EXCUR SION TO TilE ISL E OF WIGHT.

EXCURSION TO THE ISLE OF WIGHT.

TH URSDAY, MARCH 26TH, TO T UESDAY, MARCH 31ST, r891.

Directors: The PRESIDENT and THO~IAS LEIGHTO:-l, F.G.S.

(Report hy T HE DIRECTORS, deferred from page 91.) This excursion was arranged to examine the west end and the south and south-east coasts of the Isle of Wight, tho se portions of the Island not havin g been visited by the Association since 1864. Additional interest was given to this excursion by the recent publication of the new Survey Map, and of the new edition of Bristow's Memo ir on the island by Messrs. Reid and Strahan. A large party therefore assembled, in spite of the cold, inclement weather. The President, Prof. J. F. Blake, acted as director for the Secondary, and Mr. Thomas Leighton (or the Tertiary rocks.

Thursday, March 26.-The party arrived by steamer in the afternoon, and settled into quarters at the Totland Bay Hotel. Before dinner, a small but important section in the Middle Headons was visited. This section is in a gully leading to the marsh from Freshwater Church-yard, and was only recently discovered by Mr. C. Re id (Memoir, p. 139). A glance at the map will show that it is an additional link in the evidence as to the continuity of the Middle H ead ons through Totl and Bay. From the hotel the party proceeded to that part of old Fresh­ water known as School Green , and thence followed the church path across the fields. Although the gully was partiall y blocked with snow, the Director soon produced a handful of fossils, sufficient evidence of the presence of the beds described. Fading light, and the state of the gully did not allow of any considerable collec­ tions being made ; it should, however, be not ed that Mr. Reid places this horizon, as the Nen'tina bed, at the bottom of the Middle Headons. After dinner the President briefly described the general geological features of the Island. Mr. Leighton then reminded members of the similarity of the general folding of the rocks to that obtaining in the south-east of England, a difference, however, being that the anticlinal and synclinal curves were less in the more northern area; he also remarked that there could be little doubt that all these folds had been formed at one and the same time. 10 EXCURSION TO THE ISLE OF WIGHT.

Friday, March 29th.-The party went by the main road to Yarmouth, passing on the way the patch of Plateau Gravel west of North Green; and there flints lying on Bembridge Limestone were observed Yarmouth passed, the first halt was made at the section on Harnstead Cliffs, figured by Forbes (Memoir, page 40)' The following table shows the divisions now usually adopted for the Tertiary beds of the Isle of Wight, the approximate thickness of each division at the place named, and the points where sections were visited on this occasion, which are at the same time all those of any moment at the west end of the Island. The thicknesses often vary very much within short distances.

rHempstead Beds 256 feet. Hamstead Cliffs. IBembridge Marls 70 " Along the shore under Hamstead Cliffs (not seen because of the tide). A capping under the gravels ~ of Headon Hill, jBembridge Limestone. 16 " Headon HilL g Osborne Beds . go Jl Cliff End (Colwell Bay). e ~ 74 " Headon HilL IUpper Headon Beds . 47 " Colwell Bay and Headon Hill. I Middle. 33 " Colwell Bay to Headon Hill; and at Freshwater I Church. lLower . 183 " Warden Cliff, &c. '/62 Headon Hill, {~~~ Alum Bay. >G t>i lHeadon Hill Sands f " ~ ~ Barton Clay .. 255 " og Bracklesham Beds , 155 " ~ \ Lower Bagshot Beds 652 " .," ~ t>i \'London Clay 230 " "'z " ~ ij '/ Woolwich and Reading ....l&l , Beds . . , 84 CHALK,

The Director said it would be noticed that Mr. Reid (Memoir, p. 127), had altered the name of the first division from Hemp­ stead Beds to Hamstead Beds. The Director did not agree with this alteration, because he felt sure, that sooner or later, some rule would have to be adopted for the unification of stratigraphical nomenclature; further, 'he was convinced that the proposal before the Geological Congress to " repousser de la nomenclature" all such names as Chalk, Oolite, Gault, and Coal Measures, and to substitute geographical names only would never be accepted by English geologists. * He thought that the way in which this question would eventually be settled

• Compte Rendu, Congo Geol. Internar., arne Session; Lcndres, IS88 [1891], Appendix C, p, 4. EXCURSION TO THE ISLE OF WIGHT. 147 might be gathered from Prof. McKenny Hughes' prefa ce to the" Reports ofthe British Sub- Committ ees on Classificat ion and Nomenclature." * This sugge stion was, in brief, priority ofnomen­ clature to the first correct interpretation where a clear description had been published with corre ct references to locality, &c. It was clear that, shouldt his be the rule adopted in the future, Forbes' name" Hempstead Beds " would have to stand, since he was the first to interpret and describe the beds correctly. I t would be absurd to go into an author's reasons for giving a name ; such a proposal would certainly tend to the reverse of unification. Many writers had regretted the name given by Forbes, non e, however, had hitherto ventured to alter it. There was a curious error on the latter point in a note to Mr. Starkie Gardner's Report on the E ocene, Oligocene, and Miocene, on page 58 of the Geolo gical Congress Report, referred to above. Mr. Gardner had remarked, "The Geological Survey intend to alter the spelling in accordance with a suggestion of Prof. Judd's, Quart. Journ. Geol, Soc., 1880, p. 168." There was, however, no suggestion of the kind on the page, or in the paper referred to. On the contrary, Prof. Judd had laid stress on the inconvenience of making any alteration ; and he had concluded that Forbes had been labouring under a mistake as to the correct spelling of the local name. According to Bris­ tow's account, however (Memoir, p. 89), Forbes had objected to the" confusion which might possibly arise from the similarity of the. .. name to that of a village near London already celebrated as a locality for Lower Tertiary fossils "; an objection which would hold good against either spelling, but which would not arise in connection with the localities mentioned by Prof. Judd (op. cit., p. 168) in Essex and Hertfordshire, which were not celebrated as collecting grounds for any fossils. The Director, therefore, adhered to the name" Hempstead " Beds, since that was the .nam e that eventually would have to stand, unl ess a special rule were arranged to meet that case only-which was scarcely probable. The series of formati ons bracketed in the Table as " Oligo­ cene," are the celebrated Fluvio-marine Beds of the Isle of Wight. They are not known to occur elsewhere in England ; the Middle and Lower Headons, however, extend to the neighbour­ ing shores of Hampshire. These beds were first described in 1816 by Thomas Webster, in the geological chapters appended to Sir Henry Englefield's handsome topographical work on th e Isle of Wight. Although Webster's description was not quite correct, students of some recent papers on the same beds should notice that.veven at that early date, the importance of the Middle Headen Beds was recognised. Webster divided the whole series into a Lower Freshwater, Upper Marine, and Upper Freshwater Forma­ tion , taking the Headon Hill section as the type. Hi s description of the latter was fairly correct, but he erroneously referred the * op . cit . »tt., Appendix B., pp, ' 3-' 5. 148 EXCURSION TO THE ISLE OF WIGHT. higher beds of the Fluvio-marine series, which are poorly developed or wanting on Headon Hill, to one or other of his divisions, and, curiously enough, placed some of the Thames Valley drift deposits on the same horizon as his Upper Freshwater Formation. In 1853 Forbes (Quart. Journ. Geol, Soc., vol. ix., p. 259), showed the proper relations of the different beds to each other; and his classification, with slight modifications, is still in use. The Hemp­ stead Beds form by far the most important member of the whole series, although, from containing a considerable thickness of un­ fossiliferous beds, they have not received the same amount of attention as some very much thinner divisions. They are chiefly Freshwater and Estuarine Beds, and pass palreontologically and stratigraphically into the Bembridge Marls below. In the upper part of the Hempstead Beds marine conditions become gradually more pronounced: the lacustrine and estuarine conditions of the lower portion give place to beds with Corbula, Meretrix, Ostrea and Voluta. Forbes placed the division between the Hempstead Beds and the Bembridge Marls at the" Black Band," a strongly marked bed of carbonaceous clay, full of fossils, which he con­ sidered to have been a land surface. He also thought that this bed marked a change in the fossils; and believing that it contained the first examples of a Rissoa (now known as Hydrobia Chaste/i), he took that fossil as the first sign of the new order of things. Our knowledge of the paleeontology of these beds has increased since those days, and the fossil in question is now known to occur a few feet lower down. The palseontological change is moreover so gradual, and the passage is so perfect, that no one bed can be pointed to as the first of a new order of things. Prof. Judd (op. cit., p. 168) would confine the term Hempstead Beds to the upper or marine portions; even then, however, the dividing line would have to be an arbitrary one, since the conditions fluctuate and change so gradually. Now, for stratigraphical purposes, the most useful dividing line is a persistent bed which is easily recognised over a large area; and it is just these requirements which the Black Band alone of all the Hempstead Beds fulfils. Mr. Reid (Memoir, p. 190) has, ~ therefore, very properly retained the Black Band as the base of the series. Until the recent re-survey of the Island, the Hempstead Beds were only known to occur for certain in the north and south syncline at Hamstead Cliffs. Mr. Bristow, however (Memoir, p. 95), quoted good evidence that, but for the absence of sections, they would have been found under the gravels on the high ground south of Parkhurst Forest. Mr. Reid, whom the Belgian boring apparatus rendered indepen­ dent of sections, traced the Hempstead Beds, by means of the Black Band, over the greater part of the Tertiary outcrop in the Island, and thus effected an extraordinary change in the appear­ ance of the new' edition of the Survey Map. At the close of the Director's remarks the President observed EX C UR SIO l' TO THE ISL E OF WI GHT. 149 that he could not agree to the use of the term " Hempstead Beds" for strata that were intended to be typically represented at H am­ stead. In his opinion no amount of priority could justify a manifest absurdity. H e then drew att ention to the flint gravel that capped those beds, and, calling upon the memb ers to lift the ir eyes to the distant horizon where the chalk hills were seen from which these flints must have been derived; invited them to realise the immense amount of denudation requ ired to carve out the broad intervening valley, a work which had been accomplished since those flints had arri ved where they were then lying. The doubtful weath er and the un inviting bank s of mud deterred most of the members from descending to the shore as had been proposed. Some of the more ene rgetic, however, braved every obstacle and made their way over the slopes, col­ lect ing fossils on the way, to find, if possible, the lower horizons ; and this they succeeded in do ing at the cost of sundry scratchings from the matted undergrowth on the hillside. In heavy rain the party returned to Yarmouth, seeing nothing of the Bembridge Marls on acco unt of the state of the tide. About half-past one, however, when the return to Totland Bay was begun, finer weather permitted adherence to the original programme. Proceeding to the shore at Colwell Bay by way of Bram bles Chine, the party walked in a northerly direction toward s Cliff End. T his side of the bay is freq uently neglected by geologists ; but, since it shows some points of interest, the Director urged the memb ers, not entirely with success, to postpone their examin ation of the fossiliferous beds in the middle of the bay. It is a pity that the reputation of the last-named collecting-ground should cause the beds furth er north to be overlooked; since, were the y more frequentl y worked, the slopes would doubtless become as access ible as at other places, instead of being, as now, much over-grown. The fort at Cliff End stands on Bembridge Beds ; just at the sea­ wall, however, the Osborne Beds may usually be seen. T he latter formation and the U pper H eadon differ considerably here from their typical development on H eadon HilL The pale olive­ white limeston e of the Osborne Beds, which is eighteen feet thick on H eadon Hill , has here entirely disappeared, and is replaced by clays and marls. The Upper Headons have at the same time beco me more sandy, and the Upper Headon Limestone, twenty­ seven feet thick on Headon Hill, has dwindled to one foot eight inches. Under the gravels immediately to the north of Linstone Chine a double contortion of the clays of the Upper Headons attracted considerable attention (fig. i } : a recent slip of talus from the face of the cliff had left an unu sually fine exposure. In calling attention to this rem arka ble section, the Director stated that he had failed to find any published descript ion of it, although EX CURSION TO THEISLE OF WI GHT. its position was indi cated on the plate att ached to Messrs. Keeping and Tawney's paper. Mr. Clement Reid has since kindly pointed out that the feature is mentioned, without par­ ticulars, in a note on page 132 of Forbes' Memoir. ' The Director expressed the opinion, in which Professor Blake concurred, that thi s dis turba nce had no relat ion to the gravels which overlaid the contorted clays, but that it was one of the results of the great fold­ ing of the rocks of th e Island, with which folding it was in con­ nection : a close examination of the contorted beds showed that they were continuous in both directions with beds in normal condition.

