red jasper, which behave towards the limestones exactly as flint does to chalk, and a similar origin is at least suggested. Nodules of similar jasper occur in beds of the same series further south. 4. Disturbed masses near Dinas Llwyd. In this locality the intimate relations of slates, ashes, quartz, and lime- stone with one another and with basic igneous rocks are beautifully shown. On the eastside of the headland are slaty rocks, but on the west the rough irregular ashes and local breccias; on the western slope the following section is seen (fig. 7). The quartz here comes Fig. 7.—Section on west side of Dinas Llwyd. 8.E. | N. 8. a \\ > Uj \ ielINS\ 1. Ashes. 2. Quartz. 3. Diabase. 4. Breccia. 5. Ashy grit. in as a thick tongue from above, and it dies out behind on the surface. Near at hand is a diabase-dyke, probably belonging to the series; beyond this are some breccias, and then more gritty rocks. Here, then, the quartz is certainly not a fragment of old land, nor is it a contorted bed, but something that has formed where now we find it. In the grits are found fragments of similar quartz, which show the polygonal structure ; we may therefore even conclude that the quartz was a contemporary product. To the west, in the valley, lies a band of slate, and then comes a ridge of remarkable diabase, which is repeated in other ridges near Bodowen. Beyond this slates recur and form the headland of Trwyn-y-pare. The succeeding hollow is occupied by a limestone somewhat similar to those of Cerrig Ceinwen, and finally we come to the agglomerate of Porth Trwyn Mawr, referred to by Dr. Callaway. Comparing 490 REY. J. F, BLAKE ON THE the relations of these several rocks with those that obtain further to the north, they are not the same, and we must therefore regard the more special types as accidents in the series. There would appear to have been two volcanic foci—one near Llangefni, and the other near this spot, which latter may be connected with the area, to be subsequently described, on the other side of Malldraeth Bay. — I gather, therefore, that we have in this district a somewhat similar development to that which occurs between Valley and Pen- bryn-yr-Eglwys, with local differences, of which the principal is the absence of any granite amongst the ashes or pelites of the district. I can see no reason for widely separating any part of the rocks on the east side of the fault from their neighbours. THe WestERN Reeion.—We can now consider the area which lies on the western side of the dividing line; and as the main feature of this is the granite, and our view of the stratigraphy must necessarily depend on the nature of this rock, and as it has lately been denied that it is granite, but asserted to be a metamorphic sedimentary rock, it is necessary, in the first place, to bring field-observations to prove that it is intrusive. a. The Intrusive Occurrence of the Granite.—The proofs of this are so many that their enumeration threatens to be tedious. To adduce them all, however, is a necessity forced on us by recent literature. Commencing at the south-western end, we find the eastern side of Llyn Faelog coloured as granite. Here there are a number of bosses of rock protruding from the ground. On examining several of these, we find the two sides composed of different material; on the one side is the pelite, on the other the granite. The passage from one into the other is obscure, and from this locality alone it would be open to any one to say that they here recognized the gradual metamorphosis of the sedimentary rock into granitoidite. But we can also interpret the phenomenon as an absorption by the granite of the neighbouring rock, in circumstances under which the former was kept long heated in contact with the latter. On the coast at Porth-ceryg-defaid the pelite again contains patches of the granite, but they are both brecciated. Ata small promontory be- tween this and Porth-y-ly-wod, however, we get the first clear proof of intrusion. Here on the shore is a low boss of rock, with all its surface bare (see fig. 8). The pelite is more or less orientated in the direction of the sea. Into this, and running in the same general direction, but in more than one place crossing its structural lines, is a tongue of granite from 3 to 4 feet. wide, which connects the two parts of the boss, and finally disappears with it beneath the sand. Hard by to the east is another smaller string of granite not quite parallel to the larger tongue, and also crossing the lines of the pelite, but dying out before reaching the second half of the boss, and the rocks in both parts are perfectly distinct. The granite, in structure, is seen to be much brecciated, doubtless in the subsequent compressions of the rocks; but in the unbroken parts it presents a typical holocrystalline granitic arrangement, with largish patches of original white mica. MONIAN SYSTEM OF ROCKS. 491 Fig. 8.—Plan of Shore, west of Porth-y-ly-wod. — ———- yy — = —y—- —— = on - =~! C dpe eel A Wee ee. ~*~ L, - a ef ate -~ 74 . 1. Ashy pelite. 2. Granite. 3. Sea-sand. Passing up the eastern side, we find another junction at Melin Ddrydwy, on the slope of the west bank of the stream. Here the disposition of the granite and its neighbour is as shown in fig. 9. Fig. 9.—Section on West side of Stream at Melin Ddrydwy. tA 1. Quartz-felspar porphyry. 2. “Hélleflinta.” 3. Pathway. 4. River. The line between the two rocks is very clearly defined, but also irregular. The granite appears on the upper, that is on the western side. It would be difficult to regard this as anything but an intrusive junction. The “granite,” however, here is changed into a quartz-felspar porphyry, the porphyritic crystals showing signs of great pressure. We next arrive at Gualchmai. Here, just west of the road 492 REY. J. F. BLAKE ON THE leading down from the church, there is marked on the Survey map an isolated, tongue-like mass of granite, cut off on the north from another tongue which reaches down southwards from Bodwrog church. Now this tongue of granite actually exists, and is sur- rounded by sedimentary rocks as represented, those on the western side being different from those on the east, the former being halle- flinta and the latter grey gneiss. Of course a metamorphosed sedimentary rock might be got into this position by complicated faulting; hut intrusion is the more obvious method. On the slopes of the granite hill, the granite and hilleflinta are inextricably mixed, after the same manner as at Llyn Faelog*. Further north the granite comes in contact with the grey gneiss, and has ashy beds on the other side of the tongue. The actual junction is hidden beneath the road at Bodwrog church; but the grey gneiss is disturbed, where seen nearest to the granite, and is penetrated by small half-inch veins of granite. Unfortunately these veins cannot be traced beneath the roadway into the solid mass on the other side. Here, again, the simplest explanation is an intrusion. Beyond this spot there intervenes a long belt of diorite, and I have been unable to find a junction of any kind. Dr. Callaway, however, records an exposure 8.W. of Craig Llwyd, which I seem to have missed, where the “ hornblende-gneiss is interstratified with granitoidite ;” this may be an intrusion of the granite into the diorite. Also to the 8.W. of Plas Llanfihangel there are gneissose rocks, and others of mixed character, having granite segregation- veins (?) in the midst of schistose diorite,—a sort of irregular ‘handed gneiss,” but the whole area gives very little definite information. On the western side the boundary of the granite is not promising, as it is overlain unconformably by the Ordovician grits. However, at the outlier near Tafarn-y-botel there is a quarry in a beautiful micaceous gneiss, which forms part of the general mass of similar rock composing this outlier; but in the quarry floor there is an irregular tongue of granite, quite distinct in character, and with clear lines of separation. Iam doubtful whether this is really intrusive or due to segregation, but I strongly incline to the former view. In the area between the two turnpike-roads the older rocks are exposed, and south of the Star Inn the junction of the granite with them, if not actually seen, may be determined accurately in position. Here Dr. Callaway sees a gradual change from one into the other, though the bounding rock is certainly not a dark schist; but I see an indefinite boundary such as we have elsewhere observed. The indications to be met with in the interior of the mass are still more decisive than those on the boundary. One small patch of “Cambrian” is marked on the Survey map as occurring in the midst of the granite at the farm of Maen Gwyn. This spot I examined in the company of Prof. Sollas. In the sides of the * This seems to be the spot described by Dr. Callaway in Geol. Mag. 1880; but the bedding he describes does not seem to be observable. MONIAN SYSTEM OF ROCKS, 493 farmyard are seen masses of pelite, flaky and somewhat micaceous. This micaceous character increases towards one side of the yard, and here there is an intrusion of the granite into it (see fig. 10). Fig. 10.—Plan of the Farmyard of Maen Gwyn. / Y Sila Sein YU UY Z YY Uy Yy ) S 1. Granite. 2. Micaceous Pelite. The granite occurs in one boss in a gradually narrowing vein, with a quite irregular course, and branching out it dies away in quartzose strings in the midst of the pelite which overlies and underlies it. Separate from this is another patch of granite surrounded by the pelite and crossing its structural lines. This expands from a narrow neck into a larger mass, and here entirely surrounds a kind of inlier of the pelite, or, as one might more correctly call it here, the micaceous schist. The two rocks at the contact are so distinct that both may be recognized in any small hand-specimen. Is there any escape from this ? There is a second such inlier on the Survey map, near Llecheyn- farwy ; but at the spot indicated I could find no rock which ought to have been thus coloured, and certainly no granite junction. A long tongue is also indicated as running up N.H. from near Gwyndy. This I have verified, but could seldom find the actual junction; only in one knob, south-west of the farm of Y-foel, did the surface of the rock show a vein of granite running into the pelite. On the road from Gwyndy southwards the relations of the granite to its neighbour are not very clear, and resemble rather those to the south of the 494 REV. J. F. BLAKE ON THE Star Inn; but at the farm of Cefn-eth-groen there is a quarry in which a distinct junction may be seen. The actual piece of pelite seen must be an included fragment, since the mass of the rock is away to the west. This patch clings to a vertical surface of the granite on its eastern side (see fig. 11). Fig. 11.—Section at Cefn-eth-groen Farm. 4 1. Granite. 2. Pelite. 3. Junction in Map. 4. Farm. A little to the south of this we come to the region of Craig-yr- allor. Between that craig and the new Holyhead road is another eminence, called Craig Cocyn. On the surface of this craig the granite is seen in tongues, which enter the dark hornblende-schist. Sometimes these tongues are of the ordinary character, cutting across the edges of the folia of the darker rock; but at others they seem pulled out into lenticles, which in this case run with the average schistosity (as in fig. 12). Thence we may pass to a more Fig. 12.—Granite in Hornblende-schist, Craig Cocyn. SS fA LS a ‘ BN 2 fi CEN rhe 1. Granite. 2. Hornblende-schist. intimate blending of the two rocks, with the production of a form of banded gneiss. Whether or not we accept Mr. Teall’s explanation of the mode of formation of such gneisses, it is to be noted that this, the most mechanical of all explanations, involves an intrusion of the granite to start with. Finally, we come to the tongue of ‘ Cambrian” on the map, which crosses the turnpike-road, and in this we observe the same indefinite- ness of granite and pelite as is seen at Llyn Faelog, the more central portion being free from granitic material. MONIAN SYSTEM OF ROCKS. 495 In some of these cases we have clear intrusive junctions, in others the junction is indefinite. The cause of this difference seems to depend partly on the nature of the neighbour and partly on its relation to the mass of the granites which in the latter case had the power of absorption, but not in the former. Such is the positive evidence that the granite of this district is intrusive. If it is insufficient, I can have no conception of what would suffice. If it is accepted, a lesson is read to us on the danger of relying too much on minute and indescribable differences in the microscopic structure of a rock. b. Lhe Nature of the “ Granite.”—I have used the term granite throughout, partly because it is so coloured on the Survey map, and partly because, if one term only is to be chosen, this is the most gene- rally applicable. But in reality under this one term a great variety of rocks, not to mention those which are obviously distinct, must be included, though I believe them all to be connected portions of one great mass. Perhaps the most typical granite is that found at Hen-blas, near Llandrygarn, which on comparison with that from Kingstown, near Dublin, shows a resemblance amounting to almost absolute identity, the only differences being the less freshness of the mica and the smaller individuals of the quartz. One is almost tempted to ask if this can belong to a distinct and later eruption, only it is easy to recognize that some at least of the others, as that at Gualchmai, only differ by brecciation and alteration. The next in order of alteration, after this at Hen-blas, is in a mass or tongue between two diorites about a mile and a half to the north; and the next is the great mass seen in the cutting at Llanfaelog, where some of the felspars are almost porphyritic, and all the mica has either induced, or been developed in, the cracks. The granite near Craig- yr-allor is tolerably whole, but the other samples that I have exa- mined are all more or less broken, and become in some places regular endoclastic breccias (shall we say ‘“‘ endoclasts” ?). They are, how- ever, mostly from places rather near the boundary. Such is the rock at Gualchmai, at Yr-ynys-goed, Coedana, and from the Llaner- chymedd railway, near the ninth milestone. But the most brecci- ated of all that I have examined comes from the interior, at Bryn twrog, south of the railway just mentioned. The granite in the two tongues near Porth-ceryg-defaid and at Maen-gwyn differs in another way. It isnot so much brecciated, but has a larger supply than usual of clean white mica, similar, in the latter case, to the mica developed in the neighbouring pelite. All these granites differ less in their internal structure than would be expected from their external aspect. This latter is partly dependent on the size of the crystals, and partly on the brecciation, which has brought about the introduction of substances which alter the appearance, but leave the intervening granite untouched. We may take them all, therefore, to be parts of a single massif. In two places, however, we find felsitic rocks, and, probably, there are _ several more, as the granite has not been examined in every spot, and these may be said to have been noted by accident. They are Q.J.G.S8. No. 175. 24 496 REV. J. F. BLAKE ON THE at the junction near Melin Ddrydwy, and at Tyn-y-pwll in the centre, near Bryn twrog. c. The Associates of the Granite—These are the most difficult to understand, and I can only do my best to interpret them. The descriptions hitherto given have gone on the assumption that the rocks were of ordinary sedimentary origin, their crystalline cha- racter being due to subsequent metamorphosis. But, so far as [ can understand it, the whole is one great volcanic complex, of which we only see the base—the rocks with fluidal structure, and the scoriz, if they were ever present, having disap- peared. There are, in fact, besides the granite, four main types of rock within the area—the hilleflintas, the pelites, the gneisses, and the diorites. 1. The Halleflimtas. Dr. Callaway makes his hilleflinta occupy a very small area, from less than half a mile on the coast to nearly nothing at Gualchmai. It is a remarkable, compact rock, without a sign of lamination or stratification, and consists of very minute quartzose fragments. When the grey gneiss is brecciated it is hard to distinguish between the two; indeed, I think, the rock near Llangwllog, noted by Dr. Callaway, is of the latter kind; this,. however, can only contain fragments of its own substance, whereas the hilleflinta contains foreign particles, of which the most easily recognized are of plagioclase felspar. This rock runs in a narrow band from the coast to Gualchmai, where it all along intervenes: between the grey gneiss and the granite. It then passes on the western side of the granite tongue, and is in its most beautiful form, a blue, slaty-looking, finely false-bedded rock, by the side of the Holyhead road. It cannot be clearly recognized much beyond Tyn- rhos, on the same line, but occurs again on the other side of the granite at Gors Mill and Gwyndy. This irregular and restricted distribution is not to be wondered at in a volcanic dust, but would be very puzzling in a basal rock. It so interdigitates and shades off into the other rocks of the granite area, that I take them to be . all connected, and to be brought next the grey gneiss by a fault, of which there is abundant indication in the field by the sudden change of rock *. 2, The Pelite. This is somewhat different from the rock so called in the western district, inasmuch as it tends more to stratifi- cation, as in the lenticular variety. It is in fact a volcanic mud, which has sometimes particles large enough to justify the title of an ash. There is usually no quartz in it, except in secondary veins, and the whole is composed of fine polarizing flakes. When the fragments are large enough to be recognized they might be derived from a granitic rock, but not from the granite itself, which in places intrudes into the pelite. It cannot, however, be always distinguished in the field from an endoclast of the granite and asso- ciated diorite. We find this rock intervening between the halleflinta and the granite on the south shore, with an intrusive vein of the * Drawn by Dr. Callaway in his article in the Geol. Mag. 1880. MONIAN SYSTEM OF ROCKS. 497 latter. It is found in the centre between the two granite tongues at Llanfaelog, where it is called “Silurian?” in the Survey map, and skirts the east side of Llyn Faelog. It also lies next the granite near T'ycroes, and is found in patches between Llanfaelog and Pen-y-carnisiog. It forms the tongue of “Cambrian ” that cuts the Holyhead road and into which the diorite intrudes further north. Near Bodwrog church it lies between the hilleflinta and the erey gneiss, being separated from the latter by the granite. The rock that forms the long tongue north of Gwyndy is more of this type than any other, and it occurs on the other side of the granite near Llanerchymedd windmill. The name, however, is an inclusive one for all somewhat similar rocks which have no special character. On the whole it is found more to the west than the hiilleflinta, but at Bodwrog it is next the grey gneiss. 3. The Gneisses. We find these, apparently graduating into the pelites, near Llecheynfarwy. They have here a banded character. Also near the farm of Mynydd Mawr the rocks are very quartzose rough gneisses not in the least like the grey gneiss. This type of rock is continued to 'l'afarn-y-botel, where the granite intrudes, and is the most difficult of all to understand. At the latter place it is a beautifully clean crystallized rock, composed of quartz and felspar quite fresh, and black mica, which has in part passed over into another mineral. There is nothing like this rock in the whole of Anglesey elsewhere, and the question is suggested whether Wwe may not touch here a piece of genuine Archean. The nearest rock to this in character occurs on the north-east near Plas Llanfi- hangel. In connexion with this may be mentioned a mass of rock in the centre of the granite, on the railway between Llangwllog and Llanerchymedd, which is more like grey gneiss, with an extraordi- nary amount of white mica and sericite, amounting to half its yolume, and with which a calcareous rock is associated. 4. The Disrites. This is the only name I can satisfactorily give to the rocks which in many places are hornblende-schists. They appear partly as “ gneiss” and partly as ‘‘ greenstone” in the Survey map, and they figurein Dr. Callaway’s descriptions as ‘“ dark schists.” Sir A. Ramsay regards them all as metamorphic sedi- mentary rocks. No doubt their foliated appearance suggests sedi- mentation; but I find that so long ago as 1872, in Jukes’s ‘ Manual of Geology,’ it is stated of hornblende-schists that “there is reason to believe that as they occur among altered sedimentary rocks they may represent former trap-rocks ;” and of recent years this conclusion has been verified by Williams in America, and by Teall in this country. It was not, however, entirely their foliation which led Sir A. Ramsay to his conclusion, since he places in the same category in the memoir the unfoliated rock which is coloured green- stone on the map, but it was rather the shading off of both this and the granite into the surrounding rock which convinced him that the one was the derivative of the other. It is for the microscope to decide which isthe original rock. If it was the sedimentary one, then as we approached the crystalline, isolated crystals would appear 2L2 a /- sae os ae Ss eS Fe ee | SSeS. A SS 498 REV. J. F. BLAKE ON THE in the unaltered sediment, and these would gradually increase in number till, leaving no interval between them, they occupied the whole rock. It is an approach to this that we see in the case of contact-metamorphism. If, on the other hand, the crystalline rock was the original, and the other produced from it by brecciation, we should find the cracks increasing as we approached the margin, till at last the rock was a mass of crystalline fragments, which might get smaller and fewer as the sedimentary rock received other ingredients. Between these two phenomena there is a very clear difference, and in the present case the answer of the microscope is entirely in favour of the latter. This, however, does not dispose of the idea of the “‘dark schist” being an altered sedimentary rock of an older series. Such a contention would have to be proved on the clearest stratigraphical evidence, for beyond being both “ schists” and both ‘ dark,” there is nothing lithologically in common between these and the Holyhead rocks; the one set are composed of quartz and chlorite, and the other of plagioclase and hornblende. No stra- tigraphical evidence, however, can here be brought forward, since the diorite only approaches the grey gneiss in one spot, near the stream north of Llangwllog, and then it is on the wrong side. There are four areas in which these dioritic rocks occur. The best known is that round Craig-yr-allor. Here Dr. Callaway states that “grey gneiss passes up through the dark type into the grani- toidite.” I could find, however, no grey gneiss here at all. The country is rather low and marshy, and out of it stand up several bosses of rock. Some of these are composed of the ashy pelite con- taining granite veins, and in one place there is apparently an intrusion of the diorite. This rock is mostly confined to the centre, where it is schistose in some bosses, and not soinothers. In the southern boss itis veined by granite, as before described. In parts the hornblende and plagioclase are so intimately mixed that the rock is uniformly dark; in others the lighter-coloured felspar has segregated into lenticular flakes, but in such cases there are no signs of movement in the material of the rock. Nothing is ever seen below the diorite, of which the boundary is fairly marked on the Survey map. All round it are the clastic rocks, some, as in the northern tongue, being produced by its brecciation, the hornblende having mostly turned into chlorite and calcite. The rocks to the west are of the same ashy character, but usually develop more mica. A second area runs from near Pont-rhyd-defaid as far as Lle- cheynfarwy. This consists partly of good crystalline diorite, partly of altered varieties of the same, in which a few particles of quartz and the alteration of hornblende into chlorite begin an approach to rocks of another type, from which, however, they are still distinguished, by their build, by the prevalence of plagioclase and the presence of sphene. A third area, connected with the first, according to Dr. Callaway, by exposures of diorite near Pentrefelin, runs from Llandrygarn farm to Mynydd-Mawr farm, thus escaping from the surrounding granite, and being overlain by the Ordovician grits. The arrange- MONIAN SYSTEM OF ROCKS. 499 ment of the rocks is here very complicated. From Llandrygarn to Ynys Dodyn there are good diorites, with a band of granite in the centre at the latter place; but round Mynydd Mawr the diorites are inextricably mixed with the quartzose gneiss, and can scarcely be anything but intrusive. The fourth dioritic area is that long tongue which skirts the east side of the granite, and figures truly as greenstone on the Survey map. As seen on the east side of Plas Llanfihangel this is in every way comparable to the rocks at Craig-yr-allor, where the foliated hornblendic rock is spotted with lighter flakes of felspar. Between this spot and the granite it is a very complex rock with well-marked granitic segregation-veins, which may serve to throw light on the origin of some of the smaller veins and flakes which spot the diorite breccias near Llecheynfarwy and elsewhere. At Yr-ynys- goed the “ greenstone” is a broken mass, infiltrated with chlorite- veins, of quartz- and mica-particles so arranged as to suggest that it may be really a brecciated form of the grey gneiss. A little further to the south we come on the true grey gneiss with the diorite lying to the west, but just on the other side of the stream it is so broken up as to suggest a fault. Besides the above four types of rock there is a granitic-looking rock at Bryngolen, and a remarkable andesitic rock just north of Lecheynfarwy ; and Prof. Bonney has indicated that some parts in the hilleflinta-band consist of quartz-felsite. These observations are not sufficient to give a complete idea of the granitic area, which would require the microscopical examina- tion of every single exposure; but they are enough to show that no stratigraphical sequence can be truly made out, as every one that is suggested by one district will be contradicted by another. Hence, considering the nature of the rocks, we may regard the whole as showing the characteristic irregularity of an eruptive centre, in which acid and basic intrusions take place in basic and acid ashes and mud, and subsequent or consequent disturbances break up and mingle them all in confusion. The order of events would seem to be, first the protrusion of the diorite, under the influence of foliating forces ; then the production of the hialleflinta, perhaps from the fragments of the grey gneiss, and of the pelite from the materials of the diorite, and these perhaps took place more or less simultaneously and repeatedly ; but after all this came the intrusion of the granite, which is thus the most recent rock of the whole development. The relation in age of the granite and its associates to the grey gneiss and other rocks of the eastern region cannot directly be proved; but that the former are younger is @ priort probable, because in the Western District volcanic rocks form the upper part, and here also they are followed vy the Ordovician ; while it would require very complicated stratigraphy to make the grey gneiss the younger, to say nothing of the probable intrusion, in more places than one, of the granite into that rock itself. d. Bodafon Mountain to Llanerchymedd.—The rocks which lie beyond the granite to the north-east are, with the exception of 500 REV. J. F. BLAKE ON THE Bodafon mountain and Craig Fryr, considered by Dr. Callaway to belong to his slaty series. In this, I think, he is right; they are the continuations northward of the hilleflintas and the pelites, while Bodafon mountain and Craig Fryr are modifications of the grey gneiss. The two most remarkable features in these pelites are the comparative fineness of the materials, and the unusnal amount of sericite or chlorite developed in the interstices. With regard to the upper group the same kind of fine orientated dust which occurs in the extreme south here again produced dull sericitic slates with well-developed cleavage, such as are best seen at Man-addwyn and Trewyn, while to the north the great shoulder of Bodafon called Clegyr is a more compact and halleflintoid variety of the same. The slopes on the west side of Bodafon are coarse and more quartzose, and recall the halleflinta of Tycroes and Gualchmai, but they are very chloritic and also foliated. These are so comparable under the micro- scope with the finer-grained chloritic schists (though the latter are less altered) that one is tempted to include them in the lower series ; but their microscopic aspect is not schistose, and their relations to the Bodafon quartzite is not one of conformable stratification. There is an interesting variation at the fork of the roads near Clorach bach, in the form of a pink massive limestone, now brecciated, and the fine dust-rock in the neighbourhood is largely impregnated with calcite. This feature reminds one of Cerrig Ceinwen and other sporadic limestones, but I have found no quartz-knobs here. A coarse grit-band occurs near the line of junction at Man-addwyn, and there is reason to believe that there are, or have been, other grit-bands in the series still coarser and more felspathic. In other areas the rocks most similar to these in general character are the dust-rock at Pant-yr-Eglwys, and the slates on the railway north of Llangefni. The relations of these rocks to those of Bodafon mountain seem to be everywhere those brought about by a fault. This has been shown by Dr. Callaway for the south-west end, and it is equally true at Clegyr, where the fine-grained slate and the grey quartzite are seen side by side with not a foot’s breadth between them. But lam not quite certain of the character and age of this fault. The Bodafon quartzite is a highly foliated rock with a large proportion of other ingredients than quartz, and the grains of the latter are of small size. It thus approaches in character some varieties of the grey gneiss, but, lacking any recognizable felspar, may properly be referred to the lower part, on the horizon of the Holyhead quartzite. It in no way resembles even the most stratified in appearance of the quartz-knobs. Seen from certain aspects, the bedding with a low dip to the S.E. seems evident. Thus it ought to be followed by chloritic schist, and so pass up to the finer shales; but it does not; on the eastern side fragments of the slate lie on it, which, though broken as now found, must have been the next succeeding rock. It is possible therefore that the fault may have taken place in con- nexion with the eruptive outbreak, and the finer dust-rocks have been deposited against the cliff thus formed. No doubt it has been faulted again—Craig Fryr has been cut off, Bodafon has been MONIAN SYSTEM OF ROCKS. 501 divided; but the original arrangement of the rock seems to be that of an unconformity as well as of a fault. This does not make the two rocks belong to two distinct and independent series. ‘The circumstances, of course, had changed ; but the eruption of large masses of rock must be accompanied by such changes. It is not at all to be assumed that there was only one eruption ; the varieties of the ‘‘ granite” indicate that there were several, and some portions of the dust-rocks may be subsequent to or derived from the earlier masses. To the north-east of Llanerchymedd there is a lofty hill called Y Foel. It is used as a trigonometrical station, and largely quarried for road-stone. It consists of Ordovician conglomerate*. On the eastern side it passes into a great beach-breccia, in which there are numerous kinds of rock, of which I made a small collection, and found them to agree, each with each, with samples collected from the slaty series to the east, with the exception of a coarse blue grit, which as yet, Lhave not found amongthem. Atthe commencement, therefore, of the Ordovician era these older rocks must have been already carved into hills and valleys. Between Foel-fach and Tyddyn-bach is seen one of these hills in the form of brecciated grey gneiss, which may be traced some way round the southern slopes of the hill. We thus have a continuation of the older part of the series to the north, and an indication that the Ordovician here forms little more than a skin on the surface. Sir A. Ramsay speculates on the ‘ greenstone” masses to the north of Llandyfrydog being also relics of the more ancient rocks; but those I have examined are examples of the black, highly crystalline diorites, in some cases picrites, which everywhere jut up amongst the more modern as well as the more ancient rocks, and seem to be of much later date than the latter. Summary of the Central District. This is divisible into two parts. In the eastern region we have an interrupted upward succession, commencing with a grey gneiss, whose lower part, at least, and its representative further north, in Bodafon mountain, is comparable to the quartz-schists of Holyhead, while its upper part may be more or less the representative of the chloritic schists. These rocks are continued on the other side of a fault by dark, chloritic ashes intermingled with slates and grits and other sedimentary deposits. At either end of this range they develop great agglomerates, and in the southern promontory exhibit the irregularity of volcanic eruptions, mingled with basic lavas. They contain also sporadic limestones, some of which are bedded and possibly fossiliferous and contain nests of jasper. There are also quartz-knobs, which may attain a large size and approximate to stratified deposits. The series may thus be compared with that which lies towards the north in the western district. In the western region we have the largest and most complex volcanic group * Described by Prof. Hughes, Quart, Journ, Geol, Soc, vol. xxxviii. 1c. ees ie a pea See ee ee 502 REY. J. F. BLAKE ON THE in the island, the base of which is now exposed by denudation ; as. its central mass there is a great variety of granite-rocks, which are intrusive in many cases into those around them. Some of these surrounding rocks may be absorbed by the granite, and some may have been produced by its brecciation. But anterior to the granite, and intruded into by it, is a highly foliated diorite, which now occurs in more or less isolated areas. There are no agglomerates in this region, but the ashes are everywhere minute, whether in ‘the more acid form, as halleflintas, or the less acid, as pelites; and they are much impregnated with secondary minerals. Calcareous bands are also present among them. Some of the rocks found exposed between the masses of granite are of obscure origin, and by their thoroughly crystalline and foliated character, and yet their distinctness from the grey gneiss, suggest the possibility of their being truly Archean. With very few exceptions the whole of the rocks in this district are composed of finer ingredients, and are more metamorphosed than those of the western district. They are overlain in all but their eastern margin ‘by the basal rocks of the Ordovician, which everywhere contain their fragments. In spite of the separation by faulting, and the apparent unconformability at Bodafon, there is a unity of character and intimate association amongst all the parts that prevents us separating any part more widely from another than as earlier and later developments of one great system. Tue District West oF TrAarta Dvtas. This is a small and entirely isolated area which, from its proximity to Bodafon mountain, is naturally described in the present order. It figures on the Survey map as “ altered Silurian,” though no reason for this is assigned in the memoir. Dr. Roberts has shown that to the west of Pen-lon a conglomerate which he calls. Cambrian, but which is really the Ordovician basement-bed, lies over the granite. This is, in fact, carried on to the top of the granite: area somewhat as marked in the Survey map, and is continued all along the northern boundary as far as Llaneiddog; on the southern side grits are seen at the junction in the road from Wern, and also. in the stream that runs out at Traeth Dulas. It is thus surrounded by Ordovician basement-beds, and there can be no doubt of its being Pre-Ordovician. The conglomerate, however, which is in two or three bands, is not composed of the. PES underlying rock, but of quartz and jasper. The district is not noticed by Dr. Callaway, and the sole descrip tion by Sir A. Ramsay is as follows :—‘ The granite is necessarily mapped chiefly as one mass with several smaller patches, piercing the associated highly metamorphic gneissic mica-schist on the south ; but in reality they are inseparable from each other, so intimately do they seem to be interlaced.” This old island is, in fact, a mass of granite intruding into what appears to represent the grey gneiss. We have seen the latter so MONIAN SYSTEM OF ROCKS. 503 come up as far as Llanerchymedd, and all the rocks that I have examined which are not granite are very clean gneisses of felspar, quartz, and white mica, for the most part beautifully foliated, but in one instance, in which the rock has a felsitic aspect macroscopically, entirely without foliation, though otherwise of exactly the same structure. Others not microscopically examined have a more slaty or pelitic appearance, and one, at least, is composed of such granitic materials as to suggest derivation from granite. Yet at the only spot where the contact is seen it has a thoroughly intrusive appearance (see fig. 13). ‘The granite itself, which is best seen at Pen-lon, and Fig. 13.—Section in Quarry east of Pen-lon. N co . 5 ANS | 1 2 1. Granite. 2. Schistose micaceous rock, at Llaneiddog Bach, is different from that in any other district, being nearly pure white, of fine grain, and abundantly supplied with crystals of white mica. It has a very slight tendency to foliation ; even this, however, is subject to variation, and the above description applies best to the variety at Llaneiddog Bach. Possibly this may be an older mass than any other, composed of the same material which supplied the grey gneiss, before the dioritic eruptions had commenced. It is remarkable that this district is one of the very few Pre-Cambrian ones in which lead-ores occur, though these are probably of Post-Ordovician date. Tue Eastern District. In spite of its easy accessibility this district has been sadly neglected. In many respects it is the most interesting, and in some respects certainly the most difficult of all to understand. Neither Sir A. Ramsay nor Dr. Callaway tell us much about it, and there is much more to tell. Origin or THE HoRNBLENDE-SCHISTS.—For the right interpretation of the larger part of the area the first necessity is to come to a conclu- —* Ss LS eT eae Se See GS ESET LE Ee zi 504 REV. J. F. BLAKE ON THE sion with respect to the so-called “ gneiss” or “ dark schist.” And the conclusion to which I have been drawn, much against previous prejudices, is, that it is all of igneous origin. And this I must commence by demonstrating*. Now the mass to the north of Holland Arms to a great extent lacks foliation, and is composed of large crystals of green hornblende, mingled irregularly with dusty felspar, in this respect agreeing with the less foliated masses at Craig-yr-allor. In the hill to the north of Y-graig there is a parallel arrangement of the more hornblendic and the more felspathic portions, producing a lenticularly banded rock, again to be matched at Craig-yr-allor and other localities in the central district. These hornblendes pass, in places, at their edges into a bright-blue tinted mineral, and the felspar into epidote. At the edge of this mass, on the south side of Y-graig, the hornblende, partially converted into chlorite, appears in isolated needles, mingled with numerous grains of epidote, the minute portion intervening being quite clear, and possibly quartz or felspar. This mass is clearly isolated in the midst of the grey gneiss to be presently described. To the east are two other apparently isolated patches at, and to the north of, the Gaerwen windmill. In one we have the lenticularly banded diorite, and in the other the same network of hornblende-needles and epidote grains, in part foliated and in part not. Now rocks of this type, for the most part beautifully and finely foliated, with exquisite contortions, pass into the glaucophane- rock which I have lately described +. A map of the distribution of these rocks amongst the mica-schists shows that they are mostly sporadic ; so that though it might be possible to conceive of such an arrangement by complicated folding in more than one direction, the far more natural explanation is that of their being intrusive masses, especially as there is, within certain limits, considerable variation in their respective neighbours. Again, though some of these patches are foliated, others are not, and therein they agree with the rocks at Gaerwen, as they do in all other respects. These observations alone might suggest the igneous origin of the rock, but fortunately in the two cuttings made by the railway we get decisive proof. In that near Llangaffo, which I examined in the company of Prof. Sollas, we have the following section (see fig. 14). Entering from the east, we find the micaceous grey gneiss slightly dipping E., and it soon becomes contorted. This contortion is seen to be in connexion with a dark foliated rock, which intrudes upon it in an irregular manner. ‘This is followed by another smaller intrusion, and in all the neighbourhood of these the gneiss is much disturbed ; its folia are lost in immediate contact with the intrusion, and it looks almost like a hilleflinta, but is still gneissose in structure. Further west these phenomena disappear; the grey * Prof. Bonney, indeed, calls one example submitted to him a diorite (Geol. Mag. 1880, p. 127); and Dr. Callaway has lately shown that the foliated rock at Gaerwen is of the same character (Brit. Assoc. Rep. 1887). Further than io no oe seems to have considered the possibility of an igneous origin for these schists. Tt Geol. Mag. dec. 3, vol. v. p. 125. MONIAN SYSTEM OF ROCKS. gneiss becomes nearly horizontal, and finally turns up and becomes darker at the end of the cutting. Now this intrusive rock is of similar structure to the patches we have been considering further west—with the same needles of chloritized hornblende and the same epidote-spots, and in part it is foliated and in part it is not. a = ———— SS == RFE 1. Quartz-knob. 4, Finer conglomerate. 5. Grey shale. f. Faults. 2. Purple shale. 3. Great conglomerate. is, at the base of the sequence, is seen a mass of quartzite; above this is a wedge of ashy rock getting smaller at the base—and this is followed by a great band of red jasper-conglomerate, the pebbles in which are very large. The series is then cut off by a fault, and the rocks on the other side are broken. First comes a wedge of purplish slate, apparently faulted in, then a slice which has grey shales on the top, and seems to rest on a conglomerate at the inac- cessible base ; then another fault, and then some similar shales lying certainly on a considerable quantity of conglomerate of finer character, which continues to the base of the cliff. We may safely take the upper conglomerate and shale (4, 5) here to be Ordovician, though the latter is not black; but the great red conglomerate below seems to be too intimately connected with the quartz-knob to belong to a distinct system; and if it does not, then we lose all sight of the MONIAN SYSTEM OF ROCKS, 521 basal Ordovician before reaching Hells Mouth, where only the quartz is left, and the basal Ordovician never appears in the*same form again. The quartz-knob, like others of its kind, dies out on the east side; and below its expected position are some very Ordovician-looking slates, though not like the black slates of the district nor the grey shales just seen; and in these there is a lode of copper. A little further east rises the greatest quartz-knob of the district, called Craig Wen, and worked for “China stone.” This lies, as regards position, above the slates just mentioned, and some red quartz-conglomerates cling closely to its western side. It is imme- diately to the north of this quartz-knob that the ashy slates which have proved fossiliferous occur. We might expect some light to be thrown on the sequence in the cliffs of Borth Wen; but, un- fortunately, both quartz and conglomerate die out before reaching it. Fig. 23.— View of Borth Wen, west side. Craig Wen. Fossils. N. 1. Quartz. 2., Red conglomerate. 3. Fine conglomerate. 4. Ashes, 5. Slaty ashes. What we actually do see is exhibited in fig. 23. On the south side the rocks appear thoroughly confused, masses of quartz roaming about, under no law, among beds of a soft and incoherent character. This might perhaps be attributed to disturbance, but it is much more suggestive of the irregularity caused by the motion and deposit due to siliceous waters, in fact the underground branchings of the quartz-knob. To the north come on, rather rapidly, more regular slaty rocks, of ashy character. I found it impossible to determine the exact way in which these are connected with the disturbed rocks below ; certainly the boundary is not a clean one, and no additional disturbance can be made out. It is in these rocks, at the top of the tramway, that Prof. Hughes has discovered fossils. On the shore, by the pier, stands a mass of quartz, and on its northern side a large mass of coarse red conglomerate. These are followed on the shore by similar ashy shales, and these ashy-looking rocks continue to the end of the cliff, becoming very irregular and losing apparent stratification, and containing several bands of finer and 2 REY, J. F. BLAKE ON THE coarser conglomerate, dying out above, as marked in the figure, Before attempting to discuss this section, we must obtain the data offered by the continuation of the series on the eastern side of the Borth. Passing round the shore, we encounter several knobs of quartz and limestone, which now add nothing to our information, and then at Porth Pridd we find another of the Ordovician slices let down by faults. This fragment consists of the ordinary black shales with indurated bands, showing that the true Ordovician remains constant here. The fault on the north is an overthrust fault, and the rocks beyond it are the ashy shales, with fragments of limestone cemented in the fault. In these shales we soon find small quartz-knobs, and further east these form a well-marked crest. This crest is so instructive that a plan of it is given in fig. 24. Fig. 24.—Plan of the Hill-crest, west of Porth Llechog, x ty a *y eT | SS xe = ——————— —— a ee ee Oa s —— oe * \ eS Cs SS B25 ———— ———— re ae SS Ae bag ————— 2 2 1. Laminated ashes. 2. Quartz. 3. Quartz-conglomerate. Here the direction of the lines of subdivision in the ashy slates, which are parallel to the bedding, as indicated by the changes, is along the length of the crest: there is no disturbance or irregularity. The quartz-knobs may be seen on the lower slope and creeping up the hill across the bedding, and then turning round and lying in the direction of the bedding, the several beds coming directly against them. Beyond these quartzites, and therefore higher in the series, yet closely associated with them, is a band of coarse conglomerates whose pebbles have been derived from the quartzite itself; they come in with the quartz, and they disappear with the quartz, and the size of the pebbles diminishes as we pass upwards from the quartz. The natural interpretation of these phenomena is that the quartz has been forced across the edges of the ashes ; and the simplest method of accounting for this is by hot siliceous springs, the quartz of which has immediately consolidated, and has then been broken up and rounded by the waves without any cessation of the ordinary deposits. In structure this quartz-knob is one of the purest, there being no recognizable rounded pebbles, but all being composed of the polygonal network. MONIAN SYSTEM OF ROCKS. 523 Traced further to the east, this quartz dies out with the crest ; but on the south side of the line there are several smaller quartz-knobs at various horizons, and on the north beds of finer conglomerate are intermingled with the ashy slates, which have a strong resemblance to those of Borth Wen, and these continue to the coast. The whole of the ashes and conglomerates of this group are highly cleaved, with a cleavage-strike parallel to their bedding. Neither conglomerate nor quartz-knob is to be found in the coast-section of Bull Bay; and, in spite of a careful search, on two or three occasions, between the slates of Amlwch and the ashy rocks of Trwyn Melyn, I have not been able to fix on any line of break at all. In considering the bearing of these facts, it must be admitted that if no fossils had been found I should unhesitatingly have considered all the rocks seen east of Porth Llanlliana, except the undoubted Ordovician slice at Porth Pridd, as belonging to the Pre-Cambrian series. The occurrence of conglomerates naturally suggests a new series; but when the rocks above and below the conglomerates are so similar, and every attempt to find a line of separation on the coast, where all is clear, has failed, one is fain to admit a conformable succession through the whole; and this view I still hold to be most probable, and am quite ready, if possible, to receive the fossils as characteristic of the system. Against the belief that these are true Bala fossils we have the fact that they are not like any other fossils in the island, though Bala beds are supposed to be found elsewhere; and the rocks that contain them are not like the other fossiliferous beds, which are found so close at hand. Even if they were Bala fossils, they could not possibly carry all the rocks of the northern district with them, since these are so clearly identical with those in the eastern district which are overlain by Cambrian, and they are in this very neighbourhood overlain by typical Ordovician. We should therefore have to find a fault or’ unconformity somewhere ; none has yet been found, though it might be obscured by cleavage, and conglomerates might suggest it; but even thus it would be difficult to account for the neigh- bouring Ordovician conglomerate at Ogo-gyfwr, &c. As regards the fossils themselves, they are referred to Orthis Bailyana by Prof. Hughes, and this fossil is said by Davidson to be associated in Wexford with Leptena sericea and other undoubted Ordovician fossils. By the kindness of Prof. Hughes I have been able to examine his fossils, and one of them is undoubtedly 0. Bailyana, while others do not seem identifiable with any described species. It will therefore become of importance to examine the true stratigraphical position and age of the rocks in Wexford in which this fossil occurs. Summary of the Northern District. The district is isolated by a curved fault, which is broken near Parys Mountain, and has a general hade to the north, along which the older groups have been pushed up over the black Ordovician eee REV. J. F. BLAKE ON THE shales. The lowest beds are true chloritic schists, not far removed in character from the nearest rocks of the same kind in the western district. ‘They become coarser, more quartzose, and more contorted in the heights of Mynydd Mechell, but ultimately obtain a pretty uniform EK. and W. strike. They are followed by ashy grits and sericitic shales, and then by a broad band of green slates, which are undisturbed and younger-looking in the west; but in the east, where the Parys Mountain has interfered with the motion, they have become greatly contorted. Towards the far east they become gritty again. They contain sporadic nests of limestone, and are scored by dykes, which were intruded previous to the faulting. The higher’ part of the series consists of laminated and, often, cleaved ashy rocks, which become agglomerates in the west, and contain large deposits of precipitated limestone and pure quartz-knobs, irregularly placed and crossing the bedding, Above these knobs, and derived from them, there are large conglomerates ; but they are succeeded in most places by ashy rocks similar to those below, which, in one place, have yielded fossils. The whole series is unconformably overlain by another set of conglomerates leading up into black shales, which are, in other places, let down between faults and contain Ordovician fossils. Tue District East or Parys Movuntarn, Proors oF THE Pre-Camprian AcE oF THE Rocxs.—This dis- trict is entirely isolated from the northern, though by a very narrow band. It is coloured on the Survey Map as “altered Silurian.” It is therefore necessary to prove that it is rightly included in the description of Pre-Cambrian rocks. This is not so easy a matter as in the case of the neighbouring district to the south of Traeth Dulas, since here there are no obviously overlying basal Ordovicians, but the main boundaries are faults. These faults, as seen on the sea-shore, have been well determined by Sir A. Ramsay, and have been again more recently described by Prof. Hughes*. Tracing the northern fault inland, we find it pretty correctly laid down on the Survey map, and the rocks on the two sides remain everywhere most distinct, as is well seen on the road between Rhos- manarch-mawr and Rhos-manarch-ganol, and by the cottages of Pen-rallt. Further on we find a strip of dark Ordovician shale between this belt and the Parys Mountain. The boundary on the other side of the belt is obscure, but black Ordovician shale is seen quite close to the granite in Nebo Street. Tracing the southern fault inland, it is not so clear, but the beds are disturbed and broken, and no conglomerate is seen. ‘There is thus only left the boundary between Plas Ucha and Nebo, which is in a direction at right angles to the other’ boundaries, and is not therefore their natural continuation, and need not be faulted. It is along this line that the quarries quoted by Dr. Callaway, at Nebo, are worked in the basal Ordovician conglomerate, which 1s immediately followed * Quart, Journ. Geol. Soc. vol. xxxviii. MONIAN SYSTEM OF ROCKS, 525 by the black shale. There cannot now be the slightest question as to the character and age of this conglomerate. Unfortunately the line is so much broken by small faults that it is unfitted to lead to any stratigraphical conclusions, Still the basal conglomerate is there; on one side is a large area of Ordovician, on the other a large area of another group of rocks. Thus, in horizontal dis- tribution, the conglomerate is intermediate between the two, and it seems impossible that the second group of rocks should be younger than it. Thus there is reasonable ground for treating this district as not “altered Silurian,” but as Pre-Ordovician ; and if Pre-Ordo- yvician, from what we have elsewhere seen, then Pre-Cambrian. But there are still some difficulties on this head to be overcome. If we draw a line from Nebo quarries in the direction of the general faulting, we find the conglomerate continued at least a little way along it; and where it emerges on Porth Lygan, there are strewed on the shore immense blocks of the same kind of conglomerate, hiding, with other blocks, the solid rocks below. At this spot, too, Sir A, Ramsay states that there are 60 or 70 feet of black Ordo- vician shales, not now exposed, and the valley, which here descends to the shore, indicates soft rocks. There would thus appear to be a band of Ordovician running through the heart of the district, and we cannot wonder that Prof. Ramsay considered the granite intrusive in its midst. But, as we shall see, the district is not all granite, and such a band would not correspond with the lie of the other rocks. We may therefore better account for this strip by another parallel fault to bound it on the east. But, again, there is marked on the Survey map a tongue of granite running across the fault on the northern side and into the Ordovician shales. If this were correct, the granite, at least, would have to be late Ordovician in date. I have therefore examined the ground with care. The supposed tongue lies entirely in a large grass-field, and very little live rock can be found. The only knob in which anything is seen consists of a gritty band of the Ordovician, and not of granite. I conceive there- fore that this tongue is simply an error, which would be of slight importance if the granite had been proved Ordovician elsewhere, DescRIPtTion oF THE Rocxs.—At first sight the rocks of this district seem entirely different from anything we have seen before; but this is because the examination naturally begins on the sea-coast, where their true character is revealed by weathering. But, seen inland, we do not lose all clue. At Dryslwyn, south of Parys Mountain, and not much more than a mile from Pen-lon, the aspect of the rock is that of a pelite; but when examined microscopically it is seen to consist of tolerably clean foliated quartz and felspar with mica in parallel lines ; in other words, it corresponds to the ordinary grey gneiss, differing only in not being quite so clean. Then by the outer rows of evaporating pools in the low ground we find granite passing into mica-schist, reminding one of the district south of Traeth Dulas; and the low parallel mounds yield a dark foliated rock, which is micaceous diorite, only differing in the 526 REV. J. F. BLAKE ON THE presence of mica from the coarser varieties of Craig-yr-allor or Holland Arms. This does not appear to reach the coast, nor even to cross the Nebo road. In some parts the felspar is so separated from the darker ingredients in patches as to give the rock the aspect of an impure granite; and the granite itself, at its purest in this immediate neighbourhood, only differs in having little or no hornblende. Thus, as noted by Mr. Allport, quoted by Dr. Callaway, there is a passage from one into the other which we have nowhere else seen. There is also here a quantity of indurated rock in which no mica is developed. None of this is ordinary or metamorphosed sedimentary material except, perhaps, the grey gneiss of Dryslwyn. The type of granite in the main mass to the north of Nebo is of a different character. It contains no ferruginous ingredient, and its mica is white. It thus corresponds to the granite of the district south of Traeth Dulas; but when well preserved it is seen to be much coarser in the grain, and its felspars are brownish in tint, giving the rock a peculiar colour. Moreover, where the rock is most massive, mica appears to be absent. This granite is represented in the map as running in several separate tongues; but these tongues must not be taken as actually representing where the granite is, which would be impossible. Thus, in a quarry near Pant-y-bwlet, visited in company with Prof. Green (see fig. 25), the Fig. 25.—Quarry near Pant-y-bwlet. = == | Chloriie Schists Jont) ee ° ine ritoid i a | ae eee I y Bee oy Map of the distribution of ai Sega) Wc | Grey Oneuss, pe et ie S THE ROCKS OF & Mica Schusts. 23) Quartzule oC ey, Godowen 1m THE Monian SYSTEM 5 SS Ties Dinas Lng Le ass Horny te Carnarvon AND AsSociaTED Rocks “4 Cramtic Type SSaDoritic Wpe | _ J Quart Knobs i ove : . Landdyyn Is e -s is Spite irs an the Lleyn Peninsula. BU Serpentine re) mn Pulte SS LJ Scaled 1 Mi Ch & Gabbro bE a Diabase NUM rerntexst es se ct ad Mies Fred™ Dangecheld. ith, 22 Redford S Covent Garde fenton & 88 ec? MONIAN SYSTEM OF RUCKS, 547 interpretation of the country. The rocks of Howth were deter- mined as Cambrian, mainly because they lie unconformably below Lower Silurians (or Ordovicians). Prof. Bonney would like to have had stronger evidence as to the interbedding of schists and slates; he thought that the phenomena might be explained by intense local pressure, whereby a “ slatified schist,” so to say, was produced. ‘This was the case elsewhere in Anglesey and in the Alps. Professor Blake had made confusion out of his explanation of the serpentine-calcite rock in Holyhead Island. What he did say in his published paper was that after great crushing, the downward percolation from the once overlying Carboniferous Limestone had helped to cement the serpentine breccias in the Roscolyn district. A similar thing might be observed in the Apennines, with this difference, that there the limestone had not been removed by denudation. ‘The hilleflinta of the Porth-Nobla district was crushed-up rock of gneissic origin. He thought there was no necessity for the establishment of the Monian system, and endorsed all the President had said on this subject. The Anglesey crystalline rocks were so much modified by subsequent earth-move- ments that they were generally not very well suited for types. The AvrHor, in reply, thanked the Society for the reception accor- ded to his paper. He admitted the force of the President’s remarks, but said that all systems must be based on the careful examination of a single area. He had aimed at simplifying matters by absorbing a number of smaller systems. He instanced the rocks of the Long- mynd and some in Belgium as members of the Upper Monian, and the Wrekin area and St. David’s as containing Middle Monian rocks, and suggested that the rocks of the Lizard might be Lower Monian. He thought that Dr. Hicks’s criticisms did not leave much to reply to; on many points they were agreed, except as to the intrusive nature of the granite. He considered that the specimen exhibited, which contained no diorite, satisfied Dr. Hicks’s demand. He was glad to hear from Prof. Hull the explanation of the Howth beds having been called Cambrian, because it would be equally applicable to prove them Monian. ‘To Prof. Bonney he replied, with reference to the change from slates to schists, that no amount of folding could have done this, since the beds where it occurs are not folded at all. There was plenty of crushed schist in the neighbour- hood, but not of that character. Some hiilleflintas might be of gneissic origin, but not all; very fine fragmentary matter may be produced by the action of volcanos as well as by crushing. He stated that his conclusions had been modified time after time by further knowledge of these Anglesey rocks, and he was now con- vinced that they really constitute one great system. 548 DR. F. H. HATCH ON THE SPHEROID-BEARING 393. On the SPHEROID-BEARING Granite of MuttacHpere, Co. Donneat. By Freperick H. Harcu, Ph.D., F.G.S., of the Geological Survey. (Read May 23, 1888.) [Communicated by permission of the Director-General of the Geological Survey. | [Prats XIV.] On returning from a recent inspection of the field-work of the Geological Survey in Ireland, Prof. A. Geikie brought with him some remarkable specimens of spheroidal concretions, which, on account of their interesting structure, he thought worthy of detailed examination and description. For this purpose they were entrusted to me, and the present paper records my observations. These bodies were found by Mr. J. R. Kilroe, of the Geological Survey of Ireland, in granite at Mullaghderg, Dungloe, Co. Donegal. According to Mr. Kilroe, they occur in a mass, measuring 5 or 6 cubic yards, which lies in coarse granite. It consists “ of concre- tionary balls, varying in size up to 6 inches in diameter. The balls are usually flattened and lie almost contiguously, the interstices being filled by granite, which is similar in character to, thongh much finer-grained than, that surrounding the entire mass.” In a letter I have since received from Mr. Kilroe he informs me that dykes are numerous in the locality where the spheroids occur. One of these passes quite close to the mass containing the con- cretions ; but since the latter are confined to a small space and do not follow the dyke, I see no reason for connecting their formation with its intrusion *. The Normal Granite.—Of the granite referred to above, Mr. Kilroe was kind enough to furnish me with specimens. It is a coarse-grained rock, varying in colour from a pale flesh- tint to a reddish brown. ‘The specimens in my possession have a somewhat loose and crumbly texture, which, if general, would * T have examined a section of the rock from this dyke. It is a porphyrite, consisting mainly of a microcrystalline aggregate of felspar and quartz, the latter being subordinate. The sections of the felspar are bounded partly by rectilinear, partly by irregular contours. Some of the grains are striated ; others, on the other hand, show no trace of twinning. It is therefore not improbable that orthoclase is associated with the plagioclase. The quartz- grains may be distinguished from the felspars by their greater pellucidity, their more irregular shape, and by the fact that occasionally a uniaxial inter- ference-figure may be obtained. ‘Traces of micropegmatite are not unfrequent. Imbedded in this ground-mass are isolated porphyritic crystals of striated felspar, characterized by a marked zonal structure. The extinction-angles reach a rather high value; and from analogy with other porphyrites of this character, the felspar is probably labradorite. Scattered somewhat sparingly through the section are ragged blades and plates of a green small-angled mica. This mineral shows strong pleochroism:—a=pale yellow; 6 and y=dark olive-green. Associated with the mica are scales of chlorite, grains of epidote and occasionally of sphene, iron-ore in isolated granules, and apatite in slender prisms. : GRANITE OF MULLAGHDERG, CO, DONEGAL, 549 considerably curtail its application as a decorative building-stone. Its essential components are quartz, potash-felspar, soda-lime-felspar, hornblende, and black mica, with sphene as an accessory constituent. Since there is no white mica the rock must be classed with the granitites. It is in fact a sphene-bearing hornblende-granitite. The dominant felspar occurs in irregularly contoured masses, which are sometimes of such considerable dimensions as almost to give the rock a granito-porphyritic structure. The colour of this mineral, which depends on the amount of weathering, determines the prevalent tint of the rock. Reflections from cleaved surfaces show that almost every crystal is made up of the two hemitropic components of a Carlsbad twin. Its specific gravity, determined by means of Sonstadt’s solution and the Westphal’s balance, is 2°57. These are the figures assigned by Tschermak to a felspar of the composition Gr Ab,*. Examined under the microscope, a considerable proportion of this felspar is found to be microcline, presenting, between crossed nicols, the rectangular intersection of spindle-shaped striz characteristic of this mineral. In addition to this structure, suitably directed sections (viz. those in the zone P: M.) show a system of small irregular lamelle of triclinic felspar (albite or oligoclase), inter- calated along the prismatic or macropinacoidal planes, To this intergrowth of orthoclase or microcline with a feispar of the albite- oligoclase series, F. Becke f has given the name of microperthite. Irregular grains of striated felspar (oligoclase) also occur as inclusions in the microcline ; less frequent are lamelle and grains of quartz. ‘This is probably the “quartz dm/filtration” of French geologists. : Felspar presenting no striated structure is also abundant. Such felspar, according to the usual practice, is to be referred to ortho- clase. A. Michel-Lévy + has indeed made it appear likely that orthoclase and microcline are identical, by showing that the optical properties of orthoclase are such as would be expected to result from an intimate intergrowth of microcline-lamelle on the albite- and pericline-types. But the identity has not yet been proved. A curious phenomenon, which has been described and figured by Becke §, is also well shown by an isolated section of this felspar. This section is nearly parallel to the orthopinacoid, since it presents the emergence of an axis of elasticity (a), and contains two sets of fine, sharply marked cleavage-lines, crossing one another at an angle of 106°. These are the cleavages of P and M, the divergence from rectangularity being caused by the position of the section. An * Tschermak, “‘ Die Feldspath-gruppe,” Sitzungsber. der k. Akad. der Wissens. Wien, Bd. 1. Abth. 1 (1864), p. 579. “Or” stands for one molecule of orthoclase (K,O, Al,O, (SiO,),), and “Ab” for one molecule of albite (Na,O, Al,O, (SiO,),). + “Die Gneissformation des niederdsterreichischen Waldviertels,” Tscher- mak’s Min. und Petr. Mitth., Bd. iv. 1882. t “Identité probable du microcline et de l’orthose,”’ Bull. de la Soe. Minéralog. de Fr. (1879), tome ii. p. 185. § Loe. cit. p. 199. 550 soDR. F. H. HATCH ON THE SPHEROID-BEARING examination in convergent polarized light shows that the trace of the optic axial plane is coincident with one of the cleavages (P). Parallel to the cleavage-lines are two sets of straight, strongly refractive markings, reticulated as in fig. 1. These lines are dark F ig. 1.—Section of Felspar showing the cleavages P and M and the markings parallel thereto. in transmitted, and white in reflected light. They do not extin- guish with the main mass of the felspar, the latter becoming dark between crossed nicols at an angle of 5°, the former at one of 14° with the basal cleavage-lines. As Becke has already pointed out, this lineation has nothing to do with microperthitic structure. It may perhaps be due to a deposit of secondary crystalline material along the cleavage-planes. The decomposition of the orthoclase shows itself in the formation of cumulous aggregates of minute flakes of a brightly polarizing substance—muscovite or kaolin. The oligoclase occurs only in isolated crystals of rather small dimensions ; in colour it iswhite. Easily recognized by its sharply defined twin-lineation, its place in the soda-lime-series is at once given by its small-angled extinction. Its specific gravity is 2°648. These figures fall within the limits assigned by Tschermak and Max Schuster * to oligoclase, viz., 2°645, 2-671. The quartz, distinguishable by its pellucidity and its numerous liquid-inclusions, belongs to two phases of crystallization, since it occurs both in large allotriomorphic masses and as infillings of the small irregularly shaped interspaces between the larger grains. This younger quartz, representing the residual magma of the rock, is also found sending tongue-like processes into the quartz of earlier origin, thus affording ocular demonstration of their separation in point of time. The hornblende and mica are scarcely to be separated with the unaided eye. They are generally aggregated in little patches of black shining scales. Isolated and examined in convergent polarized * «“ Ueber die optische Orientirung der Plagioclase,” Tschermak’s Min. und Petr. Mitth., Bd. iii. 1881, p. 153. GRANITE OF MULLAGHDERG, CO. DONEGAL, Dol light, the mica presents an interference-figure which is practically uniaxial. It belongs accordingly to the biotite-group. Its absorp- tion is exceedingly strong, viz., a=pale yellow; 6 and y=black. The hornblende occurs either alone or associated with the mica or with a small quantity of magnetic iron-ore. Its maximum extinction-angle, measured to the vertical axis in the prismatic zone, is 17°. The pleochroism is marked, viz.: u=pale yellow, Fig. 2.—A twinned Crystal of Hornblende, showing the extinction- angles of the two halves, measured to the trace of the plane of twinning («2 P co). =deep brownish green, y=deep olive-green. Twinned crystals occur occasionally, the twinning-plane being 0 Po (100). Fig. 2 shows such a twin. Traces of a cleavage parallel to a positive orthodome will also be observed in this figure. A cleavage parallel to - sane P «0 (101) has been observed in hornblende by C. Whitman ross *, Produced probably by the hydration of the mica, are scales of a bright green chlorite. Sphene occurs in large but isolated grains enclosing granules of magnetite and, in one case, a well-contoured crystal of oligoclase. Occurring as a secondary product in the altered felspar are granules of epidote. Of all these minerals the oligoclase shows perhaps the greatest tendency to the assumption of crystalline contours. It is, however, nearly equalled in this respect by the hornblende. This, combined with the fact of its occurrence as an inclusion in sphene, should sa Studien iiber bretonische Gesteine,” Min. und Petr. Mitth. iii. (1881), p. 386. 552 DR. F. H. HATCH ON THE SPHEROID-BEARING place oligoclase high up in the order of consolidation of minerals in granite. The matrix intervening between the balls differs but little from the granite just described. Its texture is a little finer, and it con- tains perhaps a somewhat greater proportion of oligoclase. The Spheroids.—The most perfect of the concretionary bodies submitted to me for examination is a somewhat flattened spheroid, the greatest diameter of which is about four inches, and the smallest three. A thin layer of reddish felspar, with which abundant glistening plates of a dark-coloured mica are associated, is the only remnant of the enveloping matrix remaining attached to the peri- pheral surface. This felspar is orthoclase of specific gravity 2°571, which, it will be seen, is almost identical with that of the orthoclase in the surrounding granite. The mica, too, presents optical pro- perties similar to those of the mineral described above. In order to investigate its internal structure, the spheroid was cut through the centre, and one of the halves polished. Sections * showing both central and marginal portions of this and other spheroids were also prepared. Two distinct parts were then clearly to be made out :—a pink felspathic nucleus, and a dark-coloured peripheral shell. Measured in section, the diameter of the nucleus is about 14 inch; while the width of the external zonal portion is about 1 inch. The outer periphery of the spheroid is regular and sharply defined, being marked off from the granitic matrix in which it is imbedded by the dark colour of the marginal portion. A closer examination discloses the fact that this dark colour is not, as at first sight appears, uniformly diffused ; for the main mass is found to consist of a colourless and transparent mineral, enclosing innumerable granules of a black, opaque substance, with metallic lustre. Nor are the granules with- out order in their distribution, being disposed in more or less definite rings so as to produce a marked concentric structure (see fig. 1, Pl XEN): The boundary of the nucleus, on the other hand, is irregular and wanting in sharpness. This is caused by an almost imperceptible transition (due to a gradual increase in the number of black granules) of the nucleus into the outer zonal portion. Submitted to microscopic examination, the nucleus is found to consist of an irregular hypidiomorphic granular aggregate, chiefly of triclinic felspar, presenting well-defined twin-striation often on both albite- and pericline-types. This twinning is extremely sporadic in its occurrence, one and the same grain often showing no trace of striation in one place, while in another the twinning is well marked. Though occasionally clear and fresh, the felspar has often suffered from kaolinization, turbid patches being developed in consequence. Such alteration generally follows the cleavage-cracks, but in some * T have great pleasure in expressing my admiration of the way in which these sections have been prepared by Mr. J. Young in the laboratory of the Geological Survey at Edinburgh. Though of unusually large size, ie are of sufficient thinness to show the minutest structural details. GRANITE OF MULLAGHDERG, CO. DONEGAL. 553 cases prefers the twinning-planes. A few grains of unstriated felspar are possibly orthoclase. Wedged in between the felspar-masses, and evidently of later consolidation, is allotriomorphic quartz with liquid-inclusions. Accessory grains of sphene are also peculiar to this part of the spheroid. As the outer zone is approached, granules of the black opaque mineral and plates of brown mica become more and more frequent ; at the same time the quartz gradually ceases to occur. The bulk of this portion of the spheroid consists also of plagioclase felspar, differing from that of the nucleus only in the mode of arrangement. For the most part, it appears, under the microscope, in wedge-shaped sections, the longer sides of which converge towards the centre. Of the remaining two sides, the broader base forms part of the external periphery, while the other end terminates irregularly or unites with the felspar of the nucleus. This radial orientation of the felspar is distinctly indicated in certain parts of the section by an approximate coincidence of the twin-striz (when viewed between crossed nicols, or when marked by an alternation of turbid and clear lamella) with the direction of the radii of the spheroid (see fig. 4, Pl. XIV.). Such cuneate sections must represent rudely conical or pyramidal masses of felspar which radiate from the nucleus, their broad bases forming part of the external surface of the spheroid. In the polished specimen the sections of the felspar-cones are easily recognizable by the unaided eye. They are distinguished from the intervening material by a faint chatoyant lustre, apparently caused by reflection from internal surfaces. When the conical masses are contiguous, the line of junction appears, in thin section, as a series of steps, which are well brought out by the contrast of the different polarization-tints. Cross-twinning, on the albite- and pericline-types, is not unfrequent, the more persistent striation being, almost with- out exception, in the radial direction. Many of the wedge-shaped masses are, however, entirely free from polysynthetic twinning. Scattered plentifully through the sections are grains of the opaque mineral. These are of elongated form, being often 10 or 12 times as long as broad, and show, here and there, octahedral terminations. Disposed invariably with their long axes in the radial direction, they appear, at first sight, distributed irregularly over the section. A nearer examination, however, discloses the fact that, in more than one instance, they are ranged, at equal distances from the centre, side by side so as to produce the concentric marking referred to above (see figs. 1,3, Pl. XIV.). This phenomenon clearly indicates simultaneous separation of the opaque granules in concentric zones of growth, the latter evidently proceeding from the central portion outwards. More sparingly present are small plates of the brown mica. This mineral shows strong absorption, and, since it possesses an extremely small optic angle, may be classed with the biotites. Still less frequent are scales of a green chlorite-like substance, resulting, most likely, from the alteration of the mica. An isolated flake of colourless muscovite was also observed. oo4 DR. F. H. HATCH ON THE SPHEROID-BEARING In order to determine the nature of the felspar and of the black opaque mineral, a portion of the spheroid was detached and, after being freed from its outer coating of orthoclase, crushed in a steel mortar. From the powder small fragments of about 1 cubic millim. were sifted out, and of these a few selected which were as free as possible from the opaque inclusions. Tested for their flame-reactions by Szabo’s method, these fragments gave results indicating a lime- soda-felspar of intermediate composition. The fusibility, on Szabo’s scale, is 4. The fragments were now further crushed until the whole powder was sufficiently fine-grained to pass through a piece of fine cambrie, stretched across the mouth of a beaker to serve as a sieve. On going over the powder carefully with a small bar-magnet, the black opaque granules were easily removed, and were found to be com- pletely soluble in hot hydrochloric acid. These are properties of magnetic iron-ore. The total weight of the powder was 3-07 grm., that of the magnetite removed *37 grm., or 121 °/.. The remaining powder was then introduced into a Sonstadt’s solu- tion of such strength that in it calcite (sp. gr. 2°715) just remained suspended. On standing, a dark powder separated, and was removed. This, examined under the microscope, was found to con- - sist mainly of biotite, but mixed with fragments of felspar (rendered specifically heavier by minute inclusions of magnetite) and a small quantity of isolated magnetite. The solution was then carefully diluted until the remaining powder (felspar) appeared neither to sink nor to rise. The specific gravity of this solution, taken at 15° C. by means of a Westphal’s balance, was 2°649. This is almost identical with the result obtained for the specific gravity of the plagioclase of the surrounding granite (vide ut supra). In a solution in which orthoclase (of sp. g. 2°571) floated, the whole powder sank to the bottom, proving conclusively that no orthoclase is present in the zonal portion of the spheroid. A chemical analysis of this powder gave the following results :— <0 ap etamee es Sine Ua aaa. 60-99 Al, 0, (with a little Fe,O,) 25°56 a Ce Se Arkin SecA 4:88 NAOT ora. eens ee ae 773 Loss" 47S mitIOR oo en Sane 84 100-00 * By difference. This agrees very nearly with the theoretical composition of an o:igoclase of the formula Ab An: 7, To sum up shortly these results, we find that the spheroids con- sist of two parts :—a pinkish central portion (the nucleus) and a t Oligoclase of the formula Ab, An, has the following composition :— S1,0= 619; Al,O,=242; CaO= 53; Na,O=87. Tschermak, /. ¢. GRANITE OF MULLAGHDERG, CO. DONEGAL. 555 broad dark-coloured peripheral shell. They are evidently more basic than the surrounding granite; while of the spheroids them- selves the marginal portion is more basic than the nucleus, the latter consisting principally of triclinic felspar together with a little quartz and possibly orthoclase, the former of oligoclase with abun- dant included plates of biotite and over 12 °/, of magnetic iron-ore. The felspar of the zonal portion is disposed radially, the iron-ore radially and concentrically, while no fixed law appears to govern the distribution of the mica. The concentric accumulation of the magnetite may be compared to the zonal inclusion of foreign minerals in leucite or in the felspars of audesitic rocks. Literature.—Concretionary bodies have long been known to occur in granite; but these, though often of spheroidal shape, have gene- rally been described as destitute of radial structure. A concentrically laminated structure, frequently only rendered visible by weathering, is, however, not uncommon. The first mention I have been able to find of such bodies is in Leopold v. Buch’s ‘ Geognostische Beobachtungen auf Reisen durch Deutschland und Italien’*. On p. 16 he describes, as occurring in an intrusive granite of the Riesengebirge (‘‘ Felsen des Kynasts ” near Warmbrunn, Silesia), balls of a very fine-grained granitic material, which towards the exterior are richer in mica than in the central portion. Gustav Roset, in 1842, gave a more detailed de- scription of these bodies. His specimens were derived from Schwarz- bach and the Kynast. He describes balls of 6 inches diameter. The central portion of these is formed by one or more twinned crystals of orthoclase, around which lies a narrow zone of albite and mica. Carious concretionary spheroids in the granite of Chanteloube (Département de la Haute-Vienne) are described by Alluaud +. The dimensions of these bodies are from 50 em. to 1-2 metres. They consist essentially of a nucleus of orthoclase, surrounded by a finely granular aggregate of quartz and felspar, the quartz gradually ‘diminishing in quantity towards the periphery. Charpentier §, Collomb ||, Jokély 4], and von Andrian ** mention similar bodies. Zirkel t+ describes, in the granite of Clark’s Peak, Medicine Bow Range, U.S., small aggregates of granular magnetite surrounded by a fine-grained zone of quartz, felspar, and muscovite. Not unfrequently the concretions consist, for the most. part, of = Vol i. (1802). t Poggend. Ann. vol. lvi. 1842, p. 624; and J. Roth, Erlauterungen zu der geognost. Karte vom niederschles. Geb. &c. 1867, p. 63. t Bull. de la Soc. géol. de Fr. (2), vii. 1850, p. 230. § ‘Hssai sur la constitution géognostique des Pyrenées,’ 1823, p. 132. || Bull. de la Soe. géol. de France (2), vii. 1850, p. 297. “ Geoenost. Verhaltnisse in einem Theile des mittleren Bohmens,” Jahrb. k.-k. geol. Reichsanst. 1855, p. 375. ** « Beitrage zur Geologie des Kaurimer und Taborer Kreises in Bohmen,” Jahrb. k.-k. geol. Reichsanst. 1863, p. 166. tt Microscopical Petrography of the 4Uth Parallel, 1876, p. 53. 556 DR. F. H. HATCH ON THE SPHEROID-BEARING concentrically arranged scales of biotite or dark hornblende. This, for instance, is the case in the Pudding-granite of Craftsbury, Ver- mont *, where, in addition to the biotite, they contain small quanti- ties of muscovite, quartz, felspar, and calcite f. In an interesting paper read before this Society in 1879 the late Mr. J. A. Phillips t gave the results of a series of careful investiga- tions into the nature of the dark-coloured, so-called ‘‘ concretionary patches.” His conclusions show that these bodies differ from the enclosing rock, first, by containing a larger proportion of dark mica and hornblende ; secondly, by their greater basicity, the orthoclase of the matrix being replaced by plagioclase in the concretion, or by the latter being poorer in quartz than the matrix. Although several of the concretions described by this author are spheroidal or ovoidal in shape, they present neither radial nor concentric structure. Vom Rath § has mentioned the occurrence of flattened spheroids, of 6-8 centim. diameter, in the hornblende-granitite of Slitmossa, Kirchspiel Jaireda, Kalmalen, in Sweden. These bodies have a gra- nular nucleus, composed of the granite-forming minerals, and a narrow peripheral zone, showing radiate structure. The latter is further subdivided into an inner felspathic layer and an outer darker shell rich in biotite and hornblende. The same author || has de- scribed similar bodies in the granite of Fonni, in Sardinia. They were originally discovered by Prof. Lovisato €[, while on a visit to the island. The balls occur, as at Mullaghderg, packed together in a small space, scarcely exceeding two cubic metres in extent. The spheroids from Fonni have quite recently been submitted to a careful examination by Fouqué **; and his description of them shows that they exhibit several striking points of resemblance to the Irish specimens. Like the latter they consist of two parts :—(1) a nucleus, similar in composition to the surrounding rock; (2) a marginal portion compused of plagioclase felspar (albite) and biotite, the felspar being in divergent rays, and the mica in concentric zones, in which the individual plates are disposed in a tangential manner with respect to the nucleus T7. * Report on the Geology of Vermont, by Ed. Hitchcock and others, vol. ii. (1861), pp. 564, 721. Also, G. W. Hawes, Concordia, 1878, pp. 190-204. t M. K. de Kroustschoff, Bull. de la Soc. Minéral. de Fr., vol. viii (1885), . 188. : t Quart. Journ. Geol. Soc. vol. xxxyv. 1879, p. 1. § Sitzungsber. der niederrhein. Ges., Dec. 1874, p. 206. See also a paper by N. O. Holst and F. Erichstadt—Geol. Foren. Stockh. Forhandl. No. 86. Bd. vii. Haft. 2 (1884), p. 134—where the Slatmossa rock is incorrectly desig- nated Klotdiorit. || Sitzungsber. der niederrhein. Ges., Juni 1885, p. 201. € lbid., Juni 1883, p. 181. ** “Sur les nodules de la Granulite de Ghistorrai prés Fonni (Sardaigne),” Bull. de la Soc. Minéral. de France, tome x. (1887), pp. 57-63. tt Prof. Judd has kindly lent me, for comparison, a specimen of these spheroids. It is considerably flattened: the largest diameter is about 43 inches, the shortest not more than 2 inches. The zonal portion, which is about 1 inch in width, contains dark mica, but only in the outermost layers, the remainder being composed of pure felspar in divergent rays. GRANITE OF MULLAGHDERG, CO. DONEGAL. 557 An interesting variety of spheroid has lately been discovered in the Stockholm granite of the Scandinavian peninsula, and has been the subject of a searching examination and detailed description by W. C. Broégger and H. Biackstrom*. The spheroids occur in several distinct masses in a granitite consisting of orthoclase (in part microcline), oligoclase, quartz, and dark mica. ach ballis made up of a dark nucleus and an outer light-coloured zone. The former is composed of the same minerals as the surrounding rock, the latter principally of felspar (plagioclase, orthoclase, and microcline) to- gether with quartz. Dark minerals (mica, &c.) are entirely absent from this portion of the spheroid. The texture of the outer zone is granular, but finer-grained than the nucleus or the surrounding granite. A radially divergent structure was observed by Brogger in one instance only. The nucleus passes by imperceptible grada- tions into the peripheral portion; the latter, however, is sharply separated from the granite. No fixed proportion exists between inner kernel and outer zone. In some few cases the granitic material of the nucleus was found to be replaced by a single large individual of felspar (microcline), as in the spheroids described by G. Rose (cited above). Conclusions.—The concretionary bodies, briefly described in the above résumé, may be classed as follows :— I. Local accumulations of dark mica, hornblende, and a little triclinic felspar, generally of irregular shape, but sometimes rudely spheroidal. These are the “‘ concretionary patches ” of Phillips. II. Spheroids composed of quartz, felspar, and mica or hornblende (2. e. the same minerals that compose the surrounding rock) in gra- nular aggregation. These bodies possess an inner kernel and an outer zone, the latter sometimes exhibiting concentric structure. Brogger fT subdivides them into (1) those having a nucleus relatively rich in dark minerals (biotite, hornblende, &c.) with a peripheral portion relatively poor in, or free from, dark minerals; (2) those with a peripheral zone rich in dark minerals. The whole group may per- haps be classed with Vogelsang’s granospherites ft. III. Spheroidal aggregations of triclinic felspar with dark mica, hornblende, or magnetite around a central nucleus. This variety is characterized by the possession of both radial and concentric structure, and may be referred to the belonospherites of Vogelsang§. ‘To this group belong the spheroids from Mullaghderg, as also those from Fonni. The nucleus of the spheroids is extremely variable, both as regards Size and composition. It may consist of a portion of normally con- * “Om forekomsten af ‘klotgranit’ i Vasastaden, Stockholm,” Geol. Foren. Stockh. Forhandl. no. 110, Bd. ix. Haft. 5, p. 307. I am indebted to Prof. Térnebohm for directing my attention to this impor- tant paper, as also for kindly supplying me with specimens, for the purpose of comparison, from both the Swedish localities (Slatmossa and Vasastaden), T Lec. cit. p..351. { ‘ Die Krystalliten,’ Bonn, 1885, p. 134. § Loe. cit. 558 DR. F. H. HATCH ON THE SPHEROID-BEARING stituted granite, or of one or more crystals of orthoclase ; or, again, of an aggregate of plagioclase grains. Sometimes it is an accumu- lation of granules of magnetite * ; sometimes one of the dark mica- ceous nodules of group It. As the concretion forms round the original nodule, its irregularities are gradually equalized: so that the spheroidal or ellipsoidal character is soon acquired. With regard to the genesis of the spheroids, there can be little doubt that they have been formed by concretion during the con- solidation of the granite-magma; they must, consequently, be re- garded as an example of zonal and, in the case of the belonosphe- rites, radial crystallization around an earlier-formed nucleus. As one of the conditions for the development of such a crystallization a quiescent condition seems @ priorz to be essential. Differential movements in the granite-magma, which have resulted in a consider- able distortion of the spheroids, must in some cases, however, have taken place before the final consolidation of the rock+. We have here an instance of fluxion-structure, which, in granite, is undoubt- edly a rare phenomenon. Chemical composition appears also to be a determining factor; for in at least two of the above classes the concretions are more basic than the enclosing granite, the intervening material, on the other hand, being of normal constitution. A defi- ciency in silica would thus seem to favour the development of spheroids in granite. Whether the occurrence of basic patches be due to the absorption of pre-existing basic material or to some process of segre- gation, must remain, for the present, an open question. Brodgger §, on the other hand, hazards the conjecture that the spheroidal structure is preferably developed along the marginal portion of the granite area, 2. €. in those portions where the magma first consolidates. This, he says, would be analogous to the occurrence of granophyric or porphyritic structure in the marginal portions or in the apophyses of granite or syenite. The balance of evidence however, scarcely seems to favour this hypothesis. It certainly will not explain, for example, the occurrence at Mullaghderg, Co. Donegal ; for this locality lies right in the midst of the granite-area ||. With reference to the formation of these remarkable bodies, perhaps it would be not unprofitable to recall to mind Vogelsang’s explanation of similar phenomena, given in his admirable paper describing the concretionary balls of the Kugeldzorit ( Napoleonite) and Kugelporphyr of Corsica §] :—‘‘ When a molten magma consoli- dates, an irregular (ungleichmdssig) cooling may produce greater contraction of the mass at certain points; and this may lead, later on, to a spheroidal separation. If this condition is arrived at after * Zirkel, /.c. t Vom Rath, /. «. t Brogger, J. ¢. pp. 323, 327. § Loe. cit. p, 344. || Mr. Kilroe writes :—‘‘ The mass of spheroidal concretions does not occur at or near the margin of the granitic area. The point is almost equidistant from quartzite, occurring in mass some miles away on either side, through which the granite has been intruded. Small isolated masses of quartzite and schist are included in the granite in various places, but none near the special point referred to.” ‘ € Sitzungsber. d. niederrhein. Ges. 1862, xix. p. 185. GRANITE OF MULLAGHDERG, CO. DONEGAL. 559 the point of consolidation of the several minerals has been passed, and, therefore, after their separation is complete, we get, indeed, a concentrically laminated body, but one without a definite arrange- ment of the constituents : this is the well-known spheroidal structure of many eruptive rocks. If, on the other hand, the tendency to form spheroids is developed during the period in which a differentia- tion of the magma into the various minerals can still take place, the latter will naturally undergo a definite arrangement with regard to the central point.” The first case, as pointed out by Vogelsang, offers a rational ex- planation of that form of spheroidal structure in which there is no definite arrangement of the constituents *. The latter case describes what most probably took place during the formation of spheroids with zonal or radial structure. EXPLANATION OF PLATE XIV. Fig.1. A portion of a spheroid, cut through the centre and polished. It shows the light-coloured nucleus, the dark zonal portion, and a small fey of the granitic matrix attached to the periphery. (Nat. size. 2+. A portion of the nucleus, viewed in thin section under a low power and between crossed nicols. ‘The striated mineral is oligoclase; the interstitial colourless substance, quartz; and the opaque grains, mag- netite. 3. Section through the zonal portion of the spheroid, seen under a low power. The light portions are felspar (oligoclase); the black grains, magnetite. The latter have their long axes in the direction of the radii of the spheroid. The dark line in the zonal portion of fig. 1 traverses here the middle of the field, and is seen to be produced by the approximation of the black grains. 4. Section through the zonal portion of the spheroid, viewed under a low power and between crossed nicols. As in fig. 3, the main mass is oligoclase, and the black grains are magnetite. The felspar is seen to be twinned, the twin-lamelle being orientated in the direction of the radii of the spheroid. Discussion. Mr. Rurtey spoke of the difficulty of doing justice to the immense amount of careful work involved in this paper. The Author had wisely avoided theoretical views, and yet it was tempting to specu- late on the causes which set up crystallization, and to inquire why there was no radial structure in the central portions of the spheroids. Prof. Bonnzy regarded the paper as a very useful piece of work. _ He thought difference of structure proved a discontinuity of some ‘a In connexion with this point, Prof. Bonney’s papers on “ Columnar, Fissile, and Spheroidal Structures” (Q. J. G. 8. xxxii. p. 140) and “On certain rock structures as illustrated by the pitchstones and felsites of Arran” (Geol. Mag. 1877, iv. p. 429) should be consulted. t The microscopic sections are drawn, with the kind assistance of Mr. J. G. Goodchild, F.G.S., of the Geological Survey, from photographs taken by Mr. G. Barrow, F.G.S., of the Geological Survey. Q.3.G.8. No. 175. 2p 560 SPHEROID-BEARING GRANITE OF MULLAGHDERG, CO. DONEGAL. sort. The concentrie concretionary structure is not confined to melted rocks. He referred to certain slates in the Lake District in which such a structure occurs. In the case of these spheroids a molecular movement had taken place, showing that a certain amount of plasticity had been retained in a rock which had never been in a fluid condition. Dr. Hicxs suggested that the proximity of intrusive rocks might have set up some action of this kind by the production of cavities ; that the spheroids may therefore be considered as of secretionary rather than of concretionary origin. Prof. Jupp remarked that this was the first occasion in which both radial and concentric structure had been found in any spheroids 'in granite in the British Islands. The Society was to be congratulated on these specimens having fallen into such good hands, and being so admirably described. He asked if the microperthitic structure occurred in the felspars of the granite, and not in those of the nodules. The AvrHor observed, with regard to the suggestions of Dr. Hicks, that the spheroids occur in a very small compass, and probably bore no relation to the dyke. The minerals were not secondary pro- ducts. Prof. Judd was quite correct in supposing that there was microperthitic structure in the granite, but none in the spheroid. Quart. Journ.Geol. Soc. Vol. XLIV. Pl. XIV. Ant del. FH Wichsel lith. Mintern Bros imp MULLAGHDERG GRANITE. ON THE CAE GWYN CAVE, NORTH WALES. 