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.