FrG;I .-CONTORTED U P PER HFADON CLAYS U NDER LYI KG G RAVE LS I N TOTLAND BAY.-J'. F. B la/;e.

Returning to the middle of the ba y, where the Middle Headons come down to the shore, the Director addressed the re-united party on the whole Headon Series forming the coast-section from Colwell to Alum Bay. The Headon beds are better displayed her e th an elsewhere, and it was concern ing this section that th e controversy took place which was raised by Professor Judd in 1880 (op. cit., p. 137). Outside the area immediately under dis­ cussion these beds are displayed at the east and north of the I sland in Whitecliff Bay and near Osborne, and on the other side of the Solent at Hordwell, Brockenhurst and oth er places. The usual divis ions of the series have already been given. The Upper Headons are of fresh water origin. At H ead on Hill the upper twenty feet or so are clays, the remainder of th e division consisting of the th ick fresh water limestone already alluded to with Limncea longiscata and Planorbis euolllphalus. Over Totland Bay and Ward en Cliff the Upper Head ons have been removed by denudation, and the alterations that th ey have undergone when they re-appear in the section at Colwell Bay have already been mentioned. The Middle Headons are chiefly of marine origin, and, according to the view held . by the Director, become more and more marine the further they are traced to the north. They are EXCURSION TO THE ISLE OF WIGHT. chiefly blue and green clays, with a few thin beds of sand and occasionally limestone; their general appearance in the section is, however, distinctly blue. The Middle Headons may he found under the Upper Headon Limestone on the extreme north side of Alum Bay, and they have been traced by the Director all round Headon Hill to Widdick Chine in Totland Bay. Mr. Reid (Memoir, p. 137) was not so fortunate in finding sections here, always a matter of chance according to the condition of the slips. In Totland Bay the Middle Headons do not appear ill the coast section; but just east ofthe Hotel a splendid section is now open in the new brickyard, a little to the north-east of the old one mentioned by Mr. Reid (Ioc. cit.). In Warden Cliff the Middle Headons again appear over the limestone of the lower division: thence they may be traced in the cliff to How Ledge in Colwell Bay, where they come down to the shore. From the latter place they form either the whole or the lower part of the cliff, until they dis­ appear under the Upper Headons near Linstone Chine. The fossils of these beds are of the greatest possible interest, and it is from the neighbourhood of the large oyster-bank between Colwell and Brambles Chine that the rich molluscan fauna that has been recorded was chiefly collected. The spring is the worst time of year for making a collection, as the slopes are then far too soft to work upon. In the autumn, however, the mud-glaciers are dry, while the wind has removed the matrix and hardened the fossils, so that with a pair of forceps, thousands of specimens may be gathered in an hour. The Director is in entire accord with Messrs. Keeping and Tawney* as to the stratigraphy of these beds; never­ theless, the list of marine fossils recorded by them from Headon Hill was a great surprise to him. There can be no question, however, but that marine shells, irrespective of species, are far more plentiful at Colwell Bay than at Headon Hill. Allowance must, of course, be made for the superior exposure of the beds in Colwell Bay. It was to test this question thoroughly that the expedition round Headon Hill, already referred to, was under­ taken in September, 1888. On that occasion particular attention was paid to the sections at the south-west angle of the hill; and it may be stated as an example of the author's argument that, in a good exposure there of some dozen yards, but three specimens of Pisania (olim Buccinum) labiata were found. If Mr. Keeping's collection was made at the north-east corner of the hill, there may he little or no difference of opinion after all; for the result of the author's investigations on the occasion referred to was not only to confirm his previous observation that the Middle Headons are more marine at Colwell Bay, but also to show that there is an appreciable difference in the same respect between the two ends of Headon Hill. Now, at WhitecliffBay and near Brockenhurst in the New Forest, there is another development of the Middle ,. Quart. j ourn. Geol. Soc., vel. xxxvii., 1881, p. 85. EXCURSION TO THE ISLE OF WIGHT.