561 34, On the Can Gwyn Cave, Norra Watzes. By Henry Hicxs, M.D., F.R.S., F.G.S. With a Norse by C. E. Dz Rance, Esq., F.G.S. (Read April 11, 1888.) Tr has been thought advisable by those who have superintended the explorations at the Cae Gwyn Cave that a full account of the re- searches carried on there in the latter part of 1885, and during 1886 and 1887, should be laid before the Society. In a former paper (Quart. Journ. Geol. Soc., Feb. 1886) I gave the main results obtained up to the end of June 1885. The excavations were then entirely under the superintendence of E. Bouverie Luxmoore, Esq., M.A., F.G.S., P. P. Pennant, Esq., M.A., J.P., Edwin Morgan, Esq., J.P. (all of whom reside in the immediate neighbourhood), and myself. I was constantly present at the explorations to the end of June, when we had reached a distance of about 135 feet from the entrance. At this time the Cavern was visited also by Mr. C. E. De Rance, F.G.S. The sandy layer was well marked at this point, and the workmen were requested by us at the time to remove several shovelfuls, which we examined and found to have all the characters of true marine sand. The other deposits occurred in the order in which they had been found elsewhere throughout the cavern. The further researches in that year were superintended by Messrs. Luxmoore, Pennant, and Morgan, and the results were constantly communicated tome. The tunnel was found to be of nearly the same average width and height for about 10 feet further inwards, when it gradu- ally widened into what was then supposed to be achamber. Of the last portion of the cavern explored I stated in my paper (oc. cit. p. 14) : ‘The last chamber reached in this cavern has not been fully ex- amined, and as its roof has partially fallen in, it will have to be shored up before the explorations can be proceeded with in that direction. It is possible that a line of fissure has been reached, but this is not clear yet. The cavern up to this point is a true tunnel- eayern. with well-smoothed roof and sides.” I also mentioned that the bones occurred throughout at the same general horizon, that the bone-earth contained in many places much sandy and gravelly ‘material, many large angular masses of limestone, and also pieces of thick stalagmite and broken stalactites, sometimes lying hori- zontally, but more often tilted, like the bones, at a high angle. Over- lying the bone-earth throughout occurred a considerable thickness of fine laminated clay, which contained no Pleistocene remains or large angular fragments of limestone or stalagmite. In the last twenty feet or so of the tunnel and in the supposed chamber the laminated clay was overlain by layers of sand and gravel. Throughout the supposed chamber the latter attained an average thickness of from 23 to 3 feet. What was supposed to be a broken roof or line of fissure turned out on further exploration to be the line of the limestone 2P 2 562 DR. H. HICKS ON THE cliff over another entrance to the cavern. Before it was known that this so-called chamber was the widening of the cavern towards the new entrance, the following dimensions were sent to me by Mr. Luxmoore :—passage leading to chamber, height 6 feet 6 inches, width 6 feet; supposed chamber, height 9 feet, width 9 feet 6 inches, length 11 feet 3 inches. The deposits in the chamber were an increased thickness of the bone-earth, with imbedded blocks of limestone, as in the passage leading to it and in other parts of the cavern, laminated clay, continuous with that found in the passage, and upon the latter stratified marine sands and gravels. The section, it was stated, was perfectly clear, and all the deposits could be traced right across the so-called chamber. The cavern was visited by Prof. Boyd Dawkins in September, and in a letter he wrote to me on December 11, 1885, the following passage occurs :—‘ I have carefully compared the sand and gravel found in the upper cave (Cae Gwyn), and sand sometimes adherent to the bones, with the glacial sand and gravel which occurs in the valley a little way above, and find that in every particular they agree. I have also compared them with the glacial sands and gravels near Bryn Asaph and find that all three are composed in the main of quartz, quartzites, and Silurian fragments.” Up to this time, and for some months after the work was suspended, the surface of the field re- mained perfectly even, and there were no indications of any sinking of the ground. During the winter months, however, after a heavy fall of snow, some of the materials slipped inwards into the so-called chamber, and the surface of the field over the spot gradually sank. Researches in 1886. For the purpose of continuing the researches in 1886 a grant was obtained from the British Association for the Advancement of Science, and the following Committee was appointed, viz. :—Prof.T. M*Kenny Hughes, Dr. H. Hicks, Dr. H. Woodward, and Messrs. C. B. Lux- moore, P. P. Pennant, and Edwin Morgan. Work was resumed during the last week in May under the super- intendence of Messrs. Luxmoore, Pennant, and Morgan, and I joined them a few days later. It was thought advisable to sink a shaft from the surface of the field, over the depressed part, so as to uncover the supposed chamber. Much to our surprise, after a few days’ work, we found that what had appeared from within the cavern to be a broken roof, or line of fissure, was the abrupt termination of the limestone in a, cliff with an opening below into the cavern. Further researches revealed the fact that this opening was a wide entrance, over 11 feet across and with a height of from 6 to 8 feet. As the shaft was only about five feet across at the bottom at this time, a perfectly clear section of the deposits as they extended into the cavern could be seen, and the particulars now shown in fig. 1 were then carefully noted. Mr. C. E. De Rance, F.G.S., of the Geological Survey, was at that time in the neighbourhood and, at my request, visited the — cavern and kindly assisted us in taking correct measurements in the CAE GWYN CAVE, NORTH WALES. 563 pit. The section was perfectly clear all round, and the various bands were traced continuously across both into the entrance and over the cavern. The measurements were taken from a ladder placed against the vertical face. Fig. 1.—WSection across Shaft, showing the continuation of the Beds over the entrance (June, 1886). (Scale 8 ft. to 1 inch.) Entrance fo Cavern a. Bone-earth. 6. Laminated clay. e, Sand and gravel. d. Clay with boulders and bands of sand and gravel. e. Soil. x Rabbit-burrow. The rabbit-hole shown in fig. 1 indicates the track which extended direct from the cavern to the opposite side of the shaft, in a band of clean marine sand. The pit, which had been carried to a depth of 20 feet, was only 9 feet wide at the top and 5 feet at the bottom. It was subsequently widened, but all the important measurements were taken before this was done. The evidence that the deposits extended continuously into the cavern was so clear, and had been seen by so many observers, that it did not occur to us that anyone could possibly doubt it, otherwise we should most decidedly have allowed one side to remain undisturbed. Feeling, however, that the fact was established beyond the possibility of doubt, we decided to proceed with the examination of the brecciated bone-earth at the bottom, and in doing so we burrowed under the drift-face and by that 564 DR. H. HICKS ON THE means caused some falls to take place, necessitating a further widening of the shaft. I wrote to Prof. Hughes on several occasions in June, telling him the results, and strongly urging him to visit the section. Unfortunately, however, he was not able to do so until the work had been stopped (the grant from the British As- sociation having been exhausted), and most of the section had been shored up with timber for the season, to prevent further falls. We were anxious that as many geologists as possible should visit the section when the surface was fresh and each band distinct, knowing well that a few showers of rain, by washing the soil from above over the face, would blind some of the evidence ; therefore I wrote to a considerable number of geologists, who I felt would be interested in the subject, asking them to visit the cave if possible. Those who saw the section before the ground was sloped back at the top were Mr. De Rance, Dr. Stolterforth, Mr. Shone, and Mr. Morton, and later Prof. Hughes, Prof. Boyd Dawkins, and Mr. Strahan. In the bone-earth at the bottom of the shaft many teeth and bones occurred ; and one tooth of Rhinoceros was found six feet in front of the overhanging roof of the cavern, measured from the outer edge. . On June 28th, when Mr. G. H. Morton, F.G.S., visited the cavern, one of the workmen in digging in the bone-earth turned up in our presence, along with teeth of Hyzna and Reindeer, a well-worked fiint-flake, nearly two inches in length and half an inch wide (fig. 2). Fig. 2.—Flint-flake found under Drift, outside the covered entrance. (Natural size.) It is of a white, porcellaneous appearance, like the implements which we found in the Ffynnon Beuno cave; and at the last meeting of the British Association Mr. Pengelly stated that it resembled some found by him in the lower deposits in Kent’s Cavern. Its position was about 18 inches below the lowest bed of sand, in a vertical face of the section, a little outside the line of the entrance and slightly CAE GWYN CAVE, NORTH WALES. 565 to the south of the opening. It was found near one of the large angular blocks occurring in the bone-earth, but it is an entire mistake to say that it was itself covered by a block. Indeed, nothing could be clearer than the evidence of its position, for we had made a clean face to the section just before, to show how the sandy bands and the laminated clay passed in under the shelving rock, and we were bur- rowing under those bands when the flake was found. Some portions of the rock at the edge of the entrance, which were rather loose, were removed just before ; but the flake was well outside these and in the bone-earth under the deposits in regular sequence in the section. The material in which it was found was exactly like that occurring at this horizon throughout the cavern—a reddish sandy clay, with here and there fragments of stalactites, stalagmites, and angular blocks of limestone. With regard to these angular blocks of lime- stone, it is necessary to say that although they were more numerous outside the entrance than in the cavern, yet similar blocks were constantly met with in the cavern, and even at the entrance to chamber C (see Plan, p. 573) they were so large that they had to be blasted before they could be removed. Nothing could be more incorrect than to say that they formed a barrier at the entrance, giving evidence of a broken side to the cavern. These blocks (except those removed at the sides, which happened to be loose, although in their original position as forming part of the limestone cliff) were all under the laminated clay and the sandy bands, and could not be removed without disturbing the latter deposits at every point examined. The very few blocks found higher in the section were of the character of boulders, and, as could be made out in most cases, had been derived from beds at a different horizon from those at the entrance. At the close of our work in 1886 it was thought advisable to slope the upper portion of the section around the pit, to prevent falls into it during the winter, and the sides were carefully timbered for the lower 12 feet, except at the south angle. Here a few steps were placed to enable the cavern to be reached from that end, and an excavation was made in the field to a depth of about 8 feet on that side leading to the steps. As has already been stated, there was not the slightest sinking of the ground until after the rains and a very heavy fall of snow in the winter; and when the pit was dug out in June, only the part immediately above the central portion of the opening into the cavern was found to have sunk in, leaving the section at each end of the opening perfectly undisturbed. The materials found in sinking the shaft were exactly in the order in which they could be traced in the undisturbed deposits, and it was clear beyond the possibility of doubt that each band had extended right across, before that portion had been depressed during the previous winter, and that the dip of the beds was everywhere away from the cliff face and from the entrance to the cavern. When it is considered what an immense quantity of material had been removed from the cavern before the pit was dug out, it becomes at once evident that it could not have been carried in through 566 DR. H. HICKS ON THE a swallow-hole which had left no evidence whatever of its exist- ence. It must not be forgotten also that the various sediments in the cavern retained their relative sequence throughout ; more- over this sequence continued uninterruptedly from the cavern into the drift section on the outside. I have taken some pains to make a calculation of the amount of material (not taking into considera- tion the blocks of limestone, &c.) which had been removed from the cavern before we reached the new entrance, therefore before any of the deposits in the pit had been touched, and I find that it could not have been less than about 150 cartloads, consisting of gravel, sand, laminated clay, and sandy clay. This must have been conveyed into the cavern before the entrance or entrances were blocked up by the glacial deposits which extended across the valley. That the deposits in the cavern were conveyed in by marine action seems to me, after constantly watching the conditions exhibited throughout the explorations from the commencement, to be beyond the possibility of doubt. The position of the caverns shows that. they could not have been under the influence of any other force (since they had been occupied as dens by the animals) of a sufficiently powerful nature to break up the thick stalagmite floor which had at one time covered over the remains (as was abundantly evident by finding bones attached to the under side of broken pieces) and to have thrown large masses of this, frequently cver a foot in thick- ness, into all positions in the deposits. Large bones were also thrust into fissures and tilted up at all angles. Inthe sand also some frag- ments of marine shells were found, as mentioned in my previous papers. I believe the main entrance to the cavern to have been the one recently discovered under the drift section. It is the widest and most lofty entrance, and there are indications that the one first found, which had been exposed by quarrying operations, must have gradu- ally ended, before the portion in the quarry had been removed, in a fissure, somewhat lke that in which the tunnel on the east side of chamber C (see Plan) has been found to end. The vertical brecciated face, which evidently formed one side of the portion of the cavern removed by quarrying, tends strongly to show that this was not the main entrance, even if there was an opening here into the cavern from the limestone-cliff at the edge of the valley. Researches in 1887. A further grant having been obtained from the British Association, work was resumed on June 6th, under the superintendence of Messrs. Luxmoore, Pennant, Morgan, Morton (who was added to the Com- mittee), and myself, and a few days afterwards we were joined by Prof. Hughes. Mr. Morton stayed at the inn close by, so that he might be constantly present at the excavations. Up to this time no objections had been raised to the notion which we had, as we thought, established beyond the possibility of doubt during the explorations in the previous year, that the deposits from the drift-section passed directly into the cavern, and that the bone- CAE GWYN CAVE, NORTH WALES. 567 earth extended for a considerable distance outwards even to a point 14 feet from the inner wall of the cavern, measured by a line taken directly outwards. That Prof. Hughes was not at that time inclined to contest these points seems evident from the following quotation, taken from his lecture delivered at Chester and reported in the ‘Chester Chronicle,’ November 6, 1886. After referring to the finding of the flint-flake, in the presence of Mr. Morton and myself, in the bone-earth, which he describes as ‘a limestone-breccia con- taining a few bones,” he goes on to say that “a similar deposit ex- tended under the sandy drift with boulders, as far out as the exca- vation was carried. ‘This is conclusive against the drift which rested on it being the undisturbed marine Clwydian drift, as it is quite impossible that the lashing waves on the rock-bound shore exposed to the north-west winds should not have swept such loose débris into the deep fiord below.” His object at that time evidently was, as in some succeeding papers, to show that the drift was not in the position in which it had been deposited, but remamé “ rainwash” like the ‘‘mixed mud and sand and gravel which we find every- where overlying the Clwydian drift crumbling down the hillside.” It is also stated that no shells had been found “in any of these deposits ;” and attention is called to the line of an old fence, as showing how rapidly the deposits are creeping down the hill. Most of these remarks were reproduced in papers in the Geol. Mag., Noyember 1886, and in the Quart. Journ. Geol. Soc., February 1887. As to the statements in regard to the so-called fence, I was greatly puzzled at first to know what they meant, and was inclined to think that they must relate to the old fence (as distinguished from that which we had placed as a boundary to the cavern) along the edge of the valley, against which we had heaped materials obtained from the cavern. When I realized that Prof. Hughes meant the rather steep grassy slope in the field (which, according to a statement in his last paper, carried a fence which was removed about ten years ago), I determined that a cutting should be made across it beyond the point where any material had been thrown down, and our earliest opera- tions this year were directed to that purpose. A cutting, which was carried in a 8.8.W. direction from the shaft at the mouth of the cavern, was now made, varying from 5 to 10 feet in width, the nar- rowest part being at the furthest point from the cavern. In the face exposed in front of the entrance, and for a distance in the cutting from there of about 25 feet, the soil varied in depth from 18 inches to 2 feet, but at the slope it thickened considerably, probably from haying been thrown there in levelling the old fence. Underlying this throughout the whole length of the cutting, and in the part of the field examined beyond this point, a Boulder-clay of a reddish- brown colour was exposed. This Boulder-clay contained numerous erratics and thin seams of sand which were traceable along the whole section. The general dip of the beds was at an angle of about 15° away from the cliff face. On June 10th some fragments of shells were obtained by us out of a band of reddish sandy clay, in the cutting near the shaft, at a depth 568 DR. H. HICKS ON THE of about 7 feet from the surface. Additional fragments and some perfect specimens were discovered on subsequent days, and the fol- lowing list was given in my report to the British Association * :— Ostrea sp., Mytilus sp., Nucula nucleus, Cardium echinatum, C. edule, Cyprina islandica, Astarte borealis, Artemis exoleta, Venus gallina ?, Tellina balthica, Psammobia ferrdensis, Donax ?, Mya truncata, Lit- torina sp., Turritella terebra, Buccinum undatum. Below the Boulder- elay, at a depth of about 9 feet from the surface, there was exposed some sandy gravel and fine banded sand with a total thickness of over 6 feet, and under the latter a well-defined band of finely lami- nated reddish clay. Below the laminated clay the brecciated bone-earth was found to extend as far as the cutting was made in front of the entrance, and also for a distance of 7 feet in a southerly direction from the en- trance. Beyond that point the cutting was made deep enough to reach the sandy gravel under the Boulder-clay, and at different parts - test-holes were sunk still deeper into the gravel and sand. One hole was also sunk in the field in front of the cutting at a distance of over 35 feet from the entrance to the cavern. The deposits here were found to be similar to those in the cutting and in front of the cavern, but the depth of soil over the Boulder-clay was only from 1 foot to 18 inches. A very large number of smoothed and ice-scratched boulders were found, many of considerable size, the majority being fragments of Wenlock shale from the neighbourhood, and Lower Silurian rocks from the Snowdonian area. Amongst them also were fragments of granite, gneiss, quartzites, flint, diorites, basalts, Car- boniferous rocks, &c. ‘To expose the section in front of the entrance down to the limestone-floor, it was found necessary to remove the timber placed there the year before, and the cutting was widened here sufficiently to show a vertical face of undisturbed deposits. The timber supporting the north-east face was at that time allowed to remain. ‘The finding of marine shells in considerable abundance in a continuous band in the section and round the pit proves that the upper portion of the drift in which they were found, resting on the gravel and sand, is, as [ contended in my former papers, the so- ealled Upper Boulder-clay of the Clwyd valley, 2. e. where it has not been re-assorted by the action of fresh water, as in some places about St. Asaph and elsewhere along the borders of the channels carved out by the important rivers Elwy and Clwyd. As these shells are found in the deposits belonging to the Glacial period in many areas, and occur in the high-level sands of Moel Tryfaen (1360 feet) and Macclesfield (1200 feet), it seems to be perfectly clear either that the beds were deposited during a great submergence, which took place in Mid-Glacial time or at the close of the Glacial epoch, or that a great ice-sheet passed over this area subsequent to the occupation of the cavern by the animals and by man. The section was visited by Mr. Tiddeman, F.G.S., and Mr. Clement Reid, F.G.S., both of the Geological Survey, on June 15th, 16th, and 17th, and after a very * The specimens were handed to Mrs. McKenny Hughes, who kindly offered to identify them for us. CAE GWYN: CAVE, NORTH WALES. 569 careful examination they came to the conclusion that tho deposits were correctly classed with those belonging to the Glacial epoch and that they were in position as originally deposited. These gentlemen were also shown the brecciated bone-earth underlying the gravel and sand in front of the entrance and at the south-west end of the pit, 7 feet from the edge of the entrance, and they admitted that it clearly passed under the drift-section. Indeed, some blocks of limestone were removed from the brecciated bone-earth, which caused the overlying sand to fall, thereby exposing at the south-west end, and quite near to the cliff face, a remarkably clear section of stratified sand dipping away from the cavern. ‘The evidence obtained during the excava- tions in June demolished so completely all the objections previously raised that for some time we were fain to believe that no further opposition to our views would be made. In this, however, we were mistaken, for during a visit of a few hours paid to the section in September by General Pitt-Rivers and Dr. John Evans, accompanied by Prof. Hughes, after the section had been exposed to the weather for between two and three months, they noticed that some of the uppermost deposits at one or two points had slipped a little towards the pit; and the idea seemed then to have occurred to them that this was an indication that there must have been a swallow-hole at the point where the shaft was sunk. When I was informed of this, although I knew that it must have been an entirely recent change, I decided to have that portion of the shaft which had not been ex- posed during the June excavations re-examined, so that there may be no doubt whatever as to the conditions behind the timber placed there at the close of the work in 1886. Permission for this to be done was most kindly granted by the owner Mr. Morgan, and, as in former explorations, he, Mr. Luxmoore, and Mr. Pennant assisted in _ the supervision of the work, Prof. Hughes and myself being also present during most of the time. Work was resumed on September 29th. After.the timber and the material which had been thrown behind it to support the face, here 20 feet in depth, had been removed, a section of the deposits, as left by us in our researches in June 1886, was exposed, as well as some of the brecciated bone-earth which had not then been removed from the bottom of the shaft. On making a fresh face to the section at the parts where the recent looping down of the upper deposits had taken place, it was at once seen that this was due to a recent slip, and that the deposits behind and below were entirely unaffected by it. It is hardly necessary again fo mention the fact that all the observers who saw the section when the shaft was first opened state emphatically that there was no looping down to be seen at those points at that time, nor when the upper part of the opening was widened and sloped at the close of the work in 1886. The photographs which were taken by Mr. Helsby, of Den- bigh, on October 1st, show most conclusively that the bone-earth passed directly under the vertical drift-section; and it was proved by explorations subsequent to the day when the photographs were taken that it extended for a considerable distance beyond that 570 DR. H. HICKS ON THE point; indeed, the end of it was not reached when the work was suspended. This fact, even if we had not obtained similar evidence at the south-west end of the cutting at a distance of about 22 feet from the point above referred to, and also at every foot in that length either in front of the entrance or along the cliff-face, it might have been supposed, would alone have been sufficiently con- vincing evidence that the theoretical swallow-hole, or a broken wall of the cavern subsequent to the deposition of the marine deposits, could not possibly have produced such a regular sequence in the deposits from the bone-earth upwards. Moreover, as already stated, all the angular blocks of limestone were buried in the sandy clay which contained the bones, always under the laminated clay and the stratified sand. The photographs show also that the bedded sand belonging to the so-called marine drift has not sunk in towards the theoretical swallow-hole, but that it (as well as the overlying de- posits and the underlying laminated clay) dips everywhere away from the cliff and from the mouth of the cavern. Bones were dis- covered at this time under the drift at the north-east end of the cutting at a point 3 feet outwards from the edge of the overhanging rock, and it is important to remember that the sand passed under and abutted against this edge in an undisturbed condition when the section was reopened this year (fig. 3). Fig. 3.—Section at North-east end of Excavation, as seen October 3, 1887. (Scale 8 feet to 1 inch.) -s, +i ttnen tee OIE . PARK YET DEH a 38 a2 a. Brecciated bone-earth. 6. Laminated clay. c. Sand and gravel. d. Clay with boulders and bands of sand and gravel. é. Soil. x Shell-beds. * Fissure. CAE @WYN CAVE, NORTH WALES. 571 Dr. Geikie visited the cavern at the request of Prof. Hughes and myself on October 10th, Messrs. Hughes, Luxmoore, Morgan, De Rance, and Hilton Price being also present. Unfortunately I was unable to be there. Subsequently Dr. Geikie kindly furnished us with the following report :— ‘The question on which my opinion was asked with reference to this cave was, I understand, the following :—whether the glacial beds lie undisturbed upon the bone-earth at the end of the cave, or whether their present position is due to the fall of the roof or wall of the cave, and their consequent descent upon the cavern floor. Accordingly I visited the cave on the 10th instant and examined the section laid open in the pit that was dug in the glacial deposits. The conclusions I formed may be thus summarized :— ©]. The bone-carth projects beyond the present limits of the cave, but it probably never did so originally; hence I have no doubt that the roof or wall of the cavern has given way. The large masses of limestone lying at the bottom of the pit no doubt repre- sent a portion of the fallen material. “2. These fallen blocks lie on the bone-earth. The material resting upon them has, of course, been removed in the excavation of the pit; but I observed that the block nearest the northern wall of the pit passed under the base of the undisturbed glacial beds. “3. Against the lower part of the face of limestone on the northern side of the pit there is undoubted evidence of slipping, the lower layers of pebbly sand and clay being vertical against the wall of rock. This disturbance, however, I could trace only a few inches outward from the rock-boundary. It does not affect the main mass of glacial deposits, and is referable, I think, to solution of the limestone along its outer surface. The various layers of glacial sands and clays were traced by me continuously across the pit. I could see no evidence that they had ever subsided into a cavity caused by the fall of the limestone into the cavern. “4, From the data presented by the pit-section I would infer that the fall of the roof or wall of the cave took place before the deposition of the glacial deposits, and that during a period of sub- sidence these marine strata were subsequently laid down against the limestone-bank so as to conceal this entrance to the cavern.” Mr. Morton also visited the section, and has kindly sent me the following note giving the results of his observations in June and October :— “Tn June last, during the progress of the excavation in front of the original entrance to Cae Gwyn Cave, I stayed at the inn close by for eleven days, besides visiting it on other occasions before and since. During that time I had, of course, ample opportunity of constantly observing the Boulder-clay, as well as the sand and gravel, and other beds beneath it. From the first time I saw the section I felt convinced that all the beds were strictly in situ. The bone-earth had evidently been disturbed, and a stalagmitic floor broken up, and the fragments, often large blocks, mixed up in it. The laminated clay had evidently been tranquilly deposited over it. Qe = 2a -— SSS Bee > = = +. SSS SS Ea SS i ee Te ee — Soe et = 572 DR. H. HICKS ON THE The sand and gravel were over the laminated clay, but current- bedded as such so-called ‘ Middle sands’ often are. Finally, the Boulder-clay occurred over the sand and gravel, without any evidences of disturbance or rearrangement of any kind. ‘The top of the Boulder-clay formed the surface of a nearly flat field, there being no higher ground near from which débris could have been derived ; and there is no reason for supposing that the surface over the cave was ever deeply covered with clay. The entrance to the cave is in a buried limestone-cliff, from which the Boulder-clay dips, but so gradually that nothing of the nature of a talus is suggested, especially considering the rapid fall of the ground in the same direction. The Boulder-clay appeared to me as good an example of undisturbed clay as seen anywhere in the Vale of Clwyd, Cheshire, or Lancashire, while the erratics are very similar. As to the age of the clay, it seems to be the Upper Boulder-clay—that is, some of the latest deposited during a period of glacial submergence. In the surrounding country there are no evidences of an earlier part of the Glacial period than that of the deposition of the Boulder-clay ; for the occasional striz on the rocks seem to have been caused by ice- bergs and icefields towards the latter end of the submergence, and I have not seen any deposit indicating a period of land-glaciation. Consequently, the Boulder-clay, in my opinion, represents the Glacial period, and if it were considered to be Post-glacial, we should have no glacial deposits whatever in the district. Nothing need be said as to deposits in distant parts of the country, and I am not aware that the mountainous region of North Wales, with its glacial moraines, throws any light on the subject. “ The remains of Mammalia found in the bone-earth were evidently deposited in the cave before the deposition of the Boulder-clay, and there are no indications of any Inter-glacial period between it and a still earlier period of supposed land-glaciation. The broken up stalagmite associated with the bone-earth seems to prove that the latter was an ancient deposit before the glacial subsidence. In this western portion of Britain no traces of the Hyena, Lion, Elephant, and Reindeer have been found in any Post-glacial deposit, and the inference is that all the bone-caves, on both sides of the Vale of Clwyd, are Pre-glacial, though the drift about them has been for the most part denuded in Post-glacial times, and many of them invaded by animals still living or not long extinct in the country.” It has been supposed that the cavern may extend for some distance in a north-east direction under the overhanging ledge of rock ; but it appeared clear to me that that extension was rather a rock-shelter than a cavern, as it is only a narrow space, between three and four feet in height, containing loose blocks of limestone in the bone-earth, but with no rock-wall on the outside. There was a narrow fissure, about six inches across, by the side of the rock-face ; but this was found to be a continuation of the joint in the limestone which we had noticed in the floor in front of the entrance, and it did not indicate any prolongation of the cavern in that direction (see Plan, fig. 4). As Mr. Morgan and Mr. De Rance were the last CAE GWYN CAVE, NORTH WALES. 573 to see the conditions before the place was finally covered over, I will give their evidence as communicated to me :— Mr. Morgan wrote that “the day after Dr. Geikie was here, Mr. De Rance came over to make a sketch, and just before the men began to fill in the pit he got Robert to make a fresh cut at the place,” 7. ¢. the north-east end by the side of the block of limestone, and under the overhanging rocks. He further says that happening to go down there just at the time, he noticed that “there were layers of sand which we had not seen before, and instead of being vertical they were quite the opposite, the layers going right across.” Fig. 4.—Ground-plan of the Cae Gwyn Cave, and of the Excavation in the Drift in front of the covered entrance. (Scale about 50 ft. to 1 inch.) A. Old entrance. B. New entranee, uncovered under drift. C. Chamber in which flint-scraper was found. D, E, F. Outside line of excavation; from D to E the drift was removed to the limestone-floor ; from E to F in parts only. * Position of flint-flakes, The results obtained by Mr. De Rance are given in his Note (p. 576). The section (fig. 5) is intended to show the sequence of the deposits as they were observed throughout the cavern, and in their extension 574 DBR. H. HICKS ON THE H ~ ae i} CO 3 | o0) 1 me = i; as) os) Hl S$ 3 i if | = = : = 3 = = | oD e = 7 ie 8 ar ° D 3 ce = x = ee S 3 DM : Z S oO S : Ss (oe) = 4 KS) 3 Qy 3 S = bs EI => ed) BAN an Da aft =o 3 SoS scr = EeSatoal 2 Sg i = 3 = = Se = SN e Ss a} B R a S = ; = 4 fey = a B > = a ig ey = SB ees > zs bea = = £ Bod 3 E nee > - 2 es = figs We oe S BSRy Ome cS) = oO = POSS es 5 A i OS as - fk Ga > Soe = 6 Sie Ota a a n er = —sES Soe S Cm SEB OHS acne ao a S 2S.-3 sad = HOS Jee ~ RAG BR BR = > Sp sune Fo S Org OF. S255 = ag Sek nse” F > OT G oo @ S Boe ae Xo S45 :S SESE aa 6 3 SS OR ee S S é = D gas SeeES | SHeOnkRam iS sssS SAAD of = or = em a CAE GWYN CAVE, NORTH WALES. 575 outwards into the drift-plateau in front of the hidden entrance. The entrance from the quarry was almost completely blocked up by materials which had evidently been thrown there, when I first crept into it, and at that time it was impossible to penetrate inwards for a distance of more than about 50 feet. Beyond that point the deposits reached to within a few inches from the roof, and as they were comparatively in an unusually dry condition along the whole length of the main tunnel, it is evident that this space was due to the contraction of the deposits by the loss of moisture. This is proved also by the fact that in the side channel, where the deposits were in a moist condition, they filled it up completely to the roof. As there are abundant evidences in the portion of the cavern next to the quarry, in creyices along the sides up to the roof, that that portion had been completely filled up originally, it may be presumed that when the cavern was exposed in quarrying-operations the workmen probably cleared out that portion sufficiently to enable them to ereep in for shelter, and had therefore prepared it to become, as we found it, a resort for burrowing animals. SuMMARY. The recent researches at Cae Gwyn have proved most conclusively that there was no foundation for the views of those who contended ‘that the drift which crossed over the entrance and extended into the cavern was remanié, and had gradually crept down the hill. They have shown beyond the possibility of doubt that the deposits which overlie the bone-earth are in situ, and are identical with the typical glacial deposits of the area. It was found also that these deposits had at one time extended continuously across the valley above this elevation (400 feet above ordnance datum), and that the caverns had consequently been completely buried beneath them. The explorations carried on in 1885, 1886, and 1887, in the Cae Gwyn and Frynnon Beuno caverns, show that they must have been occupied by the animals before any of the Glacial deposits now found there had accumulated, also that a thick floor of stalagmite had formed over these remains before the caverns were subjected to water-action. This action broke up the floor and completely re-sorted the materials, evidently washing out some, but also adding sandy and gravelly material to the deposits. Very large blocks of limestone, which were found at many points in the caverns, had evidently been disturbed by the same force, and had in many cases protected the original contents; they were, however, invariably found in the lowest deposits, and were covered over by laminated clay, sands, and gravels. It is certain that the caverns had been completely filled up with these materials, and in the case of the Cae Gwyn cave it would appear that they must have been conveyed in mainly through the entrance recently discovered under the drift. The stratification at this entrance was so marked and could be traced so continuously inwards over the bone-earth that there can be no doubt that it was the main entrance to the cavern. There was not the slightest evidence Q.J.G.8. No. 175. 2a = Fo a ee eer eit eC a ~ 2 a i pee — se 28 se a At oe TS ce, SS a ee eT 576 DR. H. HICKS ON THE that any portion of the material had been conveyed in through a swallow-hole, and the conditions witnessed throughout were such as to preclude any such idea. The presence of Reindeer remains in these caverns, in conjunction with those of the so-called Older Pleistocene Mammalia, showed that they had reached this area long before the period of so-called submergence, and evidently at an early stage in the Glacial period. Man, as is proved by the implements found, was also present at this time; therefore it is natural to suppose that he migrated into this area, in company with the Reindeer, from some northern source, as no direct evidence of his presence at an earlier period in this country has as yet been found. It is important to remember that Reindeer-remains have also been found in the oldest river-gravels in which implements have been discovered. Although Man reached this country in company with the Reindeer and other northern animals, this does not, of course, preclude the idea that he may also have reached it from some eastern or southern source, perhaps even at an earlier period. Nore.—Mr. De Rance, F.G.S., writes as follows :-—“* When: I assisted you in constructing the plan of the cave published in Quart. Journ. Geol. Soc. Feb. 1886, the working-face was excavated to within ten feet of the supposed chamber B of that plan, and the uppermost deposit was a fine yellow sand, its surface being within six inches of the roof-arch, and resembling the Glacial Drift sands of the pits in the neighbourhood and those of Mostyn and Bagilt. There was no trace of subsidence on the surface of the field above the point B. In June 1886 the entrance to the cavern had been discovered, and a vertical shaft, 20 feet deep, disclosed Boulder-clay resting on Drift- sand, which passed continuously into the cavern itself, while the underlying bone-earth similarly passed outside the cavern, and formed the base of the cutting, as far asit was then carried. In June 1887 the pit in the Drift was cut still further back, the bone-earth still continuing to form the base of the Glacial Drift; the north side of the cutting was boarded up and considered dangerous. In October of the same year the timbering had been removed; on the 10th of that month I accompanied Dr. Geikie, F.R.S., and a vertical band of clay and sand on the west side of a mass of limestone at the base of the north face of the pit was pointed out, also a clay-joint against the vertical face of rock forming the side of the hill adjacent to the mouth of the cavern. On the 11th of October, in the presence of Mr. Edwin Morgan, J.P., I made some excavations at the north side of the pit and three sketches of the same. I found that the mass of limestone before referred to was a tumbled rock from above, that bone-earth occurred behind it and beyond it, and up to four inches above it, where occurred a tooth of Hyena, that above this occurred a horizontal band, five inches thick, of washed sand passing directly up to the clay-pipe against the limestone wall, and which afforded a sort of material for the sand- pipe by the big block, the sand-bed passing across and cutting off its upward prolongation.” CAE GWYN CAVE, NORTH WALES. 577 Discussion. Dr. Evans, notwithstanding the fresh evidence now adduced, could not adopt Dr. Hicks’s views. If the bone-earth had been formed before the submergence, the sea would have cleared out the cave-deposits ; they could not have been formed during the sub- mergence, and were therefore subsequent to it. Dr. Hicks’s opinion as to the original entrance appeared to have changed ; his own im- pression was that a number of limestone-blocks occurred at the north-west extremity, and that this was not the original entrance. After the submergence the cave was occupied by animals, and the laminated clay afterwards formed by percolating water, and a certain amount of sand was also introduced by the gradual passage of water, of the results of which he had seen traces at the north-west end. The archeological evidence was against Dr. Hicks’s views. The narrow scraper was of a character not usually found in gravel-beds of river-valleys, but was characteristic of the later caves of the Pleistocene period. The other implement was like some from Kent’s Cavern. In the Clwyd Valley there are distinctly Post-glacial cave- deposits with implements of an older type than those of Cae Gwyn, and which were similar to such as occur in undoubted Post- glacial deposits of the east of England. At Drucat, near Abbeville, Prof. Prestwich has described a pit, 90 feet deep, which had been formed in the chalk by chemical action since the deposition of the gravel containing flint implements ; and sufficient allowance had not been made for the dissolution of the limestone at Cae Gwyn. Mr. Morton regarded the drifts as identical with those of the neighbouring counties, the shells of which were mostly of living species. He agreed with Dr. Hicks as to water-action having dis- turbed the bone-earth and stalagmite, and saw no signs of the looping of the drift or of a swallow-hole. The fauna was different from the Post-glacial fauna of the vicinity. Mr. Crement Rerp considered that Dr. Hicks tried to assign too high an antiquity to the bone-earth. Interglacial deposits with — mammals occurred in the east of England, and with plants in Scot- land, and ke would suggest the correlation of the bone-earth with these. The absence of a lower Boulder-clay in this district might be accidental. Mr. Srranan believed that the drifts of the mouth of the cave were part of the northern drift which he had mapped over a large part of Denbighshire, Flintshire, and Cheshire, and that the bone- earth lay beneath them. Dr. Hicks, in reply, stated that he had not, in this paper, sug- gested that the bone-earth was actually Preglacial, but only below the Glacial deposits of the area. That the bone-earth was older than the Glacial deposits was now proved beyond the possibility of doubt. He could not agree with Dr. Evans that the fauna associated with the implements at Cae Gwyn was Post-glacial in England, and considered the implements themselves of such a character as might have been formed at any stage since man first began to fabricate implements from flint. 2Q2 i : 578 MESSRS, GARDNER, KEEPING, AND MONCKTON ON THE i 35. The Uprrr Eocenr, comprising the Barton and Upper Bagsuor ‘ Formations. By J. Srarxie Garpner, Hsq., F.G.S., F.LS., i Henry Keerine, Esq., and H. W. Moncxron, Esq., F.G.S. (Read March 28, 1888.) i THe introduction of the Oligocene stage into our classification has i necessitated a partial revision of the grouping of our older British j Tertiaries. Whether this introduction of a new primary division fi into the Tertiary system was necessary or expedient may still be ques- tioned; but it has been generally adopted and is, for the time being, established. The division does not coincide in England with a marked change in either fauna or flora, though the series seems i nevertheless tolerably complete and well developed; its limits, q however widely stretched, show that the Oligocene stage compares i neither with the Eocene nor the Miocene in importance. ‘I Opinions have differed as to where the line of division should be H drawn ; whether this should be as low down as the top of the i Barton Beds or at the base of the Headon Beds, or even higher. i For our part, we think it desirable to uphold the view which places the demarcation between the top of the Bagshot Sands of Alum Bay | and the base of the Lower Headon Series, though it is perfectly ob- i vious that any such line in the midst of our series must be a purely i artificial one. ji An almost necessary consequence of the change in the classifica- ' tion has been the readjustment of the divisions of our truncated | Eocene, only the middle and lower division remaining, so that the ’ term ‘“ Middle” without an Upper Eocene would no longer be an t appropriate one. But the Middle Eocene, embracing as it does such 1 formations as the Nummulitic and the Calcaire grossier, has a litera- ture of immense importance, which it appears to us in the highest degree inexpedient to disturb or render obsolete. We therefore ! propose to adopt the view which reconstructs an Upper Hocene from | the Barton and Upper Bagshot Beds, and to show that. they form a sufficiently natural and well-marked group*. Neitherthe Upper nor i the Middle Eocene, however, will then continue to equal the Lower | Eocene in importance, and we cannot but look on the necessity for } any revision as unfortunate. The Kocene, as it stood, was a compact, | useful, and by no means unwieldy group, with a literature and , history that should have preserved it from dismemberment. The Upper Eocene was by no means so preponderating or so distinct as to render its removal expedient, and the transition beds were either satisfactorily located or might easily have been so. Finally the flora of the Oligocene, on which some stress has been laid, is so * A paper by Prof. Prestwich has been published (Quart. Journ. Geol. Soe. vol. xliy. p. 88) since this was written. He treats the classification we propose here as the one already established, vide table p. 88. This would render further insistance on its expediency unnecessary, did he not propose, /. c. p. 108, to sup- press this classification by totally abolishing the Middle Eocene. UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 579 distinctly Eocene in facies that the flora of Bournemouth, which is at the base of the Middle Eocene, may be said to be the typical flora of the Oligocene in Europe. The Upper Eocene in England will, according to our views, com- prise the Barton Series and the Upper Bagshot Series, the inferior limit being the Bracklesham, and the superior limit the Headon Beds. We have gathered conclusive evidence that the Upper Bag- shot Series of the London basin is, to a large extent, the equivalent of the Barton Series of the Hampshire basin, and represents, indeed, rather its lower than its upper bed. This fact, again, has rendered revision necessary, and the classification which, we submit, best meets the requirements is the following :— Upper Eocene. Lonpon Basin. Hampsurre Basin. { Becton-Bunny Beds. Chama-Beds. Barton Beds. Highcliff Beds, Upper Bagshot Series. [ Unrepresented. Upper Bagshot Sands. { The base-line of the formation is, it must be confessed, not too well marked, but it almost coincides with the disappearance of Nummulites in our area, and with a considerable change in the character of the fauna, through the disappearance of a number of subtropical forms. Deposition was so continuous here during the Eocene time that it is not always easy to draw strongly marked lines of division, for such, in this case, would only occur where there had been great changes of level, or where an ‘arm of the sea became landlocked and dry. It would thus be perfectly easy, Say, to distinguish between early Pliocene deposits in Italy and those forming in historic times along the margin of the Adriatic; but if the whole basin of the Adriatic were upheaved, and escarpments cut through it, as in Hampshire, it might be very diffi- cult to draw satisfactory lines between the Pliocene and the recent beds. Literature—We have not compiled any list of works on the Upper Bagshot Beds, as those of importance are referred to further on. The splendid preservation and abundance of the fossils in the Barton Beds attracted the attention of Mr. Brander, Curator of the British Museum, and, in 1766, a work upon them was so admi- rably illustrated that all the 85 species of Mollusca described in it by Dr. Solander can readily be identified. Professor Prestwich communicated descriptions of the Barton Beds to this Society in 1847-1854; and a Geological Survey Memoir on the Isle of Wight, dealing with the Barton Beds at Alum and Whitecliff Bays, appeared in 1862. Prof. Prestwich also described the Bagshot Beds of the Londun area in 1847 *, placing the Upper Sands provisionally some- where between the Bracklesham and Headon Series; and Trimmer included both the Barton and Bracklesham Beds in the Middle ; * Quart. Journ. Geol. Soe. vol. iii. p. 384. EE Ce ee eee eet. oe oe > Le ——— —elepee te - a e [SS Sa as ee ee at SS ee ae as a! ai 580 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE Bagshots*. But Prof. Prestwich, when again dealing with the sub- ject in 1856, still considered the question unsettled ; for he says :—- ‘* How far the Upper Bagshct Sands are related to the Bracklesham series it is difficult to say. The few fossils I have found in those sands are not sufficiently distinctive to enable me to pronounce a decided opinion. As, however, the fossiliferous Middle Bagshot Sands are very thin, and represent apparently only the lower or middle part of the Bracklesham Series, I think it probable that it is the upper beds of sand and clay of the latter which pass northward into the thick sands of the Upper Bagshot Sands. Still, it is possible that part of them may represent the Barton Series; for we see at Barton how shifting the upper part of that series is, how clay predominates at one place and sands at another” 7. The Geological Survey Memoir of 1872 on the London basin contributed little further evidence as to the age of the beds under consideration, and to the present day Prof. Prestwich regards it as an open question t. Dumont, however, classed the Barton Beds with the Upper Bagshot Sands, and they have been generally regarded as more or less equivalent in age. Area.—The Upper Bagshot Sands are chiefly restricted in the London basin to what is termed the “‘ main mass” of the formation at and around Bagshot Heath, and extend from the eastern end of Berkshire into Surrey and Hampshire. In the Hampshire basin the Barton Beds occupy the coast-section in Christchurch Bay for about three miles; they have been traced inland to a little east of Ringwood, near the village of Powner, and the Corbula-zone has been recognized in brick-pits at Bramsgrove, not quite halfway between Powner and the coast. The Chama-beds have been seen at Binstead Manor, on the Compton estates, a mile north of Lynd- hurst § (by the Rev. J. Compton, Rey. O. Fisher, and by Mr. Keeping). In the Isle of Wight they crop out and are well exhibited at Alum Bay, and are equally present at the other extremity, Whitecliff Bay. Mr. Bristow records that he met with Barton fossils at Gunvelle, north of Carisbrooke, and the clays without fossils have been identified at one or two other spots in theisland. The area over which they extend is remarkably limited, considering their importance. Prof. Prestwich correlated them with the Sables de Beauchamp in France || and the Laekenian system in Belgium], and the accuracy of his views in this case has never been disputed. Thickness.—The thickness of the Upper Bagshot Sand in the London basin nowhere greatly exeeeds 200 feet, and is usually much less, owing to denudation. It is, except the gravels, the highest formation in the area. In the Hampshire cliffs the whole series, from the pebble-bed at the base to the top of the Long-Mead- * Journ. Royal Agricult. Soc. vol. xii. p. 445 (1851). t Quart. Journ. Geol. Soe. vol. xiii. p. 132. + In his latest works, Quart. Journ. Geol. Soc. vol. xliv. (1888), p. 107, and Geology, vol. il. p. 363, he still regards the question as unsettled. § Mem. Geol. Surv. I. of Wight, Bristow, 1862, p. 46. || Quart. Journ. Geol. Soc. vol. i11. (1847) p. 354. ‘On the probable Age of the London Clay and its relations to the Hampshire and Paris Basin Tertiary System.” @ Ibid. vol. xiii. (1857) p. 107. UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 581 End beds, is about 200 feet thick. Our first measurements gave a total of 190 feet, and our second of 200 feet. Dr. Wright made a total of 210 feet. Prof. Prestwich’s measurements agree, except that he makes the Middle Barton Clay 150 feet instead of 50 feet. Prof. Judd underestimated the thickness of the upper part, for he implies that the whole of the Headon group at Hordwell*, including every- thing above the Barton Beds (presumably the top of the Chama-bed), is only 100 feet thick, whereas our measurements, to the top of the Lower Headon only, show 144 feet. The thickness of the Barton and Upper Bagshot Series at Alum Bay is 380 feet, according to Prestwich ; but Mr. Fisher subtracts 40 feet from the base to add to the Bracklesham, and the sands were not actually proved to be 100 feet thick, and may, from the position they occupy, have been folded or contorted. At Whitecliff Bay the entire formation is nearly 350 feet thick. Deposition.—The series, like the entire British Eocene, is dis- tinctly fluviatile and estuarine, and in correlating it we must bear in mind that it is physically impossible for any one quality of sedi- ment to have been deposited synchronously over any very extended area by such agencies. Though the beds of the Hampshire, the London, and the Paris basins present a broad similarity, the resem- blance in most cases disappears when we come to detailed compa- risons, and we have to rely rather on the faunas and floras contained in them. When these are alike, we regard the beds as synchronous, or on the same horizon, but with such deposits we should not perhaps trust too implicitly to fossils. The Upper Bagshot Sands of the London basin are such as might have been accumulated in a large bight or bay of open sea; but in Hampshire the series was evidently laid down within the influence of a considerable river f. Jé commences with a sand-and-shingle bank with much floated wood, and ends in the silts of the higher reaches of a river. In working through the beds, we start among the breakers of a bar far out to sea, and gradually make our way up into the smooth and purely freshwater reaches of a tidal river. The succession could only have been brought about by a sustained movement of upheaval, and we can best interpret the meaning of the repeated changes in the quality of sediment to be described by endeavouring first to realize what would be exposed if the sediments now forming at the mouth of such a river as even the Thames were similarly upheaved. If a slow, sustained elevation set in between the Isles of Thanet and Foulness, the first effect would be an inward movement of the littoral zones of sand and shingle, which would overcreep the previous homogeneous sea or estuarine mud, the thickness of the former, of course, depending on the rate of upheaval. Unless this * Judd, Quart. Journ. Geol. Soc. vol. xxxvi. (1880) p. 171. Tt Mr. Sorby came to this conclusion many years ago, and believed the cur- rents which deposited the Barton Clay near Muddiford to have been N. 76° H. and §. 74° W. In the upper part of the Barton Beds (at Alum Bay) he found no traces of currents, and inferred that the sea was too deep for the sediment fo be moved (Edinb. New Phil. Journ. n. s. vol. v. p. 289). = ee ——————— SSS SS SS ee eee Se P= eS 582 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE were very gradual, the passage from blue or greenish mud or clay to coarse sand would be abrupt, but if very gradual indeed, every gradation from fine clay to sand, and from a relatively deep-water to a between-tide fauna, might be preserved. If the river con- tinued to discharge its waters in the same direction, these would keep channels open in which no deposit formed; and as the water continued to shoal, banks and shoals would accumulate like those of the Nore, through which fresh channels are perpetually being cut and old ones silted up, presenting, when upheaved, a drifted, change- able, and confused bedding. The same kind of beds, but less in area, and with a fauna gradually passing from marine to more and more brackish, would extend a long way up the tideway of the river. They would also become more muddy in character, like the deposits off Sheerness and the Medway, because relatively more sheltered from the sifting action of rough and disturbed water. Still higher the more contracted channel would be kept open, but be flanked by extensive sheets of sediment evenly and distinctly bedded, because deposited intermittently by overflowing water, and perhaps interstratified with beds full of decayed vegetation, such as were seen in the section in Tilbury Flats. Most of this vegetation was rush-like, but in still higher reaches the brackish-swamp plants would be replaced by deciduous and other kinds of leaves &c.,. which might extend up the river as far as the influence of the tides and the lowness of the banks permitted. A transverse section across a valley once occupied by such a river would present a centre core of lenticular bedding, where the actual channel had been filled in, margined by horizontal beds of clay with stratified layers of vegetable débris and, probably, distinct layers of differing animal remains. With our hypothetical very gradual but sustained elevation, each of these descriptions of sediment would in turn be laid down over the same’ spot, presenting a vertical sequence strikingly similar to that met with at Barton at the present day*. That this is so rela- tively simple and easily interpreted is truly remarkable when we consider that had the channel shifted and the river meandered greatly, all the first deposits might have been cut away and altered, while if there had been great osciilation of level the bedding must have become infinitely complicated. The Barton Series, in fact, commences with a great mass of white sand, with lines of well-rolled pebbles, indicating raised banks in shallow water; and since the main mass of the underlying Brackle- sham seen at Hengistbury was undoubtedly formed in more open * Inthe London Clay it is easy to realize that deposition took place in a broad estuary or tract of sea, such as the German Ocean 50 or 100 miles off Harwich. We can trace where great drifts of fruits and seeds, such as those met with by Moseley, 70 miles from the mouth of the Amboynah river, New Guinea, became habitually water-logged and sank, how far beyond this ma- cerated twigs alone floated, where certain types of Crustacea and Mollusca lived and died, the various depths of .the water and proximity to shore at dif- ferent localities, the main-channels strewed with terrestrial débris, and the we regions into which these were never wafted. om UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 583 sea, as indicated by the prevalence of sharks’ teeth and fish-palates in it, the period ushering in the Barton must have been one of up- heaval. We cannot expect to trace our base-line of sand and shingle in all localities, because the same amount of upheaval taking place in deeper water would merely result in a diminution of depth with, perhaps, but a slight change in the character of the sediment and nature of the fauna. The passage in the Isle of Wight, and pro- bably in the direction of the New Forest, between the Barton and Bracklesham Series is, in fact, an almost imperceptible one, and in some places they appear a practically continuous formation. ‘This mass of sand and shingle is, at Highcliff, followed by dark green sandy clay, similar to that of the Bracklesham beds, but full of drifted wood, fruits, and fir-cones, and coniferous twigs, and com- prising a thin band with Nwmmulites elegans, fish-teeth, and, more rarely, bony plates of Chelonians and Crocodiles. This assemblage, confined, apparently, so far as vegetation goes, to objects with considerable powers of flotation, should give a great insight into the conditions of deposition, were observations of the necessary kind in existing estuaries not so scanty. A ferruginous band marks, perhaps, a considerable shift when the deposition of mud was almost suspended, and preceded a change which ushered in the stiff drab clay of the Highcliff Beds proper. That the water still remained shallow is apparent, since the shells, unless minute, are broken into small fragments and drifted with sand into pockets. A shore-crab, described by Dr. Woodward, was probably from a zone of pinkish clay in this part of the series. A small Echinoderm is abundant near the base, and first Psammobia and then Pholadomya become common, and are always found in the vertical position assumed by them in life. Next we have the Middle or true Barton Clay, at first glauconitic and then plastic, with its rich assemblages of shells, many of large size, and ending with great and wide-spread drifts of shell-matter, chiefly comminuted and in an irony matrix. This is succeeded by a mass of sand crowded with Chamas and a peculiar fauna, which appears for the first time and as suddenly disappears, giving place to the truly estuarine Becton-Bunny Beds, which in turn pass upward into the brackish Long-Mead-End Beds, and then into the fluviatile Lower Headons. Great interest attaches to the Barton Series on account of its fauna, which is both rich and, to a large extent, peculiar. Prof. Prestwich long since remarked on the more northern character of its Mollusca, contrasted with those of the Brackleshams*. The Submergence implied by him seems, in fact, to have destroyed some narrow barrier or isthmus which for a long period had kept the Southern Eocene sea, of which the Brackleshams are the earliest * “The Barton-clay sea seems again to have been more connected with water opening to the northward than did that of the Bracklesham Sands; for several species of the London-clay sea . . . that had disappeared in the intermediate Bracklesham period, reappear in the Barton series. In fact, the fauna of this greup, together with that of the Sables Moyens, has not so southern an aspect as that of the Calcaire grossier and Brackleshani period.” (Quart. Journ. Geol. Soe. vol. xiii. p. 131.) Stas a ESE. 384 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE British representatives, isolated from the more northern basin in which the London Clay was formed. The mingling of the seas apparently lowered the temperature of the water to an extent suffi- cient to drive away such essentially tropical forms as the larger Cones, Cowries, Bullas, Harps, &c.*, without, however, greatly affect- ing the character of the contemporary land vegetation. We cannot say that the whole period was one of sustained and continuous elevation, but the drifts of broken shells at the close of the Middle Bartons indicate an upheaval and the presence of strong currents. These shell-drifts thicken and become more numerous to the east and north. The protracted elevation soon afterwards forced back the sea, and converted the former estuary into a brackish- water reach of our great Eocene river. The Middle and Lower Bartons were evidently deposited in almost pure sea-water, though the considerable number of rare freshwater shells occurring in Edwards’s list, even from Highcliff, would imply a river-current strong enough to have carried them along. Prestwich, moreover, mentions the occurrence of Cyrena obovata and Potamides cinctus in them at both Alum and Whitecliff Bays. It seems almost super- fluous to point out that if the Barton Beds were estuarine, quite different deposits would be forming synchronously in the higher reaches of the river as well as further out to sea. Something not very different in quality from the freshwater Eocenes, which occur below as well as above them, must, in fact, have been forming in their vicinity or at no great distance ; while the oceanic deposits of this period are probably preserved in the bed of the Atlantic, and have not been exposed to view. In dealing with our Eocenes it neither follows that distant beds are synchronous because they are similar, nor that they were separated by any intervals of time because they are dissimilar. DESCRIPTION OF THE Bens. The Barton Section (fig. 2, facing p. 594). Of all the sections exposed, by far the most important and the classic one is that occupying the fine open bay of Christchurch, facing the Needles, and terminated westward by Hengistbury Head, and eastward by Hurst Castle. Towards the centre of the bay, where the Bartons are developed, the cliffs average little short of, and in places exceed, one hundred feet in height. Their summits are nearly level, and they terminate rather abruptly near Muddiford to * The following are the principal types driven away or extinguished, and all of them have a highly tropical aspect :—Cyprea Bowerbankii, C. tuberculosa, C. globularis ; Voluta cithara and V. muricina; Conus deperditus and C. diadema ; Pleurotoma attenuata; Harpa, all sp.; Cassis gigantica; Natica cepacea, N. hybrida, N. ponderosa, N. pachycheila; Turritella sulcifera; Dentalium grande; Cerithium giganteum; Bulla Edwardsii; Hipponyx cornucopie; Sanguinolaria Hollowaysii, Cardita planicosta, Arca Branderi; also the corals Oculina, Siderastrea, &. Some of the more temperate of the London- clay genera, such as Trivia, reappear, but not Astarte, Cyprina, Verticordia, Vermetus. The only species of large size to appear for the first time in the Bartons is Voluta luctatriz. UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 5895 the west, and sink more gradually on the east. In composition they are clay or sandy clay, capped by eravel-deposits, twenty and even thirty feet thick in places, which constantly founder and partially obscure the Eocene beds below. The beds forming this coast-line begin well in the Bracklesham series to the west, and end in the Middle Headon, at Paddy’s Gap, to the east. The cliffs occupied by the true Barton Series form ruined terraces, and the beds, with few exceptions, can only be seen 2m situ here and there along the sea-margin. ‘The sea, however, which is rougher than at Bourne- mouth, regularly washes the base of the cliffs in the middle of the bay, and exposes an unending succession of fossils. On the other hand, the Hampshire Avon, which for several years swept along the base of Highcliff and threatened to undermine the Castle, has again shifted the direction of its outfall, and left such vast masses and bars of shingle behind, that the sea no longer reaches the cliffs under Highcliff; and these are consequently assuming an angle of repose, and becoming so overgrown that their stratigraphy, formerly clearly defined, cannot now be made out. This fact helped to decide us to redescribe the Barton Beds without delay. The section has been frequently described and measured. There are some slight discrepancies in the thicknesses arrived at, but abso- lute identity cannot be hoped for in dealing with beds whose thick- ness may vary within a few feet. Our measurements were checked on each occasion, the second time by Mr. Geo. Harris, F.G.8. The results are tabulated below, and, for easier comparison, we have taken the maaima and, in some cases, bracketed two or three sub- divisions of other authors together. We have adopted a tripartite system, each division of which is characterized by peculiar fossils and distinct lithological characters. as ce) ie 5 ep = ‘ 43 = | S'S] o's ay ee esees lee 2 S$ | 8 | 35 e aA | o os) Becton-Bunny \ Clay, no. 18, Wright) 25 30 23 26 |Upper Barton, 0 of __ Beds Sand, no. 19, Wright} 20 30 19 26 Prestwich. Chama-bed, no. 20, Wright ............ 15 20 15) 18 Barton Olay, no. 21, Wright ......... HOW 150%). .50 53 |Middle Barton, part @ = of Prestwich. Highcliff Beds, nos. 22, 23, 24, base 80 70 50 49 |Lower Barton, part @ according to Wright ............... of Prestwich. Green sandy clay and pebble-bed .... — 15 14 10 _ ONL ta eee 190 | Sh5* | Ul eee ooo. -. occ s concer renee: nas we ss 45 The Bracklesham Beds at Highcliff form a vertical escarpment 45 feet high, of compact white sand, with an admixture of carbo- * This measurement appears due to a lapsus calami. 586 MESSRS. GARDNER, KERPING, AND MONCKTON ON THE naceous matter and a band of ironstone Septaria throughout a part of their horizontal extent. The base is not visible here, but can be seen at Hengistbury Head*. Hight feet above the beach there is a scattered line of typical Bracklesham pebbles, and another more considerable layer of the same capping the white sandy. The flints are moderate in size, either quite white or black, and mixed with small quartz-pebbles and grains, and lignitic matter abraded and worn into pellets. The upper layer is imbedded in warm-drab loamy sand, with pale green grains and sulphur-yellow partings and pipes, giving a green streak to the tool. Casts of bivalves abound in the upper pebble-bed, and, like the pebbles themselves, are most numerous at the base. ‘The pebbles extend upwards throughout nearly 3 of the 4 feet of loamy sand composing the bed. Mr. Osmond Fisher looked on the upper pebble-bed as indicating a natural physical break, though he addedz#, “the division is probably in reality one of convenience only, the two groups forming a con- tinuous series, changing gradually throughout in its lithological character and fauna.” Prestwich considered that there was no break between the two formations. A dozen fossils were determined - by Fisher from the sand, and 18 from the pebble-bed, only 4 of which are Gasteropods. The last 10 feet is very green, stiff, sandy clay, rifle-green when fractured, but of a bright green colour when scraped. It abounds with wood, mostly TYeredo-bored, and well- preserved fir-cones are not uncommon init. Its angle of repose is very steep, and the abundance of green grains enables it to be distinguished easily from the overlying series. Casts of Mollusca abound in this part of the series, and are seen to belong to species that pass into the Bracklesham below as well as the Barton above §. At this horizon there is a band 9 inches thick of ferruginous loam or imperfectly formed ironstone, mottled with green and con- taining grains and small pebbles of quartz. It was described by Prestwich as a band of tabular soft Septaria mixed with green-sand ||; * ‘“ Description and correlation of the Bournemouth Beds.—Part I. Marine Series, by J. S. Gardner,” Quart. Journ. Geol. Soc. vol. xxxyv. (1879) p. 214. t This is coarse quartz-sand of largish subangular to rounded grains, mixed with very minute grains. + Quart. Journ. Geol. Soe. vol. xviii. (1861) p. 88. § Osmond Fisher, /. ¢., gives the following list:—Fusus pyrus, Pyrula nexilis, Voluta nodosa, Dentalium, Cardium semistriatum, Cardita (small ribbed), Cytherea (a Barton species), Crassatella costata, Corbula pisum. An analysis of the beds is also given, p. 86:— Wharher? J. 5.024; ate ree 10-02 Sila se ee eee 50:11 Tron protoxide’” j...2225--0 25°04 AQuInnS 2c o eee eee 6:12 MASSA .ec)7 5-5 . fs a - ’ - es) ern oy “d i . ' As | oe "syne! {lg SF RSI aoa avg ie € ith & . . A r Pe ate Fa hier ne b - Aye eae eau: oe ’ 2 ifr, als y P - AT ae \ v 5 a 2 Ce AOD gaa KGS ’ 7 - 4 roe) i ¥ ve a UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 995 We would also call attention to the singular interruption to the bedding which occurs a little west of Long Mead End, where the Leaf-bed and Crocodile-bed are cut through, and replaced by a con- fused mass of clay and sand with drift-wood, a large piece of which is seen to have been anchored vertically in the mud (fig. 3). Fig. 3.—Section at Hordwell (just west of Long Mead End). a. Gravel; 6. Greén clay with iron. This section of an old channel occurs a little west of Long Mead End, and is about 200 yards in length. The green clays thin out, but the Crocodile- beds are dovetailed into the lignitic sands and clays. All zones are lost, and the whole cliff looks like black or dark ash-coloured sand. It is very shaly, full of wood for the higher 16 feet, and becomes more sandy towards the base. A band of white concretionary clay-stone, with pieces of wood im- bedded in white plastic clay occurs, 16" thick. The sands are rather false- bedded and twisted, but seldom dip more than 10°, and the whole is very full of wood, especially towards the base. At A, the mass of wood is vertical, and gives the appearance of vertical bedding at that spot. The green clay is also penetrated by wood in the same direction. A good many ligneous fruits are to be found near the two extremities after rain. This is obviously the channel of an old river, similar to the estuary channel, filled with oysters, which cuts through the ‘ Venus bed,” between Colwell and Totland Bays, and such can frequently be traced in estuaries and fluviatile beds when these are of any extent*. Note explanatory of Section through the Lower Headon at Hord- well (fig. 4).—The section from the top as far down as the Chara- bed was made nearly due south of Hordwell House. The rest, to the Lignite at the base, was measured about 450 feet east of Long Mead End. At that point the 10 feet or so of beds visible above the Chara-zone, and immediately under the gravel, are considerably * Mud-beds, teeming with molluscous life, such as those of the Headons, could only be formed on the banks of a tidal river or estuary with extensive flats subject to overflow. Any change of level, whether by modifyirg the depth of water, making it more or less salt, or altering the quality of sediment de- posited, might profoundly modify the fauna; and a section through such an area might disclose many minor, but constant, parallel zones of sediment, differing from each other and characterized by quite peculiar forms of life. So long as the section coincides with the direction of the flow of the estuary, the beds are continuous for long distances, but when it becomes transverse we find a channel of confused bedding, with a recurrence of the regular bedding on each side. FA eH A ° Zz e be ) va o) P| o a py inal S rl F fa < ids) n AG D 3 | 596 "Ur g DuadAD YA Ory} “Ur F oBeq PUES ‘SoTvoS-YRy YIM OUST. — "Ul OT ‘WAmownz0g UOYOAG [BUOISBODO PUB 8jJOOK YIM ‘ARTO HOLE, ‘ur ) “wungobuhd wnynwag pus ‘snyyhpy ‘nuassienq ‘whuounjog yyia ‘XejTo yours, ‘alg yooy Z ‘AvlO pue o4rusty o[qeray oanduy,~ ‘Avpo ATxVut used peso “HOTY} “Ul 8 puBd UoIy *sgoxood Ul pogyrap vurpnyygy "PUBS QBIP UI ZOOL YAIA “TABUE KODA 4YsITg ‘sdunjaed puv sjooa youtq yyim ‘Avpo-odid quay ‘pues Mopod UI SJOOT TTA pus ‘mores YIM popjour ATQY SITs ‘Aejo Apuvs yarvcqy ‘Ayounyo sururooeq ‘Anjo Ayvwur Fy4Vg--. *toABT YOB{ ULYyy— ‘ST[OYS poynururur0o puw souog poT[or YIM “poq-oy1jordog # Fae bat Seg ee "m10990q pues doy ye vuvjd vhwowunpog josouoz ‘oXvjo oc0ul puv oseq 4¥ coyAep Surwmoseq ‘pues Aoas oped ouy A104 ‘JYSIOM UT SU} [eLeA0S 0} dn oUd}SuOAT puw Avo JO sossvur YyIM ‘Le[O ATAvUT MOOI poT}IOT[ “Ur T pueq yorjgq— ‘9U04SOULI[-DOUUWT — 099 “nawUlry “nUassiaug” YYIM ‘BNOAOFITISSOF JOO} Z ‘OSB 4B APOOs puB soYsna “puvs MOTTOA Fo TTF ‘sq00a YIM ogUdIT ‘029 ‘SoYsna ‘s}00a YAM “SAVIO GvVap PUL o}rUdIry ‘vauuyT poysnao yy Avo ATcvur udead YY Sag, "spoos JO ourry “Avo poammojoo-o04vys ATAVoU UT ‘MUIssiwIn, DIUDjayl ‘DULpn)DE ‘ow *oseq SpivMo7 Loxaep ‘Aepo Jo sduyaed Load y{IM ‘pues poyvururery ‘SOUOd-[RUIUIVUL PUB -OT}.1Ny WOxOAd YAM “qavur AYsnt YSIUIEL9 *SOTYY “UL | ‘eaoqge 09 *Y4909 SJUopoOd “BIGoJIOA SJUOdIOS YIIM OUTT Yavp {UL G [AvUT WeOUWTT *[OABID YIM PoUlLys [IB "ampLory yo ‘uopnary wanoT oyp ybnowy, woynrG—'F *SiiT ME | Se F “UL “4g f Ol g "oqrasry 2 = acco 0 LT : pod-BI[varUe Pr Sie cog poq-yuoy Sls } UF 1-8 | p9q-eT1pooo.19 ore] OFF LQ ct euojsounryT v OT 6 § "" paq-vuny9 0 GI rreseererereees gag 0247) 0 It 8 1 eee 6 0 One UR UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 597 altered and appear of a whity 4 and ochreous colour, very sandy, ; and without fossils, except some layers of Paludina quite at the a base. The Lignite Beds them- hg selves were measured at Long Se Mead End. The beds appear to Sag be very variable, as the detailed B's g measurements differ considerably ESe is from those previously made, Feo. & 5, though the principal beds re- Pe main as land-marks. The thick- 2 2 nesses have been variously re- corded :—Marchioness of Hast- ings 78 ft. to 94 ft. 10 in.; Dr. Wright 64 ft.; Tawney and : S Keeping (Quart. Journ. Geol. $38 . tao y, Soc. vol. xxxix. (1883) p. 567) S8 e's 834 ft eos Bs cs ook. pees Section atone tHE New Live pee FrRoM BrockENHURST To CHRIST- oe CHURCH (fig. 5). The cuttings forthe newline y , Boy from Brockenhurst to Christ- G 253” . RIO church present us with a second $2 $8222 section in some degree parallel Sears with the coast-line, but several nm “~ EB a . . . . ie.) miles inland. Our friend, Mr. 7 xg Beae George Harris, after checking OF.RS 8. with us our previous measure- Ba ery ments along the coast, aided in measuring the entire length of this cutting, and our section is prepared from the notes taken concurrently by each of us on the spot. The new exposure shows that the shell-beds are greatly thickened and maintain their character and position above the Septaria for a long way in- Jand. It further enables us to check off the thickness of the gained with Chama-bed, which, though un- gravel. fossiliferous, is unchanged as to its matrix *, The Becton-Bunny Beds seem, however, to disappear * Mr. Cole has examined this, and reports that it is a bed of very angular rather coarse sand with some few green grains. There is some clay with it, Ry but less than would be expected from | = its general appearance. , i OLS ‘speq-npunyg ‘puuUpy Uuopupzy mou uy mou ue buyng fo sonf yuou ‘spag uozing ay) fo uoyjsagy—'g *Biyq ‘oaety 598 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE a as at Alum Bay, and the whole series of Upper Bartons above the Chama-beds is obscured by weathering and by gravels. The vertical section is :— ft. in, Chama-beds, partly stained by gravel, about ......... 18 0 Drab lay 2 .....55283. assnadeeswnctouep et eeeee eee ee 1 6 Shelly (sed). ..... 2s. sateen sooepstes dee het bee 22 O SOPlaria i 6 . St SOS Se So 2-— >. DAFT = a. Gravel. 6, Light steel-grey clay, with shelly bands of crushed Paludine, &e. Nothing further is visible, except gravel, for about a mile, wher some white sand, some small patches of lignite and crimson-mottled clay are visible; but the bedding is disturbed and confused, as if thrust up from below, and we can only conjecture that the sand may represent the horizon of the Crocodile-beds. They extend hori- zontally for 500 yards, the lignites occurring close to the bridge over which the Brockenhurst Road is carried. The section ends with 18: UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 599) feet of green clay mottled with shells, and 6 or 7 feet of com- pact pale green sand, the com- bined horizontal extent being 700 yards. This must, we believe, represent the beds im- mediately below, as well as partly the Unio-beds of our Hordwellsection, for the Middle Headons occur somewhere in the next rising ground on the Brockenhurst side. Tue Atum-Bay Srcrion (fig. 7). The section at Alum Bay is but 6 miles from Barton, and being through lofty cliffs with vertical bedding, is extremely easy to measure and under- stand. Measurements taken by Prof. Prestwich were pub- lished in his “ Memoir on the Isle of Wight Tertiaries,” in 1846, the entire series forming the 29th and 30th beds of his section, with a thickness of 380 feet*, inclusive of 100 feet of siliceous sand. In 1857 he separated the formation into three not very well character- ized beds as group a, and made the overlying siliceous sands his division 6. Mr. Bristow, with Mr. Gibbs, measured it again, the results published in the Survey Memoirs of 1856 and 1862 showing a total thick- ness of 300 feet, exclusive of the siliceous sands. We think that this is a little over-esti- mated and that the measure- ment of 380 feet is nearly correct. Mr. Fisher, in 1861, reduced the thickness shown by Prestwich by 48 feet, placing the beds below the Nummutlites elegans, var Prestwichiana, in * Quart. Journ. Geol. Soe. vol. ii. p. 109. A Shin Wie 3 | 8 oO Lar | od 2 B Ww aN rn cd Vv “HOWE e[PPIPL ‘UOPLIVE LOMO “MIBYSePOVIgE DUDS 272YM. ‘UOpesy] JaMorT puvng DID M07] 2X hoki; £72 Ong “WY OY, T— 1, Sit 7099) hog @ “wor *snUDIYyoun;sokT Py 224 NUH AT 600 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE the Bracklesham series. We make the section (fig. 7) to be as follows :— (White sand, becoming clayey and yellow towards ft. in. ae | the base, about ..........0:..0.0.-ss00seeeeennee nese see sees 90 0 B pper 4 Dark-blue clay, with one band of ironstone a foot Beton | thick, 6 feet from top, and a similar band 4 feet \ lower down; numerous fossils * .........sscseceeeeeeeee 24 0 (Pale and ferruginous yellow sandy clays, green in the upper part, Lignite, Corals, Dentalium, Ostrea, Cor- | bula, Plewrotoma, common, and of several species, pale yellow sand at base T ...........-cecccececsceseneecees 70 0 Layer ie tabular Septaria, with many sharks’ teeth, : pebbles, fragments of wood, &c., and layer of aan | scattered pebbles beneath in green sand ............... 10 0 arton. | Grey and brown sandy clay, with numerous casts of fossils of Middle Barton species, the shells being pre- served in the lower 7 feet only ............cssssscecensene 29 0 Drab clay, with band of Septaria at top, and a second one 16 feet lower down. Corbula, sharks’ teeth, and \ Lignifie T.2..... cic. ocn0<---0nsscie noe ew heen eee 58 0 (Dark bluish-green clay, with sands in patches at the ae | top, containing Buccinum canaliculatum, Volvaria Bictan 4 acutiuscula, Mitra parva, &. The whole capped * | with 9 feet of pale grey loamy sand ............---+-++++ 56 \ The same with Nummulites elegans, var. Prestwichiana 1 oo ( Glauconitic sandy clay, the upper 10 feet with Corbula, | &c., then about 15 feet in which casis of fossils are Bracklesham. { numerous, and the rest unfossiliferous { .............-- 47 6 "Pebble bed) <2. -....:.cc.cces--sbeeaceeeo-: ae 0 6 \ White sand. (inclusive of 48 feet of Bracklesham). The white sands at the top of this section have been quarried for glass-making, and as the change from the vertical position, in which the Bartons occur, to the nearly horizontal bedding of the Lower Headons takes place within the thickness of these sands, they cannot now be very accurately measured. They were estimated by Prestwich to be 100 feet, and by Bristow at as much as 140 to 200 feet, but we doubt if they even reach the former estimate. Though quite unfossiliferous, they represent the Becton-Bunny and Long- Mead-End Beds of the opposite coast. The Chama-bed should appear beneath them, and one of us has found something very like it, but rarely exposed, at low water, just * These agree almost precisely with Bristow’s observations, Mem. Geol. Survey I. of W. p. 48. t Bristow, l.c., adds a band of small pebbles of white quartz and with sharks’ teeth, 2 inches thick, 3 feet below the Septaria, and a third large layer of Septaria 5 feet from the base. Also a band of fossils 13 feet from the base, and a band of lignite 10 feet from the base. His base is, however, 9 feet above ours, the latter thickness being separated as pale grey, loamy sand, thinly laminated. t Bristow mentions that a fossiliferous bed of indurated marl, 6 inches thick, occurs 30 feet 6 inches from the top; lignite bands at 1 foot 3 inches and 19 feet, and a layer of Septaria 28 feet from the upper part. UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 601 north-west of the pier, with Zurritella and Chama squamosa, but not massed together. We could not trace it in the cliff, though the iron-bands seem to occupy the proper horizon of the shell-beds. The Middle Bartons seem abnormally developed, being more than three times the thickness seen at Highcliff, and nearly twice that at Whitecliff; but our junction is only 9 feet above the Highcliff sands, perhaps considerably (12 to 20 feet) too low down. We have taken the Survey measurement for the lowest bed of the Upper Barton and to some extent for the Upper Bed of the Middle Barton, as the road to the pier has been so considerably widened that these divisions are now cut out, only three beds of Septaria being now visible, and no lignite. Many rare species, not met with on the mainland, are confined to these beds. The Lower Bartons maintain their normal thickness and physical features, the pockets of sand, with drifted shells, occurring precisely as at Highcliff, with the chief characteristic species; but the beds being vertical and squeezed are not so favourably situated for collecting*. The shells in it are small and confined to the upper part, gradually giving place to casts for a few feet, after which the beds become unfossiliferous. The last distinct zone of fossils is the Mummulites-elegans bed. The quantity of ferruginous and carbonaceous matter indicates, perhaps, shallow water. In comparing the section generally we are unable to recognize any of the subdivisions of the Upper Barton on the mainland, the beds having become, perhaps owing to their vertical position, more uniformly sandy and unfossiliferous; the Middle Barton maintains its characters, but is enormously thicker, even making some allowance for the obliquity of the section: the Lower Barton has not increased to any appreciable extent. Tue Secrion at WaurrecuirF Bay (fig. 8). The most perfect section through the Eocene formation in England, and perhaps in Europe, is exhibited at Whitecliff Bay, in the Isle of Wight. The only beds at all concealed are those of the Barton Series, which have been hidden for years by slips and growths of herbage and brambles. It is apparent, in glancing along the cliffs, that if the strata had chanced to have been plotted out into divisions on this spot, instead of elsewhere, a very different arrangement from that which exists would have been arrived at. All the Brackleshams above the drab clay, with seams of lignite and rootlets, must have been included in the Bartons, and the Brackleshams, as a marine formation, must have been limited to the beds with Nummulites levigatus, &c., 66 feet lower down than the Pecten-corneus zone. It is far from certain that such a division would not have proved more natural than that which obtains, for not only is there evidence of intervening dry land and freshwater deposits, but the fauna of the Lower Brackle- * Bristow mentions Dentalium striatum, Fusus longevus, Voluta spinosa, Solarium, Cardium, Natica (2 sp.), Fusus pyrus, Rostellaria, Cancellaria, Pleurotoma, Mitra, from this bed. 602 MESSRS, GARDNER, KEEPING, AND MONCKTON ON THE shams, with its giant Nummulites, Bullas, and Cowries, and its wealth of corals, differs far more from that of the Upper Brackle- sham, than the latter does from that of the Bartons. Had the Barton Series been described from the Highcliff section first, and then been followed from west to east, taking first Alum Bay and then Whitecliff Bay, the entire Upper Bracklesham Series would have found a place in it, and the base-line been drawn where a decided. physical change existed. The accidental circumstance that Mr. Fisher began to plot the Bracklesham Series at Selsey, led him to place their limits very high instead of very low. The whole of the strata on both sides of the Bill down to the London Clay were placed in the Bracklesham, perhaps chiefly because the thick freshwater sands and clays, which cut them in two, are unfossilifer- ous and seldom or never exposed on the shore. The highest beds at Selsey were traced to the New Forest, where still higher beds with similar species overlay them, and, finally, a small zone, con- - taining a particular variety of Nummulites elegans, was fixed upon as the upper limit of the Bracklesham Series. That the line is drawn in “passage beds” is admitted by Prestwich and by Fisher himself, and it is thus less satisfactory than one coinciding with a physical break. As no better line of separation can be found, how- ever, without trenching very considerably on the Bracklesham, we propose to retain the base-line inthe zone of Nummulites elegans, var. Prestwichiana. In retaining the present divisions of the Bracklesham, we must remember that the lower is very different from the upper, and that the latter passes insensibly into the over- lying Bartons. The section at Whitecliff Bay (fig. 8) commences with mottled clay resting on chalk; then follows an eroded surface with scattered pebbles; some loamy sand and the Ditrupa-bed ushering in the London Clay. This is nearly 400 feet thick, and at 50 feet from the top we can recognize layers of soft concretions, crammed with Pectunculus, representing the Bognor Beds. It is capped with 100 feet of buff sand with a few bands of scattered pebbles. The section is very oblique to the outcrop, so that all these beds have an exaggerated thickness. The Lower Bagshots consist of 137 feet of finely laminated clays and sands with vegetable impressions, and end a little below a bed of Cardita planicosta, marking the base of the Lower Brackleshams. ‘These consist in turn of 56 feet of greenish sandy clay, evidently marine; 52 feet of laminated clays, with some lignite of doubtful origin ; 90 feet of greenish sand, marine ; 37 feet of the same with Nummulites levigatus ; 66 feet of clay, with belts of lignite and underclay with roots ; and then the Pecten-corneus zone of the Upper Bracklesham. The “ Brook Bed” of Fisher follows, 23 feet thick, greenish marine sandy clay; sandstone 5 feet; Nummu- lites-variolarius zone 34 feet 6 inches; 93 feet of Huntingbridge Beds, not very well exposed; terminating with the zone of J. elegans, var. Prestwichiana, taken as the line of junction with the Barton Series. The Barton Beds were not separated by Prestwich in 1846, UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). when he described the section*, but are given as ‘‘ Headon-Hill Sands,” 202 feet; 37 feet of laminated clayey sand; 44 feet of bright yellow sand; 162 feet of imperfectly exhibited brown and grey clays, &c. ; 32 feet of fossili- ferous brown clay resting on 4 feet of sandstone. The latter is placed in the Bracklesham by Fisher, and the junction somewhere in the 162 feet of clays(Quart.J ourn. Geol. Soc. vol. xviii.(1861) p. 68). The artificial nature of the divi- ding line is shown by the fact that no observer previous to Fisher had ever thought of divi- ding up the almost homogeneous mass of fossiliferous clay which is now classified as 93 feet of Bracklesham Beds and 60 feet of Bartons. Whilst preparing this commu- nication, one of us visited White- cliff Bay and found the Barton Series exposed between tide- levels in an unusual, if not an unprecedented, manner. ‘The section was measured, and the corresponding beds subsequently exposed by digging at the base of the cliff, when the first mea- surements were checked off. The result was published in the Geological Magaziney. It must be remembered that the section is not quite at right angles to the outcrop, and a diagonal direction may somewhat exag- gerate the thickness. The mea- surements are for the most part reproduced from the work cited, as we believe them to be more accurate in the case of the Barton Beds proper than those * Quart. Journ. Geol. Soc. vol. ii. . 224. The Barton series is com- prised in beds 17-20. t “On the Discovery of the Num- mulina-elegans zone at Whitecliff Bay, by H. Keeping,” Geol. Mag. Decade iil. vol. iv. p. 70. ‘mopve IaMOT “UOpLeT OTPPLN ‘mopIVg 1aMoT ‘UBYsSaTpOVI_ umojeg zoddq e \ < rs Cs ata bape OM hy’ f ay enliel HT |! Paha Ail} CA LAT Ty P) “ tl lula . ia} |* hi 1 ui bY | "peq-pwnyg hog Jy M wD woysg7—'g “SLT “pueq ouojsuory *QUOZ SNUMLYIIN} SAT 603 -SIJUINULUUNAT 604 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE arrived at subsequently by two of us under less favourable con- ditions, and which we found to differ. The total is within a very few feet of that arrived at by Prestwich in 1846 and 1857. We have further grouped and correlated the beds with the three divi- sions seen in our typical section (fig. 2, facing p. 594). Sxcrion at Wuirectirr Bay (fig. 8). Tiower Headon | Lower Headon.........00s2.<.. s00-= SSSs LA VATS SS ty, My ; o - Lypo-Etching. St. The numbers refer to localities noticed in the paper. Fossils from the Upper Bagshot Sand. (All are from Tunnel Hill, marked 21 on the sketch-map. The * indicates where a species is most abundant.) Cea |. 2) 3.) Sy 5 = a sa | a ee aa] pe | 2) sane s ° a a aS HH | eB =) Ancillaria canalifera~ 2.2... 252. ./0 i662 Lee — x 5 = Buccinum canaliculatum .................-2---2- Pee ee Balla attenuata jcécpieeseeileudin eh. See eeee — — 2 * Bolla clip tity jo oe ag ee eo = * = = BST Pei: A ag AP le re laa eg AE Bulla orseuls s.. 4 ih sce se Bee eee * Cancellariateyullsa’ : ccna eee — — — — — | « Cassidani tedasay acc; nbd weaneee ack enone eae | | UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 617 Fossils from the Upper Bagshot Sand (continued). : e : Byelearinee ye ae 3 S a i; o | Sues he & ry PAP a cis cee Bs jane 6 = 2 A] a =) PM mINENEA AEA. yi shdudate 17h. Peas twin lease Deatalinm Prande t.....1. 6. scvnecnionsdssdenoisekse * MUNIEFIL BGPUAUII © pes) sack. vonawcasiens ..2scecececeseen * * * * Berpuloides cancellatus .............02.cceeceseees * Nee - BPPMMERIME I Werodes cis. soon tts da latewess sont eig svecwanens Meyers acutiuscula .......h.ic..scneccsckbenscies ax! * POPMOPNOTA UMPIICATIS .......cccscccence cece ceeee = = * — PME CABAL s scseh dc sass sceckense snguiees sivas a — * — ear POrUlOSUM. «2.24... eta ee cde seude sence % — — — Memvamella COrONata...........seeccccceenesse cesses -— = = = MEPNIE BAIGAL.. 11 ...c#2hoa2hs udest do Wendees Sade. * = MED PAVAT CHIL, och ev action grins if waseeiied p van n= a * — msepila longirostrum ..........0.s-ssesebecesseeres = —- * SMI PEST, «2... occ beet \eninws + oMWile saenede cde % * x — Prapsabolla stuleata Po... cs .k lee uence cence cutee ae: a * — rene s (OD GUA ..2. 65628. iNaeee es sodas dad eevee = BEECH SB eo hands. 9 yn wes davenmmusieatvnd oot avecs nics BMS CLCP RNG 0.0. oa s-ncocieearsndocesesshetergenek ene _ iy oh * Wemocardium turgidum .............0.000...eeeees i + % ? Macula similis? ........ ... yb aeba suerte aaa ds ci ? ? * RMRRIE ROSAS E? OSES ds coca sin Wid wooed Seoeda cel RIMES TA CEI FO) cin d a> Jl. 4 ko wale obitin dls wrinpiowiele’s wer — — — * Pecten carinatus ...... Se ee ren Praca eee ie: — — re MEMEMU PECOMGUMS. fio... even toned tone selvrenewe das — Fee —- -—— ectunculus deletus.........0......ceceeeeeceteseens = “= — * Serieiila Rigauliiana: 0.2... 6.5 6 cedscessnteraee alle ae * Petia SCalariOIdes .........2-2.2-dee+sesecsseceenee * | Serpula. Corals, 2 species of Turbinolia. | | | t Not Barton, but found in the equivalent Sables Moyens of the Paris basin. 618 MESSRS, GARDNER, KEEPING, AND MONCKTON ON THE The preceding list contains 52 species of Mollusca +, for the col- lection of which we are largely indebted to Mr. Herries. Of these, 43 could be determined specifically, 9 generically only, and there was a considerable residuum which we were unable to identify. Thirty-one are common to the Upper Bracklesham and Barton, only 3 are absolutely unknown in the Barton, and there are 9 Barton species unknown in the Bracklesham. We must not attach undue importance to these, however, because a considerable distance sepa- rates Barton from Tunnel Hill; and we see that as far off as the Paris basin, many of what are our most distinctive Barton shells in Hampshire, such as Volvaria acutiuscula, Strombus bartonensis, Sola- rium plicatum, become distinctive of the Calcaire Grossier, and are quite unknown in the Sables Moyens, where we should expect to find them. On the other hand, we may instance Dentalium grande as a purely Bracklesham species in Hampshire, ranging into the Sables Moyens in the Paris area. If we take the * species, which are the most typical and abundant, we find that only 4 of those common to the two formations are more at home in the Bracklesham than — in the Barton, while the reverse is the case with no less than 28. Though more of the Barton species belong to the Lower than to either the Middle or Upper divisions of the formation, the Lower Barton facies is not so apparent as we should expect it to be, probably because the sandy bottom favoured species which could not exist in the muddy bottom of the Hampshire basin. Making allowance for this the paleontological evidence agrees with the stratigraphy, the presence of the few Bracklesham forms leading us to place the Tunnel- Hill horizon a little below that of Highcliff. Tue Barton Fauna. The fauna of the Barton Series is the richest in our Eocene, and contains probably more species than have ever before been met with in a single locality. The splendid preservation of the fossils and their striking character attracted attention in very early times, and the work by Brander in 1766 is one of the very earliest in which a large series of fossils was accurately figured and described. They seem to have been collected assiduously ever since, the recurring wash of the waves against the base of the cliffs exposing fresh specimens with every tide, whilst new crops of these delicate fossils seem sprinkled over the dark slopes between Highcliff and Hordwell after every shower. Prof. Prestwich was able to enumerate 209 species from Barton in his first paper, and in his second the number was increased to 301f, t Only 15 forms are given in the Survey list, in the “ Geology of the London Basin,” p. 600; and of these very few are determined specifically. At least 4 must be different from any in our list. t In ‘Geology,’ vol. ii. p. 369, Prestwich says ‘‘ The Barton Clay contains 310 species of Mollusca ’ and 28 of corals; “ Nautili have not yet been met with there.” 4 " UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 619 of which 252 were Mollusca. The collection of the Geological Sur- vey, as shown by their catalogue in 1865, comprised 182 species, whilst Morris enumerated 219. Prof. Judd, when writing of “the richly fossiliferous marine deposits of the Barton Clay at the base of the Fluvio-marine series ” remarks (Q. J. G.8. vol. xxxvi. p. 151) :— “So long ago as 1857 Prof. Prestwich was able to enumerate no less than 300 species of Mollusca from this formation ; and when all the known forms contained in the numerous collections in this country come to be described, the number of species from this deposit will probably exceed 1000.” A somewhat critical examination of the Edwards collection shows about 527 varieties of Mollusca from the Barton Beds entitled to specific rank, and we are not of opinion that this number will ever be greatly exceeded. Fossils belonging to other groups bring the fauna to a possible total of 600. The original basis of the tabulated list appended is the catalogue of the Edwards collection in the British Museum. To this we have added as much as possible on the one hand, whilst removing on the other all forms of doubtful specific value. In tabulating the range of the species, we have endeavoured to distinguish their occurrence in each division of the Barton Series ; and we believe that the long residence of one and the repeated visits of two of us to the locality, for the purpose of collecting, enable us to deal with the question of the horizons to which species are confined, with a practical expe- rience that it is scarcely probable any other workers have exceeded. Many, especially of the minuter forms identified by Edwards, are almost, if not quite, unique, and we have no means of ascertaining their horizons with certainty. We regard the record of some of the Barton species from other formations as doubtful, but do not sup- press them, as we have ourselves discovered several fresh Barton species in Bracklesham Beds whilst preparing this paper. We endeavour to obviate the inconvenience arising from giving extended ranges to species, upon the occurrence of stray and even doubtfully recorded specimens, by placing an asterisk in the columns under which a species is most at home. We have also endeavoured to separate species of the Upper Bracklesham Beds from those of the Lower ; and, though necessarily imperfect, this arrangement cannot fail to be of value in showing the passage of the fauna in a truer light than hitherto. A formidable obstacle was presented by the extensive synonymy in use. No less than 42 species from Barton, out of 182 in the catalogue of the museum at Jermyn Street, cannot be traced under the same names in Edwards’s list, whilst in the latest of the lists given by Prestwich 65 additional names of Barton fossils occur which are ignored by Edwards. Similarly we find 60 names in Morris’s cata- logue unrepresented, and 24 out of the 86 species recorded from the Barton Beds of Alum Bay in the Survey Memoir on the Isle of Wight of 1862. We have taken every precaution that no species should be omitted, but have not thought it necessary to state our reasons for changing or excluding names. Finally, we have not given MS. names of Edwards zn extenso, but have noted the number 620 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE of undescribed species under each genus. No doubt many of them have been described on the continent; but to examine each case critically would be equivalent to monographing the entire series of Barton Mollusca. We have contributed to the clearing up of the synonymy by exchanging as many species as possible with M. Coss- mann, who is now engaged in revising and supplementing Deshayes’s work on the Mollusca of the Paris Basin, and thus assuring ourselves that the correct names are in use. M. Lefévre, of the Société Mala- cologique of Brussels, has also kindly certified a number of the species for us, and we believe that the list, if not faultless, will yet be of considerable use to collectors. We have met with no record of the discovery of any Mammalian remains in the Bartons, though they are far from uncommon in the Lower Headon of Hordwell, except that of Zeuglodon by a coast- guardsman named Addow, on the shore, in stiff tenacious clay of the Middle Barton. It was purchased by Dr. Wanklyn, and has not been seen since his death some years ago. Fragmentary remains of Crocodiles and Chelonians are quite abundant in the lowest beds of Highcliff, but have not been deter- mined specifically. For the extensive list of fish-remains we are mainly indebted to Mr. Davies, of the British Museum ; most of them are the teeth and spines of Sharks and Rays, and the species, as a rule, have a wide range. ‘The Molluscous fauna is by far the most important, and may be divided into three great groups. That comprising the largest num- ber of species is peculiar to the Lower Bartons and occurs in the small pockets of fine grey sand known as the Highcliff Sands. Mingled with the fry of larger species is a great number of minute but adult shells, some of which occur in such incredible profusion that an ounce of the sand may contain hundreds of individuals of a species, whilst others are so rare that only solitary examples are known. The relative prevalence of the species varies in samples from different pockets, but by far the most abundant, Corbula pisum perhaps excepted, is Mitra parva,the next being Marginella bifido-pli- cata. Next come Bulla elliptica, Bayanza delrbata, V olvula lanceolata, Strombus bartonensis, and then, but in rapidly decreasing numbers, several other Bulle, Volvaria acutiuscula, Sigaretus clathratus, Ac- teon Cossmanni, Bayania rudis, Eulima goniophora, Marginella pusilla, Teinostoma dubium, and Adeorbis elegans*. Most of the remaining minute forms may be considered rare, but the fact that * The number of shells I have extracted from a single pocket, some 3 peck of sand, is as follows:—of Mitra parva 400, Bayania delibata 326, Marginella bifido-plicata 190, Volwula lanceolata 140, Orthostoma crenatum 138, Natica Noe, N. labellata, and N. perforata together 124, Buccinum Solandri 90, Strombus bartonensis 72, Bulla elliptica 70, Buccinum, sp., 58, Cerithium filosum 50, Acteon Cossmanni 41, Bayania rudis and Rissoa bartonensis each 40, Bulla conulus 37, Bulla pseudo-elliptica 20, Sigaretus clathratus 18, Actgon simu- latus 16, Volvula acuminata 14, B. angystoma 13, Eulima macrostoma 13, Num- mulites elegans 12, Ringicula ringens 7, Eulima munda, E. goniophora, Bulla anomela, B. Sowerbyi, and Acteon, sp., 4 each, Marginella pusilla and Nerita inornata 3, Bulla ovulata 2,and the rest 1 each. Corals 35. UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 621 they are entirely confined to a special horizon is no doubt due to the absence elsewhere of any similar pockets into which such small shells were drifted and have been preserved. A tiny coral and the fingers of small crabs’ claws are mingled with them in equal profu- sion. Many of the species are exceedingly like living shells from Australia and Japan, and seem to indicate a considerable depth of water with light drifting currents. Many rare freshwater shells are met with in this fauna, the larger of them being almost invariably abraded, as if brought from long distances. The second fauna is best represented in the Middle Barton, though few of the species are actually confined to it. The shells are of large size, and comprise the bulk of the typical Barton forms figured by Brander. Most of the striking ones are extinct, but others, such as Ficula nexilis, Cassidaria nodosa, and the species of Pleurotoma and Natica, are so nearly identical with living forms, that representatives of them may be said to exist. The third fauna is that of the Chasmpachede, comprising a number of exquisite and entirely distinct shells of moderate size, whose sud- den appearance is to be attributed less to an interval of time than to a change in the outfall of the river, by which the muddy water and silt of an estuary gave place to clear water and a sandy bottom. An enormous colony of Chamas and the ubiquitous Zurritella took possession of the area; but not the least remarkable circumstance is that the old representative species of several genera were suddenly replaced by others that, though quite distinct, seem closely allied. Thus Voluta humerosa replaces V. maga, Murex tripteroides super- sedes WM. asper, Typhis jfistulosus displaces T.. pungens, &c., while nearly the entire tribe of Pleurotoma give way to clear-water Cowries, Cones, Mitre, Murices, &e. The survival of stray and often water-worn specimens of Middle Barton species does much, however, to rob the Chama-beds of the peculiar facies of their fauna when tabulated, and renders the break far less apparent than it actually is in the field. The fauna from the Long-Mead-End Sands is again very distinct indeed in its general facies from those which precede it. Its most noticeable feature is the large proportion of Cerithia and of Oliva Branderi. It possesses a peculiar Natica and Marginella, and species of Melania and Melanopsis similar to those of the Headon Beds above, while, owing probably to an influx of brackish water, the whole group of Volutce, Pleurotome, and Murices so characteristic of the Lower and Middle Bartons have disappeared. About a dozen of its com- monest species are, in fact, indicative of brackish, if not of fresh water, while an equal number of hardly less abundant, truly marine forms pass up from below. The list of Barton fossils comprises 23 Vertebrates, 47 Invertebrates other than Mollusca, 257 Gasteropods, and 150 Bivalves, exclusive of over 120 undetermined species. Twenty-eight of the Mollusca first appear in the London Clay and range for the most part above the Lower Barton, though 7 of them are absent in the Lower and 3 in the Upper Bracklesham. A further 37 species first appear 622 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE in the Lower Bracklesham, only 11 of which do not range above the Lower Barton. These are reinforced by no less than 108 additional species in the Upper Bracklesham, 35 of which die out with the Lower and 24 with the Middle Barton. Thus of the 407 species, 175 range below the Barton, against 56 that pass up into the Headon; but of the latter 30 are also Bracklesham and London-Clay species. The upper limits of the Barton formation are thus much more sharply defined, paleontologically, than the lower ; but we must remember that in the former case the passage into fluviatile beds is abrupt, and the marine beds next above are separated by a considerable thickness of freshwater deposits, while in the latter the transition lies everywhere in marine deposits. The reason for drawing the line between Oligocene and Eocene in our area, here if anywhere, is quite obvious if our statistics are at all reliable. The close connexion between the Upper Bracklesham and Lower Barton is rendered very striking by these tables, no less than 35 species being quite peculiar to the two horizons when combined. This contrasts with the 12 which are peculiar to the Lower and Middle Barton combined, and the less than half a dozen peculiar to the combined Middle and Upper Barton. The upper limits of the Bracklesham should obviously, on paleontological data, have been drawn much lowerdown. Only 16 are peculiar to the Upper Barton and Headon combined, and these are mostly freshwater or brackish- water stragglers. Of the tabulated Mollusca, 124 are absolutely peculiar to the Barton formation in this country, though we must not lay undue stress upon them, as we have seen that many of those most rigidly limited in range in our area have a more extended or a different range in the Paris area. Of these, 15 range through the three divisions, 12 through the Lower and Middle, 5 are confined to the Lower and Upper, 3 to the Middle and Upper. This somewhat capricious dis- tribution may be partly due to the extra turbidity of the water in the Middle period. There are 51 species absolutely confined to the Lower, 10 to the Middle, 28 to the Upper divisions. The distribution by genera is equally instructive; but in order to have made an analysis, we must have introduced subgeneric names, which would have lessened the value of the list for general comparison. We have for the same reason retained many familiar generic names which, on the ground of priority, must disappear. The general resemblance between the facies of much of the Barton fauna and that of the London Clay is net apparent in the table, perhaps because species which did not hold their ground during the Bracklesham period, but emigrated, were so considerably modified during the interval that they can be distinguished as new species on their reap- pearance; while the modifications undergone by those that remained were so slight that in the presence of connecting links they are specifically inseparable. If we confine our attention to the species whose range is marked UPPER EOCENE (BARTON AND UPPER BAGSHOT FORMATIONS). 623 by * in the table, we find, excluding a few cosmopolitans, that 7 London-Clay or Lower Bracklesham and 32 Upper Bracklesham species merely straggle up into the Barton formation, only 7 or 8 actually belonging as much to one as to the other. There are 85 distinctively Lower, 39 Middle, and 50 Upper Barton species ; only 3 or 4 species distinctive of all 3 stages, without being distinctive of any beds other than Barton; and only 2 distinctively common to the Middle and Upper stages alone. There are 13 characteristic Yeadon species in the Barton and only 5 that belong equally to Headon and Barton without passing into the Bracklesham. Vertebrata. The species which have all the columns left blank are from the Barton Series; but their precise horizon is not known. | London Clay. | Lower Barton. | Upper Barton. Zeuglodon Wanklyni, Seeley ............ ae MEET. Ciicioneuninadeevvereces sxeree NE LN ia dpc so ser + Recorded by Agassiz, but not since authenticated. Q.J.G.8. No. 175. QT 624 MESSRS. GARDNER, KEEPING, AND MONCKTON ON THE Invertebrata. The x in the columns denotes where : : the species is most at home. Thet a 2 ie ; prefixed to a name indicates that} 5 | 7% |m| 8 |9 1] 68 the shell is unique. The species} © | 8] 8/8 | 81/4 which have all the columns left S Sila lis /A8la : blank are from the Barton Series ; oS eB lense |ie ae 8 but their precise horizon is not til) SE Ph coe E = Bi FS known. HAP lAlsale l/s Nautiltis, Sp. 571g-a:c0eesseenn ceases eee eaes —j|;— |? fPedipes plaber, 2d 10. 2a. Jonc52-eeceecas = Cyprea bartonensis, Edw. ............4. * Trivia platystoma, Hdw. ...............0.- eS | ae. | dee Marginella bifido-plicata, Charlesw. ...| — |... | — | * | — Teracilis, Pwd a. oiact cpesvoawncnas On Were eee | — —— pusilla, HdW. ...ccsccsecerecencoecee vas) loe—s | eine Sineplex, PW. be feiewaansonatnncemnsen oss | aso | ce | seen Voluta luctatrix, Sol. ........ BEE tateteesiee aes | woe | coe | amibigna, 00." 4.5. .deescence << cosas] com | tas | ee (an — , var. subambigua ............ wos | wee | onc | cee) Geen === modosa, SOM | sass 2G teton.tenase es eee ee Sabri WSOUs Mere ee ck woe | aus | oes | Gece an SPINOSAy FGI. Sek oc cncdedsea gedeas ec vee face | H | — | — ———— , var. depauperata, Sow....... woe | ose | coe |) Geen enn en — scabricula, Sol. .......ccceceeceeeees 2 — ee ———= SolandPi; Bw. saciess cicccsesnasnseeds wee | es Pace | =e abhileter, Ole = 2 s6*t. sweeten ooeicans oo | — | — | x | — ——_ maga, Edw. .......cccccccceeeseseeeees coe [ eee | & | — | —] oe | — BUGPCUAA, DOL. co! Sag.c8e~ -wacesocscuee vee: |i sase «| oes. ea decora, Beyr., var. maga, Edw.....|-.-.-|.-- |... | 20a ee lhumerosa; Haw. n.250.0885scs. ect wis | poe fcc er IS] ets OU Cob] RS Se eo Se a ee n dns dines «| oa0 lee te TMitra volutiformis, Edw. ............... oe eee eee —— ROA NTA A ISO Uc seet abacus estes sen <8 eta: di sens 2] nec Steet ee PBEM, OU, cence ssaec node tne saeekee = | see |e. | A968 ee ——— fusellinns Tan. sk soe escde s daccne Sores Wee eaey es oe | = Tobesa; Haw: }. ste. o.<< Boece he See ree Poe = Conus seabrienlts, Sol | issccceseesuses ces ose. .| ae sec | eee df hee hordenced, Trai <1. 6. caacdebeteseces wee | eee | — | —] oe | * Melanopsis sigillata, Edw. ............... ani vali asa ll ve ——- fusiformis, Sow. .........cs00e-00 « col wae | ses, Jewel |) Goo enenn tee amninEn Littorina suleata; PU. ..sescccvcteasees ee f — | a | ee subangulata, Desh. 2c. ...c..cacsscses Joe.) a Lacuna, ep: . |e Se. 5s cb sasca- enesevee cos. | -aee ieee) Ae (and 8 other rare species). Styliter; Bp. pu tiacesee monster decweresuans sins .|) 3a See ae PRISSOUIH, BD, Wow c en tecnennbaccesdegecsoseok Lao fides’ Hl ae (and 3 other species). Rissoa nana, L070. \vcc1.- 0.205 0de000s .ovnes ere ese * bartonensis, OTS sa bs na srcun scene %. Ss —— carinata, Charlesw. ......0..ccceeeeee sisi alate = ¢eo8e _ BPO: Tn haunt vtec aver snet ob eda cites Leet nice el ce a eat (and 4 other rare species). Hydrobia anceps, 8. Wood ............++- ase | eee | eee | 3 | ee BextOnus, DESI, Roce cat chossrcsiwoe wivina| dd he pe ge Truncatella“sp.. ©... ore. wasiew | Se mine a ROMRUIENT DOW. lag vice ceveweenestaces —|... % bee | Ringicula ringens, Lam. ........ pitateasss * | * x — Volvaria acutiuscula, Sow, .............6- sia % IMRT IGS Gidedwcacscpsesesssavadsarads asas|v-ane. [ieee (eamau eat Balla attenuata, Sow. ........0.cccceceveee ——, | =. 1. — haan [PB * | * — Sowerbyi, Nyst .......ceceeeeeeeeees we | — tf —] * | * ——- comstricta, Sow. .........scececeseees aye | van Stage ne A — elliptica, Sow. ...........cccecescssees vee fiver | — | * | HP —]| pseudo-elliptica, Hdw.............06 Pr as eT PMOGGCtA, LAW. - i oincccssesseessanees sepa ais — GMS yetOMA, Desh.....0cccccnevescseres * —— conulus, Desh, .......ccccccecsscevess -_ oh le 3) ene idgt ene daca Serrinna. bea els em it — Lamarckii, Desh. ................ 0.008 adits Ea —|— SRM elas o itdar occa sev ecnes svaiccns's * PCC ERE. Svelodeccecss cons Bilan nivel votdagellieleies So OE HE Volvula lanceolata, Sow. ..,.............08- .. | — | — | * P}— acuminata, Charlesw. ....00......0.. 6 hee ? Acera striatella, La7.......0c.ccseccssecees * Seaphander Defrancei, Sow, ............ * — ge dade cies Nenenssascisvveteuess x RM Tha isshienavossccsadsdecavesacneds oP oe ee lind * Dentalium pellucens, Desh...............5 rr ee ee Te a a | —}]—}]—]*« ] Anomia tenuistriata, Desh. ............... x |—{—]|—]|—]«*«}]— Ostrea oblongata, Sol...............c.-e00s .. | —}|—}]—| * 1G 2S 7) eaeeeits —}|—|;—|—t]—] «#f— miganten, Sol.) .......00c0s0 Bisle elects —|—| * Vulsella deperdita, Lam? ...........05 wiet:t nusp pk waea [eo Af eiktoah ae de PPGCten COLNEUS, SOW, © ....cccsecccceerenese Skee Si ee ee carinatus, Sow.......... pacheeenvanete a . |—|—] * — reconditus, Sol. ...........6. sistas —|.. | — | — Emma compta, S. Wood ......ccec.sscene PRED E Se TV OOD sco ccsvnccseces ewan oaicien Avicula media, Sow.......... psec rarcnacaenas *}/—!|—|]—]|—|] «le Pinna margaritacea, Lam. ............6- 3 | Be Fig, 3.—Section of the Melkote Arca in the line A-B on Plan, fig. 2. For explanation of symbols, see fig. 2. Narasimha Temple * The white clay is called by the natives “ nama” and is used by all the Sri Vaishnavas of that region for painting the sectarian mark (Brah- man) on their foreheads, and some of it is also sent for the same pur- pose to Kasi and Benares. 2 = MW, MYSORE PROVINCE, SOUTHERN INDIA. 639 rocks. A band of mica-schists again appears, which gives place to a fine-grained gneiss-rock dipping nearly vertically. Mica-schist dipping to the west is followed by a hard hornblende-schist, which dips to the east, and then fine-grained gneiss accompanied by a broad band of mica-schist comes in, giving place to hornblende-schist, followed by a mixture of narrow bands of mica- and hornblende- schists, quartzites, quartz-veins, a band of eclogite, and some talc- and chloritic schists. The schists are now replaced by schistose gneiss and gneiss similar in some respects to those found at the commencement of the section. The only difference is in the gneiss being much more finely-grained and more regular in its foliation at the east end of the section than at the west. Having briefly named the different rocks met with in the Melkote Area, I will describe in some detail a few of the important ones, referring for the full microscopical description to the Appendix by Prof. Bonney (p. 651). On the north bank of the Lokapavani River (see Plan, fig. 2) there is a band, some thirty feet in thickness, of a hard, compact, greyish rock, containing numerous reddish-coloured garnets, and with a com- pact base showing green hornblende. ‘The rock is most difficult to break with the hammer, and the only garnets obtained in a fair state of preservation were those found close to the hornblende-schist which adjoined it. The rock may be called eclogite (Rock-section no. 1, p. 651), and it was found to have a specific gravity of 3:22 and by chemical analysis to contain 59:14 per cent. of silica. The qualitative analysis showed it to contain only a small quan- tity of iron as well as of alumina. The area occupied by the eclogite is limited, so far as the author’s observations went, as it could not be found south of the river, and only about one third of a mile to the north of it. Hornblende- schists occur in both wide and narrow bands, and they were examined with considerable care as well as interest on account of the name Fig. 4.—Top view of Quartzite, showing Slickensides. of trap being locally applied to the rocks. The hornblende-schist avec. 5. No. 175. 2u 640 MR. G. ATTWOOD ON AURIFEROUS TRACTS OF varies from black to greenish-black and dark grey in colour, very compact (see Rock-sections, nos. 2 and 4, p. 651). The hornblende is green, and the felspar generally plagioclase. The specific gravity of No. 4 was found to be 3:19, and it contained 49°85 per cent. of silica. The qualitative analysis showed the rock to contain a small quantity of organic matter, a fair percentage of iron-oxides, with a little alumina and a trace of manganese. Mica-schists having a soft silvery as well as yellowish appearance are abundant in the Melkote Area. The general strike of the mica-schists is about N. 20° E.; but the dip, as willbe seen by the section, fig. 3, varies from east to west, and at the east end of the section the dip is nearly vertical; but at the same time the strata are very irregular and much contorted. Evidences of great crushing-movements are seen by examining the slickensides on the bands of quartzite (fig. 4). The bands of quartzite are narrow, being from 5 to 20 feet thick, running parallel with the schists, and they have also the same dip. Large masses of vein-quartz were also found scored, and with their surfaces showing slickensides. The direction of the crushing-movement appears to be nearly vertical, from the slickensides on the quartzites and quartz 7 situ. However in some parts of the section there are ~ evidences of horizontal as well as lateral movements. In one case in question the lateral throw was found to be about 60 feet (fig. 5). Fig. 5.—Plan showing lateral displacement of Quartz-vein. —TThKhT—T————————— —eee——SSS ———SSSSHSEESESEESHHLSSSSS55 SSS ———————————— = —> —SSaSSS=_ ——— ————— : a. Quartz-vein. 6. Schistose rock. In the mica-schists, especially the soft silvery-looking schist, crushed garnets of different sizes were found, varying from one inch to one tenth of an inch in diameter, and flattened out to a great extent (figs. 6, 7); for instance, a garnet of 3 of an inch in diameter would be only 2 of an inch thick in the centre at its widest part. MYSORE PROVINCE, SOUTHERN INDIA. G41 Fig. 6.—Section of Mica-schist, showing flattened Garnets. To assist in indicating the appearance of the garnets two drawings * (Pl. XV.) were made from the slide (Rock-section no. 3), and the author has also made a chemical analysis of one of the garnets. per cent. piiea ..... Sh i eG eo thine pees ee 49-50 eam PROtORIde TT sets cee a bn ie ee 36°25 PEIN NER e asin, Meme RN thse. Com a ceineiies eh 6°25 PRE ccs he ie ok cies: =p he ee Sey, es RPA MOBT Ar 6. ahs) 5. 6 cucinnsw a» ogee ait eae 1:44 Menpanese . . ). 2. OR lee 2 wee 1:76 Hyeroscopie water’... 2)... oe ee 0°37 Combuned water... 40. Jas 3:20 Specific gravity, 3°64. 100-20 From the above analysis, as well as from the microscopic exami- nation, it is an iron-alumina garnet, probably in its original state * The author is indebted to Mr. Felix Oswald for making the above drawings. 202 642 MR. G. ATTWOOD ON AURIFEROUS TRACTS OF “almandite.” The excess of silica in the form of crystalline quartz found by the microscope was confirmed by the chemical analysis. . At the east end of the Melkote Section a very hard, crystalline, eneissic rock is seen, standing, in some places, from 30 to 40 feet above the ground, and above the banks of the Lokapavani River. The rock has a light grey colour, and contains quartz, mica, and felspar (Rock- section no. 5), and has all the appearance of belonging to an ancient series. Small bands of tale- and chloritic schist* are abundant at the east end of the section, as well as small quantities of hematite and magnetite. A few pieces of coarse corundum were picked up on the surface. In traversing the Melkote Area and also most of the schistose bands on the Mysore plateau a deposit is met with which is some- times found in the nullahs (water-courses) on the side hills on masses of broken quartz (the detritus of ancient alluvial gold washing), and also in excavating below the surface where the ground is more or less soft and covered with alluvium or contains fissures and crevices. The native name for the deposit is “ Kunker.” The deposit was found to be a calcareous one, generally of a dull and ereyish-white colour and of a nodular and botryoidal form. A piece of the deposit was selected for analysis and afforded the author the following results :— Per cent. Combinations. Silica th. cae eee ee Las 7-00 Carbonic acid ........ 40-7 Linte geek ck be tien oe 48°53 CaO, CO, . 86°66 Magnesia ~4-2is..c ae. oe bh Mg0,CO, .... 26p ASWGESS Cn cate ws Sek 0-13 Iron protoxide...... 170 FeO, CO)... ae P OtaSr oe eae eee 0-13 KO, CO) eee SOU ye om ca earapa eee 0-176. NaO, CO, 1) ae Chlorate. 2 sue sss @ oss trace SulphoR gig oe aces trace Water (ssh. oP eec 041 99-726 Specific gravity, 2°81. It is not unreasonable to suppose that the lime contained in the deposit is derived in a great measure from the hornblende-schists, as the latter contain from 7 to 20 per cent. of lime, whilst the mica- schists are almost devoid of it, and even the gneiss seldom contains more than 2 per cent. of lime. Lime contained in rocks which are exposed to a tropical sun weathers away rapidly. An analysis of a hard diabase rock from South America showed the unaltered rock to contain 9:65 per cent. of lime; a portion of the same stone weathered contained 4-98 per * The natives call all stones of the magnesian order which have a greasy or soapy feel “ Balapam,” and they use the stone extensively in the construction of their iron- and steel-furnaces, and also in their dwellings. MYSORE PROVINCE, SOUTHERN INDIA. 643 cent., and the outer layer of the same stone, which was highly weathered, was found to contain only 2°37 per cent. of lime *. Quartz-outcrops as well as detached pieces of all sizes are plentiful at the east end of the Section ; but a critical examination of most of the outcrops led to disappointment, as the majority of them were found not continuous when examined below the surface. About one outcrop in ten proved, after exploration, to represent a true quartz-vein of strength and permanence. Many of the outcrops are large at the surface, but when intersected 15 to 20 feet below, they are found to diminish in thickness and in some cases disappear altogether (fig. 8). Fig. 8.—Scetion showing downward attenuation of Quartz-vein. | Vii Wine Mili a. Quartz. Bea At ie, Men Ls Sahin Schistose rock. Upon an examination of the rocks where the Lokapavani River cuts through the hill, no quartz-veins were visible at the river-level except small stringers ; although on the hills above large exposures of quartz, from 4 to 15 feet in width, are observed, which, if con- tinuous, would be intersected by the river. The same feature was observed where precipitous ravines intersected the hill-range. The schists are bent, contorted, and squeezed to a great extent, and the quartz-veins generally lie between their strata and have the same strike, about north 15° to north 20° east. One quartz-vein of some 4 feet in thickness, lying in hornblende-schist, showed peculiar faulting, having been thrown twice in a height of 30 feet (fig. 9). Extensive gold-washing (or streaming) has been carried on during ancient times in the ravines and on the hill-sides of these schist- rocks ; and from the large heaps of waste stones, consisting chiefly of broken quartz, the workings must at one time have been productive and most likely remunerative. After washing the alluvium and detritus found in the ravines and nullahs in a miner’s cradle (or rocking-machine), also in a Batéa, small grains and nuggets of gold were found in most instances, and they were mixed with particles of magnetite 7, hematite, fragments of garnet, quartz, &c. The grains of gold examined under the microscope werefound to have a flattened or a somewhat imperfect crystalline form, and when very irregular in shape were found on their surfaces to retain in crevices and hollow places small crystals of magnetite, which appeared to be attached to the gold by a siliceous coating of ferruginous matter. Most of the gold-grains were partially covered with the above * See Geo. Attwood, “ A Contribution to South-American Geology,” Quart. Journ. Geol. Soc. vol. xxxv. p. 586 (Nov. 1879). Tt Commonly called ‘‘ black sand” by the miners. 644 MR. G. ATTWOOD ON AURIFEROUS TRACTS OF coating, and in that respect they resemble gold nuggets found in the district of Pastora, Venezuela, South America *. Fig. 9.—Section showing double faulting of a Quartz-vein. a. Quartz. 6. Hornblende-schist. The gold has a bright gold-colour with the exception of its outer coating, and appears to be of great purity ; by comparing it with other gold grains of a known fineness, it will be about = fine. From the field-examination, assisted by the microscope and chemi- cal analysis, itis highly probable that the gneissic rocks, as well as the hornblende- and mica-schists, also the quartz-veins which accompany them, belong to the very old series of rocks called Archean. 2. Serengapatam Area. The second Area is in the neighbourhood of Seringapatam, district of Mysore (see Plan, fig. 10). The line of section takes a south-easterly direetion from the 72nd milestone on the Seringapatam and Bangalore road to the north-west side of the village of Arakere. Gneiss-rock, rather coarse-grained, is followed by a schistose gneiss, which gives place to mica- and hornblende-schists. The general strike of the gneiss- and schist-rock is about north 20° east, and the dip various, as seen in the section, fig. 11. The hornblende- and mica-schists have a sharp dip, nearly vertical, whilst the gneiss-rocks gradually slope away until they recline at an angle of about 35 or 40 degrees. * See paper “On a Gold Nugget from South America,” by Geo. Attwood, Journal of the Chemical Society, July 26, 1879. 645 MYSORE PROVINCE, SOUTHERN INDIA. “ig. 10.—Sketch Plan of the Seringapatam Area. f C ARAKERE re) SAS) KASALGERE AN) DAGCEMANPALYA MARLAGAL 2°25 “WVLVdV9 Y NIAAS OL —B Fig. 11.—Section through the Seringapatam Area in the line A on Plan, fig. 10 pS a> aPAK > d>5> > 3S 7) @ “a a So n t o ine) = o = wo} 3 ~ I -veins. Ras Quartz Schistose gneiss. | Porphyritic dykes. YJ, Mica-schist. 646 MR. G. ATTWOOD ON AURIFEROUS TRACTS OF At the south-east end of the Section numerous quartz-outcrops are found, varying from 6 inches to 5 or 6 feet in thickness, and the surface is more or less covered with pieces of broken quartz. Good crystals of schorl were found in some of the detached pieces of quartz. The majority of the outcrops show very hard, white quartz and scarcely any pyritic matter. One promising quartz-vein was opened on and named the Elliot lode. It was proved for about 500 feet in length and over 60 feet in depth; the strike was nearly north and south, ard the dip varied four times in 60 feet, and eventually went off to the west, at an angle of about 65 degrees. Near the surface the wall-rocks of the lode were much decom- posed and not well defined ; but from 30 to 60 feet below the surface they were found to be hard and compact, well defined, and to consist of mica-schist, highly quartzose. Free gold was found in most of the vein-stone, accompanied by arsenical and iron-pyrites, and occasionally a little copper-pyrites. The micaceous wall-rocks were found to contain small guantities of gold, whilst the vein-matter itself was rich in gold. The gold was not always found in the quartz itself, but frequently in the cleavages—the latter being more or less filled with iron- and arsenical pyrites. Under the microscope the goid grains obtained from washing the pulverized quartz showed crystalline forms, but not perfect, and the grains were covered in most cases with a coating of siliceous matter, sometimes highly ferruginous, but often almost free from iron-oxides, and frequently quartz-crystals were observed firmly attached to the gold-grains by the siliceous coating, and also in the crevices, or held by claw-like gold protuberances. In ancient times the Elliot lode was worked extensively, and the old workings were found to extend several hundred feet in length by some 55 feet in depth. With the exception of a few pillars of quartz to keep the walls from closing in, all the vein-stone had been taken away by the ancient miners, and the space filled up with waste rock. The mine was discovered by an accident, as all the workings were filled up close to the surface and that covered with vegetation ; a depression on the top of the hill led to work being commenced and to the discovery of the ancient mine. The quartz-rock was very hard in the lower portion of the mine, and the old miners must have had considerable difficuity in breaking it up. Human remains and pieces of charcoal were found in some of the old workings*. It is probable that the old miners used charcoal fires and then water to decompose the rock before breaking it with their tools. Large heaps of waste quartz-fragments were — found near the water-springs in the ravines, some hundreds of yards from the mine, and gold was found in most of the ravines by washing the sands and alluvium. On the hill near the mine, wherever the exposed rock-surfaces were hard and compact, the natives had made holes to act as mortars * Mr. J. C. Butterfield and Capt. Thos. Kitehen found the bones and char- coal after my departure. : Land MYSORE PROVINCE, SOUTHERN INDIA. 647 to grind their gold quartz (fig. 12). The holes were about 8 inches in diameter and about 4 inches deep. Fig. 12.—Section of Rock-mortar in Schistose Geiss. Some exposed surfaces had as many as twelve or thirteen mortars, while in other places only two or three were observed. The rock in which the mortars were formed is a schistose gneiss (or a gneissic mica-schist), tough and hard. It appears likely that the old miners crushed up the partially calcined quartz in the stone mortars * and then carried the powdered sand to the water below and separated the gold by washing in wooden vessels. The following sketches (figs. 13, 14) represent two forms of gold-washing vessels used by the natives at the present day, and they are not unlikely to be somewhat similar to those employed in past ages, as mechanical appliances in Mysore are not subject to daily improvements as they are in the western countries. There is no evidence about the after-treatment, but on account of the gold consisting, in many cases, of very fine particles, some means of collecting it beyond washing must have been adopted. Fusion of the concentrated material with lead was probably the method employed in ancient days, and in more recent times amalgamation by means of mercury. Several other promising quartz-veins were found at the south-east end of the Seringapatam Section, which may lead to further explora- tion. In the northern part of the section the quartz-veins are composed of hard white quartz showing little or no pyritic matter, and apparently devoid of mineral, whilst at the south-east end a great change in the quartz-veins takes place. Pyrite, chalcopyrite, and arsenical pyrites are found, and the vein-stone contains large quantities of iron-oxides, and is more or less banded or divided by seams, while the quartz is of a finer grain, entirely different from that at the north end of the section. At the south-east end of the section (see Plan and Section, figs. 10, 11) the schists are much broken up and disturbed by porphyritic dykes. One of the strongest of the dykes was more than 20 feet wide, and had a strike north 80° east (Rock-section no. 8, p. 652). The rock was of a darkish grey colour, very hard and compact, showing felspar- * Quartz would be very friable if, after being exposed for some time to a charcoal fire, it had water thrown over it whilst heated. 648 MR. G. ATTWOOD ON AURIFEROUS TRACTS OF crystals, also pyrite, specific gravity 2°83, and was found to contain silica, 60°71 per cent. Fig. 13.—Sketches of a Halagay or Gold-washing dish used by Julgars (Gold-washers) in the Shimoga District, Mysore Province. (Seale 1 nat. size.) a. From the side; 0, from above. Fig. 14.—Sketches of Dhone or Sluice-box used by Gold-washers m the Shimoga District. (Scale ;4, nat. size.) > LZ Z Z LLL N a. From the side; 6, from above; c, end view. Another porphyritic dyke (see Rock-section no. 6, p. 652) showed considerable signs of weathering; the colour was a light pink, the strike nearly northand south. ‘The specific gravity was found to be 2°83, the same as that of its harder-looking brother. A specimen taken from another porphyrite, having a strike nearly east and west, was found to have a specific gravity of 2°84, and to have a dark-grey base, with the felspar-crystals chiefly pink and glassy. Another porphyrite (see Rock-section no. 9) had a dark-grey { colour, and was very compact and difficult to break, resembling in a great measure Rock-section no. 8. MYSORE PROVINCE, SOUTHERN INDIA. 649 The porphyritic dykes are of recent origin and most likely of Tertiary age, whilst the gneiss and the mica- and hornblende-schists belong to the older series called Archean. At the south-east end of the section a small granitic dyke, having a strike about north 30° east, intersects the Elliot lode diagonally. The dyke is about 10 feet thick, and consists of a coarse-grained granite, with fresh-looking quartz-crystals (in places an inch square), light, pearly, almost transparent mica, in thin folia, and large felspar-crystals of a dark cream-colour. The granitic dyke cuts elean through the Elliot lode, but only throws the lode for a few feet, so far as the underground explorations went. The dyke will therefore be of more recent origin than the porphyrites (and probably Upper Tertiary). Some three miles to the south-east of the above, Mr. Walter Marsh also observed some large exposures of a coarse-grained granite, somewhat similar in structure. 3. General Observations. In the Plan, fig. 1, there will be seen three districts marked as hornblende-, mica-, and cale-schists, containing quartz-veins, which have been visited by the author. On the west of the plan a large area of land extending from the town of Banavar to the south-east of Honsur Town, a distance of some 45 miles, is marked as being composed of the schistose rocks. Starting from Banavar and travelling south towards Honsur, the schist-band is almost continuous, and on the east and west sides are found the gneiss rocks. Extensive old gold-mine workings are met with at intervals nearly all the way, although at the time of my visit no active work was being carried forward on any of the mines. Mr. Bruce Foote, F.G.8., of the Indian Geological Survey, who has lately visited the above district, and has issued a Report on the same to the Mysore government, calls the schistose rock-series “ Dharwar Rock,” and says: ‘“ Two years ago I gave the name of the Dharwar System, from the fact that the rocks forming it occur very largely in the Dharwar country, and that there I first recognized the necessity of separating them from the great gneissic system with which they had till then been grouped” *. To the east of the Banavar and Honsur schist-bands another band occurs, which has been described at some length in the previous sections, as Messrs. Foote, Lavelle, and Marsh had not examined it fully at the time of my visit. About 45 miles to the east of the City of Bangalore another schistose series occurs in what is called the Kolar district. In the above series are found some of the best gold-mines in Mysore, viz. Mysore, Nine Reefs, Nundydroog, Gold Fields of Mysore, &c., &c., some being worked and many others still lying idle. During numerous traverses no quartz-veins carrying gold were found in the gneiss-rocks. * See Selections from the Records of the Mysore Government, 1887 : ‘Report on Auriferous Tracts in Mysore.” 650 MR. G. ATTWOOD ON AURIFEROUS TRACTS OF In prospecting for gold in Southern India one feature of especial interest was observed, that is, the general absence of alluvial depo- sits rich in gold; this and the absence of ancient river-bed gravel containing gold make it evident, after inspecting the auriferous lands of other countries, that the natives have years ago extracted the metal, and they have also tested with care the various outcrops of quartz in their search for gold. The ancients were by no means inferior miners, to judge from the author’s experience, as he never found gold in a single place or rock where the old miners had not left indications to show that. they had worked before, although several hundred tests were made. Therefore where the ancient workings now exist will be the most likely places to find gold in paying quantities; and that it will be found by searching, and that the gold-mining industry can and will be carried on profitably, the author has no doubt. The quartz- veins lying in the schists, which are naturally of irregular form, bent and twisted, will require, however, the services of skilled engineers and miners to follow them. About 10 miles to the east of Gubbi (40 miles east of Tiptur, see Map, fig. 1), in the centre of a large gneissose area, a rock was selected for microscopic examination (see Rock-section no. 10). The rock was fine-grained, with a pink tinge, and consisted of quartz, felspar, and mica, and in situ showed distinct foliation and may be called a gneiss. Prof. Bonney remarks that its structure “ recalls that of the Archean gneisses rather than of the normal granites.” The author has been much struck with the paucity of granite compared with the immense tracts of gneiss which are found in Southern India; and many rocks called locally granite, upon examination have been found to be un- doubtedly gneiss. A general examination of the strata on the Mysore plateau shows that immense pressure has broken up the gneissose rocks, and also compressed the mica- and hornblende-schists; and it is not unlikely that the above disturbance and breaking-up of the gneissose beds was caused by the gradual rise of the eastern and western ghats, which would create great pressure on the strata forming the Mysore plateau which lies between them. The Mysore plateau shows evidences of having been subjected to extensive denudation, from the absence of the later formations and the exposures of gneissose and schistose rocks, and from many masses of gneissose rocks (in some cases solitary) standing above the plain at a height of from two to eight hundred feet; also the hardest of the hornblende- and mica-schists often remain in the form of small hills or mountain-ranges above the level of the plain. Having now come to the end of my notes, I shall conclude with an acknowledgment of the great assistance I have derived in my work from Prof, Bonney’s microscopic researches ; and I may say, further, that Prof. Bonney, without having been on the ground or seen the results of the chemical analyses or the large collection of rocks brought home, has, with the microscope alone, read the whole story just as well MYSORE PROVINCE, SOUTHERN INDIA. 651 as if he had been over the ground himself and had had tho benefit of the analyses. Nort on Specimens from Mysorz, collected by G. Artwoop, Ksq., F.G.S. By Prof. T. G. Bonnzy, D.Sc., LL.D., F.R.S., F.G.S. 1. Rock consisting of reddish garnets, very irregular in their outline, ina greenish-grey crystalline matrix, with brown weathering. Apparently a variety of eclogite. Microsc.: consists of garnet, quartz, felspar, hornblende, iron-oxide, rutile (?), andafew grains of a honey- yellow mineral. The garnet rarely shows a crystalline form; often it encloses grains of other minerals, chiefly quartz; sometimesit forms with them a kind of granular aggregate. The felspar is to a great extent replaced by secondary products, but some small grains of plagioclase are well preserved. One of the larger (rather decom- posed) grains encloses quartz granules. The hornblende is green, sometimes rather dark, showing very characteristic dichroism and cleavage. The yellow mineral mentioned above is not abundant, generally granular in form, but in one case prismatic ; here extinc- tion seems to take place at a small angle with the larger edge. The dichroism is not strong, and there is moderate chromatic polarization. It may be a variety of epidote; but I am uncertain. From the general structure of the rock, it appears to me to have formerly under- gone mechanical disturbance, but so long since that there has been a practical recrystallization of constituents, 2. e. very few distinct indications of crushing now remain. Therock rather reminds me of a variety of eclogite which I collected at Wahnapitae, on the Canada Pacific railway. 2. The rock in the hand-specimen appears to be a slightly foliated, dark, hornblende-schist, containing some very small garnets. Under the microscope it is seen to consist of green hornblende, quartz, plagioclase felspar, garnets (very irregular in outline), hematite (?), and a little biotite. The rock is now a hornblende-schist, but it is by no means improbable that it may have once been an augitic rock of igneous origin, modified by pressure and consequent mineral changes. 3. A flattened anaes in a fine-grained quartzose mica-schist. Under the microscope more or less ‘granular garnet is curiously associated with clear, crystalline quartz and a little white mica, in a way almost impossible to describe, but which may be understood from the illustration. Parts of the slide are slightly stained with limonite. I have no doubt this is from a garnet-bearing mica-schist, which has been subsequently crushed and has then to a certain extent recrystallized. 4, A rather compact hornblende-schist. Under the microscope it bears a general resemblance to No. 3, except that there is rather more hornblende, less quartz, and the species of the felspar is less deter- minate. The same remark applies to the following specimen :— 5. A light-grey, crystalline, gneissoid rock. Under the microscope it consists of quartz, felspar slightly decomposed, biotite (sometimes 652 PROF. T. G. BONNEY ON SPECIMENS FROM rather altered), with a little white-mica, epidote, sphene, iron-oxide, and apatite. The rock appears to have suffered from mechanical disturbances, probably at no recent epoch; but its anterior structure is, I think, commonly well preserved and much resembles that which usually occurs in the old gneisses, to some of which this rock has a macroscopic resemblance. 6. A pinkish, somewhat porphyritic felstone. Microscopic exami- nation shows it to be a porphyrite, with devitrified ground-mass, the larger felspar-crystals (plagioclase) being rather decomposed. There is nothing noteworthy in the slide. 7. A rather similar slightly deeper-coloured rock. Also a por- phyrite ; nothing noteworthy. 8. A darker more mottled felstone. Also a porphyrite, but differing from the others in containing a fair amount of a greenish mineral, This, under the microscope, is seen to occur in irregular patches, sometimes adumbrating the form of a pyroxenic or micaceous mineral. That which dominates in these patches is generally a strongly dichroic, olive-green mineral in small folia, probably a chlorite, associated with viridite and sometimes calcite. Probably . all these are of secondary origin, indicating the former presence of a ferro-magnesian silicate. 9. A rock bearing some resemblance to the last named, but with much pyrite in the hand-specimen. This is less abundant in the slide, which shows the rock to be also a porphyrite, bearing some general resemblance to the last described, except that the green patches are yet more indefinite in outline and more in- determinate in structure. So far as I can ascertain, they are largely composed of granules of an impure epidote and belonites of a greenish mineral, probably hornblende. 10. A moderately fine-grained, pinkish, granitoid rock; the microscope shows it to be composed of quartz, felspar (microcline, orthoclase and oligoclase ?), hornblende, biotite, and apatite, with probably one or two small zircons. There are some slight indications of mechanical disturbance, but none of marked crushing, and the structure of the rock recalls that of the Archean gneisses rather than of the normal granites. So far as I can form an opinion from the slides and specimens alone, I should say that Nos. 1, 3, 5, 10, with possibly 2 and 4, belong to an ancient series of rocks, which, even if wholly or in part of igneous origin, assumed their present mineral structure and condition at an epoch remote from the present. Some of them resemble rocks known to be Archean, and they do not resemble (so far as my ex- perience goes) any which are indubitably Post-Archean: 6, 7, 8, 9 are certainly igneous and of more recent date, though I should doubt if they were not at least of early Tertiary age. . EXPLANATION OF PLATE XV. Fig. 1. Section of flattened garnet, showing mica-schist on right-hand side. x 40. 2. Section of flattened garnet. x 40. Mintern Bros. Chremo lith. PT MYSORE, . my Li | Oo A fx] ya aa al < 4 fy [x4 S ep) a je IH O [xj S Felix Oswald del. oe ‘ : ‘ ' . ‘ YT ' * . J te, , ‘ i Z 7 * ‘ , . é é f oe v és F " 4 i 1 - " ; | ‘ 4 “ ; : " : , rn Fy ; ‘ ‘ . : ¢ { , ‘ i ' ' { a i tes ? 4," } . ‘ Yi we i i U )r as ‘ ‘ , a \ 5 aa hae & : H ie Cea . ' F () = , ’ a ~ i ah | Ro» . ) : . ‘ < ‘ 2 ae pails y . s bs ‘ : . ‘ i - a” ‘ ha » j ‘ + ae ‘ a ‘ F + 3 ” ‘ eat 2 ‘ *s b . ‘i ‘ 7 ( - . a * : rs ‘ ‘ . aT - MYSORE PROVINCE, SOUTHERN INDIA. 653 DIscussIoN. The Prestmpent remarked that on behalf of the Geological Society, as well as of Indian geologists, he would express his pleasure at hearing a paper on India by an independent observer. He referred to Mr. Foote’s view that the auriferous rocks of Mysore differed from the main gneissic group of Southern India. There was no doubt as to the great age of the rocks. The analyses given by Mr. Attwood would be useful. He questioned the Author’s use of the word ‘“ kunker,”’ which meant a small stone and, in the plural, gravel. As lime is commonly made from calcareous nodules in India, the term “‘kunker” has gradually but erroneously come into use amongst Europeans for calcareous rocks. ‘There was great interest with regard to the asserted Tertiary age of the porphyrite-dykes, when viewed in connexion with the great volcanic outbursts of the Deccan ; but he would like to have some much more positive evi- dence as regards the age of these intrusions. With regard to the elevation of the Ghats, he doubted its connexion with pressure- effects. The eastern Ghats are more or less imaginary, and the western Ghats simply a ridge left by denudation. Mr. W. P. Buaxs observed that the schistose rocks closely re- sembled the auriferous Archean rocks of the United States, espe- cially those in Dakota. The Autor, in reply, stated that Prof. Bonney agreed that the porphyritic rocks were much more modern than the Archeean schists through which they broke. He had adopted the word “ kunker” as he found it used in the particular area described and generally applied to the calcareous deposits. Q.J.G.8. No. 176. 2x 654 MR. J. E, MARR AND DR. H. A. NICHOLSON 37. The Srocxpate Suares. By J. E. Marr, M.A., F.G.S., Fellow of St. John’s Coll. Camb., and H. A. Nicwotson, M.D., D.Sc., F.G.S., Regius Professor of Natural History in the University of Aberdeen. (Read May 9, 1888.) [Prats XVI.] I. Introduction. II. Notice of previous writings. III. Description of the typical sections of Skelgill and Stockdale. IV. Description of confirmatory Sections. VY. Comparison with corresponding Beds in other areas. VI. Remarks on the bearings of the results. VII. Description of Fossils. § 1. Lyrropvetion. WE propose, in a series of papers, to supplement the observations which have been previously published upon the divisions, organic ~ remains, and subdivisions of the Lower Paleozoic Rocks of the Lake-district and adjoining areas. In the investigation of the geological structure of any such complicated region as the Lake-. district, the first step necessarily consists In the determination of those rock-divisions which are developed in the area in question to an extent which renders them capable of representation on the one- inch map of the Ordnance Survey. When the first step has been satisfactorily accomplished, the general structure of the region may be said to be determined ; but there may, nevertheless, remain many points of great geological interest and importance which still require solution. Thus, it is now generally recognized that in any region a set of deposits may have been formed so slowly that a thickness of only a few feet of such may mark a lapse of time represented elsewhere by many hundreds of feet of sediment. Im such cases a more minute subdivision of the strata than can be represented upon an ordinary geological map becomes necessary, and it is also essen- tial to enter into a detailed examination and comparison of the organic remains of the different beds. By this method of investi- gation verv important results have already been obtained in other regions, and we see no reason to doubt that the application of the same method to the study of the Palzozoic Rocks of the Lake- district will result in the eventual filling up of many of the gaps which at present exist in the geological history of this area. Under ordinary circumstances it would, no doubt, have been more convenient to commence our investigations with an examina- tion of the oldest rocks of the district, and in selecting the Stock- dale Shales as a starting-point we were influenced by several considerations. In the first place, the Stockdale Shales form a well- marked series, readily separable from the rocks lying below and above them, while they present at the same time considerable varia- tions in the character of their sediments and included fossils. ON THE STOCKDALE SHALES. 655 Secondly, the outcrop along their whole range in the Lake-district proper has been marked in the published maps of the Geological Survey. Thirdly, the equivalent and similar rocks in other areas have been described with a minuteness which is wanting in the case of the other series of the Lower Paleozoic rocks of this region; we are therefore likely, by selecting this series, to test the value of these minute subdivisions for purposes of comparison. The general features of. the district have been so frequently de- scribed, and its structure is so universally known, that it is suffi- cient to remark here that the Stockdale Shales occur on the south side of a great anticlinal, and that they do not appear on the north, as the newer rocks of the northern limb are concealed by the un- conformable overlap of the Upper Paleozoic rocks. In the southern limb the beds first appear on the eastern side of the Lake-district proper, a few miles to the west of Shap Wells, after which they are traceable with a general E.N.E.—W.S.W. strike over the valleys of Long Sleddale, Kentmere, and Troutbeck, and across the head of Windermere to Coniston Waterhead. In this region they dip, usually at a high angle, to the S.8.E., and their course is interrupted by several large north and south faults, the position of which will be seen by reference to the maps of the Geological Survey. (We would here notice that we do not give a map of the outcrop of the beds, as one on a smaller scale than that of the published geological maps would be insufficient for our purpose.) On the western side of Coniston Lake the strike of the beds changes, trending generally in a N.E.-S.W. direction, and continues thus to Broughton Mills, to the south of which we have seen no trace of the Stockdale Shales, on the western side of the Duddon estuary. On the eastern side of that estuary the beds are brought te the surface by a great anti- clinal fold, and appear in the neighbourhood of Dalton-in-Furness, where the exposures are poor. In addition to this the Stockdale Shales are also seen in two areas lying on the eastern margin of the Lake-district,—first in the exposure of Lower Paleozoic which is found between the Pennine fault of the Cross-Fell chain and the New Red Sandstones of the Eden valley, where the beds crop out in the neighbourhood of the village of Knock, in the course of Swindale Beck and its tributary, Rundale Beck. Secondly, in the anticlinal which runs along the Rawthey valley, in the neigh- bourhood of Sedbergh, where the shales are seen in the bed of the river at Rawthey Bridge, and in several of the tributary streams, as Hebblethwaite Gill, Cross Haw Beck, and Taith’s Gill, on the south side of the Rawthey, and in the stream which runs from Spengill Head, on the north side. Representatives of these beds also occur in the neighbourhood of Ingleton in Austwick Beck, and in Teesdale possible equivalents have been described by Messrs, Gunn and Clough. In most places, owing to the small thickness of the series and the high angle of dip, the outcrop is very narrow. This outcrop is nearly at right angles to the direction of the principal streams, so that there are frequent opportunities of seeing the relations of the 2x2 656 MR. J. E. MARR AND DR. H. A. NICHOLSON Stockdale Shales to the beds above and below. Against this ad- vantage must be placed the paucity of sections, but especially the constant occurrence of a strike-fault, which frequently cuts out a great part of the series, and, as we shall eventually show, in every case causes a portion to be missing. Nevertheless the number of exposures is sufficient to allow us to piece together the whole of the succession, save, possibly, at one point only, where we shall give reasons for believing that if any portion of the deposit is now entirely unseen in this district, it is only a very insignificant one. We would record our debt of gratitude to Professor Lapworth for invaluable assistance, and to Professor Hughes for information about the rocks of the Sedbergh district. § II. Noricz or Previous Writrnes. The first attempt at a subdivision of the rocks of the Lake-dis- trict was made by Mr. Jonathan Otley, whose paper appeared ori- ginally in the ‘ Lonsdale Magazine,’ vol. i. p. 433, and subsequently in the ‘ Philosophical Magazine’ for 1820 (Phil. Mag. vol. lvi. - p. 257). Mr. Otley adopted that threefold subdivision of the slates of this area which was afterward supported by Professor Sedgwick, and which forms the basis of all subsequent classifications. The well-known narrow band of Coniston Limestone was shown to form a natural separation between the slates of the second and third divi- sions. This Coniston-Limestone band was proved by Sedgwick to contain a fauna similar to that of his Bala rocks of North Wales, whilst the true slates of the third division undoubtedly contained, in their higher portions, fossils similar to those of the typical Silu- rian rocks of the area explored by Sir Roderick Murchison. At this time the beds which form the subject of this communication were not separated off from that division of the Upper Slates to which Prof. Sedgwick, in 1845, applied the term “Coniston Flags ;” so that all that was written previous to the period when that sepa- ration was effected, concerning the relationship of the Coniston Flags to the Coniston-Limestone series, applies also to the relation- ship between the latter and the Stockdale Shales. In Professor Sedgwick’s writings we find the Coniston Flagstones or Flags at one time connected with the Coniston-Limestone series, at another separated from these and united to the rocks above them; and he finally adopts this arrangement, and, to quote the words used in his ‘Letters’ to Wordsworth, places the Coniston Flags “at the base _ of the Upper Silurian series of the Lake District.” The beds now known as the Stockdale Shales were originally distinguished by Professors Harkness and Nicholson in the year 1868, in a paper “On the Coniston Group ” (Quart. Journ. Geol. Soc. vol, xxiv. p. 296). These authors describe the lower portion of the Stockdale Shales under the name of ‘“‘ Graptolitiferous Mudstones,” and give a list of fossils found in these beds at Skelgill and in Long Sleddale. They refer to the beds now included in the upper part of the Stock- ON THE STOCKDALE SHALES, 657 dale Shales under the term “Grey Grits.” Both these sets of deposits are included as a subdivision of the Coniston Flags, and the Mudstones are considered to rest conformably upon the Coniston Limestone, and are referred by the authors to the Bala. We append a brief abstract of the views expressed in various papers which have appeared subsequently to the one above referred to, and which treat specially of the Stockdale Shales. 1868. “On the Graptolites of the Coniston Flags,” by H. A. Nicholson (Q: J. G. 8. vol. xxiv. p. 521). Alters the term “Graptolitiferous Mudstones” to “ Graptolitic Mudstones,” and describes many Graptolites from these beds. 1868. ‘An Essay on the Geology of Cumberland and Westmore- land,’ by H. A. Nicholson. The Stockdale Shales included as a member of the Coniston Flags. Fossil lists given. Age considered as between that of Bala Lime- stone and that of Lower Llandovery. 1872. “ Migrations of the Graptolites,” by H. A. Nicholson (Q. eGo. vol. xxviii. p. 217). Gives list of species from the ‘‘ Graptolitic Mudstones.” 1872. “Memoirs of the Geological Survey.” Explanation of Quarter Sheet 98, N.E., by Messrs. W. T. Aveline and T. M°K. Hughes. First use the term ‘Stockdale Shales,” and separate them from the Coniston Flags: divide them into a lower portion, ‘‘ Grapto- litic Mudstones,” and an upper, “ Pale Slates.” Give the lithological characters of each, and a list of fossils from the “ Graptolitic Mud- stones” of Holbeck Gill (=Skelgill), near Ambleside. Refer them to Upper Silurian. 1872. “ On the Silurian Rocks of the English Lake District,” by Prof. H. A. Nicholson (Proc. Geol. Assoc. 1872, p. 105). Discusses age of ‘Graptolitic Mudstones”; abandons view that they belong to Coniston Flags, and refers them to Lower Silurian, and considers them conformable with beds above and below. 1872. “On the Continuity and Breaks between the various divi- sions of the Silurian Strata of the Lake District,” by W.T. Aveline (Geol. Mag. vol. ix. p. 441). Considers slight unconformity to exist between Coniston Lime- stone and Stockdale Shales: refers latter to Upper Silurian, and correlates them with Tarannon Shales of North Wales. 1875. ‘*On the central group of the Silurian series of the North of England,” by H. A. Nicholson and C. Lapworth (Rep. Brit. Assoc. we70, p. 78). Use the term “Coniston Mudstone series” for the Stockdale Shales, and suggest the term ‘‘Skelgill Beds” for the “ Graptolitic Mudstones,” and that of ‘‘ Knock Beds” for the Pale Slates, and correlate the entire ‘“‘ Coniston Mudstone Series” with the Lower and Upper Llandovery and Tarannon Shales of North Wales. 1876. ‘“‘ Absence of Llandovery Rocks in the Lake District,” by W. T. Aveline (Geol. Mag. dee. ii. vol. iii. p. 282). Again correlates Stockdale Shales with Tarannon Shales. 658 MR. J. E. MARR AND DR. H. A. NICHOLSON 1876. “Llandovery Rocks in the Lake District,” by H. Hicks (Geol. Mag. dee. ii. vol. iii. pp. 335 and 429). Considers Stockdale Shales of Llandovery age. 1876. “On the Vertical Range of the Graptolitic types in Sweden,” by G. Linnarsson (Geol. Mag. dec. ii. vol. i. p. 241). Correlates Stockdale Shales with Upper Graptolitic Schists of that country. 1876. “Llandovery Rocks in the Lake District,” by C. Lapworth (Geol. Mag. dec. ii. vol. iii. p. 447). Assigns Skelgill beds to Lower Llandovery. 1877. “On the Strata and their Fossil contents between the Borrowdale Series of the North of England and the Coniston Flags,” by Profs. R. Harkness and H. A. Nicholson” (Q. J. G. 8. xxxiii. p- 461). Describe “ Graptolitic Mudstones” or “ Skelgill Beds,” and give lists of Graptolites and of more highly organized fossils from these beds; correlate them with highest beds of Bala series or with lower portion of Llandovery group. Describe ‘‘ Knock Beds,” and incline to regard them as base of (Upper) Silurian. 1878. ‘Discovery of Silurian Beds in Teesdale,” by Messrs. Gunn and Clough (Q. J. G. 8. xxxiv. p. 27). Describe beds at Cronkley Pencil Mill resembling Pale Slates. 1878. “The Moffat Series,” by C. Lapworth (Q. J. G. 8. xxxiy. p-. 240). Correlates Skelgill beds with Birkhill Shales, which he refers to Lower Llandovery. 1878. ‘On some well-defined Life-zonesin the . . . Lake District,” by J. E. Marr (Q. J. G. 8. xxxiv. p. 871). Refers Skelgill beds to May Hill, and supposes unconformity between them and Ashgill Shales. 1879. “On the Geological Distribution of the Rhabdophora,” by C. Lapworth (Ann. & Mag. Nat. Hist. ser. 5, vol. i11.). Assigns a Llandovery May-Hill age to the Skelgill beds ; divides them into a lower (tenuis) and upper (argenteus) zone, and gives lists of fossils from each. Besides the above, many papers have appeared which contain in- cidental references to the Stockdale Shales, or which describe fossils contained therein. These will be alluded to in the body of the paper. § III. Description or tor Typicat Sections oF SKELGILL AND STOCKDALE. The most convenient course for us to adopt in describing the suc- cession of the different subdivisions of the Stockdale Shales is to commence with an account of the typical sections of the two stages of the series, and afterwards to supplement this by an account of the resemblances and variations exhibited in the other sections. The typical section of the beds of the lower stage is that displayed ON THE STOCKDALE SHALES. 659 in the course of the stream near Ambleside, which is termed Holbeck Gill on the maps of the Ordnance Survey, but which has been so often alluded to in geological writings under the name of Skelgill (derived from the farm of High Skelgill, situated near its banks), that it would be highly inconvenient to adopt any other name. It is on account of the strong development of the beds of this stage, in this locality, that one of us, in conjunction with Professor Lapworth, has proposed for the beds the title of “ Skelgill Beds,” a term which we propose to employ here instead of the more ancient term “ Graptolitic Mudstones,” because there are other Graptolitic beds in the district, and the term “ Mudstone” is hardly so appli- cable to the true Shales in which the Graptolites are found, as to the bluish-grey clayey beds, devoid of stratification, which occur between the different bands of Graptolitic Shale, and which do not contain Graptolites. The upper stage of the series is well seen in the course of Stock- dale Beck, which also contains a fair development of the lower stage, so that the name of this beck is particularly applicable to the whole series. In a tributary of Stockdale, which is called Browgill on the maps of the Ordnance Survey, there is an excellent develop- ment of fossiliferous beds of the upper stage, and those beds of this stage which are not seen here are seen in the larger beck close by; so we propose to adopt the section at Browgill, supplemented by that in the adjoining Stockdale stream, as our type section, and, for the sake of uniformity, as well as in order to have the type sections along the main line of outcrop of the Stockdale Shales, to substitute the term “ Browgill Beds” for “‘ Knock Beds” in describing this upper stage of the series. We do this with the consent of Professor Lapworth, who, with one of us, originally proposed the term ‘‘ Knock Beds ” for this series. Our classification, then, is as follows :— : Upper { Browgill stage. Stockdale-Shale series. Tous { Skelgill stage. A. The Skelgill Beds of Skelgill. The stream of Skelgill Beck well deserves to be considered as fur- nishing the type section of the lower stage of the Stockdale Shales, not only on account of the magnificent section exposed along its banks, but also on account of its accessibility, and the unrivalled views of the Lake-district hills as seen from its neighbourhood. The stream rises in the moorland immediately to the east of Wansfell Pike, and enters Windermere a few yards south of the Low Wood Hotel, after a course of about two miles. For the first half-mile it runs in a shallow valley through volcanic rocks and the beds of the Coniston- Limestone series, and then reaches a bridge over which passes a cart-track from Troutbeck village, known as Hundreds Road. This bridge we may speak of as the Upper Bridge. At this point the stream, which has been flowing due south, assumes a south-westerly direction, and enters a ravine which is in a straight line with a 660 MR. J. E. MARR AND DR. H. A. NICHOLSON shallow depression marking the position of the outcrop of the Skelgill Beds, which are concealed for some distance to the north-east of this point. The beds are seen in the stream immediately after turning the corner below the bridge, and a more or less continuous section of the several members of the stage is traceable along the left bank for about half a mile down the stream to a point about 10 chains east of the farm of High Skelgill. The right bank is mainly composed of Ashgill Shales, with a few exceptions to be noted subsequently. At the point near High Skelgill the stream once more turns due south, and soon flows over the beds of the Browgill stage, so that at present our description will be limited to the exposures in that part of the stream which runs between the Upper Bridge and the point at which the stream again turns due south near High Skelgill Farm. Along this portion the direction of the stream is parallel with that of the strike of the beds, which is here nearly due N.E.-S.W., and the beds are dipping at a com- paratively low angle, averaging about 35° to the S.E. Below the Upper Bridge the stream runs for a distance of about 15 chains through a ravine cut in the moorland, and we may speak © of this as the “ moorland” portion of the gill. From this point until a wall is reached, about 5 chains east of the spot near the farm where the stream once more turns due south, it flows through a wooded ravine, and this we shall refer to as the ‘‘ wooded ” portion of the gill. About 5 chains below the point where the stream enters this wood is a foot-bridge, over which a footpath, slanting obliquely up the steep left bank of the stream, is carried; this is the Lower Bridge. Some 15 chains further down the first important tributary from the north enters the main stream, and a few yards further down a second tributary from the north joins the main beck at the point where the latter quits the wood. The remaining few chains over which the stream preserves its 8.W. direction are on swampy ground, with no sections; and at the point where the flow changes to the southward, a third tributary enters the main stream from the north. After these preliminary remarks, we may proceed to describe the section in greater detail. The most continuous vertical exposure which is readily accessible is seen at the Lower Bridge, which one of us, in a paper printed in the Society’s Journal for 1878, has spoken of as the Lower Foot- bridge. The section there inserted is, in the main, correct, but some of the thicknesses have to be modified as a result of numerous subsequent measurements (fig. 1). Aa. Lower Skelgill Beds. (1) A few yards below the Lower Bridge a cliff, some 10 feet in height, is seen, standing immediately above the stream on the left bank. Here the stream is seen to be flowing over the highest beds of the Ashgill Shales, containing the characteristic Brachiopods of the deposit, and having a discontinuous line of calcareous nodules ON THE STOCKDALE SHALES. 661 Immediately above this is a very tough bed, one at the summit. foot thick, consisting of an impure, compact limestone, containing flocculent dark-grey patches, giving it a mottled appearance, and There are no sub- holding a considerable quantity of iron-pyrites. sidiary planes of deposition in this bed, which breaks with extreme Fig. 1.—Section across Skelgill. (Scale 15 feet to 1 inch.) WB Ac 4 hace =} Acl ; Ab 6 = Nets 5 | Ab 2 | Ab 1 => Fault Breccvn Aa2 SS SUT} “Ash gill Shales difficulty, with a somewhat hackly fracture. At this point we have obtained no fossils, but a few yards above the Lower Bridge, at a spot presently to be described, there are a fair number of fossils, which are obtainable with difficulty, the most abundant being a new species of Atrypa, on which account we propose to term this bed the Zone of Atrypa flexuosa. (2) Immediately over this hard limestone band are bluish-black, rather flaggy and somewhat calcareous shales, resting with perfect 662 MR. J. E. MARR AND DR. H. A. NICHOLSON conformity upon the limestone. One foot above the limestone is a permanent divisional plane, which is markedly slickensided, and along which some movement has taken place. A little more than a foot above this is another prominent, slickensided, divisional plane, against which the laminz are seen to die out at the S.W. end of the cliff, whilst at the N.E. end a little fault-breccia occurs, showing that there has certainly been some disturbance here. About one foot above this is a marked, pale-green band, and above this six feet six inches of blackish shales occur, passing to the top of the cliff, where a great mass of fault-breccia marks the position of a considerable strike-fault. The Graptolites preserved in these black shales, which here have a thickness of at least 9 feet 9 inches, are difficult to ex- tract from this cliff; but fortunately at this point the shales are also _ developed on the right bank of the stream, where the black calea- reous Shales are seen dipping immediately at those on the cliff, and an examination of the rocks in the bed of the stream forbids the existence of any fault. The identity of the beds is proved by the fact that the Graptolites, which are beautifully preserved in the shales seen in an excavation in the bank, a few feet above the stream, are identical with those obtainable with some difficulty in the shales of the cliff. These species are :— Monograptus leptotheca, Lapw. Diplograptus sinuatus, Wich. Sandersoni, Lapw. longissimus, Kurck. revolutus, Kurck. vesiculosus, Wich. — tenuis, Pordl. Climacograptus normalis, attenuatus, Hopk. Lapw. Dimorphograptus confertus, minutus, Carr. Nich elongatus, Lapw. Of these forms the most noticeable are the remarkable Dimorpho- graptus confertus, Nich., which occurs in swarms, especially along one bedding-plane, where it is found to the almost complete exclusion of any other species, and Monograptus revolutus, which is also very abundant. One example of Dimorphograptus elongatus occurred. We shall speak of this zone as the Dimorphograptus-confertus Zone ; and this and the underlying zone, we regard as constituting the Lower Skelgull Beds. It will be convenient to consider the development of these beds in other parts of the gill before proceeding to describe the higher sub- divisions. Although the Lower Bridge crosses the gill in the wooded portion, nevertheless the wood mainly occupies the left bank of the stream until we attain a point a few yards below the Lower Bridge, where the right bank also becomes wooded, to the south-west of a wall which runs down this bank to the top of the small cliff overhanging the stream. Here the fault described as occurring at the top of the small cliff in which the beds of the Dimorphograptus-confertus Zone are developed has come down to the stream, and the Ashgill Shales are immediately succeeded by higher beds, which are much crushed ER, ON THE STOCKDALE SHALES. 663 at the base, the Lower Skelgill Beds being entirely faulted out; but some distance below this wall the Dimorphograptus-confertus Beds are again exposed on the right bank of the stream, which here forms a dip-slope from which the shales of this zone may be broken off in slabs of considerable size. Most of the fossils obtained at the Lower Bridge are found here, and where the shales are unweathered the Graptolites have been replaced by white calcite, though in the weathered state they occur as yellow-brown impressions, as is the case for the most part with those found at the Lower Bridge. On the opposite side of the stream at this point the section is very similar to that at the Lower Bridge on the same bank, though there is a smaller thickness of shales of the Dimorphograptus-confer- tus Zone below the fault. The portion seen is disturbed, a slight disturbance having probably crushed out a portion of the Atrypa- jlewuosa Limestone, which is here only three inches thick. Above this we find ten inches of calcareous bluish flags, with the usual Graptolites of the Dimorphograptus-zone, above which is a calcareous pyritous band, apparently in the position of the slickensided divi- sional plane noticed in the section at the Lower Bridge. This band contains badly preserved Graptolites along with numereous Ostracods and small Brachiopods, whose identification it would be too hazardous to attempt. Isolated plates of a species of Y'urrilepas are also tolerably abundant. Lower down the strike-fault is more pronounced, and where there are exposures the Lower Skelgill Beds are again entirely cut out, until we reach the second tributary from the north, on the west bank of which is seen the Atrypa-ficwuosa band halfway up in a cliff, separating the Dimorphograptus-confertus Beds above, with the usual fossils, from the Ashgill Shales below. Returning now to the Lower Bridge, and tracing the Lower Skel- gill Beds up stream, we find the Atrypa-fic~uosa Limestone resting on the Ashgill Shales immediately above the bridge; but the beds above it are here covered with talus. A few yards higher up the stream a dip-fault with a downthrow of a few feet to the north runs ina general K.-W. Jirection, bringing the Ashgill Shales against the Dimorphograptus-confertus Beds on the right bank of the stream, and the strike-fault, which has here reached the bed of the stream, has caused the disappearance of a much greater thickness of beds on its north side, so that at the foot of a high precipice, which will be hereafter noticed as containing a magnificent exposure of some of the Middle Skelgill Beds, not only are the Dimorphograptus-confertus Beds faulted out, but also the lower part of the Middle Skelgill Beds, which latter rest against the Atrypa-flecuosa Bed. This limestone is here seen in the stream, and after being somewhat displaced again by another dip-fault (which runs up a deep gash on the north-east side of the high cliff, in the same way as the first-named dip-fault runs up a similar gash on the south-west side of the clift), it is well seen resting on the uppermost beds of the Ashgill Shales, at a point where the stream turns a corner and runs down a steep dip-slope. Here the highest Ashgill Shales again contain the calcareous nodules 664 MR. J. E. MARR AND DR. H. A. NICHOLSON noticed before, and the Atrypa-—fleauosa band, which is one foot thick, contains a number of fossils, including :— Climacograptus normalis, Zapw. | Strophomena. Atrypa flexuosa, n. sp. Homalonotus ? The breccia of the strike-fault is here seen immediately above the limestone, nor do we meet with any exposure of the Dimorphograp- tus-confertus Beds on the left bank of the stream above this point, the strike-fault usually occurring in the bed of the stream and bring- ing the Middle Skelgill Beds against the Atrypa-flecuosa Zone or even the Ashgill Shales. At one point however, in the moorland portion of the stream, a very good exposure of the Dimorphograptus-confertus Beds occurs on the right bank. This is about a hundred yards below the Upper Bridge. Below the Upper Bridge the stream makes a bend, leaving a promontory mainly composed of the Middle Skelgill Beds in a greatly shattered condition, and at the south-west corner of the - promontory the Dimorphograptus-confertus Beds are seen dipping so as to pass beneath the Middle Skelgill Beds, though a short interval occurs between them, certainly occupied by the usual strike-fault, the breccia of which is seen in places. The Dimorphograptus-beds consist of blue mudstones, here break- ing into rectangular fragments, and resting on the Ashgill Beds, against which they are crushed, as shown by the absence of the Atrypa-flexuosa band, and the disturbed character of the Dimorpho- gruptus-beds, where brought against the Ashgill Shales. The fossils here are somewhat different from those seen at the Lower Bridge. We have found :— Monograptus revolutus, Kwrck. Dimorphograptus confertus, Nich. Sandersoni, Lapw. Swanstoni, Lapw. attenuatus, Hopk. Diplograptus vesiculosus, Nich. — tenuis, Poriti. modestus, Lapw. ? Of these, Diplograptus vesiculosus, Nich., Dimorphograptus Swan- stont, Lapw., and Monograptus tenuis, Portl., are abundant, whilst Dimorphograptus confertus, Nich., is rarer. We consider that thess beds are somewhat higher in the series than those occurring at the Lower Bridge :—first, because the D.-confertus Beds at the Lower Bridge immediately succeed the <2 ' Dee A ‘ x 5 : The Lower Skelgill beds are seen occupying the same position as at the rake, but only one foot of the shales which we refer to the Dimorphograptus-zone is found below the strike-fault. Another ON THE STOCKDALE SHALES, 681 fault, which dies out before we reach the rake, brings the Browgill Beds against the Middle Skelgill Beds, and between the two faults these latter occur in an overfolded synclinal, as shown in the figure. The lowest beds seen belong to Ab 4, the glaber-zone, of which a few inches are seen in contact with the Lower Skelgill Beds, whilst two feet are visible resting against the second fault. These beds are blue mudstones, of the same character as those we have had frequent occasion to describe, but we have found no fossils therein at this spot. ‘heir identification is rendered certain by their position, for they pass into the newer beds of the synclinal. It is evident that the strike-fault between the Lower and Middle Skelgill Beds is more important here than at Skelgill, and the result is that the zones of Enerinurus punctatus and Monograptus ar- genteus are unrepresented in this section. Ab 5. Continuing the description of the beds in the isocline, we observe the glaber-mudstones passing up into 1 foot 6 inches of black shales, in which the Graptolites are well preserved in relief. Succeeding these are some pale-greenish mudstones apparently devoid of fossils, and above them we meet with about four feet of blackish shales, with olive-brown staining along the joint-surfaces, and containing Monograptus convolutus with its usual associates. The list of fossils found in these shales in Browgill will be enu- merated after describing the shales of this zone seen at the rake; but in the meantime we would mention that we found one specimen of Petalograptus cometa a few inches below the pale-green mudstones in the inverted limb of the syncline, and therefore in newer beds. The band of black shales between the pale-green mudstones and the glaber-zone is, as at Skelgill, marked by the occurrence of great quantities of Diplograptus tamariscus, Nich. We have called particular attention to this isoclinal fold, because such are most exceptional in the Stockdale Shales between Browgill and Coniston Waterhead, and it is the rule along that country to find members of the series faulted out, and not reduplicated. To return to the section at the rake :— A thickness of one foot four inches of the convolutus-shales is seen immediately above the strike-fault, these forming the extreme summit of the zone, and passing up into the mudstones of the succeeding zone. These shales are quite like those of the con- volutus-zone in Skelgill, viz. greyish-blue shales, with olive-brown stains along the joint-surfaces. We have obtained from the M.-convolutus zone of Browgill :— Monograptus convolutus, His, Rastrites hybridus, Lapw. eregarius, Lapw. Retiolites perlatus, Nich. — Nicoli, Harkn. Diplograptus Hughesii, Nich. —— proteus, Barr. tamariscus, Nich. attenuatus, Hoph. Petalograptus cometa, Gein. Ab 5, The beds into which the shales of the preceding zone pass up consist here of pale-green mudstones, having a very ferruginous, calcareous, nodular band near the summit ; the whole has a thickness 682 MR. J. E. MARR AND DR. H. A. NICHOLSON of only two feet, and we have obtained no fossils from it, but it is shown by its position to be the representative of the “‘ Barren Band ” of Skelgill. Ac 1. The preceding beds pass into three feet of Graptolitic shales of a leaden colour, except near the centre, where they are blacker. This is the Clingani-band, and, like the corresponding band at Skelgill, it contains a great abundance of Climacograptus normalis along certain lines, along with :— Monograptus Clingani, Carr. Monograptus crenularis, Lapw. Nicoli, Harkn, M. Clingani is the prevailing form. é Ac 2. The overlying mudstones, which present the usual passage into the shales above and below, are only one foot five inches in thickness. They consist of pale-green, calcareous shale, with numerous dendritic markings, and containing few fossils except along one bedding-plane, where they are very numerous, indeed far more so than in any one of the non-Graptolitic bands of the Stockdale Shales of any other locality whatsoever. ‘Two nodular, calcareous bands are seen near the centre of the zone, with the usual chocolate- coloured earthy residue left where the nodules are weathered out, and between these bands occurs the bedding-plane alluded to above. Besides this, a few fossils are found in the lower calcareous band. Fossils :— Ampyx aloniensis, n. sp. Phacops elegans, var. glaber. Harpes judex, n. sp. elegans, Beck & Sars. Calymene Blumenbachii, Brongn. Acidaspis. Proétus brachypygus ? Leptzna quinquecostata, M‘Coy. Encrinurus punctatus, Wahl. of. sericea, Sow. Phacops mucronatus, brongn. Also occasional plates of a Cystidean. Very many heads of the Ampyx are seen, and all the fossils cf the A.-aloniensis zone of Skelgill appear to occur here, with a few others, so that there would be no difficulty in fixing the horizon of the zone, even if it were not seen in the same position as at Skelgill, viz. between the Clingani-band and the spinigerus-zone. Ac 3. The spinegerus-zone of Browgill is about two feet thick ; but the passage into the mudstones above is so gradual that it is difficult to fix upon the exact line of demarcation. The lower part of the zone consists of black shales, weathering olive-brown, and with many Graptolites along certain bands, whilst the upper part is composed of shales of many colours, some showing the lozenge- pattern also found in the beds of this zone at Skelgill and, indeed, in all places where it is well developed throughout the district, so that we need not call attention to this feature in our future de- scriptions of the sections. Monograptus spinigerus occurs as usual in countless multitudes, with its customary associates, which we did not trouble to collect ; but one specimen of Rastrites hybridus was obtained, and we call attention te it, as it has not turned up in the spznigerus-zone elsewhere. iy ‘ ————— ee ON THE STOCKDALE SHALES, 683 Ac 4. The highest beds consist of the blue mudstones, which occur between the spinigerus-zone and the Browgill Beds ; these are here ten feet in thickness, and contain a calcareous nodular band of the usual description, ten inches thick, and at a distance of three feet from the base. No fossils have been found here in these mud- stones of the erinaceus-zone, and their passage up into the Browgill Beds has been already described. The section in Stockdale Beck below the cascade over the Coniston Limestone is, so far as the Skelgill Beds are concerned, quite like that occurring at the rake in Browgill; for we get the convolutus- beds as the lowest zone developed, and above it the remaining zones of the Middle Skelgill, and all the zones of the Upper Skelgill Beds occur just as there, so that further description is unnecessary. The strike-fault below the shales of the convolutus-zone is marked by a depression down which a rivulet trickles from a swamp in the field above, and this fault appears to bring the convolutus-beds actually against the Coniston Limestone, though there is a short interspace, marked by the above hollow, in which no rock is seen. Stile End. The Stockdale Shales are apparently shifted to a slight extent by a dip-fault, or probably a complex of such faults, running down the Long Sleddale valley ; but as the lower parts of the valley are here occupied by alluvium and drift, no section of the beds is seen until after mounting the hill on the west side of the valley for a con- siderable distance. About halfway up the Stile End Pass, shales Fig. 4.—Section near Stile End. (Scale 12 feet to 1 inch.) phalus- limestone (Ash- gill Shales). Stauroce, ---- Pale band. ; ' 1 ' belonging to the Dimorphograptus-zone are seen cropping up on the moorland ; but the exposure is a small one and of little interest. Still higher up, and a very short distance below the summit of the pass, on the Long Sleddale side, a section of the Skelgill Beds is found on the right bank of a small stream to the south of the path (see fig. +). | The base of the Ashgill-Shales series occupies the left bank of the 684 MR. J. E. MARR AND DR. H. A. NICHOLSON stream, down which the usual strike-fault runs, and the lowest beds seen on the right bank are mudstones, of which a thickness of 1 foot 6 inches occurs. Above this are 5 feet 8 inches of Graptolitic shales, having the ordinary lithological characters of the convolutus-zone, and containing its fossils. A pale-green band, two inches thick, occurs a foot above the base of these shales, and at first sight it appeared as though the shales, with many specimens of D. tamariscus, would occur beneath this; but this was found not to be the case, and we believe that the mudstones at the bottom of the section belong to the convolutus-zone, and that the shales with many specimens of D. tamariscus should occur beneath this, and are not here exposed. Fossils :— Monograptus convolutus, Hs. Rastrites hybridus, Zapw. leptotheca, Lapw. Diplograptus tamariscus, Nich. gregarius, Lapw. Climacograptus normalis, Lapw. Nicol, Harkn. Aptychopsis, Rastrites urceolus, Richter. Ab 6. The Barren Band here consists of two feet ten inches of blue mudstones, passing down into the beds below. (It will be ~ convenient if we remark that a passage is understood unless otherwise intimated.) It yielded Leptena quinquecostata, M‘Coy, and Whit- fieldia tumida, Dalm. ? Ac 1. The Clingani-band is represented by one foot of grey-blue Graptolitic shale, with the usual fossils accompanying the cha- racteristic small M. Clingani, and above it is Ac 2, the Ampya- aloniensis zone, of which only two feet are seen, and which yielded no fossils. The Browgill Beds occur in isolated outcrops on the moorland, at several places between Long Sleddale and Kentmere, but they present little of interest. Kentmere Sections. No section of any importance occurs on the east side of the Kent- mere valley, the hill-sides being largely occupied with turbary. A number of dip-faults run down the valley, shifting the beds to some extent, and the first good section of the Stockdale Shales is seen in the bed of the Kent, just east of the church. Only the upper portion of the Browgill Beds occurs here, with the usual fine, hard, greenish-grey grit interstratified with shales ; but the passage into the Coniston Flags is admirably displayed, the Browgill Beds having interstratified bands of blue mudstones towards the summit, until at last these preponderate, and the pale bands become rarer, and finally disappear altogether, the complete passage taking place in the course of twenty or thirty feet. On the west side of the valley the dip-faults become very numerous, and the beds are greatly shifted laterally, as shown by the outcrop of the Coniston Limestone; but we meet with no exposures of the Stockdale Shales until arriving at a point some distance above the bottom of the Kentmere valley. Here two small ‘ ON THE STOCKDALE SHALES. 685 streamlets unite at the 900-feet contour-line to form a tributary of Hallgill, and the southernmost of these displays the Stockdale Shales dipping to the 8.8.E., and striking transversely across the beck. The lowest bed seen belongs to the zone of Ampyw aloniensis, and one of the calcareous nodular bands is seen in it, and above it is the base of the spznigerus-zone, composed of black earthy shales crowded with Monograptus discretus, Nich., and containing also M. jaculum, Lapw., and other fossils. Above this is a short interval, and then the upper part of the spinigerus-zone comes on, exhibiting the usual variegated shales, with :— Monograptus spinigerus, Nich. Diplograptus modestus, Lapw.? jaculum, Lapw. Petalograptus palmeus, Barr. — distans, Pordl. Climacograptus normalis, Lapw. crassus, Lapw. Retiolites perlatus, Nich, Rastrites urceolus, Richter. Peltocaris. Diplograptus tamariscus, Nich. These shales are succeeded by 10 feet of blue mudstone, belonging to the A.-erznuwceus zone, in which no fossils have been found here. These pass into the Browgill Beds, some feet of which are seen in the stream, after which is a gap in the place where the turricula- tus-bearing black band should occur. No signs of it are visible. Above this are more pale-green shales, with a few black bands con- taining badly preserved Graptolites. Some of the bands are pro- bably covered up, for in the stream immediately below this are loose fragments containing the Graptolites characteristic of the M.-crispus zone, including :— Monograptus crispus, Lapw. Monograptus jaculum, Lapw. - exiguus, Nich. Petalograptus palmeus, Barr. discus, Torng. Retiolites Geinitzianus, Barr. pandus, Lapw. . Troutbeck Valley. A marked depression indicates the position of the Skelgill Beds above the section just described, and an isolated exposure on the moorland just south of the summit of the Garbourn Pass furnishes the following fossils of the fimbriatus-zone :— Monograptus fimbriatus, Nich. Climacograptus normalis, Lapw. Diplograptus tamariscus, Nich. Orthoceras araneosum, Sarr. — sinuatus, Nich. Proceeding to the Troutbeck side of the pass, the depression marked by the mudstones or, rather, more probably by a fault which cuts them out entirely, is seen running diagonally down the hillside towards Troutbeck church, shifted laterally by some small dip-faults, and crossing the Garbourn road just below the large flag-quarries. On the hillside above this depression are several exposures of and quarries in the Browgill Beds, but no continuous section. On reaching the bottom of the valley the beds are shifted oyy;G.8. No. 176. 