Headons, and, from the evidence. of their fossils, those beds are usually placed at a lower horizon than the lowest Middle Headons at the west end of the Isle of Wight; that is to say, the Brocken­ hurst Beds are supposed to be absent from the Isle of Wight. There is, however, no evidence of a break below the Lower and Middle Headons; consequently it may be argued that the so­ called Brockenhurst Beds must be synchronous with the lowest beds at Colwell Bay, although the fauna belongs to a different zone. But this is just what should be expected on the theory that the infusion of fresh water, of which we have evidence, * came from the south: away to the north and east, further removed from the influence of the river, forms more purely marine would be able to exist. It is contended by the author that a careful examination of the list of fossils given by Messrs. Keeping and Tawney will be found to support this view; also that a collection of fossils from the small exposure still open at Roydon near Brockenhurst will show a greater abundance of forms from deeper sea, such as are rare at Colwell Bay, and especially a less frequent occurrence of estuarine forms-facts which support the same view. In a series of more or less estuarine beds of inconsiderable thickness, the author doubts the wisdom of separating "zones" ; that is, if the same meaning is to be attached to such divisions as, for example, in the Lias. As a means of reconstructing the former physical geography of a district, in the way begun above, some such classification as has been made may be defended; but, since these beds constantly thin out and give place to something slightly different, their further sub-division is superfluous. The oyster-bank in the middle of Colwell Bay is a peculiar development at this place. It was commented on by Webster in 1813 (Of. cit., p. 230), and appears to have altered very little since, as it has been mentioned by every subsequent writer. The Lower Headons are chiefly of fresh water origin, but contain some beds with Cyrena and Cerithium. They are thin limestones, clays, marls and sands, and vary a good deal along the section. Two beds of limestone, however, although varying in thickness, are constant, and are accordingly extremely useful for stratigraphical purposes. The upper of these, the How Ledge Limestone, forms the top bed of the division. When the slips are favourable it may be seen in the section at Headon Hill above Alum Bay immediately below the blue beds of the Middle Headons. It has been identified by Messrs. Keeping and Tawney in the same position at the north-east corner of Headon Hill, and it forms the feature-marking band in the upper part of the cliff on the opposite side of Totland Bay. From this point it descends, through Warden Cliff, to the ledge from which it takes

* Many fresh-water and estuarine shell", OCcur in the most marine beds at Colwell Bay, and Mr. C. Reid tells me he has found Chara in the Venus b~-T.L. EXCURSION TO THE ISLE OF WIGHT. 153 its name a little south of the centre of Colwell Bay. Warden Ledge, forming the dangerous reef out to sea off Warden Point, consists of a concretionary sandstone some twenty feet lower in the series. The second thin limestone, referred to above, is found some seventeen feet below the sandstone last mentioned. It rises from the shore about the middle of Warden Cliff, whence it may be traced continuously southwards round Totland Bay to the neighbourhood of Widdick Chine. It now only remains to speak of the undulations which have affected the whole of the Headon Series alike. The true dip is to the north, and this is well seen at Alum Bay. At the north-east corner of Headon Hill, however, there is some evidence of a local dip to the south; and this induced Forbes to consider that Totland Bay was a denuded anticline, ,a view which was adopted in the old edition of Sheet 47 of the Horizontal Sections of the Geological Survey. Professor Judd (op. cit., p. 143) altogether disputed this idea, although, as is pointed out by Messrs. Keeping and Tawney, his statements on the subject were rather conflicting (o/J. cit., p. 86). In his recent re-survey of the Island, Mr. Clement Reid (op. cit., p. 137) has proved the existence of a distinct flattening of the beds over the area of Totland Bay. At Warden Cliff the true northerly dip is again visible, and the same continues throughout Colwell Bay. Noteworthy features in the latter place are the overthrust faults visible in the How Ledge Limestone near Colwell Chine, which are connected with the general folding of the rocks of the Island. The so-called Venus Bed in Colwell Bay attracted consider­ able attention as the horizon at which the best fossils may be found. It is in general so much confused,partly by- sinking and partly by the mixture of other beds with its surface, that its true character must be seen in such places as show a freshly-broken cliff surface. It is full of the beautiful fossil Meretrix (olim Cytherea} incrassata. Attached to the surface of one of these shells the President found a colony of five or six Balanus unguiformis, probably an unique specimen of its kind. After a considerable stay in Colwell Bay, the party proceeded round Warden Cliff, the various horizons noted above being studied on the way. Totland Bay was reached about five o'clock, ann, while some members had tea, others accompanied the Director to the brick-yard, always an important section as the Middle Headons are exposed there. The old brick-yard, which showed a section in the oyster-bed with occasional Meretrix incrassata, and other fossils, has been built over. The new brick­ yard, now first seen by the Director, exhibits a splendid section of considerable length in the typical sandy clay of the Venus Bed, full of frferetrix incrassata. This new exposure lies immediately behind the old one, where certain drying processes were previously carried on. It appears to occupy slightly lower ground, and, so 154 EXCURSION TO THE ISLE OF WIGHT. far as could be ascertained on this hasty visit, the beds belong to a slightly lower horizon than that of the old section. At Widdick Chine the party re-assembled, and, although the Chine itself is entirely overgrown, small exposures of the Pleisto­ cene tufa were found in the sea face of the bank. This deposit is probably of no great age jit contains the remains of recent land­ shells, and several specimens of Helix nemora/is and other species were found by members of the party. It was no doubt formed by springs given off from the thick Upper Headon Limestone higher up on the hill. Associated with the tufa-beds are certain lacustrine deposits with remains of recent fresh water molluscs j these beds were described in detail by Forbes (Memoir, p. 8). The party next proceeded to the north-east corner of Headon Hill, where the section (fig. 2) described by Messrs. Keeping and Tawney was measured. Under the thick Upper Headon Lime­ stone the blue marine beds of the Middle Headons were seen, and from them some characteristic marine fossils were collected, as well as "Cerithiu1ll concauusn," which is here most common. The section was not, however, in good condition. The optical illusion which has led to the idea that the How Ledge Limestone is continued into the Upper Headon Limestone is particularly noticeable from this point j but the Director pointed out that in Colwell Bay the marine beds had been worked by the party over the How Ledge Limestone, and that that succession had been followed round Warden Cliff into Totland Bay. At the spot where the party was then standing the marine beds were seen under the thick Upper Headon Limestone, which formed practi­ cally the base of the Upper Headons, as the How Ledge Lime­ stone formed the top of the Lower Headons. The marine beds lying between the two formed the Middle Headons, and it should not be forgotten that their thickness was only some 33 feet. In the intervening area of Totland Bay the Director called attention to the ledge formed in the cliff from Warden Cliff to Widdick Chine by the lower bed of limestone of the Lower H eadons previously referred to. Taking with this evidence the two exposures of the Middle Headons at Freshwater Church, and in the Totland Bay brick-yard, the Director claimed that the inter­ pretation of the beds which he had given was the only one that agreed with the facts which he had been able to show to the party. If, however, anybody wished for further evidence he would recommend them to follow up Mr. Reid's mapping of the Upper Headon Limestone to the rear of Totland Bay (Memoir, p. 137), and carefully to compare the beds. It was not possible for the party to do this on the then occasion j it might, however, be mentioned that the bed in question had been traced by Mr. Reid to Amos Hill at 110 feet above the sea, that locality lying nearly due east of the Totland Bay brickyard where the Middle Headons occurred at 93 feet above the sea. B E \ lI UH 1)( i E L D I E ST O :-.; E ..... 2~ fcct , r OSWHC, E BEDS ; 0 . , I V"I'EJ.: l h :AP'l :" 49 ,. (rotul r.

~ ft. in. La mina ted grecni-h ,:by, with br oken I"at'udi ll il . ~ I

:< \\ 'hity-hrown to huff sands, with Iarcr~ of ligniric matter. 6 ~ -g 0 t i-.·:·.<,: ...... "

t8~}.~~~~ Greyer",."" below. 1'.,lalll.,lII)'a, J/da"i" lIIurk"(,,, U"i,', I'"Iudi"" 1.'''1". l 0 3 c- ~ LiJ.:n itc. Grcyb,h.grc(·11clav... C. ,'(II' ) Vlcaryn concat -a, .1lar,;'ullll.,ittalll , .\'cn·, ( 9;".-1('. fri(fISUIII-hctl wi th f t i n u l'O I l( ' rl1.'ll , .I/ ( · ltll~ ill ntu ricat a , &c. I 6 in . ...I:im'!trl!.limc:-tonc , :-'Ofl anti cr umhl ing , with a thi n lig ni te a t top. .. .\ cn.! lgn!\·gn,:cll ckry, wid. rootlet s. I ft.0in. ;". I ' 0 LiIllJUra· linh:..tone.