27 686 MR. J. E. MARR AND DR. H. A. NICHOLSON half a mile to the north by the great dip-fault, and the next section in the Stockdale Shales is met with in Scot Beck. A dip-fault runs down this stream, bringing the Stockdale Shales of the left bank against the Ashgill Shales on the right. The hard mottled pyritous limestone of the Atrypa-flewuosa zone is seen on the left of the stream, containing no fossils here. Above it are two or three inches of hard, bluish-black, unfossiliferous shales, apparently belonging to the Dimorphograptus-zone, and above these is a smashed mass of shales with a few badly preserved Graptolites, including Monograptus fimbriatus, Nich., M. concinnus, Lapw., and Petalograptus ovato- elongatus, Kurck, belonging to the jfimbriatus-zone. The usual strike-fault evidently occurs at the base of these, and accounts for their crushed condition. Lower down the stream the Browgill Beds are seen, with many black bands, which are greatly hardened, and no fossils were seen in them. Immediately to the west of this a drain was cut in 1886 in the field, and exposed the spinzgerus-beds with beautifully preserved specimens of Monograptus spinigerus ; and at the summit of these were a few inches of the mudstones of the erinaceus-zone. After crossing a mass of Coniston Limestone brought against the Stockdale Shales by trough-faults, the depression marking the position of the (probably) faulted-out Skelgill Beds may be traced westward across Nanny Lane, after which it bends to the south-west, and so is continued into Skelgill at the Upper Bridge, as previously described. On the moorland to the south of this depression are many small quarries in the Browgill Beds, which contain numerous minute and indeterminable Brachiopods. These beds are traceable on the high ground to the south-east of the beck to near High Skelgill Farm. It will be remembered that the Skelgill Beds were last seen where the stream left the wood and ran for a few yards over a swampy tract. It here turns due south, and is presently crossed by the bridge leading to High Skelgill Farm. The Browgill Beds first appear in the stream just above this bridge, and consist of pale green shales, interstratified with which are a number of indurated grey bands, the lamination-planes of which are marked with minute wrinklings, which render the contained Graptolites undeterminable. They are almost certainly the crispus-beds, the turriculatus-beds being concealed under the alluvial material higher up the stream. About 30 yards below the bridge the calcareous nodular bands forming the base of the Upper Browgill Beds are found, and are succeeded by the usual pale shales with interstratified grit bands, with which no Graptolite-shales were seen; and these pass up, in the way described when dealing with the Kentmere section, into the Lower Coniston Flags, which contain well-preserved fragments of vomerine Graptolites. Beyond this the beds strike through Dove- nest Wood to the eastern shore of Windermere. ~~ ON THE STOCKDALE SHALES. 687 Pull Beck. The extensive bay of Pull Wyke, on the west side of Windermere and close to the head of the lake, is due to the soft rock of the Stockdale Shales, which are masked to the westward by the exist- ence of an alluvial flat, through which the stream called Pull Beck runs. Crossing over this stream by the bridge over which the Coniston road runs, we may follow the latter road past the great Brathay Flag-quarries to a cart-track which turns to the right through a gate immediately beyond the quarries. If we follow this cart-track we are presently brought down to the stream near some cottages. The Skelgill Beds are exposed in numerous more or less isolated outcrops in the bed and banks of the stream and in the lane north of the cottages; but they are so cut up by numerous minor dip-faults as to assume the character of a fault-breccia on a large scale, and any attempt to make out a succession is futile. The Atrypa-flewuosa limestone is seen in the lane north of the cottages, and has the same character as at Skelgill; but no fossils were found here. The Dimorphograptus-confertus Beds occur in the stream by the bridge at the cottages, and contain numerous well-preserved specimens of Monograptus revolutus, Murch. The Middle Skelgill Beds are seen in many places, and the fossils of most of the zones can be collected in an admirable state of preservation, as the beds in this faulted tract have escaped to a great extent the effects of cleavage. In the wood west of the cottages a small exposure of the alonzensis-zone occurred and yielded an excellent specimen of Proétus brachypygus, n. sp. Beyond the wood the stream runs through a few fields to a small spinney called Redding Coppice, and there receives a tributary from the west, whilst the main stream flows from the south-west. In the main stream, just above the point of junction with the tributary, the black bands of the crispus- zone occur, and the fossils at this point are in a better state of preservation than in any other exposure of this zone which we have met with. They include :— Monograptus crispus, Lapw. Retiolites Geinitzianus, Barr. exiguus, Lapw. perlatus, Nich., var. pandus, Lapw. Petalograptus palmeus, Barr, discus, Torng. , var. tenuis. Hisingeri, Carr. Peltocaris. Cyrtograptus? spiralis, Gez. Higher Browgill Beds occur further up the stream. Just west of this point a great dip-fault shifts the beds five sixths of a mile to the south, and the pale shales of the Browgill Beds are seen in a beck coming down the hill from the west, just south of Sunny Brow. Here they are of no great interest, and although several exposures of Browgill Beds and occasional patches of the Skelgill Beds are seen between here and the Coniston Valley, no section of particular interest is found till Coniston Waterhead is reached. ‘There are some exposures of Skelgill Beds in a stream near the Waterhead Hotel ; but the best sections occur further west. 222 688 MR. J. E. MARR AND DR. H. A. NICHOLSON Yewdale Beck. Just east of the Waterhead Hotel another great north-and-south fault, ranging down Coniston Lake, shifts the beds to the north a distance of nearly a mile, and accordingly we again meet with the Stockdale Shales in Yewdale Beck, which flows through the Yew- dale Valley west of Tarn Hows Wood, in a south-westerly direction, and consequently parallel with the strike of the beds, which between Sunny Brow and Broughton Mills is north-east and south-west instead of east-north-east to west-south-west. At this point are some saw-mills, which are about half a mile north of Coniston church ; and above the weir belonging to these mills the Dimorphograptus- confertus beds are seen striking slightly obliquely across the stream, and are again met with some yards higher up after crossing a meadow. ‘There is an apparent thickness here of at least 50 feet; but an examination of the beds suggests much repetition. They occur in a Series of lenticular masses, so as to produce a simulation of false-bedding, and the beds are extremely indurated, the lamina- tion-planes being marked with minute wrinklings, which render the fossils, abundant enough, generally undeterminable. We recognized Monograptus revolutus, Kurck, and WM. tenuis, Portl. A strike-fault ranges along the south-east bank of the stream and brings the Middle Skelgill Beds against the Dimorphograptus-beds, cutting out the lower portion of the middle group, so that the zones of Mono- graptus fimbriatus, Encrinurus punctatus, Monograptus argenteus, and part of the zone of Phacops glaber are absent. The upper part of the Phacops-glaber zone is seen passing into the convolutus-beds, of the usual appearance, and containing the usual fossils; but the summit of this bed is not seen at any accessible point, and, indeed, the next beds we were able to examine were those belonging to the zone of Acidaspis erinaceus, which were seen passing up into the Browgill Beds. Following the beck to the cluster of houses known as the Far End another exposure is reached where the beck turns sharply to the south-south-east, and the Stockdale Shales leave the beck and Fig. 5.—Section at Far End, Yewdale Beck. (Scale 12 feet to 1 inch.) LB Ac2 Ac3 strike across the drift-covered country in the direction of the rail- way-station. At this turn of the stream the above section is met with (fig. 5). The Ampyx-zone (4 feet seen) is succeeded by the ON THE STOCKDALE SHALES. 689 spinigerus-zone (2 feet thick, but somewhat crushed), which yielded, to a brief search, * Monograptus spinigerus, Nich. Diplograptus Hughesii, Nich. distans, Pordl. Two calcareous nodular bands of the ordinary kind occurred near the top of the einaceus-zone, which shows the usual passage into the Browgill Beds, and is here 10 feet thick. Mealy Gill. Half a mile after leaving Yewdale Beck the Stockdale Shales are again met with in Church Beck, where this stream is joined by a tributary coming from the south-west known as Mealy Gill, and a good section of the shales is exhibited in a wooded gully through which the latter runs, and is found just above the bridge over which a siding from the railway-station is carried. Fig. 6.—Section in Mealy Gill. (Scale 12 feet to 1 inch.) Ac4 Fault Breccia. Pee ert rer See ee ee ee rrr Mar mareee The lowest beds seen are on the north-west bank of the stream, as seen in fig. 6, which shows a restored section taken from diffe- rent parts of the gill, so as to exhibit all the zones which we have detected here in the Skelgill Beds. The Lower Skelgill Beds occupy a great part of this bank, but in one place a fragment of the fimbri- atus-zone occurs in which the fossils are beautifully preserved. They include :-— Monograptus fimbriatus, Nich. Petalograptus ovato-elongatus, leptotheca, Lapw. Kurck. Rastrites peregrinus, Barr. Climacograptus normalis, Lapw, Diplograptus sinuatus, Nich. 690 MR. J. E. MARR AND DR. H. A. NICHOLSON In most cases, however, the usual strike-fault runs up the bed of the stream, and the Middle Skelgill Beds are developed only on the right bank. About halfway between the railway-bridge and a waterfall which flows over the smashed Lower Skelgill Beds is a precipitous cliff-section on the right bank, and at the base of this a few feet of much-broken shale of the fimbriatus-zone occur above the fault, having a gentler dip than the Lower Skelgill Beds of the opposite side of the stream. Ab 2. Above these jimbriatus-shales about 4 feet of mudstone of the Encrinurus-punctatus zone can be measured; but the junction with the fimbriatus-shales is not seen. Ab 3. The most interesting feature of this gill is the occurrence therein of the argenteus-zone, as this is the only section other than the typical one in which we have found it. It is a little thinner than at Skelgill, being only 6 inches thick, and is more strongly cleaved than at that place; but in the centre runs the remarkable pale green streak, one quarter of an inch thick, which is also found at Skelgill at a distance of 7 miles in a direct line. Owing to the cleaved nature of the rock fossils are difficult to - procure; but we found Monograptus argenteus, Nich. Diplograptus sinuatus, Nich. leptotheca, Lapw. Petalograptus ovatus, Barr. — cyphus, Lapw. The first-named occurs in considerable quantity. Ab4. Six feet of the zone of Phacops glaber is seen above the argenteus-zone. It has the usual calcareous nodular bands, as has the punctatus-zone in this section. A fault is seen above this with what are apparently some of the convolutus-shales crushed in the fissure in one place ; but the next zone which is well developed is Ac 2, the zone of Ampyz aloniensis, so that the convolutus-zone, the Barren Band, and the Clingani-band are here cut out. At the waterfall the section is similar, the very top of the Eneri- nurus-punctatus zone only is found above the fault, and this is sue- ceeded by the argenteus-zone, which is close to the stream at the head of the fall, and is succeeded by some Phacops-glaber mudstones, after which the second fault brings the zone of Ampyzx aloniensis against these. Ac 3. The spinigerus-shales of normal character, but somewhat crushed, 2 feet thick, but possibly some crushed out altogether. They contain abundance of Monograptus spinigerus, Nich., along with WM, lobiferus, M‘Coy, M. distans, Portl., Diplograptus tamaris- cus, Nich., &c. Ac4. The zone of, Acidaspis erinaceus is from 8 to 10 feet thick so far as can be seen, and the mudstones pass up into the Browgill Shales. The beds of the last two zones are seen on the moorland on the right bank and a turn in the stream causes the beds of the ertnaceus- zone to strike into the stream, where the Browgill Beds overlie them. Twenty-one feet of pale green shales are succeeded by a black band ON THE STOCKDALE SHALES, 1 inch thick, which is greatly hardened, and is probably the band containing Mono- graptus turriculatus, Barr.; but we could obtain no fossils therefrom. About 8 feet of pale green shales overlie this, and then several black bands like those of the crzspus- zone are interstratified with the pale shales ; but they too have had their fossils oblite- rated. A little to the south-west of the section just described the beds are shifted some- what to the north by a dip-fault, and the line of outcrop of the Skelgill Beds may be followed by a line of depression, along which runs Braidy Beck, a tributary of Mealy Gill, to a pool of water known as Boo Tarn, and then onward alongside the Walney Scar road, and over a peat-moss to Torver Beck, which is a mile and a quarter to the south-west of the section last described. Along the whole of this distance frequent exposures of the Browgill Beds are seen on the moorland; but there is no feature of any interest to record. Torver Beck. This stream runs from Goat’s Water at right angles to the strike of the beds. West of the large flag-quarry of Tranearth the depression above mentioned crosses the beck, and there is certainly a strike-fault across the stream here, as there is little space in which no rock is exposed, and a considerable amount of the Coniston-Lime- stone series and nearly all the beds of the Skelgill group are unseen. To the east of the fault the section shown in fig. 7 is seen. Ac 3. The spinigerus-zone is the lowest band visible. The beds are much broken against a minor fault which crosses the stream transversely, and a dip-fault also runs on the north-east side of the beck, displacing the beds of the erinaceus-zone. Above the small transverse fault are two or three feet of the spnigerus-shales, which are here blacker than is usually the case, and contain fossils preserved in relief, w& ao _ 6 90 “SOUL IT | | el | 4 | \ 5 E ‘10 peqzraro @ 2H JO 691 “qe JF 06 TLOQY (YOU T 04 409} QF OTBOG) “yoo wansoy, Ue WoNDIG’—'}, “SLT 692 MR. J. E. MARR AND DR. H. A. NICHOLSON a mode of occurrence somewhat unusual among the shales of this zone. The fossils are :— Monograptus spinigerus, Nich. Monograptus lobiferus, M‘Coy. crassus, Lapw. Diplograptus tamariscus, Nich. jaculum, Lapw. Petalograptus palmeus, Barr. Ac 4. These shales pass up into the mudstones of the Aciduspis- erinaceus zone. ‘These are seen on the right bank of the beck, just above a wall, and bend round so as to occur with a slightly diffe- rent strike on the left bank. They are 10 feet thick, and contain two bands of calcareous nodules near the centre, separated by about a foot of mudstone. Fossils are common between these net bands, and we have obtained here Lindstreemia, sp. Phacops eleniaeh Boeck & Sars. Acidaspis erinaceus, n. sp. Leptzna quinquecostata, M‘Coy. All these forms are found abundantly, the Acidaspis usually in fragments, and perfect specimens are rare. These erinaceus-beds — are shifted to the north-west for a distance of about ten paces by the dip-fault, and there come down to the stream, as the fault has now entered the bed of the stream. The beds of the last zone pass up into the pale shales of the Browgill group, and there is a tolerably complete section of this group to the base of the Coniston Flags; but as the beds are much disturbed exact measurement is impossible. We find the following development of these beds :— Ba 1. Fifteen or twenty feet of ordinary pale shale, surmounted by a thin seam of hard grey shale one inch thick, in which we ob- tained Monograptus turriculatus, Barr., in a bad state of preserva- tion; but this is sufficient to show that these beds belong to the turriculatus-zone. Ba 2. About 10 feet of pale shale, surmounted by 20 feet of black shales interstratified with pale bands, as is usual in the crispus-zone, and specimens of Monograptus crispus occurred here. About 20 feet of pale shale come on above this. These are the beds of the crispus-zone. Bo1. A pale band with calcareous nodules 2 or 3 feet thick, forming as usual the base of the Upper Browgill Beds. Bb 2. These uppermost beds of the Browgill group are less stained than usual, being mostly green, and contain the hard fine-grained grit-beds. Over 100 feet of these beds seem to be developed, so that the Browgill Beds in this section are about 200 feet in thick- ness. ‘They pass up in the ordinary way into the Brathay Flags, below a waterfall. This and the section at Stockdale are the only two sections along the main line of outcrop which afford a fairly complete exhibition of the whole of the Browgill Beds. ON THE STOCKDALE SHALES, 693 Ashgill. The usual depression is continued from Torver Beck to Ashgill Quarry, about two thirds of a mile to the south-west. The section in the quarry is shown in fig. 8. Fig. 8.—Section across Ashgill Quarry. in, i. (Scale about 50 feet to 1 in.) hd . ‘ Ld é Z S. 2 E g 53 E Z Ae 3 m2 Coal D SQ . = "Ep we £3 e "ee as a 3h BE © 3 3 < < % A < < f \ The Dimorphograptus-beds are seen in the face of the quarry resting on the Ashgill Beds, the Atrypa-flexcuosa limestone being” here crushed out. They are hard, ferruginous, well-laminated, grey-black shales, of glossy appearance, and with Graptolites, inclu- ding Monograptus revolutus, Kurck, in a very indifferent state of preservation. Dimorphograptus confertus seems to occur here, but the shales are strongly cleaved, and sufficiently large pieces cannot be obtained to show the whole of any individual Graptolite. No higher beds of the Skelgill series occur. In the south-west corner of the quarry a fault, which runs slightly obliquely to the strike, brings the Dimorphograptus-beds once more against the lowest part of the Ashgill Shales—the Stawrocephalus- limestone. ‘They are here seen to be affected by a series of folds, which causes reduplication of the shale. This is the clearest sec- tion we have seen exhibiting this feature; but we feel convinced that these shales are repeated often many times upon themselves all the way from Yewdale Beck to Appletreeworth Beck. Below the quarry no rock is seen for a considerable distance ; but at the tail of what was once an island (though the south-western branch of the stream is now dry), about halfway between the quarry and Ashgill Bridge, the black shales of the crispus-zone crop out in the stream, associated with the usual pale shales. The fossils here are in a very tolerable state of preservation and include :— Monograptus crispus, Lapw. Monograptus griestonensis, Nicol. exiguus, Nich. — Hisingeri, Carr. pandus, Lapw. Retiolites Geinitzianus, Barr, —— discus, Torng. Petalograptus palmeus, Barr, The Retiolites occurred only in the highest band visible. The whole thickness is about 20 feet. Just above Ashgill Bridge the 694 MR. J. E. MARR AND DR. H. A. NICHOLSON calcareous nodular band forming the base of the Upper Browgill Beds is seen, the intervening ground being covered with drift. A few feet above the calcareous band and on the other side of the bridge are some light shaly beds, stained pink, with a thin pebbly seam a quarter of an inch thick, about 7 inches from the summit. The pebbles are only about the size of a pea and are well rounded ; and we mention this band as it is the only one which we have found in the whole Stockdale-Shale series which has any coarse material in it. Above this is a considerable thickness of pale shale with hard grits belonging to the Upper Browgill Beds ; but ‘the junction with the Lower Coniston Flags is not seen. The depression caused by the Skelgill Beds or by the strike-fault runs in a south-westerly direction from this over a low col to the head of Appletreeworth Beck, which is reached in about one sixth of a mile from Ashgill. Appletreeworth Beck. Sections in the Stockdale Shales are exhibited at intervals for — over a mile between the head of the beck and Appletreeworth Farm. The stream runs in a south-westerly direction and along *the strike of the beds, and we find the Lower Skelgill Beds as usual continuous with the Ashgill Shales and occurring generally on the north-west (right) bank of the stream, whilst the middle and upper beds and the Browgill group are developed on the left bank. No section of any importance need detain us until we reach a precipi- tous cliff a few hundred yards above the farm on the left bank of the stream. The section across the stream at this point is shown in fig. 9. The dip-slope is composed of the usual Ashgill Shales, at the summit of which is a band of large calcareous nodules, as at Skelgill. Immediately above this is a very thin, dark grey, calca- reous band crowded with Ostracods and inseparable both from the Ashgill Shales below and the Atrypa-flexuosa beds above. We do not know whether to refer this Ostracod-bearing band to the lower or upper group ; but it is a matter of no importance, as there is not the slightest doubt that a passage exists here. The Atrypa-fleauosa band is only 3 inches thick and consists of the usual light grey, mottled, pyritous limestone. The usual strike-fault runs down the stream ; but at the upper end of the cliff it occurs some way off the stream on the left bank, and allows of the occurrence of about 15 feet of Dimorphograptus-shales with Monograptus revolutus, &c., in a small cliff. These beds are probably folded on themselves, as they exhibit a simulated false-bedded structure. At the point where our section is taken, lower down the stream, the fault has come to the bed of the stream, and below the line of section the thickness of beds rendered invisible by the fault increases, and higher and higher beds are brought against the Lower Skelgill Beds, until at last all the zones of the Middle and Upper Skelgill Beds are faulted out and the Browgill Beds rest against the Lower Skelgill Beds. . ON THE STOCKDALE SHALES. 695 A little above the Atrypa-flexuosa band a thin bed occurs in the Dimorphograptus-shales, with small Brachiopods and Z'urrilepas, as at Skelgill. Ab1. The shales of the fimbriatus-zone are seen on the line of our section at the base of the left bank of the stream ; they contain Fig. 9.—Section across “ Cliff” Appletreeworth Beck. (Seale 12 feet to 1 inch.) i eesseeas, Malt: Ashgill Shales. Monograptus fimbriatus, Nich., Petalograptus ovato-elongatus, Kurck, Rastrites peregrinus, &e. A subsidiary disturbance is seen above them, removing the Encrinurus-punctatus zone, the argenteus-zone, and part of the zone of Phacops glaber; but about 10 feet of the latter remains with its nodular bands. Ab5. The convolutus-beds are seen, but the exposure is not a very good one. We obtained Monograptus convolutus, His., Rastrites hybridus, Lapw., Diplograptus tamariscus, Nich., &c. A gap occurs here with no rock visible. Acl. The next rock above this gap belongs to the Clinganz-band, a few inches of shale occurring with Monograptus Clingani, Carr., &e. Ac2. The aloniensis-zone consists of blue mudstones about 2 feet 6 inches thick. Ac 3. The spinigerus-zone consists of many-coloured shales 2 feet 6 inches thick, with abundance of Monograptus spinigerus, Nich., 696 MR. J. E. MARR AND DR. H, A. NICHOLSON Monograptus distans, Portl., and the accompanying fossils, and is succeeded by Ac4. The Acidaspis-erinaceus mudstones, 10 feet thick, and passing up into the Browgill Beds above. The latter are difficult of access, and we were unable to work them in detail. We have not collected carefully from the beds of this section, as they are much cleaved, and the fossils are very indifferent; we merely obtained sufficient to satisfy ourselves of the identity of the beds, and did not work the Trilobite-bearing mudstones at all for fossils ; indeed, with the exception of one or two cases, we have left these latter untouched, knowing the time required, as a general rule, to extract any fossil remains from these comparatively barren bands, and knowing also that the identification of the Graptolitic zones above and below each mudstone band is sufficient to fix the position of the mudstone. It has been stated that the strike-fault increases in intensity towards the south-west; and just below Appletreeworth Farm the disturbance has been so great as to produce the remarkable section seen in fig. 10. Fig. 10.—Section of Farm, Appletreeworth Beck. (Scale about 200 feet to 1 inch.) N.E cs) =| io) <2 re eye = 2) oa as = Poe a: Q 14 oH = =o ie) ° oS & rot = We have here a faulted synclinal of Skelgill Beds brought beneath the Coniston Limestone by a fault which is shown, by the way in which it crosses the beck, to have a reversed hade. We would suggest that the fold which here brings up the Coniston Limestone has decreased to such an extent higher up the gill that there it only affects the Lower Skelgill Beds, repeating them upon themselves, a supposition for which we have given other evidence. If this is really the case, and the facts favour it strongly, the great apparent thickness of the Lower Skelgill Beds in Yewdale Beck and other sections is illusory. : The syncline of Skelgill Beds rapidly dies out to the south, as does the Coniston-Limestone anticline to the north, and the main outcrop of the Skelgill Beds proceeds to the south-west in a line ON THE. STOCKDALE SHALES. 697 continuous with the morass represented at the right-hand side of our section. Though the depression can be followed to Broughton Mills, no exposure of the Skelgill Beds occurs, and only a few iso- lated patches of the Browgill Beds are seen. Before leaving this section at the farm, we would add some further particulars. The ashes seen in the extreme left of the section belong to a massive volcanic series, probably at this point below the whole of the Coniston-Limestone series, though, as is well known, similar beds are elsewhere intercalated between different members of the Coniston Limestone. Along the fault between the volcanic rocks and the Skelgill Beds a felsite-dyke has burst, and this has baked the Graptolitic shales to a deep crimson colour. Specimens of this crimson shale can be obtained with the usual fossils of the Dimorphograptus-zone, viz. : — Dimorphograptus confertus, Nich., Monograptus revolutus, Kurck, and M. tenuis, Portl. The crimson shales appear to be included in the felsite ; and on the hillside south-east of the stream the normal black Dimorphograptus-shales are seen dipping to the south-east, and containing the same fossils as the altered portions. Above this is a gap with no rock seen, and further up the hill we meet with voleanic rocks like those at the extreme north-west of the section, succeeded on the brow of the hill by normal Coniston Limestone. This dips towards the morass seen in the right-hand portion of the section, and under this either the Skelgill Beds are concealed or the strike-fault which so frequently affects them runs, for on the other side of the morass the ordinary Browgill Beds are found passing into the normal Coniston Flags of the district without any further disturbance. It has been observed that no section of any importance in the Stockdale Shales occurs between this point and Broughton Mills. Below the Mills an alluvial tract occupies the position of the Stock- dale Shales; and although the underlying Coniston-Limestone series is traceable at intervals along this line of strike as far as Millom, no further exposure in the Stockdale Shales is found on the west side of the Duddon estuary, though there is room in some places for the beds of this series between the Coniston Limestone and the Coniston Flags ; but in such cases the rock is concealed by alluvium. Poaka Beck. On the east side of the Duddon estuary an anticlinal fold brings up the Stockdale Shales in the neighbourhood of Dalton-in-Furness. In a paper in the ‘ Quarterly Journal’ for 1878 one of us refers to two specimens of Stricklandima lirata as coming from the Browgill Beds of Rebecca Hill. The shale in which they occur is certainly like that of the Browgill Beds, but we have never met with any Brachiopods other than “extremely minute ones in these beds, and we think it possible that the specimens preserved in the Wood- 698 MR. J. E. MARR AND DR. H. A. NICHOLSON wardian Museum have really been derived from one of the mud- stone-bands of the Skelgill Beds. The only section in the Skelgill Beds of the east side of Duddon which is known to us occurs in Poaka Beck, just above Bridge End, 3 miles to the north of Dalton-in-Furness. The section seen there is shown in fig. 11. Fig. 11.—Sectron at Poaka Beck. (Scale 12 feet to 1 inch.) Fault Breccia. Aa 2?, The lowest beds seen are greatly disturbed, rusty-brown, weathered shales, with many ill-preserved Graptolites, of which the only one which we could determine was Climacograptus normalis, Lapw.; but from the general appearance of the shales we believe them to belong to the zone of Dimorphograptus confertus. Above these shales is a considerable fault-breccia and then a space in which no rock is seen. Ab 6?. Two feet four inches of blue mudstone, the Barren Band or the summit of the Ampyza-aloniensis zone. Ac1?. Very dark ferruginous mudstones, 8 inches thick, with few Graptolites. Weobtained Monograptus distans, Portl., M. Nicol, Harkn., and Climacograptus normalis, Lapw. We believe this to represent the M.-Clingani band, but did not see that fossil therein. Ac2?. Pale green mudstone 1 foot thick. Either the Ampyz- alontensis zone or a pale band interstratified with the M.-spinigerus shales. Ac 3. Banded black, grey, and pale mudstones, 2 feet 2 inches in thickness, with abundance of Monograptus spinigerus, Nich., and undvubtedly representing the M.-spinigerus zone. Ac4. Blue mudstones of the Acidaspis-erinaceus zone, of which only the lowermost 6 feet are visible. At some distance above this on the hillside is a quarry in B, the pale shales of the Browgill Beds, which here contain unusually large cubic crystals of pyrites and many small undeterminable Brachiopods. There is little doubt that the bed we have marked Ac 1 is really the MZ-Clingani band, otherwise the spinigerus-zone would be of unusual thickness here, and we shall eventually point out that the beds tend to thin out in this direction. : The whole section is of little interest, and we call attention to it as it is the most southerly exposure of the Stockdale Shales in the Lake-district proper. ON THE STOCKDALE SHALES. . 699 Having now traced the beds along their line of outcrop in the Lake-district, we may proceed to a description of the beds in those outlying districts to which we have previously referred. Swindale Beck, Knock. If we continue the line of strike of the Stockdale Shales in an east-north-easterly direction from Shap Wells it would pass near the village of Knock, under the Pennine Chain, and close to this village the Stockdale Shales actually do occur in Swindale Beck, and in a tributary which enters it from the north-east. In this tributary (Rundale Beck) some very black shales are seen, evidently separated from the surrounding rocks by aseries of faults, and having a strike discordant with that of the adjacent rocks. The beds are lithologically like those of the fimbriatus-zone, and though we have not found the characteristic fossil of that zone, there is no doubt from an examination of the appended list that the beds really do appertain to it. Monograptus leptotheca, Lapw. Petalograptus ovatus, Barr. eyphus, Lapw. Diplograptus sinuatus, Wich. tenuis, Porti, —— Hughesii, Nich. —-— triangulatus, Harkn. ? Climacograptus normalis, Lapw. Rastrites peregrinus, Barr. In Swindale Beck itself the highest Lower Paleozoic beds seen belong to the Lower Coniston Flags, and between these and the Coniston-Limestone series is a tolerable section of the Browgill Beds, though the section is by no means complete. The Upper Browgill Beds do not appear prominently, but the two Graptolitic zones of the Lower Browgill Beds are well represented. We could find no representatives of the Skelgill Beds in the main beck, and the lowest Graptolitic zone which isin the pale shales is only 1 inch thick; but it has yielded a great number of beautifully preserved specimens of Monograptus turriculatus, Barr., along with Mono- graptus lobiferus, M‘Coy, and Rastrites distans, Lapw., showing that we have here the turriculatus-zone. This band occurred just above the level of the water, and is now almost entirely worked out, though the stream will doubtless cut a new exposure in time. A few feet above it are a series of black shales interstratified with pale shales and yielding the fossils of the crispus-zone. We have ob- tained from them :— Monograptus broughtonensis, Cyrtograptus? spiralis, Gein. Nich. Retiolites Geinitzianus, Barr. pandus, Lapw. ef, macilentus, Zorng. Cyrtograptus Gray, Lapw. The Browgill Beds are here traversed by some mica-trap dykes, and the pink staining has affected the Lower Browgill Beds, a cir- cumstance of unusual occurrence. 700 - MR. J. E. MARR AND DR. H. A. NICHOLSON Spengull. The existence of an anticlinal in the neighbourhood of Sedbergh was long ago described by Professor Sedgwick, and asaresult of __ this fold we meet with beds of the Stockdale-Shale series in many of the streams in the valley of the Rawthey, on the north side of the anticlinal. By far the most complete of these sections is exhi- bited in a stream which runs down from Spengill Head in a southerly direction towards the farm of High Haygarth, about 5 miles east of Sedbergh, on the road to Kirkby Stephen. We shall speak of this stream as Spengill, a name which is more euphonious than that by which the stream is designated on the map of the Ordnance Survey. About 2 miles north of High Haygarth the main stream coming from the north is joined by a feeder from the north-west, and at the point of junction of the two streams a cart-track crosses a little ford. Above this an admirable exposure of the Stockdale Shales is afforded by a deep gully, and still further up in the bed of a shal- lower valley. A few yards below the ford a hard calcareous grit, one foot in thickness, was first pointed out to one of us by Professor Hughes; it occurs in a weathered exposure on the heathery right - bank of the stream, by the side of the cart-track, and here fossils can readily be procured from it. In the Woodwardian Museum Cornulites. Strophomena siluriana, Dav. Orthis protensa, Sow. Meristella crassa, Sow. ? —— biforata, Schloth. are preserved from this bed. The first four of these are found in the Ashgill Shales. This grit-band is succeeded by several feet of leaden-blue, cleaved, non-laminated mudstones, with abundance of Phyllopora Hisingerit, M‘Coy, and Myelodactylus, sp. They are quite similar to the Ashgill Shales of other areas, and we believe : that both these shales and the grit are referable to that horizon. Some little distance above the ford a very hard limestone band, 6 inches thick, is exposed on the right bank of the stream just above water-level. It contains a few Crinoids, and we would take this as the base of the Stockdale Shales and as the equivalent of the Atrypa- jflewuosa band. The section of the Stockdale Shales of Spengill is given in fig. 12, where this bed is marked Aa 1. Aa 2. Immediately above this limestone are black, crushed shales with Climacograptus normals, Lapw., and Monograptus revolutus, Kurck, aud they pass into a series of greyish-black, very fissile shales, much stained with ferruginous matter, and crowded with . Graptolites. These shales are seen on both sides of the stream. These beds dip at an angle of about 60° to the north, and the direction of dip is maintained by the overlying beds, though its amount becomes less in the upper portions of the Stockdale-Shale series. There is a thickness of at least 25 feet of the blackish shales, and as the dip is fairly constant it does not appear that the beds have been repeated. The fossils in these shales are :— | Monograptus revolutus, Kurck. Dimorphograptus confertus, Nich. tenuis, Portl. Swanstoni, Lapw. attenuatus, Hopk. Diplograptus vesiculosus, Nich. — Sandersoni, Lapw. modestus, Lapw.? ON THE STOCKDALE SHALES. It will be seen that this list is identical with that of the Graptolites from an exposure of the confertus-shales a little below the Upper Bridge, Skel- gill. As at that place, Demor- phograptus confertus is rare and D. Swanstont abundant. We think it highly probable that the seams containing the abun- dance of D.confertus are crushed out from between these shales and the underlying calcareous band; but it is just possible that they may be on a higher horizon. Whatever be the relative position of the shales in which D. confertus is abundant and D. Swanstoni apparently absent, and those in which the latter is abundant and the former rare, there can be no question that the two belong to one Graptolitic zone, occur- ring always between the zone of Atrypa flexuosa or of its equivalent, that of Diplograptus acuminatus, and the zone of Monograptus fimbriatus. Ab 1. The actual passage between the confertus-shales and the succeeding Graptolitic shales is not seen; but we are disposed to believe that the junction is here an unfaulted one. If so, this is the only locality we have met with where such is the case. There is no great gap be- tween the confertus-shales and the overlying beds, and the two are dipping with perfect conformity. Moreover if a strike-fault did occur here, we believe we should find traces of it, as it is usual to get a considerable breccia developed at that point, and this breccia would almost certainly be ex- hibited. Be that as it may, the measured thickness of the Q.J.G.8. No. 176. Ashgill Shales. Aa2. Adl. Ad 2- Ac2, b io} rs o— ° On a i & ES) bo 2] = e e e e ON oF Nh os er OO OOOO em™m™ =. of eS Ee eee f 17 2 eee eee nen mnen news serene ae cere ens errr rer ee na nec ee ne eeeneew ener eee eee eee ee te aa aceon en eee en=~--- Savp iT mo4sIu0g Ac3. Calcareous eds. see casera! LIOWEL MOL. Waterfall. Upper Maz. oe “yprbuady u2 uonrg— ZT “Sti CYOUL T 04 Joox GY qnoqe eyeag) 702 MR. J. E. MARR AND DR. H. A. NICHOLSON confertus-beds is greater here than in any other section except where we have indications of repetition. The shales above the confertus-beds are also Graptolitic and are very similar to the confertus-shales in lithological characters, being fissile and having a ferruginous staining due to weathering. The fossils are different :— Monograptus fimbriatus, Nich. Rastrites peregrinus, Barr. gregarius, Lapw. Diplograptus sinuatus, Nich. attenuatus, Hopk. Climacograptus normalis, Lapw. triangulatus, Harkn. There is no doubt that these are the shales of the fimbriatus-zone, and another argument of the succession being here complete is fur- nisbed by the fact that Monograptus triangulatus is here very abun- . dant, while elsewhere it is rare. It will be eventually seen that this form marks the lowest horizon of the representatives of the Middle Skelgill Beds in other areas. The beds of the Middle Skelgill group above the finale are extremely disturbed in this section. They are best exposed on © the left bank of the stream. A crush occurs between the jimbriatus- shales and the succeeding beds, which are blue mudstones, probably forming the top of the zone of Phacops glaber, as the succeeding shales appear to belong to the convolutus-zone. In this case the zones of Encrinurus punctatus and Monograptus argenteus are entirely faulted out. As our time for examining this section was limited, and the Middle Skelgill Beds seemed to be of normal character, we did not work them out in detail, a task of some difficulty owing to their extremely folded condition. The beds which we refer to the convolutus-zone have the ordinary appearance of the shales of that horizon, and exhibit the very marked olive-brown staining which distinguishes its deposits. Above them are some blue mud- stones ; but a considerable fault occurs between the Middle Skelgill Beds and the lowest exposed beds of the Upper Skelgill group. The section of the representatives of this group is one of considerable importance, and we worked it carefully. Ac38. Returning to the right bank, an angle of the bank is seen jutting out into the stream at some little distance below a waterfall. In this angle some very black shales, interbedded with lighter bands, appear for about 2 feet below the overlying mudstones. The upper- most black shales have well-preserved Graptolites, including :— Monograptus spinigerus, Nich. Rastrites urceolus, Richter. distans, Portl. Diplograptus Hughesii, Nich. leptotheca, Lapw. Climacograptus normalis, Lapw. lobiferus, M‘Coy. Monograptus spinigerus occurs in the usual numbers, and indicates that this is undoubtedly the zone characterized by that species. The succeeding beds of the Upper Skelgill group offer interesting differences from those of other sections. Ac 4. No less than 30 feet of blue mudstones overlie the shales of ON THE STOCKDALE SHALES. 703 the spinigerus-zone, without the intervention of any Graptolitic shales. They contain many calcareous, nodular bands towards the summit, forming an impure limestone some 10 feet in thickness. Our attention was first called to this calcareous band by Prof. Hughes, and a number of fossils occur in it. We have found :— Lindstreemia, sp. Cheirurus bimucronatus, Murch. Favosites. Illenus Bowmanni, Salt. Phacops elegans, Beck & Sars. Leptena quinquecostata, M‘Coy. The band strongly resembles that of the zone of Acidaspis erina ceus as seen at Torver Beck, and there is no doubt as to the identity of the two deposits, though the characteristic Acidaspis has not yet turned up in the Spengill section. Ac5. The zone about to be described has been found in no other section in the district, and indeed there is no doubt that it is absent all along the line of outcrop of the Stockdale Shales in the central district, as we have frequent opportunity of seeing a passage from the underlying beds into the Browgill group. A waterfall in the Spengill section here separates the lower ravine which we have described from an upper one, and this waterfall is found to be determined by a mass of hard blue mudstones, which also form cliffs on each side. The cliff on the right bank is seen to form a projecting cornice, and immediately under this cornice 4 inches of very hard black Graptolitic shale occur. From this band we extracted a number of specimens of Rastrites maximus, Carr., and one example of Monograptus jaculum, Lapw. No doubt other fossils also occur; but the spot is a dangerous one, on account of the broken nature of the rock forming the cornice. These beds strike across the stream at the foot of the waterfall, and are again seen at the foot of the cliff on the left bank; but pieces of the shale are difficult to extract here. The characteristic Rastrites maximus was found here also. The blue mudstones above this band are 24 feet thick, and at the summit of them and forming the top of the cliff over which the water falls is another band, also 4 inches thick, very similar to the former, though lighter in colour, and likewise con- taining numerous examples of Fastrites maximus. We speak of these black shales with the intervening mudstones as constituting the Zone of Rastrites maximus. The upper black band of the R.-maximus zone is at once suc- ceeded conformably by the lowermost Browgill Beds. Ba 1. The Browgill Beds occupy the upper ravine, which runs obliquely to the strike, so that we meet with a generally ascending succession, until we reach a second waterfall, which marks the upper end of this ravine. Above the &.-maximus beds are nineteen feet of ordinary pale green shale, after which we meet with four feet of pale green and bluish-grey bands with some thin dark seams. These are well seen on the right bank of the stream a little above water-level, and a few yards above the waterfall, where they are extremely conspicuous, owing to the stripes of the different-coloured bands. Above them are three feet of unstriped bluish-grey beds, on 342 704 MR. J. E. MARR AND DR. H. A. NICHOLSON the top of which rests a thickness of four inches of dark-grey, rather ferruginous shales, with Monograptus turriculatus, Barr., and Rastri- tes distans, Lapw., the former abundant and the latter rare. This bed is seen on both sides of the stream. Above it one foot two inches of pale shale separate it from another greyish-black band, four inches thick, with :— Monograptus turriculatus, Barr. Rastrites distans, Lapw. —— Hisingeri, Barr. One foot six inches of pale shale intervenes between this and a third black band, also four inches thick, in which we saw no UM. turri- culatus, but Rastrites distans was procured therefrom. These two upper zones are well seen at the top of a buttress of rock on the left bank of the stream, and also higher up, to the east of the waterfall. Fourteen feet of pale shale ensue, and then a con- cretionary grey bed about three inches thick, in which are no fossils, is met with, forming the extreme summit of the cliff over which the water falls at the head ofthe second ravine. This band may be traced along the lateral cliff on the right bank of the stream, and below the waterfall, and the ascending section followed from it. The beds below it are inaccessible on this side, until near the bottom of the dip where the banded rock already noticed occurs. Above the concretionary band we find in this cliff:—Green beds with fine shaly bands, many of them stained pink, and in some of which Graptolites are seen, but are poorly preserved, seventeen feet. This shaly bed, five inches thick, and stained pink, crowded with Monograptus turriculatus, Barr., contains also :— Monograptus rectus ? | Retiolites obesus, Lapw. A total thickness of 61 feet 4 inches has been measured between the top of the zone of Rastrites maximus and this point, and we refer these beds to the zone of Monograptus turriculatus. Ba 2. Above the waterfall, the stream runs through a shallow valley, with exposures on each bank, but mainly on the left one. Above the uppermost turriculatus-band, we get thirteen feet of green beds with fine shaly bands, at the top of which there is reason to suppose the existence of a fault. A thin blue-black band, sometimes stained pink, is s next met with, and this yielded :— Monograptus pandus, Lapw. Cyrtograptus? spiralis, Gein. griestonensis, JVicol. This band is much baked by a dyke, and fossils are difficult to extract. It is two or three inches thick. Two or three feet of pale shale lie between this Graptolitic shale and a felsite sheet breaking along the bedding and having a thickness of about twenty feet, and above it are twelve feet of ordinary pale shales somewhat baked; the next band seen is very fine, grey, gritty shale three inches thick, one bedding-plane of which is covered with ON THE STOCKDALE SHALES, 705 the beautiful little Cyrtograptus Graye, Lapw., and the bed yielded also Monograptus pandus, Lapw., and a specimen of Retiolites Geinitz- zanus, Barr. The band is seen on the grass- and heath-covered left bank, and is succeeded by sixteen feet of ordinary pale shales, after which is a gap crossed by a footpath, in which there is room for about ten feet of rock. We refer the beds between the uppermost M.-turriculatus band and this point to the zone of Monograptus crispus. There is little doubt that some of the beds are faulted out, either along the line of the dyke or below it, or both, and the shales which are seen are so baked that delicate forms like Monograptus crispus, if they originally occurred there, would be obliterated. The other species found all belong to the crispus-zone, and the zone is found in the immediate vicinity of this gill, About forty-four feet of rock has been measured belonging to this zone. At the same time we would refer to the grey gritty shale as the Cyrtograptus-Graye band, believing it to form the very uppermost part of the crispus-zone. Above the footpath the section is less con- tinuous. Bb. We believe that the footpath marks the line of separation between the Lower and Upper Browgill beds. Above the footpath are fourteen feet of green shales, passing up into a great mass of red shales, with interstratified grits, which become greenish grey towards the summit, the whole having a thickness of about 160 feet. We have obtained no fossils from this portion, which is quite similar to the Upper Browgill group as de- veloped elsewhere. It will be seen that the Browgill Beds of this locality have a total thickness little short of 300 feet, and for diversity of character and richness of fossils they are unexcelled in any other part of the district. fiwer Rawthey. The following Graptolites from black shales interstratified with pale green shales are preserved in the Woodwardian Museum; they were collected by Prof. Hughes at Rawthey Bridge and undoubtedly belong to the crispus zone :— Monograptus exiguus, Wich. Cyrtograptus spiralis, Gee, — pandus, Lapw. Petalograptus palmeus, Barr. The Browgill Beds are all well seen in Hebblethwaite Gill, on the south side of the Rawthey valley, and nearer Sedbergh than the last locality. Professor Hughes has obtained Monograptus turriculatus from this stream, and we found bands with :— Monograptus pandus, Lapw. | Petalograptus palmeus, Barr. Cyrtograptus ? spiralis, Gein. Retiolites Geinitzianus, Barr. So that the two Graptolitic zones of the Browgill Beds appear to be here present. 706 MR, J. E. MARR AND DR. H. A. NICHOLSON Austwick Beck, near Settle. The section here is described by Prof. Hughes in the ‘ Geological “Magazine, vol. iv., and one of us has given additional notes in the ‘ Geological Magazine,’ dec. iii. vol. iv. The Bala Beds are succeeded here by a conglomerate of variable thickness, passing up into a lime- stone which contains Trilobites found in different zones in the Stock- dale Shales; this limestone is immediately followed by the Lower Coniston Flags. Hither the Skelgill Beds are absent, and the repre- sentatives of the Browgill Beds rest unconformably on the Bala Beds, or the conglomerate and succeeding limestone represent the whole Stockdale-Shale series. We shall revert to this question in the sequel. hibble Valley. At Crag Hill, near Horton, Prof. Hughes describes a breccia-like limestone overlying the Coniston Limestone, in which he records the occurrence of Favosites. One of us has examined this. ; There certainly is a strong resemblance between this limestone- | conglomerate and the conglomerate of the valley, and the former like the latter occurs between the ordinary Coniston Limestone and the Lower Coniston Flags. We agree with Prof. Hughes therefore in referring the Crag-Hill calcareous conglomerate to the Stockdale- - Shale series. Teesdale. We complete our description of the Stockdale Shales of the north of England by referring to the probable existence of Browgill Beds at Cronkley Mill, as described by Messrs. Gunn and Clough. The accompanying figure (fig. 13) gives a general section through the Stockdale Shales, showing the full development of the zones. The thickness of the whole series varies from two hundred and fifty feet to over four hundred feet, the latter thickness being that of the beds in the Sedbergh district. We append a table (pp. 726-729) showing the distribution of the fossils in the different zones of the Stockdale Shales. § V. Comparison WITH CORRESPONDING BEDS IN OTHER AREAS. One noticeable feature about the Stockdale Shales is the inter- ealation of non-Graptolitic beds containing more highly organized fossils with the Graptolite-bearing shales. We are thus enabled to compare the series with the corresponding Graptolitic beds of other areas as well as with non-Graptolitic ones. We will commence with a comparison of our beds with the corresponding Graptolitic shales of the other areas, and we naturally start with those of the South of Scotland, which have been so admirably and clearly worked out by Professor Lapworth. It is hardly necessary to insist on the similarity between the Skelgill Beds and the Birkhill Shales, and between the Browgill Beds Q.J.G.S. vol. xliv.] STOCKDALE SHALES. Browgill Beds. Skelgill Beds. a Nn “~ [Zo face p. 706. Fig. 13.— Vertical Section of Stockdale Shales. (Scale about 1 inch to 50 feet.) Bb 2— Coniston Flags. i a Ba 1— ~ | Ashgill Shales. —Zone of Monograptus crispus. —Zone of Monogruptus turriculatus. —Zone of Rastrites maximus. —Zone of Acidaspis erinaceus. J none of Monograptus spinigerus. “Zone of Ampyz aloniensis. —Clingani-Band. ~Barren Band. —Zone of Monograptus concolutus. —Zone of Phacops glaber. —Zone of Monograptus argenteus. —Zone of Encrinurus punctatus. —Zone of Monograptus fimbriatus. —Zone of Dimorphograptus confertus. —Zone of Diplograptus acuminatus. ON THE STOCKDALE SHALES, 707 and those of the Gala group; indeed, Prof. Lapworth has himself shown the relationship of these in his papers on “The Moffat Series ”* and ‘* On the Geological Distribution of the Rhabdophora’’t ; but a most remarkable similarity between the Scotch and North of England beds becomes apparent when we come to compare the zones of each, for not only are the fossil contents of the zones of the two areas remarkably similar, but a decided resemblance can be traced when we compare the lithological characters. The Lower Skelgill Beds are flaggy beds like those of the zones of Diplograptus acumimatus and Diplograptus vesiculosus at the base of the Birkhill Shales, The Middle Skelgill Beds resemble the Monograptus-gregarius zone, not only in the blackness of the shales, but also in the develop- ment of interstratified mudstones containing calcareous nodules. The Upper Skelgill Beds resemble the zones of Monograptus spingerus and Rastrites maximus in that the beds are generally of a lighter colour than those of the underlying zones. The Grits and pale Shales of the Browgill Beds are comparable with similar rocks in the Gala group. Comparing the zones in detail :— 1. The zone of Diplograptus acwminatus at the base of the Birk- hill Shales is like the same zone at the base of the Skelgill Beds. Both are slightly calcareous flaggy shales, and the two fossils found in the acuminatus-zone at Browgill, viz. Diplograptus acuminatus, Nich., and Chimacograptus normalis, Lapw., both occur in the Birkhill zone. ‘The two other species found in the Birkhill zone, Dimorpho- graptus elongatus, Lapw., and Diplograptus vesiculosus, Nich., have not yet turned up in the Lake-district ; but possibly a further search will result in their discovery. 2. The zone of Diplograptus vesiculosus, Nich., is represented by the zone of Dimorphograptus confertus, Nich. In both areas the beds consist of black flagstones. Of the fossils found in this zone in the Lake-district, Monograptus tenuis, Portl., M. attenuatus, Hopk., Dimorphograptus elongatus, Lapw., Diplograptus vesiculosus, Nich., and Climacograptus normahs, Lapw., are also found in the corresponding Birkhill zone. Monograptus revolutus, Kurck, M. Sanderson, Lapw., M. lepto- theca, Lapw., Dimorphograptus confertus, Nich., D. Swanstoni, Lapw., and Diplograptus longissimus, Kurck, have not been recorded from the Birkhill Shales, but they are mainly found on one horizon in the Lake-district, and may eventually turn up in the Scotch area. 3. The zone of Monograptus gregarius, Lapw., is undoubtedly represented by the zones of Monograptus fimbriatus, M. argenteus and M. convolutus, with their interstratified mudstones. In all these zones Monograptus gregarius is abundant, and it is practically limited to them, only one specimen having been discovered in the Chngani- band. Of the thirty-three species of Graptolites found in these zones in 7G) 0. G.S. xxxly, Pool, t+ Ann. & Mag. Nat. Hist. ser. 5, vol. iii. p. 39. 708 MR. J. E. MARR AND DR. H. A. NICHOLSON the Lake-district, at least twenty-one also occur in the gregarius- zone of Scotland, whilst only four species found in the latter aefa are absent from the representative zones in the Lakes. The lithological resemblances have been already commented upon, and there can be no hesitation in correlating the Middle Skelgill Beds of the Lake- district with the zone of Monograptus gregarius of Scotland. 4, The succeeding subzone of Petalograptus cometa is not differ- entiated in our area. It appears to have thinned out; it is partly replaced by a mudstone band, or was formed contemporaneously with the uppermost portion of the convolutus-beds of the Lake-district ; the latter contain cometa rarely, and all the forms found in the cometa-zone are also found in our convolutus-zone, with the exception of Rastrites capillaris, Carr., which is recorded in Prof. Lapworth’s list at page 323 of his paper on the Moffat Series, but not in the general list at page 328. 5. The Clingani-band, which occurs at the base of the spinigerus- zone in Scotland, may be compared with our Clingani-band. Three of the four forms mentioned by Prof. Lapworth are found also in our band. The Birkhill zone of Monograptus spinigerus, on the whole, bears a very striking resemblance to the zone containing this form in abun- dance in the Lake-district. The Clingani-band at Eldinhope Ruin is succeeded by 6 feet of soft greenish-grey shales without Graptolites. At Skelgill it has above it the 4 feet 6 inches of blue mudstones constituting the zone of Ampyx aloniensis. The many-coloured shales above are quite comparable to those of the upper part of the spini- gerus-zone in Scotland, even to the occurrence of the lozenge-shaped patches on the rough surfaces of the harder beds. Of the Graptolites from the spinigerus-zone of the Lake-district, ten out of sixteen are found in the Birkhill Shales, or more than this if we count also those of the Clingani-band in our area, whilst three which occur in Scotland have not yet been found in our zone. 6. The abundance of Rastrites maximus in our uppermost zone of the Skelgill Beds shows its relationship to the highest zone of the Birkhill Shales. A fuller examination of the beds in the Spengill section would almost certainly result in the discovery of a more abundant fauna. It is noticeable that the mazimus-beds occur in pairs in Scotland ; and Prof. Lapworth states that at Craigmichan only one pair is visible. We also have a pair of these beds separated by many feet of mudstone. In this comparison we have not yet insisted upon what we con- sider of far more importance than the occurrence of a certain percentage of fossils common to the corresponding zones (for the percentages would certainly be considerably increased after further work), namely, the great abundance of the characteristic forms of the different zones in the corresponding order, We find :— ON THE STOCKDALE SHALES. 709 In the Lake-district :— In the Moffat area :— 1. Diplograptus acuminatus, common. D. acuminatus, common. 2. D. vesiculosus, common, D. vesiculosus, common. D. acuminatus has disappeared. 1D acuminatus has disap- peared. . Monograptus gregarius, common. { M. gregarius, common. Diplograptus vesiculosus, very rare. D. vesiculosus, very rare. . Lack of abundance of Petalograptus Abundance of P. cometa. cometa, . Abundance of Monograptus spinigerus. Abundance of M. spinigerus. 1 sdecimen of M. gregarius. Absence of M. gregarius. . Abundance of Lastrites maximus. Abundance of A. maximus. oOo oO - os Furthermore, our divisions of the Middle Skelgill Beds are, at any rate partially, suggested by an examination of the mode of occurrence of the Graptolites in the gregarius-zone of Scotland. Prof. Lapworth states that in his district ‘* Monograptus Sanderson (Lapw.) and M. finbriatus (Nich.) are unknown above the central line” of the gregarius-zone. In our country they are found in the fimbriatus- zone, but not above it. Again, “ Monograptus triangularis (Harkn.) occurs only in the neighbourhood of the nodule-band ” which is near the centre; with us it is only found in the fimbriatus-zone. Lastly, “neither Rastrites peregrinus nor Diplograptus vesiculosus reach the summit of the group.” We find the former confined to the fimbri- atus-zone, and the latter rarely occurring in it, and not higher. Passing now to the Browgill Beds, we find at first sight less striking resemblances in the more minute subdivisions ; but this is partly due to the reference of the peculiar Monograptus discus to M. turriculatus, Barr., and the inclusion of Monograptus pandus with M. priodon in the published lists. Prof. Lapworth, in his paper on the ‘* Geological Distribution of the Rhabdophora,” p. 41, gives a list of fossils from the Gala group. ‘Twenty-one species are there enumerated, of which twelve have been discovered by us in the Browgill Beds, and of these twelve only two pass down into the Skelgill Beds, and these only occur in the upper group. We cannot find any record of the separation of the twrriculatus-beds as a distinct zone; they undoubtedly form such in the Lake-district, and the two forms Monograptus turriculatus, Barr., and Rastrites distans, Lapw., appear to be strictly limited to it in that area. The fossils of the zone of Monograptus crispus are mostly found in the Gala group, and WV. eaiguus 1s a very common form in the two areas. In Prof. Lapworth’s paper on “ The Girvan succession ” * the equivalents of the Gala group, the “ Crussopodia-group,” are divided into Lower Penhill Shales with Monograptus ewiquus &c., Middle Penhill flags and greywackes, in which the Graptolites of the pre- ceding beds recur, and Upper Penhill mudstones, or Graye-beds, with Cyrtograptus Graye and Retiolites Geimtzianus. It has already been pointed out that although we are unable to separate the Graye- beds and the beds with Retiolites Geinitzianus from the beds of our crispus-zone, we have found that they are limited to the upper * Q. J. G.S. vol. xxxviii. p. 652. 710 MR. J. E. MARR AND DR, H. A. NICHOLSON part of it, and Cyrtograptus Graye, especially, occurs in such vast abundance in one seam at the very top of the crispus-beds, that we have thought fit to allude to this seam especially as the Graye-band. Our comparison of the Stockdale Shales with the Birkhill and Gala groups renders unnecessary a minute comparison with the similar Graptolitic deposits in other areas. Such a comparison has already been successfuly instituted by Prof. Lapworth in his papers on the “ Geological Distribution of the Rhabdophora” and on “ The Moffat Series.” We merely proceed to add a few supplementary remarks, and in the first place call attention to some researches of the late Dr. Tullberg, published since the appearance of the above-mentioned papers of Prof. Lapworth. By Dr. Tullberg’s early death science has been deprived of a most promising Graptolithologist and strati- graphical geologist, and his co-workers have lost a genial companion. In a paper “ Om Lagerfoljden i de Kambriska och Siluriska Afla- gringarne vid Rosténga ” * he suggests the following correlation of the beds of Scania and Scotland :— Brachiopod-skiffer with Phacops mucronatus, Brongn. = Lower Birkhill? Lobiferus-skiffer. = Upper Birkhill ; and divides the latter as follows :— Shales with Monograptus spinigerus, Nich., \ Diplograptus (Petalo.) cometa, Gein., M. gre- | Zone of M. gregarius. garius, Lapw., M. cyphus, Lapw., M. Sandersoni, ' = », D. cometa. Lapw., Rastrites peregrinus, Lapw., Climaco- | ,, M. spinigerus. graptus normalis, Lapw., &c. Shales with Rastrites maximus, not found in=Zone of Rastr. maximus. Scania. 39 33 Retiolites-skiffer. Shales with Monograptus crispus &c. = Gala and Grieston. The latter succeeded by Shales with Cyrtograptus Murchisoni &e. = Wenlock. A fuller comparison is made by the same author?y in a paper published in 1882. At the summit of the beds which he describes as appertaining to the Lower Silurian group or Ordovician, he places a dark-grey shale with Diplograptus, nu. sp., and Climacograptus scalaris, Lapw., and an absence of Monograptus. This succeeds the zone of Phacops mucronatus, Ang., and most probably represents our zone of Diplograptus acuminatus. The Rastrites-beds are placed at the base of the (Upper) Silurian and are divided as follows :— At the base is the zone of Monograptus cyphus, containing also a Dimorphograptus. We shall presently give reasons for concluding that this represents our zone of Dimorphograptus confertus. * Geol. Foreningens i Stockholm Férhandl. 1880, No. 59, Bd. v. No. 2. a Skanes Graptoliter: Part 1.,” Sveriges Geologiska Undersdkning, Ser. C, no. 90. ON THE STOCKDALE SHALES. val His succeeding zone of Monograptus gregarius, containing also Monograptus fimbriatus and Rastrites peregrinus, is in the position of our zone of M. fimbriatus, which contains the same forms. Above this is Tullberg’s zone of Monograptus convolutus. It also contains WM. lobiferus, M. leptotheca, M. communis, Rastrites pere- grinus, and Petalograptus folium. All these forms occur in the convolutus-zone of the Lakes, except R. peregrinus, which is replaced by 2. hybridus ; there seems therefore to be no representative of the thin argenteus-zone in Scania. The zones of Petalograptus cometa and Monograptus spinigerus are united together in Scania. Tullberg finds in this zone M. spini- gerus, M. intermedius (=discretus, Nich. 2), M. Clingant, M. argutus, Diplograptus Hughes, and Petalograptus cometa. The zone of Lastrites maximus is doubtfully represented. He refers certain shales seen at Tosterup with Monograptus turriculatus and M. crispus to this horizon ; but we believe that this and the succeeding zone of Monograptus uncinatus are really referable to the Browgill Beds. The beds which Tullberg compares with the Gala Group of Scotland, and which are therefore comparable with the Browgill Beds, are (in ascending order) :—The zones of Cyrto- graptus Gr ray ce, Lapw., Oyrtograptus? spirals, Gein., Cyrtograptus Lapworthi, Tullb., forming the base of his Cyr tograptus-beds. We feel doubt as to ’ whether these are all separable from the two upper zones of his Rastrites-beds. In our district Cyrtograptus? spiralis occurs abundantly below the band with Cyrtograptus Graye; but as the former species appa- rently ranges into the Wenlock Beds of Britain, it probably occurs in the representatives of the Gala Group, both above and below the band with Cyrtograptus Graye. We just now alluded to the zone of Monograptus cyphus as being probably referable to our zone ot Dimorphograptus confertus. In 1881, Baron Kurck described a section at the quarry of Bollerup which exhibits the zone of Monograptus cyphus and the base of the zone of Monograptus gregarius. Irom the cyphus-beds he records :— _ Monograptus cyphus, Lapw. | Diplograptus tamariscus, Nich. revolutus, Kurck. longissimus, Kurck, attenuatus, Hopk. Climacograptus undulatus, Kurck. Dimorphograptus Swanstoni, Zapw. | Discinocaris Brouniana, Woodw. cf. Swanstoni, Lapw. The second Dimorphograptus is described and figured, and agrees in every particular with a species described and figured by one of us in the Society’s Journal for 1868*, under the name of Diplograptus confertus, Nich. The discovery of more perfect specimens has shown us that this is in reality a Dimorphograptus, and we have named the zone in which it occurs after it. In the cyphus-zone at Bollerup five species of Graptolites out of the eight recorded are found also in our zone, and we have no hesitation in asserting that the Dimorpho- * “ On the Graptolites of the Coniston Flags,” Q. J. G. 8. vol. xxiv. p. 526. 712 MR. J. E. MARR AND DR. H. A. NICHOLSON graptus-confertus zone of the Skelgill Beds is the British representa- tive of the cyphus-zone of Bollerup. The lowest band of the gre- garius-zone which is seen in the quarry at Bollerup contains Mono- graptus triangulatus, Harkn., and this is a reason for supposing that the section at Spengill, where beds with Monograptus triangulatus occur immediately above the confertus-zone, 1s complete. In a former paper read before the Society in 1880*, one of the writers in describing the shales at the base of Barrande’s band EK. e. 1. in Bohemia, expressed the opinion that “‘ not only does this zone represent the Birkhill Shales, but it can, like them, be divided into a series of subzones characterized by various species of Grapto- lites,” though the actual succession of the zones was not determined. This opinion is justified by the researches of Dr. Tullberg who, in his ‘Skanes Graptoliter,’ when discussing the theory of ‘ Colonies,” gives the results of his examination of a series of specimens from these colonies, and from the corresponding beds at the base of E. e. 1. He recognizes the following zones :— 1. Zone of Monograptus gregarius, 2. Zone with M. leptotheca and M. lobiferus, 3. Zone with WM. turriculatus, and 4. Zone with Cyrtograptus? spiralis, besides others of Wenlock and Ludlow age. From Colonie Krejci he recognizes Rastrites peregrinus, Mono- graptus gregarius, M. fimbriatus, M. triangulatus, M. lobiferus, M. leptotheca, and Climacograptus scalarvs. This corresponds with the fauna of his gregarius-zone in Scania and of our fimbriatus-zone. In Colonie Haidinger he finds Monograptus lobiferus, M. triangula- tus, M. convolutus, M. communis, Climacograptus scalaris, Diyplograp- tus, cfr. foliwm, D. tamariscus, and Rastrites peregrinus. He compares this with the fauna of his zone of Monograptus leptotheca, corre- sponding with ours of M. convolutus. In Colonie D’Archiac he has recognized Monograptus lobiferus and M. triangulatus in one bed, M. proteus in another, and Cyrtograptus ? spiralis in a third, and supposes that here are representatives of his zones of M. leptotheca, M. runcinatus, and Cyrtograptus? spirals. To these we would add the occurrence of the zones of Monograp- tus spinigerus and either Rastrites maximus or Monograptus turricu- latus in the Colony of Hodkovicek, and of the former zone in the colonies D’Archiac and Haidinger. Two specimens of shale from the Lower Paleozoic Beds of Hof, Bavaria, are mounted on a tablet in the Woodwardian Museum. These pieces contain the fossils of our zone of Monograptus fimbria- tus, V1Z :— Monograptus fimbriatus, Nich, Rastrites peregrinus, Barr. attenuatus, Hofth. Diplograptus modestus, Lapw. —— tenuis, Portl. vesiculosus, Nich. —— gregarius, Lapw. Climacograptus normalis, Lapw. A comparison of the non-Graptolitic fauna of the Stockdale Shales * Q. J. G.S. vol. xxxvi. p. 604. ON THE STOCKDALE SHALES. 413 with that of similar beds is more difficult, but fully confirms the conclusions come to after examining the Graptolites. The different forms of Phyllocarida might have been considered along with the Graptolites, as they occur in Graptolitic rocks. Of these Discinocaris is found in the Birkhill Shales and their Bohemian equivalents ; whilst Peltocaris aptychoides and Aptychopsis Lapworthi are also found in the Birkhill Shales. Of the other fossils, Encrinwrus punctatus, Calymene Blumenbachii, and Leptena quinquecostata are found both in Llandovery Beds and in beds above and below them, whilst Favosites mullochensis occurs in the Llandovery Beds of the Girvan area. Phacops elegans has been recognized in the Mulloch-Hill Sand- stones (a specimen from this locality being preserved in the Wood- wardian Museum) and in the corresponding beds at the Gasworks, Haverfordwest. It also occurs in the Gala Beds of Devil’s Bridge, Aberystwith, where it was found some years ago by one of the authors. In Norway it is common in the sandstones of stage 58 of Kjerulf, which correspond in lithological characters and fossil contents with the Mulloch-Hill Beds and the beds at the Gasworks, Haverford- west. Dr. Schmidt records it from the Raikill Beds of Russia, where it is found along with other fossils occurring in Kjerulf’s 5£, and Diplograptus esthonus *. All these beds are admitted to be of Llandovery age, with the exception of the Devil’s-Bridge deposit, which is compared with the Gala Group, and therefore indirectly with the Tarannon Shales. That some of the Trilobites occurring in our Skelgill Beds do pass up into the Browgill Beds seems clear from the occurrence of many of them in the calcareous band immediately below the Coniston Flags in Austwick Beck, and we have one speci- men of Phacops elegans var. glaber from the Browgill Beds of Brow- gill, though its exact positiou was not ascertained. More Trilobites would probably be found in the Browgill Beds of the central area if the calcareous bands were further examined ; for the carbonate of lime of these beds was probably derived from Trilobites, as in the case of the Trilobitic mudstones of the Skelgiil group. The examination of the occurrence of Phacops elegans shows that it is a Llandovery-Tarannon form, and it has not been recorded from earlier or later formations. Phacops mucronatus, Brongn., occurs in the Llandovery Beds of Haverfordwest, and in the Upper Brachiopod Schists of Westrogothia. It is different from the form which occurs in the Ashgill Shales, and which seems to correspond with the form from the Lower Brachiopod Schists. Orthoceras araneosum, Barr., is found in the Wenlock and Ludlow rocks of Britain, and in the beds of Barrande’s Stage E, in Bohemia *. The other fossils are new. Of these, Ampyw aloniensis belongs to * Schmidt, ‘Revision der ostbaltischen silurischen Trilobiten,’ p. 43; and Q. J. G. S. vol. xxxviii. p. 526. T Blake, ‘ British Fossil Cephalopoda,’ p. 124. 714 MR. J. E. MARR AND DR. H. A. NICHOLSON a genus which is common in Ordovician rocks. Two species are, however, found in the Silurian, viz. :—Ampywx parvulus, Forbes, from the Lower Ludlow rocks of Ludlow, and Ampyx Rovalti, Barr., from the corresponding beds of Bohemia. It is interesting to find another form which reduces the gap between the newest Ampyz of the Ordovi- cian rocks and these diminutive forms of the Ludlow series. The fauna that most nearly approaches our Trilobite fauna of the Stockdale Shales is found in the Tarannon Shales of the Onny River. Anumber of Trilobites from these beds are preserved in the Museum of Practical Geology, and we have examined the specimens; they are :— Phacops glaber, n. var. Calymene Blumenbachii, Brongn. Cheirurus bimucronatus, Murch. | Ilenus Thompsoni, var. Encrinurus punctatus, var. are- Proétus nasiger, Edgell, MSS. naceus. Acidaspis dama, Fl. & Salt.? The first form occurs also in the Stockdale Shales; of the two latter, Proétus nasiger is very near our P. brachypygus. It appears to possess a narrower tail, and larger basal lobes to the glabella. The © specimen doubtfully referred to Acidaspis dama is near to our A. erinaceus. The glabella and free cheek only are seen in the specimens of the Museum of Practical Geology. The former issmooth, and the lobes are slightly different from our forms. The discovery of more specimens may prove that these distinctions are merely varietal in the case both of the Proétus and of the Acidaspis. VI. Remarks oN THE BEARINGS OF THE RESULTS. The Stockdale Shales have been shown to consist of from two- hundred and fifty to four hundred feet of alternating black and green shales, blue mudstones, often calcareous, and greenish-grey grits. They are divisible into a Lower group, the Skelgill Beds, consisting mainly of dark Graptolite-bearing shales alternating with lighter mudstones, which are entirely devoid of Graptolites except where they pass into the adjacent Graptolitic shales, and an Upper group haying from twice to three times the thickness of the Lower one (but probably formed much more rapidly, and therefore not of anything like the actual importance of the Lower group), con- sisting chiefly of green and purple shales with interstratified grit- bands, and a few insignificant seams of dark Graptolite-bearing shales. The Stockdale Shales are furthermore capable of being divided into aseries of zones, recognizable by their lithological characters and also by their contained fossils, these zones undergoing only a slight alteration in thickness and character when traced across the country. The lowest zone has been shown to be entirely conformable to the Ashgill Shales below, there being no discordance of strike, and the same bed of the Ashgill Shales being seen, in several remote sections, with the lowest band of the Stockdale Shales resting directly upon it. ON THE STOCKDALE SHALES. . 715 The apparent unconformity by which one of us was formerly de- ceived turns out, on examination, to be due to the existence of strike- faults. Although there is absolute conformity between the lowest beds of the Stockdale Shales and the highest beds of the Ashgill Shales, the paleontological break is complete, and it is at this point that we draw the line of division between the Ordovician and Silurian systems. Similar conformity is seen between the top of the Stockdale-Shale series and the base of the succeeding Coniston Flags, the passage being rather a gradual one, however, instead of very sudden, as in the case of the junction at the base. In all the sections described, with the possible exception of that at Spengill, the Lower Skelgill Beds are seen to be separated from the higher beds of the group by a strike-fault ; and minor faults of a similar nature are seen at higher levels. That this fault does not remove any great thickness of rock is shown :— (1) By the frequent juxtaposition of the zones of Dimorphograp- tus confertus, and Monograptus fimbriatus, which contain several species in common, (2) More particularly by the resemblances between the above- named zones and two similar zones in the Moffat area, the zones of Duplograptus vesiculosus, Nich., and Monograptus gregarius, Lapw., and the relationship of the M.-fimbriatus zone to the lower portion of the latter. As the succession is complete in the Scotch region, no important zone of rock can be concealed in that of the Lake-dis- trict. ) The occurrence of a fault of such wide extent exerting so little effect is remarkable, and we can offer proofs that the fault itself is not an ordinary one, but that it runs generally with the bedding, and that itis rather of the natureofacrush. The soft Skelgill Beds lie between the harder rocks at the summit of the Ordovician series and those of the Browgill group, and they must have given way during a process of stretching, which caused the upper beds adhering to the Browgill rocks to move over the lower beds, which have been shown to adhere to the Ashgill Shales. That such stretching has taken place is proved by the following facts :— (1) The behaviour of the strike-fault with the beds. The out- crop of the Skelgill Beds is a sinuous one, being bent into V’s in crossing the valleys, the apex of the V’s always pointing down the valleys, as the dip of the beds is always greater than the slopes of the valley-bottoms. Moreover, these valleys are usually occupied by great dip-faults, which displace the beds laterally. In such cases the strike-fault would be found to affect different beds when crossing these valleys and shifted by the dip-faults, whereas it is always found to run along the narrow band between the Ashgill Shales and the Browgill Beds. (2) The Skelgill Beds are often entirely, or almost entirely, removed. When developed in force, there is usually a section cut through them, and the narrow depressions occurring between the different sections and marked by a line of swamp, are bounded by 716 MR. J. Ee MARR AND DR. H. A. NICHOLSON the Ashgill Shales or Coniston Limestone on one side and by the Browgill Beds on the other. The Ordovician and Silurian rocks usually approach so near to each other that it may readily be seen that there is no room for more than a small portion of the whole thickness of the Skelgill Beds in the interval. The beds are there- fore now preserved as a series of lenticular patches, the main portion of the line of outcrop being occupied by little or none of them. (8) Smaller crushes of a similar nature can often be traced in a single section, as, for instance, in the case already described of the crushing-out of the shales of the argenteus-zone below the Upper Bridge at Skelgill. (4) The hade of the fault may frequently be actually seen coincid- ing with the dip of the beds; and the line of fracture is often marked by broken shale frequently further crushed into a black mud. Where the dip of the beds is different on the two sides of the fault, this is probably a local phenomenon produced by the rucking up of the lower beds during the process of sliding. (5) The occurrence of a quartz-vein along the line of movement just below the promontory near the Upper Bridge at Skelgill, which - coincides with the dip of the beds there, and the upper surface of which is completely polished by the shales which rest on it, shows that these shales have been moved over the nearly horizontal vein at this point. (6) At the Lower Bridge at Skelgill it can be shown that some 15 feet more rock has been removed by the fault in the great cliff just above the bridge than in the section just below it. Between these two sections is the small dip-fault already described, which has a downthrow to the E.N.E. on the 8.8.W. side of the stream, and one to the W.S.W. on the N.N.E. side. This looks as if the tearing away of the additional 15 feet of rock had been limited by a pre- existing joint-plane, and that on this side of the joint the lower and upper rocks had moved towards each other to fill up the gap so produced. (7) It is probably due to the same process of stretching that the great dip-faults, which frequently cause a lateral shift of the Coniston Limestone to an extent of over half a mile, rapidly die out to the south, so that beds some two miles south of the Coniston-Limestone outcrop are scarcely affected. It has been stated above that the beds of the Stockdale-Shale series undergo little alteration in character and thickness” when traced laterally. This is well shown by the remarkably exact correspondence between the shales of the zone of Monograptus argenteus, as seen in Skelgill and Mealy Gill. There is, however, a certain amount of lateral change, as shown clearly by the great thickening of the Browgill Beds between Stockdale Beck and Spengill. The variations of thickness, so far as we have been able to ascertain them by measurement, are indicated in the following table :— 717 ON THE STOCKDALE SHALES. Crispus-zone to Turriculatus-band| ... Turriculatus-bands and included mudstones............... De See Re Pale shale below lowest Zurricu- CLG SATS MS ec a hes IMG XIMUS=ZONCE eeccceccecsvccscccccves Ca Erimaceus-Zone ............++++s.s+..2.| 6’ seen SPUAGEPUS-ZONG —...scecacecevescereee| 2a" PALOTVENGIS=ZONC «ccc cecscecssscccecssecl he CHAGHTA-DANG vic. ..5enceesccccesens..| oO"! SOT TENOWANG © scivscvscvscccescee a ee Bee cee | ee St ey St es eee eee AN tes os os oS O8 o'8,| 08 ax rb) (amy) o§ os o oS re) 4 obese | ss ) Sb | ee) Ss | ae *S S & is) “ho 8 NS N& N > N Na NS AS ea S Re aS Q Ss be d Dd ‘S SS 8 S| & eee els | Fi 8) ele Ss Si Ry 'S S S | S RS q = q S| 4 vm see cee % eee * ee, aa % ° een . eee * . eee ee *% ee ° ° ee % an % oe *% * % e % ee % * : * * *% ea * ‘ * * . % 2 * s g cle ae S A 3 3 S iN ’ ‘S di SS ra te Sy eons ra ae ewe ae ee egies | ae] 28| oe NS NS NS Se os SM ele a ae i S 2 & ) pS Sy Ss > 8 > Sai ok si 3 ms 5 bs AY 5 cs = ‘(ponuryuoo) savady fo ysv7 Zone of Dimorphograptus confertus. * ““"mpooy “euerunorg stavooutost¢y ee aoaT “eyepamed ures 1 a eeeeateeettenaseeeseneseesnnen idly Peer ee ree ere ssreenseseesoey ‘unl "Yn P ‘youT ‘SISUETOOT[NUE soyIsoAT AT ree teeeeereeseseeenee ely ‘eroLeocyspurT segeenerrrassntes sae OTOROCMMOL TOT ees Dudoy, ‘snquopiovur «(9 ‘—— ‘“mdpry ‘sngseqo ‘eA ‘—— —— seer eer eerereveres "YOUN ‘gnqepaod ' WlMT ‘SNUBIZILUTOL) 807101} OIF sere esseeeerce ‘ndoT ‘StyeUTLOU Ww ‘snqnutut snydeasooeuntto ee RN ‘gnso[no1iseA —— Peep se 116, ‘Snostavure, tae yee iy vies L594) ‘snyenuis —— a elf aly ‘gnysopour -—— Teeseeseeee son sy ‘SNULISSISUOT —— de ey dig ee k2) 3), ‘Tisoyon yy “your ‘sngeurumnoe snydevasordrcy aC tes Zone of Diplograptus acuminatus. 729 ON THE STOCKDALE SHALES. * *K * * eee KOK OK OK OK * OK K K * K * eee wee sinieisis ‘UDG “UWNSOIUVAB SBLODOYJAO aman 6 Mg Span SIPC AM Sees stterees “smo ‘gagtaos +9 &-—- hoo. ‘eyeysooonbumnb vueeydory treeeeeseerens ag ety ‘esOnxoyy edAayy Teeeeeseseeseoney TUURUIMOG SNUBTTT pears SOLUTE 6 thing u u ‘snsdddygovaq snjygoag PRG uur ‘ds ‘u ‘sisuoiuoye xAdury ceecceceseccses ‘dg “IU ‘sngsnsue ramones es ektew sel xO pMlr Rood et ubuougy* ITpouquounyg ouewudTeQ evecrececcvece ‘ds "UL ‘sopro10ul “* AOU "AVA ‘SOPOTJURIV snAMATEYC) srreeses ubuoug ‘snyeuoronut ee eee eseccncees Jaqrys "IVA ‘6 "* supy £ yooog ‘suesejo sdoovyg eee ee re) ‘ds stnecesossconecneegnsenescvseesen ofa vroseeees lg tr ‘snoovurse sidseploy "9" “apy ‘snyejound snanuougy stiageeesentreeseneeees y gna QUOTeULOT] Ceres eveseesesreeseeeseeeeseee sedopiaany, ““mpooy ‘tqy4omdery sisdoqosyd-y SO eee re eeneererereseseeserrere ‘ds (a "rreesss ype ‘soproyosyde stav9009[0g ee eeee Se “mpooy ‘susId ———— st eceeerseeceeseesesessecewos Gig 6 730 MR. J. E. MARR AND DR. H. A. NICHOLSON EXPLANATION OF PLATE XVI. Unless otherwise stated, the figures are of the natural size. Fig. 1. Phacops elegans, Boeck & Sars: internal cast of glabella, Glaber-zone, Skelgill, x 2. 1a. Ditto: asmall tail, x 2. 2. Ditto: from a wax impression of intaglio of head and penis body- rings, Hrinaceus-zone, Torver Beck. 3. Ditto: internal cast of a nearly complete specimen, Gaber-zone, Skelgill. 3a. Ditto: glabella and cheek of the same specimen, from a wax impres- sion of internal cast. 3b. Ditto: diagrammatic sketch of incurved lower margin of cheek of the same specimen, showing cavities for the reception of the extremities of the pleurze, x 4. . Ditto, var. noy. glaber: internal cast of tail, Glaber-zone, Skelgill. . Phacops mucronatus, Brong.: internal cast of glabella, Aloniensis-zone, Browgill. . Ditto: tail from same zone and locality. Cheirurus bimucronatus, var. nov. acanthodes: esi and cheek, Glaber-zone, Skelgill, x 2. . Ditto: tail, restored, from a second specimen, same zone and locality. . Cheirurus moroides, n. sp.: from a wax mate of an external mould - of the glabella, Glaber-zone, Skelgill, x 2 aoe 10. Ditto: from a wax impression of an external mould of the glabella, Glaber-zone, Skelgill. 10a. Ditto: details of ornamentation of the same, highly magnified. 11. Acidaspis erinaceus, n. sp.: Erinaceus-zone, Torver Beck, X 2. 12. Ditto: a younger specimen, same zone and locality, x 2. 13. Harpes judex, nu. sp.: slightly distorted, the wrinkles on the centre of the glabella being apparently due to this, Aloniensis-zone, Skelgill, 14. Ditto: a crushed head, showing the venose structure, Glaber-zone, Skelgill. 14a. Ditto: a portion of the same specimen, highly magnified. 15. Harpes angustus, n. sp.: head, and cast of portion of body, Aloniensis- zone, Skelgill, x 2. 16. Ditto; internal mould of head, Glaber-zone, Skelgill. 16a. Ditto : a portion of the same, highly magnified, showing punctations. 17. Ampy« aloniensis, n. sp.: from a wax impressicn of intaglio, Aloniensis- zone, Skelgill, x 3. 18. Proétus brachypygus, n. sp.; from a wax impression of intaglio, Alo- niensis-zone, Skelgill, x 2. 19, Ditto: Aloniensis-zone, Pull Beck, x 2. 20. Atrypa flexuosa, n. sp.: ventral valve, Flexuosa-zone, Skelgill. 20a. Ditto: the same specimen, dorsal valve. 20 6. Ditto : ditto, anterior view. Norr.—In fig. 2 the axis should be extended through the lowest Ganperfect body-ring. In fig. 19 the glabella-lobes are made too wide. COCO NSIS oh Discussion. The Prestpent observed that the more minute details of strati- graphical geology were as important as divisions of wider range, especially in the Paleozoic rocks. He referred in illustration to the work done in Bohemia by one of the Authors. | Prof. Lapworrs looked forward to the day when the existence of these Graptolite-zones in Lower Paleozoic rocks would be generally acknowledged, and they would be employed as a basis for classifi- ON THE STOCKDALE SHALES. 731 cation and mapping. He remarked that the thin Moffat series of South Scotland represented the whole of the Llandeilo, Bala, and Llandovery formations in other regions. There was never any doubt as to the general age of the beds above and below these Stockdale Shales, but there had been a great controversy as to the age of the shales themselves, which the Authors had now settled. The zones they had detected in the Lake-district agree with zones already established in South Scotland, Wales, Scandinavia, &c., and it is clear that the ideas of correlation by means of such zones are destined to be generally accepted. He commented on the small thickness of these Stockdale beds, but pointed out that they were represented by very great thick- nesses of deposit elsewhere ; thus the Browgills were represented by thousands of feet in the Gala group and the Tarannon, and the Skelgills by enormous thicknesses in Girvan and Central Wales. The Authors had accomplished a piece-of work of the highest sys- tematic importance. Further zone-work was required, and it would be followed by a remapping of many areas. Prof. Hueuexs alluded to the enormous changes in the classifi- cation of the older Paleozoic rocks which resulted from Prof. Lap- worth’s researches in the Moffat area. He referred to the appa- rent absence of reappearances of fossils in the beds described, but pointed out an instance of such a reappearance of a group of fossils elsewhere. He noticed the absence of fossils in the upper Browgill Beds of Spengill, and speculated on the possible con- nexion of this with the red coloration of the rocks. He thought that we must not overlook the important question whether the ap- plication of the Graptolitic and Trilobitic verniers would give the same results. He contrasted our present knowledge with the state of things when he mapped that country. Dr. Woopwazp noted the fact that in the case of these thin beds a fauna limited to a small thickness of them was found to extend through a much greater thickness of rock elsewhere. With regard to the relative value of fossils, he pointed out that we must make the most of what we can get. Mr. Horxtnson had examined the beds many years ago, and, although he had not worked out the zones, his recollections of the general succession coincided with the views of the Authors. Mr. Erxeripee commented on the value of zones, and specially referred to Prof. Keeping’s work in Central Wales, and that of Prof. Blake on the Kimmeridge beds of the north of France and the Yorkshire Lias. Dr. Hryvr referred to the value of the large series of specimens exhibited in showing the characters of the rocks and fossils described. Mr. Rurtzy pointed out the difficulty of restoring the physical geography of these early times. Mr. Marx, in reply, pointed out that one peculiarity connected with Graptolites was the extremely slow accumulation of the deposits which usually contained them, as might be inferred from the remarks of 732 ON THE STOCKDALE SHALES. previous speakers on their mode of swelling out laterally into normal deposits of great thickness. Hence, although the forms had un- doubtedly migrated from region to region, the time taken for migra- tion was so short, as compared with the time taken for the accumu- lation of an appreciable thickness of sediment, that the film formed during the time of migration might be practically neglected. He thanked the Society, on Prof. Nicholson’s behalf as well as his own, for the way in which the paper had been received. Quart .Journ.Geol. Soc. Vol. XLIV. Pl. XVI. Mintern Bros. imp. F.H. Michael del. et lth. FOSSILS OF THE STOCKDALE SHALES THE LAW THAT GOVERNS THE ACTION OF FLOWING STREAMS, 733 38. On the Law that governs the Action of Fiow1ne Streams. By R. D. OtpHam, Esq., A.R.S.M., F.G.8., Deputy Superintendent, Geological Survey of India. (Read January 11, 1888.) Or all the agents which Nature employs in her great and ceaseless work of change, of destruction and construction, of removal and renewal, probably none have been less studied, few are less under- stood, by geologists, than water in the form of streams and rivers. In a general way it is known that, with sufficient velocity, a stream will erode its bed, and that if the velocity be reduced sufficiently it will deposit part or all of what solid material it may be carrying down its course. But, while mathematicians and engineers have been investigating, in all their details, the laws which govern the flow of water, geologists have done little to investigate the laws under which it acts in shaping the surface of the world we live in. Rain, glaciers, and the sea; these seem almost to have limited the horizon of the geological view, and, without forgetting the researches of Prof. Hull, the essay of the late Mr. Greenwood, or the application of the principles enunciated by him to a special case by the late Mr. Fergusson, we may almost say that the intermediate link in the chain—the flowing stream—has either been regarded as unworthy of notice, or the vague general ideas and statements of the textbooks have been regarded as a complete and satisfactory account of the problem. Yet in the whole range of physical geology there is no subject which will better repay a detailed investigation or open a wider field of intricate and interesting problems than this: and it is with the hope of being able to contribute something to our knowledge of this almost unexplored region that this paper is laid before you. My attention was first drawn to this subject when at Hardwar in December 1883. In course of the operations for constructing new head-works to the Ganges Canal a small driblet of water began to eat into sand, over which it had flowed previous to the removal of a block of masonry. I noticed that only in certain parts of its course did it erode its channel and that there were intermediate reaches where there was no erosion, or, when it had assumed a nearly permanent condition, even deposition. The areas of no erosion, or deposition, gradually encroached upon the channels of erosion above them and were themselves encroached upon by the channels of erosion below. Acting on the hints obtained, I commenced an inductive investi- gation into what should be the action of a stream flowing over a uniform deposit, whether of its own formation or not. This, with my subsequent inquiries into the truth of the deductions arrived at, will be presented in the following pages. The fundamental principle on which all such investigations must be based is one of great simplicity, though its application leads to Q.J.G.8. No. 176. 