St ilTgreen cb ys with con choidal fractu re in d ryi ng. I , Oy-rer-bcd towa rd.. the basco I 9 Fnsus Itd,illl lt.\·, .1r~ · /. /Il.(( illItl, .1/. III u rica ta , ! C l:1y becoming greyer t . \·~ ril tl (lt o 'l tl , CO'. 1'a r itl bi k . C. ! :-" fud l;ci" ,:" below. Fo..~il.. I UIII , OSI """ ,,'dala, .llyli lus ajJi nis, C,)l bicu la. ,1/',r.·,'la, Lncina (·,}/';'ellou-is. z J u .\hern a ti nJ,: grey and och ry cla ys. -<: :.:.: t Y l lt . incrassn t a • .1lacl ra / a sfJ:::i a f a . " I "ollls.hed,·· riche..t po rt ion , con - .11)'a a lt. ~· 1t sfa l tl , ('"rbii'lIla tJhlJvtl ft l, 0 J ta ins ..cattered Hint», brown ..andy .\"ueula lissa, .\·. Ilt"w(IJntllsis, j' rt:~ _ - c1 :~r hCCO I!,il1~ green clay and sanu'"rl ddfoid,'tl, "tSIiS Itlbl:afus, ~·tll/u~/. 11CIOW. 1· 0 11.. ,·I,m .:tl' tl, ,1e'ltl/WISIS /USi/IJrJ lflS . - V o/ultl stinostl, Vic. concana, .\·a· .-: T hin arcy sandy clays, tica Stndcri, wcat hering brown. I I s 0 Cy tlu""a in cra ssa ta .:\:c wnncred throughout. I .11;' (1 fl ll.::usta /a , c..pccially near k,..e, Ch ocolmc-brown cr blnckisb ...ands l rri~" , !ldttJidl'tl, Cer, /' S' · /( dl ~ ~Il C t lll ~/ 1 I l .\ a t /(..tl /tl l,~. " r ta , .1/,.:ltln./ usi/orlllls . 2 6 Trt:C-Oll e'C,d i a -I>c,I.

I () 6 Hlacki..It-brown ..a nd!', -,",·rilina·bed: .V. eM/ca" 'il, .l / .(IISi/(JrJllis, C. obot-ata , l I-I J ~'-----="-l "> Ve ry !'ti lY te nacious clay . l .iIllJltra.1illlcstolle, •. II ow- Led g e lim eston e " : I~ . /oll/-,;iscllla,/usi/'ol lllis,&c. 2~ -4 6 ;. ( g :.:.: I I S 6 }~~f/}:t \\' h i l \ ·. )IfCl\ VU or yell ow !'alH!" a nti saud-rock , wit h lay ers or /'al lld iJltl ;\lHI I "l,iall/(I/Il)'tl. :·>:·:-:::::"·: •". ~ •• 0.0 ~ 1 • • 0 • T he ba. C concealed by unu hie an d uudercliff.] I .:;~~ l l FIG.•. VERTICA L S ECTION OF BEDS AT T H E NORTH-EAST CORNE R OF I-IEADO N H ILL. (Scale, 8 feet to th e inch.) Reprinted, witholtt alteration, from (jlJART . j O UKN. G EOL. So c., \'01. xxxvii., p. 91. EXCURSION. TO THE ISLE OF WIGHT.

Saturday, March z8th.-Leaving the luggage to be forwarded to Blackgang by road, the party started over Headen Hill for Alum Bay to complete the study of the Tertiaries of the district. Leaving the high road by the old footpath, now notified to be dangerous, the party was conducted to the section in the fresh­ water Osborne Beds immediately above the position of the section shown in figure z. According to Prof. Judd (oj. cit., pI. vii., and explanation, p. 176), other marine beds should occur here; in this place, however, one finds the pale greenish-white concretionary limestone 18 feet thick, followed above by the white, coloured and mottled clays and marls 50 feet thick, both of the Osborne series. These beds contain few fossils: Limna:a longiscata, Planorbis discus and others, besides turtle remains, occur in the limestone and concretions. The two sections were found in excellent con­ dition, although, as usual, much tumbled about; the slips, how­ ever, were fresh and clean, and showed to advantage the different characters of these beds when compared with those below. Passing to the regular footpath the party rapidly mounted the hill and reached the spot where loose blocks of the Bembridge Limestone are usually to be found scattered about in the broken ground. Here a section of those beds in situ was found such as had not been seen here for many years. The heavy snows and rapid thaws of the preceding winter had caused the gravel talus to slip off the face of the limestone under one of the large gravel mounds so conspicuous at the top of the hill. It may here be mentioned that all the sections visited on this excursion were in particularly fine condition from this cause, some compensation for the severity of the weather. Although time was very limited, the President, Director, and a few other active members of the.party quickly scaled the cliff, and, after a few minutes' search, the Director procured the cast of a small species of He/ix. The Bembridge Limestone is 16 feet thick on Headon Hill, and the exposures seen must have approached this amount. In colour this limestone is of a dead white, thereby easily distinguishable from the other limestones of the neighbourhood. It is somewhat brecciated and concretionary. Its fossils are almost always casts; sometimes, however, the shell has been replaced by calc-spar, and such specimens are very beautiful objects. The brecciated pieces are compact in texture and hard, and ring under the hammer. The so-called "turtle's egg" concretions occur in regular lines: these are now looked upon as of mineral origin. A trace of the Bembridge Marls was seen higher up under the gravel capping; and here a curious phenomenon was noticed. To all appearance these marls are laminated, being coloured with great regularity white and brown; so that in a hand specimen, or seen on the cliff-face, no doubt of their laminated character could be entertained. If, however, the lines of apparent lamination be traced, they are seen to curve upwards at the top, as though the sandy marls were false-bedded. EXCURSION TO THE ISLE OF WIGHT. 157 Traced further still these lines are seen to be continued over the surface of the overlying flints. This shows that they are caused by successive and periodical infiltrations of ferruginous waters. At eleven o'clock the party assembled at the head of Alum Bay pier, whence a fine view of the section round the bay is obtained. To the extreme left is Headon Hill, at the top of which the thick bed of limestone ofthe Upper Headons is seen, followed by the blue-coloured Middle Headons; under the latter are the Lower Headons, which on the occasion of the excursion were rather more free from talus than usual. Then comes the chasm from which the Headon Hill Sands have been removed for com­ mercial purposes. This formation is a very interesting one, as it is not known to occur elsewhere. In the earlier Isle of Wight Memoirs (Forbes, p. 86; Bristow, p. 50), it was classed as Upper Bagshot Sand; but since the latter formation was shown by Messrs. Gardner, Keepingand Monckton to be on the horizon of the lower part of the Barton Clay, which is present here in full force under­ neaththe sands in question, it follows thatthese beds belong to a later Eocene age than is represented in the London area; the Headon Hill Sands are in fact passage-beds from the Eocene to the Oligocene. They are almost entirely unfossiliferous, and at Alum Bay quite so. At Whitecliff Bay casts of Teliina and Panopaa have been found, and upon this evidence the beds have been placed at the top of the Eocene rather than at the base of the Oligocene, their original name being restored to them. It is difficult to estimate the thickness of beds that have been carted away for glass-making; Mr. Reid gives it at from 140 to 200 feet, which is probably a full estimate. The Headon Hill Sands are exposed in several parts of the island. They underlie Headon Hill itself, and may sometimes be seen just at the shore on the Totland Bay side. Mr. Reid (Memcir, p. 135) has also proved their existence in that neighbourhood by boring close to Widdick Chine, at a spot where, according to Prof. Judd's diagram (op. cit., pl. vii.), "brackish water" beds should appear. After the Headon Hill Sands come the Barton Beds (j, fig. 3), the first group of beds that is nearly vertical. As the base of this series the conglomerate of iron-cemented flints that stands out so boldly in the cliff used to be taken (Bristow, Memoir, p. 45). In the section, figure 3, Alum Bay Chine is shown cutting the Lower Bagshot Beds; but where the Chine comes down to the shore it is in the upper part of the Barton Beds. For palseonto­ logical reasons, however, it is now taken at 44 feet I inch above that horizon, in the midst of a mass of dark sandy clay. Such a base as this could not be pointed out in the section without a measuring tape; and as the passage from the Bracklesham into the Barton is an extremely gradual one, both lithologically and paleeontologically, it is open to question whether this peculiarly modern reading is any improvement on the older one. It must H E.I I)():-I HI LI.. 1111; 11 1l01 1·:" . s. ~~ ~~ 1<. ~ • \ , ~r ,.-'-. <--+--:;-~,,--- -:.-c=-- <.f: .---=-=-.'?: - - - - - :::. :: L 4 (I) P la tea u G ra vel. I (,l.') (e) U) Hem bridge Bed ,;. (j) ( h) ( /) Osbor ne Bcds. (z) (II) (Ii) l I cad on Bed s. (d)

F IG. 3.-S ECTl O:-l ACIW SS :\1.I:~1IlAv F1{()~1 I [ EAll O:" 1[ 11.1. TO I [ IGII Dowx .- Al lt ,. I I. II'. /),.iJlo/i·.