3¢ 734 MR. R. D. OLDHAM ON THE LAW THAT GOVERNS conditions and combinations of no little complexity. Mr. Greenwood has explained how the tendency of a river to preserve a uniform velocity throughout its course leads to the parabolic section presented by the channel from source to mouth; but, owing to his haying overlooked the very different nature of the solid burden carried by the river in different parts of its course, his explanation lacks com- pleteness. As it seems to me, the law is not that the river tends to preserve or obtain a constant velocity, but that at any point of its course the velocity of current will tend to become such that the stream can just carry its solid burden. With regard to the appli- cation of this law, it is necessary to observe that it is the coarsest débris borne by the stream which will determine its velocity ; thus, in a stream carrying shingle, sand, and mud, the velocity will be controlled by the shingle, after that has been deposited, by the sand, and finally by the mud. But this must not be taken to mean that the current is directly governed by the nature of the burden cast upon the stream. Gra- dient and shape of channel are of course the two principal factors which govern the velocity of current, and in a subsidiary degree the © nature of the sides of the channel ; of these the two former frequently, the last generally, are to a greater or less degree the product of the stream itself, and by deposition or erosion they tend to become such that, when equilibrium has been established, the stream is just able to transport its solid burden. The law, as stated above, I hold to be obeyed by every stream throughout its length, though its action is often controlled and obscured by interfering causes, such as unequal hardness of the bed where the stream flows over rock. Where a stream enters on an alluvial plain, the law can be seen to prevail, and is moreover, on slight consideration, seen to be almost axiomatic in its nature ; for, suppose the velocity of current to be greater than that due to the law propounded, the immediate consequence would be erosion of the channel and transport of débris: when the stream reached the sea, if not sooner, the velocity would be checked and the transported débris would be deposited. In this way the lower end of the reach would be raised, the upper lowered, and the gradient diminished ; this, leaving out of consideration the effect of the shape of the channel, would result in a diminished velocity and equilibrium when the stream could just transport its solid burden. Similarly, if the velocity were less than that demanded, deposition would commence, and the gradient below the deposit would increase until the velocity of the stream reached the required limit. But it is not only by an alteration of gradients that the stream can adjust its velocity, for, with the same slope and sectional area of channel, the velocity varies with the square root of the hydraulic mean depth, or of the sectional area divided by the wetted perimeter. From this it follows that the gradient required to produce a given velocity will vary with the shape of the channel, being greater where this is broad and shallow, and less where it is narrow and deep. THE ACTION OF FLOWING STREAMS. ~ 735 Turning now to the application of these principles, let us take the case of a stream flowing in a restricted rocky channel and debouching on to a gently sloping plain whose gradient is too gentle to admit of the stream carrying on its burden of débris. This is consequently deposited as a “ fan” whose surface has a steeper slope than that of the plain and on which the stream is broken up into several broad and shallow channels, in which it has such a velocity as just suffices to transport its burden. In course of time, as the fan increases in size, some of these sepa- rate portions of the stream will reunite, and, by the mere fact of uniting, their velocity will be increased; since the same body of water flowing over the same gradient has a more rapid current when flowing in a single channel than when flowing in two separate | channels. But this increase of velocity will cause the stream to erode the surface of the fan over which it flows, and by forming a defined channel, to increase its hydraulic depth. The ves and consequently erosion will thus be still further increased. But this channel of erosion must at its lower end come out to the surface either of the fan or the plain, while its upper end is depressed below the surface of the fan ; its gradient is therefore less than that of the fan and consequently, in spite of the greater hydraulic mean depth, a limit will be reached where the velocity of current will again be only just sufficient to enable it to transport its burden of débris. Where this eroded channel passes out to the general surface of the ground, and its waters are no longer confined within a defined channel, the débris will be deposited in a second “fan.” I am aware that the word fan has never been used in this sense; but the form of deposit is essentially so similar to that of the fan, as ordinarily known, that [am loth to invent a new word, and prefer to define the lower region of deposition as a “‘ secondary fan.” At the base of the secondary fan an eroded channel will be formed, and at its lower end another fan, till we have a series of stretches in which the stream has alternately a higher gradient with shallow ill-defined channel and a Jesser gradient with deeper well-defined channel, the velocity in each case being such as will just enable the stream to transport its burden of débris. I shall define the former of these conditions as a “fan,” the latter as a ‘‘ reach.” Where a fan passes into a reach the gradient will be steeper than that of the fan, for the upper end of the reach has been excavated out of the latter; over this steeper gradient the stream will flow under the same conditions as over the surface of the fan, the velocity will be higher than on the fan, and erosion will take place. We may consequently expect that the reach will be constantly cutting back into the fan, and must consider whether there will not be an equal encroachment by the fan on the lower end of the reach. I have already explained that the fan below the reach will commence where the lesser gradient of the latter brings it out to the surface, and the waters are scattered abroad instead of being confined to a defined channel. But this spreading of the waters will 3c 2 736 MR. R. D. OLDHAM ON THE LAW THAT GOVERNS cause a sudden check in the velocity of the current, and a large portion of the débris will be deposited as a bar across the reach. This bar, both by the actual resistance it offers and by its influence in causing the waters to spread out at a point higher up stream than before, will continually increase by the deposit of débris on its up- stream side; the lower fan will consequently encroach on the reach above it, and we have the compensation required for the encroach- ment of the reach on the fan. These encroachments of fan on reach and reach on fan necessitate some modification of what has gone before. Both reach and fan have been regarded as regions of transport pure and simple, without either erosion or deposition, but it is evident that the gradual growth of the bar at the foot of the reach must react upwards and induce a certain amount of deposition in the reach, while the erosion at the foot of the fan must similarly react upwards and cause a certain amount of erosion on the surface of the fan. These considerations lead us to the following definition of the normal condition of equilibrium which a stream tends to assume :— that it will consist of alternate fans and reaches in which the stream is respectively split up into several shallow ill-defined channels, and collected into a single deep well-defined channel; that the former will be a region mainly of transport, but subsidiarily of erosion, while the latter will be a region, mainly of transport, but subsidiarily of deposition ; that fan will pass into reach by a short stretch of maximum gradient where erosion is at its maximum, and reach into fan by a short stretch of minimum gradient where deposition is at its maximum ; and that the sum total of erosion will equal that of deposition. Probably no stream is a purely transporting agent, but, unless the deposition or erosion are excessive, the above definition will apply with the exception of the last clause; there will be an excess of erosion or deposition according as the stream is on the whole eroding or depositing. The only actual levels, taken under circumstances that will test the above hypothesis, which are accessible to me are those taken in connexion with the Ganges Canal and recorded in the late Sir P. B. Cautley’s account of that work ; but before referring to them there are some general considerations bearing on the hypothesis. Since framing the definition given above I have travelled largely, to a great extent in country where the streams flow at the general level of the surface and where, owing to their drying up completely for half the year, the form of their channels can be very favourably studied ; and in every case where the stream does not flow in an excavated channel, but at the general surface-level of the alluvial deposits, wherever, in fact, there are no interfering influences, I have found that the stream-bed exhibits those features which it should according to my hypothesis. The stream-bed alternately spreads out into a broad ill-defined stretch of sand or gravel, and contracts into a narrow well-defined channel; moreover the broad stretches always rise up to the general surface, often the gravel atl oe THE ACTION OF FLOWING STREAMS, 737 spreads over it, while the narrow channels are distinctly depressed below the general surface. Taking the slope of the latter to repre- sent the average slope of the stream, this alternate elevation and depression of the stream-bed with reference to it accords perfectly with my hypothesis. Besides my own observations, I have studied the maps produced by the Survey of India, and find that wherever the circumstances are favourable this alternate expansion and contraction of the stream- bed is very noticeable; nor does it seem to be confined to small streams only, but may also be detected, though, as might be expected, obscurely, in such large rivers as the Ganges and the Jumna. Turning now to the Ganges-canal levels, if the maps in the Ganges-canal atlas are examined and the position of contour lines, drawn at a vertical distance of five feet apart on the Patthri and Rani Raos, be represented by dots, the crowding of these together where the channel broadens is palpable, but the original map does not indicate where the channel is well and where ill defined. Fortu- nately the text comes to our assistance and we are informed. that in the case of the Patthri Rao the canal crosses it where it had no defined channel; in the case of Rani Rao the canal was taken across a well-defined channel, but we are informed that 2000 feet below the canal this stream ceased to have a defined channel and was spread abroad over the country ; and it is evident at a glance that the gradient is there higher than where the channel is well defined, precisely as should be the case if my hypothesis were true. These two torrents are carried over the canal by “ superpassages,”’ that is bridges built so as to form a continuous channel for the torrents. In the case of the Patthri Rao the course of the stream was diverted, and it is consequently of no use for our present purpose. But for the Rani Rao, the superpassage was built so as to replace that part of the defined channel which was removed in excavating the canal. Within a few years of its completion, it is recorded that the region where the channel was. no longer well defined, instead of commencing 2000 feet below the superpassage, had extended right up to it, and presently sand began to accumulate on the bridge. This accumulation of sand for many years gave much trouble to the engineers in charge, but it has now ceased. Whether this is, as the engineers believe, altogether due to their works, or whether it is due to the defined channel below the fan having worked up to the bridge, or whether, as is most probable, it is due to a combination of the two, the records are not sufficient to deter- mine. Thus the surveys for and records of the Ganges Canal show the alternation of reach and fan, the greater gradient of the latter and the gradual progress of both up stream as demanded by the hypo- thesis formulated above. The small stretches of high and low gra- dient are not shown in these records, being probably of too small extent and too difficult to detect without special search, but they are indicated by the later records of the Patthri Rao. Here the stream, after crossing the superpassage, is artificially confined in a 738 MR. BR. D. OLDHAM ON THE LAW THAT GOVERNS channel of 150 feet broad, in which the slope of deposit is 14°5 feet per mile; but, where the stream is allowed to spread, the slope immediately falls to 3:04 feet per mile, and increases after 1 furlong to 20°3 feet per mile on the fan. From this it will be seen that the hypothesis above propounded leads to conclusions which are strongly supported by the surveys and levels of topographers and engineers, whose object was a mere delineation and record of observed facts without any consideration of their possible bearing on an unmooted hypothesis; and this agreement appears to be as strong a confirmation as could be desired. These considerations lead us to regard a flowing stream as another instance of the automatic adjustments of Nature by which cause is proportioned to effect, and the energy exerted to the work to be done. They moreover show that the ordinary text-book statement, that the size of the débris transported depends on the velocity of the current, is but a partial account of the case; that though the velocity of the current is directly due to the slope and shape of the channel, these are largely controlled by the nature of the burden cast on to the stream ; and that, where equilibrium has been established, where, to ~ borrow a phrase, the stream is in unison with its environment, the velocity of the current may be said to depend on the size of the débris it carries. It will be no answer to this to point out that the actual velocity of a stream is often in excess or defect of what the hypothesis demands; for, in such cases, the stream is either eroding or depositing, and the mere fact of erosion or deposition of itself proves that equi- librium has not been, but is being, attained. Where the velocity is too great, erosion tends to diminish the average gradient, and hence the velocity ; and if, owing to a defect of velocity, deposition takes place, the stream deposits its burden in such a manner as to increase the general gradient to the limit at which the velocity will be sufficient for the transport of its burden. These local exceptions cannot be held of importance in the face of the broad fact that on the whole it is in the upper reaches of a river, where the burden cast upon it consists of coarse débris, that high velocity is found, while in the lower reaches, where the burden consists of fine mud, a low velocity prevails. And this fact, even in the absence of the special considerations detailed above, might by itself be fairly held to show that the velocity of the stream is ulti- mately regulated by the work it has to do, and not its work by the velocity it possesses. Discusston. Mr. Drew hoped that Mr. Oldham would continue his observa- tions. The paper was difficult to discuss without being read, but Mr. Drew did not understand there being greater velocity on a “‘ fan,” the origin of which implied loss of velocity. Mr. Oldham used the word ‘‘fan” in a rather different sense from that in which it was originally proposed by the speaker. THE ACTION OF FLOWING STREAMS, 739 Rey. E. Hit was glad to hear a paper on physical geology. The two parts of the paper appeared to be separate. The dependence of the velocity of the stream upon the coarseness of its burden appeared to be a paradox, and perhaps was put forward as such. The alternation of “ fan” and “ canal,” or, as Mr. Oldham called it, “reach,” is well illustrated in the Alps, and must be produced whenever a succession of steps is traversed. Prof. Buaxr suggested that Mr. Oldham might mean that it depended on the coarseness or fineness of the material introduced into the stream, whether it was retarded or not in its lower reaches and so made to alter its velocity. Dr. Buawrorp said that he understood Mr. Oldham to express the view that the velocity of a stream was dependent upon the coarseness or fineness of the solid materials transported, a view in favour of which the speaker did not think Mr. Oldham had brought forward valid evidence. The observations on the alternation of “fans” and “reaches” were interesting, and alternations of a similar nature, of faster and slower areas, occurred in all parts of rivers. It was, however, unfortunate that Mr. Oldham’s critical illustrations were taken from localities where the course of the rivers had been affected by the Ganges canal-works. The Presipent regretted that Mr. Oldham’s paper was heard at a disadvantage, as the Author was not present to reply to the remarks made. 740 MR. F, RUTLEY ON PERLITIC FELSITES, 39. On Prrurtic Fensrrus, probably of Ancuman AGE, from the Franxs of the HererorpsHIRE Bracon; and on the possible OxteIn of some Errposires. By Franx Rurtzy, Esq., F.GS., Lecturer on Mineralogy in the Royal School of Mines. (Read June 20, 1888.) ; [Pirate XVII.] In a previous communication to this Society * a rock was described (No. 20) in which faint indications of a perlitic structure were dis- cernible. It occurred on the side of the Herefordshire Beacon, overlooking Castle-Morton Common, and a short distance in rear of the well-known cave. The specimens now under consideration were derived from the Rabbit Warren near the above-mentioned locality ; No. 1 from a point about thirty yards above the path, where it touches a small beck which runs between the higher portion of the Beacon and the - Warren ; while No. 2 was procured a little above and to the east of this spot, and about halfway up the steep bank of the Warren. The first is a rather deep greenish-grey to brownish-grey rock, which, on a smoothly-cut surface, shows a meshwork of very delicate veins, darker than the material of which the rock is mainly com- osed. 3 The second specimen is of paler colour, a yellowish-green or buff tint predominating. It was difficult at the time to procure better samples, and both of these must be regarded as in a considerably advanced stage of alte- ration. They were, however, kept;as they seemed to show faint indications of perlitic structure, and although, in sections cut from them, the structure is somewhat obscure, there is nevertheless sufficient proof that it is present. A section taken from specimen No. 1 appears by reflected light, under a low power, to consist of greenish-white to greyish-white matter, broken by small dark specks and curved lines, which un- mistakably denote perlitic structure, although this is, at first sight, somewhat difficult to recognize, owing to the extensive alteration which the rock has undergone. The section is seen to be traversed by a network of delicate fissures filled with quartz. From this it is evident that the rock has been subjected to great pressure and crushed into a mass of angular fragments, ranging from very small dimensions up to about a quarter of an inch in diameter ; but, beyond the actual gape of the veins, which seldom attain 4, inch in breadth, there has been no appreciable displacement of the frag- ments. * “On the Rocks of the Malvern Hills,” Quart. Joarn. Geol. Soe. vol. xliii. p. 499. AND ON THE ORIGIN OF SOME EPIDOSITES, 741 By transmitted light the decomposition-product appears to be chiefly epidote with possibly a little kaolin. The latter would naturally have resulted from the alteration of the felspathic portion of the felsite ; while the epidote seems, in great part, to have been formed within the minute fissures and perlitic cracks by which the rock is penetrated. Specks of hematite are also present. The prevailing greenish colour of the rock is due to the epidote, of which the largest crystals occur chiefly in the quartz-veins. The crystals are too small and, as a rule, too imperfectly developed for the measurement of the oblique extinction-angle in clinopinacoidal sections ; but in one case it was found to be about 28° to the edge 001: 010, or trace of the basal plane, the angle between the faces 001 and 100 in this instance being 113° to 114°. If the section were truly parallel to the clinopinacoid this angle should be 115° 24’, Sections in the orthodiagonal zone give parallel extinction. The close massing of the epidote renders the perlitic structure some- what obscure in transmitted light. The structure, however, appears more distinct when surface-illumination is resorted to; but, even in transmitted light and between crossed nicols, the most decomposed portions of the section may be seen to have a perlitic structure. Under these conditions of illumination this may be recognized by any one or more of the following characters :—1st, by the segregation of epidote along the perlitic cracks being denoted by the interference- colours ; 2ndly, by feeble translucence verging on opacity along the cracks due mainly to the close massing of very small grains of epidote ; ordly, by delicate rings or curved lines of felsitic or simply siliceous matter, the continuity of which is apparently broken by the ex- tinction in any given position of certain of the minute crystalline grains which constitute these delicate strings, so that an ever-shifting succession of bright points may be traced along the perlitic cracks during rotation of the section; and 4thly, by oval or irregularly- shaped nuclear residues of felsitic matter lying within the perlitic areas, and free, or comparatively free, from epidote. In section No. 2, from which the accompanying drawings (Pl. XVII.), were made, the decomposition-products are not so abundant as in No. 1. They are, however, present to a considerable extent and also consist mainly of epidote, which, by its segregation along irregular, wavy, and anastomosing lines, indicates that a banded structure may also have existed in the rock. The specimens do not disintegrate at all readily when scraped on a smoothly cut surface with the point of a penknife, and, indeed, there is more knife than rock abraded during the process. It does not therefore appear that kaolin is present in any appreciable quantity, if at all, or the rock would be less coherent. We may consequently assume that most, if not all, of the greenish-white matter in the rock is epidote. It is, however, probable that kaolin represented the first stage of decomposition of the felspathic consti- tuent of the felsite, and that the epidote has resulted from the alteration of this first decomposition-product by the action of water charged with bicarbonate of lime and more or less carbonate of iron 742 MR. F., RUTLEY ON PERLITIC FELSITES, in solution, substances readily taken up by water filtering through overlying rocks. If beneath the calculated percentage composition of kaolin we place an analysis of epidote, and subtract from the kaolin the amount of silica, alumina, and water present in the epidote, we see that the kaolin would require to have 31 per cent. of its constituents replaced by ferric oxide, lime, and magnesia. Si0,. Al,O,. Fe,0,. CaO. MgO. H,O. HRCEOEEEE Bsn oe css seeaim ciacris os 46-40 39°68 _... aa ... 13:92=100 i Ronmeisbas) | 8887 2113 1685 2358 O17 ... =10010 ee) Worn Rath $8907 2890 743 2480 010 0:63=100-48 That such a change may take place seems very probable, since water which has filtered through rocks moderately rich in lime and iron would suffice to bring about a conversion of this kind. It is difficult to say whether, in a felsitic rock, the conversion of the felspathic constituent into epidote would take place directly from the alteration of the felspar, or indirectly from it, by the alteration — of kaolin; but the alkalies present in the felspar would not be in- volved in the fabrication of epidote, and it seems highly probable that the conditions requisite to effect the alteration of felspars would entail the early removal of their alkalies and the consequent formation of kaolin. Such changes may occur in felsitic rocks, especially in those which, by reason of their perlitic structure, offer exceptional facilities for the percolation of water. As regards the blowpipe characters of the rocks which form the subject of this paper, thin splinters fuse on the edges to a white frothy glass in some spots and to a brown or greenish-black in others, the latter being evidently due to the fusion of parts more strongly charged with epidote. By ordinary transmitted light the epidote ranges from almost colourless to yellowish-green, and where the granules are closely massed together, the green colour is deeper, becoming brownish-green, and in such spots the section transmits very little light. Between crossed nicols some of the sections of the larger crystals show oblique extinction and the interference-colours are strong. The majority of the sections, however, give parallel extinction. The pleochroism is not strongly marked. In sections parallel to 100, b=nearly colourless, c=pale yellowish-green. That the two specimens here described show perlitic structure there can be no doubt; but, owing to the prevalence of epidote, it is rendered unusually obscure, and I have therefore given a more detailed description of the microscopic characters, in the hope that it may encourage search for this structure in felsitic rocks, even when alteration is far advanced. In the cases here given very slight additional change would have obliterated all traces of perlitic structure. It is possible that some epidosites result from alterations of this kind. AND ON THE ORIGIN OF SOME EPIDOSITES, 743 The mass in which these rocks occur forms a buttress, faulted against the eastern flank of the Herefordshire Beacon, and has been described as “ altered Primordial” by the late Dr. Harvey B. Holl. That they are of later Archean or Cambrian age is probable. With regard to another specimen derived from this mass *, which was described and figured in the paper which I last read before this Society, mention was made of numerous minute granules which were massed most closely along lines of perlitic fission in the rock, and as to the nature of which I expressed considerable doubt at the time. On re-examining the section and comparing it with those now described, I am inclined to regard these small granules as epidote. Dr. W. 8. Bayley, in a recent publication t, appears to have mis- interpreted my statement on this subject, indicating that I considered these granules to be topaz, whereas I “ very doubtfully ” referred a few isolatad crystals to the latter mineral. It is quite possible that these crystals are also epidote, as they give extinctions parallel and at right angles to the length of the prism, which would occur in orthodiagonal sections of epidote. From the foregoing observations it seems reasonable to think that felsites resulting from the devitrification of obsidian, quartz-felsites, aplite, arkose, and felspathic grits may, by the decomposition of the felspathic constituent, pass, in the first instance, into rocks composed essentially of quartz and kaolin, and that by subsequent alteration of the kaolin in the manner already indicated, they may eventually be converted into epidosite. This, however, I put forward as a suggestion, not asa conclusion. According to the relative percentages of quartz and felspar originally present in rocks, so, by alteration, they may eventually become more or less epidositic, and, in cases where the original percentage of quartz was low, a true epidote may result. The three sections now exhibited show three different grades of epidosition, although their original characters were probably identical. Concerning the origin of epidosite, Kalkowsky says :—“ One frequently meets with rocks consisting of epidote and quartz, which are generally termed epidosite; in many cases these are, however, nothing else than the last decomposition- and alteration-products of basic anogenic and katagenic rocks. There are probably also original epidote-rocks which belong to the quartzite family, and may be called epidote quartzites ” +. In the theory which I have here proposed it seems needless to demand that the rock should have been originally of a basic character, although I would in no way question the truth of Dr. Kalkowsky’s statement, for there may be more ways than one in which epidosites are formed. In the case of the felsites from the Herefordshire Beacon it is evident that the epidote was not an original constituent feo the Rocks of the Malvern Hills,’ Quart. Journ. Geol. Soc. vol. xliii. p. 499. Tt “Summary of Progress in Mineralogy and Petrography in 1887,” published from monthly notes in the ‘ American Naturalist,’ p. 1112. { ‘ Elemente der Lithologie,’ p. 272 (Heidelberg, 1886). 744 ON PERLITIC FELSITES, AND ON THE ORIGIN OF SOME EPIDOSITES. of the rock, since it has been chiefly developed along fissures and perlitic cracks, and the latter are known to have been formed during or subsequently to the solidification of the rocks which they traverse. It is also clear that in these instances the rock was originally vitreous, and unaltered vitreous rocks never contain epidote, sofar as I am aware, although it is by no means uncommon in their devitrified condition. EXPLANATION OF PLATH XVII. Fig. 1. Epidositic felsite (The Rabbit Warren, Herefordshire Beacon), showing perlitic structure, marked by the development of epidote along the perlitic cracks. X25 linear, ordinary transmitted light. 2. Another portion of the same section, x 120 linear, showing traces of perlitic structure. Discussion. The Presmpent wished to hear the opinion of chemists as to whether any solution acting on so inert a substance as kaolin could convert it into epidote. Mr. Teaxt congratulated the Author on having carried the history ~ of the vitreous rocks a stage further. He could confirm his obser- vations as to the frequency of epidote in perlitic rocks, and believed it had been largely developed during the alterations of the old vitreous rocks; but he would not venture to express an opinion on the process by which the epidote was formed. Mr. W. P. Braxe noted the frequent occurrence of epidote in the Triassic rocks of North America, where it is sometimes extensively interstratified with and formed in sandstones, as in the Sierra Nevada. Mr. Baverman commented on the way in which epidote was formed throughout the mass of the rock, and suggested the bearing of the matter of this paper on the question of the formation of such masses of epidote as that of Lake Superior, which may also have been formed, though on a large scale, in fissures. Epidote also occurs in the same way in Cyprus. Mr. Cote asked whether, seeing that even pyroxenes occur in many trachytes, it was not possible that the original rock contained sufficient lime to account for the formation of the epidote by secon- dary decomposition. He referred to the observations of M. Lévy on variolite of the Durance, where the perlitic cracks are marked out by crystalline granules. The AvurHor admitted the uncertainty connected with the precise mode of formation of epidote, and stated that, so far as he knew, epidote had never yet been produced artificially ; he was, however, puzzled to imagine the extensive percolation of water through the rocks without conversion of the felspar into kaolin. With regard to Mr. Cole’s question, he was inclined to think that the rocks were practically devitrified obsidians, and he did not think there was any evidence of the original existence of pyroxene in them, although it was abundant in other rocks in their immediate vicinity. Quart.Journ.Geol. Soc. Vol. XLIV. Pl. XVIL X 120. PH Michael Lith Mintern Bros - imp PERLITIC FELSITE (epiposrric) FROM THE HEREFORDSHIRE BEACON. ON A HORNBLENDE-BIOTITE ROCK FROM NEW ZEALAND. 745 40. On a Hornsienpe-BrotiteE Rock from Dusxy Sounp, New ZEALAND. By Captain F. W. Hurron, F.G.S. (Read May 23, 1888.) Tus rock was collected in Dusky Sound by Mr. W. Docherty, and given to the late Sir J. von Haast, who gave it to me. I do not know its field relations, but undoubtedly it is of eruptive origin and is associated with the Archzean gneisses and schists of that district. As I am not aware of any similar rock having been described, I think that some account of it may be interesting. The rock is compact, crystalline, of a dark green colour, weathering reddish brown, and the specific gravity varies between 3°00 and 3:07. With a lens it is seen to be composed of two minerals in nearly equal proportions. One is a black mica, the plates of which are sometimes collected into masses 0°1 to 0-2 inch in diameter, but generally scattered through the other mineral. Cleavage-flakes of this mica can be easily detached, and, under the polariscope, prove to be biotite, in which the two optic axes nearly coincide. When thin, these cleavage-lamine have a greenish tinge by transmitted light. Under the microscope, in thin sections of the rock, the biotite has the usual brown colour and strong dichroism. It often contains erystals of apatite, which is, I think, not usual. The other mineral, in thin sections, is of a pale bluish-green colour and dichroic, but not strongly so, passing from a pale brownish green to a pale bluish green, some portions being more strongly dichroic than others. With ordinary light very little structure is apparent, but with crossed nicols the general mass shows an aggre- gate polarization of rather coarse grains, almost a mosaic ; but here and there distinct crystals of considerable size can be recognized, without, however, retaining any of their crystalline faces. These crystals seldom show cleavage, and in the few cases where it is developed there is only one set of lines, the position of which I could not determine ; but certainly it does not lie in the orthopinacoid. Most of the crystals show twinning, often of a polysynthetic character, very similar to that so commonly seen in augite. A common case is for one side of a crystal to show a single twin, while the other side is polysynthetic. Ora band of twin lamine may occupy the centre of the crystal only. In a section taken nearly parallel to the brachypinacoid one set of lamine extinguished at an angle of 17° 30’ from the twinning plane, while the alternate set extinguished at an angle of 16° 45! on the other side of that plane. Another crystal, somewhat similarly cut, gave 12° and 16° as the two angles. This proves the crystals to belong to the monoclinic system and to be probably hornblende. J was fortunately enabled to test this determination further by finding a crystal in which the twins ex- tinguished simultaneously when the twinning plane was parallel to one of the diagonals of the polarizer. This proved that the crystal 746 ON A HORNBLENDE-BIOTITE ROCK FROM NEW ZEALAND. was cut parallel to the base. The crystal consisted of a single twin on one half, and several twin lamine on the other half, and the boundaries of the lamine were so sharp, although the section was not very thin, that it was evident they had been cut nearly at right angles, or, in other words, that the section was nearly parallel to the basal pinacoid. I therefore tried the simple half with con- vergent polarized light, and found a very distinct optic axis, with revolving band, on the circumference of the field, thus confirming the previous determination of the green crystals as hornblende. Some of these crystals show traces of schillerization in one direction, which I take to be a face of the prism. I saw no inclusions in them. There are no other essential constituents of the rock but hornblende and biotite. Occasionally an actinolitic structure is seen, but not commonly. ‘The mineral which shows aggregate polarization is either crushed hornblende or some altered form of it; itis identical in colour with, and shows the same dichroism as, the hornblende crystals. In one case I saw a small quantity of calcite in a crack. I suppose that this rock will come under Dana’s name of horn- blendite ; but I think it objectionable to take the name of a mineral and apply it to a rock, especially when that rock consists of two minerals in nearly equal proportions. There is in the Canterbury Museum a very similar-looking rock from Wet-Jacket Arm, Breaksea Sound; but I have not been able to examine it microscopically. Discussion. The PresrpEent remarked upon the rare occurrence of such rocks as the one described, and regretted that no specimen of the rock could be exhibited to the meeting. ON MARINE FOSSILS IN THE COAL-MEASURES OF FIFE, 747 41. On the OcovrRENCE of Marine Fosstis in the CoaL-MEASURES of Fire. By James W. Kirxsy, Esq. (Read June 20, 1888.) (Oommunicated by Prof. T, Rururt Jonus, F.R.S., F.G.S.) Tis paper records the discovery of fossils of good marine types in the Fifeshire Coal-measures. Reference is also made to the occur- rence of similar fossils in the same formation elsewhere. The Fifeshire Coal-measures* form a comparatively small field on the north shore of the Firth of Forth, where they abut on the coast- line from Dysart eastward to Largo. They extend only two or three miles inland where the field is widest. On the west they are bounded by outcropping beds equivalent to Millstone-Grit ; on the north by faulted strata of the Carboniferous-Limestone series. On the east and south they are bounded by the sea, beneath which they dip. Including an upper set of red beds (d” of the Geological Survey maps), there is a thickness of over 2000 feet of these measures ; but all the workable coals are in the lower portion (d’ of the Geological Survey maps) : see vertical section at p. 748. The prevailing fossils of this coal-field are those always charac- teristic of the formation in other districts. The flora is essentially the same as in the North of England. Among the animal fossils usually met with are Anthracosia acuta, Anthracomya modiolaris, Anthracoptera carinata, and other Lamellibranchs of this family. Spirorbis carbonarius is the common Annelid. The Ostracods consist of various species of Carbonia, with Beyrichia arcuata; with them also occurs the phyllopod Leaia Leidyi. Among the fish are Megalichthys Hibbertc, Strepsodus sauroides, Diplodus gibbosus, and well-known species of Ctenodus, Colacanthus, Rhizodopsis, Acanthodus, Paleoniscus, &. The Amphibians Loxomma Allmanni and Anthracosaurus Russelli are the highest forms of animal life represented. Of late years pits have been sunk further on the dip for the purpose of winning the deeper-lying coal of the field. One of these was put down to the Chemise Seam in 1884-5 by Messrs. Bowman & Co.t, of the Muiredge Collieries. This pit, which is now known as the Denbeath Colliery, is situated near the shore, between the villages of Methil and Buckhaven, in the parish of Wemyss. The sinking commenced in the upper red beds, which are well exposed on the shore adjoining. These beds were sunk through to the extent of nearly 70 fathoms, and then the underlying portion of the series was reached. A few fathoms in this lower division, and above a thin band of poor coal, a thick bed of dark shale was passed through, the material from it being tipped over the waste-heap along with the other excavated rock from the sinking. * The Upper Coal-measures were treated of in the Quart. Journ. Geol. Soc. vol. xxxvili. p. 245, &e. + Whom I have to thank for information very readily given. 748 MR. J. W. KIRKBY ON THE OCCURRENCE OF . Vertical Section of the Coal-measures in Fifeshire (300 feet at the top omitted.) (Scale 1 inch to 300 feet.) ..-Lhin Coals, or Black Bands and calcareous beds, near Methil. Upper Red=Beds, d3' of Geol. Survey ...... ...Marine-bed seen at Wemyss, &c. ...Hight-foot or Barncraig Coal. ...9ix-foot or Coxtool Coal. --Chemise or Main Coal. Lower Beds, with work- able Coals, d5 of Geol. SUPVCY). caisson / Parrot Coal. =| \ Wood Coal. ...Bowhouse Coal. ...Brankston Coal. | ...Dysart Coal. ...seven-foot Coal and Ironstone. MARINE FOSSILS IN THE COAL-MEASURES OF FIFE. 749 In this shale, a few months afterwards, I found the remains of a Lingula in great abundance. Further search led to the discovery of other Mollusca, two of which are easily determinable as Murchisonia striatula and Bellerophon Urei. Other specimens probably belong to Bellerophon decussatus : and imperfect examples of a Lamellibranch are not unlike a Sanguinolites. The Lingula differs in no way from Lower-Carboniferous examples of L. mytiloides, or from Permian examples of L. Crednert, which names Mr. Davidson has shown refer to one and the same species. On some planes of the shale it is very thickly strewed, in many cases with the valves together, in others as single valves or in fragments. The Murchisonia only occurred twice. One specimen shows from twelve to fourteen individuals within a few aquare inches of surface. These shells are well preserved. Several specimens of Bellerophon Urei were found, all more or less in bad condition. Along with the Mollusca are some scales, plates, and teeth of fishes, some of the scales resembling those of Rhizodopsis. Also stray patches of coprolitic matter, and very rarely there are fragments of plants. No Microzoa have been detected, though the shale has been carefully examined for Ostracods. The shale is black, brown, or rather purple, in colour. Part of the bed is laminated; but much of it splits irregularly with a curious roughly granulated surface. Here and there in it are flattish concretions or cakes of soft red ironstone, which contain good examples of the Lingula. The position of the bed is about 35 fathoms above the “ Eight- Foot Coal,” and thus considerably higher than all the workable coals of the series. As the measures lying above the “ Hight Foot” are exposed on the shore to the eastward of West Wemyss, I afterwards looked for this Lingula-bed there, and soon found it to the east of Wemyss Castle. It is here seen as a thick black shale, more or less laminated, and associated with a thin coal. Being a soft bed it is denuded to a lower level than the sandstones above and below it, and is thus covered by the tide before high water. The coal is the highest that is marked on the six-inch Geol. Survey Map (Sheet 32). The base of the upper red beds is seen a short distance to the dip; so that the stratigraphical position is about the same as at the first locality. The Lingule are here scarcely so numerous as at Denbeath Pit, though not at allrare. Bellerophon Urei occurs with them. Likewise the teeth (or dermal spines) of that common Coal-measure fish Diplodus gibbosus. A few other fish-teeth, some Paleoniscid scales, and coprolites (filled with scales), along with traces of plants are the other fossils found. Quite recently, in company with Mr. J. 8. Grant-Wilson, of the Geological Survey, I came upon another outcrop of this bed, in a little den or ravine at Kast Wemyss, about a mile to the east of the oy. G.S. No, 176. 3D 750 MR. J. W. KIRKBY ON THE OCCURRENCE OF last-described locality. This outcrop is seen in the den a short distance above the Parochial Office, and not far below the curling- pond. The coal is again present, resting on fireclay. The fossils are found in the shale above the coal. The upper group of beds (d”), in the form of red sandstone and shale, comes into section a few yards further down the den. Other marine fossils appear in the shale of this locality. The remains of a small Crinoid are common; and besides Lingula mytiloides there occur L. squamiformis, Discina nitida, Productus semireticulatus var. Martini, Discites rotifer, an Orthoceras, some Hybodont teeth, and other things. Perhaps the most characteristic form among the fossils at Hast Wemyss is the Discites identified with the D. rotifer described by Mr. Salter from a marine deposit near the top of the middle measures of the Lancashire coal-field (see p. 752). It is two inches or more in diameter, and has the same style of whorls, with sigmoidal ribs, as represented in that species. Discites rotifer, however, is evi- dently nearly akin to the D. falcatus of Sowerby, as pointed out by Mr. Salter, and it is possible that they may ultimately be found to be one and the same species. The Orthoceras always occurs flattened by pressure, and nothing like a perfect example has been found. So far as they go, the specimens, some of which are over seven inches long, seem nearest to O. attenuatum, Fleming. Some of the Hybodont teeth resemble those of Orodus, and are beautifully sculptured. Dr. Henry Woodward, who very kindly examined one of the specimens, informs me that they come near to the genus Mesodomodus as figured by Messrs. St. John and A. H. Worthen, from the Lower Carboniferous “ Kinderhook Beds” of Burlington, Iowa*. Others of the teeth belong to a species of Petalodus. From the three foregoing localities there have been obtained the following species :— Strepsodus sauroides?, 4g.,teeth and | Bellerophon decussatus, Flem. scales. Murchisonia (Aclisma) striatula, De Rhizodopsis ? sp., scales. Kon. Paleoniscid scales. Sanguinolites ? sp. Diplodus gibbosus, Ag. Productus semireticulatus, var. Mar- Mesodomodus, sp. Nov. tini, Sow. Petalodus, sp. Discina nitida, Phil/ips. Discites rotifer, Sa/t. Lingula mytiloides, Sow. sp., with longitudinal ribs. squamiformis. Phillips. sp., smooth. Crinoid stems= Actinocrinus ? sp. Orthoceras attenuatum ?, Flem. Plant remains, obscure. Bellerophon Urei, Flem. West of Scotland.—These are the only marine beds known in the Fifeshire Coal-measures. But in the West of Scotland marine fossils are recorded from different horizons of the formation: these * Geol. Surv. Illinois, 1875, vol. vi. p. 291, pl. v. figs. 18-22: = MARINE FOSSILS IN THE COAL-MEASURES OF FIFE. 751 it may be useful to mention, for the sake of including here all that is as yet known on the subject. In Lanarkshire the following species have been found by the Geo- logical Survey in the Slaty-band Ironstone (or in strata connected therewith) at the base of the Coal-measures* :—Conularia quadri- sulcata, Bellerophon Ure, B. decussatus, Lovonema or Murchisonia sp., Schizodus sp., Productus longispinus, Discina nitida, Lingula mytiloides, L. squamiformis, Serpulites carbonarius. Lingula squamiformis is also recorded by the same observers as occurring higher in the series, in the Airdrie or Quarter Blackband Ironstonet. The same authorities found Aviculopecten papyraceus and Posi- donomya, sp., still higher, in a shale some distance above the Ell Coal +. Probably from near the same horizon Mr. Dunlop has recently discovered, in the Airdrie Coal-field, Aviculopecten papyraceus and Orthoceras attenuatum, along with fish-remains, and the common Coal-measure Ostracod, Beyrichia arcuata §. Higher still, near the top of the Coal-measures (d’ of Geol. Surv., or workable portion), and thus probably at about the same horizon as the Fifeshire bed, Mr. Skipsey discovered, in 1865, the following marine fossils at the sinking of a pit at Drumpark, to the east of Glasgow ||:—Conularia quadrisulcata, Schizodus deltoideus, Pro- ductus scabriculus, Discina nitida, and the pentagonal stems of a crinoid. These fossils were imbedded in shale and ironstone nodules, the Productus being the most common. There are, thus, not less than four horizons at which marine fossils are found in the Coal-measures of the West of Scotland. England.—In England the occurrence of marine fossils in Coal- measures has been recorded from various districts. Among the earliest notices is that by Prof. John Phillips, who described the finding of Aviculopecten, Posidonomya, Gonratites, and Orthoceras in the roof of one of the Lower or Gannister coals near Leeds, Bradford, Halifax, and other places in Yorkshire]. Mr. E. W. Binney afterwards described similar marine bands in the Gannister coals of Lancashire, where they are found overlying several coal-seams of that series. Aviculopecten, Gonatites, Ortho- ceras, and other species are found in these beds **. It was pointed out by Mr. Binney that such fossils are seen at more than one horizon in Yorkshire, and that they are also met with in the same series of strata in Derbyshire, Staffordshire, Cheshire, and Flint ff. * Memoirs of Geol. Surv. Scotl., Explanation of Sheet 23, p. 23; Expl. Sheet 31, pp. 74, 75, 80. t bid., Explan Sheet 23, p. 91. t Lbid., Explan. Sheet 23, p. 92. § From information supplied by my friend Mr. John Young, of Glasgow. || Trans. Geol. Soc. Glasgow, 1865, vol. ii. p. 52. {| Manual of Geology, 1855, p. 183. ** Trans. Manchester Geol. Soc. 1860, vol. ii. pp. 72-83. tt Loe. cit. pp. 79, 83. OD 2 jal, MR. J. W. KIRKBY ON THE OCCURRENCE OF These Aviculopecten-bands of the Lower Coal-measures are described in the Memoirs of the Geological Survey for Lancashire, and the following is the list of fossils from them, after Mr. Salter :— Orthoceras, sp. Posidonomya Gibsoni, Brown. Discites, sp. leevigata, Brown. Goniatites Listeri, Martin. Monotis levis, Brown. paucilobus, Phill. ? (Gervillia) obtusa, Brown. Sp., near truncatus. Lingula mytiloides, Sow. Aviculopecten papyraceus, Goldf. Beyrichia arcuata, Bean. Another marine bed of the Lancashire Coal-field appears near the top of the Middle Coal-measures, the middle measures of Lan- cashire being the same as the Coal-measures proper of the North of England and Scotland (d’ of the Geol. Survey). Attention was first drawn to it by Prof. A. H. Green, who noticed its outcrop on the banks of the river Tame, at Ashton-under-Lyne, in 1864, and where I saw it in 1866 in company with my old friend Mr. Binney. The fossils occur in a thick stratum of grey shale; and they were considered by Mr. Salter to be wholly distinct, A, papyraceus excepted, from the species of the Lower Coal- measures and Carboniferous Limestone. Mr. Salter quoted the following species* .— Orthoceras, sp. Ctenodonta, sp. Discites rotifer, Salter. Aviculopecten papyraceus, Goldf, sp. -—— fibrillosus, Salt. sp. Serpulites, sp. Nautilus precox, Salt. Megalichthys Hibberti, Ag. Goniatites, sp. Calamites, sp. In 1860 (Quart. Journ. Geol. Soc. vol. xvi. p. 412) I gave a short account of the discovery of Lingula Credneri, Geinitz, a Permian species since shown by Mr. Davidson to be the same as L. mytiloides, in the Durham Coal-measures. The specimens were found during the sinking of the shafts at Ryhope Colliery, near Sunderland, in shale about 590 feet below the base of the Permian strata. All the workable coals were below this Lingula-bed, though twelve thin seams were passed through above it. The remains of Fishes, Anthracosie, and Ostracoda occurred in the same bed with or near the Lingula. In the “ Descriptive Programme of Excursions” for the Bir- mingham Meeting of the British Association, 1866, it is stated, at page 46, that three beds of black shale, containing marine fossils, were passed through at the Sandwell Park sinking (Hamstead Colliery), sixty-one yards above the Thick Coal of the South Staffordshire coal-field. Among these fossils are mentioned species of Lingula, Productus, Spirifera, Ortheous (Orthoceras?), and Euomphalus. Conclusion.—All these occurrences of marine fossils show that the Coal-measures, as a formation, contain many exceptions to their ordinary fauna and flora. If the amphibian and fish remains, the * Mem. Geol. Survey: Geol. of Country around Oldham, pp. 20, 64-66. MARINE FOSSILS IN THE COAL-MEASURES OF FIFE. Tae Mollusca, Cypride, and plants of the latter indicate freshwater conditions, it is evident that such conditions were occasionally overborne by inroads of the sea, bringing back species of shells and erinoids that had existed in the Carboniferous-Limestone ocean of an earlier period. This appears to have taken place in the areas of most coal-fields, and repeatedly in some. It is thus reasonable to assume that the open sea was not far off when the British Coal- measures were being formed, and that a slight increase in the rate of depression of the area sufficed to bring back the sea and marine life. There is undoubtedly something peculiar about the ordinary fauna of the Coal-measures, though the peculiarity is, perhaps, just as great, whether it is viewed as of freshwater or of marine origin. And though it cannot have been marine in the same sense as the fauna of the Carboniferous Limestone or any open-sea deposit, it can scarcely be understood on the view of its being of lacustrine origin, as some geologists still hold. Certainly these intercalated marine beds seem easier of explanation when the formation is looked upon as the deltaic or, in some way, marginal accumulations of a large land-area. Under such conditions everything observed in the paleontology of the strata can be accounted for, whether the indications be of dense vegetable growth, vegetable drift, or of freshwater, brackish- water, or open-sea animal life. Anyone who has studied the Carboniferous series of Fife strati- graphically, from the base of the Calciferous Sandstone* upward, will only see in these marine beds the last and final instances of what has come under his notice times out of number before, the coming in of marine deposits in succession to shales, sandstones, fire-clays, and coals containing plant remains or estuarine fossils. The whole formation indicates a long series of depressions with _ Intervening siltings up during periods of rest, the former often bringing in marine conditions, the latter as often resulting in an approach to land-surfaces and subterrestrial conditions. This is true of the Calciferous Sandstones, where there are more coals (only poor and thin) than in the Coal-measures proper, but where thin limestones and other marine strata are comparatively common. In the lower portion of the Carboniferous-Limestone series marine beds are thicker and the remains of marine life more abundant, though coals and plant-bearing beds come in among them. The same is the case, though less pronounced, in the upper portion of the Carboni- ferous Limestone; while between the upper and lower portions there is a thick group of carbonaceous strata containing as good workable coals, and as many of them, as exist in the true Coal- measures one thousand feet or so higher up. And so in the group of strata classed as Millstone Grit, marine beds alternate with others containing vegetable remains and poor coals. Then follow the Coal-measures with the second great series of thick coals, with here and there marine beds, without the least indications of unconformity or physical break. In fact there is no such break anywhere in the Carboniferous series of Fife. The whole succession is one of regular * Quart. Journ. Geol. Soc. vol, xxxvi. p. 559 &e. 704 ON MARINE FOSSILS IN THE COAL-MEASURES OF FIFE, order from the lowest beds seen at Anstruther to the highest at the mouth of the River Leven; and the lines of division used in their systematic arrangement are arbitrary, though convenient. ‘The Coal-measures of this county are thus part and parcel of the under- lying portion of the series, and they have evidently originated under much the same physical conditions as prevailed here during the whole of the Carboniferous period. I believe that the same regular sequence of Carboniferous strata obtains in other parts of Scotland, and it is the same in the North of England. In conclusion, it may be remarked that no marine deposits have been observed as yet in the upper red beds (d”) of the Coal- measures in Fife, or in other parts of Scotland. These latter beds contain the ordinary coal fossils, except that in Fife there haye been found on one horizon the remains of species of Hurypterus, some Limuloid Crustacea, and a cockroach. The next appearance of undoubted marine life in paleozoic strata is in the Lower-Permian Limestone of Durham and Northumberland, where two of the species* found at Wemyss, along with two or three other Carboni- ferous forms, are found among what is essentially a new fauna. These recurrent species, however, form a connecting-link between Carboniferous and Permian life; while, on the other hand, the fewness of the surviving species of the great Carboniferous-Lime- stone fauna shows how extensive and long-lasting must have been the physical changes that took place in the period intervening. * Lingula mytiloides and Discina nitida. ~1 or a ~t THE GREENSAND BED AT THE BASE OF THE THANET SAND, 42. The Gruunsanp Bev at the Basz of the Tuannr Sann. By Miss Marcarer I. Garpiner, Bathurst Student, Newnham College, Cambridge. (Read June 20, 1888.) (Communicated by J. J. H. Tuaut, Esq., M.A., F.G.S.) Tus bed may be seen at various points from Pegwell Bay in the east to Chislehurst in the west of Kent, and there is a bed at Sudbury, in the N.W. corner of Suffolk, which Mr. Whitaker considers to be the same*. At Lewisham and Croydon, to the west of Chislehurst, it is missing, and the light buff micaceous sand which usually succeeds it in West Kent rests directly on the flint bed above the chalk ; so that, unless either the 9 inches of greensand and tiint or the 2 feet of grey sand last seen in 1830 at Epsom by Prof. Prestwich are the same, the succeeding beds of the ‘lhanet Sand overlap it westwards. Specimens have been obtained from Pegwell Bay, Chislet near Herne Bay, Upnor, Chislehurst, and Sudbury. Leaving for the present che Sudbury sand out of consideration, this basement bed is a very fine sand formed of about equal quantities of dark and light grains mixed with more or less clayey matter. 1ts appearance in a section varies considerably with the weather, for it is the dark greenish grey of the darker grains which gives the colour when it is wet ; but when it is dry the clayey matter becomes a white powder, and is a much more conspicuous constituent. A microscopic in- spection shows the sand to consist of quartz, flint, glauconite, and small quantities of felspar and various rarer minerals, with a few casts of microscopic organisms. Quartz.cThe quartz is in not much rounded grains of average largest dimension about ‘1 millim. One of the striking points about the sand is the small proportion of quartz-grains, namely, only about 45 per cent. Glauconite.—The glauconite-grains are small as compared with those of most greensands. ‘he majority are of rounded outline, and consist of an aggregation of smaller grains, often wedge-shaped in form and fitted together in a convolute manner. The cracks between the parts of the grain are marked by a yellow line, probably of iron-oxide. ‘This kind of aggregate seems to be the commonest form of glauconite-grain, and occurs in those of the Cambridge Greensand, Lower Greensand (Folkestone), Upper Greensand (Highclere), and the basement bed of the Woolwich Sands. Other green grains are subangular. Some of these are only pieces of the round grains, but others are probably coated grains of flint or quartz, since some may be seen to give a distinct quartz-reaction. When mounted in balsam the glauconite is opaque except just at the edge, but in water or glycerine by * Geol. Surv. Mem. to Sheet 47. 756 MISS M. I. GARDINER ON THE GREENSAND BED transmitted light, and always by reflected light, it is a bright yellow green. That of some other sands, e.g. the Cambridge Greensand and the basement Woolwich beds, is a very blue green. Between crossed nicols it gives either no reaction or a speckled look, some- what like that of flint. The glauconite-percentage is only 15. Flint.—On first looking at a slide of this sand one is struck by the large number of very sharply angular chips. These may be roughly divided into two sets, the one transparent, the other almost or entirely opaque. The transparent ones have a rough pitted surface, which gives them a slightly greyish tint, and are often marked by small black dots, which, when present in any number, give the grains a darker colour. Between crossed nicols they have a minutely tesselated appearance, the lighter parts being of a bluish neutral tint. Their close resemblance to chips obtained by crushing a flint seemed to leave little doubt as to their nature; but, since the glauconite gives a somewhat similar reaction, it seemed possible that at least some of the more rounded grains, or those which gave a less distinct reaction, might be weathered glauconite. Asa test, glauconite grains were bleached by boiling in hydrochloric acid, and it was found that these could be distinguished from the flint by their different surface, clearer colour, and less distinct outline. The Upper Greensand (Highclere) was then examined for compari- son. Itis avery similarsand of quartz and glauconite. Though the glauconite-grains are in all respects like those of the Thanet Sand, yet there are no grains which could be mistaken for flint. There seems no reason why the glauconite-grains in the one should be supposed to have lost their colour by weathering when they have not done so in the other. Finally the sand was placed in a boro- tungstate solution of sp. gr. just below that of flint; although a few green grains fell through, all those floated out, with the exception of a very few grains of both quartz and flint which had probably adhered to the side of the funnel, were green. Therefore, unless the glauconite increased in sp. gr. by weathering, these grey grains cannot be glauconite. A consideration of this evidence seems to leave no doubt that these lighter grey grains are flint, although they form the abnormally large proportion of 20 per cent. The more opaque grains are in general form like the clear ones. In both, forms which resemble microscopic spear- and arrow-heads are not uncommon. There is a more or less distinct transition from the clear to the opaque, and some are opaque in parts and clear in others. By reflected light many show the same greyish colour as the clear grains, though many are almost black. In fact, by reflected light one often cannot tell whether a particular grain is transparent or opaque, though both are easily distinguished from the quartz- or the green glauconite-grains. Crushed fragments of the weathered white coating of a flint are very like some of the more opaque and transitional forms by transmitted light, though these differ by being white in reflected light. The slightly weathered surface of a black flint is such a mere film that it has not been found AT THE BASE OF THE THANET SAND, Tar possible to get pieces of it to compare; but some of these grains look by reflected light very like small, black flint pebbles, and the double thickness of weathered coating even, though thin, might be sufficient to make them opaque. In the boro-tungstate solution these opaque grains fall with the clear ones. Altogether there seems to be no reason for considering these grains to be glauconite, as their comparative opacity and the faint reaction which they sometimes give in parts between crossed nicols at first inclines one to do. The evidence there is seems to be in favour of the sup- position, suggested by their form, that these grains are also flint. Counting these in with the others, the flint-percentage rises to 40. This and the other percentages have been obtained by counting between 3000 and 4000 grains. The flint-grains are of about the same size as the quartz-grains, 7.¢. about 1 millim, in their longest dimension. It is these opaque grains quite as much as the glauconite which give the dark colour to the sand; for when the clay is washed out, what remains is dark grey, quite black when wet; but when the clay is washed out of the Upper Greensand, which is a sand very like this without the flint, the residue is of a light green colour. Besides these flint-grains, larger ones which might almost be called small pebbles, about ;4, inch in diameter, are often found, and at Pegwell Bay much larger flints, some slightly rounded like those just above the chalk, and others which are regular pebbles. Six were picked out of a piece of cliff about 2 feet square, but in most parts they were not quite so numerous. Twinned Felspar occurs in no great quantity. What there is is very generally twinned in two directions. Magnetite and Spinel.—Amongst the grains which come down in a boro-tungstate solution of sp. gr. 2°9 black opaque grains are the commonest. Amongst these some are very perfect octahedra. Only some seem to be magnetic, so that probably both magnetite and a dark spinel are present. Zircon also forms a large proportion of the heavier minerals. It occurs in very perfect crystals and in grains. The crystals differ considerably in size and form. Two from amongst the larger and smaller respectively measured ‘116 millim. x 036 millim. and "06 millim. x -02 millim. Often only the (100) and (10/) planes are developed, but sometimes also the (110) and (111) and other pyramid planes. Very frequently one pair of the (101) planes is developed at the expense of the other, so that the crystal has a truncated appearance. There are often needle-like inclusions parallel to some of the pyramid faces. Garnet (?).—In about the same quantity is present a mineral of which only broken fragments of fairly large size have been seen. It is very clear, colourless, highly refracting and isotropic. The fragments are often very sharply broken, and sometimes the fracture has a conchoidal look. Inclusions of black and green grains are not uncommon. Rutile is not present in such quantity as the minerals already 758 MISS M. I. GARDINER ON THE GREENSAND BED described, though there is always some in any slide of the heavier minerals separated from this sand. It is in long narrow prisms and grains. Tourmaline is present in about the same quantity. It is dark brown, purplish grey or very light and almost colourless. The light variety is in smal] and very perfect crystals, often as broad as they are long, so that they have the outline of a hexagon. They are terminated at both ends by the rhombohedron-planes, but the darker varieties are generally broken, or if not, the rhombohedral planes are only at one end, and the basal plane is developed at the other. Anatase has been looked for, but not found. The description so far applies to specimens from all the places mentioned except Sudbury, that is to say, since these places are distributed along the whole length of the southern outcrop, it may be taken as a general description of the basement sand of the Thanet Sands in the South of England from a mineralogical point of view. The following minerals occur in very small quantities, and so are not in any way characteristic. Garnet.—A few minute colourless dodecahedra have been noticed. One measured 02 millim. from one dodecahedron-face to the parallel one. One has grown round a smaller red crystal of the same form— a fact which seems to point to their being garnets. Actinolite.—A few fragments of a fibrous-looking green mineral strongly pleochroic, or yellow-green, with vibrations parallel to the length, and blue-green with those in the opposite direction are probably actinolite. Epidote—One somewhat rounded crystal of the outline of an oblique parallelogram with the corners rounded off, strongly pleochroic and with very distinct cleavages, has been referred for me by Mr. Davies to this mineral. Judging by the colour and pleochroism other grains may be of the same mineral. Chalcedony.—There are a few grains of a mineral polarizing in grey and having a spherulitic structure. Such grains are common in the residue of chalk dissolved in hydrochloric acid. Organe Remains.—A few microscopic organisms have been met with, and are sufficiently numerous to render it probable that with careful searching many genera might be found. ‘The commonest are siliceous, spherical bodies with a pitted surface, with a more or less distinct dark centre, apparently not casts. These may be either Radiolarians or Diatoms. Casts of Foraminifera, probably of the genera Planorbulina and Textularia in a clear, colourless mineral, perhaps chalcedony, have been noticed. The Greensand bed at Sudbury.—This bed has apparently been classified with the Thanet Sand on account of its position and colour. The great point of difference from the southern greensand already described is in the much larger glauconite-percentage, which gives the bed a greener, less grey colour. Glauconite constitutes about 75 per cent. of the grains, and the proportion by bulk is still greater, since the glauconite grains are larger and the other grains smaller AT THE BASE OF THE THANET SAND. 759 than those of the southern bed. Under these circumstances it is difficult to compare the flint-percentage. The flint forms about 10 per cent. of the quartz and flint grains, leaving the glauconite out of consideration. This,though much lower than in the south, is still high. The quantity of sand other than glauconite in the specimen brought away was so small that it did not seem worth while to try to make a separation ; but in slides of the sand left when the glauconite was washed off zircon, rutile, tourmaline, black mica, and fragments of the isotropic mineral described as garnet have been found. The points of resemblance to the southern basement-bed of the Thanet Sand are the facts that both are glauconitic, and contain a larger proportion of flint than is common, as well as frag- ments of a colourless garnet, which do not seem to be of such universal distribution as the other heavy minerals common to both. The basement Woolwich bed, though almost as largely glauconitic where it rests on the chalk in Hampshire, differs in several respects. Its glauconite is of a blue and not a yellow green; and though search has been made, no flint grains have been found. The statement has been made in the Survey Memoirs that there seems to be no proof of unconformity between the Chalk and the Tertiaries. Prof. Prestwich, in his new volume, assumes such an unconformity, since he says, ‘‘as the area of the Chalk-sea at the close of the Cretaceous period gradually became more and more restricted during emergence, so the early EKocene strata during the first period of the following submergence were of very limited extent ”*. Although a small flint-percentage might be due to an unconformity at a distance, so large a percentage could hardly have occurred in a sand formed far from the source of the flint; because the further the flint was carried, the greater would be the chance that, when deposited, it would be mixed with sand from other coasts. If such a sand could only be formed close to a chalk-shore, its existence at the base of the Tertiaries forms an additional piece of evidence in favour of the gradual extension of the early Tertiary sea described by Prof. Prestwich. One at once wonders how so large a flint-percentage could have been formed in early Tertiary times, whilst the sand now being formed along a very similarly situated shore contains little or no flint. ‘The difference may, perhaps, be due to a difference in the nature of the coast. Our coast consists of chalk-cliffs with the two long breaks of the Tertiary and the Wealden sands and clays. Is it not probable that currents drift the débris of these coasts as well as the material brought down by the Thames to mix with the débris of the chalk, and so bring down the flint percentage? If the early Thanet-sea stretched from the borders of Belgium as far north as Sudbury it would almost certainly have had something like 200 miles of unbroken chalk-cliff along its western shore, for the Tertiaries were not there, and even Prof. Prestwich, who seems to date the Wealden and Boulonnais anticlinal earlier than any one * ‘Geology: Chemical, Physical, and Stratigraphical,’ vol. ii. p. 337. 760 THE GREENSAND BED AT THE BASE OF THE THANET SAND. else, does not give any reason for thinking that the chalk was quite cut through in the middle of the Wealden area before the deposition of the Tertiary beds. If there were no strong currents to bring material from the other coasts, such a shore would be just the place for the accumulation of sand largely consisting of flint. It is true that the succeeding beds have a flint-percentage of about 5, and cannot have been formed in a sea with very different shores; but it is possible that they are really contemporaneous beds formed further out to sea, which crept westwards after the flint- sand, the flint-sand always being formed against the cliffs. Discussion. Dr. Hrype considered the paper important as showing the great amount of minute particles of flint present in these sands. It was a matter for regret that the Authoress could not be present when the paper was read. MR. E. WILSON ON THE DURHAM SALT-DISTRICT. 761 43. On the Duruam Satt-Disrrict. By E. Wiison, Esq., F.G.S. (Read June 6, 1888.) Tue new salt-field in the North of England occupies the low-lying country bordering the estuary of the Tees, situate partly in York- shire, partly in Durham, and bounded by the Magnesian Limestone district of Durham on the north, by the Jurassic hills of Cleveland on the south, and by the German Ocean on the east *. At the present time this salt-field has a proved or fairly indicated area of at least twelve square miles. Of this area, however, more than half lies beneath the sea, and is therefore inaccessible by the only system of working at present in operation in the district. Beyond these limits, however, the Durham salt-field has probably a wide extension. Kvidences of a limitation of the field in a northerly and also in a westerly direction have, indeed, been obtained; but what are its boundaries on the south and on the east we have not as yet, and perhaps never shall have, any means of determining. Discovery of the Rock-salt at Middlesborough and Origin and Progress of the Salt Industry in South Durham *. In the year 1859, Messrs Bolckow and Vaughan, the celebrated ironmasters of Middlesborough-on-Tees, being in want of water at their Middlesborough Ironworks, had a borehole, 18 inches in diameter, put down to a depth of 1200 feet ¢. Although large supplies of water were yielded by the more pervious strata passed through in this boring, this water was so highly charged with sulphate of lime as to be quite unfit for the purposes for which it was required. After passing through 70 feet of superficial deposits, which in this district consist of marine warp, river-alluvium, and Boulder-clay, and 1136 feet of red sandstone and red and blue marls with gypsum, a bed of rock-salt, 100 feet in thickness, was struck at 1206 feet from the surface, the boring leaving off (in August 1863) in rock described as “ limestone and conglomerate containing much salt ” at a total depth of 1313 feet 4 inches. The discovery of rock-salt in the Tees Valley was thus a fortuitous piece of good luck. It may be remarked that this was also the case in Cheshire and in Antrim ; but in those instances the discovery of the salt-beds was made in searching for coal. Shortly after its * See map, p. 762. t+ The discovery of rock-salt in the Tees Valley may be said to have been forecast so far back as 1816. In that year Mr. N. J. Winch, in his “ Observations on the Eastern part of Yorkshire,” read before the Geological Society, referring to the mineral springs of Dinsdale and Croft-on-Tees, said, “I have never heard that any brine spring had its source in this series of strata, though red sand- stone in which gypsum abounds seems a likely locality for rock-salt ” (Trans. Geol. Soe. vol. v. 1821, p. 543). { For details of this section see Mr. John Marley “ On the discovery of rock- salt in the New Red Sandstone at Middlesborough,” Rep. Brit. Assoc. 1863, Trans. of Sections, p. 82, and ‘ Geologist, 1863, p. 387. Map of the Durham Salt- District, 1888. Mavs -{ Scale Linch fo a mile ING ~ = 10°) Se) A IWS = ras A, Spree tent TES Nae ra it a re) las 3 +} IN zp ‘on HAVERTON HILL SALI O Beit Bro®\N27-; fi Ai O TENNANT & C28 erpthaece Spi) tie! Salfholme > ATE HEE SSS ~ SX F=f / BoRiNCNT SESS e2, Magnesian Limestone. £3. Red and white Sandstone, with Red Marl, Rock-salt, and Gypsum; f®. Red and green marls with Gypsum. gf. Black Shales (Rhetic). gl. Dark Shales and Limestones (Lower Lias). © Salt-wells and trial-borings. Alluyium. ->>| Blown sand. MR. E. WILSON ON THE DURHAM SALT-DISTRICT. 763 discovery at Middlesborough an attempt was made to sink a shaft in order to mine the rock-salt, but the influx of water was so con- siderable that the undertaking was for the time abandoned, and for nearly twelve years nothing further was heard about: Middlesborough salt *. In the year 1874 Messrs. Bell Bros. engaged the “ Diamond Rock Boring Company ” to put down an exploring hole fT, close to their ironworks at Port Clarence on the north bank of the Tees, about three quarters of a mile (1314 yards) nearly due north of the Middlesborough boring, and after nearly two years’ work, the bed of rock-salt, 65 feet in thickness, was reached at a depth of 1127 feet. In order to prove the character of the strata beneath the rock-salt, this borehole was continued for 150 feet below the thick bed of rock-salt, or to 1342 feet t from the surface, and at this depth strata were met with which were identified (erroneously, I believe, see p- 770) as the Magnesian Limestone of Durham §. Having proved the salt-bed, Messrs. Bell sank a well at the Clarence Ironworks, nearly a mile (1680 yards) due north of the place where it was first discovered at Middlesborough, and at this point found it at a depth of 1043 feet, having a thickness of 65 feet. Subsequently they put down a second hole about half a mile (830 yards) E.N.E. from their first well, and again found the salt-bed, rather thicker than before, at a depth of 1129 feet. Messrs. Bell Bros. were the first who succeeded in working the salt-bed in the Durham district, by a process which will be hereafter referred to. The success of this enterprising firm soon led other competitors into the field. Most of the subsequent explorations have proved the rock-salt to be present in good thickness; but in two or three * « On the Manufacture of Salt near Middlesbrough,” by Sir Lowthian Bell, Bart., F.R.S., M.Inst.C.E., ‘Proc. Inst. Civil Eugineers,’ vol. xc. 1886-87, part iv. p. 131 ef seq. t Loc. cit. See Appendix, p. 779, for details of this boring. t Two analyses of this limestone given by Sir Lowthian Bell, in his valuable paper already quoted, yielded the following results :— feet. feet. “ Depth from under-surface of the salt...... 154 193 Wambomatevom Limes. less, foves neaeesch cecaneesa’ 54°71 94:48 B TAAPTIOSEA) thieves se uedete o's dewkssc 41-18 2°98 “a REO: ya.si sensi amas SAGAN soe deco 0-81 0-78 EEE CRS eS ore eee SE Pe 2:00 1-20 PEERS Wath ca cok cs astne vote ueeaeh Seamasenidh eek enue 0:22 0°36 PUPS RELEE! 50, ck. Sots. os neat ok aontane cetonaeepomang les! 1:08 0°20 100-00 100-00 ” There are some slight discrepancies here. In the sections to Sir L. Bell’s paper (pl. 3. fig. 3) the total depth of the boring is given as 1355 feet, and the beds of ‘‘ limestone and much gas” and “grey limestone and gypsum” described in that section, and from which the above analyses appear to have been taken, lie at depths of from 56 to 133 below the wnder surface of the rock-salt, and therefore could not have come from depths of 154 and 193 feet below that bed. Probably ‘‘ depth from upper surface of the salt”’ is here meant. § Loe. cit. p. 133. 764 MR. E. WILSON ON THE DURHAM SALT-DISTRICT,. notable cases it was either very poorly developed or entirely wanting. The Newcastle Chemical Works Company put down two boreholes on the north bank of the Tees, opposite Middlesborough and about 1400 yards W.N.W. of Messrs. Bolckow, Vaughan and Co.’s Middles- borough well. Although the sinking at this point was carried to a depth of 1260 feet, including upwards of 200 feet of Magnesian Limestone underlying the New Red Sandstone, not a trace of the rock-salt was found*. Again at a boring which was made at Stone Marsh, Haverton Hill, on the Tees, one mile W.N.W. of the last-mentioned exploration, to a depth of 1000 feet, including about 180 feet of Magnesian Limestone, a bed of rock-salt only 9 feet in thickness was found near the base of the New Red Sandstone. About three quarters of a mile (1300 yards) north of the New- castle Chemical Co.’s unsuccessful sinking, the Haverton Hill Com- pany have sunk several wells, and here the rock-salt was met with in full development (93 to 123 feet) at a depth of about 900 feet. The Newcastle Chemical Company having secured a district on the ‘TTees-mouth shore, north of the area leased to Messrs. Bell, and 1235 yards nearly due north of the No. 2 well | of that firm, sank seven wells within a limited area, and in all of these found the salt-bed in full thickness (90 to 117 feet) at a depth of 1100 feet. A company, promoted by Mr. Casebourne of Hartlepool, has put down a hole on property belonging to the Greatham Hospital, at a point two miles a little west of north of the last-mentioned wells, and found the salt 82 feet thick at a depth of 889 feet. This is the most northerly point at which the salt-bed has yet been proved. Last year the same firm (Messrs. Casebourne and Bird) commenced a boring f for salt at Seaton Carew, two miles N.N.E. of their Greatham well, and about the same distance south of Hartlepool. The New Red Sandstone was penetrated to a depth of 522 feet, without any traces of rock-salt being found. The Magnesian Limestone was then entered, and at the time of writing had been proved to a depth of 838 feet, or 1360 feet from the surface, without being passed through. So long ago as the year 1827 a boring was put down to a depth of 529 feet at Oughton, 14 mile west of Seaton Carew. The greater portion, if not the whole, of this boring was in Triassic sandstones and marls, but no salt-beds were met with. In 1887 Messrs. Case- bourne and Co. put down a boring at the Cement Works near West Hartlepool, half a mile N.W. of the Seaton Carew boring, to a depth of 770 feet. The upper 715 feet of this section consisted of New Red Sandstone (Keuper Waterstones), the lower 55 feet of Magne- sian Limestone. No rock-salt was found here either, but consider- able deposits of anhydrite occurred at the base of the Trias ¢. * See Appendix, p. 779, for details of this section. + See Appendix, p. 781, for details of this section. + The presence of from 500 to 700 feet or so of Triassic strata near Seaton Carew, within a mile of the probable boundary of the Magnesian Limestone, would seem to indicate the existence of a fault, with a downthrow on the south, between this place and West Hartlepool. MR. E, WILSON ON THE DURHAM SALT-DISTRICT, 765 It is intended to carry the Seaton Carew boring to a total depth of 2000 feet, in order to determine whether or not productive measures of the Durham Coal-field extend beneath the Permian and Triassic rocks in this direction. Whatever be the result, this trial-boring will always be one of very great geological interest, not only from the light it will throw upon this important question, but also from its furnishing us for the first time, in one complete vertical section, with the entire series of the Magnesian Limestone of Durham *., Further successful explorations for rock-salt have also been recently conducted south of the estuary of the Tees. The Middles- borough Estate Co., Limited, have proved the salt-bed 90 feet in thick- ness at a depthof 1341 feet from the surface at North Ormesby, three quarters of a mile (1200 yards) due south of Messrs. Bolekow and Co.’s Middlesborough boring. The Cleveland Salt Company (for- merly Messrs. Bolckow and Vaughan) have sunk a well on the Tees foreshore, near the Eston Ironworks, about 23 miles east of their Middlesborough well, and found the salt-bed 81 feet in thickness at a depth of 1570 feet from the surfacey. The salt-bed (86 feet) has also been proved at the Imperial Ironworks, half a mile nearer Middlesborough, at about the same depth. In the year 1887 there were, according to Sir Lowthian Bell, no less than twenty wells in the Durham district from which salt in the form of brine had been raised, although seven of these were then disabled through accident. The annual production of salt from these wells in that year has been estimated at 150,000 tons, and for the present year at 200,000 tons or thereabouts. Seeing that the demand for this substance at the soda-works of the neighbouring district is at the present time very considerably in excess of this amount, there can be very little doubt that, the natural supplies being ample, the above output is capable of very considerable expansion in the future. Stratigraphical Position of the Saliferous Rocks of the Durham district. As in other cases where our knowledge of the stratigraphy of a district mainly depends upon the evidence afforded by deep borings, the determination of the geological age of the saliferous rocks of the Durham district is by no means free from difficulty. We must not therefore be surprised to find that very diverse and conflicting opinions have already been expressed, and that at the present time a good deal of confusion exists on the subject. I propose in the first place to briefly review these opinions, and afterwards to con- sider in a little more detail the particular view which I believe to be the correct one. In a paper read before the British Association in 1863, Mr. John Marley described the discovery of rock-salt at Middlesborough by * Since this paper was read the boring at Seaton Carew has been continued and is still proceeding. The Magnesian Limestone has been proved to haye a total thickness of 878 feet at this point. At a depth of 1400 feet from the surface Carboniferous rocks were entered, and on Sept. 29th, 1888, had been proved to a depth of 400 feet, or a total depth of 1800 feet fi om the surface, These rocks consist of grey and red sandstones with dark bituminous shales with two thin coal-seams, and evidently belong to the Coal-measures of Durham ; but, so far, no workable coal has been reached. t See Appendix, pe eto: O23-G. 8. No..176. 3E 766 MR. E. WILSON ON THE DURHAM SALT-DISTRICT. Messrs. Bolckow and Co., and gave a detailed section of that boring, and the analysis of the salt here quoted *. The author refers “ the strata in which the salt occurs to the Upper New Red Sandstone, or the same as those in which the rock-salt of Cheshire occurs.” In a paper “On the parts of England and Wales in which Coal may and may not be looked for beyond the known Coalfields,” read before the British Association in 1866+, Sir Roderick Murchison referred to the (then) recent discovery at Middlesborongh, “ by the spirited ironmaster Mr. Vaughan, of a body of rock-salt subordinate to the New Red Sandstone at a depth of 1800 + feet without reaching even the surface of the Magnesian Limestone.” In the Presidential Address to the British Association in the year 1880, Sir Andrew C. Ramsay, LL.D., F.R.S., referring to the earlier salt-explorations of Messrs. Bolckow and Messrs. Bell, said (p. 11), ‘‘in the North of England at and near Middlesb’rough, two deep boreholes were made some years ago in the hope of reaching the coal-measures of the Durham Coalfield§, One of them, at Saltholme, was sunk toa depth of 1355 feet. First they passed through 74 feet of superficial clay and gravel, and next through about 1175 feet of red sandstones and marls with beds of rock-salt and gypsum. The whole of these strata (except- ing the clay and gravel) evidently belong to the Keuper marls and sandstones of the upper part of our New Red Series. Beneath these they passed through 67 feet of dolomitic limestone, which in this neigh- bourhood forms the upper part of the Permian series, and beneath the limestone the strata consist of 27 feet of gypsum and rock-salt and marls, one of the beds of rock-salt having a thickness of 14 feet. This bed of Permian Salt is of some importance, since I have been convinced for long that the British Permian strata were deposited, not in the sea, but in salt lakes comparable in some respects with the great salt lake of Utah, and in its restricted fauna to the far greater salt lake of the Caspian Sea” ||. In the geological article by Messrs. W. Y. Veitch and G. Barrow, F.G.S., appended to the ‘ Guide to Middlesborough and the District,’ for the use of Members of the British Association visiting Cleveland, Sept. 8th, 1881, the authors give three detailed sections of the salt- measures of the district, viz., Messrs. Bolekow, Vaughan & Co.’s Middlesborough well, and Messrs. Bell Brothers’ Saltholme Test- boring and No. 1 well, and speak of the salt-deposits as occurring in the New Red Sandstone. In the Sixth Report of the Committee of the British Association “On the Circulation of Underground Waters in the Permeable For- mations of England and Wales” 4, Mr. C. E. de Rance, F.GS., * Rep. Brit. Assoc. 1863, Trans. of Sections, p. 82. ‘Geologist,’ 1863, p. 387. Appendix, infra, p. 782. Tt Rep. Brit. Assoc. 1867, Trans. of Sections, p. 61. ¢ An error for “from 1200 to 1300 feet.” § This was not exactly the case ; the first boring was sunk for water, the second for salt, and to test the strata below the salt-bed, rather than with the hope of actually reaching coal. See Bell, doc. cit. p. 133. || Rep. Brit. Assoc. 1880, p. 11. The italics in this and the following quota- tions are mine. {| Rep. Brit. Assoc. 188U, p. i104. See also Seventh Report of the same Committee, Rep. Brit. Assoc, 1881, p. 310, MR, E. WILSON ON THE DURHAM SALT-DISTRICT, 767 referring to the Middlesborough boring, says, ‘‘ The limestones, thick salt-beds, and gypsum in that boring, are probably referable to the Permian ; the intervening beds of red sandstone, 673 feet, are probably referable to the Waterstones and Lower Mottled Bunter, the Upper Mottled and Pebble-beds having thinned out.” But in the Eleventh Report * of the same Committee we find that this author modifies his opinion as to the strata met with in the Middlesborough and Saltholme borings to the extent that he considered it “‘ more probable that the pebbly character of the middle portion of the Bunter has died away northwards, and that the Middlesborough section represents Waterstones, pebbleless Middle Bunter and Lower Bunter.” In a paper read before the Geological Section of tie British Asso- ciation in 1886, on “The Stratigraphical Position of the Salt Measures of South Durham ”’ +, Professor G. A. Lebour, M.A., F.G.S., gives reasons for suggesting “that much of the Salt-measures of the South Durham district is probably the representative of the Upper or Rauchwacke Permian of Germany.” The following table shows the classification Professor Lebour tentatively suggests for the strata met with in the Durham district, with an alternative arrangement of the strata which I would myself advocate. Classification of the Permian and Triassic Rocks of the Durham district, according to Permian LEsBour. Tue Avutuor. Avicula-contorta beds (proved in Hston shaft and boring) ............ Rheetic. Rheetic. 7. Red and green marls with gypsum oa ) (known only South of Tees)..... ... Upper | re = Trias. \ Bribe BATIGSEONG «.........cce.-ccscenscnsss Unconformity (?). | Upper gi Trias, 5. Red sandstones and marls .........068 (2? Lower) Trias.|| 3 f _ viz. \ Upper Unconformity (?). = Keuper. 4, Red marly sandstones, marls with U = lenticular beds of anhydrite, gyp- rca sum, and salt, and fcetid limestone (Rauchwacke) in variable bands towards the base. ) ’ Unconformity. 3. Main Magnesian Limestone............ Middle 2. Marl-slate, with fish-bed ............... Permian. \ Permian ; (Upper f). MepPellow Sands <....:....0.cceccssccoececs Lower Permian.| ) Unconformity. Unconformity. Carboniferous rocks ...........sceeseseeeees Carboniferous. * Rep. Brit. Assoc. 1885, p. 384. + Rep. Brit. Assoc. 1886, Trans. of Sections, p. 673. { That is to say, Upper or Zechstein &c. division, as contrasted broadly with the Lower or Rothliegende group. 3&2 768 MR. E. WILSON ON THE DURHAM SALT-DISTRICT. The above classification of Professor Lebour’s has been criticized by Professor Green, in ‘ Nature’ *, on general grounds regarding the impracticability of making precise correlations of the minor divisions of a formation in dissociated areas, especially in the case of “a group of rocks like the Permian, formed in so many distinct basins and under changing conditions, the order and nature of which were probably never the same in any two basins.” With the general tendency of these objections I coincide. To arrive at correct con- clusions regarding the classification of the Permian (and the Triassic) rocks of the Durham district, we must compare these rocks with those of the same series in other portions of the same great North-eastern area or basin, with which they are in direct physical continuity, and of which they form apart. All attempts to correlate the Per- mian rocks of Cumberland and Lancashire with those of Durham, Yorkshire, &c., are, 1 believe, doomed to failure, because these two areas were physically disconnected in Permian times, and on that account the sequence of the possibly synchronous deposits in them is entirely different 7. Still more hazardous would it be to attempt to correlate in minute detail, especially in the absence of any strongly confirmatory palzontological evidence, the minor divisions of the Magnesian Limestone of Durham with the rocks of the same series in the equally disconnected and far more distant conti- nental areas. But that it is possible to compare the Permian (and the Trias) of Durham, in their subdivisions, with the same rock- series in other parts of the North-eastern basin I cannot doubt; and it would be a lame conclusion, I consider, to fall back on some general term, such as “ Poikilitic” or ‘‘ New Red Sandstone,” for the united Permian and Trias of Durham, because the characters and succession of those rocks in that district are not precisely identical with what we find them to be further to the south. Sir Lowthian Bell, in his essay ‘‘ On the Manufacture of Salt near Middlesborough,” does not himself consider the question of the geological age of the saliferous rocks of the district; but in the discussion which followed the reading of his paper several diverse opinions on this head were expressed by some eminent authorities, Sir W. W. Smyth said, ‘It had been already shown pretty clearly that the formation in which the salt was found’ was of a different period, and of a different quality to that of the Cheshire salt-beds.” On the other hand, Professor Hull wrote that ‘‘ The salt-rock under Middlesbrough seemed to occupy the exact geological position of that in Cheshire, Staffordshire, Warwickshire, and at Carrickfergus, near Belfast, being at the base of the New Red Marl (Kenper division of the Trias), and above the New Red Sandstone (Bunter) ; ” whilst Mr. Bauerman observed that the subject of the paper was ‘very interesting, but, like many other interesting subjects, obscure.” The Geological Survey of England class the saliferous beds of South Durham with the lower or ‘‘ Waterstones ” section (/°) of * « Nature,’ vol. xxxvi. 1887, p. 289. t ‘‘The Age of the Pennine Chain,” Rep. Brit. — 1879, p. 343, and Geol. Mag. 1879, p. 500, ‘ic MR. E, WILSON ON THE DURHAM SALT-DISTRICT, 769 the Upper Keuper division of the Triassic series. Upon the re- cently published maps the rocks of this lower subdivision (Water- stones) are shown as occupying the larger portion of the low-lying country intervening between the Jurassic uplands of the Cleveland district and the Magnesian Limestone region north of the Tees, without the intervention of any Bunter Sandstone. The limits of the Permian and Triassic areas could not, however, be defined with precision, owing to the thick cloak of superticial deposits, which renders the study of the solid geology of this district so difficult ; thus the boundary between the two had to be indicated by formal lines, and it is stated on the maps as approximate only. From the foregoing references, then, it appears that there are three distinct views at present prevailing with regard to the geological age of the saliferous deposits of the Durham district. First, there is the view, originally expressed, I believe, by Sir Andrew Ramsay, that the principal bed of rock-salt belongs to the Keuper, and that the lower beds of rock-salt, marl, limestone, and gypsum belong to the upper portion of the Permian series. ‘This is the view which Mr, Horace Woodward, F.G.S8., adopts in the new edition of that work so valuable to all students of British Geology, ‘ The Geology of England and Wales’*. Then we have what I should call the more extreme view of Professor Lebour and Mr. C. E. De Rance, that all the salt- beds and associated strata, “‘ Red marly sandstones” &c. (No. 4 in Prof. Lebour’s classification), belong to the Permian formation, and that the overlying series of Red Sandstone and marls (No. 5) represent the Lower Trias or Bunter Sandstone. Lastly, there is the view that all the salt-beds and the whole of the saliferous marls, sandstones, and limestones met with in the lower part of the various borings in this salt-field + above the continuous strata of the Magne- sian Limestone, as well as all the overlying red rocks of the Tees- valley district, belong to the Trias, and to the Upper or Keuper division thereof—to the same general series, in fact, as that which contains beds of rock-salt in Cheshire, Worcestershire, and the north of Ireland. This last is the view which the earlier geologists, judging by the limited evidence then available, took of the matter, and is the one which has always appeared the most probable to myselft. In addition to the authority of the Geological Survey, which, as the result of careful and detailed investigation on the spot by highly qualified men, must always carry very great weight, I think I am justified in quoting this as the opinion of Professor Hull; for in the correspondence relating to Sir L. Bell’s paper §, the able author of the “‘ Trias and Permian Rocks of the Midland Counties” refers the salt-rock under Middlesborough to the base of the Keuper Red Marls, and says nothing about ‘ Permian Salt.’ It is only fair, however, to say that Prof. Hull refers solely to the Middlesborough * «The Geology of England and Wales,’ 2nd ed. 1887, pp. 221, 241. t See p. 772 and Sections facing p. 782. ¢t “The Permian Formation in the North-east of England,” ‘ Midland Naturalist,’ vol. iv. 1881, p. 188. § Loe. cit. p. 154. 770 MR. E. WILSON ON THE DURHAM SALT-DISTRICT. section, and makes no mention of Messrs. Bell’s trial-boring, 2. e. the particular section upon which the hypothesis of Permian salt in Durham was first based. We must also interpret in a liberal sense the words “ the exact geological position” used by Prof. Hull. It wouid not be correct to assume that the salt-beds of South Durham, of Cheshire, Worcestershire, and the North of Ireland lie at exactly the same horizon in the Triassic (Keuper) series, or that they were strictly synchronous deposits. As a matter of fact, the beds of rock-salt in Durham lie near the base of the Upper Keuper (f’) and 1700 feet below the topmost Trias (or we will say the Rheetics, to fix the horizon still more definitely), whereas in Cheshire the salt-beds come high up in the Keuper Marls (f°), whilst in Worcestershire and in Antrim they probably occupy inter- mediate positions. I will now state the grounds upon which I conclude that the saliferous rocks of the Tees valley belong, neither wholly to the Permian formation, nor partly to the Permian and partly to the Trias, but wholly and solely to the Triassic series. In the year 1881 I made a careful examination of the cores of the rocks passed through in Messrs. Bell Brothers’ Saltholme trial-boring, including the 150 feet or so of strata beneath the thick bed of rock-salt at that point. From this inspection I satisfied myself that the rock-salt belonged to the Keuper division of the Trias. The thick series of regularly bedded and fine-grained red and grey sandstones and marls which, in this and the other sections here referred to (see Appendix and Sections facing p. 782), overlie and graduate down into the saliferous marls, and which underlie and appear to graduate up into the gyp- siferous red marls, show the closest resemblances in their general structure and mineral characters to the Keuper “ Waterstones ” of the Midland counties. The development in this district of some 300 or 400 feet of red marls with beds of gypsum and rock-salt, having very much the character of the Upper Keuper ‘“ Red Marls,” beneath a considerable series of red sandstones possessing the characters of the ‘* Water- stones,” does not, in my opinion, militate against the conclusion that all these rocks belong to the Keuper series, but, on the other hand, tends to bear out the view, which we have independent reasons for adopting, that the ‘“‘ Red Marls ” and the “* Waterstones ” can only be arbitrarily separated from each other, that they really form portions of the same rock series, and that the same peculiar physical conditions were maintained during their deposition. The lowest beds met with in the Saltholme boring beneath the thick bed of rock-salt (154 feet proved), and described by Sir Lowthian Bell as ‘ Limestone and marls with gypsum and rock-salt,’ also appear to me to belong to the Keuper division of the Triassic series. The cores of these beds which I now exhibit, and which were kindly given me by Messrs. Bell on visiting their works at Port Clarence, appeared to be fair samples of the 67 feet or so of strata met with near the bottom of their trial-boring, and described in the sections as “ Limestone” or “ Magnesian Limestone.” I should MR, E. WILSON ON THE DORHAM SALT-DISTRICT, TTL demur to the use of the term “‘ Limestone” as applied to the whole of these beds, and would designate them instead ‘indurated marls.” Although there appear to be dolomitic or calcareous, as well as dark bituminous beds among them, they show no sort of resemblance to any known beds of the Magnesian Limestone of Durham; on the other hand, they possess the characteristic greenish-grey colour of certain Keuper Marls, as well as a very similar texture and probably also mineral composition, although decidedly harder than most of the rocks of that series. It is also worthy of note that they contain gypsum, as well as that they overlie a thickish seam of rock-salt. It was upon the supposed identification of these ‘limestones’ as belonging to the Magnesian Limestone that Ramsay based his hypothesis of Permian salt in Durham. Whilst not prepared to accept the evidence of rock-salt in the Permian formation in Eng- land, I do not on abstract grounds contest the possibility of such an occurrence. With the hypothesis of direct chemical precipitation in inland salt lakes (or lagoons) of the dolomitic deposits of the British Permians I entirely concur, and elsewhere I have advanced arguments in support of this theory *. Although the idea of ‘ Perm- ian salt’ in Britain must, I believe, be abandoned, it is worthy cf note that in certain of the deep borings in the Durham salt-field (see Appendix, pp. 779, 781), gypsum and anhydrite are found to occur in intimate association with the dolomites of the Magnesian Limestone ; and in the Seaton Carew section these minerals are distributed, more or less abundantly, through the greater portion of that series. Surely this is a very significant fact and one that must tell strongly in fayour of the chemical-precipitation hypothesis. Accepting the accuracy of the information as to the presence in the Saltholme section of dolomitic limestones above certain saliferous strata, it would not be safe to assume, failing more decisive evidence on the subject, that such beds belong to the Permian formation. Calcareous beds are met with in rocks of undoubted Triassic age exposed at the surface in South Durham, and dolomitic rocks are known to occur to a considerable extent in the Keuper sandstones and marls of the West of England and in other parts of the British area, especially where these rocks approach a margin of Mountain Limestone. In the same way we might naturally expect to meet with dolomitic beds towards the base of the Keuper in a district where these rocks rest on a margin of Magnesian Limestone. The view that the upper portion of the saliferous rocks of South Durham belongs to the Trias and the lower to the Permian, seems to me, if anything, the most improbable of all. The chances, in the abstract, against two sets of beds of such an uncommon mineral as rock-salt occurring at the same point, and within 200 feet of each other in the same vertical section, in two distinct rock-series, are assuredly very great; but the chances against such a coincidence are vastly increased when we consider that there is no sort of sequence between the two formations in the district in question, but that, on * “The Permian Formation in the North-east of England,” ‘ Midland Nat- uralist,’ vol. iv. pp. 202-208 (1881). 