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(' /) I Icmpstcad Bcds. (/) Ha rton C lay. (l) {"pper Cha lk . (h) BClllbridg'e Bcd" with Lime- (,c) Hracklc-h.u n and Lo wer Bag- (I) :\I idd le C halk. s to ne a t base. shot B('d , . ( III) Lower C ha lk . (e) Osbo rn e Eeds. (n) London C lav . (1/) (; pper c;rcc nsam l. (rl) II cad on Beds. (I) Reading' Ik d.', (0) Ga ult, &c. (e ) l lcadon H ill San ds.

O~l FI(; , .j .-S ECTI O:-l FI{ S TAPI. ERS TO ST. G EO R(;J( 'S D O\l' :-I 0 :-1 .1 l. 1:" E BET II'E E:-I O SBOR:" J( I'r J(R 01:\ II R OCKE:" E:" ll.

SJ(CTlO:"~. - FRO~1 l l o kr zo xr. vr. S IlEET -Ii . OF T ilE G EO LOGI CAl. S li rn ' EY O F E:" Cl.A:" Il .vxn " ' A LES, EXCURSION TO THE ISLE OF WIGHT. 159 not be forgotten that pebble-beds (i.e., fossil beaches) must indicate a certain amount of change, hence the popularity they enjoy as division-lines; and were this particular pebble-bed at all continuous, the author would certainly vote for its retention as the base of the Barton series. The evidence on this point is, how­ ever, not at all clear;* in fact, Section I on plate iv. of the 1889 Survey Memoir is at variance with the text on page 115 in this respect, the older reading being still retained on the plate. The Barton Beds are typically developed on the opposite coast of Hamp­ shire, where they are noted for the richness, fine preservation, and abundance of their fossils, chiefly Mollusca. These denote com­ paratively deep sea conditions and a tropical climate. Although the list of fossils from Alum Bay is not so extensive as that of those from Barton Cliff, that may be due in some measure to the difference in, and smaller extent of the exposure, the vertical position of the beds here preserving them from waste. The Barton Beds consist chiefly of grey and dark sandy clays, with some darker clays, lighter sands and occasional septarian layers. They are not equally fossiliferous throughout: one of the best places for collecting is just against the pier-master's booth, whence several good specimens of the characteristic Volutes were obtained by members. Next come the Bracklesham Beds (e in fig. 3), the equivalent of the Middle Bagshots of the London Basin. They extend in the section from the undefined position here taken as the base in the series above to the commencement of the coloured sands for which the bay is famous. They include at the base the four beds of lignite that form such a prominent feature in the cliff. They are typically developed near Selsea Bill in the bay from which they are named, and form a much more important series at Whitecliff Bay than at this end of the island. At Alum Bay their fossils occur as impressions only: these show shallow water conditions and a sub-tropical climate, whilst the presence of the lignite­ bands proves the proximity of land; in fact, the vegetation of which they are formed appears to have grown on the spot, since each bed of lignite rests on a regular bed of underclay with root­ lets, as in the Coal Measures. The Bracklesham Beds here con­ sist of dark sandy clays, followed by light tawny sands, white marly clay, and then the dark clays with the lignite.

* It is instructive to compare the thicknesses of the different members of the Eocene at either end of the island. The following are the figures from the 1889 Memoir. Alum Bay. WhitecliffBay. Headon Hill Sands 170 feet 184 feet. Barton Clay 255 " 162 " Bracklesham Beds J 55 " 653 " Lower Bagshot Beds 662* " 100 " London Clay ... 233 " 320 " Woolwich and Reading Beds 84 " 163 " 1,559 feet. 1,582 feet. What can he said when we have to confess that this is the present state of our knowledge! 160 EXCURSION TO THE ISLE O~' WIGHT.

Following these come the Lower Bagshot Sands (d in fig. 3), the coloured "Alum Bay Sands," They are entirely unfossili­ ferous in the upper 450 feet; Mr. C Reid suggests, accordingly, that they may be the" decalcified equivalents of the marine beds of Whitecliff Bay and Bracklesham." In the pipe-clay, a little lower in the series, the celebrated leaf-bed used to exist; it is now, however, entirely worked out. Mr. Starkie Gardner, writing on the Flora of this leaf-bed in the 1889 Survey Memoir (p. 106), considers that it is the" most tropical of any that has so far been studied in the northern hemisphere." Next to these is the London Clay (c in fig. 3), which is here rather more sandy than in the area where it is typically developed, and which contains occasional lines of flint pebbles, probable evidence of the shoaling of the London Clay sea in this direc­ tion, There is a distinct basement-bed here, some 6 feet in thickness, in the bottom layers of which pebbles of the underlying red clay are sometimes found, pointing to an eroded surface. The marine fossils of the London Clay appear to indicate a sub-tropical climate. At Alum Bay the clay, comparatively speaking, is fairly fossiliferous; Ditrupa plana is plentiful at the base, and a walk over the slopes is sure to result in the finding of several species. Here the fossils are not pyritised, and can be preserved without difficulty. In considering the thickness of this formation, its nearness to the point of origin of the sharp monoclinal curve must not be overlooked; sections of these vertical beds will be found to measure more at the top of the cliff than at its base, and, of course, the nearer we approach the Chalk the greater has been the pressure and consequent squeezing of the softer formations. Below the London Clay are the Plastic Clays of the Woolwich and Reading Series (b in fig. 3), resting on a slightly eroded surface of Chalk, with small rolled flint pebbles at the base. This junction is not often well seen; a striking feature at this place, however, is the shattering of the flints in the Chalk itself, a phenomenon that shows something of the force to which they have been subjected. The Woolwich and Reading Series here consist almost entirely of mottled clays, in which red, white, purple and rich brown are the prominent colours. No fossils of any importance have been found in them. The great monoclinal curve forms a prominent feature in the section as seen from the pier. The upheaval of the Chalk to its present position has forced the softer Tertiary beds lying above it into the vertical position they occupy in the middle of the bay; indeed, certain beds of the Lower Bagshot Series have been thrown completely over, and have a slightly reversed dip. Towards the left the effects of the curve are less and less, until the upper beds on Headon Hill have little more than a northerly dip; still there is evidence that even the Bembridge Beds on the top of the hill have been affected by this great movement. So far then the EXCURSION TO THE ISL E O F WI GHT. 161 evide nce pro ved that this disturban ce was of later dat e than the de position of the Rembridge Reds. Mr . Clement Reid, how­ ever, through extensive use of th e boring apparatu s, has proved (Memoir. p. 242 ) that, along th e central ran ge, the H em pstead Beds are also affected by th e general tiltin g up (fig. 4). Nowhere, as Mr. R eid says, do we find evide nce that an y of the later Ter­ tiaries thin out against the anticlinal folds ; consequently, the dis­ turbance could not have begun until after their deposition. We know, however, that this upheaval was pre-Pliocene, because, as Mr. Reid has pointed out in 'Nature,' at Lenham beds of that age rest directly on th e Chalk ; conseq uently th e great up­ heaval that formed th e London Basin, the Weald, and the doubl e set of folds in the Isle of Wight took place in Miocene times, when, as there is every reason to suppose, these islands formed a land surface. The Director inform ed the party that he had held the abo ve view for a long time, in spite of criticism, and that he was glad to have Mr. Reid's authority to support him. At th e same time, the Director expressed his obligation to Mr. Reid for advice and assistance in arranging th e excursion; while he ventured to congratul ate him self on the fact that, though the party had seldom tra velled on the high road they had not once missed their way.

-( ---..,-

F IG. 5.-0VERTUR NI NG OF T HE T ERTIA RY BEDS IN A LU ~I BAY .­ Y. F. Blake.

After the Director had thus explained the section, several members walked alon g the shore as far as the Chalk, th e jun ction of which with the overlying sandy bed -included with the Pla stic n ay in the Woolwich and Reading Series-was part ic ularly well seen. At this spot. also, the remarkab le overturning of the lower pa rts of the T ert iaries was very noticeable. The Pla stic Clay is actually overturned ; and at the top of the cliff it becomes II 162 EXCURSION TO THE ISLE OF WIGHT. horizontal, with its upper face downwards, proving conclusively that the Chalk has not only been tilted up vertically, but that it has been pushed over from the south, and that it must at one time have actually overlaid the Tertiaries at this spot (fig. 5).* At twelve o'clock the direction of the party was taken by the President, who immediately led the way to the top of the Downs, and along their northern slopes to a quarry in the uppermost beds of the Chalk. This Chalk is the zone of Marsupites, and contains Belemnite/fa mucronata. The latter fossil, however, was not actually obtained, though specimens of Terebratula carnea, Ananchytes ovatus, and the plates of Marsupites were easily procured. A halt was made at the Beacon, on the summit of High Down-whence, the day being clear, an excellent view was obtained, and the Direc­ tor took the opportunity of pointing out the general structure of the island. "The Downs on which we are standing," he said, " may be considered the back-bone. It curves in a crescent form from east to west, from Culver Cliff to the Needles; and, further away in the same direction, it may be seen at Durlstone Head. This is one of the master-lines in the structure of the South of England. It forms the northern half of an anticlinal, the southern part of which once occupied the Channel. In the centre of the crescent, in the eastern distance, the rocks may be seen bending over, as it were, and becoming horizontal in St. Katherine's Down, between which and the main axis, the once continuous Chalk has been denuded, leaving the curved valley, whose western portion we see debouching in Brook Bay. It is in this valley that we find the true summit of the anticlinal, where the lowest beds of the Island are exposed. Turning our eyes northward, they range over the whole extent of what is known as the Hampshire Basin, the bounding hills of Chalk, which rock crops up again on the other side, being just visible on the horizon. This basin forms the com­ plementary synclinal; and, as it contains a development of Ter­ tiary rocks distinct in character from those beyond its boundary, the bending of the strata must have commenced in early Tertiary times, though continued, as has been seen already, at a later date, From this point can also be descried the heights of Hamstead, where on the previous day we found Chalk flints, which taught us the enormous extent of later denudation." As soon as the party could tear themselves away from this splendid panorama, they descended to luncheon at the Albion Hotel, Freshwater Gate. The valley in which this stands is a transverse breach in the continuity of the Chalk Downs, and is filled with gravels of fresh water origin, said to have yielded the

* This observation was made by the President. I much regret that, since I was other­ wise engaged at the time, I can express no opinion on the subject. Nothing, however, has hitherto led me to suppose that the Woolwich and Reading Beds are here inverted as sug­ gested above. The beds have been crushed and are much disturbed, and the cliff is always more or less covered by slips. I have previously noticed the London Clay slipping down over the Plastic Clav, and vice 'l,trs/i.-T. L. EXCURSION TO THE ISLE OF WIGHT. tooth of a Mammoth, and yet there is no river there to form them: their origin then must date from a time when the geography was different. These gravels were noticed as the party ascended to Afton Down along the Military Road, the western end of which has already succumbed to the inroads of the sea. On this road, where it turns a little to the south, is a good section of the Chalk, which, however, could scarcely be examined owing to the great drifts of snow that still lingered in its deeper parts. Crossing it obliquely was seen at one spot a band of rubbly rock, which was pointed out as that which was called" Chalk Rock," and taken as the dividing line between the Upper and Middle Chalk. If this can be guaranteed to occur always on the same horizon, the lower division must here be comparatively thin, for soon after passing it we leave the Chalk entirely. This cliff, it may be noted in pass­ ing, has a botanical interest, it being the only known habitat of the wild stock, a specimen of which was gathered by Mr. Stratton, of Newport. A halt was made at the bottom of the path leading down to Compton Bay, and the Director, taking up his parable again, pointed out the various members of the Cretaceous System as they rose rapidly into the cliff. Here the Upper Greensand, Gault and Neocomian beds are all contained in a space of little over a quarter of a mile of shore, running obliquely to the stratification, and the members were called upon to notice and to remember their com­ paratively slight development at this spot. It is not a good locality for fossils; little time therefore was devoted to searching for them. Attention, however, was called to a remarkable deposit of chalk rubble which caps the cliff and reaches a thickness of perhaps twenty feet. This is spoken of in the Survey Memoir as merely the "run of the hil!." It is, however, so compact and exten­ sive that it must have required for its formation somewhat different conditions from those at present obtaining, perhaps only a greater height in the adjacent Downs before their chemical solution had proceeded as far as at present. The principal rock here is the Ferruginous Sandstone, which is carved into picturesque cliffs: between these and the lower cliffs of Wealden shale, the Perna bed is supposed to be seen. It had, however, to be taken for granted, for not a sign of it could be discovered in the slips. The party then entered on the long stretch of cliffs showing the various sub-divisions of the Wealden Clays, a section of which, pre­ pared by Prof. T. R. Jones, had been exhibited. A halt was made at the "C.vpris shales," which almost immediately came on, and numerous specimens of the characteristic Entomostracan, covering the whole surface with their tiny tests, were obtained. There was, however, no time to linger: though passing over the sepulchres of the weird Iguanodons, no man moved. their bones, for they could not in a moment be found. The members were hurrying on to see the remarkable" Pine-raft" before it should be covered by the tide. EXCURSION TO THE ISLE OF WIGHT.

In this they were successful; and, standing on one of the large trunks, which here lie prone, and form a bank stretching from the shore to below the water, Mr. Carruthers described their nature. They did not grow where now they lie, he said, but were drifted, like the logs in the Mississippi, till they stranded in one spot where the current could no more dislodge them. They were trunks of great coniferous trees, as might be seen from their internal structure: a microscopic section would show their characteristic medullary rays and the pitted nature of their woody cells; while associated with them might be found numerous species of the cones, which he had described. One of these cones the President was fortunate enough to obtain from the adjacent shales, and several members took specimens of the wood for microscopical examina­ tion. Coniferous trees, however, are not the only contributors to the Pine-raft; for remains of a great tree fern, known as Endogenites erosa, are sometimes found. This being a much greater rarity, was not met with on the occasion of the visit. In the neighbourhood of Brook another deposit of interest was noticed. Capping the low cliffs are seen some superficial deposits, which have been separated into two categories :-the Plateau and the Valley Gravels. The former, though at a lower level than usual, are considered, on account of their containing flints, to belong to the same group of deposits, as are elsewhere in the Island called by the same name; but it is to the latter especially that the interest attaches. They are not entirely gravel, but beds of brick earth are mingled with them; and, though they lie in the valleys of the present small streams, they are more widely spread and at a higher elevation than the modern alluvium; they may, therefore, be taken to represent the product of a period when the streams were more considerable and the valley not so deeply eroded. This involves the extension of the land to the south, and, in connection with what was seen at Freshwater, indicates that there was here a tributary to the river which once ran through Freshwater Gate to Yarmouth. At Brook the day's excursion practically terminated. A long but pleasant drive brought the members at last to comfortable quarters at the Blackgang Chine Hotel.

Monday, March 3oth.-After a restful Sunday, during which members became familiar with the general aspect of the district and particularly of the coast, the party started early to examine the complete section of the Neocomian beds here exhibited. In order to commence at the base they walked over the cliffs to beyond the coast guard station and descended to the beach in the bay beyond. Here the horizon was recognised by the C)prt"s shales; and then, walking eastwards, members kept a careful watch upon the base of the cliff. At length, almost at the point, a hard band was recognised as reaching the shore, and this was ~ ./ .J:: ~ ~ .~:.:. t ~ r: ~.!: ;., Co wlc:ll"c ~ U "'"u Shep herd\. .5 .\I h<,,·rlidd Coastg unr d '"0 ~ Chine. ::: Chine . ~ Point. 3 S tation . ~

&·~ U.:\L«::i.(·.?·.:::07C~~:~~

'J: v: ( ;o rc :::S t. Cath erine's ClifT.::> Down . " r: .,: ~8 g;, .~ ~:" ·u."'E Blackgalll; ~ '. "...... ~ :r:: ~ Chine. ,. t· ::: Signal. v ~ u "-

~ ' ':'~ ~ ~ ~~ cr ._ \YI.lalc .g L~(~l t W alpen , :--::: . .- _

.~ =7:~~~""':"" ~ ''':'''''...:", "~ ~ Chi ne . U Clulle. Clune. V.tllcy ( ;r:l\'cl... _ ~ .. .:.... ~. .' ~ '.:~~ . •.