7712 MR. E. WILSON ON THE DURHAM SALT-DISTRICT. the contrary, there is a decided break and unconformity between them, indicated by the omission of the whole of the Lower Trias or Bunter Sandstone, not to mention the Middle Trias, or Muschelkalk of the continent. I would here observe, parenthetically, that this discordance between the Permian and Trias of Durham is probably im a large measure due to want of conformity between the Upper and the Lower Trias, coupled also perhaps with an original northerly thinning out of the Bunter Sandstone. The very ample and Cheshire-like development of the Keuper series in the Tees valley (1800 or 1900 feet as com- pared with 600 or 800 feet in the East Midlands), taken in conjunc- tion with the total absence of the Bunter Sandstone in South Durham, is certainly a very suggestive phenomenon. In some parts of “the Midland district there are evidences of rapid attenuations of the Bunter Sandstone, as well as of actual discordance between the Bunter and the Keuper *, and in passing across Yorkshire something of the same kind evidently occurs. The arguments against the whole (as of any part) of the saliferous rocks of South Durham being Permian are also very strong. In- addition to the indications of the graduation of these beds upwards into undoubted “ Red Marls,” and the evidence of their mineral characters, which I affirm indicate that they belong to the Upper Trias, we have the negative fact, that no deposits of rock-salt have ever been found in any British rocks which have ever (rightly or wrongly) been assigned to the Permian period. Gypsum is, indeed, known to occur in certain Permian marls in this country, and, as‘we have lately learnt, has been found associated with the Magnesian Limestone of South Durham. Although beds of rock-salt oceur in certain continental Permians, not even a single pseudomorph of common salt has ever been found in any British rock of Permian age. On the other hand, rock-salt occurs in the Trias (Upper Keuper) of Cheshire, Staffordshire, Shropshire, Worcestershire, &c., and in the north of Ireland; and where we do not meet with actual beds of this mineral in these rocks, its former presence is very frequently indicated by salt-pseudomorphs or by brine-springs. A very little consideration will show that it is much more probable that beds of rock-salt should occur towards the base of the upper than towards the top of the lower of two discordant formations. Between the Permian and Triassic epochs in Durham there was certainly an interval in time unrepresented by rock-formation. Had any deposits of salt been formed towards the close of the Permian epoch, and thus left for long periods of time exposed near the surface, these beds would almost certainly have been destroyed during this interval. That the main mass of Rock-salt belongs to the overlying and not to the wnderlying rock-series is indicated by its persistence at a well- defined horizon f in the former for a distance of at least four miles (Eston to Greatham), in a direction at right angles to the average * “On the Unconformity of the Bunter and Keuper,’ Geol. Mag. 1880, p. 809 ; ‘ Geology of England and Wales,’ 2nd ed. 1887, PP- 221, 224. + See Vertical Sections, facing p. 782. MR. E. WILSON ON THE DURHAM SALT-DISTRICT. 773 strike of the non-conformable Permian and Triassic rocks. Some- times the rock-salt is entirely wanting, but in none of the deep salt-borings, colliery-sinkings, or more superficial excavations into the Magnesian Limestone of Durham have any saliferous beds ever been found associated with any undoubted Permian rocks. Area of the Salt-field, Limits of Distribution and Depth of the Rock-salt. The question naturally arises at this point, Can we at present form any conception of the extent of the area of the Durham Salt-field? All experience in other salt-districts ‘shows that ‘this mineral does not, like coal, lie in continuous beds of pretty uniform thickness over very extensive areas, but that it is liable to rapid fluctuations and sudden total disappearances. This evidently applies to the South-Durham salt-field. As we have seen, the thick salt-bed was present at Middlesborough in full development (100 feet). At Messrs. Bell’s Saltholme trial-boring, three quarters of a mile to the north, the bed was reduced to little more than half this thickness (65 feet) ; at the Newcastle Chemical Co.’s boring on the Tees, only three quarters of a mile west of these two points, the salt-rock had entirely run out. At Stone Marsh, about a mile further west, the rock-salt is present, but in a very attenuated condition; whilst at the equally distant Haverton-Hill borings it attains its maximum development in the district. Again, at the Greatham boring, midway between Middlesborough and Hartlepool, the salt is present in full thickness; but at Seaton Carew, a little over two miles north of this point, it is absent. In the seven wells put down by the Newcastle Chemical Co. on the Tees-mouth shore, the salt-bed was found to vary from 90’ 6” to 115’ 4", 7. e. 24' 10” in a distance of only 132 yards, a fluctuation at the rate of 1 in 16. Evidently, then, the bed consists of one or more * great lenticular masses. There is little reason to doubt that in this form the salt-bed has a wide distribution beneath the estuary of the Tees and the bordering districts. Itis fully developed at the Greatham boring on the north and at the Ormesby boring on the south, places four miles apart, and has so far been met with in good thickness at every exploration in a straight line between the two points. In a transverse direction (W.N.W. and E.S.E.) the salt-rock has been found well developed from the Eston Ironworks to Haverton Hill, a distance of very nearly three miles. How far the bed extends from the Greatham boring towards Seaton Carew can only be proved by actual sinkings ; but its absence in the recent Seaton and earlier Oughton borings seems to indicate that there is a considerable Triassic area bordering the Magnesian Limestone country which is destitute of this mineral. As regards the southerly extension of the rock-salt, the ample development of the thick bed at points between two and three miles * It is assumed as most probable that the thick salt-bed hitherto met with in the various deep borings in this districtis one and the same bed. See Vertical Sections, facing p. 782. 774 MR. E. WILSON ON THE DURHAM SALT-DISTRICT. apart on the south bank of the Tees is certainly hopefully suggestive of a wide distribution. It is probable that this mineral underlies a large area of the low-lying ground south of the estuary of the Tees, and it is quite possible that it extends beyond that region and beneath the Cleveland Hills of Yorkshire. Owing, however, to the prevailing south-easterly dips of the Secondary rocks of this part of England, and the consequent coming in of higher measures, the saliferous beds of the Trias and rock-salt can only be looked for at very considerable and constantly increasing depths the further we proceed in that direction. In the country north of the Tees, where the inclination of the New Red Sandstone is generally very small, viz. 2° to 8°, and in some portions of the district almost nil, the Salt-rock is found at depths of from 1200 to 900 feet or less. In the vicinity of the Tees the dip appears to increase to about 5°, so that at Ormesby and Eston, close to the south bank of the river, its depth from the surface is more considerable, viz. 1350 feet and 1570 teet respectively. South of the Tees the average inclination of the strata appears to be about 3°. Beneath the Cleveland Hills the greatest of these depths would be considerably exceeded, seeing that, partly on account of the dip and partly on account of the rise of the ground, the whole or the greater portion of the Lias, as well as almost the entire series of the Triassic rocks of the district, would have to be passed through before the rock-salt (if present) could be reached. We are now in a position to indicate approximately what these depths would be. At the Cleveland Salt Company’s Eston boring the sait-rock is reached through 1570 feet of Keuper marls and sandstones. At the gypsum-pit, midway between Eston Junction and the Eston Ironstone Mines, the highest stratum of the Keuper marls was reached at a depth of 190 feet from the surface, or about 154 feet below the sea-level*. Taking the dip between these two points as 3°S.E., and assuming that no faults intervene to affect our calculations, we should have to add 120 or 130 feet to the Eston salt-works section to arrive at the full thickness of the Keuper rocks down to the rock-salt. This would give 1700 feet, and the full development of the Triassic series, including the saliferous beds at the base, as probably 1900 feet or thereabouts. According to Messrs. Tate and Blake 7, the Lias and Rhetics beneath Eston Moor attain a maximum development of 1325 feet. Adding this to the Triassic strata overlying the salt-bed, we find that in this portion of the Cleveland district any wells sunk to the rock-salt, granting it to be present, would have to be at least 3000 feet deep. It has been supposed by some geologists that productive coal-measures underlie the Jurassic uplands intervening between the Durham and Yorkshire coal-fields, although the opposite view has genera]ly been taken (rightly, I believe) by most of those who are competent to speak on the subject. This is a question entirely beyond the scope of the present paper, and into which I do not intend to enter, beyond calling attention * «The Yorkshire Lias,’ 1876, p. 30. t Lbid. p. 193. af MR. E. WILSON ON THE DURHAM SALT-DISTRICT. vi 5) to the light recent explorations in the Durham salt-field have thrown on the very considerable depths to which any coal-explorations would have to be carried in the above district, even supposing productive Coal-measures to be there present. For, to the 3000 feet of Lias and Trias, we should have to add fully 800 feet of Permian strata, besides a more or less considerable capping of Lower Oolites. This would mean something like 4000 feet down to the surface of the Carboniferous rocks, a depth which was held by the Royal Coal Commission of 1871 as the limit at which it would be possible to mine coal. To return, however, to our proper subject, I would again insist on the want of all certainty there is in the distribution of so fluc- tuating and unreliable a mineral as rock-salt. All that we can safely say is, that the thick bed of rock-salt of South Durham has already been proved to extend over an area four miles by three or four in extent ; that it is highly probable that beneath the greater portion, if not the whole, of this area the salt-bed maintains a considerable (80 to 120 feet) and pretty uniform thickness ; that it is improbable that so considerable a deposit should rapidly die away in every direction ; and that, as previous explorations seem to show that the bed does die away in two given directions (N. and W.), there are reasonable grounds for anticipating its further extension in the opposite (EK. and 8.) directions. At the same time I do not mean to affirm that the disappearance of the salt-bed ata single point on the Tees is sufficient to prove that itis absent from the whole of the rest of the Triassic country beyond, stretching S.W. from the Tees mouth, or that its presence at three or four points on the 8.E. bank of this river is sufficient to prove its continuous and indefinite extension in that direction. It is a well-known fact that rock-salt never crops out at the surface, and it has been justly observed that so soluble a mineral as this is could not be expected to do so, since its outcropping portions would be speedily destroyed by the infiltration of surface waters. I do not, however, believe, as some have supposed, that this is the explanation of the absence of the rock-salt on the Tees opposite Middlesborough, and still less that such dissolution along the outcrop has originated the channel of that river. The point referred to is between four and five miles from the outcrop, and here the horizon for the salt-bed lies 1000 feet beneath the surface and is bounded by impervious marls. The salt-rock has also been met with at other points nearer the outcrop. At Seaton Carew which is about one mile and a half from the outcrop of the Magnesian Limestone, the horizon for the salt-rock would lie at about 500 feet from the surface. Here also the measures were, I understand, dry, and there was no evidence in the shape of brine or other springs at this horizon to explain its disappearance. We may broadly assert that in the South-Durham salt-district the salt-rock (or the stratum occupying its horizon) is always enclosed between impervious beds and is free from water, having what is known in the Cheshire district as ‘a dry rock-head.” If this salt-bed ever did crop out at the 776 MR. E. WILSON ON THE DURHAM SALT-DISTRICT. surface, of which fact I am by no means satisfied, the effects of surface-infiltration would, I believe, be limited to a small lateral extent ; because on the removal of the salt the impervious roof would subside on to the impervious floor and the surface-action would be brought to astandstill. It has been suggested that certain eavities and swallow-holes met with along the boundary of the Magnesian Limestone between Hartlepool and Darlington, and also near Ripon, may be due to the dissolution of saliferous beds; but it seems to me more probable that the true explanation of these hollows is the same as that for similar phenomena along other lime- stone boundaries, and that the peculiar forms of the cavities may be due to the rapidly varying character and solubility of beds of the Magnesian Limestone. I therefore conclude that the present exten- sion of the rock-salt in South Durham is defined by the limits of its original area of deposition and not by subsequent dissolution by outcrop or other infiltration. Method of winning the Salt, Waste in working &e. It would be beyond my powers and outside the scope of this paper to consider the chemical and mechanical details of the mining and manufacture of salt in the Durham district. For full information on these matters I must refer those who are interested in the subject to Sir Lowthian Bell’s admirable essay ‘‘ On the Manufacture of Salt near Middlesborough”*, There are, however, certain consequences of the method of working the salt-bed there described which cannot be considered as altogether satisfactory, and to which I should like to call attention. The salt is extracted from its bed by solution, by a method which has for some time past been in operation at Nancy, in France, but was introduced for the first time into England by Messrs. Bell Bros. about twelve years ago at their Saltholme works. The process is as follows:—A hole from 6 to 12 inches or so in diameter is bored down to and through the Rock-salt, and is lined with an iron retaining tube ; within this an inner tube of 2 or 4 inches less diameter is let down and secured below ; both tubes are perfor- ated with holes where they pass through the rock-salt ; fresh water is let down the space between the two tubes, and this passing through the outer holes gradually dissolves the salt ; the brine thus formed enters the inner tube and rises in it as high as a column of fresh water will support a liquid having a sp. gr. of 1-204 or there- abouts, and is drawn up the remaining height by pumping. Now it appears that this system of working the salt, although far more economical for raising this mineral from great depths, both as regards the capital and the labour employed, than by sinking a shaft and regularly mining as in the case of coal, is extremely wasteful, having regard to the proportion of the salt which is extracted from its bed. It is found that a single borehole will only extract a limited amount * Loc. cit. See also paper on “ The South Durham Salt-bed and Associated py read by Mr. W. J. Bird to the Manchester Geological Society, June 5, MR. E. WILSON ON THE DURHAM SALT-DISTRICT. Tt of salt. ‘This is apparently due to the insoluble earthy residue of the rock-salt (which in the Durham salt-bed seems often to attain rather large proportions), coupled with falls from the roof, forming in time over the floor of the cavity eaten out of the salt-bed a thickish earthy layer which is impervious to the solvent water. Thus, after a while, the brine is found to become weaker and weaker, until in time it will not pay to raise. Again, the bed of rock-salt appears to be dissolved away by this process in a very unequal manner, viz. much more rapidly above than below, owing to the fact that the saturated brine which sinks to the lowest depths of the borehole has not nearly such solvent power as the comparatively fresh water which floats upon it. Hence the cavities eaten out in the rock-salt at the bottom of a brine well assume the form of imverted cones, of which the bottom of the well is the apex. This leads us to infer that in the course of time, when the inevitable subsidences set in, a number of cavities will be formed at the surface which will con- form to the general contours of these subterranean cavities, and of course the unequal character of such subsidences would be particu- larly destructive to surface properties. It appears further that, as the law now stands, owners of land adjoining these wells, unlike owners of land undermined by coal-workings, have no legal claim for compensation on account of the damage done to the surface, nor for the loss of the mineral which has been abstracted from beneath their property—a palpable injustice which it seems impossible to suppose can be allowed long to continue. These special evils would be removed if the salt-rock were mined and in other respects treated in the same manner as coal. By that mode of working, too, a much larger proportion of the bed might be extracted, as well also as a good deal which extends beneath the sea; but whether it would, by any method of working, be practicable to mine the whole or even the greater portion of an immense mass of rock-salt 100 feet in thickness, lying at depths of from 1000 to 2000 feet, I am not able to say, nor can one forecast the precise limits of the destruction which might result through subsidence, were such a thing done. I would conclude with the remark that, vast as are the stores repre- sented by this thick and widely distributed bed of Durham salt (about one hundred million tons per square mile), the supply of the mineral is not absolutely unlimited, and that the interests of future generations as well as those of ourselves and our own immediate successors ought in a matter of this kind to receive due considera- tion. In addition to acknowledgments already made, I am indebted either for valuable information or for references to Mr. Horace B. Woodward, F.G.8., Mr. Alfred Allhusen, M.I.C.E., Manager of the Newcastle Chemical Works Company, to Mr. John Harrison, Secre- tary of the Cleveland Salt Company, and to Mr. Rowland Gascoyne, F.G.8., of Mexborough. I am also specially indebted to Mr. W. J. Bird, Mining Engineer of Sunderland, for the section and loan of cores of the Seaton-Carew boring. 778 MR. E. WILSON ON THE DURHAM SALT-DISTRICT. APPENDIX. Section of the Cleveland Salt Company’s Boring at South Bank, Eston on Tees, 1585. fi. | in) aoe =) Made ground . 2. 4 0...testecseeneseoneeee renee Go" a6) | Blueisandy Clay <2 TO ey get 4 Dark brown, Glayn..cngbet- eee eee 7 0 4Is B46. | Soft red. marl, 5... 22.4 at ea eee 2, » pO El Brown © Pinnel 132020 eee 16. OY a { Red marl a APR eee tee eee 22 10 \ Ge E Red and blue marl with veins of gypsum 31 3 | 5 3 | © 2 | Red marl with veins of gypsum ............ 46 8 Ke = 4 = % ) Red and blue marl with veins of gypsum 15 3 ‘ 453 0 a 3.4 Red and blue shale with veins of gypsum... 325 O {| = a | | Blue shaly Sandstone ...............-.-.:--+- 2 O | 5a Se Red Sandstone with thin beds of gypsum \ A‘ andishalen Sie! on oe tao eee 10:30 Ff (Sandstone with thin beds of shale ......... 1, An Red Sandstone 2 eeer- apni. eeeeec nea tekeorees 415 8 Red Sandstone with thin beds of marl ... 39 0O | | Red sandy Marl ..............00..seeeescee eee 846 2 «| eed Saavsione cro 2. scees ese --eeree 29 0 | | & | Wed sandy Mrvel ooo cee ctr 4 2 ls d Red Sandstone with thir beds of Marl... 46 0 793 6 a\|& | EEE lots 2c bgp eR ca leeds pian ante pe Baa SM CI - z | % | Red Sandstones with beds of Marl ......... a4) WG Ey | ey ve Maat ds liepees See coal ho kee. oe oe 17; 48 | a | = | Red Sandstone with beds of Marl ......... 138 7 5 Red Marl with beds of red Sandstone ... 21 I1 | = | Red Sandstone with beds of Marl ......... 14 6 “4 | Red Marl with Sandstone ..........00...... Ss Ce Bd sof SeedoNicecleg: 4 ese ep eee mee te ee 43 0 \ 5 Red sandy Marl with blue spots and veins y | Cg 7 CTL CS San em mee ny iN ie Tee 6 | = | 2 | Redsandy Marl with thin veins of gypsum 78 0 = | & 4 Red sandy Marl with veins of gypsum and 282 3 5 Ss) -bluesppisn clasts Se SOnFD | 4 Avlydeate bu25.:4 36+. fea ece ee eee i] sia | = | Red sandy Marl with Salt .................- 21. O “(Red Marl wath’ Salé":.0. 0: gsc cetpenceoer ace 6 Sid | 3 Riock:ssaui Ue cierer bottcwen nee ene ss eb ea topes a1 sr°-"6 Anhydrite with Salt ‘2 3.224.0.0: 2: ie ies 6 Anhydrites: 43. 3.2 he ae eee ‘horn © ! 28 «11k \ Anhydrite and a little Salt .................. 25, 114 1679 83 / —— = MR, E. WILSON ON THE DURHAM SALT-DISTRICT. 779 Section of the Newcastle Chemical Works (o.’s No. 1 Boring, Post- Alluvium, &e. ot ——_———~_ Tertiary. Urprrr Kerurer (WATERSTONES). Red Sandstones. — A A —_———_—_—_<_ Magnesian Lime- Saliferous Permian (Upper). stone. Marls. on the Rt. Tees, opposite Middlesborough. fi, in. Peatiand muddy. sand tivsssesavesmastiaseen se i? 0 Mame aandiy: Claw y....vadesakednunwawspanteunaesan 605-0 SAPICE CLAM acct uecddeatnaidstarone sd abeeamareeas 1s oe PUUNINE SAN ,..cccaconsesesesecneans sienna 35 «(OO iPlard-bound. Ghraivel:\. «2... dausves.vaeei. dabientey TAO PROCS EP WTITIGL o ecinisiain stansaininennsineneice cite 12h,0 Red sandy Shale with gypsum............... 35 «(OO Grey sandy Shale with gypsum ............ 10. 0 Red and grey Shale with gypsum ......... 29 =O Red and grey sandy Shale .................. 36 COO FEC WAMORTODE asain ap circles senivioit, cakes 314 0 BS LCs cchaciolreid natvieceldsieinsisilanalepaninas ae iain a 5050 PREOSAOSL OME. gcc ienqasewisinn.sadaieasae ncenee ete 33 «6 ROCIO. cc asin spadebnsatrceeids ek ojtiweile ob alaatiel eal @ RGM MS AE CSE OMG s aisisnsinicimisins.nainavinivaiiensitinea sae 46 6 RCO I SORE) smwsiesiak tna dbboue nth nerd wh intiiale ts Divan LOOM SAIGSLOMG » desmwrdaasmeleaveatianhs oa ulvdce au 47 0 PGES MAC, vs camsearinetancns deldkdowe -abiicle deandatie tae | Red Sandstone ........sescseeeseeesseesreeees 794.0 POUR AIG, .05cennadalaactiv once cdsine domannce onleaiaite 8.6 USAR SRMORLONO ot andoncdcteneeaedeisasinacdssuntas 29 6 PRETO SEIAIG 5 aaissswntdeidinn du netthbedbeavvalncl ellodts 9.6 MGR SHIGSUONDicc usiianwacinnawemesinssines voces eens 35 «6 Pe SHO esc dag sn asidianadandaaoci geass xxacnite pe 50 \ Red shaly Sandstone.........scscececccenssees an ssin 0 Red Shale with beds of Sandstone ......... 865° .0 Red Shale with small blue joints and veins GRP SEITIN S25 aps cassis sisioplelejeinciisiiebiie eis oeRa 60 6 Red and grey Shale and gypsum............ 24 0 PATE GONG, 0 faseniiaa nents dani ile cclahes, Havas 68 6 Magnesian Limestone ..............ccseeceeeee 40 0O A ny Gib: Fy PSUR eidac cis cies -\narnivaie cmee Se acts Di 20 BV MEE AYPSUN,. soscnoneasindantinatncaeecana ts «ase 13 6 SPV tte ROG) cee coecn ce snienansesesacesensnenncee 1h en) Magnesian Limestone. ..........c0cccecesnenes 39 «6 PAT CCTV PBUUD, ov anudiatansscdieasisesividuenllcs 3. O Dark grey Limestone with gypsum......... (AA | Magnesian Limestone and gypsum ...... 20 O 1260 0 = = 5 Je) We) =) ~J io) Oo i) —" =I =) for) bo S =I fer) YS SES > eer —““_ ——" Norr.—No beds of Rock-Salt were found in this exploration. The oc- currence of gypsum and anhydrite in association with Magnesian Limestone in this Section is worthy of notice. Section of Messrs. Bell Bros. Trial-Boring at Saltholme, Post-TERTIARY. near Port Clarence, Durham, 1874. | Weems. cctasiasciacarestieasasssaticcqetagmereeaaes i 4 7 Cleat Sand )jccasacawevarassssospensiagidsioaansaad 26 eGh Clay’ sa2i0cscceraanatvonudanssaanedecenwecaaene 3 sang and Gravel» -sssasiccsescocaaasceevaerases 8 WBoulder-Claycsccicccsasatuscoocaszacneceeds ote 27 OOOO ASo & Carried forward...cccsccscccccces (i \ ie a 0 ) 80 Uprrr Knurnr (Warnrstonns). MR. Ee WILSON ON THE DURHAM SALT-DISTRICT. Section of Messrs. Bell Bros,’ Trial-Boring (continued). ee bet n. in. Brought forward .............8. 102g te 0 ff ied! Maar). 8.0... cecna nase ee Beige Red Sandstone with veins of Marl ......... 144. 0 White Sandstone, ..:..<.2252-.554c. eee Luthe | Red Sandstone with veins of Marl ......... 153. 9 Red Sandstone.....i.a 3 afl Rie ees me Joan — Soc a \teee fe S22 py [ears fae g Oe a = Korn 878'0 wD [rey Dee jo) ase Blags Jeg Me as A eo 2 (2) oa Mie 3.8 a= =r | a ry i i Sle Ttedl Sandatones, with subor- ZnO 5/4 dinate Marle’ and o little n a HY PBUITE sr ceter eee et enter eseeeeseee B18 alk olE D i] FE lia fi : & - Pe eb Rod Marla, with gypsum and | 282! 3” ¢ walt | ig 5 5 Dn ee | sro f | Rookewalt cassie Anhydrite, gypsum, and marie a8'11}" NOTH.—All these borings were made in a country which is remarkably fiat and so little above the sea, that for all practical purposes we may assume them to start at the sea-level. Sections of Deep Borings in the Durham Salt-District. MIDDLESBOROUGH. * Oleveland Salt Co.” (Bolckow, Vaughan & Co.) 802" 0" R. TEES. ** Newoastle Chemical Co.” 783! 0” 170' 6" (Seale : 300 feet to an inch.) SALTHOLMBE. Messrs. Bell Bros.” Trial-Boring. 778" 0” “Limestones’ and Marls, with 136' 0" gypsum. eae Rock-sal¢ (1.41 0, Marl wit ard gy pum eel 4! TEES MOUTH. “ Newcastle Chemical Go.” S17 0" ~ to Liz! o" GREATHAM. Messrs. Casebourne & Co. [To face p. 782. ; N. SEATON CAREW. Messrs, Casebourne «& Bind, Shasnaven. nro } say's” or 87a’ ov CARBONIFEROUS_ - Siekt BATS FTE OS. Te el “4 oC = hess ” unrest EZ 0 OVI) Oy ON THE HORIZONTAL MOVEMENTS OF ROCKS, ETC. 783 44, On the Hortzontat Movements of Rocks, and the Rutatton of these Movements to the Formation of Dykes and Favtts and to Denvpation and the Tuicxentne of Srrata. By WittiaMm Bartow, Esq., F.G.S. (Read April 25, 1888.) I propose to call attention to some horizontal movements of rocks occasioned by gravitation, the importance of which has, I believe, been almost entirely overlooked, and shall try to show that the great forces of denudation in many cases owe much of their power to fissuring and dislocation produced by these movements, also that to these movements is to be referred the production of dykes and faults. In the Grand Canon District of the American Union a wide expanse of elevated horizontal strata, some thousands of square miles in extent, has been denuded in such a manner as to display a succession of huge terraces or steps of successive strata, each terrace being terminated by a sinuous line of cliffs or abrupt slopes. Between the succeeding escarpments the strata dip slightly from the crest of the one below to the foot of the next above. In the median parts of any given terrace the strata are very nearly hori- zontal and have inclinations scarcely exceeding one degree ; but as we approach the escarpment of the next higher terrace, the inclination increases to three or four degrees, becommg a maximum at the base of this wall. The cumulative effect of the slight dip thus displayed, which for the most part has a northerly direction, is that the top of a certain stratum, the Carboniferous, is more than 8000 feet lower at the north, below the topmost terrace, than at the south, where it comes to the surface and forms a wide plateau, the lowest terrace. The difference in altitude between the highest and the lowest terrace is several thousand feet *. In the same district of horizontal strata the forces of denudation have removed the upper strata to a great depth over a large area of elliptical form, producing in this way a great hollow, many miles in diameter, enclosed by cliffs and known as “‘ The San Rafael Swell.” Here also there are indications of a slight elevation of the unloaded strata within the denuded space as compared with the continuation of the same strata where they are heavily loaded beneath the sur- rounding cliffs 7. It has been suggested by Mr. Dutton that the phenomenon referred to is analogous to the action of creeping in deep mines; and Mr. Clarence King, in reference to the subsidence of strata in the same locality, makes a similar suggestion £. * «Tertiary Hist. of the Grand Cafion District,’ C. E. Dutton, pp. 47, 70. Tt ‘Geology of the High Plateaus of Utah, Dutton, pp. 18-21. ft U.S. Geological Exploration of the 40th Parallel.—I. Systematic Geology. 3F2 784 MR. W. BARLOW ON THE HORIZONTAL The phenomenon of creep * may be defined as the thickening of the parts of beds from which a load of superincumbent rock has been lifted, caused by a thinning of the adjoining parts of the same beds, which continue loaded, some of the substance of the latter being squeezed out to furnish the material for the thickening. The effects are, however, so extensively diffused that, although it is the hori- zontal components of the motions of the rock-particles which alone determine the extent of a creep, it is the vertical components of these motions which alone force themselves on our attention ; thus Buddle tells us, ‘‘ he has never noticed any tendency to a sliding or sideway movement in any subsidence of strata occasioned by the working of the coal, except the slight obliquity occasioned by the offbreak at the sides of the settlement where the strata are bent down and cracks formed ” +. If we regard the phenomenon recorded by Dutton as an instance of creep on a large scale, we must conclude that a lateral extension of the beds still remaining heavily loaded has taken place, and that a large mass of material has, somewhere below the surface, been squeezed out from beneath the cliffs. Further, the movement of this large mass must have produced a considerable horizontal thrust, — which, as the process was no doubt very slow, and the lower ground at the foot of the cliffs of considerable extent, would be transmitted through the rocks underlying this lower ground to a very great distance. The effects of such a horizontal thrust are, in the cases referred to, and in most other cases where masses of rock are similarly bounded by precipices or steep slopes, hidden from view, but there are in- stances where they are to be traced. Thus many evident examples of plication traceable to horizontal thrusts produced by gravitation are to be seen in Glacial drift. And from the fact that comparatively small masses of rock have been able by their weight to squeeze up plastic Boulder-clays and soft sandy layers on which they rested into folds and contortions, we may fairly conclude that the unequal distribution of weight at the earth’s surface, due to the presence of lofty cliffs and mountainous blocks, has been able during long periods of time to produce consider- able plication, even of the more intractable rocks, in the same way. It can scarcely be doubted that many instances of plication generally attributed to secular contraction of the earth’s crust are traceable to the cause I have named. This will especially be the case with subsidiary plications found on the flanks of mountains ; for wherever there are great inequalities of surface, rocks far beneath the surface and consequently having considerable plasticity, will be materially affected by the unequal distribution of the weight of the rocks above them, and will spread in the same way as the Boulder- clays referred to have done. It has been suggested that much of the contortion and upheaval of the later Tertiary rocks of the sub-Himalayan zone has been * See ‘Student’s Hlements of Geology,’ 2nd edition, p. 55. Tt Proc. Geol. Soc. vol. iii. 1842, p. 149. MOVEMENTS OF ROCKS, ETC. 785 caused by a partial sinking of the central regions, due to a reflex action, the protracted adjustment of equilibrium after the great mountain-features had been fully developed *. There is, I submit, another effect produced by the creeping move- ment of large masses of rock, where, owing to the presence of preci- pices or slopes, they are insufficiently supported on one or more sides, and itis one which I believe to be of considerable importance. In the description of a creep given by Lyell reference is made to the production of cracks in the pillars of coal left standing in mines. These cracks are generally quite close, but very numerous; they are no doubt due to the strain induced by slight inequality in the yielding of the bed supporting the coal, and thus have a precisely similar origin to the joints and fractures artificially produced by Daubrée in different substances which he subjected to undulatory movement by torsion, or to simple pressure 7. Now the precipices of the Grand Cafon district indicate in a very remarkable manner the presence of joints and fissures. Over and over again, in the descriptions given by the geological explorers of these regions, we come upon expressions of surprise and admiration at the extraordinary architectural forms into which the cliiff faces are carved t, and this is especially the case with regard to the higher cliffs §. These sculpturings are, we know, mapped out by the joints and fissures present in the sculptured masses ||, just as in a quarry the readiest way of working the stone is determined by the positions of the joints and fractures. If therefore we conclude with Daubrée that joints and fractures occurring in nature are due to small torsional movements taking place in the rocks, we shall argue that some part at least of the effects referred to have been initiated by joints and fissures caused by creeping movements of the rocks due to their position in the faces of precipices, 2. ¢. to their want of support on one side. An observation made by Mr. Dutton confirms this view, and seems to indicate that fissuring produced by the small horizontal movements of rocks thus situated has important consequences in facilitating denudation. He tells us that he has repeatedly noticed that where a fault runs in a direction perpendicular to the trend of a cliff, the recession of the cliff is less on the side of the downthrow than on the other side of the fault 4. It is manifest that the higher the cliff the greater the superin- cumbent weight upon the rocks at its foot, and the greater the creeping movement and the jointing and fissuring consequent upon this movement. This jointing and fissuring weakens the rock and * H. B. Medlicott,‘Mem. Geol. Survey of India, iii. pt. 2,p. 174; and Quart, Journ. Geol. Soc. vol. xxiv. p. 48. + Géol. Expérim. (Daubrée), Part 1, section 2, chapter 2. t ‘ Geology of the High Plateaus of Utah ’ (Dutton), p. 254. § ‘Tertiary Hist. of the Grand Cafion District ’ (C. E. Dutton), p. 204. || ‘Géol. Expérim.’ p. 3824; and ‘ Tertiary Hist. Grand Caiion District,’ p. 53. €| ‘ Tertiary History of the Grand Canon District,’ p. 200. 786 MR. W. BARLOW ON THE HORIZONTAL prepares it for degradation ; and therefore the above phenomenon observed by Dutton is what we ought to expect if the jointing and fissuring produced in this manner in the cliffs of the great terraces are appreciable *. I believe, then, that we have in this weakening effect of gravitation on rocks an important key to some of the peculiar features of the great erosion which has taken place in the plateau country of the American Union, and, indeed, that it is an important factor im the waste of almost all cliffs. I should not be surprised if it were found to have a very appreciable influence in all cases of mountain denu- dation. From the consideration of the production of joints and small, comparatively superficial fissures by gravitation, I will now pass to the consideration of the production of extensive fissures by the same agency. In a landslip the spreading of some underlying bed, which has become plastic through the percolation of water, or from some other cause, drags apart the more solid intractable beds above, and produces fissures and fractures transverse to the direction of movement f. . Familiar examples of fissuring produced in this way are often seen in railway-cuttings made through clay, also on the verge of sea-cliffs. The horizontal movement which produces the open fissures is in these cases, aS In the case of most large landslips, due to a squeezing and lateral extension of the material some distance below the surface, and the consequent dragging apart of the mass above. I suggest that most of the fissures produced in voleanic districts have a similar origin, and also that the same simple cause is the origin of trap-dykes. First, as to the production of fissures. Wherever a considerable body of moiten rock exists below the surface, its own weight and the weight of the solid rocks resting upon it will together produce considerable hydrostatic pressure throughout the molten mass. And the rigidity of the crust not being perfect, some movement, slight or otherwise, of the molten matter will take place towards points where the superincumbent weight is least—that is, provided there is not absolute equilibrium. Therefore if the ground-surface is much higher over the tract of molten matter than it is just beyond its limits, the molten rock will tend to spread by its own weight and that of the solid crust resting upon it. And as all rocks are more or less plastic, we may, in this case, look for some horizontal movement, small though it be, of the solid rock at the confines of the molten mass, and which is subjected to its thrust. * Dutton refers the phenomenon to the fact that those regions which have been elevated most have been most degraded by erosion; but this explanation does not appear to account for the lower portions of the higher cliffs having a greater rate of recession than the corresponding portions of the lower cliffs, but only for the greater erosion of the upper parts of the higher cliffs. Indeed, the lower portions of the higher cliffs are manifestly more protected from erosive agency owing to the greater amount of material which falls over them from above. tT Dana's ‘ Geology,’ 8rd edition, p. 666. MOVEMENTS OF ROCKS, ETC. 787 Any such yielding of the solid rocks around to the pressure of the molten rock will tend to draw apart the solid crust resting upon it ; and thus if the crust is not too strong, we shall have the ground opening along lines of weakness such as are produced by the presence of joints or other close fractures, and more or less extensive fissures will be formed. And in some cases, where there is any considerable adhesion of the crust to the spreading mass beneath, and the spreading is great in amount, the crust may be expected to break up into larger or smaller fragments, much as the ground-surface breaks up and separates in the case of landslips. In cases where the quantity of molten matter spreading is large, relatively to the thickness of the solid crust, and the conditions are such that the mass spreads considerably in seeking equilibrium, the force operating to extend and rupture the crust will, it is evident, be both great and of long continuance. Jn all cases the degree of viscosity of the molten matter, and the degree of plasticity of the solid crust, and the presence of joints and fissures will all be impor- tant factors in determining what effects are produced *. Next with regard to the production of trap-dykes. When a large mass of molten matter is present near to the surface, and a fissure is produced in the manner referred to, the weight of the ruptured crust will, if the plastic mass beneath be liquid enough, cause the latter to rise in the fissure, either as it forms or immediately after its formation. The view that the production of the fissure precedes and is distinct from the extravasation of the matter forming the dyke, and that the latter is due to a relatively gentle hydrostatic force not capable of driving the lava into and through solid rocks, is supported by the fact that in many volcanic eruptions, lava flows out quietly and with- out explosive violence 7; also by the fact that a subsidence of the strata around volcanic vents, such as would follow the hydrostatic movement of the lava, is sometimes seen +. Dutton tells us that ‘a careful examination of the details of vol- canic eruptions leaves the impression that they are pressed up by the weight of rocks which overlie their reservoirs, and that their ex- travasation is merely a hydrostatic problem of the simplest order” §. The rending of the rocks preparatory to the extravasation of molten matter has, according to the view I have submitted, commonly taken place with suddenness and on a large scale. And I think we have evidence that this has been so in the case of many dykes, in the familiar fact that they generally take their course without regard to the irregularities in structure and disposition of the masses they * An instance of a large body of solid rock, which overlay molten rock, shifting in the manner suggested, is given by Mr. Dana: see his ‘ Geology,’ 3rd edition, p. 731. tT Scrope’s ‘ Volcanos,’ 1872, p. 160. t Scrope’s ‘ Volcanos,’ 1872, p. 228. The formation of gases and heat-expan- sion of rock which occur beneath volcanic vents will, it is evident, operate to produce elevation of the crust ; and it is not therefore surprising that subsidence should be observed but seldom. bid. p. 226. § ‘Geology of the High Plateaus of Utah,’ p. 130. 788 MR. W. BARLOW ON THE HORIZONTAL penetrate, preserving wonderfully straight courses, even across frac= tured and irregular strata, often for miles together. An observation recorded by Mr. Dutton relative to the situation of some volcanic vents seems to be confirmatory of the view sub- mitted above, that the presence of precipices or steep declivities has a weakening effect on the masses of rock which they bound, producing in these masses faulting and fissuring that greatly facilitate their degradation. ‘Thus he tells us that basaltic vents occur very often upon the brink of cliffs of erosion, and never (within his observation) at the base of one; often upon the top of the wall of a canon and never within the cafion itself, though the stream of lava often runs into the canon; and he instances ten large cones standing upon the very brink of the Grand Canon which have sent their lavas down into it. And he also mentions, away from the Canon, a considerable number of craters upon the various cliffs near the Hurricane Ledge, and far to the north-eastward half adozen upon the crests of the White Cliffs. He states that out of rather more than three hundred basaltic cones of this region, he has noted thirty-three, or nearly eleven per cent., occupying such positions *. The fact of no vents being opened at the bases of the cliffs is quite in harmony with my views, for if the spread of the rock underlying the cliffs is producing a thrust against the crust lying near their bases, as I have argued it is, the tendency will be for this lateral pressure to keep fissures closed. If, however, the underlying mass of lava is of great extent, and the ground-surface beyond it much lower than the ground-surface above it, so that the spreading movement of the lava is general and considerable, the local effect just traced may be partially lost in a more general one; the two walls of a canon may move bodily further apart and produce a fissure within it, the site of the canon being a line of weakness. Even in this case, if the movement takes place gradually and. slowly, it is possible that the local effect just referred to would keep the bottom of the newly forming vent closed, and pres the extravasation of lava within the canon. An interesting case of a volcanic eruption on the verge of the Grand Canon of the Colorado recorded by Mr. Dutton may be referred to in support of my views. On the south side of the canon a lateral. gorge or amphitheatre is excavated in the chasm-wall, very nearly as deep as the main abyss. At the summit of the wall of the inner chasm, just at the angle which it makes with this lateral gorge, a ruined basaltic crater stands upon the very brink, the dyke through which the lava came up and several neighbouring dykes being seen projecting from the face of the wall of the lateral gorge throughout a depth of half a mile. The strike of all these dykes is parallel to the. river, showing a probable connexion between the position of the rwer and the formation of the dykes. The presence of some remnants of tufa-beds several hundred feet down indicates that the subsidiary * “Geology of the High Plateaus of Utah ’ (Dutton), note, p. 203. _ ae | MOVEMENTS OF ROCKS, ETC. 789 chasm must haye had some considerable depth when these dykes were formed*, The uniform width of dykes throughout such great heights as are attained by those just mentioned is manifestly a serious difficulty in the way of theories of dyke-formation which suppose the fissuring to have been caused by upheaval. It is almost equally incompatible with any theory of fissuring by the pressure of the intruded rock, supposed to act as a wedge; for surely the displace- ment of the material of a solid rock caused by the forcible intrusion of a thick mass of trap into the lower part of it would produce some torsional movement of the masses wedged apart, even sup- posing it did not cause any upheaval; and if there was a movement of this kind, how was the parallelism of the sides of the fissure preserved ? Again, the suggestion that the production of dykes proceeds from the dragging apart of the solid crust by a stretching force is in harmony with the fact that the deeper fractures from which igneous flows take place have occurred where there was little folding, and the more of the one, the less of the other. In the Appalachians, where we find indications of great lateral compression, no such outflows are knownt. While, however, the bending of strata is not the immediate cause of the fissuring which has produced dykes, it is evident that in many cases it may be the cause of fractures or joints, which afterwards are converted into fissures by the spreading of underlying molten matter in the way suggested §. That the body of trap injected is, in some cases, relatively so large ||, is no difficulty in the suggested explanation. Where this is so we shall argue the presence of a large mass of molten matter beneath the crust at the time of the injection, and a large spreading movement of this mass. It is, however, otherwise with theories of fissuring by contraction. For where numerous cracks or fissures are produced in a substance by unequal contraction due to unequal cooling, they always have a relatively small magnitude ; and to account for large dykes in this way it is necessary to make some additional supposition, such as, that the molten matter exerts hydrostatic pressure laterally—a supposition very difficult to allow, when we find no effect of such a pressure in an upward direction, that is, in what is generally the direction of least resistance. Most, if not all of the effects which I have thus far endeavoured to connect with horizontal movement produced by gravitation are displayed in a particularly instructive manner in the singular group of mountains in the Plateau Province of the American Union known as the Henry Mountains. * Tertiary Hist. of the Grand Cafion District, p. 95. tT See also Scrope’s ‘ Volcanos,’ p. 165. t Dana’s ‘Geology,’ p. 791. Dana says thata lateral pull rather than a lateral pressure is apparently required for the origin of some dykes. bd. p. 803. § Dana’s ‘ Geology,’ p. 803. || See Macculloch, ‘System of Geology,’ i. p. 110. 790 MR. W. BARLOW ON THE HORIZONTAL The elevations of the earth’s crust which form these mountains are the outcome, on an exceptionally large scale, of the common phenomenon of lava penetrating but part way to the surface in dykes, and then diffusing itself between the beds and forming subterranean lakes or deposits of lava. In this case very large deposits were formed, the intrusion of which lifted great thicknesses of superincumbent strata, and produced huge dome-shaped elevations of the otherwise nearly horizontal beds. These very regular protuberances were afterwards carved by denudation into rugged outlines of ridge and cafion. The chambers occupied by the intruded trachyte are in some cases over three thousand feet high. They have in each case been made along a shaly layer in the formation where the cohesion was — least*. They occur at different levels in the strata, and the lowest in geological position is 4500 feet below the level of the highest. Large as is the scale on which the effects have been produced, it does not appear necessary to attribute them to the action of any other force than the force of gravitation acting in the manner I have already described. Thus, first with regard to the frequent phenomenon of dykes stopping short before they reach the surface, a phenomenon of which we have here such important examples. In most cases where a body of molten rock spreads and produces dykes the solid rock immediately over the liquid mass will experience the lateral pull first, and thus the vertical fissures which receive the molten rock will begin to open from below. And in cases where the upper strata are more plastic than the lower, or where they form an elevation on the surface, and thus are less completely attached to the rocks around them, it will often happen that, while the lower strata of the solid crust are fissured, the upper strata will make sufficient movement with respect to the lower to avoid rupture. It would seem that the whole district about the Henry Mountains has experienced a force which ruptured the lower strata and extended the upper strata without breaking them. Thus Mr. Gilbert says respecting this district t: ‘‘ It seems as though the crust of the earth had been divided into-great blocks, each many miles in extent, which were moved from their original positions in various ways. Some were carried up and others down, and the majority were left higher at one margin than at the other. But although they moved independently they were not cleft asunder, -the strata remained continuous, and were flexed instead of faulted at the margins of the blocks ” +. And further on the same writer adds: “‘ It has been the opinion, not only of the writer, but of other students of the displacements of the West, that the ordinary sedimentary rocks, sandstone, limestone, and shale are frequently elongated as well as compressed by orographiec * «Geology of the Henry Mountains,’ by G. K. Gilbert, p. 58. T bid. p. AN: { The mountains stand within the province of the great flexures, but are independent of them. MOVEMENTS OF ROCKS, ETC. 791 movements, and that this takes place without any appreciable metamorphosism; but it is difficult to find opportunity for the demonstration of the phenomenon by measurement. . . . Of the unfractured quaquaversals of the Henry Mountains there is one which combines all the essentials of a crucial case. The ‘ Lesser Holmes’ arch is nearly isolated; on three sides it rises from the undisturbed plateau, and on the fourth it joins a similar but fractured dome. The major part of its surface is composed of one bed, the Vermilion Cliff Sandstone, broken only by erosion. Comparing the length of this bed in its present curved form with the space it must have occupied before it was upbent, I find that in a distance of three miles it has been elongated 300 feet”*. Second, as to the diffusion of lava between some of the beds which have been penetrated. This may evidently be attributed to the lava having a less specific gravity than that of the strata which it penetrated, and to a lack of cohesion between some of the invaded layers which allowed portions of strata that were weakened by vertical fissuring to break away from the better-supported rock above, and gradually to bend down while the liquid lava passed into the horizontal rift which was thus forming. Third, as to the elevation of the upper crust to form protuberances on the surface. If the fissures had extended through the crust, the lava would have passed up, and, having a specific gravity less than that of the crust, would have welled out over the surface. Now, suppose a very thick layer of plastic extensible clay had lain at the surface, and that the fissures formed extended through all the strata except the clay. The lava would in this case also have welled up, though while the clay remained unbroken it would not reach the surface, but would push up the clay; and it would continue to act thus until the hydrostatic pressure downwards, through the fissure, of the accumulating lava and the clay resting upon it balanced the hydrostatic pressure Bena caused by the slow sinking of the fissured crust. The same line of argument manifestly applies to any case in which, as in that under notice, the upper crust is sufficiently flexible to yield to the pressure brought to bear upon it. The reason why, in the Henry Mountains, the crust yielded in such a way as to produce the wonderful effects recorded is because in that particular spot the lava became very extensively diffused in wide sheets between the layers of strata. For we see that an exceptionally great diffusion of lava in this way must inevitably expose large surfaces to upward pressurey, at places where the solid crust has less thickness and therefore less resisting power than in the region around. I will now call attention to some phenomena seen in these * ‘Geology of the Henry Mountains,’ p. 80. t+ As Mr. Gilbert remarks, the action of the liquid lava was exactly that of the water in a hydrostatic press. See ‘Geology of the Henry Mountains,’ p. 95. 792 MR. W. BARLOW ON THE HORIZONTAL mountains which I attribute to horizontal movements such as I have above treated of. The very shape of the lava-deposits formed within the strata suggests that they have spread by their own weight and the weight of the superimposed crust. Circular or elliptical on plan, they are nearly flat in the middle, and curve down more and more rapidly towards the circumference*. Thus they have much the form taken by a drop of viscous fluid placed upon a level surface’. Dykes rise from the upper surfaces of the deposits. These are largest and most numerous about the centre, and the largest of them mostly radiate from the centre outward. Where numerous they reticulate f{. This predominance of the dykes in the axial regions of the lava masses, a well-known phenomenon in volcanic mountains, is possibly due to the crust experiencing most strain where most motion of the molten matter beneath takes place, the spread of the molten matter facilitating the spread and rupture of the crust resting upon it. Another phenomenon pointing in the same direction is that faults are present in some cases which are subordinate phenomena of the uplift. They are restricted to rts central portion, and never occur so far from the centre as the zone of maximum dip of the domed strata. The strata of the upper part of the arch are in this case divided into: a number of prismoid blocks, which stand at slightly different levels.. All or nearly all of the fault-planes are occupied by dykes of trachyte §. Further, the horizontal movement of some layers of strata on others is proved by the fact that in a number of instances the dykes are as even upon their upper surfaces as an artificial stone wall, the flat top of the dyke butting against an unbroken stratum of rock which bridges across it, and being parallel to the bedding of the enclosing strata. In one case a converse phenomenon is seen. A great dyke forms the crest of a ridge for half a mile, its base being _ buried in sandstone, and at the end of the ridge the strata are seen to be continuous beneath the dyke}. Then there is a fact which we may refer to the presence of joints or close fissures caused by small horizontal motions of the parts of the strata. The denudation has been far greater where the strata are uplifted to form the mountains than in the region around. Thus,. while from the base of the arch of one of the mountains 3500 feet of the Cretaceous and from 500 to 1500 feet of the Jura-Irias series: have been removed, from the summit of the arch more than 2500 feet: of the latter have disappeared. In cases where the lava deposits are so deep that the denudation has not laid them bare, the arched sedimentary rocks of the uplift have often been eroded down to * ‘Geology of the Henry Mountains,’ p. 55. t Ibid. pp. 20, 23. { Many mountain uplifts have much this form, e.g. the Uinta Mountains, the Kaibab Plateau, and the Black Hills of Dakota. See Geology of the Black Hills of Dakota,’ p. 207. § ‘Geology of the Henry Mountains,’ p. 23. | Zoid. pp. 28, 34. mi MOVEMENTS OF ROCKS, ETC, 793 ‘substantially the same level as that of the surrounding plain, the mountain originally formed having quite disappeared *. The source of additional jointing and fissuring which would account for the greater rate at which these uplifted rocks have been disintegrated is evidently to be found in the lateral strain and stretching to which over a long period they were subjected. Some increased weakening will also have been caused by the presence of precipices and steep slopes in the way before explained. If the production of fissures by horizontal movement, unattended by upheaval, has been as common an occurrence as the foregoing would lead us to conclude, it may, I think, be fairly questioned whether sufficient prominence has of late been given to the influence exerted by it in determining the directions taken by rivers and streams. The opening of a very narrow fissure across the bed of a river might suffice to initiate the complete diversion of the course of the water, and, in cases where no faulting or upheaval accompanied the fissuring, there would commonly be no evidence to betray the origin of the diversion. Unfilled fissures have often been produced concurrently with dykes in modern times, and must have been frequently produced in the past. And we have in some cases a correlation of the locality and direction of dykes and the direction of watercourses pointing to a common or connected origin. Moreover, I have suggested that the existence of elevated ground over plastic rock causes the spread of the latter to be more con- siderable on account of the greater weight pressing upon it, so that fissuring by this means will commonly have been more prevalent among mountains and elevated lands than elsewhere. And this would furnish an explanation of the well-known fact that gorges, ravines, and canadas are found in every high country, and also go far to account for the great number of cases of rivers intersecting elevated and isolated rocks. , In harmony with this explanation, we find that the examples of rivers whose courses are thus out of conformity with the features of the land-surface and also with the dip of the strata are most numerous in countries where dykes and other traces of the presence in the past of very plastic or fluid rock near the surface are found. Thus, in the country of the great canons in North America we have innumerable instances of want of conformity between the courses of considerable streams and the contour of the ground- surface and the dip of the stratat, and in the same district we have a recurrence over wide areas of similar and evidently related phenomena of faulting and contortion, which indisputably proves * «Geology of the Henry Mountains,’ pp. 25, 33, & 35. Tt In Scotland, for instance. { ‘Tertiary Hist. of the Grand Cafion District’ (C. E. Dutton), pp. 2, 49, 50, 73, 201, 203, 204, 220; and ‘Geology of the High Plateaus of Utah,’ pp. 17, 257. Report of the U.S. Geological and Geographical Survey of the Territories, Colorado, &e., 1876, pp. 52, 54; ‘ Geology of the Black Hills of Dakota,’ p. 216, 794 MR. W. BARLOW ON THE HORIZONTAL that large tracts of the earth’s crust have in this district experienced related movements, and points to a liquid or very plastic state of the underlying rocks at the time. The probability that separation by strain has in many cases initiated the diversion of rivers in the Western States has been recognized by some American geologists*. Other explanations of the want of conformity referred to appear — to me to involve very serious difficulties. Take the supposition that the Plateau-region has been elevated so slowly that the corrasion of the Colorado River has kept pace with it, and that, in this way, the position of this river has remained constant, while the ground- surface has been changed and new structural features created by the movement of the rocks. To this there is the following important objection. However slow the rate of elevation of an uplift, there must be some effect from the lessening of the gradients of the watercourses where they are approaching the uplift, and from the steepening of the gradients where they are leaving it, and con- sequently, in the case referred to, diminished erosion should be found on one side of the uplift and increased erosion on the other, and the modification of the bed and banks of the stream resulting from this distribution of force should be apparent. Now whatever uplift has taken place has, in the main, taken place without materially affecting the horizontality of the strata, consequently it is only where the river leaves the elevated tableland that any increase whatever in the fall of the river can be supposed to have been directly produced by the uplift, and the extreme erosion should, it would seem, if this were the explanation, be confined to this end of the river. The facts that the river has sunk its bed deep into the strata throughout the whole length of the elevated tract and that steep gradients are not at all confined to its lower end prove, I submit, that, whatever the explanation, it is not this. If when the uplift, which has raised the Plateau-region to its present altitude, began, the Colorado river was peacefully meandering along a nearly level surface of horizontal strata since cut away by denudation, it appears to me that any such elevation as that which has taken place must, however slowly it occurred, have diminished the rate of flow of the river and have converted it into a succession of sluggish pools, and finally have dammed it back and obliged it to take a new coursert. If, on the other hand, the course of the river was marked out by the opening of a fissure by horizontal strain, one can see how the weakening of the rocks bordering the precipices by the creeping movements to which I have called attention would pave the way for rapid erosion{. * Report Geological and Geographical Survey of Colorado, pe BS 105, 198, 201, 220, and 227; and Report Idaho and Wyoming, 1877, p Tt A very slight movement of the rocks is often sufficient to pe the course of ariver. It requires a movement of a few feet only to change the outlets of Lakes Michigan, Huron, and Superior from Illinois River to the St. Clair. t See ‘ Geology of the High Plateaus of Utah,’ p. 37. MOVEMENTS OF ROCKS, ETC. 795 In the same way I attribute to this weakening of the rocks by creep the formation of branch canons, the creeping movements working back into the rocks from every new precipice as it is formed*. Next, just a word as to the formation of faults. It appears to me that, as reverse faults are admittedly due to horizontal compression, so faults of “normal” hade should be attributed to horizontal extension. For if, when a fissure is formed in the way I have explained, the rock on one side of the fissure overhangs, there will, on account of the greater weight pressing on the plastic material beneath on this side, be a subsidence of the rock on this relatively to that on the other side of the fissure. The movement will generally go on until, by the shifting which takes place, the fissure is closed’, and, if the spreading or extension is continued for a long period of time, so as to allow the complete plasticity which all rocks ultimately manifest to come into play, [think most, if not all, of the peculiarities of this kind of faulting could be readily accounted for. A few words in conclusion with reference to the extent of that horizontal compression of the earth’s superficial crust which is seen to have been extensively associated with the elevation of mountain ranges, and which reveals itself by greater or lesser folds and con- tortions of the strata i. In making the familiar comparison between a bale of cloth folded and puckered by lateral pressure and crumpled, stratified, or lami- nated rocks, it has sometimes been overlooked that, while in the one case, the length of the cloth after it has been puckered is the same as when it lay flat, so that the extent of the compression can be easily estimated from the curves produced, this is not so in the case of folded rocks, as concurrently with the bending of the layers some amount of plastic thickening or thinning takes place. The evidence of this partial plasticity is found in differences in the thickness of contorted layers of strata, depending on the direction into which the lines of bedding have been forced. This is well shown in an interesting section figured by Sorby §. In weighing the evidence of thickening afforded by such a section, it should moreover be remembered that in the early stages of the deforming process, while the curving was inconsiderable, the con- torted layers must have suffered thickening throughout their entire length, and not only at the vertices of the curves, and further that this early stage must have been protracted owing to the resistance to the deformation being greater at first. I submit, then, that wherever folds or tiltings and displacements have been produced in stratified rocks by lateral pressure, very great thickening of the strata has taken place, particularly in the early stages of the disturbance, before the puckering became considerable ; * See ‘ Tertiary Hist. of the Grand Cafton District, p. 62. t The closing of the fissure will, no doubt, be accelerated by the spreading of the rock in which it occurs caused by gravitation. t See Dana’s ‘ Geology,’ 3rd edition, p. 785. § H. CO. Sorby, “On Origin of Slaty Cleavage,” Edin. New Phil. Journ. vol. ly. 1853, p. 139. 796 ON THE HORIZONTAL MOVEMENTS OF ROCKS, ETC. and, consequently, that the lateral compression has been very far more than the curving taken alone would seem to indicate; and ‘this especially applies to large folds. Again, as to the extent of the lateral compression of strata in cases where it is not associated with any contortion, but is revealed by the deformation of the contained fossils *, I would remark that for the deformation of a fossil organism to furnish a measure of the amount of thickening which the deposit containing it has undergone, the organism must at the time it was subjected to the strain have been as plastic as the deposit, a condition which, perhaps, will but seldom have been fulfilled in the case of organisms durable enough to insure their good preservation in the fossil state. That fossils do resist the deforming influence exerted by the thick- ening of the deposit containing them is evidenced by the well-known facts that thicker and harder shells are not found deformed where thinner shells, Algee and Trilobites, associated with them in the same formation, have suffered deformation f, and that sometimes particular organisms are found less distorted in beds of one kind than in beds of another at the same spot f. Again, where no contortion of the strata, or deformation of fossils, affords evidence of lateral compression, we frequently have an indica- tion of its occurrence in the simultaneous thinning of a series of different strata in the same direction, and that whether the conver- gence of the surfaces separating the strata is only slight or very great, as in the well-known fan-shaped structure often displayed in mountains. For I submit that for a series of superimposed deposits to be oreginally laid down all having their thickness increasing in the same direction, would seem to involve that during the whole period of their deposition the position of the shore-line continued nearly the same; and that, as this seems untenable, we must suppose that, generally, deposits thus related have been thickened up at one place, or thinned out at another, since their deposition. And the only agent we know of, adequate to produce this effect ona large scale, 1s lateral compression. The thinner as well as the thicker parts of the deposits will generally, it is manifest, have been thickened in the process. These conclusions appear to me to have some interest and import- ance, because the thickness of deposits is very generally regarded as furnishing a clue to the length of time which was taken to form them. If they are sound, we must, I think, conclude that most indurated and disturbed strata have suffered considerable thickening by lateral compression since their deposition. * See Dana’s ‘Geology,’ 3rd edition, p. 98. + “Report on Cleavage and Foliation,” John Phillips. Brit. Assoc. Rep. 1856, p. 386. + Sharpe, “On Slaty Cleavage,” Quart. Journ. Geol. Soe. vol. iii. 1847, p. 77. ON THE EOZOIC AND PALOZOIC ROCKS OF CANADA. 797 45. On the Kozorc and Patmozorc Rocks of the Attantic Coast of Canapa, in Comparison with those of Wustrrn Evrore and of the Intertor of Amurrca. By Sir J. Witt1am Dawson, K.C.M.G., LL.D., F.R.S., &. (Read May 23, 1888.) Sryce the year 1845 the author has contributed from time to time to the Journal of this Society more than forty papers on the geology of Nova Scotia, New Brunswick, and Prince Edward Island, in which frequent comparisons were made between the rocks and fossils of the Atlantic coast-region and those of the inland plateau of the North-American continent on the one hand, and those of Europe on the other *. Many additional details bearing on the more uncertain parts of these subjects have been accumulated in unpub- lished notes in recent years, while large additions to our information have resulted from the extension of the Geological Survey of Canada, under Logan and Selwyn and their assistants, to those provinces, and from the Geological Survey of Newfoundland under Murray and Howley 7, while new facts have been accumulating with reference to the continuation of the Atlantic rocks southward on the coast of the United States, and also with regard to the intermediate or “ inner marginal” series observed on the Lower St. Lawrence and thence southward. The time seems thus to have arrived when some further and useful comparisons may be made, as well as corrections and amplifications of previous statements ; and these seem to be the more necessary, inasmuch as it is evidently difficult for geologists who have not personally studied these districts to correlate with accuracy the geological features of the marginal belts of the two sides of the Atlantic. The subject is, however, so extensive that within the limits of this paper it will be necessary to confine attention to the most sa- lient points, and to state these as briefly as possible. I shall also confine the descriptive part to the rocks of the Atlantic border of North America, especially of Canada, and shall merely mention the parallel formations of other districts. It may be useful to explain that I shall use the term “ System ” for the larger divisions of the great geological ages, and “‘ Series ” for their most important subdivisions, and the term ‘‘ Group” in its ordinary sense as indicating a number of associated beds without reference to precise classificatory value. * TI find that, of forty-three papers on the Geology of Canada which I have contributed to the Society’s Journal, ten are on subjects connected with the Hozoic and older Palxozoic rocks, twenty-nine relate to the Devonian and Carboniferous, and four to the Mesozoic and Modern. t Though Newfoundland is not, politically, a portion of Canada, it is neces- sary to include its geology in any general survey of that of the Canadian coast. Q. J.G.S. No. 176. 3G 798 SIR J. W. DAWSON ON THE EOZOIC AND PALAOZOIC I. Toe LavrentiAN System. It is, I think, becoming more and more evident that in every part of the world the oldest rocks exposed are of the nature of ortho- clase-gneisses associated with various kinds of crystalline schists, and locally with quartzites and limestones. This statement applies with equal force to the Acadian Provinces of Canada and to west- ern Europe. In these districts, however, the old Laurentian sub- stratum is represented, not by great continuous areas, as in the interior of North America, but by rugged islets and ridges of erystalline rock, in most places so imperfectly exposed that their subdivisions can scarcely be made out, and that geologists may even be excused for doubting the stratified character of their rocks. It is only by comparing them with the magnificent series exposed in the country north of the St. Lawrence, and worked out so ably by Logan, that the more limited exposures of the Atlantic margins can be understood. In the Journal of this Society for February 1865 will be found a summary statement by Logan of the structure of this formation, which still holds good*. He there divides the Laurentian into two series, the - lower and the upper, the former largely composed of othoclase-gneiss, but with beds of limestone, quartzite, and micaceous and hornblendic schists in its upper parts ; the latter composed of similar gneisses and limestones, but with beds of gneissose anorthosite and lab- radorite, and great masses of coarsely cleavable labradorite and hypersthene. It is perhaps unfortunate that these last masses, many of them, no doubt, accidental and intrusive, so forcibly attracted the attention of Logan that he characterized the upper Laurentian as a labradorite series, whereas the true aqueous rocks of this series would afford better terms of comparison with other districts than merely igneous masses or beds. A similar objection, I think, applies in some degree to the name Norian, as more recently given by Hunt; and I have no doubt, from my own observations in the typical districts, that Logan’s division must stand, though perhaps it would be well to separate the lower gneiss from the remainder of his Lower Laurentian and to re- cognize a Lower, Middle, and Upper group, all of which are distinctly erystallinerockst. The upper member, as developed in the west,should, Ithink, includesome of the crystalline rocks which have been classed as. Huronian, and which seem to fill part of the gap between the latter and the Lower Laurentian in the regions further east t+. This view will in * “On the Hozoic and Paleozoic Rocks.” t The two principal members have been named respectively the Ottawa and Grenville series. The third, or upper member, in Logan’s typical district has been separated as the Norian series by Hunt; and by Selwyn (Reports Geol. Survey of Canada, 1879-80) is regarded as mainly composed of igneous rocks. In the maritime Provinces, as we shall see, only two members have been recog- nized. + Dr. Bigsby, “On Lake of the Woods,” Journal of Geol. Society, 1851-2; Dr. G. M. Dawson, Report on 49th Parallel, 1875; Mr. Lawson, Reports Geol. Survey of Canada, 1885. The latter has proposed the name “‘ Keewatin” for some of these rocks in the west. ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 799 any case afford better means of comparison with the Laurentian of other districts, and the occurrence of masses of binary granite and syenite in the Lower group and of labradorite in the Upper need not inter- fere with such comparisons, though it is to‘be observed that in the Upper member plagioclase felspars are much more abundant than in the Lower. Prof. Bonney has some very judicious remarks on this in his Anniversary Address before this Society in 1886. Whatever views may be entertained as to the origin of these old rocks, no one who has studied the typical districts of the Ottawa River can doubt for a moment that they are regularly bedded de- posits, and that in the middle Laurentian those conditions which in later periods have produced beds of limestone, sandstone, iron-ore, and even of coal, were already in operation on a gigantic scale*, At the same time it may be admitted that some areas of the lower gneiss may be cooled portions of an original igneous mass, and that many of the schistose rocks may be really bedded igneous materials. Turning now to the Atlantic coast, the greatest area of Lauren- tian rocks is that forming the nucleus of the Island of Newfoundland. In the northern part of that island the absence of the great crystal- line limestones would seem to indicate that the lower member of the series alone is represented. The same remark applies to the contin- uation of the formation in the south of the island, with the exception that indications of graphitic limestone and of magnetic iron-ore have been found in two places +. It is to be noted here that the great uplift in Pre-Cambrian times of the Laurentian nucleus of Newfoundland seems to have acted as an outwork to the formations to the westward, protecting the area of the Gulf of St. Lawrence from those thrusts from the eastward which have piled up in gigantic earth-waves the older formations of other parts of Eastern Canada and the Appalachian region. In con- sequence of this the area of the Gulf of St. Lawrence has throughout Paleozoic time remained undisturbed, and has conformed in its con- ditions of deposit rather to the internal plateau than to the maritime districts. In Cape Breton the isolated mass of St. Ann’s Mountain seems to be a representative of the Lower Laurentian of Newfoundland, and Mr. Fletcher’s observations render it probable that rocks of this kind exist in the northern extremity of the island. In Nova Scotia proper I have not been able to recognize any true Laurentian, the rocks attributed by some other observers to this age being, in my judgment, intrusive granite masses of much later date associated with altered rocks ft. In southern New Brunswick, however, the Laurentian reappears. As seen near St. John, the lower part consists of red and grey gneiss with chloritic gneiss and diorite. The occurrence of hydrated silicates * Q.J.G.S. vols. xxiii., xxv., xxxii., xxxv. In these papers I have set forth not merely the evidence for the organic character of Hozoon, but for that of the Laurentian limestones and graphites and phosphates in general. + Murray’s ‘ Geol. Survey of Newfoundland,’ 1881. + Supplement to Acadian Geology, 1878, p. 89. ” e2 800 SIR J. W. DAWSON ON THE EOZOIC AND PALZOZOIC in some parts of these old gneisses may be attributed to changes sub- sequent to their original formation. The upper member contains much limestone, with graphite and serpentine*, grey quartzites and diorite. This last series, which I hold to be really Laurentian, as it certainly underlies, and probably unconformably, the Huronian system, must belong to the upper member of the series. There is, indeed, nothing in its mineral character to exclude it from the Upper Laurentian as developed further west except the absence of certain igneous rocks. The resemblance of this interrupted belt of Laurentian along the Atlantic coast of America to that which extends southward from Scandinavia along the west of Europe is patent to every observer. The relation to the next succeeding formations is also identical, and on both sides of the Atlantic those great foldings which have bent and crumpled the old crystalline rocks seem to have occurred at the close of the Laurentian and before the next succeeding formation. Itis to be observed here, however, that in the case of the Laurentian these foldings pervaded the whole of what are now the Continental areas, as well as those marginal lines which were alone affected by . the succeeding movements. This general disturbance of the Lau- ~ rentian over the whole breadth of our continents, and this before any of the succeeding beds were deposited, impresses us with the conviction that the earth-movements immediately following the Laurentian were more extensive than those of any subsequent period, that they form a sufficient explanation of the very different character of the next succeeding formations, and that they produced wide areas of elevated rock which formed the nuclei of all later de- positions and movements. In comparing the Upper Laurentian of New Brunswick with the rocks which elsewhere, asin New Hampshire +, the district of St. Jerome, the Madoc district in Ontario, and the country west of Lake Superior, rest on the older Laurentian gneisses or on rocks regarded by some as primitive granites, one is obliged to admit either that this formation is of a somewhat protean character, or that, as Hunt maintains, there are several different formations of post-Laurentian crystalline rocks occurring in these different localities. In the Lewisian gneiss of Murchison we have in Britain an ade- quate representative of the Lower Laurentian, and in the two members of the Dimetian of Hicks a sufficient parallel to the middle and upper members of this great series {, which undoubtedly also appear in the isolated mass of the Malverns, and have been recognized by Barrois and Bonney in the ancient crystalline rocks of Brittany §. * In this limestone there occur fragments of Hozoon, and the graphite shows obscure fibrous structures. + Hitchcock’s Report. The beds called Montalban by Hitchcock occupy this osition. é t Hicks’s “Classification of Hozoic and Lower Palzozoic Rocks,” Popular Science Review, 1881. § Bonney, Quart. Journ. Geol. Soc. vol. xliii. ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 801 Il. Tur Horonran System. In the typical area of Lake Huron, as originally described by Logan and Murray *, this system rests unconformably on the Lower and Middle Laurentian, and presents a great contrast in point of mineral character to these formations. It is comparatively little disturbed, and is clastic rather than crystalline in character. ‘This point has been well insisted upon by Dr. Bonney and by Mr. Irving in recent papers. Further, its conglomerates contain pebbles of Laurentian rock in the same crystalline state in which these rocks are found at present. It consists chiefly of quartzites, conglomer- ates of different kinds, limestone, and slates, sometimes chloritic, with interbedded diorite. Without discussing those more or less erystalline rocks west of Lake Superior and in the Appalachian region which have been by Logan himself and later authors identi- fied with the Huronian, and which may, in part, belong to the interval between the Huronian and Laurentian or to the upper beds of the latter, or may even be later sediments in an altered state, we may attend at once to the beds which on the Atlantic coast suceeed the Laurentian. We may remark, however, that, associated with the Huronian at the west of Lake Superior and extending thence northwards to Hudson’s Bay and the Arctic sea, are the dark slates, sandstones, &c. constituting the Ainimiké series of Hunt. Whether these constitute an upper member of the Huronian or a distinct for- mation does not certainly appear. It is, however, certain that this formation is very widely distributed, especially in the north ¢. It is also to be observed that many of the bedded rocks of the Huronian are really of volcanic origin, being bedded volcanic ashes or muds in an altered state §. In Newfoundland the older slate-series of Jukes ||, which Murray originally called the intermediate series, but afterwards mapped as Huronian, consists, in ascending order, of quartzites with diorites and jaspery bands, slate-conglomerate, green, purple, and red slates, and dark-brown or blackish slates. In the upper part of this or the lower part of the next group are the worm-burrows known as Arenicolites spiralis and the uncertain fossils described by Billings as Aspidella. The lithological correspondence here between Newfoundland and Lake Huron is very close, and is increased by the fact that a series of red sandstones and con- glomerates, the Kewenian of the West and the upper Huronian or Signal-Hill beds of Jukes and Murray, overlie the typical Huronian in both districts J. * Geology of Canada, 1863. + Anniversary Address, 1886. Amer. Journ. of Science, 1887. ¢t G. M. Dawson, “‘ Notes on northern part of Dominion of Canada,” Geol. Survey, 1887, p. 8; Dr. R. Ball, “ Report on Hudson Bay, 1877 to 1885,” Geol. Survey of Canada. § Dawson, ‘ Canadian Naturalist,’ 1857; Nicholson, Quart. Journ. Geol. Soe. 1873; G. M. Dawson, Geol. Mag. 1875. || Report on Newfoundland, 1843. 4 Geology of Newfoundland, 1881. 802 SIR J. W. DAWSON ON THE EOZOIC AND PALZOZOIC Passing from Newfoundland to the coast of southern New Bruns- wick, we find in the ‘‘ Coldbrook ” and “ Coastal” series of Bailey a group corresponding essentially to that in Newfoundland, except perhaps in the fact that felsitic rocks occur toa larger extent in the lower part, and that the upper part presents not only conglomerates, ash-rocks, and amygdaloids, but also chloritic and hydro-miea schists. This upper part, distinguished as the ‘‘ Coastal Series,” is regarded by Prof. Bailey as distinct from the Huronian proper, and as either an upper member of that system or perhaps of later age, though pre-Cambrian *. As in Newfoundland, the typical Huronian of New Brunswick is overlain by reddish and purple conglomerates, sandstones, and shales, which are, however, here regarded as the base of the Cambrian 7. Matthew has recently found in them not only worm-burrows and fucoids, but a Linguloid shell. They appear, however, to underlie unconformably the lowest division of the Paradoxides-beds. With these rocks, whether of Lake Huron, Newfoundland, or New Brunswick, I have no hesitation in comparing the Pebidian of Wales, as well as certain portions of the older Malvern rocks and those of Charnwood Forest. Some of these groups I have seen on the ground, others are well known to me by suites of specimens. Similar rocks also succeed the Laurentian in Scandinavia and in other parts of Europe as well as in Africa and portions of Asia. Thus the Huronian type is very widely distributed, even if we take it in the restricted sense as originally used by Logan and, later, by Irving t, and leave out doubtful deposits which have been connected with it. The Huronian marks a period of igneous disturbance and coarse mechanical deposition succeeding to the Laurentian foldings. It is essentially a coastal or marginal deposit, and indicates that at the close of the Laurentian considerable areas of land had been elevated in the northern hemisphere. It was along the margins of this old Laurentian land that the Huronian was deposited, and its outcrops mark these margins, which in America before the rise of the Appa- lachians extended westward from the Atlantic coast along the southern shores of the Laurentian land. The conditions of deposit in Wales at the same period were evidently in general similar, though with local peculiarities. Two important questions arise from the above statements. The first relates to possible deep-sea deposits of this age, differing from the coarse marginal detritus and volcanic accumulations. These must have existed; but to what an extent are they known to us? The limestones associated with the Huronian probably belong to their margins; but they have so far afforded no fossils except ob- scure indications of sponge-spicules in the chert-nodules which they * Bailey, ‘Geology of New Brunswick,” Geol. Survey Report 1877-8; Ells, ‘ History of New-Brunswick Geology,’ 1887. t Geological Survey Reports, 1878. ¢{ Amer. Journal of Science, 1887. ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 803 contain *. I confess, however, that I am inclined to suspect that some of the beds known as Ainimiké and Taconian may prove to be of this character, as well as some of the disputed Huronian of the Appalachian region f. The second question relates to the extent to which conditions similar to those of the Huronian may have been repeated in subse- quent periods; and here it is evident that wherever on continental margins coarse aqueous rocks were being accumulated, in the Vicinity of igneous foci and mixed with their detritus, rocks litho- logically resembling the Huronian may have been deposited. This consideration imposes much caution as to the possible correlation of such deposits with the true Huronian on the ground of mineral character alone. In Nova Scotia and New Brunswick as well as in Great Britian there are rocks having in many respects the aspect of the Huronian which belong to Paleozoic times, and there is reason to believe that on the Pacific coast there are certain rocks of this kind of much later date. These, as has been shown by Dr. Selwyn and Dr. G. M. Dawson, are in great part bedded volcanic ash-rocks in an altered condition {. An important new light has recently been thrown on the supposed upper Huronian of Newfoundland by Mr. Matthew, who has found that in New Brunswick the conglomerate and red sandstone under- lying the Paradowides-beds are, as before stated, unconformable to these, and that, likethe Basal or Caerfai beds of Hicks in Wales, which somewhat resemble them in mineral character, they contain worm- tracks and a Linguloid shell as wellas remains of Alge. He there- fore regards these as basal Cambrian beds. This may also prove to be the position of the Newfoundland Signal-Hill rocks, and of the Kewenian series of the west. This basal series of New Brunswick is estimated at 1200 feet in thickness. If it be reckoned as the equivalent of the Caerfai, the lower members of the St. John group proper will be the equivalent of the Solva group, and the upper members will represent the Menevian §. Ina letter recently received from Mr. Irving, of the U. 8. Geological Survey, he informs me that *©an obscure Linguloid shell” has been found in the quartzite of south-western Minnesota, a formation which he regards as probably below the Kewenian, and possibly even Huronian. These facts render it possible that an upper Huronian series containing precursors of the Cambrian fauna may yet be recognized, or probably a new intermediate system to be designated by some other name ||. It will also be observed that, like the typical Huronian, such series, whether * T find such indications in the chert of the limestones on Georgian Bay. They are apparently simple acerate siliceous spicules, resembling those of some Cambrian sponges. + See, however, Dr. Sterry Hunt,‘‘ Elements of Primary Geology,” Geol. Mag., Noy. 1887, fer his classification of tue western rocks of these groups. + Report Geol. Survey of Canada, 1871-1885. § Matthew, ‘Canadian Record of Science,’ 1887. || Irving has proposed té call all the formations between the Laurentian and the base of the Cambrian “ Agnotozoic ;” but the term Huronian seems sufficient at present for this purpose. 804 SIR J. W. DAWSON ON THE EOZOIC AND PALOZOIC Huronian or Kewenian or intermediate, will be common to the coastal and interior regions, thus differing from the true Paradoaides- zone. Til. Tue Camprian System. For a long time the base of the Paleozoic, in the eyes of the geolo- gists of America, was the Potsdam Sandstone, which over great areas of Canada and the United States rests unconformably and directly on the Laurentian. The marginal areas of the continent have since afforded a great series parallel to the Cambrian of Wales and of Scandinavia. In southern Newfoundland the Huronian rocks, or the Signal- Hill red sandstones and conglomerates overlying them, are succeeded, according to Jukes and Murray, by a thick formation of sandstones and slates with a little limestone and conglomerate, and near the base of this the great Paradoxides Bennetw and other forms of like age are found. These are Lower Cambrian and obviously parallel with the beds holding the rich fauna of this age in New Brunswick, originally described by the late Prof. Hartt *, and more recently and more fully by Mr. Matthew. The strata holding these fossils in New- foundland have conglomerate, slate, and limestone below, and a great thickness of variously coloured slates above, overlain by sandstones and slate. Very similar beds constitute the lower Cambrian series of St. John, New Brunswick. I have already stated that there exists in southern New Bruns- wick a series of red, purple, and grey conglomerates and sandstones not unlike the Signal-Hill series, unconformable to the Huronian below and the Paradoazdes-beds above, and holding not only worm- tracks, but Linguloid shells. These are regarded as a basal Cambrian series, perhaps equivalent to the Caerfai group of Hicks, while above this are the equivalents of the Solva and Menevian groups of the same geologist, corresponding in mineral character and fossils so closely as to indicate portions of the same sea-bottom?. The Braintree slates in Massachusetts with their underlying conglomerates may be considered a continuation of the New Brunswick beds §. Above these in Newfoundland is a slender representation of the lower part of the Upper Cambrian, now called Middle Cambrian by _ some, and consisting of sandstones and flags, often micaceous, with Inngule. Similar beds cap the Lower Cambrian in southern New Brunswick. Mr. Fletcher, of the Canadian Survey, has found fossils indicating what is probably the same horizon in the slaty districts of southern Cape Breton. Mr. Matthew regards these series as covering the whole succession from the Caerfai group of Hicks to the Lingula- flags, and the two great zones A and B of Angelin in Sweden. * Acadian Geology, 1868. + Trans. Royal Society of Canada, 1885 to 1888. ¢ Matthew, ‘Canadian Record of Science,’ 1888. § Crosby, ‘Boston Society of Nat. History,’ 1884. ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 805 There is, however, no certain evidence that any of these beds reach so high as the horizon of the Potsdam *. These rocks of Newfoundland and the Acadian Provinces, con- stituting what I formerly named the “ Acadian group” +, are in their lithological characters and fossil remains precise equivalents of the Longmynd, Menevian, and Lower Lingula-flag groups of England. In this connexion an important group of rocks is the Atlantic coast series, or gold series of Nova Scotia, described by me in this Society’s Journal as far back as 1850 +, and subsequently in ‘ Acadian Geology ’ and supplements thereto§. This great series, extending for more than 200 miles along the Atlantic coast of Nova Scotia, consists of dark-coloured quartzite and slate in massive bands, the former predominating below and the latter above, and the whole attaining to a thickness of perhaps 10,000 feet. In its western extension it appears to rest on rocks of Huronian aspect, and where it is invaded by granitic masses and veins (Devonian in age) it assumes the con- dition of mica-schist and imperfect gneiss, being then similar in mineral character to the rocks elsewhere known as Montalban. It has unfortunately afforded no well-characterized fossils. The mark- ings called Kophyton || and certain radiating bodies (Astropolithon) {J found in it are, however, similar to those occurring elsewhere in Lower Cambrian rocks. Murray was disposed to regard this forma- tion as corresponding to his Huronian in Newfoundland ; but it does not agree with this either in mineral character or in fossils, and is perhaps rather to be regarded as a great development of the lowest member of the Cambrian, an exaggerated equivalent of the Harlech Grits and Llanberris Slates. In this case, however, it may be expected that it will yet afford true Cambrian fossils. In Western Europe, as Hicks has shown, great movements of depression must have occurred in this period, and we have evidence of asimilar character in America. If we roughly divide the Cambrian system into three great series, characterized respectively by the pre- valence of the large Trilobites of the genera Paradowides, Olenellus, and Drkelocephalus, we shall find that the former, the true Lower Cambrian, is unknown over all the great continental plateau of America **. Itisstrictly a marginal deposit formed at a time when there was probably a great continent west of the then infant Ap- palachians. But the second, or Olenellus-group, slenderly represented on the coast, appears in force immediately within the great Lauren- tian axis of Newfoundland 77. It is known in the valley of the St. Lawrence by the great masses of limestone full of fragments of * Fletcher, ‘Report Geol. Survey of Canada’; Matthew, Trans, Roy. Soc. Can. 1886; Canadian Record of Science, 1887. t Acadian Geology, 1868. t Quart. Journ. Geol. Soe. vol. vi. § 1868 and 1878. || Selwyn, Report Geol. Survey. € Acadian Geology, Supplement, p. 82. ** Walcott apparently places the lower portion of the Wahsatch section in Utah in the Lower Cambrian ; but this may belong to a western marginal area. tt Murray’s ‘ Newfoundland’; Billings’s ‘ Paleozoic Fossils.’ 