11(,,.i~JII(ll/ II/ilt . FtT/ jea l 100 '200 4 00 ~fd. Scau . Sc a l,·. _I __ l I 1

FlG. 6.-SECTION OF LOWER GREENSAND BEDS HOM ATHERFIELD TO BLACKGANG.-A. Strahan. 166 EXCURSION TO THE ISLE OF WIGHT soon found to contain marine remains, such as Exogyra. This is the Perna bed. The fossil, Penza mulleti, after which it is named, is not by any means common, and none were then found. Nevertheless, there could be no doubt that here there was a change of condition, and though there were clays above which closely resembled the clays below, and though this band itself was an insignificant one, yet here the Wealden was left and the

Punficld. Compton nay. Athcrfield Sand own Bay. Chalk Rock , :\liddlc Rock .

~[ cl bollrn c 1~ (J ck.

- ...... Lower Ch alk .

Upper Grecnsund .

Sandrock .

Fc!Oru gi nous Sands.

·100 Atherfield Clay .

Wealden .

" 000 Scale in feet.

FIG. 7,-COMPARATIVE SECTIONS OF CRETACEOUS ROCKs.-A, Strahan. Neocomian series entered. On closer inspection, too it was found that the top of the Wealden clay was not quite regular, and that it was somewhat discoloured, while pebbles of various kinds occurred in the base of the Perna bed itself. The Neocomian strata in the Isle of Wight are now classed by the Geological Survey, for the purposes of mapping, into four sub­ divisions. These, commencing at the base, are: (I) Atherfield EXCURSION TO THE ISLE OF WIGHT.

Clay, (2) Ferruginous Sands, (3) Sandrock, (4) Carstone. These differ sufficiently in character to be recognised inland; on the coast, however, more numerous subdivisions were recognised by Fitton in his" Strata below the Chalk," and these were partly veri­ fied on this occasion. The Atherfield Clay terminates a few hundred yards to the east of the Coast Guard station, and at one spot a recent slip gave members the chance of securing several specimens of the charac­ teristic crustacean, Meyeria oectensis, whose presence has given rise to the name" Lobster Bed." The change into the Ferruginous Sand was easily recognised, more particularly as the lowest rock of this series is a remarkable one called the" Crackers." It has a peculiar grey tint with irreg­ ular markings, and becomes remarkably hard under the action of the sea. The great masses of it strewn on the shore shew here and there dark nests of fossils. These, when separated and broken up, are found to be softer in the inside, and yield fine specimens. When obtained from the band in the cliff they are still better, but for this the opportunities are fewer. Members easily obtained examples of Ammonites deshayesi, Thetis minor, Natica rotundata, Tornatella albensis and Gervillia anceps. Further on, in the softer darker sands, were found other nodules of fossils; in this case Terebratula sella and the interesting coral HOlocystis elegans. The great oysters, Exogyra sinuata, commence in the Perna bed; but in higher beds they become more numerous, and often occur alone in bands. One such band was encountered before the party reached Whale Chine, and another a quarter of a mile from Blackgang. At the base of Whale Chine itself was seen a ledge of hard rock, commonly known as the Scaphite Bed; and though the Crioceras after which the bed is named does not now appear to be so common a's formerly, the earlier whorls of one specimen were discovered, and were worked out after great labour on the part of several members of the party. From what was seen, how­ ever, Whale Chine seems to be a natural collecting ground for fossils. Numerous large Gryphseas.fragments of Ammonites, and one large specimen of Ammonites hambrovii, were picked up wtihout trouble amongst the loose stones at its base. Some ofthe members were here interested in a mass of" con­ glomerate" which was found loose upon the shore. It turned out to be a good illustration of the cementing powers of ferruginous water, since it was really a mass of shingle which had been bound together by the decay of an iron plate from a neighbouring wreck. The rest of the walk to Blackgang was still upon the Ferru­ ginous Sands, and was comparatively uninteresting: one band and many scattered specimens of the Exogyra appeared, and a band full of nests of Serpula. At the foot of the Chine members had an opportunity of buying fossils, and procured some of the characteristic species, amongst which was a very fine example of 168 EXCURSION TO THE ISLE OF WIGHT.

Hoploparia Iangimana from the upper part ofthe series, which had been obtained after a slip of the cliff. The upper divisions of the Neocomian series do not reach the shore before Blackgang is reached, though the Sandrock comes down near Rocken End: they are best seen in the Chine itself. The southern side of this presents crag above crag, the highest of which is the Carstone, capped with a sloping bank of dark blue Gault, while those below it, not including the first cliff above the waterfall, represent the Sandrock. The members complained that Blackgang Chine was not half so wild and weird as the accounts they had read of it had led them to suppose. This, however, is not the fault of the accounts, which were true enough, no doubt, when written, but of the acci­ dents which have happened to the Chine itself. The northern half, which used to complete the amphitheatre, has now all slipped away, and become a broken undercliff of no great beauty or note. In the course of this walk the Director called a halt to draw the attention of members to the admirable opportunity here afforded of appreciating the various mutations of condition that go to make up a geological. epoch, such as that known as the Cre­ taceous. After the marine Portland Beds had given place to the fresh water Purbeck, a still further elevation of the land brought about those continental conditions which were represented by the Wealden river. Even during the continuance of these as a whole we find evidence here of a rise and fall of level, in the Pine-raft when the area of deposit was highest, and by the alternations of the sands and clays. At last with the Perna bed we have the introduction of the sea over the estuary area, bringing the shallow­ water oysters, Gervillia and Perna, while the mud was still being brought down. New and independent features set in with the Ferruginous Sands, indicating an open and wide-spreading sea, in which those and the overlying beds were deposited. This sea, becoming gradually deep, received the Gault deposits, and again shallowing, received the sandy Freestones. Finally another de­ pression resulted in the non-detrital Chalk. After a hearty lunch at the B1ackgang Hotel, a fresh start was made to examine the higher portions of the Cretaceous Series. Mounting by the footpath, members soon found themselves in a quarry on Gore Cliff, in which the Chert Bed and underlying Free­ stone of the so-called Upper Greensand were well exposed; and here some characteristic fossils were obtained. This chert is very largely composed of sponge spicules, easily observed by the aid of the glass, which give it a speckled appearance even at a distance. A little above the level of the quarry is another in the Lower Chalk proper. Here were met with many specimens of Ammon­ ites varians, and A. mantelli, with portions of Inoceramus. Thence the party mounted to the top of St. Catherine's Hill. This had formerly the reputation of being the highest land in the EXCURSION TO THE ISLE OF WIGHT.