806 SIR J. W. DAWSON ON THE EOZOIC AND PALZOZOIC Olenellus, Solenopleura, Hyolithes &c. in the conglomerates of the Quebec group*, and it also appears in the Georgia series of Vermont T, nd, according to Walcott, as far west as Nevada and Utah{. On the other hand the upper members of the Cambrian, the Dzkeloce- phalus-group or Potsdam Sandstone, is apparently altogether absent n the Acadian provinces, which at that time must have been under ocean-depths in which deposits of a very different kind would be produced, or elevated into land, perhaps the border of an Atlantic island now mostly submerged. It seems doubtful if any good equiy- alent of the Potsdam exists in England or Wales. It is otherwise, however, with the next succeeding formation, that passage-serles between the Cambrian and Ordovician known in Wales as the Tremadoc. This, in America, takes a more inland position, and becomes an interior or submarginal formation connected with the Quebec group to be mentioned in the sequel. At Matane and Cape Rosier, as noted by me in 1883 §, and as Lapworth has more fully proved in 1886]||, we have a true Tremadoc filled with Dic- tyonema sociale and containing also fragments of characteristic Trilobites. Further inland, on the main American plateau, these beds are not found, but are represented by the peculiar ‘“ Calciferous ” formation, a dolomite formed apparently in an inland sea and haying a characteristic fauna of its own. A very remarkable and exceptional feature in British geology is the appearance in the sandstone and limestone of the Durness series of Scotland of a group of fossils long ago recognized by Salter as of the interior American type 4. In other words there existed in Scotland, within the shelter of the old Laurentian and Hurontan ridges, an area which sustained a fauna similar to that of the internal plateau of America, and which, so far as known, did not exist in Wales or on the American coast. This curious case of apparent isola- tion we might better understand did we know the exact geographical arrangements of the period. One consideration bearing on it is the probability that the Trilobitic and Graptolitic faunas of the coast mainly belonged to cold northern currents, while the Plateau-faunas, richer in Cephalopods, Gasteropods, and Corals, belonged to the superficial warm currents passing over shallow plateaus, or to the tepid waters accumulated in closed basins. This is, I think, quite manifestly the case with the very dissimilar marginal and continental faunas to be noticed under the next heading. Salter seemed to sup- pose that the occurrence of these fossils in Scotland, and not to the south, indicated a climatal difference. In this he was justified; but the character of the climate was probably different from that which he imagined. * At Metis, St. Simon, &e. t Emmons’s ‘ American Geology ; Billings’s ‘ Paleozoic Fossils.’ { Bulletin U. S. Survey. § Report Peter Redpath Museum, No. ii. Richardson’s observations at Matane. || Transactions Royal Society of Canada. *| Quart. Journ. Geol. Soc. vol. xv. These rocks are also recognized by Geikie in Skye (Quart. Journ. Geol. Soc., Feb. 1888). ROCKS OF THR ATLANTIC COAST OF CANADA, ETC. 807 Before leaving the Cambrian, it may be well to state that Mr. Matthew informs me that he hopes to make out in the St. John series the equivalents of all of the subdivisions of the Paradoaides-zone established by Linnarsson in Sweden, so that there would seem to be a correspondence even in the minor details of the deposits on the opposite sides of the Atlantic *. This, as we shall see, also appears to Prof. Lapworth to hold in the case of the Graptolitic fauna of the Upper Cambrian and Ordovician on the two Atlantic margins. IV. Tuer Orpovicran SYSTEM. With the incoming of this new age a more marked distinction occurs in America between the marginal and plateau-deposits. I have already referred to this in the Calciferous ; but it is more dis- tinct as between the marginal and submarginal areas and those inland, in the period on which we now enter. In Newfoundland, Murray aud Howley have described large areas of Quebec-group rocks in the west and north of the island which seem to be continuations of the submarginal area of the Lower St. Lawrence. There is also one limited exposure of Trenton Limestone on the west coast, and belonging to the area of the Gulf of St. Lawrence, the peculiar conditions of which I have already mentioned. In Nova Scotia we have as yet uo representatives of the Ordovician system except slates associated with igneous rocks, resembling in mineral character the Borrowdale series of the North of England, and destitute of fossils. In northern New Brunswick we find a belt of slaty beds representing the Quebec group of Logan, which is the characteristic form of the submarginal development of this system occupying the St. Lawrence valley. This group, resembling in many respects the Arenig of England, and consisting principally of slates, sandstones, and conglomerates, constitutes the eastern representative of the great Upper Calciferous and Chazy Limestones widely spread over the internal plateau, and probably of part of the Trenton as well. The origin of this formation and its true relations to the interior plateau-deposits were early defined by Logan, who regarded the Quebec group as an Atlantic deposit thrown down in the open sea along the margin of the old Laurentian plateau, while thinner and differently constituted beds were being formed in the shallower and warmer waters of the plateau itself. It was further found and illus- trated by Logan that in the great earth-movements which closed the Ordovician period these marginal and submarginal deposits had been erushed and folded against the old Laurentian border, and even, ‘in places, pushed over the inland formations by reversed faults, while the latter remained comparatively undisturbed. These peculiar arrangements, which extend southward along the Appalachian ranges, led to much discussion among the geologists of the New York Survey, and to that ‘“ Taconic” controversy which is still scarcely terminated. So far as our present subject is concerned, it is sufficient to * Amer. Journ. of Science, May 1887. 808 SIR J. W. DAWSON ON THE EOZOIC AND PALZOZOIC observe that the Quebec group is not strictly an outer marginal for- mation, but rather submarginal, and belongs to a period when the principal area of coastal deposition of sediment from the north was: inland of the Acadian provinces, or between them and the main American plateau, and separated from the outer ocean by a belt of active volcanos. Its conditions of deposit and characteristic fossils may fairly be compared with those of the Skiddaw and Arenig of England *. The Ordovician series of Shropshire extending upward. from the Stiper Stones to the Caradoc is also a counterpart of the Quebec group f. Perhaps no term of comparison for these beds is more satisfactory than that of the Graptolitic faunat. This has been studied in the case of the Canadian series with great care by Hall, whose monograph on the Graptolites of Canada is a classical work, and subsequent observations have ascertained several divisions between the Matane series of the Lower St. Lawrence and the Utica§. The whole subject has, however, recently been reviewed by Lapworth ||, in connexion with material placed in his hands by the Director of the Geological Survey of Canada, and his results are of the greatest interest as indicating the precise correspondence in those truly pelagic forms on the two sides of the Atlantic. They may be summed up as follows, in ascending order :— Qursec Group oF Lower St. LAWRENCE. 1. Matane Beds 9 .—Grey, red and black shales, sandstones and limestone, equivalent to Lower Calciferous of inland America and Tremadoc of England. Characterized by Dictyonema sociale, Bryo- graptus, Clonograptus, &e. 2. Levis Beds.—Dark shales, with sandstones and limestone- conglomerates. Limestone-bands and dolomite. Characterized by Phyllograptus, Tetragraptus, Didymograptus, &c. Remains of siliceous sponges also occur in some places**, This corresponds te the Chazy of inland America and the Arenig or Skiddaw of England. 3. Marsouin Beds.—Shales, limestones, dolomites, and sandstone, with Canograptus, Diplograptus, &c. Equivalent to the Trenton formation of interior America, including the Normanskill Shales of Hall, and to the Llandeilo formation of England. 4, Utica Series.—Soft shales, often highly bituminous or carbon— aceous, with Leptograptus, Diplograptus, &e. This is the Utica-Slate formation of inland America, and corresponds to the Hartfell and Caradoc group of England. * Hicks, ‘ Classification of Lower Paleozoic Rocks,’ 1881. Tt Lapworth, Geol. Magazine, 1887. + Mr. A. M. Ami, F.G.S., of the Geological Survey of Canada, has devoted much labour to these fossils. 2 § Report Redpath Museum, 1883. Paper by Mr. H. M. Ami, ‘ Ottawa Field lub,’ &e. || Transactions Royal Society of Canada, 1886. “| Cape Rosier Zone of Lapworth. ** Dawson and Hinde, Canadian Record of Science, 1888; also ‘“‘ Redpath Museum Notes,” 1888. ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 809 It will be observed here that the Graptolitic faunas referred to by Lapworth extend from the Tremadoc to the Caradoc inclusive ; but the Quebec group proper may be regarded as limited by these groups above and below. It is also to be observed that the Quebee group conditions of shale- and sandstone-deposit with cold-water animal species seem, in the later Trenton and Utica periods, to have become prevalent over the interior plateau as well as the marginal area. This appears not only from the wide extension of the Grapto- litic fauna over all the plateau west of the Appalachians in this later Ordovician time, but from the occurrence of these fossils in the extreme west. Graptolites of this age are reported by White in Nevada *, and have recently been found by M‘Connell and identified by Lapworth in the Wapta Pass in the Rocky Mountains of Canada ft. Thus, what we have regarded as marginal and submarginal con- ditions may in the later Ordovician have prevailed from the Atlantic to the Pacific. This was undoubtedly a consequence of the gradual Subsidence going on in the Ordovician age. It was naturally fol- lowed by the settlement of the ocean-bed, which raised again the continental area and folded the marginal and submarginal Ordovician rocks on both sides of the Atlantic. I may add that the above views correspond closely with those I haye held for many years, as the result of much study of these rocks in my summer vacations on the Lower St. Lawrence, and which are thus expressed in a paper published in 1883 { :— “There seems reason to believe from Mr. Richardson’s recent observations that Graptolitic zones reaching from the Lower Tre- madoc to the Upper Llandeilo may be discriminated in the great mass of sediments known as the ‘ Quebec Group,’ which the writer has long believed, on the evidence of the fossils he has himself observed, to represent a lapse of geological time extending from the base of the Potsdam to the Chazy limestone.” Prof. Lapworth’s recent memoir extends the range of this comparison as far upward as the Trenton and even the Utica. One feature of the Quebec Series is especially characteristic and American; this is the great limestone-conglomerates, which form conspicuous features in its middle portion. These conglomerates, which are very irregular in their distribution, and swell out rapidly to great thickness, degenerating as rapidly to mere sandstones, are remarkable for the quantity of boulders and pebbles of limestone which they contain, and which often afford Cambrian fossils, though in other cases they appear to belong to the limestone of the lower part of the Quebec group itself. The only means of explaining these conglomerates seems to be the action of the coast ice, which at this period appears to have been as energetic on the American shores as at the present day, and seems to have had great reefs of limestone, probably in the area of the Gulf of St. Lawrence, to act * Report on the 100th Meridian, vol. iv. t ‘“‘Report on Rocky Mountains,” Geol. Sury, of Canada, 1887. ¢ Report on Peter Redpath Museum. 810 SIR J. W. DAWSON ON THE EOZOIC AND PALZOZOIC upon and to remove in large slabs and boulders, piling these up on banks, to constitute masses of conglomerate. This would bespeak a cold ice-laden sea as that in which the Graptolites lived, and it may account for the survival in these areas of old Trilobitic genera which were not represented in the warmer waters of the continental plateau. This circumstance has perhaps some connexion with the greater apparent survival of these in America as compared with Europe, though I suspect that the observed appearances depend in part upon collectors attributing species belonging to fragments of older limestones to the Quebec group itself. The importance of the Quebec group of Logan is thus vindicated, as representing widely spread local conditions and great lapse of geological time ; and the prescient view which he entertained of it may be indicated by the following extract from a note appended by him to Murray’s Report on Newfoundland in 1865 :— “The sediments which in the first part of the Silurian period were deposited in the ocean surrounding the Laurentian and Huronian nucleus of the present American continent, appear to have differed considerably in different areas. Oscillations in this ancient land permitted to be spread over its surface, when at times submerged, that series of apparently conformable deposits which constitute the New York system, ranging from the Potsdam to the Hudson River formation. But between the Potsdam and Chazy periods, a sudden continental elevation, and subsequent gradual subsidence, allowed the accumulation of a great series of intermediate deposits, which are displayed in the Green Mountains on one side of the ancient nucleus, and in the metalliferous rocks of Lake Superior on the other, but which are necessarily absent in the intermediate region of New York and central Canada. “‘ At an early date in the Silurian period, a great dislocation commenced along the south-eastern line of the ancient gneissic continent, which gave rise to the division that now forms the western and eastern basins. The western basin includes those strata which extended over the surface of the submerged continent, together with the Pre-Chazy rocks of Lake Superior, while the Lower Silurian rocks of the eastern basin present only the Pre-Chazy formations, unconformably overlaid, in parts, by Upper Silurian and Devonian rocks. The group between the Potsdam and Chazy, in the eastern basin, has been separated into three divisions, but these subdivisions. have not yet been defined in the western basin. In the western basin the measures are comparatively flat and undisturbed ; while in the eastern they are thrown into innumerable undulations, a vast majority of which present anticlinal forms overturned on the north- western side. The general sinuous north-east and south-west axis of these undulations is parallel with the great dislocation of the St.. Lawrence, and the undulations themselves are a part of those belonging to the Appalachain chain of mountains. It is in the western basin that we must look for the more regular succession of the Silurian rocks, from the time of the Chazy, and in the eastern, including Newfoundland, for that of those anterior to it.” ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 811 Of Ordovician rocks other than the Quebec group and nearer to the Atlantic margin, perhaps the best example is that of the area in Central and Western New Brunswick described by Prof. Bailey*. This consists, in ascending order, of (1) gneiss and mica-schist with chloritic and hornblendic schists, (2) grey and purplish micaceous sandstones and slates with limestone and conglomerate and felspathic slates, (3) black graphitic and pyritous slates, (4) schistose felspathic rocks and conglomerates, (5) amygdaloid and felsite with sandstone and slate, (6) felsites capped with sandstones and slates, often chloritic. These remarkable rocks, which are of great thickness and haye evidently experienced much metamorphism, have been found at one locality to contain fossils of Trenton age equivalent to Bala and Llandeilo. Similar rocks come out from beneath Silurian beds in various parts of the hilly districts of Nova Scotiat. They resemble the Cumberland Ordovician more nearly than other British developments of these rocks. In the continuation of these beds in Northern New Brunswick Graptolites were discovered some years ago by Mr. Robb and Dr. Ells, of the Canadian Geological Survey, and are believed to be of Upper Ordovician age. V. Tue Srrvurtan System. In the inland plateau of North America this period begins with shallow-water conditions passing into the great and long-continued depression marked by the Niagara Limestone. There is then a second elevation, that of the Salina, succeeded by the very widely distri- buted Helderberg Limestones. There are thus two depressions sepa- rated by an intervening elevation. In Newfoundland the Silurian rocks occur in a narrow trough extending through the centre of the island, and, so far as can be ascertained from the Reports of the Survey of Newfoundland, are not dissimilar from the exposures in Nova Scotia. In the latter province the great limestones are absent or repre- sented by comparatively insignificant and impure bands. Shales with some sandy beds (Lower Arisaig beds of previous papers) represent the Clinton and contain Graptolithus clintonensis ; coarse impure limestone and shale (New Canaan beds of previous papers) correspond to the Niagara, holding characteristic corals of this age, and shaly beds with thin layers of limestone (Upper Arisaig of pre- vious papers) represent the Helderberg. In Nova Scotia these occur in the New Canaan, Arisaig, and Pictou districts, and their characters correspond to those seen in Newfoundland, New Bruns- wick, and Maine. In the Cobequid Mountains of Nova Scotia, however, and in New Brunswick, these beds, especially in their upper part, show great contemporaneous emissions of igneous rock. These are partly felsitic and partly doleritic and amygdaloidal. They correspond in age with those isolated igneous masses of the * Report Geological Survey of Canada, 1884-5. Tt Quart. Journ. Geol. Soc. 1850. ‘ Acadian Geology ’ and Supplement. $12 SIR J. W. DAWSON ON THE EOZOIC AND PALZOZOIC plain of the St. Lawrence to which the Montreal and Belceil Moun- — tains belong. In proceeding to the west and north the Helderberg Limestones appear in great force at Cape Bon Ami in Northern New Brunswick, where they are rich in fossils and associated with beds of trap. Both limestones are largely developed in Bonaventure and Gaspé, and the lower member in the Island of Anticosti, so that here as in previous periods the area of the Gulf of St. Lawrence corresponds with the interior plateau rather than with the coastal region. In some respects, indeed, this area presents an exaggeration of the interior conditions, since in Anticosti there is apparently a gradual passage from the limestones of the Hudson-river group to those of the Clinton, without the intervention of sandstones similar to the Oneida and Medina of New York and Ontario. In so far as I am aware there is also an absence of beds representing that condition of deserts and salt lagoons represented by the Salina or Onondago salt- group. In this last respect, as in so many others, the conditions of the eastern districts of America conform to those of Europe, and not to those of the interior plateau of America. In America as in England the Silurian of the maritime districts is unconformable to the Ordovician, though this does not hold in Anti- costi or in the inland region. Lithologically the English Silurian is more perfect than that of the East Coast of America, as containing, in the Wenlock Limestone, a better representative of the Niagara formation. The unequal cha- racter of this limestone, however, and its thinning out toward. the south-west, bring the series into harmony with that in Nova Scotia. The Ludlow rocks are perfect representatives of the Upper Arisaig series of Nova Scotia, and the fossils are remarkably similar, much more so than in the case of the Arisaig and the inland Helderberg in any locality known to me*. In England the trees which I have named Nematodendree appear first in the Denbighshire Sandstone at the base of the Silurian}. In America they appear in the Helderberg series. Placoganoid fishes have recently been recognized in the Silurian in New Bruns- wick +. The eurite and tufaceous rocks of the Silurian of the West of Ireland appear to be the principal British representatives of the abundant rocks of volcanic origin associated with the Upper Silurian in Nova Scotia and New Brunswick §. In summing up the Eozoic and older Paleozoic rocks of the Mari- time Provinces I may reproduce here, with some slight additions, the table given in the Supplement to ‘ Acadian Geology,’ 1878. * Acadian Geology and Supplements. t Hicks, Quart. Journ. Geol. Soc. vols. xxxvii. and xxxvill.; Dawson, ibid. +t Matthew, ‘Canadian Record of Science,’ 1886. § Murchison, ‘ Siluria.’ ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 813 Eneanp, &c. Nova Scorra anp New Brunswick. Silurian. Ludlow, Wenlock and Llandovery, Upper Arisaig Series, Nova Scotia ; or Mayhill. Mascarene Series, New Brunswick ; Lower Arisaig, New Canaan and Wentworth beds of Nova Scotia; and Restigouche series, New Brunswick. Ordovician. Caradoc and Bala, with Snowdon Upper Cobequid Series, slates, felsites and ash-beds, Coniston and | felsites, quartzites, and greenstones. Knock Series. Ordovician of Western and Central New Brunswick. Great felsite and trap-ash Series Lower Cobequid Series, felsites, of Borrowdale (Ward). porphyrites, agglomerates, and mas- sive syenite of Cobequids, Pictou, and Cape Breton ? * Middle Graptolitic or Levis Series of Quebec and North New Brunswick, part of Cape Breton Series ? Lower Llandeilo flags and shales, Arenig Series, Skiddaw slates, &c. Cambrian. Tremadoc slates and Lingula-flags. Matane or Cape Rosier Graptolitie beds. Miré and St. Andrew’s Channel Series in Cape Breton ? Menevian and Longmynd Series, | Acadian Series of St. John, New Harlech grits, and Llanberis slates. Brunswick. Quartzite and slate of Atlantic coast of Nova Scotia. Caerfai Group of Hicks. Basal Cambrian of Southern New Brunswick. Huroman. Pebidian Series (Hicks), containing Huronian felsites, chloritic and felsite, chlorite-schist, and serpentine. | epidotic rocks of Southern New Brunswick, Yarmouth, and of Cape Breton in part. Laurentian. Older gneisses of Scotland and of Gneiss, quartzite and limestone of Scandinavia, Dimetian ? St. John, Portland Group, gneiss of St. Anne’s Mountain. VI. Tum Ertan, ok Devonran System. This formation, most largely and completely represented in the great ‘‘ Erie Division ” of the Geological Survey of New York, which occupies an immense area in the district around the lake from which it is named, and attains therein its maximum thickness and develop- ment, appears on the eastern coast entirely in the form of sandstones and shales, which may be compared with those of the Old Red Sand- stone of Scotland and England. They differ entirely in mineral character from the great limestone- and shale-deposits of the interior of America, where, in the Province of Ontario, the Corniferous Lime- * It seems impossible at present to separate these perfectly from the Huronian, in some localites at least. Q.J.G.S. No. 176. onan 814 SIR J. W. DAWSON ON THE EOZOIC AND PALZOZOIC stone is perhaps the richest of all the paleeozoic limestones in fossil corals, and indicates a long continuance of truly marine conditions. These beds abound in fossil plants and, locally, in remains of fishes, and both the fishes and the plants are generically similar to those of Britain, and divisible into two series, representing the lower and the upper members respectively. The beds do not appear, however, to be lake-deposits but, rather, estuarine and littoral. They have been fully described in the papers referred to below *. In the Baie de Chaleur, for example, the lowest series is charac- terized by Psilophyton and Nematophyton, and by fishes of the genera Cephalaspis, Coccosteus, Ctenacanthus, and Homacanthust. The upper division is characterized by ferns of the genera Archeopteris and Platyphyllum, and by fishes of the genera Pterichthys, Dupla- canthus, Phaneropleuron, Glyptolepis, Cheirolepis, and a new genus named by Whiteaves Husthenopteront. The only truly marine portion of the system in the Maritime Province is the lower part, corresponding to the Oriskany of the interior, and this may perhaps be regarded as an equivalent of the Downton Sandstones of England. The greatest granitic intrusions of Nova Scotia belong to the close of the Devonian, as do many granitic masses in New Brunswick and Quebec. These are the equivalents of the Devonian and Cornish granites, though perhaps a little earlier in date, and are also repre- sented by the felsites of the Scottish Devonian. The remarkably rich flora of the Erian of the east of Canada was first made known in the Journal of this Society, and still holds its position as probably the most copious known in this age, though I have been obliged to withdraw two of its species, Selaginates formosus and Kguisetites Wrightianus, as probably Crustacean, and the genus Dictyophyton as certainly belonging to sponges and not vegetable §. VII. Tae Carzpontrerous System, &e. The Carboniferous formations of Nova Scotia have been described by the writer in a number of papers in the Journal of this Society]. Like the Carboniferous of Britain, these rocks present many local diversities. Their subdivisions are :— 1. A lower series corresponding to the Tuedian of the North of England and Calciferous of Scotland both in mineral character and fossils (the Horton Series of my later papers) 4. 2. A Carboniferous Limestone, associated, however, with gypsum, and marly and red sandstones, but having fossil remains for the most * Quart. Journ. Geol. Soc. vols. xv. and xviii. Tt Dawson’s Report on Erian Plants. Whiteaves, Trans. Roy. Soc. Can. vol. iv. “On Devonian Fishes.” t Lbid. § Quart. Journ. Geol. Soc. vols. xv., xviii., Xxvii., XxiX., xxxvi., xxxvili. The Devonian Flora of Scotland and that of Belgium, as described by Créspin, and exhibited in the Brussels Museum, are closely allied to that of Eastern Canada. || Quart. Journ. Geol. Soc. vols. i., ii., v., ix., X.,. Xi., XV-, XIX., xxil., xxix., XXX 4 Acadian Geology, 3rd edition. ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 815 part specifically identical with those of England (Windsor Series of recent papers). 3. A Millstone-grit series consisting of coarse sandstones and shales with conglomerate, mostly of red colours. 4, The Main or Productive Coal-measures, precisely similar in character to those of Britain. Of 135 species of fossil plants which I have catalogued from these beds more than one half are specifically identical with those of England. ‘The animal fossils of these beds, Batrachians, Fishes, Crustaceans, and Mollusks, are also akin to those of England. In the class of Batrachians a still more close approxi- mation appears in those obtained by Fritzsch in the Upper Car- boniferous of Bohemia. 5. A Permo-Carboniferous series, perhaps corresponding in age to the Lower Permian of England, and consisting largely of Red Sand- stones with species of plants characteristic in Europe of the Lower Permian, but including no limestones. The conditions of the Carboniferous are on the whole similar throughout North America, except in the extreme West and locally in the Appalachian region: but in Nova Scotia, Newfoundland, and New Brunswick they are more nearly allied to the British type, except in the abundance of red marls and gypsum in the Lower part. Interstratified trappean rocks, similar to those in Scotland and England, occur in Nova Scotia and New Brunswick, especially in the Lower Carboniferous. The details of the Carboniferous and Permian of Nova Scotia and Prince Edward Island are so fully given in the papers referred to in the notes, that the above general mention will be sufficient here. One fact of general application which is admirably illustrated in the Carboniferous of Nova Scotia is the extreme sensitiveness of the earth’s crust to unequal pressure. The Coal-formation of the Cum- berland district, 5000 feet in thickness, and consisting wholly of beds which must have been deposited almost exactly at the sea-level, shows that for every inch of sediment or of vegetable matter there must have been a corresponding depression of the crust. This accurate correspondence of sedimentation with subsidence has long appeared to me one of the most striking facts in geological dynamics. The Triassic Red Sandstone of Nova Scotia and Prince Edward Island and the associated Traps closely resemble the same for- mations in England. Like them they contain no important marine limestones, and their fossils are limited thus far to a single Dino- saurian reptile and a few fossil plants. In these it is far inferior to deposits of the same age further to the south on the Atlantic coast of the United States. In America, as in Europe, the Triassic flora and land- and freshwater-faunas seem to have been of southern origin. The maritime region of Eastern Canada is remarkable for its deficiency of Mesozoic rocks newer than the Trias. If there are such deposits, they must be, like the Cretaceous rocks believed to exist further south on George’s Banks, still under the sea. It is only on Greenland and the Arctic Islands that we find beds ranging from 3H2 816 SIR J. W. DAWSON ON THE EOZOIC AND PALHOZOTIC the Lias to the Eocene, and these belong rather to the Arctic basin than to that of the Atlantic*. In this respect the maritime region of Canada differs materially from that of Europe, though it is note- worthy that the extreme coastal region of Great Britain to the west is also somewhat deficient in such rocks. The question of Paleozoic climates in the northern hemisphere has some bearings on the subjects discussed in this paper, and is well illustrated by a map of the Arctic districts of Canada recently issued by the Geological Survey t. From this it appears that there are no indications of a warm climate in the Arctic basin up to the close of the Cambrian. The later Ordovician and the Silurian were, however, signalized by the deposition in the Arctic seas of thick and extensive organic limestones, holding fossils comparable with those of the temperate regions at the same time. The Lower Erian may perhaps indicate a short relapse to cold; but in the Upper Erian and Lower Carboniferous we have warm seas tenanted by marine animals and a rich land-vegetation appearing both in the Arctic Islands of Canada and in Spitzbergen. The Upper Coal-formation and the Permian and Trias indicate a return of cold, and the temperature seems to increase in the Jurassic, attaining its maximum in the later Cretaceous and Eocene, and gradually diminishing to the glacial age, between which and the modern there seems to have been a warm period of short duration, evidenced in the deposition of mam- moth bones, &e., on the Arctic coasts. The cycles of cold and warm climate thus indicated in the Arctic region have. I think, an important bearing on the succession of life further south, at least in Eastern America, and their correlation with the climatal changes in Europe would be a subject of much interest, on which, however, I do not feel in a position to speak positively; but I imagine that the warm and cold periods will be found to correspond with those of the Arctic basin and of America. The general sketch above given is sufficient to show that in the rocks from the Laurentian to the Trias inclusive we have on the two sides of the Atlantic a continuous parallelism in the following points :— 1. In mineral character and order of succession of aqueous deposits. 2. In the occurrence of great earth-movements of elevation, de- pression, and plication, at corresponding times. 3. In the ejection of like kinds of igneous rocks in connexion with like members of the aqueous series. 4, In the order of introduction and extinction of animals and plants. 5. In the specific identity of animals and plants in corresponding formations. All this, I think, points to an actual contemporaneity of the suc- cessive changes on the two sides of the Atlantic basin, and to a special correspondence of the formations of the respective marginal * For references see ‘Notes on Geological Map of Northern Canada’ by Dr. G. M. Dawson. t ‘Geology of Northern Canada,’ Dr. G. M. Dawson, 1887. ROCKS OF THE ATLANTIC COAST OF CANADA, ETC. 817 areas as contrasted with those of the continental plateaus. It also indicates a persistence, on the whole, of the oceanic character of the Atlantic depression. Lastly it shows the necessity in any system of geological classifi- cation of distinguishing the continental plateaus, the lines of great foldings and of igneous action, and the ancient ocean-margins from each other, and of adapting our arrangements and nomenclature to their actual diversity. In order to do this, while adopting common designations for the great ages of geological time, and for those systems of formations which mark the successive submergences and emergences of the continental plateaus, separate classifications must exist for the different kinds of areas, in their details. It is also, I think, necessary that we should not tie ourselves down to hard-and- fast lines either as to the limits of systems or as to the relative values of their divisions in widely separated localities, as these differ in nature, and nothing is to be gained by conventional arrangements overlooking these diiterences. Finally, I can imagine that many questions which have not occurred to me may present themselves to the minds of other geologists who may read or hear this paper. Should I possess any facts tending to the solution of such questions, and not stated in the above pages, they will be at the service of any one desirous to use them for the advancement of science. Discussion. The Presiprent, whilst recognizing the importance of the paper, doubted whether the question of correlation of the Pre-Cambrian rocks on either side of the Atlantic was ripe for discussion. Dr. Hicxs felt sure that the paper would be welcomed on this side of the Atlantic. He agreed with most of the conclusions of the Author, including the correlation of the Huronian with the Pebidian. This was borne out, not only by similarity of lithologi- cal characters, but by the exact correspondence of the succeeding beds in the two areas as shown by Mr. G. F. Matthew. The diffi- culty of correlation lay with the rocks below the Huronian. He noticed that fragments of granitoid rocks occurred in the Huronian as in the Pebidian. He also had called attention to the contrast be- tween the Paleozoic rocks of the ocean borders and those of the interior of the continents, in papers read before the Society and else- where. Dr. Scorr referred to Mr. Walcott’s work, and mentioned the occurrence of great deposits of Pre-Cambrian rock in Arizona. Where terrestrial species play an important part, difficulties of corre- lation were much increased. Dr. Hine noticed the difference between the se game of America and that of the interior. Mr. Marr stated that the paper referred very fully eb the point noticed by the last speaker. - 818 REY. 0. FISHER ON THE OCCURRENCE OF 46. On the Occurrence of ELEPHAS MERIDIONALIS at DewzisH, Dorset. By the Rev. O. Fisumr, M.A.,F.G.S. (Read June 20, 1888.) In the year 1877 I saw in the Blackmore Museum at Salisbury two molars of an elephant, labelled “‘ Dewlish, Dorset.” I at once attributed them to E. meridionalis, and they interested me much, because I had been lately engaged upon the geology of Norfolk’, only in the pre-glacial Forest-bed of which county, so far as I was aware, that species had been found in this country. It was not, however, till the autumn of the year 1887 that I obtained any information upon the subject, when Mr. E. Cunnington, of Dorchester, told me that large bones had been lately found at the same place; and he gave me an extract from an old notice by the late Mr. Hall, a local antiquarian, that a memorandum of the original find of these remains was published in the ‘ Monthly Magazine’ for May, 1814, in which Mr. Hall states that “ there is a hill in the parish of Dewlish which was always supposed to be formed of chalk only ; but last summer (1813), about 100 feet above the level of the foot of the hill, some sand was observed to be drawn out by a mouse. It was taken notice of, and General Michel [the proprietor of the land] sent workmen to seek for sand.” At about 5 feet below the surface they found the teeth of the elephant, of which two are now exhibited. The section observed by Mr. Hall is recorded below. His description of the fossil remains is diverting. Mr. Blackmore, of Salisbury, in reply to my inquiries, writes that the specimens in their Museum were obtained by his grandfather, Mr. - Shorto, in 1814; and an exceedingly sensible letter, written by him to Mr. Hall, was published in ‘ Flint Chips,’ page 207. Mr. Black- more says that Dr. Falconer, from rubbings only, attributed these teeth to #. antiquus. But Mr. Ashford Sandford, on seeing the specimens themselves, at once said, “* Hlephas meridionalis without doubt,” adding, “ I have just been looking over the specimens at the British Museum, and can speak positively.” And this identification was published in ‘ Flint Chips’ in 1870. Mr. Boyd Dawkins also saw the specimens, and mentioned them to Dr. Leith Adams, who had sketches forwarded to him, but would not allow that they could be #. meridionalis, because that species had never been found so far west; he also mistook Dewlish for Dawlish, in Devonshire. Mr. Cunnington’s information revived my interest in the subject ; and I visited the locality on September 23rd, 1887, in company with my brother-in-law, Mr. H. B. Middleton. We were received by Mr. C. Kent, the tenant of the farm, and by great good fortune * See “On the Denudations of Norfolk,” Brit, Assoe. Norwich meeting, 1868 ; Geol. Mag. vol. v. Dec. 1868. Also other papers on Norfolk by the author in the same magazine. + ‘Flint Chips,’ by Joseph Stevens. London, 1870. ELEPHAS MERIDIONALIS AT DEWLISH, DORSET, 819 my old friend, Mr. Mansel-Pleydell, F.G.S., F.L.S., heard that I was coming, and met me there. Mr. Kent possessed a molar found in 1883, and also now exhibited. Fig. 1.—Section of Chalk-Escarpment at Dewlish, Dorsetshire. (Scale 100 feet to 1 inch.) extension of Fault. Stream | Probable a, Klephant-bed. The locality from which these remains have been obtained is situated just opposite the village, near the top of a remarkably steep, straight escarpment of a plateau of chalk, facing the west, and is in a district consisting entirely of chalk. The angle of the hill was estimated by me by the eye to be about 55°. But Mr. Pleydell considers it more steep than that. He has measured the position of the pit, if such it can be called, and has found it 90 feet above the foot of the hill, and 10 feet below its brow (fig. 1). The opposite side of the valley, in which the village is situated, rises with a gentle slope towards the Hast. The escarpment trends nearly North and South, and the Geological Survey map shows it to be on the course of a fault, which, where it runs out among the subjacent strata to the North, appears to be downcast towards the East. This shows that the scarp has not been caused by elevatory action; but the effect of the fault may possibly have been to harden the chalk along its course, and to turn up the edges of the beds, both of which effects would present obstacles to its denudation. A very remarkable circumstance is, that there is not a trace of a gravel terrace or the slightest outward indication of the existence here of anything except chalk, so that, had it not been for the geological explorations of the mouse, the deposit probably would have remained concealed to the present day. A small stream called the Dewlish runs near, but not close to, the bottom of the hill. Upon my visit, which lasted only two or three hours, with a man to dig for me, I did not get sufficiently into the deposit to observe any distinct stratification. I found only some angular gravel, impacted in an extremely fine sandy silt, and in this were numerous fragments of ivory, disseminated, forming a constituent part of the gravel, much as other stones would do*. Towards the bottom of * Possibly this had been disturbed in 1814. “4 820 REV. 0. FISHER ON THE OCCURRENCE OF the deposit I found the gravel much coarser and subangular; and here I met with a portion of a nearly worn-down molar (exhibited). I did not see any vestige of shells; but I found some extremely curiously polished flints, of which more anon. Lady Michel, the present owner of the property, most courteously gave me the loan of the two molars which were obtained in 1813, - and are now in her possession. Mr. Mansel-Pleydell has since carried on excavations with great success. He has sent mea section of the gravel-beds; and it is interesting to compare it with that made by Mr. Hall 75 years ago. Mr. Hatt’s Section, Mr. Manset-PLeYDELL’s SEcTION. CS 1 oY rma meee aan ago about 3 feet. | 1. Mould)... oe about 38 inches. 2. WW nite Clay accor eee Pak 2. Chalk rubble ............ 10: oo WANG: HL... caeoueeccereceeneeee aaa 3. Fine impalpable sand Ansa, 2... ceptepaee-eeeeees Sos and flints, remains of 5. Gravel with large flints ... 3 ,, elephant 2. 2:23 3 feet. G:, White clay. 2). -n.heera B35 4. Sand and ferruginous ho MOT as Oe rahe eee ine pravel <<. Challe 12.3..2 e ? Mr. Mansel-Pleydell has sent me some small samples of the various kinds of gravel that he met with. The fine sand consists of sub- angular grains of quartz with a few well-rounded grains probably of limonite, for they are not attracted by the magnet. We were both of opinion that the deposit has been water-borne, and is not the contents of a pot-hole. It is not deposited upon a shelf of chalk, but is undercut into the face of the escarpment. The length from North to South is considerable, but has not been exactly ascertained. The explanation seems to be that, when the stream formerly flowed 90 feet higher than it does at present, at this point it undercut a cliff-like chalk-bank. A somewhat similar relation of the stream to a chalk-bank may now be seen on the north side of Poundbury, near Dorchester, and under similar cir- cumstances of faulting on the south side of Maiden Castle. In esti- mating the lapse of time which is indicated by a difference of 90 feet between the former and present levels of the stream, it must be borne in mind that all surface-features are more emphasized in the West of England than they are in the Hast, the land appearing to have been always in a state of greater unrest. One might have attributed the elevation to a movement on the line of fault, had not the deposit been upon its downcast side. Had the elephants (for more than one individual has been entombed at the spot) been EL. primigenius or E. antiquus, their occurrence would hardly need to have been chronicled ; but £. meridionalis being, so far as it is known in this country, a pre-glacial species, this renders its occur- ELEPHAS MERIDIONALIS AT DEWLISH, DORSET. 821 rence, in a district in which, so far as 1 am aware, no glacial phe- nomena have been certified, more interesting. Mr. Mansel-Pleydell and myself have thought it therefore worth while to bring this notice before the Society. Polished flints have been already mentioned as being found among the gravel. Most of these are polished only upon a portion of their surface. Prof. Prestwich and myself in the year 1873 found a deposit of gravel in Portland which, in my opinion, overlay a swallow-hole, where the pebbles were similarly polished, and formed almost a pudding-stone, the interstices being occupied by a cement of calcite. In that instance it appeared to me that the polishing was due to the long-continued percolation of water, carrying fine silt with it, and I suspect that a similar process has been at work at Dewlish since the deposit was laid high and dry, the unpolished portions of the flints being where they were held fast, and the polished surfaces the portions past which silty water has percolated. The discovery of the molar in 1853 by Mr. Kent led Mr. Mansel- Pleydell to resume the search, and he soon found a left humerus, four feet long. This was left protected by a covering of sacks and hurdles, but a rough party from a neighbouring village visited it on the next day, which was a Sunday, and demolishedit. Since my visit he has continued his excavations, and, including the humerus, the following bones have been found* :— 1. A left humerus 4 feet long. 2. A radius 2 feet long. 3. An ulna, length 2 feet 2 inches. 4. An entire scapula with ridge and recurved process. 5. The anterior border and fossa of a scapula 3 feet 6 inches long, and 9 inches from the border to the ridge and spine. 6. The left side of a pelvis, ischium missing; length of ilium a outer border 3 feet 10 inches. ' 7, An ischium (?) detached ; length (transverse) 2 feet 2 inches, breadth at broadest end 1 foot 1 inch, at most. constricted part 84 inches. Maen 8. A femur, length 2 feet 3 inches. 9. A tibia, length 1 foot 10 inches. 10. The massive left alveolus of an upper jaw, the cavity of which corresponded with a magnificent tusk which lay near it. The orifice for the insertion of the latter was cylindrical and 6 inches in dia- meter ; the other extremity was somewhat flattered, expanding into a thin, wing-like plate on one side. Dr. Falconer considered the angle which this part makes with the frontal plane to afford a mark of distinction between E. meridionalis and E. primigenius, but unfortunately, owing to the detachment. of the two, this angle could not be observed. The length of the bone was 3 feet 9 inches. 11. A tusk 6 feet 2 inches long, and 6 inchesin diameter at its base. The point, for about 18 inches, rested perpendicularly upon a bed of waterworn flints, mingled with fine quartz-sand. By a bold * These descriptions are by Mr. Mansel-Pleydell. 822 REV. 0. FISHER ON THE OCCURRENCE OF upward curve the middle portion, at about 16 inches distance, was raised two feet four above the base line, and from that point it lay nearly horizontally, though with a slight inclination downwards. The posterior end lay within a few inches of the alveolus just described. 12. Another tusk of much larger dimensions, 7 feet 6 inches long, and 2 feet 3 inches in circumference at the base. About 18 inches of the anterior end missing. It was probably in this condition when the superincumbent bed of clay was deposited, as they are in con- tact. This tusk differs in shape from the preceding; the curve (which bore its whole weight as it lay in the bed) had an upward and forward direction. Both extremities touched the clay-bed above. The deficient extremity probably had an outward direction. 13. Remains of other tusks were scattered in several parts of the deposit. In some places the fragments of ivory were so numerous as to predominate over the other materials. 14. A molar; crown in use 44 inches long, consisting of 6 plates (the anterior missing); 6 others unexposed and notin use. Breadth of fourth plate in use 32 inches, depth 43 inches. 15, Another molar; crown 74 inches long, consisting of 10 plates. Breadth of fourth plate 34 inches; depth from tenth plate (posterior) to the fang 5inches. This molar appears to be that of a broad-crowned Elephas antiquus ; although the enamel is as thick as in #. meridionalis, the cement-wedges are much thinner. 16. Several other molars of Elephas meridionalis have been found, the whole number from the first until now being seven, including three plates and part of the fourth in which the digitations are worn down into continuous ridges. A right upper molar is figured on the opposite page (figs. 2,3). (‘The specimen, the two tusks, the alveolus, the femur and the tibia, have been presented by Mr. Mansel- Pleydell to the Dorset County Museum.) 17. Several isolated plates of other molars are scattered in various parts of the deposit. There is considerable variety in the various Jayers of the deposit ; but only one of them contains bones. Some large blocks of chalk seem formerly to have fallen from the top, and it is to the protection which one of these has afforded, that Mr. Mansel-Pleydell attributes the preservation of the tusk. As yet no data have been obtained to fix the geological age of these remains. No vestiges of other animals have been found, nor any shells or microscopic organisms. The position of the deposit, close to the summit of a lofty escarpment, suggests a far-gone age, which may have been even pre-glacial ; and the absence of any terrace-like feature may point to a stream of ice, abrading gravel and chalk alike down to a uniform cliff-like face, as having been the sculpturing agent. It is not, however, impossible that a stream, continuously attack- ing the base without meandering away, might produce such a cliff-like escarpment. But its unusual steepness is, no doubt, partly due to the hardening of the chalk along the course of the fault. 823 ELEPHAS MERIDIONALIS AT DEWLISH, DORSET, Molar of Elephas meridionalis, (Z nat. size.) from Dewlish, Dorsetshire. Fig. 2.—Side view of Right Upper ( nat. size.) Fig. 3.—Grinding-surface of Right Upper Molar of Elephas meridionalis. $24 ELEPHAS MERIDIONALIsS AT DEWLISH, DORSET. Discussion. The Presipenr would like to have a further explanation of the polished pebbles referred to. The peculiar manner in which the bones occurred was very interesting; was there any possibility of the deposit being an eroded pipe ? The Avrnor said that the pipe-theory had at first occurred to him ; however, the beds where the fossils were obtained are distinctly water-deposited Mr. Manset-PLeyDELL agreed that the beds were stratified. He gave a description of them. The lower beds consisted of one contain- ing broken chalk and fits, between two others half an inch thick, ferruginous, and composed exclusively of thin flints, like shells ; then came the bone-bed of the finest sand, associated with large and small flints more or less polished, the smaller at the top. Fragments of ivory, owing to their being lighter, occurred immediately above, and there was some more broken chalk and clay—the point of a tusk just reached this clay. He then enumerated the bones found, which he thought might belong to two species, one being much larger ~ than the other. The teeth shown by Mr. Fisher were those of E. meridionalis. Mr. Newron had little doubt that some, at least, of these teeth belonged to HL. meridionalis, and those which were not like #. meri- dionalis resembled very closely certain other Forest-bed forms. The question of age, too, was a matter of importance. Unfortu- nately nothing was known of the associated fauna; but it seemed more likely that these beds would prove to be of about the age of the Cromer Forest-bed, than that H. meridionalis should be found passing up into Pleistocene deposits. The AvrHor asked if the extremely steep escarpment might not have been due to ice-action. ON THE MOVEMENT OF SCREE-MATERIAL. 825 47. Seconp Nore on the Movement of Sorre-Marertart. By Cartes Davison, M.A., Mathematical Master at King Edward's High School, Birmingham. (Read June 6, 1888.) (Communicated by Prof. T. G. Bonney, D.Sc., F.R.S., F.G.S.) [ Abridged. ] Tue first results of the experiment described in this note, namely, those relating to the period from May 5 to September 22, 1887, have already been recorded in a paper read before the Geological Society on February 29, 1888 *. After a brief interval the experiment was continued under the same conditions as before, from October 4, 1887, to May 5, 1888, with the object of comparing the rates of descent in the winter and summer halves of the year, and also of determining the effects on creeping of rain and snow. Allowing a distance of 4 mm. for the interval of 12 days during which the experiment was suspended, the total descent during the year was 131 mm. (i.e. a little more than half an inch), the mean rate of descent being therefore -00140 inch per day. Comparison of the Rates of Descent during the Winter and Summer Months.—Dividing the year of the experiment into winter, from October 4, 1887, to April 3, 1888, and summer, from May 5 to October 4, 1887, and April 3 to May 5, 1888, we have :— Average daily Total descent Rate of descent range of tem- in mm. in inches per perature Tf. day. Summer (184 days)...... 14°-4 F. 8 00171. Winter (182 days)...... 8°-0 53 00112. Had the creeping movement been proportional to the range of temperature, the average daily descent during the winter, compared with that during the summer, would have been rather less, namely *00095 inch per day. Not only, however, is the heat of the sun more intense in summer than in winter, and consequently the effects produced by passing clouds so mnch the greater, but also for about three months of winter the experimental stone was entirely shielded from the sun by surrounding houses. Clearly, then, other causes must have operated in producing the comparatively rapid rate of descent during the winter months. Influence of Snow.—The heavy snow-storms which visited many parts of England during the last winter were represented at Birmingham by very meagre falls. Except between February 14 and March 28, the snow seldom lay upon the ground, and when, on several occasions between these dates, it did lie for a short time, the * Quart. Journ. Geol. Soc. for May 1888, p. 232. t Excluding 20 days from August 6-25, and 8 days from February 15-22. 826 ON THE MOVEMENT OF SCREE-MATERIAL. snow was nearly always driven by the wind from the experimental stone before the middle of the day, or melted by the increasing heat of the sun. During the 12 weeks from November 23 to February 14, the average daily range of temperature was 7°°5 F., and the average daily descent only ‘00078 inch. From February 15 to April 3, a period of 7 weeks, the average daily range of temperature (during all but the first 8 days) was 8-2 F., and the average daily descent (during the whole time) ‘00147 inch, nearly twice as great as in the preceding period. I believe that this difference was chiefly, though not entirely, due to the influence of snow. By contact with the snow the upper stone is more thoroughly and quickly cooled than by contact with the air. Moreover, the lower stone is directly cooled only by the air, and as the movement depends on the difference of the temperatures to which the stones are at any time subjected, the effect of short and repeated contact with a covering of snow is evidently to increase the rate of descent. On the other hand, snow, when it lies thickly and for long periods, prevents the stones from fully participating in the range of tempera- | ture to which they would otherwise be subjected, and the effects of mere creeping are then reduced to a minimum. DIRECTIONS OF ICE-FLOW IN THE NORTH OF IRELAND. 827 48. Drrecrions of Icz-rLow in the Norru of IRELAND, as DETER- MINED by the OssERvatiIons of the GuotoeicaAL Survey. By J. R. Kirroz, Esq. (Read June 20, 1888.) (Communicated by Prof. E. Hunt, F.R.S., F.G.8.) Tre field observations of the Geological Survey, Ireland, being completed, it was considered desirable by the Director to represent those bearing on glacial phenomena in the northern half of the country on a general map, scale ten miles to one inch. Data for this were amply furnished by the one-inch sheets already published, and by those in course of preparation, upon which the usual map- indications of glacial strize are numerous and distinctly shown. _ These indications consist of circles denoting the places of observation, lines crossing those circles giving the trends of strize, and arrow- heads attached \thereto indicating the directions of ice-flow when these are determinable. In carrying out this transfer a remarkable circumstance became apparent, namely, that the striz were capable of being resolved into two distinct sets, nearly at right angles to each other; which rendered it convenient to appropriate two copies of the general map to the two sets of striz. The stricz thus transferred have been further connected by continuous lines about three eighths of an inch apart, or have served as guides when the lines do not happen to pass through the exact points of observation. So constant in direction are the strize of each set over an area of some 16,000 square miles, that they maintain an almost unswerving parallelism to those continuous, though slightly waved lines. Comparatively few deviate more than a few degrees to one side or the other of the general direction, such deviation being adequately accounted for by local inequalities of the surface. Of more than 600 recorded observations, the trend of striz at some nine or ten points cannot be thus accounted for, and they have been relegated toa third copy of the general map. They are doubtless attributable to local ice-flows; and as an instance may be cited evidence for a glacial movement southeastward from the Sperrin mountains of Londonderry, which at some period thus seem to have been the centre of an independent glacial system. Probably several other minor systems existed, evidences for which are now wanting, or merge with those going to establish more extended and general systems of glaciation. Now, while the striz to the east of a line drawn from Strangford Lough to Galway Bay all trend in one direction, two sets of striz occur north-west of that line, and these generally at right angles to each other, as above mentioned. This, it will be conceded, is an interesting fact, and cannot be accounted for, as has been attempted, by conceiving that the same general ice-flow could have produced both. The remarkable absence of two sets south-east of the line mentioned is perhaps the strongest argument against this supposition. The sequel, too, makes manifest how unnecessary such a supposition 828 MR, J. R. KILROE ON DIRECTIONS OF ICE-FLOW is. With this may here be mentioned that both sets have been observed on the same flat surface in several instances, and that both are alike found in the valleys and on the flanks and summits of some of the highest hills. Directions of Stric.—Of the two sets of strie referred to, the direc- tion of one varies from north to north-west, which, as evidence of ice- movement, will be considered hereafter. The direction of the second set is W. 25° S., swinging round to W. in Donegal, and S.W. towards Galway Bay, and is strikingly persistent throughout. The value of this fact will be appreciated when it is stated that if we select a few scattered points by way of illustration, the di- rection of striz is almost the same whether at 1200 feet above the sea at Glenarm, or near the sea-level at Belfast and Londonderry ; 700 feet above datum, S.W. of Draperstown ; 1250 in Slieve Beagh, co. Tyrone; 1200 in SI. League, co. Donegal; 1100 in the Nephin Fig. 1.—Map showing Glaciation of the Northern Parts of the British Isles. I /V. Ma ut HAs J Y, Z g SZ i Z 7 41 Zz \ a | Group, co. Mayo, or on the shore of Sligo Bay. To account for this uniformity of direction, whether at the sea-level or more than 1000 feet above it, whether in Antrim, Tyrone, Donegal, or Mayo, IN THE NORTH OF IRELAND. 829 we must conceive the passage of an ice-sheet of vast thickness across the country with uninterrupted flow. We proceed to show that an ice-sheet crossed the North Channel from the Scottish coast opposite, forming a portion of the Mer de glace which originated in the Central Highlands, and which we may for this reason speak of as “The Scottish Glacial System” (see Map, fig. 1). That an ice-flow has invaded the east of Antrim from seaward has been fully established by my colleagues Messrs. Symes and M*Henry, who were engaged on the Survey of that part of Ulster, and who have indicated on the Government maps several instances of strive in this direction. Confirmatory evidence of this westerly movement is found in the occurrence of blocks of the cha- racteristic columnar basalt of Fair Head, westward of their original site, included in the drift which overlies the schist and Carboniferous- Limestone areas near Ballycastle. Mr. Symes informs me that he found blocks of chalk in Carnlough Glen, due west of Glenarm, 400 feet above the sea-level, and resting upon basalt one mile within its boundary, which must obviously have travelled westward and upward from their parent mass. Blocks of schist from Cantire bestrew the surface of Rathlin Island, where striz also are nume- rous, most of which indicate a westerly ice-movement. In Ayrshire and Wigton numerous striz are represented on the Goverment published maps, which seem separable into two distinct sets, as in the case of those in the North of Ireland, the directions moreover being strikingly similar to those maintained by the two sets in the Irish area. It will at once be seen that those bearing westward indicate an outward flow towards the Irish coast, and strongly suggest the connexion of this flow with that which moved landward from the North Channel over the counties of Antrim and Down. The small map published by Dr. Geikie in his ‘ Scenery of Scotland’ *, showing the glaciation of that country, clearly suggests the theory we maintain, and has supplied matter for the prepa- ration of the small map (fig. 1) accompanying this paper. This author has likewise given us numerous interesting data, with deduc- tions therefrom, as to the vast extension of the Mer de glace which centred in the Scottish Highlands. Eastward it coalesced with the Great Scandinavian ice-sheet, and south-westward united with the Trish Glacial system, so as to form a vast glacier, probably extending from Cape Clear to the North Cape, a distance of 1500 miles. Considering the movements of this ice-sheet, as it spread itself outward to reach the open ocean, Dr. Geikie informs us that part of it moved southward along the floor and over the shores of the German Ocean. We also know that part moved northward and north-westward over the Orkney Group fT, and that westward it crossed the Minch and Outer Hebrides, to fill the contiguous * Pp. 251 ez seq. t Paper and map by Messrs. Peach and Horne, Quart. Journ. Geol. Soc. vol. xxxvi. t Paper by Jas. Geikie, LL.D., F.R.S., Quart. Journ. Geol. Soe. vol. xxxiv. 0.3, G8. No, 176. 31 830 MR. J. R. KILROE ON DIRECTIONS OF ICE-FLOW ocean-bed, probably to the verge of the Atlantic trough, some 90 miles distant from the Lewisian chain of islands *. It may perhaps be questioned whether the Scottish ice-sheet, impinging on the Irish coast, was of sufficient thickness to breast and overtop the Antrim coast-line, when little less precipitous than it now is, and achieve those phenomena with which we accredit it in the Irish area. As bearing upon this interesting point, the following data and considerations are presented, viz. :— Striz bearing westward have been observedt about the centre of the Nephin Group, Co. Mayo, at the 1100-feet contour. Dr. J. Geikie states that an ice-sheet, after crossing the Minch from the Scottish Highlands, attained an elevation of not less than 1600 feet in North Harris {; that in South Uist glaciation is traceable up to about 1650 feet or more, on Beinn-Mhor {; and that “scratches may be traced .... up to an elevation of 3500 feet at least,” in the High- lands§. The same author believes that ice buried Scotland to a depth of several thousand feet, only a few hill-tops rising above the general level of the Mer de glace §. And in his ‘Scenery of Scot- land,’ Dr. Archibald Geikie records striz at a height of 2250 feet on Ben Lomond |}. If we conceive these points connected by an ideal plane, the plane would mark a minimum upward limit of glaciation during the period of intensest cold; and ascending by an imperceptible gradient towards the Grampians, would be some 2000 feet above the present sea-level at the Antrim coast-line. Allowing for unobserved and effaced glacial traces, at higher elevations than the points referred to, also for the depth of ice and névé necessary to leave appreciable traces on the more elevated surfaces of rock over which the mass moved, the “‘ general level of the Mer de glace,” mentioned in the above extract, probably attained a much higher level than the plane which indicates the limit of observed glaciation. The ice-sheet probably exceeded 3000 feet in the North Channel, the present depth of water being 700; and urging its way westward, it over- topped the coast escarpment by some thousand feet or more. It has hitherto been supposed that the Irish Mer de glace was sufficient to obstruct the Scottish ice-current and divert it north- ward, after its encroachment to some extent upon the territory of the former. But strie have been observed bearing westward, from the entrance to Lough Foyle throughout the county of Donegal to the western sea-board, which could not have resulted otherwise than from ice continuous with and moving en masse with the sheet which blocked up the adjacent oceanic area, as already described. Such an ice-movement alone satisfactorily accounts for the occurrence of chalk-flints in the drift of Inishowen which bestrews the Northern Donegal coast from Inishowen Head to Malin Head. What thus at this period hindered the northward flow in Donegal would, a * See Messrs. Peach and Horne’s map above referred to. Dr. Croll supposes the ice-cliff terminating the great ice-sheet westward to have been about 170 miles distant, see Chart, p. 449, ‘Climate and Time,’ 1875. t By myself in 1878. ; ‘Great Ice Age,’ ed. 1 (1874), pp. 83, 86. t Paper sup. cit. p. 832. | ‘Scenery of Scotland,’ ed. 2 (1887), p. 252. IN THE NORTH OF IRELAND. 831 fortiori, further inland, hinder a northward movement; and it follows that we find strie in Tyrone, Fermanagh, Mayo, &c., bearing south of west, all obviously due to the prevalence of a Scottish ice- system over the Irish, so far southward as the occurrence of west- ward strie warrant us to predicate its influence. Confirmatory evidence for the westward movement is to be found in the absence of granitic blocks from the Lower Boulder-clay of Glen Swilly *, and from the boulder-clay which rests on the granite at the north entrance of Barnesmore Gap. Hence the ice-sheet which passed off the Wigton and Ayrshire coast flowed on to Irish soil, and urged its way across the country, bearing previous accumulations before it, to escape on the western coast by the various bays of Donegal, Sligo, Mayo, and Galway, and over mountain groups which were unable to command an independent glacial system sufficient to obstruct or divert its flow. Dr. Hull considers that a glacial system, centred in the Mourne Mountains, presented such an obstacle ; and this would account for an absence of westward strie south of the Strangford- Lough and Galway-Bay line. The Irish Glacial System (Map, fig. 2).—Much has been done by Fig. 2.—Map of the North of Ireland, showing the North-Irish system of glaciation, after Professor Hull. the Rey. M. Close towards the elucidation of glacial phenomena in the Irish areay; and his map of the glaciation of [arconnaught, * As observed by Mr. M°Henry. t Paper on the ‘‘ General Glaciation of Ireland,” with Map, Journ. Roy Soc. Trel. vol. i. new series, p. 207. 832 MR. J. BR. KILROE ON DIRECTIONS OF ICE-FLOW prepared in conjunction with Mr. G. H. Kinahan, and published in 1872, has furnished important aid in the preparation of the maps accompanying this paper. Dr. Hull, in his ‘ Physical Geology of Ireland,’ has described the glaciation of the country in considerable detail; and on his map* indicates an axis of glacial movement, coincident with a great central snowfield which sent its flows north- ward and southward. This the author represents as stretching north-eastward between the counties of Galway and Antrim ; and it is satisfactory to be able to state that all the evidence brought to light since the publication of his book in 1878 goes to establish his conclusions beyond question, with some additional details to be mentioned presently. It has been stated in the opening pages of this paper, that the prevailing direction of one set of glacial striz in Ulster is northerly. More exactly the striz trend N. by W.in Antrim and Londonderry ; N.W. over the highlands of Fermanagh; and N.E., N., and N. by W. in Donegal, &c., all indicating a northerly ice-flow. South of the axis of glaciation, the flow has unquestionably been south-easterly, over the central plain of Ireland and towards the Irish Sea, even across the Mourne Mountain. This group is well glaciated from the sea- shore at Carlingford Lough up to 1200 feet, and probably above it; the Fermanagh hills up to 1000 feet, and those in Donegal to 1340. The Irish glacial system thus attained important proportions. South-easterly striz abound on the east coast of the county of Down, and some bearing northward occur in Rathlin Island. It is there- fore obvious that the central snow-field extended at least to the coast- line of Antrim, perhaps beyond it towards the Scottish coast opposite. And it would seem, judging from the directions of striz in Fer- managh and Donegal, that a spur or projection from the central snow-field extended westward to the head of Donegal Bay, across Barnesmore Hill. Relative Ages.—It remains to consider the Irish and Scottish systems of glaciation with reference to their relative ages. Unfortunately the comparative freshness of striz belonging to the two sets when occurring in proximity has not received the special attention which alone could invest this class of evidence with due weight. For it will be remembered that until of late both sets were believed to indicate but one general ice-movement, and therefore to be practically contemporaneous. It is, however, reasonable to sup- pose that a very considerable accumulation of snow and ice obtained in the Irish area, during the period of intensest cold, while the Scottish system was gathering maximum strength, and that an ice- movement outward was concomitant with this accumulation. Sucha movement would obviously be northward in Ulster; and would maintain this direction until the Scottish ice-sheet invaded this area, to move westward uninterruptedly. Previously formed striz would thus be to a large extent effaced and replaced by those bearing westward. Some might remain, to indicate a more ancient date for eae Ste IN THE NORTH OF IRELAND. 833 the former probable ice-flow ; but they would obviously be very few. Strie bearing northward are, however, by far the most numerous ; from which we conclude that during the decline, or possibly after the decline and subdued revival of glacial conditions, an inde- pendent Irish Mer de glace flowed northward and southward, finding its axis of movement in the Great Central Snow-field. It need scarcely be added that south of the Galway Bay and Strangford-Lough line, the ice-movement appears to have continued unchanged in direction throughout the glacial epoch, until the Mer de glace gave place to numerous independent local systems, with their glaciers and moraines, which marked the decline and extinction of glacial conditions in this country. Discussion. Mr. Marr commented upon the supposed partial obliteration of one set of strie by the ice which had produced a second; whilst the latter appeared to be comparatively fresh, though overridden by a third ice-flow. The Presmpent noted that Prof. Dana had brought forward evidence to show that the ice passing down valleys in Connecticut moved in quite a different direction from that passing over the ridges. 834 MR. J. H. COLLINS ON THE SUDBURY COPPER-DEPOSITS. 49. On the Suppury Copprer-Deposits. By J. H. Cottrs, Esq., F.G.S. (Read June 6, 1888.) [Abridged.] Tue extensive deposits of copper-ore in the neighbourhood of Sud- bury, to the north of Georgian Bay on Lake Huron, have attracted a great deal of attention during the past two years. The geological and mineralogical characters of the Huronian rocks of the Sudbury district were described by Prof. Bonney in a paper read before the Geological Society of London in November of last year *, ‘The copper was discovered about the time of his visit; but as he does not refer to it in his paper, I presume his attention was not called to it. At first it was thought to be an immensely important discovery, likely to revolutionize the copper-trade, and to reduce the price of copper, then, and for a long time after, only £40 per ton, to a figure which would render such mines as Rio Tinto, Calumet and Hecla, and Anaconda quite unremunera- tive. One of the deposits, the Stobie Mine, which had been tested by a series of shallow trial pits, was reported to consist of ‘*a mass of solid sulphides of copper and iron, 1600 ft. long and 1200 ft. across,” the depth being supposed practically unlimited. The description (published only a few months before my visit in October 1887, but written some time before) runs accurately enough as follows :—“ It is in the form of a wide round hill, covered, like the surrounding region, with burnt trees, and in appearance it does not differ in any way from the other low hills around, except in the presence of a large proportion of oxide of iron, which gives a red appearance to the surface soil. Beneath this is a kind of ‘pan’ of iron oxide resembling bog iron-ore, and still deeper frag- ments of partially decomposed pyrites”t. At first the ore-bodies were supposed to be as extensive as these surface-gozzans, and as similar gozzans may be traced at intervals for eight miles in a south-westerly direction as far as Kelly Lake, nearly following the strike of the rocks, the most exalted notions were entertained as to the value of the deposits. The principal mine-workings are about eight miles apart. These are known as the Copper Cliff and the Stobie respectively. Other smaller works have been started and are known as McConnell, the Eyre Mine, the Evans, the Lady Macdonald, and Kelly Lake. Copper was first discovered at a point on the main line about two miles north-west of Sudbury in 1883, and the Canadian Copper Company was formed to work the Copper Cliff and Stobie in 1885. At the former place the ore was found in the face of a cliff of diorite forty or fifty feet high. By digging away at the foot of this cliff a total height of 80 or 90 ft. was soon exposed. This was thought to be a cutting in a veritable mountain of ore—decomposing * Quart. Journ. Geol. Soc. vol. xliv. p. 32. ‘Canadian Mining Review,’ Sept. 1887. MR. J. H. COLLINS ON THE SUDBURY COPPER-DEPOSITS. 835 sulphides with oxides and carbonates near the surface, solid copper- pyrites with magnetic pyrites (pyrrhotite) below. Blocks of nearly pure copper-pyrites, weighing half a ton or more, were raised, and about four thousand tons of ore were actually taken out and shipped for smelting to New York, some assaying as high as 18 per cent. of copper, a still larger quantity, running only 3 or 4 per cent., being rejected. As might have been expected, however, it proved to be merely a rich bunch in a cupriferous belt, and not a “‘mountain of ore.” A shaft has been sunk following the dip of the belt to a depth of more than 100 feet on what seems to be a sort of ore-vein running diagonally across the belt, and levels have been commenced right and left at various depths. A section of the workings at the Copper-Cliff Mine is given in fig. 1. The mine is Fig. 1.—Section of Ore-deposit at Copper Cliff. (Scale about 130 feet to 1 inch.) Cliff, Tih Wi i) WHS i, Ve Wi Wii} Wy Dy / Vy a 7 y i My ase i} yy i )) i] I), y/ PN Wy Wi 7) UH f=V KA U yi) a wh 7 S.E. Hy = lyf f “ES Le ¥ i] iy \ dl I y} a. Huronian deposits. 6. Diorite. ¢. Ore-mass. s. Shaft on diagonal vein. connected with the Algoma branch by a siding about a mile in length, built by the Canadian Pacific Railway Company. At the Stobie Mine the ore-body has been exposed for a length of several hundred feet, and to a depth of forty or fifty feet. By means of bore-holes it has been tested to a further depth of 30 ft. A section of this deposit is given in fig. 2. It was at first thought that the ore dipped to the south-east, and the shaft shown at s_ was actually sunk to a depth of 70 ft. at a point about 450 ft.. away from where the works were first started, in the assured ex- pectation of coming upon mineral. As none was found, a bore-hole was put down in the bottom of the shaft to a further depth of 80 ft., but still without success. Another bore-hole was then com- menced much nearer the ore-body, and inclining towards it, but still no ore was found, although it was carried to a depth of 200 ft. In fact, at the time of my visit, all the appearances were in favour of the deposit dipping to the north-west, but very steeply, as indicated by the section. 836 MR. J. H. COLLINS ON THE SUDBURY COPPER-DEPOSITS. As at the Copper Cliff, a very large proportion of the ore has to be rejected, being of too low a grade to bear the expense of transport to the smelting-works. At first an annual output of at least Fig. 2.—WSection of Ore-deposit at Stobte Mine. (Scale about 130 feet to 1 inch.) S.F. = — —— — = = = ee ee ) MH}; a Ee me Rarer Y), Hy y g SEN Ss TiN \ a / Wf | i) PY iH | s iY) Ld) Hy if /} Uf i) / rs Ai) ZW MM MY A 7 eS YU Uy) A Wf | See, SS — — es iif a i a. Huronian strata. 0. Diorite. c. Ore-body. s. Shaft. xx. Bore-holes, 30,000 tons was confidently anticipated ; but up to the present time the total production of two seasons has not amounted to 10,000 tons. Some small workings have also been made at the “6 in 6,” the McConnell, the Eyre, and other places; but none of them of any extent, and none have as yet yielded saleable ore. These various works, although so far not at all profitable to their owners, have yet sufficed to demonstrate several important facts. The ore exists in three distinct forms as follows :— 1. As local impregnations of certain siliceous and felspathic beds or belts of rock of clastic or fragmentary origin, in the form of spots, patches, and strings of cupreous pyrrhotite, or magnetic pyrites. 2. As contact-deposits of the same mineral lying between the impregnated beds just mentioned and certain large interbedded or intrusive masses of diorite. 3. As segregated veins of copper-pyrites and of highly nickeli- ferous pyrrhotite of secondary formation filling fissures and shrink- age-cracks in the ore-masses of the second class. There is much in this mode of occurrence to suggest that the copper occurring in the first mode was an original, or at least a very ancient, constituent of the beds, while the richer masses of the second and third modes of occurrence have resulted from later segregations into openings produced either by the intrusion of the diorites or by internal movements of the rocks. A comparison is at once suggested with the cupreous pyrites of the Sierra Morena, and especially of Rio Tinto, described by me in 1885*. Although the containing rocks at Sudbury, and the de- * “On the Geology of the Rio Tinto Mines,” Quart. Journ. Geol. Soe. vol. xli. p. 245. MR. J. H. COLLINS ON THE SUDBURY COPPER-DEPOSITS. 837 posits themselves, are so different in age and in mineral character, yet the modes of origin have apparently been very similar. In each region we have highly inclined stratified beds penetrated by dykes of igneous origin which have followed the stratification so closely that they present the appearance of interbedding, and suggest a contemporaneous origin until very closely examined. The following conclusions seem to me to be fully warranted in both regions :— (1) The rocks immediately enclosing the ore-deposits were originally, or at a very early period, pyritous and probably cupri- ferous. (2) The intrusions of igneous matter gave rise to lines of weak- ness along the planes of contact. (3) Subsequent fissuring and, to a certain extent, faulting oc- curred at these contact-planes. (4) The filling-in of these fissures was mainly by solution from the pyritous and cupreous material of the enclosing stratified rocks. (5) There is, in places, a pyritous breccia indicating a partial mechanical filling. (6) There is, in places, a concentration of mineral matter in those portions of the ‘country rock” which adjoin the more solid deposits occupying the fissures. (7) The formation of rich veinlets or “leaders” of ore within the masses has been the result of subsequent operations, probably at many very different times. These veins appear to occupy minor faults and shrinkage-cracks, and to have been filled by segregation of more richly cupreous material derived from the main masses of pyrites. (8) Abundant evidence of partial movements within the masses of pyrites is afforded by the numerous slickensides which are every- where and continually met with. So far, the phenomena observable in the two sets of deposits are parallel, if not absolutely identical. The following differences may now be noted :—At Sudbury the stratified rocks are Huronian, the intrusive masses dioritic, and the mineral deposits mainly pyrrho- tite, a monosulphide of iron, or nearly so, with less than 40 per cent. of sulphur when free from foreign matter. At Rio Tinto and in the south of Spain generally the stratified rocks in which the pyritous deposits occur are Upper Devonian, the intrusive masses are generally, if not always*, quartz-porphyries, and the deposits always consist in the main of bisulphide of iron with 50 per cent. or more of sulphur, pyrrhotite being unknown. In addition to the great differences of age and of mineral composition, we may ob- serve in these two series of deposits the following differences in their surroundings :— a. At Sudbury there is little or no evidence of kaolinization of the felspathic ingredients of the country rocks in the immediate * According to R. Wimmer some of the deposits in the neighbourhood of Tharsis are associated with dioritic intrusions. Od. G..S. No. 176. 3K 838 MR. J. H. COLLINS ON THE SUDBURY COPPER-DEPOSITS. neighbourhood of the deposits. It is true there is not much felspar present, and that little is not orthoclase, hence perhaps the dif- ference in this respect. At Rio Tinto kaolinization is very marked. 6. As at Rio Tinto and in the Sierra Morena generally, so at Sudbury, the actual presence of pyritous matter is indicated by the existence of a highly ferruginous subsoil; but in the latter region there are no ancient lake-deposits of i iron-ore like those capping the Mesa de los Pinos at Rio Tinto*. This, however, is a local dif- ference in respect only of a secondary deposit of comparatively recent origin and of no genetic importance. In conclusion, I would remark that whatever may be the cause of the important differences in the nature of the pyrites at Sudbury and in the south of Spain, there is no reason to suppose that it results from the differences in the containing rocks, since similar differences are frequently observed in the pyritous deposits of Canada when the country rocks are identical. It is possible that a more minute examination of the various Canadian deposits would throw light on this important subject; but hitherto such an in- vestigation does not seem to have been made. [Norn, October 22, 1888.—Very little work has been done since the above was written except at the Evans Mine, where the ore is said to have the following average composition :—copper 3 per cent., nickel 34, iron 40, sulphur 24, rock 494. It is proposed to erect concentration- and smelting-works, and to ship the nickeliferous “matter” to the United States for subsequent treatment; but as yet this is a proposition only. | Discussion. The Prestpent observed that the comparison of these deposits with those of other regions constituted a valuable feature in the aper. Mr. Atrwoop confirmed the statements of the Author as to these deposits occurring in the Huronian, consisting of gneiss, quartzites, and clay-slates. There was an abundant occurrence of diorites, which in his opinion had brought up the metals. These diorites strike N.E. andS.W. He had seen no evidence of contact-deposits ; the diorite-intrusions were very plainly shown intersecting the clay- slates, &c., by examining the railway-cutting south of Sudbury, on the Algoma branch. * Op. cit. pp. 253, 263. GENERAL INDEX TO THE QUARTERLY JOURNAL AND PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [The fossils referred to are described ; and those of which the names are printed in italics are also figured. | Aberdeen (S. Africa), section north of, showing the junction of the Karoo ei Keea beds, 261 ; section through, 270. Acadian group of rocks, 805. Achumore, section through, 418. Acidaspis erinaceus, 728. , zone of, 674, 683, 685, i 688, 689, 690, 692, 696, 698, 2. Actinolite in greensand at base of Thanet Sand, 758. Adamson, Mr. 8. A., on a recent dis- covery of Stigmaria ficoides at Clay- ton, Yorkshire, 375. Africa, South, two new Lepidotoid Ganoids from early Mesozoic de- a of the Orange Free State, 138. : , Geology of, 239. Agate pebbles, eroded, from the Sou- dan, 368. Agglomerates near Llangefni, 487. Ailurus angilicus, a new Carnivore from the Red Crag, 228. Ainimiké series, 801. Albert Asylum well, Upper Bagshot in, 608, 609. Aldershot, Upper Bagshots in Thorn Hill, 612. Allt Halag, section from Elphin to, 426. Allt Leth Slighe, section in, 71. Alluvial gold, general absence of, in Mysore, 650. America, the Eozoic and Palsxozoic rocks of the Atlantic coast of Canada, compared with those of the interior of, 797. Amlweh, 516. Ampyx aloniensis, 724. ——., zone of, 673, 674, 682, 685, 687, 688, 690, 695, 698. Analyses of Cretaceous deposits in Lincolnshire and Yorkshire, 358; of South-African Coals, 251; of Ardtun tachylyte, 303; of garnet from Mysore, 641; of ‘“ Kunker” from Mysore, 642; of epidotes, 742; of limestone under salt in Durham, 763; of rock-salt from Middles- borough, 782; of rock-salt from the Saltholme borings, 782. Anglesey, physical history of the Monian rocks of, 543. ——., Pre-Cambrian rocks of, 463. Anniversary Address of the President, Proc. 41-84. See also Judd, Prof. J. W Annual Report for 1887, Proc. 8. Appletreeworth Beck, section across “ Cliff,” 695; section of Farm, 696. Farm, ashes at, 697 ; felsite dyke at, 697. Archean rocks of the North-west Highlands, 387. Arctic lands, Mesozoic rocks on, 815; Palzozoic climates of, 816. Ardtun, tachylyte from, 300. Ascot, section of Bagshot Beds at Hagthorn Hill, near, 166; in South- Western Railway cutting near, 166. 3K 2 840 Ascot Hills, Bagshot Beds of the, 170. Ashes, at Appletreeworth Farm, 697. Ashgill, section across quarry, 693. Ashgill shales, 660, 665, 680, 698, - 694, 700. Assynt, succession of Cambrian rocks in, 401. aon Atrypa flexuosa, : ‘ni , zone of, 661, 665, 686, 687, 694, 700. Attwood, Mr. G., on some of the Auri- ferous tracts of Mysore province, Southern India, 636. Auriferous tracts of Mysore province, Southern India, Mr. G. Attwood on some of the, 636. Austwick Beck, Stockdale shales on, 706. Bagshot Beds of the London Basin, Rey. A. Irving on the stratigraphy of the, 164. sands, Lower, 105. Ball, Mr. Valentine, on some eroded Agate pebbles from the Soudan, 368. , on the probable mode of trans- port of the fragments of granite and other rocks which are found imbedded in the Carboniferous Limestone of the neighbourhood of Dublin, 371. Bangor, Pre-Cambrian rocks near, 533; Trilobites in the Upper Green (Cambrian) Slates of the Penrhyn Quarries, Bethesda, near, 74. © and Caernarvon, map of the district between, 272. and Caernarvon area, Cam- brian and associated rocks in the, 273. Barkham Hill, section in pits on, 176. Barlow, Mr. W., on the horizontal movement of rocks, and the relation of these movements to the formation of dykes and faults, and to denuda- tion and thickening of strata, 783. Barren Band of the Skelgill beds, 672, 682, 684. Barton, fauna of the, 618. -~—., Lower, or Highcliff Beds, 587 ; fauna of, 588. Clay, or Middle Barton, 588; fauna of, 589. Cliff, section of the, 594. —— series, 579, 582; of the London area, 606. Barton-on-Humber, succession of Cre- taceous beds at, 330. Basalt-dykes in Archean gneiss of North-west Highlands, 390. GENERAL INDEX. Basement Bed of the London Clay, 102; Mollusca of the, 103. Bavaria, Graptolites of Stockdale Shales from, 712. Bealloch, section from the, across Coinne-mheall to Corrie Mhadaidh, 421. Bearwood Hills, Bagshot beds of, 176. Beaufort West, intrusive trap-sheet at, 254 ; section through, 270. Becton-Bunny Beds, 591; section of, 592. Bedford, Mr. R. Lydekker on the skeleton of a Sauropterygian from the Oxford Clay near, Proc. 89. Beinn Lice, sections through, 415. —— Suardal, fossils from the Lime- stone of, 69. Belemnitella plena, zone of, in Lin- colnshire, 329; in Yorkshire, 346. Belemnite-marls in Lincolnshire and Yorkshire, 363. , minute structure of the, 357. Belgium, Prof. Prestwich on the cor- relation of the Hocene Strata in England, the north of France, and, 88. Belonostomus cinctus, 145. Ben Aird da Loch, section through, 417. Ben Arkle, section across, to the Moine thrust-plane, 415. Ben Dreavie, section through, 415. Ben Fhuarain, section through, 424. Ben More, general structure of, 421; section from the Oykel valley, across, 423. thrust, 412, 418, 419, 422, 423, 427, 428, 480, 431, 482, 433, 435. —————— thrust-plane, section from Quinaig to the, 418. Ben Uidhe, section through, 418. Bethesda, near Bangor, Dr. H. Wood- ward on Trilobites in the Upper Green (Cambrian) Slates of the Penrhyn Quarries at, 74. Birkhill Shales, comparison of, with Skelgill Beds, '706, 709. - Black Rock of Clifton, insoluble resi- dues from the, 190. Blake, Prof. J. F., on the Cambrian and associated rocks in North-west Caernarvonshire, 271. , on the Monian system of rocks, 463. Blocks, ejected, of Monte Somma, Dr. H. J. Johnston-Lavis, on the, Proc. gl. Bodafon Mountain, rocks of, 499. GENERAL INDEX. Bohemia, equivalents of Stockdale Shales in, 712, 713. Bokkeveldt Beds, 214. Bollerup, Graptolites of, 711. Bonney, Prof. T. G., on some results of pressure, and of the Intrusion of Granite in Stratified Paleozoic Rocks near Morlaix in Brittany, i. , on the Obermittweida Conglo- merate, its composition and altera- tion, 25, , on a part of the Huronian series in the neighbourhood of Sudbury (Canada), 32. ——, on the “‘intrusive syenite” of Glen Logan, 384. , Note on specimens from Mysore, collected by G. Attwood, EHsq., 651. Borth Saint, quartzite of, 478; view in, 479 Wen, view of, west side, 521. Bothriospondylus, 59. Boulder-clay, Low-level Marine, of the Dee, Mersey, and Ribble, denu- dation of the, 291. Bracheux, Sables de, 94; Mollusca of the, 96. Bracklesham Beds at Highcliff, 585. Sands, 107. Brady, Mr. H. B., on the so-called “ Soapstone ” of Fiji, 1. Braebag, section through, 424. Braidy Beck, 691. wre Head, Pre-Cambrian rocks of, 530. Breccias of the neighbourhood of Sud- bury, Canada, 38. Breccia-series in the Red rocks of South Devon, 157. _ Bridlington Drift, fossils of the, 120. Britain, comparison of older Paleozoic rocks of, with those of Nova Scotia and New Brunswick, 813. ——, Laurentian in, 800. British Isles, map showing the glacia- tion of the northern parts of the, 828. Brittany, Prof. T. G. Bonney on some results of pressure, and of the in- ‘trusion of Granite in stratified Palzozoic rocks near Morlaix, 11. , Upper Laurentian in, 800. Browgill, section at the “ Rake,” 675; sections in, 679. Beds, comparison of, with Gala Beds, 707, 709. of Browgill and Stockdale, 674. Brown, Mr. Barrington, discovery of 841 rubies in matrix in Burmah, Proc. gl. Bryansford, tachylyte from near, 305. Bryn Efail, plan of quarry at, 283; section in road near, 284; section through, 287. Bryntwrog, brecciated granite of, 495. Budleigh Salterton, Red rocks at, 153 ; section at, 155. , Vertebrate remains in the Triassic strata between Sidmouth and, 318. Buffels-river valley, Dwyka Conglo- merate in the, 243; section in the, 259. Bull-Brook, Bagshot beds of, 165. Burmah, rubies in the matrix from, Proe. 91. Cadell, Mr. H. M., see Geological Survey. Cae Gwyn Cave, Prof. T. M‘K. Hughes on the, 112. ——, N. Wales, Dr. H. Hicks on the, 561; Mr. C. BE. De Rance on the, 576. , fossils of Drift at, 120; views of portions of the, 119, 124, 125, 126; sections in the, 127, 128 ; plans of the, 185, 573; section across shaft, showing the continua- tion of the beds over the entrance, 5638; flint-flake found under Drifts, outside the covered entrance, 564 ; section at north-east end of excava - tion, October 1887, 570; section through, 574. Caerfai Beds, 803, 804. Caernarvon and Bangor, Map of the district between, 272. Area, Cambrian and associated rocks in the, 273. Caernarvonshire, Arenigs of, 275 ; Mr. A. Harker on the eruptive rocks in the neighbourhood of Sarn, 442; Pre-Cambrian rocks in, 533; Prof. J. K. Blake on the Cambrian and’ associated rocks in north-west, 271. Caistor, succession of Cretaceous beds at, 329. Calcaire de Mons, 90. Calcisphzree, Mr. E. Wethered on the occurrence of, in the Carboniferous Limestone of Gloucestershire, Proc. gi. California Brick-yard, clay-pit in, 172. Callaway, Dr. C., on the geology of the North-west Highlands, 384. Camawg, Pre-Cambrian rocks at, 471. 842 Cambrian, relation of, to the Lime- stone of Strath, Skye, 70. and associated rocks in North- west Caernarvonshire, Prof. J. F. Blake on the, 271. —— of Wales, fossils of the, 74. rocks, in the north-west High- lands, 400; in the Parph district, 401; in Assynt, 401; in the Loch- Broom district, 402; formation of outliers of, by folding and denu- dation, 402, 403. strata, metamorphism of ig- neous rocks intrusive in, 434; of the North-west Highlands, meta- morphism of, 431; on Coinne- mheall, alterations of, 438. system of Canada, Western Europe, and the interior of America, 804. —— Upper Green Slates, discovery of Trilobites in the, of the Penrhyn Quarries, Bethesda, near Bangor, Camdeboo Mountains, section through, | 270. Canada, Eozoic and Paleozoic rocks of the Atlantic coast of, in compa- rison with those of Western Europe and of the interior of America, Sir J. W. Dawson on the, 797. ——, Prof. Bonney on a part of the Huronian Series in the neighbour- hood of Sudbury, 32. Canisp, section from to Sgonnan More, 424. Cape Breton, Laurentian in, 799. Cape Colony, Prof. A. H. Green on the Geology and Physical Geo- graphy of the, 239. , section showing the general geulogical structure of the, from the Zwarteberg to the Stormberg Moun- tains, 256, 270. Cape Town, generalized section from, to the Transvaal, 256, 270. Carboniferous Limestone near Dub- lin, probable mode of transport of fragments of granite and other rocks found imbedded in the, 371. of Gloucestershire, occur- rence of Calcispherz in the, Proc. gi. Series, insoluble resi- a obtained from the, at Clifton, 86. system, of Canada, Western Europe, and the interior of Ame- rica, 814. — times, Mr. J. Spencer on eyvi- dence of ice-action in, Proc. 93. GENERAL INDEX. Careg Gwladys, volcanic group of, 509; view of rock at, 510; section on west side of, 511; section look- ing north, 512. Caer: new, from the Red Crag, 28. Carter, Mr. H.J., on some Vertebrate Remains in the Triassic strata of the south coast of Devonshire, be- tween Budleigh Salterton and Sid- mouth, 318. Cave, Cae Gwyn, Prof. T. MK. Hughes on the, 112; Dr. H. Hicks on the, 561. Cave Sandstone of the Stormberg series, 253. Cefn-amlwch, section in quarry at, Cefn-eth-groen, junction of granite and pelite at, 494; section at, 494. Cemmaes, disturbed volcanic series” near, 518. Central District of Anglesey, 485, 501. Cerrig Ceinwen, section in quarry near, 488. Cetiosauria, 86. Cetiosaurus, 58. brevis, 56. Chalcedony in greensand at base of Thanet Sand, 758. Chalk, condition of the, on the brow of the Yorkshire Wolds, 3382. , Squatina Cranei and the man- dible of Belonostomus cinctus, from the, of Sussex, 144. and ‘Tertiaries, unconformity between, 759. Ohalk-escarpment, section of, at Dew- lish, Dorset, 819. Chalk-Marl, in Lincolnshire, 324; fossils from the, in Norfolk, Suffolk, and Lincolnshire, 349; in York- shire, 351; in Lincolnshire and Yorkshire, 361; minute structure of the, in Lincolnshire and York- shire, 355. Chama-beds, 590; fossils of the, at Whitecliff Bay, 605. Champernowne Memorial, Proc. 86. Charnwood Forest, Huronian rocks in, 802. Cheirurus bimucronatus, var. acan-= thodes, 722. moroides, 722. Chemical composition of the Chalk in Lincolnshire and Yorkshire, 357. Chobham, Bracklesham beds of, 609. — Ridges, 609; Bagshot beds of, 164. Church Hill, Finchampstead, Bagshot beds of, 173. GENERAL INDEX. Clayton, Yorkshire, discovery of Stig- maria ficoides at, 375. Clegyr, section through, 287. Cleithrolepis Extoni, 141, Clidgas Rocks, greenstone from, 315. Clifton, insoluble residues obtained from the Carboniferous Limestone Series at, 186. Olough, Mr. ©. T., see Geological Survey. Cnoe an Droighinn, section from Loch Assynt to, 420. Cnoc an Fhuarain Bhain, section from Glendhu to, across the Stack of Glencoul, 417. Coal-measures of Fife, Mr. J. W. Kirkby on the occurrence of marine fossils in the, 747; vertical section of the, 748. of Nova Scotia, 815. Coals, South-African, 249; analyses of, 251. Coinne-mheall, alterations of Cambrian strata on, 433; sections across, 421, Cole, Mr. G. A. J., on some additional occurrences of tachylyte, 300. Colesberg, trap at, 254. Collins, Mr. J. H., on the Sudbury Copper-deposits, 834. Colonies, Secretary of State for the, letter relating to discoveries of Gold in the Transvaal, Proc. 3. Coloured bands in the Cretaceous de- posits in Lincolnshire and York- shire, 353. Colwyn Drifts, fossils of the 120. Conglomerate, Obermittweida, Prof. Bonney on the composition and alteration of the, 25; Prof. Hughes on the position of the, 20. — of Twt-Hill, age of the, 275. and Porphyry, plan of junction of, in Twt-Hill Field-quarry, Caernaryon, 273. Coniston, 688. Limestone, 675, 696. Conocoryphe viola, 77. Contact metamorphism in Cambrian and Silurian rocks of the North- west Highlands, 410. Copper Cliff, Sudbury, section of ore- deposit at, 835. Corals of the Stockdale series, 720. Corniferous Limestone, 813. Corrie Mhadaidh, section from one of the sources of the Traligill to, across Coinne-mheall, 421; section from the Bealloch to, 421. Crag, Red, a new Carnivore, Ailurus anglicus, from the, 228. 