Island, but the recent Ordnance Survey has shown that St. Boni­ face Down above Ventnor is 6 feet higher, being 787 feet as against 781 feet. This fact, however, did not spoil the view, which was a magnificent one, even the distant Isle of Portland being clearly seen in the western horizon. Part of the object in making this ascent here, which, as the day was bitterly cold and the wind cutting, required some inducement, was to see the flint gravels that are mapped upon the summit. These are not really gravels in the ordinary sense of the word, and would, under ordinary circumstances, be reckoned as little more than surface soil, which in fact they are; but their peculiarity is that they con­ tain flints, although there are no flints in the subsoil, since the hill is in the" Chalk without flints." The explanation, however, is very simple. This hill was formerly higher than now; so much higher that the top of it reached the level of the flinty Chalk. Since then the Chalk has been dissolved away, leaving the flints and other insoluble parts to sink down vertically, while always remaining at the top of the hill. From this spot there was also an excellent view of the" feature" that is made here, as often else­ where, by the chert band, in the long crest which runs out north­ wards and forms St. Catherine's Down. After inspecting the little belfry on the top of the hill, which is built of the local freestone, and seems to have stood very well, the party descended to examine the place where coprolites were for­ merly worked on the edge of Gore Cliff. The excavation is imme­ diately above the Chert Beds, and thus occupies the interval between the two quarries previously examined. It exposes a soft marly earth, quite dark, with green glauconitic grains, and here and there phosphatic nodules, and is a veritable happy hunting ground for fossils. Ammonites varians and Turrilites scheuch­ zertanus were picked up at will. A little further along the cliff, at a slightly higher horizon, was found another fossiliferous band, of a more chalky nature, in which larger specimens of Ammonites varians were almost equally abundant, while one of the members secured a specimen of the much rarer Ammonites falcatus. A little beyond this the party descended by a path running obliquely down the cliff face, and traced along the sides the Freestone and other beds, which here go to make the "Upper Greensand." On reaching the road they were conducted by Mr. Livesay, of Ventnor, into the grounds of South Cliff, the property of Dr. Paul, to inspect the junction of the Upper Green­ sand with the underlying Gault, which is here well exposed in an artificial section. This was the only opportunity of examining the latter formation, which is generally obscured by the slips, or is other­ wise inaccessible. Itwas not found to be fossiliferous, as it seldom is so in the Isle of Wight; otherwise it was of similar character to that of other localities. Some of the members of the party were afterwards hospitably entertained by the same gentleman at Spring 17° EXCURSION TO THE ISLE OF WIGHT. Cottage, in the grounds of which is the once celebrated Chalybeate Spring. This they had no time to visit, but Mr. Livesay was good enough to send some of the water to the hotel for members to taste. It seems a pity that so excellent and powerful a Chaly­ beate water should be allowed to run to waste; but there is a fashion in waters as in everything else. The party returned to the Blackgang Hotel to dine and sleep.

Tuesday, March 3ISI.-The last day of the Excursion was a comparatively easy one. Making a good start at half-past eight, members drove along the delightfulU ndercliff, the warmth of which contrasted strongly with the cutting wind experienced on St. Catherine's Hill the day before, and whose trees were just budding forth with the promise of Spring. Ventnor reached, they alighted at the Museum, where they were met by the Curator, Mr. Norman, whose careful collecting of the fossils of the district in days gone by, had enriched many a public and private cabinet. Good exam­ ples of the products of the neighbourhood are exposed in the wall cases of the Museum; and these were carefully inspected by members. The Director here took the opportunity of thanking Mr. Livesay for the attention he had paid the party during their pleasant visit, and Mr. Norman for attending to conduct them round the Museum. Leaving the Museum, the members walked over the wild and broken ground which forms the" Landslip " of Bonchurch; and here the Director gave utterance to a prophecy concerning the future fate of the Undercliff. This Undercliff, as every geologist knows, is caused by the Chalk and Greensand having a slight dip towards the sea, and by their resting on the soft and unctuous Gault, which rejoices in the appropriate name of the "Blue Slipper." But the great masses of hard rock which have thus fallen, have for the most part descended to the sea, and form a natural protection to the land that lies behind. The two ends, however, by curving round to the north, bring the Gault to a higher level; and at the other end it may be seen on the sea­ shore. Slipping here is, therefore, still possible; accordingly we find comparatively recent landslips on both sides. It is therefore probable that the ultimate destruction of the Undercliff will be brought about by losses from the east and west, till it is reduced to its central portion. The path led the party at last to Luccombe Chine, where they descended, and, had the tide permitted, would have gone along the shore to Shanklin. At Horse Ledge, however, the water was up to the cliff; so the members had to content them­ selves with the ground between this and the Chine. Fortunately it is the most interesting part, for here one passes, at close quarters, over the Carstone and the Sandrock, which form the bulk of the cliff, and whose dark masses are there well exposed. On the EXCURSION TO THE ISLE OF WIGHT. shore are ledges of the upper part of the Ferruginous Sands, which are here as fossiliferous as they are barren at Blackgang. The specimens of Exogvra are immense, probably the largest oysters that are to be found anywhere in any English rocks. Yellow and Horse Ledges yielded to members many of the characteristic nodules ;. some of these are masses of Rhynchonella gibbsiana, the shells of which are well preserved in a green sandy matrix; others consist of Thetis minor, and other bivalve shells, which occur as hollow casts in a compact dark-brown ferruginous stone. Having collected enough of these fossils from the loose blocks on the shore, the members who had ventured so far had to return to Luc­ combe Chine. On the way, the Director took occasion to point out the influence which the jointing of the rocks has on the form of cliffs. This piece of cliff has a step-like boundary. First, there is a long stretch of bare rock parallel to the shore-line, then a short piece at right angles to it, and then another long stretch, and so on. Now the long pieces coincide in direction with the dip of the stratum, and consequently run along the" Master-joints," while the others at right angles are along the secondary joints. He also called to the mind of the members the three sections they had seen in the Neocomian rocks, of which that'at Compton Chine was the thinnest, that at Blackgang the thickest, and this intermediate between the two, thus showing the direction in which the rocks thinned out. Here the geology came to an end, and there remained but the necessary parting meal, and the reluctant departure by the train for Shanklin.

REFERENCES. Geological Survey Map, Sheet 10. 1816. ENGLEFIELD, SIR H. C.-" Description of the Principal Picturesque Beauties, Antiquities, and Geological Phenomena of the Isle of Wi g-ht." London. (The geology by T. Webster.) 1853. FORBES, E.-" On the Fluvio-marine Tertiaries of the Isle of Wight," Quart. :!ourn. Geo!. Soc., vol. ix., P: 259. 1856. FORBES, E.-" The Tertiary Fluvio-marine Formation of the Isle of Wight," Geo!. Survey Mem. 1862. BRISTOW, H. W.-" Geology of the Isle of Wight," Geol. Survey Mem. 1880. ]UDD,]. W.-" 0" the Oligocene Strata of the Hampshire Basin," Quart. :!ourn Geo], Soc., vol. xxxvi., p. 137; with Plate vii. 1887.-KEEPING, H., and TAWNEY, E. B.-" On the Beds of Headon Hill and Colwell Bay in the Isle of Wight," Quart. Jou,-n. Geo!. Soc., vol, xxxvii., p. 85, with Plate v. 1886. REID, C.-" The Pliocene Deposits of North-west Europe," Nature, vol. xxiv., p. 341. 1888. GARDNER,]. S., KEEPING, H., and MONCKTON, H. W.-" The Upper Eocene, comprising the Barton and Upper Bagshot Formations," Quart. :!ourn. Geo!. Soc., vol. xliv., p. 578. 1889. REID, C. and STRAHAN, A.-" Geology of the Isle of Wight," by H. W. Bristow, Second Edition, Geo!. Survey il1em. 172 EXCURSION TO NORTHAMPTONSHIRE.

STRAHAN, A., and RETD, C.-" La Geologie de I'Ile de 'Wight," COllg. Giol. hlterllat., Compte Rendtt, 4me Session, Londres, 1888, p. 347; with Map. 1891. GARDNER, J. S.-" Report on the Eocene, Oligocene, and Miocene," COllg. Ceo! .1nterllat., Compte Rendtt, 4me SeSS1(m, Londres, 1888, Appendix B, p. 39.

EXCURSION TO NORTHAMPTONSHIRE.

SATURDAY, MAY 16TH TO TUESDAY, MAY 19TH, 1891.

Directors: BEEBY THOMPSON, F.G.S., F.CS., AND \VALTER D. CRICK.

(Report by the DIRECTORS.) The official Excursion comprised only the two days, Monday and Tuesday, in Whitsun week, i.e., May rSth and r oth, but a preliminary Excursion was arranged for the Saturday previous. The programme of the Excursion contained a section, showing the sequence of the various beds in the particular area to be visited by the Members, which is here reproduced.

DETAILED DESCRIPTION OF THE BEDS.

CORNBRASH.

I. Rubbly ferruginous and fossiliferous limestone, with some large blocks, containing Terebratula obovata, Pecten vagans, Avicula echinata, Anabacia orbulites, &c.

FOREST MARBLE SERIES.

2 and 4. Variegated clays, greenish looking at a distance, containing much drift-wood and carbonaceous matter. 3 and 5· Fissile shelly limestones and hard shales, with many fossils, chiefly Ostrea, also much drift-wood; some surfaces of the stone being nearly covered with plant-remains.

GREAT OOLITE CLAY. 6. Blue and purple clay, containing much wood and carbon­ aceous matter, some of the larger pieces of wood bored by some boring mollusc. Ostrea subrugulosa is abundant in this bed at some places, but not in the area visited.

TRANSITION BED? 7. Ferruginous bed containing concretionary ironstone nodules, also much selenite in curious interlacing layers.