843 Oraig Cocyn, contact of granite and hornblende-schist at, 494. Craig Wen, 521. Craig yr-allor, dioritic rocks near, 498 ; granite near, 495. Cretaceous rocks, map of the outcrop of, in Lincolnshire and Yorkshire, BY series, Upper, Mr. W. Hill on the lower beds of the, in York- shire and Lincolnshire, 320. Cromalt, section through, 426. Hills, section from the Knockan Cliff to the, 427. Crossopodia-group, 709. Oumnoria, 47. Cunningham, R. J. H., on the geo- logy of Sutherland, 380. Currents, transporting action of, 733. Cyrtograptus Graye, band of, 705, 710. Dalton-in-Furness, Stockdale Shales near, 697. Davison, Mr. C., on the movement of Scree-material, 232, 825. Dawkins, Prof. W. Boyd, on Adlurus anglicus, a new Carnivore from the Red Crag, 228. Dawson, Sir J. W., on the Eozoic and Paleozoic rocks of the Atlantic coast of Canada, in comparison with those of Western Europe and of the interior of America, 797. De Beer's mine, Kimberley, trap at, 254. Dee, Mersey, and Ribble, denudation of the low-level Marine Boulder- clay of the, 291. De Rance, Mr. C. E., on the Cae Gwyn Cave, 576. Denudation of the Land-surface in the Highlands, 400. , relation of horizontal move- ments of rocks to, 783. of old land-surface before deposition of Old Red Sandstone, 438. Devon Coast-section, Rev. A. Irving on the Red-rock series of the, 149. Devonian or Erian of Canada, Wes- tern Europe, and the interior of America, 813. Devonshire, Mr. H. J. Carter on Vertebrate Remains in the Triassic strata of the south coast of, 318. Dewlish, Dorset, Rev. O. Fisher on the occurrence of Elephas meridionalis at, 818. Dharwar Rock, 649. Pre-Cambrian North-west 844 ‘“Dhone” or sluice-box, for gold- washing, 648. Diabase of the Sarn district, 448. , Hornblende-, of the district, 450. Dimetian of Laurentian age, 800. Dimorphograptus-confertus zone, 662, 665, 680, 683, 686, 687, 688, 693, 694, 698, '700, 707, 715. Dimorphograptus confertus, zone of, in Skelgill beds, represented by the zone of Diplograptus vesiculosus in Birkhill shales, 707. Dinas Dinorwice, section from, to Llyn Padarn, 287. Dinas Llwyd, disturbed masses near, 489; section on west side of, 489. Dinas Mawr, section through, 287. Dinosauria, Prof. H. G. Seeley on the classification of the, 85. Dinosaurs, Mr. R. Lydekker on some, Sarn Diorite, formation of “eyes” of, in Hornblende-schist, 392. , metamorphosis of, into horn- blende-schist, 392. of the Sarn district, 447. Diorites of central Anglesey, 497. Diplograptus acuminatus, zone of, in Browgill, 680; at base of Birkhill shales, comparison of, with same zone in Skelgill beds, 707. vesiculosus, zone of, in Birk- hill shales, represented by the zone of Dimorphograptus confertus, in Skelgill beds, 707. Directions of Ice-flow in the north of Ireland, Mr. J. R. Kilroe on the, 827. Dolerite-dyke, formation of “eyes” of diorite in, 392. Dolerite-dykes of the Sarn district, 460. in Archean gneiss of North- west Highlands, 389. Donations to the Library and Mu- seum, Proc. 97. Donegal, Dr. F. H. Hatch on the spheroid-bearing granite of Mul- laghderg, 548. Dordrecht, S. Africa, intrusive trap- sheet at, 254. Dorset, Rev. O. Fisher on the occur- rence of Hlephas meridionalis at Dewlish, 818. Down, tachylyte from, 305. Downton Sandstones, 814. Drifts of North Wales, fossils of the, 120. Dublin, Mr. V. Ball on the probable mode of transport of the fragments GENERAL INDEX. of granite and other rocks found imbedded in the Carboniferous ria of the neighbourhood of, 71. Durham Salt-district, Mr. E. Wilson on the, 761; map of the, 762; area of the, 773. Durness Limestone, American type of fossils in the, 806. and Eriboll, section of Si- lurian at, 404. Dusky Sound, New Zealand, Capt. F. W. Hutton on a hornblende- biotite rock from, 745. Dwyka conglomerate, 241; at Gra- hamstown, 242; on the Witte- bergen, 243; in the Buffels River valley, 243. Dyke, basic, in Man-of-War Rocks,311. a at Appletreeworth Farm, 697. in Quadrant Island, 313. Dykes, dolerite-, of the Sarn district, 460. , formation of, relation of hori- zontal movements of rocks to the, 783. , intrusive, in the Archean rocks of the North-west Highlands, effects of later Pre-Cambrian movements upon, 391. , porphyritic and granitic, in ue Seringaptam area, 647, 648, 649. Eastern District of Anglesey, 503, 513. Easthampstead Plain, Bagshot beds on north flank of, 164. East Hesterton, section of Red Chalk at, 337. cca Beds, near Grahamstown, 244. Eclogite of the Melkote area, 639, 651. Ehrenbergina bicornis, 5. Elephas meridionalis, Rev. O. Fisher on the occurrence of, at Dewlish, Dorset, 818. Elliot lode, 646. Ellipsoidina ellipsoides, var. oblonga, 5. Hlphin, section from, to Allt Halag, 426. Encrinurus punctatus, zone of, 668, 672, 690. England, marine fossils from the coal-measures of, 751. , Prof. Prestwich on the cor- relation of the Eocene strata in Belgium, the north of France, and, 88 ; , Silurians of, 812. Enoch Rock, schist and gneiss from, 3l7. GENERAL INDEX. Hocene series, table of classification of the, 89, 108. strata, Prof. Prestwich on the correlation of the, in England, Bel- Sa and the north of France, ——, Upper, Messrs. J. S. Gardner, H. Keeping, and H. W. Monckton on the, 578. Eozoic and Paleozoic rocks of the Atlantic coast of Canada, in com- parison with those of Western Europe and of the interior of oo Sir J. W. Dawson on the, is Epidosites, Mr. W. F. Rutley on the possible origin of some, 740. Epidote infusions in Pre-Cambrian rocks of Western Anglesey, 475. —— in greensand at base of Thanet Sand, 758. Epidotes, analyses of, 742. Erian or Devonian of Canada, Western aoe and the interior of America, Eriboll and Durness, section of Silu- rian strata at, 404. . and Ullapool], physical rela- tions of the strata between, 411. , Section of Silurian strata from, to Ullapool, 406. Hruptive rocks in the neighbourhood of Sarn, Caernarvonshire, 442. Escarpment of Chalk at Dewlish, Dorset, 819. Hston-on-Tees, South Bank, boring at, section of the, 778, 782. Kuiguanodonts, 51. Kurope, Western, Cambrians of, 805. » — . the Hozoic and Pale- ozoic rocks of the Atlantic coasts of Canada, compared with those of, 797. Far End, Yewdale Beck, section at, 688. Farley Hill, Bagshot beds of, 177. Farnborough, Upper Bagshots at, 612. Faults, formation of, relation of hori- zontal movements of rocks to the, 7838. Fauna of the Lower Beds of the Upper Cretaceous in Lincolnshire and Yorkshire, 352. a of the Upper Bagshot Sand, 8. Felsite-dyke at Appletreeworth Farm, 697. Felsites, perlitic, Mr. F. Rutley on some, from the flanks of the Here- fordshire Beacon, 740. 845 Felspar in greensand at base of Thanet Sand, '757. , section of, from granite of Mullaghderg, 550. — crystals, development of quartz and flakes of mica in, 36. Felstones, porphyritic, from Mysore, characters of, 652. Ffynnon Beuno cave, section in quarry opposite, 132. gorge, caves of the, 113, 561. Fifeshire, Mr. J. W. Kirkby on the occurrence of marine fossils in the Coal-measures of, 747. Fiji, Mr. H. B. Brady on the so-called ‘‘soapstone”’ of, 1. Finchampstead Ridges, Bagshot beds of U7), Fish River, section across, 270. Fisher, Rey. O., on the occurrence of EHlephas meridionalis at Dewlish, Dorset, 818. Fissures, production of, by horizontal movements of rocks, 783. Flint in greensand at base of Thanet Sand, 756, 789. Flint-flake found under drifts outside the covered entrance to Oae Gwyn Cave, 564. Flowing Streams, Mr. R. D. Oldham on the law that governs the action of, 733. Foliation, double, produced by mecha- nical movements in Archzxan gneiss, 397 ; diagram showing, 398. Foord, Mr. A. H., award of one moiety of the Lyell Geological Fund to, Proe. 39. Foraminifera, Post-tertiary, of Suva, Fiji, 8. Fossils, marine, Mr. J. W. Kirkby on the occurrence of, in the Coal- measures of Fife, 747 ; in the Coal- measures of Scotland and England, 750, 751. from the so-called Soapstone of Fiji, 4; Dinosaurian, from the Wealden, &c., 49, 72; from the Limestone of Beinn Suardal, Strath, 69; of the Cambrians, 74; of the Calcaire de Mons, 90; of the Tha- net Sands, Pegwell Bay, 93; of the sands of Bracheux, 96; of the Woolwich and Reading Series, 100; of the Basement-bed of the London Clay, or Oldbaven Beds, 103; of the Bridlington Drift, 120; from the Orange Free State, 138; from the Chalk of Sussex, 144; from the Red Chalk or Hunstanton Lime- stone, 347 ; of the Lower Chalk of 846 Lincolnshire, 348; from the Chalk Marl and Totternhoe Stone in Norfolk, Suffolk, and Lincolnshire, 349; from the Lower Chalk of Yorkshire, 351; from the Upper Bagshot Sand, 616; of the Barton beds, 623; of the Stockdale Shales, 726. Fox, Mr. Howard, on the gneissic rocks off the Lizard, 309. Fox Hills, sections in Upper Bagshot in the, 610, 611. Fragments of granite and other rocks found imbedded in the Carboni- ferous Limestone near Dublin, probable mode of transport of, 371 France, Prof. Prestwich on the cor- relation of the Eocene strata in England, Belgium, and the north of, 88 Frilled Schists, 431, 435. Gabbro of the Sarn district, 447. Gala Beds, comparison of, with Brow- gill Beds, 707. Ganoids, Lepidotoid, from the early Mesozoic deposits of the Orange Free State, 138. Ganton Hall, section of Lower Chalk near, 342. Garbourn Pass, 685. Gardiner, Miss M. I., on the Green- sand bed at the base of the Thanet Sand, 755. Gardner, Mr. J. S., Mr. H. Keeping, and Mr. H. W. Monckton on the Upper Eocene, comprising the Barton and Upper Bagshot for- mations, 578. Garnet in greensand at base of Thanet Sand, 757, 758. Garnets, crushed, in mica-schists of the Melkote area, 640, 641 ; analysis of, 641. , flattened, from Mysore, 651. Garrowby Hall, section of Red Chalk near, 335. Garth Ferry, weathered surface of rock north of, 507. Gault of Norfolk, analysis of, 358. Geikie, Dr. A., on the age of the altered limestone of Strath, Skye, 62. ——, on recent researches in Cae wyn Cave, 571. Geological Survey, report on the recent work of the, in the North- west Highlands of Scotland, based on the field-notes and maps of Messrs. B. N. Peach, J. Horne, GENERAL INDEX. W. Gunn, C. T. Clough, L. Hinx- man, and H. M. Cadell, 378. Glaciation of the northern part of the British Isles, map showing the, 828; North Irish system of, map showing the, 831. Glasven, diagram-section in west face of, illustrating thrusts and reversed faults, 413 ; section through, 418. Glauconite in greensand at base of Thanet Sand, 755; in the green- sand bed at Sudbury, 758. Glenbeg, section through head of, 418. Ghee section across the Stack of, 417. —— thrust, 412, 413, 417, 418, 420, 421, 429, 431, 434, 435. Glendhu, section from, across the Stack of Glencoul, to Cnoe an Fhuarain Bhain, 417. Glyphastrea, Dr. G. J. Hinde on the genus, 200. Gneiss, effects of later Pre-Cambrian movements upon the Archzan, in the North-west Highlands, 395. , original types of, in the North- west Highlands, 387 ; unfoliated igneous rocks in, 388; evidence of mechanical movements in the for- mation of the, 388; igneous rocks injected into the, 389. , granitoid, from Mysore, charac- ters of, 652. Gneisses of Central Anglesey, 497 ; of Eastern Anglesey, 505; of the Mel- kote area, 637, 638, 642; of the Seringapatam area, 644. Gneissic diorite of the Sarn district, 447. granite of the Sarn district, 444. rocks off the Lizard, Mr. H. Fox and Mr. J. J. H. Teall, on the, 309, 314. Gneissoid rock from Mysore, charac- ters of, 651. Gogarth, Pre-Cambrian rocks of, 479. Gold, alluvial, general absence of in Mysore, 650. , discoveries of, in the Transvaal, Proc. 3; mode of occurrence of, in the Melkote area, 648; occurrence of, in the Seringapatam area, 646, 647. Gold-mining, native, in the Melkote area, 643, 649; in the Seringapa- tam area, 646. Gold-washing dish, sketches of a, 648. Grahamstown, Dwyka conglomerate at, 242; Eeca Beds near, 244. , sections through, 263, 270. GENERAL INDEX, Granite, Dr. F. H. Hatch on the spheroid-bearing, of Mullaghderg, Co. Donegal, 548. , normal of Mullaghderg, 548 ; microscopic characters of, 549. ——, fragments of, found imbedded in the Carboniferous Limestone near Dublin, probable mode of transport of, 371. ——, intrusive, in the west of the central district of Anglesey, 490. ——, junction of, with gneiss, diorite, &e., near Gaulchmai, Plas Llanfihan- gel, Tafarn-y-botel, &c., 492, 494. —-— near Ynys-y-fyddlyn, 473; near Llyn Trefwll, 482. —— of Anglesey, nature of the, 495. —— of the Sarn district, 444. paucity of, in Southern India, 650. ——, Prof. Bonney on some results of the intrusion of, in stratified Palzo- zoic rocks near Morlaix, Brittany, ah. ——., veins and belts of, conversion of, into granitoid gneiss, 393. Granites, dykes of, in Archzean gneiss in North-west Highlands, 391. Granitic dyke in the Seringapatam area, 649. Granophyre bosses of Strath, Skye, 72 Graptolites of the Quebec Group, 808. Grasby, succession of Cretaceous heds at, 327. Greatham, boring at, section in, 782. Green, Prof. A. H., on the Geology and Physical Geography of the Cape Colony, 239. Green-earth series of the Bagshot, 183. Greensand bed at the base of the Thanet Sand, Miss M. I. Gardiner on the, 755. Greet’s Hill quarry, section of Red . Chalk at, 335. “Grey Bed” in Lincolnshire, 325. “Grey Beds” in Lincolnshire and Yorkshire, 363. “Grey Bed,” minute structure of the, 356. Grey Chalk, fossils from the, in York- shire, 8351; minute structure of the, 307; of Lincolnshire, 328; in Lin- colnshire and Yorkshire, 363. Grits of the neighbourhood of Sud- bury, Canada, 40. Gualchmai, granite at, 491. Gully Hill, Upper Bagshot section in, 612. Gunn, Mr. W., see Geological Survey. 847 Hagley Heath, 613. Hagthorn Hill, sectionof Bagshot beds at, 166. “ Halagay” or Mysore gold-washing dish, sketches of, 648. Halleflintas of central Anglesey, 496. Hampshire Cliffs, Upper Bagshot Sands in the, 580. Hangklip, trap at, 254. Haplophragmium rugosum, 4. Harker, Mr. A., on the eruptive rocks in the neighbourhood of Sarn, Caernarvonshire, 442. Harpes angustus, 724. —— judex, 723. Hartford Bridge Flats, Upper Bag- shot on, 612. Hassan district of Mysore province, plan of part of the, 637. Hatch, Dr. F. H., on the spheroid- bearing Granite of Mullaghderg, Oo. Donegal, 548. Heath Pool, section of Middle Bagshot strata at 171. Heersian, 91. Hen-blas, granite of, 495. Herefordshire Beacon, Mr. F. Rutley on some perlitice felsites from the flanks of the, 740. Hicks, Dr. H., on the geology of Loch Maree, 383. ——, on the Cae Gwyn Cave, N. Wales, 561. Highclere, Bagshot beds of, 178. Station, Upper Bagshot outlier near, 614. Highcliff Beds, Lower Barton, 587; fauna of, 588. Highlands, North-west, of Scotland, report on the recent work of the Geological Survey in the, 378. Hill, Mr. W., on the lower beds of the Upper Cretaceous series in Lincoln- shire and Yorkshire, 320. Hinde, Dr. G. J., on the history and characters of the genus Septastrea, D’Orbigny, and the identity of its type species with that of Glyph- astrea, Duncan, 200. Hinton Admiral, section of Barton Beds near, 597. Hinxman, Mr. L., seeGeological Survey. Holaster, Mr. A. J. Jukes-Browne on a new species of, 364. Holyhead Island, Pre-Cambrian rocks of, 467. Straits, Precambrian rocks of area north of, 468. Home Secretary, letter from the, ac- knowledging the Society’s address to the Queen, Proc. 1. 848 Hope Town, section through, 270. Hordwell, section at, 595 ; section through the Lower Headon at, 596. Horizontal movements of rocks, Mr. W. Barlow on the, 788. Hornblende, twinned crystal of, 551. Hornblende-biotite rock from Dusky Sound, New Zealand, Capt. F. W. Hutton on a, 745. Hornblende-diabase of the Sarn dis- trict, 450. Horblende-picrite of the Sarn district, 454, Hornblende-schist, formation of eyes of diorite in, 392; from Mysore, characters of, 651; in the Melkote area, 639; origin of, in Eastern Anglesey, 503. Horne, Mr. John, award of the Wol- laston Donation Fund to, Proc. 33+ Horne, Mr. J., see Geological Survey. Howth Hill, Pre-Cambrian rock of, 535. Hudleston, Mr. W. H., on the “ Glen Logan” rock, 384. Hughes, Prof. T. McK., on the posi- tion of the Obermittweida Con- glomerate, 20. ——, on the Cae Gwyn Cave, 112. Hunstanton Limestone, in Lincoln- shire, 324; in Yorkshire, 333; of Lincolnshire and Yorkshire, 359; fossils from the, in Lincolnshire and Yorkshire, 347 ; minute structure of the, 355; analyses of, 358. Huntingbridge, Upper Bagshot beds at, 606. Huronian, formation of, 802. Series, Prof. Bonney on a part of, in the neighbourhood of Sud- bury (Canada), 32. —— System of Canada, Western Kurope, and the interior of America, 801; west of the great lakes, 801. Hutton, Capt. F.W., on a Hornblende- biotite rock from Dusky Sound, New Zealand, 745. Hyle@osaurus, 53. Ice-action, Mr. J. Spencer, on evidence of, in Carboniferous times, Proc. 93. Ice-flow, directions of the, in the north of Ireland, Mr. J. R. Kilroe on the, 827. Igneous rocks in Cambrian and Silu- rian formations of the North-west Highlands, 408 ; their intrusive character, 408 ; their horizons, 408 ; their distribution, 409; characters of, 409; metamorphism caused by, GENERAL INDEX. 410; injected into original Archean gneiss after first foliation, 389; un- foliated in original Archean gneiss, 388; intrusive in Cambrian and Silurian strata, metamorphism of, 434, Iguanodon Dawsoni, 47. Prestwichi, 47. Iguanodont, Wealden, Mr. R. Lydek- ker on a new, 46. Inchnadamff, limestone plateau of, 419. India, Secretary of State for, letter accompanying rubies in the matrix from Burmah, Proc. 91. , Southern, Mr. G. Attwood on | some of the auriferous tracts of Mysore province, 636. Intrusion of Granite in stratified Paleozoic rocks near Morlaix, Brittany, Prof. Bonney on some results of the, 11. of igneous rocks in Cambrian and Silurian formations of the North-west Highlands, 408, 410. ireland, Directions of Ice-flow in the north of, Mr. J. R. Kilroe on the, 827. , map of the north of, showing the North-Irish system of glaciation, 831. Irving, Rev. A., on the Red-Rock series of the Devon Coast-section, 149. —~—., on the Stratigraphy of the Bag- shot beds of the London Basin, 164. Ischyrosaurus, 57. Johnston-Lavis, Dr. H. J., on the ejected blocks of Monte Somma, Proc. 94. Judd, Prof. J. W. (President), Address on presenting the Wollaston Gold Medal to Mr. H. B. Medlicott, Proc. 32; Address on handing the Balance of the Wollaston Donation Fund to Dr. A. Geikie for transmis- sion to Mr. John Horne, Proce. 33; Address on handing the Murchison Medal to Dr. A. Geikie for trans- mission to Prof. J. S. Newberry, Proc, 34; Address on handing the Balance of the Murchison Geological Fund to Dr. H. Woodward for transmission to Mr. E. Wilson, Proc. 36; Address on presenting the Lyell Medal to Prof. H. A. Nicholson, Proc. 37; Address on presenting one moiety of the Lyell Geological Fund to Mr. A. H. Foord, GENERAL INDEX, Proc. 39; Address on presenting the second moiety of the Lyell Geo- logical Fund to Mr. T. Roberts, Proc. 39. Anniversary Address, February 17, 1888, Obituary Notices of Deceased Fellows :—Mr. Arthur Champernowne, Proc. 41; Mr. John Edward Lee, Proc. 42; Rev. Wil- liam 8. Symonds, Proc. 43; Sir William Vernon Guise, Proc. 44; Rev. A. H. Winnington Ingram, Proc. 45; Sir Julius von Haast, Proc. 45; Mr. Charles Henry Wil- son, Proc. 47; Mr. Alfred Morris, Proc. 47; Mr. Robert George Bell, Proc. 47; Mr. Rooke Pennington, Proc. 48 ; Baron de Basterot, Proc. 48; Mr. Edward T’Anson, Capt. W. H. Breton, Mr. G. EH. Eyre, the Rev. Lord Charles Harvey, Mr. A. Crichton, Mr. James Baber, Dr. John Millar, Proc. 48 ; Prof. Bern- hard Studer, Proc. 49; Prof. Lau- rent-Guillaume de Koninck, Proc. 50; M. Jules Desnoyers, Proc. 51 ; Dr. Ferdinand v. Hayden, Proc. 52; Count Marschall, Proc. 53.— Address on the work done by the Society and its Fellows, on the pro- gress of Geology, and on the relation between Palzontology and Geology, Proc. 53. Jukes-Browne, Mr. A. J., on a new species of Holaster, 364. Kammannassie Bergen, section through the, 270. Karoo Beds, 245. —— Desert, section through the, 270. Keeping, Mr. H., Mr. J. S. Gardner, and Mr. H. W. Monckton on the Upper Eocene, comprising the Bar- ton and Upper Bagshot formations, 578. Keiskama river, section across, 270. Kentmere, sections of Stockdale Shales in, 684. Kewenian series, 803. Kilmelfort, tachylyte from, 303. Kilroe, Mr. J. R., on the Directions of ." in the north of Ireland, 827. Kimberley, section through, 270. ——, trap at De Beer’s mine, 254. Shales, 244. King William’s Town, section through, 263, 270. Kirkby, Mr. James W., on the occur- rence of Marine fossils in the Coal- measures of Fite, 747. 849 Knap-Hill Asylum, outlier of Upper Bagshot near, 610. Knock, Stockdale Shales near, 699, Knockan Cliff, section from the, to the OCromalt Hills, 427. “Kunker” of the Melkote area, 642; analysis of, 642. Kurck, Baron, on the Graptolites of Bollerup, 711. Labham Reefs, gneissose and schistose rocks from, 317. —— Rock, granulitice rocks of, 317. Laccolite of Mynydd Penarfynydd, 458, 459. Lake District and Moffat area, equi- valence of Graptolitic zones in the, 709. Landenian, Lower, 91; Mollusca of the, 93. Land-surface, Cambro-Silurian, de- nudation of the, in the North-west Highlands, before the deposition of the Old Red Sandstone, 438, Langwell, section at, 427. Lapworth, Prof. C., on the North- west Highlands, 385. Laurentian system of Canada, Western Europe, and the interior of Ame- rica, 798. Lavas, subaerial, of the Stormberg series, 255. Leavening, section of Lower Chalk at, 341 ; section of Cretaceous deposits at, 366. Lepidotoid Ganoids from the early Mesozoic deposits of the Orange Free State, 138. Lewisian, 800. Lias, relation of, to the limestone of Strath, Skye, 71. _ Limestone, altered, of Strath, Skye, 62; under the Salt in Durham, anaiyses of, 763. —— plateau at Inchnadamff, 419, Limestones, sporadic, in the pelites of Anglesey, 476, 488, 508. Lincolnshire, general succession of the Lower beds of the Upper Cretaceous in, 331. ——, South and Central, sections of Upper Cretaceous beds in, 366. ——, stratigraphy of the Upper Cre- taceous series in, 322. —— and Yorkshire, Mr. W. Hill on the lower beds of the Upper Creta- ceous series in, 320. Lithology of the Limestone of Strath, Skye, 65. Lizard, Mr. H. Fox and Mr. J. J. H. 850 Teall on the Gneissic rocks off the, 309, 314. Llanbadrig, coast near, 518. Llanberis, Pre-Cambrian quartz-felsite of, 533. Llandovery, occurrence of Stockdale fossils in the, 713. Llandrygarn, dioritic rocks of, 498; granite of Hen-blas, near, 495. Llaneilian, 516. Llanerchymedd, rocks near, 501. Llanfaelog, granite of, 495. Llanfechell Grit, 515. Llanfihangel, dioritic rock near, 499. Llangaffo cutting, section in, 505. Llangefin, agglomerates near, 487. Lleyn Peninsula, Monian rocks in the, 530. Llyn Padarn, section from Dinas Di- norwic to, 287. —— —— and Moel Tryfaen, conglo- merate &e. of, 281. Llyn Trefwll, granite near, 482; plan of ground west of, 485. Loanan river, section by the, 424. Loch Assynt, section from, to Cnoc an Droighinn, 420. Loch-Broom district, succession of Cambrian rocks in, 402. Loch Glendhu, microcline-mica dyke in Archeean gneiss at, 390; section between Strath nan Carran and, 415. Loch Leathaid Bhuain, through, 415. Loch More, section of the ground between, and Strath nan Carran, 415. Loch na Cagrach, section through, 417. Londesborough, sections of Lower Chalk near, 340, 346. London area, Barton series of the, 606. —— Basin, Rey. A. Irving on the stratigraphy of the Bagshot Beds of the, 164. ——, Upper Bagshot Sands in the, 580. Clay, 105 ; basement bed of the 102; Mollusca of the, 103. Long-Mead-End Sands, 593. Longmore, well-section at, 173. Longmynd, Monian rocks in the, 542. Louth, section of Cretaceous beds near, 327. Lower Bagshot sands, 105. —— Barton, or Highcliff Beds, 587 ; fauna of, 588. Browgill beds, 676, 678, 685, 687, 692, 699. section GENERAL INDEX. Lower Chalk in Yorkshire, 338, 339 of Lincolnshire, fossils from the, as ; of Yorkshire, fossils from the, File —— Headon, section through, at Hordwell, 596. —— Limestones of Clifton, organisms from the, 187. — — Limestone Shales of Clifton, in- soluble residues from, 190. Lower Skelgill beds, 660, 665. Lydekker, Mr. R., on a new Wealden pierce and other Dinosaurs, , on the skeleton of a Sauroptery- gian from the Oxford Clay, near Bedford, Proc. 89. Lyell Geological Fund, award of the, to Mr. A. H. Foord and Mr. T. Roberts, Proc. 39. —— Medal, award of the, to Prof. H. Alleyne Nicholson, Proc. 37. Macculloch, John, on the North-west Highlands, 379. Maen Gwyn Farm, plan of, 493. Maen-yr-esgyll quartzite, 478. Magnetite im greensand at base of Thanet Sand, 757. Malmesbury beds near Cape Town, 240, 241. Malverns, Huronian in the, 802; Upper Laurentian in the, 800. Malvin, gneiss from, 317. Man-of-War Rocks, 309, 310, 311. SSS , gneiss and greenstone from, 315. Map of the district between Bangor and Caernaryon, 272. =a of the Durham §Salt-district, of the Lizard and adjacent rocks and reefs, 316. —— of the Outcrop of Cretaceous Rocks in Lincolnshire and York- shire, 321. —— of the Sarn district, 443. —-— showing glaciation of the north- ern parts of the British Isles, 828 ; of the North of Ireland, showing the North-Irish system of glaciation, 831. showing the position of some of the auriferous lands in Mysore pro- vince, 636. —— showing Upper Bagshot Sands of Bagshot area, 616. showing glaciation of the northern parts of the British Isles, 828. —— of the north of Ireland, showing GENERAL INDEX. the North-Irish system of glacia- tion, 831. Marine fossils, occurrence of, in the Coal-measures of Fife, 747. Marr, Mr. J.E., and Prof. H. A. Nichol- son on the Stockdale Shales, 654. Mealy Gill, section in, 689. Medlicott, Mr. H. B., Award of the Wollaston Gold Medal to, Proc. 32. Megalosaurus, 59. Meirings Poort, section in, 257. Melin Ddrydwy, section on west side of stream at, 491. Melkote area, 637 ; plan of the, 687 ; section of the, 638; rocks of the, 637, 649. Men Hyr, gneissose rock from, 314. Mén Par, gneissose rock of, 317. Mersey, Dee, and Ribble, denudation of the Low-level Marine Boulder- clay of the, 291. Mesozoic deposits, early, of the Orange Free State, two new Lepidotoid Ganoids from the, 138. —— rocks, deficiency of, in Hastern Canada, 815. Metamorphism of Oambrian strata in the North-west Highlands, 431 ; of, Silurian strata, 433. —— ofthe Igneous rocks intrusive in the Cambrian and Silurian strata of the North-west Highlands, 434. —— produced by intrusive rocks in the Cambrian and Silurian strata of the North-west Highlands, 410. Mica, development of flakes of, in felspar crystals, 36. Micaceous layers, overfolding of, along thrust-planes in Archean gneiss, 397. Mica-schists of astern Anglesey, 505. —— of the Melkote area, 638, 639, 640, 641, 649. . Microcline-mica, conversion of, into mica-schists, 393. —— dyke in Archean gneiss at Loch Glendhu, 390. Middle Barton, or Barton Clay, 588 ; fauna of the, 589. —— Chalk in Lincolnshire and York- shire, 364 ; minute structure of the, 357. —— Limestones of Clifton, organisms from the, 188; insoluble residues from the, 191. —— Skelgill beds, 665, 672, 687, 702. Middlesborough, borings at and near, 761, 763, 764, 765; boring oppo- site, section of the, 779, 782. 851 Middlesborough, discovery of Rock- salt at, 761, 766. Minute structure of Cretaceous beds in Lincolnshire and Yorkshire, 354. Mitcheldeania Beds, insoluble residues from, 191. Moel Tryfaen, Pre-Cambrian quartz- felsite of, 5383. Moel Tryfaev and Llyn Padarn, Con- glomerate &e. of, 281. Moffat area and Lake District, equi- valence of Graptolitic zones in the, 706, 709, Moine thrust, 412, 414, 416, 418, 423, 425, 426, 428, 430, 434, 485, 486. thrust-plane, section across Ben Arkle to the, 415; succession of strata above the, 436. Molteno, section through, 270. —— Beds, 246 ; coals of the, 248. Monckton, Mr. H. W., Mr. J. S. Gardner, and Mr. H. Keeping on the Upper Eocene, comprising the Barton aud Upper Bagshot forma- tions, 578. Monian system of rocks, Prof. Blake on the, 463. system, arrangement of groups in the, 536; table of distribution of the rocks of the, 5389; subdivisions of the, 541; development of, in other areas, Longmynd, St. David’s, Wrekin, 542. Monograptus argenteus, zone of, 669, 672, 690. — Clingani, band of, 678, 674, 682, 684, 695, 698. , band of, in Skelgill Beds and Birkhill Shales, 708. convolutus, zone of, 671, 672, 680, 684, 688, 695, 702. crispus, zone of, 677, 678, 685, 687, 690, 692, 692, 699, '705; zone of, in the Gala Group, 709. Jimbriatus, zone of, 667, 672, 680, 685, 686, 689, 695, 699, 702. , argentcus, and convolutus, zones of, in the Skelgill Beds, re- presented by the zone of M. gre- gartus in the Birkhill Shales, 707. gregarius, zone of, in Birkhill Shales, represented by the zones of M. fimbriatus, argenteus, and con- volutus in the Skelgill Beds, 707. spinigerus, zone of, 673, 674, 682, 685, 686, 689, 690, 691, 695, 698, 702; zone of, in Skelgill Beds and Birkhill Shales, 708. turriculatus, zone of, 676, 678, 690, 692, 699, 704, 705; zone of, in the Gala Group, 709. a 852 Mons, Calcaire de, 90. Monte Somma, Dr. H. J. Johnston- Lavis on the ejected blocks of, Proc. 94- Morlaix, Prof. Bonney on some re- sults of pressure and of the intrusion of Granite in stratified Palaeozoic rocks near, 11. Morosaurus, 56. ' Mortars in gneiss, Seringapatam area, 646. Morton, Mr. G. H., on recent re- searches in Cae Gwyn Cave, 571. Movement of Scree-material, Mr. C. Davison on the, 282, 825. Movements, horizontal, of rocks, Mr. W. Barlow on the, 783. Mullaghderg, Donegal, Dr. F. H. Hatch on the spheroid-bearing granite of, 548. Murchison, Sir R. I., on the North- west Highlands, 380, 382. Murchison Geological Fund, award of the, to Mr. Edward Wilson, Proc. 36. Medal, award of the, to Prof. J. S. Newberry, Proc. 34. Mynydd Llwyddiart, area south-west of, 509. Penarfynydd, section through southern end of, 458. Roscolyn, section in gorge below, 478. Mysore, Prof. Bonney on specimens from, 651. plateau, general characters of the, 650. province, Mr. G. Attwood on some of the Auriferous tracts of, 636. Nanny Goat’s House, Speeton, section of cliffs near, 366. Narasimha Temple, section through, 638. Newberry, Prof. J. S., award of the Murchison Medal to, Proc. 34. New Brunswick, Cambrians of, 804; comparison of older Palzeozoic rocks of, with those of Britain, 813; Huronian of, 802, 803; Laurentian in, 799, 800; Ordovician in, 807, 811; Silurians of, 812. Newfoundland, Cambrians of, 804, 805; Huronian rocks of, 801, 803; Laurentian rocks of, 799; Silurian rocks of, 811; Quebec group in, 807 ; Trenton Limestone in, 807. New Zealand, Capt. F. W. Hutton on a hornblende-biotite rock from Dusky Sound, 745. GENERAL INDEX. Nicholson, Prof. H. A., award of the Lyell Medal to, Proc. 37. , and Mr. J. HE. Marr on the Stockdale Shales, 654. Nicol, James, on the Highlands, 380. Nieuwvyeldt mountains, section through the, 270. Nodosaria longiscata, 6. Norfolk, analysis of Gault of, 358. , section of Upper Cretaceous beds in north-west, 366. Northern district of Anglesey, 513, 523. North Ormesby, boring at, 765; section in, 782. Norway, occurrence of Stockdale- shale fossils in, 713. Nova Scotia, Cambrians of, 805; Ordovician in, 807 ; Carboniferous series in, 814, 815; comparison of older Paleozoic rocks of, with those of Britain, 813; Silurian rocks of, 811; Triassic Red Sandstone of, 815. Nummulite-band at base of Barton series, 587. Nummulites elegans, zone of, fossils of the, at Whitecliff Bay, 605. variolarius bed at Selsey, 605. North-west Obermittweida Conglomerate, Prof. Bonney on the composition and alteration of the, 25. , Prof. Hughes on the position of the, 20. , Section across the valley at, 22; matrix of conglomerate of, 26. Ogo-gyfwr, section at, 519. Oldham, Mr. R. D., on the law that governs the action of flowing streams, 733. Oldhaven Beds, 102; Mollusea of the, 103. Old Red Sandstone, 813. ,» denudation of Cambro- Silurian land-surface before the deposition of the, 438. Oliphants River, section across, 270 ; conglomerates of the, 264. Valley, section showing the position of the Conglomerate of the, 257, 270. Orange Free State, South Africa, Mr. A. S. Woodward on two new Lepi- dotoid Ganoids from the early Mesozoic deposits of the, 138. Ordovician System in Canada, Western Europe, and the interior of America, 807. Organic remains in greensand at base of Thanet Sand, 758. GENERAL INDEX, Organisms of the Carboniferous Lime- stone series at Clifton, 187. Ornithischia, 86. Ornithopsis Hulkei, 54. Ostracoda in Foraminiferal deposits in Hiji, 7. Otter Mouth, Red rocks at, 153. Oughton, boring at, 764. Outliers of Cambrian strata, formation of, in Pre-Silurian time, by folding and denudation, 402, 403. Oxford Clay, Sauropterygian from the, near Bedford, Proc. 89. Oykel, river, alterations of Cambrian strata on the, 433. Valley, section from the, across Ben More, 428. Palzontology of the Limestone of Beinn Suardal, Skye, 69; of the Cambrians, 74; of the Calcaire de Mons, 90; of the Thanet Sands, 93 ; of the sands of Bracheux, 96 ; of the Woolwich and Reading series, 100; of the Oldhaven Beds, 103; of the Red Chalk, 347 ; of the Lower Chalk of Lincolnshire, 348; of the Chalk-marl and Totternhoe Stone, 349; of the Lower Chalk of York- shire, 351; of the Upper Bagshot Sand, 616; of the Barton Beds, 623; of the Stockdale Shales, 726; of the Fifeshire Coal-measures, 747. Palzopicrite-dykes in Archzean gneiss of North-west Highlands, 390. Paleozoic rocks, stratified, Prof. Bonney on some results of pressure and of the intrusion of Granite in, near Morlaix, Brittany, 11. and Eozoic rocks of the At- lantic Coast of Canada, in com- parison with those of Western Europe and of the interior of America, Sir J. W. Dawson on the, GOT. Pant-y-bwlet, section in Quarry near, 526. Parph district, order of succession of Cambrian rocks in the, 401. Parys Mountain, Anglesey, district east of, 524, 530. Peach, Mr. B. N., see Geological Survey. Peach, C. W., on fossils in the Dur- ness Limestone, 380, 382. Pebble-bed at base of Upper Bagshot, 608. Pebidian, Huronian age of the, 802. Pegmatites, formation of, in horn- blende-schist and granitoid gneiss, 393. @.I.G.S. No. 176. 853 Pelite, lenticular, 472 ; of Camawg, in Anglesey, 472; of Central Anglesey, 496. Pelorosaurus, 55, 57. Pen-Craig, section from, to south of Sarn, 449. Pen Ervan, gneissose and schistose rocks from, 317. Pen-lon, section in quarry east of, 503. Penrhyn Quarries, Bethesda, near Bangor, Trilobites in the Upper Green (Cambrian) Slates of, 74. Pen-y-parc, Cemmaes, looking east, 518; quartz-knob at, 508. Peridote-dykes in Archzan gneiss of North-west Highlands, 390. Peridotites, conversion of, into talcose schists, 393. Perlitic felsites, Mr. F. Rutley on some, from the flanks of the Here- fordshire Beacon, 740. Permian deposits of the South Devon Coast, 160. and Triassic rocks of the Durham district, classification of the, 767. Petalograptus cometa, zone of, in the Birkhill Shales, 708. Phacops elegans, 720. , var. glaber, 721. — mucronatus, 721. glaber, zone of, 670, 672, 681, 688, 690, 695, 702. Picrite, hornblende-, district, 454. Pipe-rock zone, 403. Pirbright, Upper-Bagshot near, 611. Plan of farmyard of Maen Gwyn, 493. of ground west of Llyn Trefwll, 483. of junction of Porphyry and Conglomerate, in Twt Hill Field- quarry, Caernarvon, 273; of Twt Hill, 274. of quarry at Bryn Efail, 283. — of shore west of Porth-y-ly-wod, 491. — of the Seringapatam area in Mysore, 644. of the district east of Melkote. in the Hassan district of the My- sore province, 637. showing deflection and disrup- tion of dykes by vertical thrust- planes, 394. showing displacement of a quartz-vein, 640. Plans of Cae Gwyn Cave, 135, 573. Plas Llanfihangel, relations of granite and gneiss at, 492. ' 3 L of the Sarn outlier 854 Poaka Beck, Stockdale Shales of, 697 ; section at, 698. Point Alianus, 516. Pont-rhyd-defaid, dioritic rocks near, 498. Porphyritic dykes in the Seringapatam area, 647, 648. felstone, from Mysore, characters of, 652. Porphyry and Conglomerate, plan of junction of, in Twt Hili Field- quarry, Caernarvon, 273, of Llyn Padarn and Moel Try- faen, 282. Port Clarence, boring near, section in, 779, 782. Porth Llanlliana, view in, looking east, 520. —— Llechog, plan of hill-crest west of, 522. — Rhyffydd, cleavage and con- tortion shown at, 481. Porth-y-defaid, Pre-Cambrian rocks at, 468, 472. Porth-y-ly-wod, plan of shore west of, 491. Post-glacial time, Mr. T. Mellard Reade’s estimate of, 291. Potsdam Sandstone, 806. Pre-Cambrian land-surface, denuda- tion of the, in the North-west High- lands, 400. movements, later,in the Archzan rocks of the North-west Highlands, 391,399; effects of, on the intrusive dykes, 391 ; effects of, on the gneiss, 395. rocks of Anglesey, 464, 466; of the Lleyn Peninsula, 530. Pressure, Prof. Bonney on some re- sults of, in stratified Paleozoic rocks near Morlaix, Brittany, 11. Prestwich, Prof. Joseph, on the Corre- lation of the Eocene strata in Eng- land, Belgium, and the north of France, 88. Prince Albert, 270. Prince-Edward Island, Triassic red sandstone of, 815. Proétus brachypygus, 725. Proiguanodonts, 51. Pullan, section through, 426. Pull Beck, Stockdale Shales in, 687. section through, Quadrant Island, 312, 313; granulite and greenstone of, 317. Quartz and flakes of mica, develop- ment of, in felspar crystals, 36. in greensand at base of Thanet sand, 755, GENERAL INDEX. Quartz, micro-crystals of, in the Car- boniferous Limestone at Clifton, 194. knobs in the rocks of Angle- sey, 475, 488, 508; at Pen-y-pare, Beaumaris, 508. Quartzite, slickensides on, 639; of the Melkote area, 640. of the neighbourhood of Sudbury, Canada, 35; of the Zuurbergen, Zwartebergen,and Wittebergen,240, 241. Quartz-rock of the Seringapatam area, Quartz-veins, displacement of, 640; downward attenuation of, in the Melkote area, 643; double faulting of, 644. Quebec Group, 807, 808. Quinaig, section from, to the Ben- more thrust-plane, 418. Quiraing, Skye, tachylyte from, 304. Rastrites maximus, zone of, 703; in Skelgill Beds and Birkhill Shales, 708. Rawthey, river, Stockdale Shales on, 705. Reade, Mr. T. Mellard, an estimate of Post-glacial time, 291. Red beds of the Stormberg series, 253. Red Chalk, analyses of, 358; fossils from the, in Lincolnshire and Yorkshire, 347 ; minute structure of the, 355; in Lincolnshire, 324; in Yorkshire, 333 ; of Lincolnshire and Yorkshire, 359. Red Crag, Ailurus anglicus, a new Carnivore from the, 228. Red-Rock Series.of the Devon coast- section, Rev. A. Irving on the, 149. Regnosaurus, 53. Report on the recent work of the Geological Survey in the North- west Highlands of Scotland, 378. Residues, insoluble, obtained from the Carboniferous Limestone Series at Clifton, 186. Rhosbeirio Shales, 515. Rhyl, fossils of the drift at, 120. Ribble, Dee, and Mersey, denudation of the Low-level Marine Boulder- clay of the, 291. Valley, Stockdale Shales in, Rio Tinto, comparison of ore deposits of, with those at Sudbury, Canada, 836 Roberts, Mr. T., award of one moiety of the Lyell Geological Fund to, Proce. 39. GENERAL INDEX. Rock-fragments imbedded in Carboni- ferous Limestone near Dublin, probable mode of transport of, 371. Rock-mortars in gneiss, Seringapatam area, 646. Rock- salt, discovery of, at Middles- borough, 761, 766. Rocks east of Parys mountain, Pre- Cambrian age of the, 524; eruptive, in the neighbourhood of Sarn, Caer- narvonshire, 442; horizontal move- ments of, Mr. W. Barlow on the, 783; South African, classification of, 240. Roscolyn, South-Stack series near, 477. Rubies, in the matrix, from Burmah, Proc.-9r. Rutile in greensand at base of Thanet Sand, 757. Rutley, Mr. F., on perlitic felsites, robably of Archzean age, from the Pinks of the Herefordshire Beacon, and on the possible origin of some Epidosites, 740. Sables de Bracheux, 94; Mollusca of the, 96. St. Asaph Drift, fossils of the, 120. St. David’s, Monian rocks at, 543. Saleombe Dingle, Red-rocks at, 150. Saliferous rocks of Durham, strati- graphical position of the, 765. Salt, working of, in the Durham district, 776. Salt-district of Durham, Mr. E.Wilson on the, 761; area of the, 773. Saltholme, boring at, section in, 779, 782. Sandhurst, Upper Bagshots at, 613, 614 Sands, Upper Bagshot, 580; Thanet, ereensand at base of, '755. Sanspareil, granulite and greenstone of, 317. Sarn, Caernarvonshire, Mr, A. Harker on the eruptive rocks in the neigh- bourhood of, 442. , section from Pen-Craig to near, district, map of the, 443. Saurischia, 86. Sauropoda, 53, 85. Sauropterygian, Mr. R. Lydekker on the skeleton of a, from the Oxford Clay, near Bedford, Proe. 89. Scandinavia, Huronian in, 802. Scania, representatives of Stockdale Shales in, 710. 85d Scelidosauride, 52. Schists, frilled, 451, 435. Schoorstein Berg, section through the, 270. Scotland, equivalents of Stockdale Shales in, 706. , report on the recent work of the Geological Survey in the North- west Highlands of, 378. , west, marine fossils from the Ooal-measures of, 750. Scree-material, Mr. C. Davison on the movement of, 232, 825. Seaton Carew, borings at and near, 764, 765; sections in, 781, 782. Sections :—across the valley at Ober- mittweida, 22; at Torr Mor, Bore- raig, Loch WHishort, 68; in Allt Leth Slighe, Strath, 71; in Cae Gwyn Cave, 127, 128; in quarry opposite Ffynnon Beuno Cave, 182 ; showing junction of the Budleigh- Salterton Pebble-bed and Permian Marls, 155; of Hocene Beds, Didcot and Winchester Railway, 179; in the valley of the Buffels River, 259; north of Aberdeen, showing the junction of the Karoo and Ecca beds, 261; showing the general geological ‘structure of the Cape Colony from the Zwarteberg to the Stormberg Mountains, 256, 270; generalized, from Cape Town to the Transvaal, 256, 270; showing the position of the Conglomerate of the Oliphants Valley, 257, 270; through Grahamstown and King William’s Town, 263, 270; at Twt-Hill Field- quarry, Caernarvon, 273; in road near Bryn Efail, 284; from Dinas Dinorwic to Llyn Padarn, 287; in Speeton Cliff, 354; of lower beds of the Upper Cretaceous series in North-west Norfolk, South and Central Lincolnshire, and South Yorkshire, and at Leavening and Speeton, 366; of original Archzan gneiss, 389; of overfolding of micaceous layers along thrust- planes in Archean gneiss, 397; showing doublefoliation in Archean gneiss, 398; in the Parph district, 401; of Silurian strata at Durness and Hriboll, 404 ; of Silurian strata from Eriboll to Ullapool, 406; in west face of Glasven near Loch Gamnheach, 413; across Ben Arkle to the outcrop of the Moine thrust- plane, 415; showing structure of ground between Loch More and Strath nan Carran, 415; showing 856 structure of ground between Strath nan Carran and Loch Glendhu, 415; from Glendhu across the Stack of Glencoul to Cnoc na Fhuarain Bhain, 417; from Quinaig east to the Ben- More thrust-plane, 418 ; from Loch Assynt to Cnoc an Droighinn, 420 ; across Coinne-mheall from one of the sources of the Traligill east to Corrie Mhadaidh, 421; from the Bealloch across Coinne-mheall to Corrie Mhadaidh, 421; from the Oykel Valley across Ben More, 423; from Canisp to Sgonnan More, 424 ; from Elphin to Allt Ealag, 426; from the Knockan Cliff to the Cromalt Hills, 427; along Strath Kanaird at Langwell, 427 ; south of Ullapool, 428; of Cambrian strata on Coinne-mheall, 433 ; in the most southerly quarry at Cefn-Amwlch, 446; from Pen-Craig to south of Sarn, 449; through the southern end of Mynydd Penarfynydd, 458 ; in gorge below Mynydd Roscolyn, 478 ; in Borth Saint, Roscolyn, 479 ; showing running of one bed at South Stack, 480; in quarry 14 mile south of Cerrig Ceinwen, 488; on west side of Dinas Llwyd, 489; on west side of stream at Melin Ddry- dwy, 491 ; at Cefn-eth-groen Farm 494 ; in quarry east of Pen-lon, 503; in Llangaffo cutting, 505; showing eastern face of quartz-knob, Pen-y- Pare, Beaumaris, 508; on west side of Careg Gwladys, 511; looking north, Careg Gwladys, 512; at Ogo- gyfwr, 519; in Porth Llanlliana, looking east, 520; of Borth Wen, west side, 521 ; in quarry near Pant- y-bwlet, 526; across Shaft at Cae Gwyn Cave, showing the continua- tion of the beds over the entrance, 568 ; at north-east end of excavation, Cae Gwyn Cave, 570; through Cae Gwyn Cavern, 574; of Becton- Bunny beds, 592; of the Barton Cliff, 594; at Hordwell, west of Long Mead End, 595 ; through the Lower Headon at Hordwell, 596; of the Barton Beds, north face of cutting near Hinton-Admiral, 597 ; of contorted Lower Headon beds, 598 ; at Alum Bay, 599; at White- cliff Bay, 603; at Tunnel Hill, west of Pirbright Common, 611; on the South-eastern Railway near Wel- lington College Station, 614 ; of the Melkote area, 638 ; showing down- ward attenuation of Quartz-vein, GENERAL INDEX. 643; showing double-faulting of a _ Quartz-vein, 644; through the Serin- gapatam area, 645; across Skelgill, 661; at ‘Rake, Browgill, 675; of isoclinal, Browgill, 680; near Stile End, 683; at Far End, Yewdale Beck, 688; in Mealy Guill, 689; in Torver Beck, 691; across Ashgill quarry, 693; across ‘ Cliff,’ Apple- treeworth Beck,695; of Farm, Apple- treeworth Beck, 696; at Poaka Beck, 698; in Spengill, 701; general, of the Stockdale Shales, 706; of the Coal-measures of Fifeshire, 748; of borings in the Durham Salt-district, 778, 779, 780, 781, 782; of Chalk- escarpment at Dewlish, Dorset, 819; of ore-deposit at Copper Cliff, Sud- bury, 835; of ore-deposit at Stobie Mine, Sudbury, 836. Sedimentary series of the Northern district of Anglesey, 514. Seeley, Prof. H. G., on Thecospondylus Daviesi, Seeley, with some remarks on the classification of the Dino- sauria, 79. Selsey, Upper Bagshot beds of, 605. Semionotus capensis, 138. Septaria in the Barton Series, 589. Septastrea, Dr. G. J. Hinde on the history and characters of the genus, 200. Septastrea, 217; sexradiata,219; mul- tilateralis, 222 ; hirtolamellata, 222; ramosa, 223; excavata, 223; dis- par, 223; explanata, 223; Haimei, 224; Fromenteli, 224; Eveshami, 224; crassa, 224; ambigua, 224. — Forbési, 205, 218; mode of growth of, 206; corallites of, 207; septa of, 208; pseudocolumella of, 210; minute structure of, 211. Seringapatam area, rocks of the, 644; plan and section of the, 645. Serpentine masses in Anglesey, 481. Shag rocks, granulitic rocks of, 317. Sharpe, D., on foliation in the North- west Highlands, 380. Sidmouth, Red-Rock series at, 149, 152; Vertebrate remains in the Triassic strata between Budleigh Salterton and, 318. Silica, occurrence of, in the Carboni- ferous Limestones at Clifton, 194, 196. Silurian strata in the North-west Highlands, 403 ; section of, at Dur- ness and Eriboll, 404; section of, from Eriboll to Ullapool, 406; metamorphism of igneous rocks GENERAL INDEX. intrusive in, 434; of the North- west Highlands, metamorphism of, 433. Silurian system in Oanada, Western Europe, and the interior of America, 811. Skelgill, section across, 661. —— beds, comparison of, with Birk- hill Shales, 706. of Skelgill, 659; Lower, 660 ; Middle, 665 ; Upper, 672. Skye, Dr. A. Geikie on the age of the altered Limestone of Strath, 62. , tachylyte from Quiraing in, 304. Sluice-box, Mysorean, for gold-wash- ing, 648. Soapstone, Mr. H. B. Brady on the so-called, of Fiji, 1. Soudan, Mr. V. Ball on some eroded Agate pebbles from the, 368. South Africa, physical structure of, 256. South-African rocks, classification of, South Cave, sections of Lower Chalk &e. near, 339; sections of Red Chalk near, 334, 335. South Stack, section showing running of one bed at, 480. Series, 476, 484. South Thoresby, succession of Creta- ceous beds at, 326. Speeton Cliff, section in, 354. Cliffs, succession of Oretaceous beds in, 345. —., Red Chalk at, 337; sec- tion of Cretaceous deposits at, 366. Spencer, Mr. J., on evidence of ice- action in Carboniferous times, Proc. —_—__— 93. Spengill, Stockdale Shales of, 700; section in, 701. Spheroidina ornata, 6. Sphenospondylus, 46. gracilis, 47. Spheroids of the granite of Mullagh- derg, 552. Spinel in greensand at base of Thanet Sand, 757. Squatina Cranei, 144. Stags, gneissose rocks from the, 315, Staurocephalus limestone, 693. Stigmaria ficoides, My.S. A. Adamson on a recent discovery of, at Clayton, Yorkshire, 375. Stile End, section near, 683. Stobie Mine, Sudbury, section of ore- deposit at, 836. Stockdale, Browgill beds of Browgill and, 674. 857 Stockdale Shales, Mr. J. E. Marr and Prof. H. A. Nicholson on the, 654. Shales, comparison of, with beds in other areas, 706 ; representa- tives of the, in Scania, 710; general characters of the, 714; table of the distribution of the zones of the, 717; formation of the, 718; age of the, 719; fossils of the, 720. Stormberg Beds, 240, 253. Strath, Skye, Dr. A. Geikie on the age of the altered Limestone of, 62. Strath Kanaird, section along, 427. nan Carran, section of the ground between Loch More and, 415; section between, and Loch Glendhu, 415. Stratigraphy of the Limestone of Strath, Skye, 67; of the Upper Cretaceous series in Lincolnshire, 322. Streams, Mr. R. D. Oldham on the law on governs the action of flowing, 33. Stronechrubie, plateau east of, 420. ae ee Upper Bagshot beds of, 606. Sudbury, Greensand bed at, 758. ——., Canada, Prof. Bonney on a part of the Huronian Series in the neighbourhood of, 32. , quartzites of, 35, 41; matrix of conglomerate from, 35; breccias of, 38; grits of, 40. , Mr. J. H. Collins on the copper-deposits of, 834. Sunningdale, Bagshot beds near, 166, 167. Sunny Brow, 687. Sussex, Squatina Cranet and the mandible of Belonostomus cinctus from the Chalk of, 144. Suva, Fiji, foraminiferal deposit at, 2 Swindale Beck, Stockdale Shales of, 699. Swinley, Bagshot beds at, 165. Table-Mountain Sandstone, 241. Tachylyte, Mr. G. A. J. Cole on some additional occurrences of, 300. of Ardtun, analysis of, 303. Tafarn-y-botel, granite in gneiss at, 492. Tarannon Shales, Stockdale-shale Trilobites from the, 714. Taylor’s Rock, gneiss and greenstone from, 315. Teall, Mr. J. J. H., on Rock-specimens collected by Mr. Fox from the islands off the Lizard Head, 314. 858 Teall, Mr. J. J. H., on dykes at Scourie, 386. Tees, boring on south bank of the, opposite Middlesborough, section in the, 779, 782. Mouth, boring at, section in, 782. Valley, discovery of rock-salt in the, 761, 766. Teesdale, Stockdale Shales in, 706. Terrestrial movements, classification of, 412. Tertiaries and Chalk, unconformity between, 759. Tetford Wood, succession of Oretace- ous beds at, 326. Textularia quadrilatera, 5. Thanet Sand, Miss M. I. Gardiner on the greensand-bed at the base of the, 755. Sands, 91; Mollusca of the, 93. Thecospondylus Daviesi, 79. Theropoda, 59. Thickening of strata, relation of horizontal movements of rocks to the, 783. Thorn Hill, Aldershot, Upper Bag- shots at, 612. Thrust-planes, explanation of, 389; deflection and disruption of dykes by, 394. Thrusts, chief maximum, in the North- west Highlands, 412; charac- teristics of, 413. , Ininor, major, and maximum, 412. Time, estimate of Post-glacial, 291. Titanosaurus, 59. Torr Mor, Boreraig, Loch Hishort, section at, 68. Torridon Sandstone, relation of, to the Limestone of Strath, Skye, 70 ; in the North-west Highlands, 400. Torver Beck, section in, 691. Totternhoe Stone, equivalent of, in Lincolnshire, 325 ; fossils from the, . in Norfolk, Suffolk, and Lincoln- shire, 349; in Yorkshire, 351. Tourmaline in greensand at base of Thanet Sand, 758. Traeth Dulas, district west of, 502. Traligill, section from one of the sources of the, across Coinne-mheall to Corrie Mhadaidh, 421. Transporting action of flowing streams, 733. Transvaal, discoveries of Gold in the, PROC Fe. , generalized section from Cape Town to the, 256, 270. Traps, intrusive and contemporaneous, of Cape Colony, 254. GENERAL INDEX. Tremadoc in America, 806. Triassic deposits of the South Devon Coast, 160. and Permian rocks of the Dur- ae district, classification of the, 67. Red Sandstone of Nova Scotia and Prince Edward Island, 815. strata of the South coast .of Devonshire, between Budleigh Salterton and Sidmouth, Mr. H. J. pe on vertebrate remains in the, 18. Trilobites, Dr. H. Woodward on the discovery of, in the Upper Green (Cambrian) Slates of the Penrhyn me Bethesda, near Bangor, 4. Trochodon cantabrigiensis, 47. Troutbeck Valley, sections of Stock- dale shales in, 685. Truncatulina mundula, 7. Trwyn-y-parce, limestone of, 518. Tullberg, Prof., on the Silurian and Cambrian deposits of Scania, 710. Tunnel Hill, section of Upper Bagshot in, 611; fossils from the Upper Bagshot sand of, 616. Twt-Hill field-quarry, section at,273; plan of junction of Porphyry and Conglomerate in, 273; granite of, 533; ground-plan of, 274; age of conglomerate of, 275. Tyn-y-cleout, section through, 287. Ullapool, section of Silurian strata from Eriboll to, 406. and Eriboll, physical relations of the strata between, 411. Upper Bagshot beds, characters of, in London area, 615; in the Albert Asylum well, 608, 609. —— Sand, fossils from the, 616. series, 579. Bartons, 590. — Browgill beds, 677, 678, 687, 692, 693. Limestone of Clifton, insoluble residues from the, 193. Skelgill beds, 672, 674. Vasiler, gneissose rock from, 315. Vectisaurus, 52. Vertebrate remains in Triassic strata between Budleigh Salterton and Sid- mouth, 318. Victoria West, section through, 270. Voleanic group of Careg Gwladys, 509; of the northern district of Anglesey, 517. GENERAL INDEX. Volcanic series of the Lleyn Peninsula, 530. Warfield, Bagshot Beds at, 168. Warter, section of Red Chalk near, 334. Wealden, Mr. R. Lydekker on a new Iguanodont from the, 46. Wellington College, Upper Bagshots at, 613; section on South-western Railway near, 614; well-section at, 614. Welton, succession of Cretaceous beds at, 326. Western District of Anglesey, 467, 484. West Hartlepool, boring at, 764; bor- ing at Saltholme near, section in, 781, 782. Wethered, Mr. E., on insoluble resi- dues obtained from the Carbon- iferous Limestone series at Clifton, 186. ——, on the occurrence of Calci- sphere, Williamson, in the Carbo- niferous Limestone of Gloucester- shire, Proc. 91. Wharram Station, section of Red Chalk near, 336. , Whitecliff Bay, section at, 603. Wick Hill, Clay-pit at, 172. Willowmore, section through, 270. Wilson, Mr. Edward, award of the © Murchison Geological Fund to, Proc. 36. ,on the Durham Salt-district, 761. Wiltshire Rock, granulitic rocks of, 317. Winburg, intrusive trap-sheet at, 254. Wittebergen, Quartzites of the, 240, 241 ; Dwyka Conglomerate on the, 243; section through the, 270. Wolds, condition of the Chalk on the brow of the Yorkshire, 332. Wollaston Donation Fund, award of the, to Mr. John Horne, Proc, 33. 859 Wollaston Gold Medal, award of the, to Mr. H. B. Medlicott, Proc. 32. Woodward, Mr. A. S., on some re- mains of Squatina Cranei, sp. nov., and the mandible of Belonostomus cinctus, from the Chalk of Sussex, 144. , on two new Lepidotoid Ganoids from the early Mesozoic deposits of the Orange Free State, South Africa, 138. Woodward, Dr. H., onthe discovery of Trilobites in the Upper Green(Cam- brian) Slates of the Penrhyn Quarries, Bethesda, near Bangor, North Wales, 74. Woolwich and Reading Beds, 98; Mollusca of the, 100. Worcester, section through, 270. Wrekin, Monian rocks in the, 548. Y Foel, rocks of, 501. Yewdale Beck, Stockdale Shales in, 688. Ynys-y-fyddlyn, Pre-Cambrian rocks near, 473; granite near, 473. Yorkshire, Mr. S. A. Adamson on a recent discovery of Stigmaria Jicoides at Clayton, 375. and Lincolnshire, Mr. W. Hill on the lower beds of the Upper Cretaceous series in, 320; succession of ine Upper Cretaceous beds in, 331. , South, section of Upper Creta- ceous beds in, 366. Ypresian, Lower, 105, 106. Zircon in greensand at base of Thanet Sand, 757. Zuurbergen, quartzites of the, 240, 241 Zwartebergen, quartzites of the, 240, 241; sections through the, 270. END OF VOL. XLIV. Printed by TAYLOR and FRANcIs, Red Licn Court, Fleet Street, ’ . 7 4, oe my : tye ANU Sy i” * i. “ 7 - wy } 4 = : mi ‘ if ation > : > WG E i , r ue nea. dat’ eee 7 eke eat gir WAt. rise) Coil bal area . 1 ae PROCEEDINGS OF THE GEOLOGICAL SOCIETY OF LONDON. SESSION 1887-88. November 9, 1887. Prof. J. W. Jupp, F.R.S., President, in the Chair. James Harvey Hichens, Esq., M.A., Radley School, Radley, near Abingdon, was elected a Fellow, and Professor J. P. Lesley, of Philadelphia, a Foreign Member of the Society. The list of Donations to the Library was read. The President read the following communication from the Home Secretary :— * Whitehall, July 22, 1887. 66 Sir, I have had the Honour to lay before the Queen the loyal and dutiful Address of the President, Council, and Fellows of the Geological Society of London on the occasion of Her Majesty attain- ing the Fiftieth year of Her Reign. And I have to inform you that Her Majesty was pleased to receive the same very graciously. I have the Honour to be, Sir, Your obedient Servant, Heyry Marruews.” “The President of The Geological Society of London, Burlington House, W.”’ The following communications were read :— 1. “ Note on the so-called ‘Soapstone’ of Fiji.” By Henry B, Brady, Esq., F.R.S., F.G.S. VOL, XLIV. a 2 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 2. “On some Results of Pressure and of Intrusive Granite in Stratified Palszozoic Rocks near Morlaix, in Brittany.” By Prof. T. G. Bonney, D.Sc., LL.D., F.R.S., V.P.G-S. 3. ‘On the Position of the Obermittweida Conglomerate.” By Prof. T. McK. Hughes, M.A., F.G.S. 4. “On the Obermittweida Conglomerate ; its Composition and Alteration.” By Prof. T. G. Bonney, D.Sc., LL.D., F.R.S., V.P.G.S. 5. “ Notes on a part of the Huronian Series in the Neighbourhood of Sudbury (Canada).” By Prof. T.G. Bonney, D.Sc., LL.D., F.RB.S., VAI2G.S: The following specimens were exhibited :— Specimens and microscopic rock-sections, exhibited by Prof. T. G. Bonney, D.Sc., F.R.S., V.P.G.S., in illustration of his papers. Specimens exhibited by Prof. T. M¢Kenny Hughes, M.A., F.G.S., in illustration of his paper. November 23, 1887. Prof. J. W. Jupp, F.R.S., President, in the Chair. The List of Donations to the Library was read. The following communications were read :— 1. “Note on a New Wealden Iguanodont and other Dinosaurs.” By R. Lydekker, Esq., B.A., F.G.S. 2. “On the Cae-Gwyn Cave.” By T. McKenny Hughes, M.A., F.G.S., Woodwardian Professor of Geology, Cambridge. The following specimens were exhibited :— Specimens of remains of Bos primigenius, Elephas antiquus, Cervus elaphus (?), Hippopotamus amphibius, Rhinoceros, and a piece of wood, possibly pointed by a blunt instrument, found in digging foundations at 26 and 27 Cockspur Street, S.W., at a depth of be- tween 15 and 20 feet below the surface, exhibited by Messrs. Higgs and Hill, the contractors. Casts exhibited by R. Lydekker, Esq., F.G.S., in illustration of his paper. PROCEEDINGS OF THE GEOLOGICAL SOCIETY, 3 Specimens and photographs exhibited by Prof. T. M°Kenny Hughes, M.A., F.G.S., in illustration of his paper. Sketches by C. E. De Rance, Esq., F.G.S., and photographs and diagrams, exhibited by Dr. H. Hicks, F.G.S., in illustration of his remarks on the Cae-Gwyn Cave. A Special General Meeting of the Society was held at 8 pP.m., when the following Resolution was passed :—‘‘ That this Meeting authorizes the payment of the bills for cleaning, repairing, and redecorating the Society’s House, amounting in all to £512 Is. 6d., and sanctions the sale of such an amount of Stock as may be necessary for that purpose.” December 7, 1887. Prof. J. W. Jupp, F.R.S., President, in the Chair. Alfred Edward Carey, Esq., M. Inst. C.E., 9 Dean’s Yard, West- minster, S.W.; Walter F. Ferrier, Esq., Montreal, Canada; Howard Fox, Esq., Falmouth ; Thomas Freeman, Jun., Esq., St. Augustine’s, Florence, Stoke-on-Trent ; William Horne, Esq., Leyburn, York- shire ; Harold Macandrew, Esq., 8 Nevern Square, Harl’s Court, S.W.; Charles Edward Newton, Esq., 17 Cooper Street, Manchester ; Charles Champion Rawlins, Esq., Armadale, near Melbourne, Vic- toria; Joseph Gurdon Leycester Stephenson, Esq., Assoc. M. Inst. C.K., 6 Drapers Gardens, E.C.; William Thomas, Esq., Tuckingmill, Camborne, Cornwall; and Herbert Frederick Tomalin, Esq., Colombo, Ceylon, were elected Fellows of the Society. The List of Donations to the Library was read. The following communications were read :— 1. “A Letter from H.M. Secretary of State for the Colonies, enclosing an account of recent Discoveries of Gold in the Trans- vaal.” The deposits in which gold has been found, locally known as “‘ banket,” consist of a quartz-conglomerate forming so-called ‘ reefs,” which traverse the veldt parallel to, but at a short distance from, the rocky ridge of Witwatersrand. These masses always dip to the south, but at angles varying from 30° up to 90°. The “ reefs ” are believed to have been discovered by Mr. Struben, an English gentle- man long resident in the country. The “‘ main reef” has been traced for twenty-five or thirty miles, and varies in breadth from 3 feet 6 inches to 15 feet; parallel and branching “reefs” of smaller dimensions have also been found, The yield of gold is said to be a 2 4 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. very variable in different portions of the “ reef,’ samples with from 3 oz. to 4 oz. per ton occurring in close proximity. So far as observation has gone (and the deepest workings have only reached a depth of from 70 to 150 feet), the yield of gold has generally increased as the reefs are followed downwards. Discussion. Prof. T. Rupert Jonzs said the interesting question was the mode of occurrence of the gold, whether in the pebbles, which are of white and dark-grey quartz, or in the matrix of this almondrock-like ‘‘banket.” On this point further information was desirable. 2. “On the Age of the Altered Limestone of Strath, Skye.” By Dr. Archibald Geikie, F.R.S., V.P.G.S. 3. “On the Discovery of Trilobites in the Upper Green (Cam- brian) Slates of the Penrhyn Quarry, Bethesda, near Bangor, N orth Wales.” By Dr. Henry Woodward, F.R.S., V.P.GS. 4, “On Thecospondylus Daviesi, Seeley, with some Remarks on the Classification of the Dinosauria.” By Prof. H. G. Seeley, F.R.S., F.G.S. The following specimens were exhibited :— Specimens exhibited by Dr. Archibald Geikie, F.R.S., V.P.GS., in illustration of his paper. Three specimens of Conocoryphe viola, exhibited by Dr. Henry Woodward, F.R.S., V.P.G.S., in illustration of his paper. December 21, 1887. Prof. J. W. Jupp, F.R.S., President, in the Chair. Joseph Carl August Hall, Esq., Grosvenor House, Swansea ; Edward Wilton Newton, Esq., 4 Cross Street, Camborne, Cornwall; and James William Stroud, M.D., Port Elizabeth, Cape Colony, South Africa, were elected Fellows of the Society. The List of Donations to the Library was read. The President announced that the Fourth Meeting of the Inter- national Geological Congress will be held in London in September next on the 17th and following days. An Organizing Committee has nominated the following Officers :—Honorary President: Prof. T. H. Huxley, D.C.L., LL.D., F.R.S. President: Prof. J. Prest- PROCEEDINGS OF THE GEOLOGICAL SOCIETY, 5 wich, M.A., F.R.S. Vice-Presidents: The President of the Geolo- gical Society, the Director-General of the Geological Survey, and Prof. T. M*Kenny Hughes, M.A. Treasurer: F. W. Rudler. General Secretaries: J. W. Hulke, F.R.S., and W. Topley. Steps are being taken to enlist the cooperation of all persons interested in Geology and the allied branches of science. Particulars will be immediately announced by the Committee. Fellows of the Society are invited to join the Congress and tc assist in making the Meeting a success. The following communications were read :-— 1. “On the Correlation of some of the Eocene Strata in the Ter- tiary Basins of England, Belgium, and the North of France.” By Prof. Joseph Prestwich, M.A., F.R.S., F.G.S. 9. “On the Cambrian and Associated Rocks in North-west Caer- naryonshire.” By Prof. J. F. Blake, M.A., F.G.S. The following specimens were exhibited :— Rocks and Rock-sections, exhibited by Prof. J. F. Blake in illus- tration of his paper. January 11, 1888. Prof. J. W. Jupp, F.R.S., President, in the Chair. Percy John Ogle, Esq., 4 Bishopsgate Street Within, E.C., and Frederick Danvers Power, Esq., of the Geological Society of Austral- asia, 17 Queen Street, Melbourne, Victoria, were elected Fellows ; Baron F. von Richthofen of Berlin, and Prof. G. Vom Rath of Bonn, Foreign Members; and Prof. W. C. Brogger of Stockholm, and Dr. Anton Fritsch of Prague, Foreign Correspondents of the Society. The List of Donations to the Library was read. The following communications were read :— 1. “ On the Law that governs the Action of Flowing Streams.” By R. D. Oldham, Esq., F.G.S. 2. “Supplementary Notes on the Stratigraphy of the Bagshot Beds of the London Basin.” By the Rev. A. Irving, B.Sc., B.A., F.G.S. 3. “The Red-Rock Series of the Devon Coast Section.” By the Rey. A. Irving, B.Sc., B.A., F.G.S. 6 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. The following specimens were exhibited :— Casts of Shells from Bagshot Beds (? Upper) in Sandpit at West- street, near Highclere, Hants, exhibited by R. 8S. Herries, Esq., G9: Specimens from the Red-Rock Series, exhibited by the Rey. A. Irving, F.(.S., in illustration of his paper. January 25, 1888. Prof. J. W. Jupp, F.R.S., President, in the Chair. Thomas Adair Masey, Esq., Adelaide, Blinman, South Australia, was elected a Fellow of the Society. The List of Donations to the Library was read. The following communications were read :— 1. “On Atlurus anglicus, a new Carnivore from the Red Crag.” By Prof. W. Boyd Dawkins, M.A., F.R.S., F.G.8. 2. “A Contribution to the Geology and Physical Geography of the Cape Colony.” By Prof. A. H. Green, M.A., F.RS., F.G.S. 3. “On two new Lepidotoid Ganoids from the early Mesozoic Deposits of Orange Free State, South Africa.” By A. Smith Wood- ward, Esq., F.G.S. The following specimens were exhibited :— Specimen of Ailurus anglicus from the Red Crag, Felixstowe, Suffolk, exhibited by Prof. W. Boyd Dawkins, F.R.S., F.G.S., on behalf of the Yorkshire Philosophical Soeiety, in illustration of his paper. Specimen of the skull of Adlurus fulgens, Cuy., from Nipal, exhi- bited by R. Lydekker, Esq., F.G.S. Rock specimens and microscopic sections, exhibited by Prof. A. H. Green, F.R.S., F.G.S., in Ulustration of his paper. Specimens of Clithrolepis Extoni, sp. noy., from the Stormberg ~ beds, Orange Free State, exhibited by Dr. H. Woodward, F.R.S., F.G.8., on behalf of Dr. H. Exton, F.G.S., in illustration of the paper by A. Smith Woodward, Esq., F.G.S. Remains of Squatina Crane, sp. nov., and mandible of Belono- stomus cinctus, Agass., from the Chalk of Sussex, exhibited by Henry Willett, Esq., F.G.S. PROCEEDINGS OF THE GEOLOGICAL SOCIETY. — 7 February 8, 1888. Prof. J. W. Jupp, F.R.S., President, in the Chair. William Duncan, Esq., 25 Tavistock Road, London, W.; Alex- ander M‘Kay, Ksq., New Zealand Geological Survey, Wellington, New Zealand; James Park, Ksq., New Zealand Geological Survey, Wellington, New Zealand ; and Frederick Wilkinson, Esq., 2 Vernon Street, Bolton, Lancashire, were elected Fellows of the Society. The List of Donations to the Library was read. The following communications were read :— 1. “On some Remains of Squatina Cranei, sp. nov., and the Mandible of Belonostomus cinctus, from the Chalk of Sussex, pre- served in the Collection of Henry Willett, Esq., F.G.S., Brighton Museum.” By A. Smith Woodward, Esq., F.G.S. 2. “On the History and Characters of the Genus Septastrea, D’Orbigny (1849), and the Identity of its Type Species with that of Glyphastrea, Duncan (1887).” By George Jennings Hinde, Ph.D., 3. ** On the Examination of Insoluble Residues obtained from the Carboniferous Limestone at Clifton.” By E. Wethered, Esq., F.G.S, The following specimens were exhibited :— Remains of Squatina Cranei, sp. nov., and mandible of Belonosto- mus cinctus, Agass., from the Chalk of Sussex, exhibited by Henry Willett, Esq., F.G.S., in illustration of the paper by A. Smith Woodward, Esq., F.G.S. Specimens of Septastraa Forbesi, belonging to the Scarborough Museum, exhibited by C. Fox Strangways, Esq., F.G.S., in illus- tration of Dr. Hinde’s paper. Specimens of Septastrea Forbesi, E. & H., of Astrea? mary- landica, Conrad, and Astrea? bella, Conrad, from the Tertiaries of the United States, exhibited, by permission of Prof. Angelo Heil- prin, of Philadelphia, by Dr. G. J. Hinde, F.G.S., in illustration of his paper. Photographs and microscopic specimens, exhibited by E. Weth- ered, Esq., F.G.S., in illustration of his paper. Glassy Volcanic Bombs which float on water, picked up 15 miles from Mount Tarawera, New Zealand, after the outburst of June 1886, exhibited by H. B. Armstrong, Esq., B.A., F.G.S. 8 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. ANNUAL GENERAL MEETING, February 17, 1888. Prof. J. W. Jupp, F.R.S., President, in the Chair. Report. oF THE Councit FoR 1887. In presenting their Report for the year 1887, the Council of the Geological Society have much pleasure in being again able to con- gratulate the Fellows upon the continued prosperity of the Society. The Income of the Society has been considerably larger than in 1886, so that notwithstanding the Investment of a sum of £250, and the extraordinary expenditure incurred in connexion with the Redecoration, Repairs, and Alterations made in the Society’s House, the Accounts still show a balance in favour of the Society. The number of Fellows elected during the year is 46, of whom 43 paid their fees before the end of the year, making with 10 previously elected Fellows, who paid their fees in 1887, a total accession during the year of 53 Fellows. During the same period, however, there was a loss by death of 39 Fellows, and by resignation of 15 Fellows, while 6 Fellows were removed from the List for non-pay- ment of their annual contributions, making a total loss of 60 Fellows. There is thus an actual decrease of 7 in the number of Fellows of the Society. Of the 39 Fellows deceased, 10 were Compounders, and 12 non-contributing Fellows; the number of contributing — Fellows is increased by 7, being now 840. The total number of Fellows, Foreign Members and Foreign Correspondents was 1423 at the end of the year 1886, and 1413 at the close of 1887. At the end of 1886 there was one vacancy in the List of Foreign Members, and this was filled up in the course of 1887. During that year, intelligence was received of the decease of 4 Foreign Members. In the List of Foreign Correspondents there was also one vacancy at the end of 1886, and intelligence was received during 1887 of the decease of 2 Foreign Correspondents. This loss, with the filling up of 2 vacancies among the Foreign Members, caused in all 5 vacancies in the List of Foreign Correspondents, 3 of which were filled up during the year. Thus, at the close of the year 1887, there were 3 vacancies in the List of Foreign Members, and 2 in that of the Foreign Correspondents of the Society. ANNUAL REPORT. g The total Receipts on account of Income for the year 1887 were £2760 15s. 9d., being £263 15s, 9d. more than the estimated Income for the year. The ordinary current Expenditure of the year, leaving out of account the sum of £254 7s. 6d. expended in the purchase of £250 Reduced 3 per cent. Stock, was £2453 8s. 2d., or £3 12s. 2d. in excess of the Estimate. Actually, however, the Expenditure of the year was £2961 15s. 8d., or £511 19s. 8d. in excess of the printed Estimate. This is due to the fact that the cleaning, repairs, redecoration, and ventilation of the Society’s rooms have been carried out in the course of the past year, and the Council consider it desirable that the Fellows of the Society should be fully informed of the reasons for undertaking the work, and the circum- stances under which it was carried out. When the Society, in 1874, accepted from H.M. Government the apartments now occupied in Burlington House, free of rent, it was with the condition that the cost of all necessary internal repairs,. painting, and redecoration should be borne by the Society. In 1887 upwards of thirteen years had elapsed without any internal painting or repairs, and for some years past it had been evident that a considerable expenditure would be needed for these purposes. Had the necessary Funds been in hand the work would have been undertaken three or four years ago. For the last two years, by reducing expenditure, the Council have succeeded in accumulating a considerable sum, and £500 has been invested in two instalments. to meet the contemplated expenses. In February last the Council announced in their Report, which was accepted by the Fellows, that it might be advisable in the course of the coming summer to make use of a part of the balance then available for the execution of the necessary repairs, painting, &c., of the interior of the Society’s House. It would have been exceedingly difficult, at the time, to give an estimate of the cost, for until the work was actually in hand no one could tell what the expenditure might be. In the course of the summer, as had been hoped, it was found that the state of the Society’s finances justified the expenditure now considered essential. By the time that the necessary inquiries had been made, and estimates of the cost obtained, the Ordinary General Meetings of the Society had come to an end for the Session; and ‘ had the procedure laid down in the Bye-Laws been followed, all action must have been delayed for a year, a course which might have involved the Society in greatly increased expense, besides post- poning the cleaning of the building, which had become necessary. Under these circumstances the Council determined, on their own responsibility, to order the necessary work to be carried out, and subsequently asked the Fellows of the Society to sanction the expen- diture. This was done at a special General Meeting held for the purpose on the 23rd of November, 1887. Some doubt, however, has been expressed whether the course adopted by the Council was strictly in accordance with the Bye- Laws. Under these circumstances the Council trust that the pre- Io PROCEEDINGS OF THE GEOLOGICAL SOCIETY. sent Meeting, by adopting this Report, will express its approval of the course followed. The Council are of opinion that the time has arrived when the Bye-Laws might be reconsidered, in order to ascertain whether the introduction of any modifications would be to the advantage of the Society. Tt will be remembered that the Special General Meeting of November 23rd authorized the sale of such an amount of Stock as might be necessary for the purpose of defraying the cost of painting, repairs, &c. It is with much pleasure that the Council are able to announce that no sale of Stock has been found requisite, but that the whole cost of cleaning, painting, repairs, and ventila- tion has been paid out of Income and the balance remaining at the Society’s credit after the Investments already mentioned had been made. ‘Thus an addition of £500 has been secured to the Society’s permanent Investments, besides defraying all expenses, ordinary and extraordinary. The Council have no doubt that the very material improvement thus manifested in the financial position of _ the Society, as compared with that at the close of 1885, will be considered very satisfactory. At the desire of many of the Fellows, a Conversazione, which was well attended and gave general satisfaction, was held in the rooms of the Society on the evening of the 2nd November last. The Council have to announce the completion of Vol. XLUL, and the commencement of Vol. XLIV. of the Society’s Quarterly Journal. The Council have awarded the Wollaston Medal to H. B. Medlicott, Hsq., F.R.S., F.G.8., in recognition of the additions made by him to our knowledge of the Geology of India. The Murchison Medai, with the sum of Ten Guineas from the proceeds of the Fund, has been awarded to Prof. J. 8. Newberry, M.D., F.M.G.S., of New York, as a mark of appreciation of the long series of researches made by him into the Geology and Paleon- tology of Ohio and of other parts of the United States. The Lyell Medal, with a sum of Twenty-five Pounds from the roceeds of the Fund, has been awarded to Prof. Henry Alleyne Nicholson, M.D., D.Sc., F.G.S., in testimony of the value of his Geological investigations in the Lake District and in Canada, and of his studies of many obscure forms of Ancient Life. The balance of the proceeds of the Wollaston Donation Fund has been awarded to John Horne, Esq., F.R.S.E., F.G.S., in token of appreciation of his contributions to the Geology of the Voleanie and Glacial Rocks of Scotland, and to assist him in the further prosecu- tion of his researches. The balance of the proceeds of the Murchison Geological Fund has been awarded to EK. Wilson, Esq., F.G.S., in recognition of the alue of his researches into the Geology of the Midland and South- western counties of England, and to aid him in further investiga- tions. . One moiety of the Balance of the proceeds of the Lyell Geolo- ANNUAL REPORT. II gical Fund has been awarded to Arthur Humphreys Foord, Ksq., F.G.S., as a testimony to the importance of the additions made by him to our knowledge of the Monticuliporide and other fossil organisms in Canada and this country, and to assist him in con- tinuing his studies. The remainder of the balance of the Lyell Geological Fund has been awarded to Thomas Roberts, Esq., B.A., F.G.S., in token of appreciation of his investigations into the correlation of the Jurassic rocks, and to aid him in the prosecution of similar inquiries. The Council have decided to apply the sum of Thirty Pounds from the proceeds of the Barlow-Jameson Fund to the improvement and re-arrangement of the contents of the Society’s Museum. I2 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. Report oF THE LIBRARY AND Museum CoMMITTEER. Labrary. Since the last Anniversary Meeting a great number of valuable additions have been made to the Library, both by donation and by purchase. As Donations the Library has received about 128 volumes of separately published works and Survey Reports, and 234 pamphlets and separate impressions of Memoirs, besides about 159 volumes and 97 detached parts of the publications of various Societies. Further, 9 volumes of independent Periodicals, presented chiefly by their respective Editors, and 15 volumes of Newspapers have been received. This constitutes a total addition to the Society’s Library, by donation, of about 830 volumes and 234 pamphlets. A considerable number of Maps, Plans, and Charts have been added to the Society’s Collection by presentation, chiefly from the Ordnance Survey of Great Britain, whose donations amount to 899 Sheets, large and small. From the French Dépét de la Marine © 4 sheets of charts and coast-plans have been received. Of Geological-Survey publications the Society has received 34 sheets of Maps and Sections from the Geological Survey of Italy, 9 sheets from the Swedish Geological Survey, 4 sheets from the Roumanian Geological Bureau, and 1 sheet from the Imperial Geo- logical Survey of Japan. Of the Geological Map of Queensland 2 copies have been received, one from the Queensland Department of Public Works, the other from the author, Mr. R. L. Jack; and a copy of a revised edition of the Geological Map of South Australia has been presented by the Colonial Geologist, Mr. H. Y. L. Brown. Seven sheets of the Atlas of New Jersey were presented by the State Geologist. Other additions are Mr. E. Best’s new small Geological Map of the British Isles ; anda Map of the English Lakes and adja- cent country, geologically coloured by Mr. J. Ruthven (in 1855), the latter presented by Mr. W. Whitaker. The total number of Maps, Charts, and Plans presented during the year was 967. Several photographs of interest were also presented to the Society in 1837. The Books, Maps, &c. above referred to have been received from 156 personal Donors, the Editors or Publishers of 15 Periodicals, and 189 Societies, Surveys, and other Public Bodies, making, in all, 360 Donors. By purchase, on the recommendation of the Standing Library Committee, the Library has received the addition of 57 volumes of books, and of 12 volumes and 60 parts (making about 20 volumes) of various Periodicals, besides 32 parts of certain works in course of publication serially. Of the Geological-Survey Map of France 6 sheets have been obtained by purchase, as also 8 sheets of the smaller Geological fa of France and the neighbouring districts, by MM. Vasseur and arez, ANNUAL REPORT. 13 The cost of Books, Periodicals, and Maps purchased during the year 1887 was £50 9s. 6d., and that of Binding £120 11s. 11d., making a total of £171 1s. 5d. Museum. No additions have been made to the collections in the Museum during the past year. The Committee having taken into consideration the fact that no general cleaning of the specimens in the Society’s Museum has taken place since the Collections were placed in their present cabinets, and also that a partial rearrangement of some of the series ‘was desirable, recommended to the Council that the necessary work should be undertaken in the course of the coming spring and summer. The Council have adopted this recommendation, and the work will be carried out accordingly. I4 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. CoMPARATIVE STATEMENT OF THE NUMBER OF THE SOCIETY AT THE CLOSE OF THE YEARS 1886 ann 1887. Dec. 31, 1886. Dee. 31, 1887. Compounders......... Ee O14 eee 312 Contributing Fellows...... Soon of ane 840 Non-contributing Fellows .. 198. ae 186 1345 1338 Foreign Members ........ es ew ese 37 Foreign Correspondents... .. ee 38 1423 1413 Comparative Statement explanatory of the Alterations in the Number of Fellows, Foreign Members, and Foreign Correspondents at a close of the years 1886 and 1887. Number of Compounders, Contributing and Non- 1345 contributing Fellows, December 31, 1886.... Add Fellows elected during former year and paid 10 in US67"- oe eR ai eee Add Fellows elected and paid in 1887 ........ 43 1398 Deduct Compounders deceased .............. 10 Contributing Fellows deceased ........ 17 Non-contributing Fellows deceased.... 12 Contributing Fellows resigned ........ 15 Contributing Fellows removed ........ 6 — 60 1338 Number of Foreign Members, and aes 78 Correspondents, December 31, 1886 .... Deduct Foreign Members deceased... ..... + Foreign Correspondents deceased 2 Foreign Correspondents ie 9 Foreign Members .......... — 8 70 Add Foreign Members elected ........ 2 wee Foreign Correspondents elected ........ 3 ANNUAL REPORT. DercrAseD FELLOWS. Baber, J., Esq. Callard, T. K., Esq. Coxon, 8. B., Esq. Eyre, G. E., Esq. Fraser, Rev. C. Compounders (10). Jenkins, H. M., Esq. King, W. P., Esq. Richards, W. P., Esq. Thomas, C., Esq. Witchell, E., Esq. Resident and other Contributing Fellows (17). Brickenden, J. G., Esq. Bright, H. E. R., Esq. Brook, T., Esq. Carrick, Rev. J. L. Champernowne, A., Esq. Cooke, J. 8., Esq. Haast, Sir J. von. Heckels, M., Esq. Morris, A., Esq. Bastérot, Comte de. Breton, Capt. W. H. Evans, T., Esq. Guise, Sir W. VY. Hervey, Rev. Lord C. A. Hymers, Rev. J. Newman, F., Esq. Phillips, J. A., Esq. Price, Major W. E. Routledge, T. Stevenson, T. Twamley, C. White, Rev. F. le Grix. Wilson, C. H., Esq. Non-contributing Fellows (12). Ingram, Rey. Canon. Lee, J. E., Esq. Lees, E., Esq. Sharp, J., Esq. Symonds, Rev. W. S. Thornton, Rev. J. Foreign Members (4). Desnoyers, M. Jules. Hayden, Dr. F. V. Koninck, Prof. L. G. de. Studer, Prof. B. Foreign Correspondents (2). Cornet, M. F. L. | Marschall, Count A. F. 16 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. Fellows Resigned (15). Galton, C. E., Esq. | Lucas, A. H.8., Esq. Harris, E., Esq. | Pankhurst, E. A., Esq. Heighton, H. J., Esq. | Ridgway, J., Esq. Hunt, Rev. H. G. B. Roberts, Rev. W. W. TVAnson, J., Esq. Shelford, W., Esq. Kernahan, Rev. J. | Wood, C. J., Esq. Anson, J. C., Esq. | Stainton, H. T., Esq. Lester, W., Esq. Fellows Removed (6). Luke, G. B., Esq. Read, N. W. R., Esq. ° M°Cann, Rev. J. | Thomas, D., Esq. Nevill, W. J., Esq. | Warwick, F., Esq. The following Personages were elected from the List of Foreign Cor- respondents to fill the vacancies in the List of Foreign Members during the year 1887. Professor J. P. Lesley, of Philadelphia. Professor J. D. Whitney, of Cambridge, U.S. The following Personages were elected Foreign Correspondents during the year 1887. Senhor J. F. N. Delgado, of Lisbon. Professor A. Heim, of Zurich. Professor A. de Lapparent, of Paris. ANNUAL REPORT. 17 After the Reports had been read, it was resolved :— That they be received and entered on the Minutes of the Meeting, and that such parts of them as the Council shall think fit be printed and distributed among the Fellows. It was afterwards resolved :— That the thanks of the Society be given to Professor J. W. Judd, retiring from the office of President. That the thanks of the Society be given to H. Bauerman, Ksq., Professor T. G. Bonney, and Dr. A. Geikie, retiring from the office of Vice-President. That the thanks of the Society be given to Dr. W. T. Blanford, . retiring from the office of Secretary. That the thanks of the Society be given to H. Bauerman, Esq., Professor T. G. Bonney, T’. Davies, Esq., Prof. “P. M. Duncan, and J.J. H. Teall, Esq., retiring from the Council. After the Balloting-glasses had been duly closed, and the Lists examined by the Scrutineers, the following gentlemen were declared to have been duly elected as the Officers and Council for the ensuing year :— VOL. XLIV. b 18 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. OFFICERS. PRESIDENT. W. T. Blanford, LL.D., F.R.8. VICE-PRESIDENTS. John Evans, D.C.L., LL.D., F.R.S. Prof, T. M*Kenny Hughes, M.A. Prof. J. Prestwich, M.A., F.R.S. Henry Woodward, LL.D., F.R.S. SECRETARIES. W. H. Hudleston, Esq., M.A., F.R.S. J. HK. Marr, Esq., M.A. FOREIGN SECRETARY. Sir Warington W. Smyth, M.A., F.R.S. TREASURER. Prof. T. Wiltshire, M.A., F.LS. COUNCIL. W. T. Blantord, LD; EARS: Col. C. A. M®Mahon. John Evans, D.C.L., LL.D., F.R.S. | J. HE. Marr, Esg., M.A. L. Fletcher, Esq., M.A. EK. Tulley Newton, Esq. A. Geikie, LL.D., F.R.S. Prof. J. Prestwich, M.A., F.R.S. Henry Hicks, M.D., F.R.S. Prof. H. G. Seeley, F.R.S. Rev. Edwin Hill, M.A. Sir Warington W. Smyth, M.A., W.H. Hudleston, Esq., M.A., F.R.S.| F.R.S. Prof. T. M*Kenny Hughes. W. Topley, Esq. J. W. Hulke, Esq., F.R.S. Rev. G. F. Whidborne, M.A. Prof. T. Rupert Jones, F.R.S. Prof. T. Wiltshire, M.A., F.L.S. Prof. W. Judd; hans: Rev. H. H. Winwood, M.A. R. Lydekker, Esq., B.A. Henry Woodward, LL.D., F.R.S. ANNUAL REPORT. LIST OF THE FOREIGN MEMBERS OF THE GEOLOGICAL SOCIETY OF LONDON, 1n 1887. Date of Election. 1827. Dr. H. von Dechen, Bonn. 1848. James Hall, Esq., Albany, State of New York. 1851. Professor James D. Dana, New Haven, Connecticut. 1853. Count Alexander von Keyserling, Raykiill, Russva. 1856. Professor Robert Bunsen, For. Mem. R.S., Hezdelberg. 1857. Professor H. B. Geinitz, Dresden. 1859. Dr. Ferdinand Romer, Breslau. 1866. Dr. Joseph Leidy, Philadelphia. 1867. Professor A. Daubrée, For. Mem. R.S., Paris. 1871. Dr. Franz Ritter von Hauer, Vienna. 1874. Professor Alphonse Favre, Geneva. 1874. Professor E. Hébert, Paris. 1874. Professor Albert Gaudry, Paris. 1875. Professor Fridolin Sandberger, Wiirzburg. 1875. Professor Theodor Kjerulf, Christiania. 1875. Professor F. August Quenstedt, Tiibingen. 1876. Professor EK. Beyrich, Berlin. 1877. Dr. Carl Wilhelm Gtimbel, Maumnich. 1877. Dr. Eduard Suess, Vienna. 1879. Major-General N. von Kokscharow, S¢. Petersburg. 1879. M. Jules Marcou, Cambridge, U. 8. 1879. Dr. J. J.S. Sieenstrup, For. Mem. R.8., Copenhagen. 1880. Professor Gustave Dewalque, Lrége. 1880. Baron Adolf Erik Nordenskidld, Stockholm. 1880. Professor Ferdinand Zirkel, Lezpzig. 1882. Professor Sven Lovén, Stockholm. 1882. Professor Ludwig Ritimeyer, Basle. 1883. Professor J. 8. Newberry, New York. 1883. Professor Otto Martin Torell, Stockholm. 1884. Professor G. Capellini, Bologna. 1884, Professor A. L. O. Des Cloizeaux, For. Mem. R.S., Paris. 1884, Professor G. Meneghini, Pisa. 1884. Professor J. Szabo, Pesth. 1885. Professor Jules Gosselet, Lille. 1886. Professor Gustav Tschermak, Vienna. 1887. Professor J. P. Lesley, Philadelphia. 1887. Professor J. D. Whitney, Cambridge, U.S. 20 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. LIST OF THE FOREIGN CORRESPONDENTS OF THE GEOLOGICAL SOCIETY OF LONDON, 1n 1887. Date of Election. 1863. Dr. F. Senft, Evsenach. 1864. Dr. Charles Martins, Montpellier. 1866. Professor Victor Raulin, Bordeauz. 1866. Baron Achille de Zigno, Padua. 1872. Herr Dionys Stur, Vienna. 1874. Professor Igino Cocchi, Florence. 1874. M. Gustave H. Cotteau, Auzrerre. 1874. Professor G. Seguenza, Messina. 1874. Dr. T. C. Winkler, Haarlem. 1877. Professor George J. Brush, New Haven. 1877. Professor E. Renevier, Lausanne. 1877. Count Gaston de Saporta, Azx-en- Provence. 1879. Professor Pierre J. van Beneden, For.Mem.R.S., Louvain. 1879. M. Edouard Dupont, Brussels. 1879. Professor Gerhard Vom Rath, Bonn. 1879. Dr. Emile Sauvage, Paris. 1880. Professor Luigi Bellardi, Turin. 1880. Professor Leo Lesquereux, Columbus. 1880. Dr. Melchior Neumayr, Vienna. 1880. M. Alphonse Renard, Brussels. 1881. Professor E. D. Cope, Philadelphia. 1882. Professor Louis Lartet, Toulouse. 1882. Professor Alphonse Milne-Edwards, Paris. 1883. Baron Ferdinand von Richthofen, Leipzig. 1883. Professor Karl Alfred Zittel, Munich. 1884. Dr. Charles Barrois, Zvile. 1884, M. Alphonse Briart, Morlanwelz. 1884. Professor Hermann Creduer, Letpzig. 1884, Baron C. von Ettingshausen, Gratz. 1884. Dr. E. Mojsisovics von Mojsvar, Vienna 1885. M. F. Fouqué, Paris. 1885. Professor G. Lindstrém, Stockholm. 1885, Dr. A. G. Nathorst, Stockholm. 1886. Professor BD. Rosenbusch, Heidelberg. 1886. Professor J. Vilanova y Piera, Madrid. 1887. Senhor J. F. N. Delgado, Lisbon. 1887. Professor A. Heim, Zurich. 1887. Professor A. de Lapparent, Paris, ANNUAL REPORT. 21 AWARDS OF THE WOLLASTON MEDAL ESTABLISHED BY UNDER THE CONDITIONS OF THE ‘‘ DONATION FUND” WILLIAM HYDE WOLLASTON, M_D., F.R.S., F.G.S., &e. To promote researches concerning the mineral structure of the earth, and to enable the Council of the Geological Society to reward those individuals of any country by whom such researches may hereafter be made,”—“ such individual not being a Member of the Council.”’ 1831. 1835. 1836, 1837. 1838. 1839. 1840. 1841. 1842. 1845. 1844. 1845. 1846. 1847, 1848. 1849. 1850. 1851. 1852. 1853. 1854. 1855. 1856. 1857. 1858. 1859, Mr. William Smith. Dr. G. A. Mantell. M. Louis Agassiz. Capt. T. P. Cautley. Dr. H. Falconer. Sir Richard Owen. Professor C. G. Ehrenberg. Professor A. H. Dumont. M. Adolphe T. Brongniart. Baron L. von Buch. M. Elie de Beaumont. M. P. A. Dufrénoy. Rey. W. D. Conybeare. Professor John Phillips. Mr. William Lonsdale. Dr. Ami Boué. Rev. Dr. W. Buckland. Professor Joseph Prestwich. Mr. William Hopkins. Rev. Prof. A. Sedgwick. Dr. W. H. Fitton. M. le Vicomte A. d’Archiac. M. E. de Verneuil. Sir Richard Griffith. Sir H. T. De la Beche. Sir W. E. Logan. M. Joachim Barrande. ae Hermann von Meyer. Mr. James Hall. Mr. Charles Darwin. 1860. 1861. 1862. 1863, 1864. 1865, 1866. 1867. 1868. 1869. 1870. 1871. 1872. 1873. 1874. 1875. 1876. 1877. 1878. 1879. 1880. 1881. 1882. 1885. 1884. 1885. 1886. 1887, 1888. Mr. Searles V. Wood. Professor Dr. H. G. Bronn. Mr. R. A. C. Godwin-Austen. Professor Gustav Bischof. Sir R. I. Murchison. Dr. Thomas Davidson. Sir Charles Lyell. Mr. G. Poulett Scrope. Professor Carl F. Naumann. Dr. H. C. Sorby. Professor G. P. Deshayes. Sir A. C. Ramsay. Professor J. D. Dana. Sir P. de M. Grey-Egerton. Professor Oswald Heer. Professor L. G. de Koninck. Professor T. H. Huxley. Mr. Robert Mallet. Dr. Thomas Wright. Professor Bernhard Studer. Professor Auguste Daubrée. Professor P. Martin Duncan. Dr. Franz Ritter von Hauer. Dr. W. T. Blanford. Professor Albert Gaudry. Mr. George Busk. Professor A. L. O. Des Cloizeaux. Mr. J. Whitaker Hulke. Mr. H. B. Medlicott. 22 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. AWARDS OF THE BALANCE OF THE PROCEEDS OF THE WOLLASTON “ DONATION-FUND.” 1831. 1833. 1854. 1835. 1836. 1838. 1839. 1840. 1841. 1842. 1845. 1844. 1845. 1846. 1847. 1848. 1849. 1850. 1851. 1852. 1855. 1854. 1855. 1856. 1857. 1858. 1859. 1860. Mr. William Smith. Mr. William Lonsdale. M. Louis Agassiz. Dr. G. A. Mantell. Professor G. P. Deshayes. Sir Richard Owen. Professor C. G. Ehrenberg. Mr. J. De Carle Sowerby. Professor Edward Forbes. Professor John Morris. Professor John Morris. Mr. William Lonsdale. Mr. Geddes Bain. Mr. William Lonsdale. M. Alcide d’Orbigny. Cape-of-Good-Hope Fossils. M. Alcide d’Orbigny. Mr. William Lonsdale. Professor John Morris. M. Joachim Barrande. Professor John Morris. Professor L. G. de Koninck. Dr. 8. P. Woodward. Drs. G. and FI’. Sandberger. Professor G. P. Deshayes. Dr. 8. P. Woodward. Mr. James Hall. Mr. Charles Peach. Professor T. Rupert Jones. ie W. K. Parker. 1861. 1862. 1863. 1864, 1865. 1866. 1867. 1868, 1869. 1870. sve 1872. 1873. 1874. 1875. 1876. 1877. 1878. 1879. 1880. 1881. 1882. 1883. 1884. 1885. 1886. 1887. 1888, Professor A. Daubrée. Professor Oswald Heer. Professor Ferdinand Senft. Professor G. P. Deshayes. Mr. J. W. Salter. Dr. Henry Woodward. Mr. W. H. Baily. M. J. Bosquet. Mr. W. Carruthers. M. Marie Rouault. Mr. R. Etheridge. Dr. James Croll. Professor J. W. Judd. Dr. Henri Nyst. Mr. L. C. Miall. Professor Giuseppe Seguenza. Mr. R. Etheridge, Jun. Professor W. J. Sollas. Mr. 8. Allport. Mr. Thomas Davies. Dr. R. H. Traquair. Dr, G..J. Hinde: Mr. John Milne. Mr. E. Tulley Newton. Dr. Charles Callaway. Mr. J. S. Gardner. Mr. B. N. Peach. Mr. John Horne. ANNUAL REPORT. 23 AWARDS OF THE MURCHISON MEDAL AND OF THE PROCEEDS OF “THE MURCHISON GEOLOGICAL FUND,” ESTABLISHED UNDER THE WILL OF THE LATE SIR RODERICK IMPEY MURCHISON, Banrt., F.R.S., F.G.S. “To be applied in every consecutive year in such manner as the Council of the Society may deem most useful in advancing gevlogical science, whether by granting sums of money to travellers in pursuit of know- ledge, to authors of memoirs, or to persons actually employed in any inquiries bearing upon the science of geology, or in rewarding any such travellers, authors, or other persons, and the Medal to be given to some person to whom such Council shall grant any sum of money or recompense in respect of geological science.” 1873. 1873. 1874. 1874. 1874. 1875. 1875. 1876. 1876. 1877. hic/We 1878. 1878. 1879. 1879. 1880. 1881. 1881. Mr. William Davies. Medal. Professor Oswald Heer. Dr. J. J. Bigsby. Medal. My. Alfred Bell. Professor Ralph Tate. Mr. W. J. Henwood. Medal. Professor H. G. Seeley. Mr. A.R.C.Selwyn. Medal. Dr. James Croll. Rev. W. B. Clarke. Professor J. F. Blake. Dr. H. B. Geinitz. Medal. Professor C. Lapworth. Medal. Professor I’. M‘Coy. Medal. Mr. J. W. Kirkby. Mr. R. Etheridge. Medal. Professor A.Geikie. Medal. Mr. F. Rutley. 1882. 1882. 1883. 1883. 1884, 1884. 1885. 1885. 1886. 1886, 1887. 1887. 1888. 1888. Professor J.Gosselet. Medal. Professor T. Rupert Jones. Professor H. R. Goppert. Medal, Mr. John Young. Dr. H. Woodward. Medal. Mr. Martin Simpson. Dr. Ferdinand Romer. Medal. Mr. Horace B. Woodward. Mr. W. Whitaker. Medal. Mr. Clement Reid. Rev. P. B. Brodie. Medal. Mr. Robert Kidston. Professor J. 8. Newberry. Medal. Mr. E. Wilson. 24 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. AWARDS OF THE LYELL MEDAL AND OF THE PROCEEDS OF THE “LYELL GEOLOGICAL FUND, ESTABLISHED UNDER THE WILL AND CODICIL OF THE LATE SIR CHARLES LYELL, Barr., F.R.S., F.G.S. The Medal “to be given annually” (or from time to time) “as a mark of honorary distinction as an expression on the part of the governing body of the Society that the Medallist has deserved well of the Science,”—‘ not less than one third of the annual interest [of the fund] to accompany the Medal, the remaining interest to be given in - one or more portions at the discretion of the Council for the encou- ragement of Geology or of any of the allied sciences by which they shall consider Geology to have been most materially advanced.” 1876. 1877. 1877. 1878. 1878. 1879. 1879. 1879. 1880. 1880. 1881. 1881. 1881. 1882. 882. Professor John Morris. Medal. Dr. James Hector. Medal. Mr. W. Pengelly. Mr. G. Busk. Medal. Dr. W. Waagen. Professor Edmond Hébert. Medal. Professor H. A. Nicholson. Dr. Henry Woodward. Mr. John Evans. Medal. Professor F. Quenstedt. Sir J. W. Dawson. Medal. Dr. Anton Fritsch. Mr. G. R. Vine. Dr. J. Lycett. Medal. Rey. Norman Glass. 1882. 1883. 1883. 1883. 1884. 1884. 1885. 1885. 1886. 1886. 1887. 1887. 1888. Professor C. Lapworth. Dr. W. B. Carpenter. Medal. Mr. P. H. Carpenter. M. E. Rigaux. Dr. Joseph Leidy. Medal. Professor Charles Lapworth. Professor H. G. Seeley. Medal. Mr. A. J. Jukes-Browne. Mr. W. Pengelly. Medal. Mr. D. Mackintosh. Mr. Samuel Allport. Medai. Rey. Osmond Fisher. Professor H. A. Nicholson. Medai. 888. Mr. A. H. Foord. OO (os) (o6) . Mr. T. Roberts. ty ul ANNUAL REPORT, AWARDS OF THE BIGSBY MEDAL, FOUNDED BY Das ds)S. BIGSBY, FES. Ga To be awarded biennially “as an acknowledgment of eminent services in any department of Geology, irrespective of the receiver’s country ; but he must not be older than 45 years at his last birthday, thus probably not too old for further work, and not too young to have done much.” 1877. Professor O. C. Marsh. 1883. Dr. Henry Hicks. 1879. Professor E. D. Cope. 1885. Professor Alphonse Renard. 1881. Dr. C. Barrois. ; 1887, Professor Charles Lapworth. AWARDS OF THE PROCEEDS OF THE BARLOW- JAMESON FUND, ESTABLISHED UNDER THE WILL OF THE LATE Dr. H. C. BARLOW, F.G:S. “The perpetual interest to be applied every two or three years, as may be approved by the Council, to or for the advancement of Geological Science.” 1880. Purchase of microscope. 1884, Professor Leo Lesquereux. 1881. Purchase of microscope lamps. | 1886. Dr. H. J. Johuston-Lavis. 1882. Baron C. von Ettingshausen. {| 1888. Museum. 1884, Dr. James Croll. VOL. XLIV. C 26 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. Estimates for INCOME EXPECTED. Due for Arrears of Annual Contributions ...... 130 0 0 Due for Arrears of Admission-fees ............ 20 0 0 150 0 O Estimated Ordinary Income for 1888 :— Annual Contributions from Resident Fellows, and Non- residents, 1859 to 18Gb 2,2 .4>.c580.eniike Meee 1500 0 O Adangsion=ees "+... taescs tes san sae ee eee 208 0 0 Compositions <2. Ate). Shae 68. eee eee 199 0 O Annual Contributions in advance ............2+006- 42 0 0 Dividends on Consols and Reduced 3 per Cents. .......... 248 1 4 Sale of Transactions, Library-catalogue, Orme- rod’s Index, Hochstetter’s New Zealand, and Last of Mellowe orcs tess Acad kace ste 3: 02 Sale of Quarterly Journal, including Longman’s ACCOMEL Creek Oc > eee eas ee ee ear eres 170 ‘OF® Sale of Geological Map, including Stanford’s account) .4.6. 55 HE Ae es eet eee ee es 7 Qi58 —— 180 0 0 £2527 1 4 THOMAS WILTSHIRE, Treas. 2 Feb, 1888. FINANCIAL REPORT. the Year 1888. 27 EXPENDITURE ESTIMATED. House Expenditure: a a, 2 £8: 4d. PEGS HSI POSUPANOO sas encsoannicevavdcaaseanuiten 43 10 0 ase e Oi ota ac Uc sinsici csascas'sasdneenen Li, OO House-repairs and Maintenance................06 ib: O00 ET SORTING os cain aisuinn din annivenavenedemedcewian 20, 08-6 Satie atid SUMGII ES, «aces sscdanscvcsccesnonanens 33 0 9 Pelt WNGEUIMES, 2.1. saietciveaceecteswscavatscaseaiess ie 204 10 0 Salaries and Wages: PRGA Seti SOCKORALY. ssa. vineneinsscensadeestccvaccssenes 350 0 0 Assistants in Library, Office, and Museum ... 225 0 O EPHRO LO WAEG ites sicineide daldleselae ea vieadbeleioae sade domed 105. 0). 0 MS PMIS OOM cathecte tae sae i WF dba ; ee St — - » Ses 4 — TU 3 9088 01350 1887