P. G. H. DOSWELL, EXCURSION TO IlENTLEY, SUrFOI.". 327

Thereafter we walked to Cadgwith, where a detailed exarnin­ arion was made of the interesting section on the east-side of the Devil's Frying-pan; its special feature is the intrusion of Kennack gneisses into hornblende-schist, and the presence of a small tongue of dunite-serpentine in the complex thus formed. After tea in Cadgwith we walked to Ruan Minor and took the opportunity of examining some sections of the weathered Ruan gneiss on which stands the village of S1. Ruan,

REPORT OF AN EXCURSION TO BENTLEY, . SATUIWAY, APRIL 5TH, 1913. Bv P. G. H. BOSWELL, B.Sc., F.G.S., Director of lite Excursion,

THE official party of the Association, travelling from Liverpool Street Station (G.E.R.), were met at 1.50 p.m, at Bentley by local members of the Association and members of the and District Field Club, who had bern invited to attend the excursion. The whole party of fifty then proceeded eastward along the main road, halting for a few minutes in the Crag Pit at Danes Barn, south of the road, about 300 yards east of the station. Geological maps of the district on the scale of 3 inches to the mile (reduced from the Director's Geological Survey on the scale of 6 inches to the mile) were distributed, and the sequence of the beds in the immediate neighbourhood commented on. The London Clay was the lowest bed reached in the valleys, and this was succeeded by Red Crag ~ with an intervening bank of Coralline Crag at one place only-Tattingstone Hall), Glacial Sand, Gravel, Loam, and Chalky (non-Kirnmeridgic) Boulder Clay. River loam and alluvium also occurred. In the pit (Danes Barn) some 30 ft. or more of unfossiliferous ferruginous sands were visible, these being the upper, decalcified portion of the Red Crag, which used to be seen in its ordinary shelly condition at the base of the section, now covered with talus. Members then proceeded to the small pit in the field on the opposite (north) side of the road. Here the complementary phenomenon to decalcification was pointed out. Percolating water, charged with carbonic acid gas derived in part from the atmosphere, but perhaps largely from the soil (which also pro­ vides organic acids), dissolves out the shells from the Crag (those made of aragonite disappearing long before the less abundant calcite forms, such as Peaen, Anomia, Sea/aria, Tere­ braluta, etc.), leaving decalcified sands. If, for any reason, the P. G. H. n05WEJ.r., water is compelled to redeposit this dissolved chalk, it frequently does so in the interstices of decalcified or shelIy Crag lower down the slopes, and a hard white wall of t'lldura/ed Crag, such as was seen on the south side of this pit, is the result. As the pit had yielded a rather good fauna (over 130 species of Mollusca, Polyzoa, Corals, etc., which, considering the paucity of species hereabouts, was distinctly satisfactory) in 1906-7, when many tons of the Crag here were sifted to determine its affinities, a few minutes were alIowed for collecting. The party then moved on along the main road eastwards through Tattingstone Park to Tattingstone HaII Farm. Here an isolated massof Coralline Crag (the only one south of the Deben estuary) is cut into in the stackyard pit. Before reaching the pit, however, "scratches" of the bed were pointed out near the house. The accompanying sketch-map, taken from the writer's large scale survey, indicates the areal extent of this bank (or so-called "reef") of Lower Crag. It is clear that the out-crop is not so large as the Geological Surveyors indicated on the old one-inch map, the area according to them being rather over double that on the more modern map. However, the small scale and inaccurate topogra­ phical maps may be largely responsible for this. In this pit the Director gave a brief account of modern views and work on the Pliocene deposits of East Anglia and the Continent. It was mentioned that the Coralline Crag seen in the form of a bank in the pit was not typical, being here very comminuted and yielding few good fossils. Charlesworth and Lyell had visited and described the section in r835 and 1839 respectively, and Prestwich had figured it in r870. Lyell made a 7 feet deep excavation, but was then stopped by water. At the bottom he found a NllCltla and Vorus ova/a. By an interesting coincidence, one of the few whole fossils obtained from the Coralline Crag on the excursion was a perfect little Venus ova/a Pen. Mr. F. \Y. Harmer's zoning of the Red Crag deposits was referred to·, the beds characterised by extinct and southern shells (Wallonian Zone) occurring south of the Stour estuary, an intermediate division with more recent and boreal forms (New­ bournian Zone) occurring between the Orwelland Deben estuaries, and the most recent Red Crag deposits (Butleyan Zone) occurring north of the Deben estuary. The fact that these are lateral zones was emphasized, i.e., the Newbournian is never found lying on the Waltonian, nor the Butleyan 011 the Newbournian, the lateral change being a result of the tectonic wave-like movements of the land in Pliocene times, resulting in a gradual upheaval to the south and subsidence to the north. The area into which the Association were making their excursion, viz., that between the Orwell and Stour estuaries, has not yet been fullyinvestigated, • Harmer. 1900and l}09-see references. EXCURSION TO BENTLEY, SUn·OI.K.

but some amount of work carried out in 19°6-19°8- (sifting being adopted to obtain as complete a fauna list as possible) appeared to indicate that the affinities of, at any rate, the southern part of this area (Bentley, etc.) were rather with the Waltonian Zone.t At the same time, preliminary work farther north in the district (Tattingstone, , etc.) seems to show that the deposits have rather affinities with the Newbournian Crag. In

Stole : 8:,0'=='*====1' furlong . r.-;--:-, -_.- Contour lines, L....:-..:....: ---- Footpath s. Glacial Red Coralline London Sand and Crag Crag Clay Gravel, (k'). (k'). (I').

FIG. 26.-GEOLOGICAL SKETCH-~IAP SHOWING THE CORAJ.1.I:"E CRAG, ETC.,.AT TATTINGSTONE, SUFFO/.K, ON A SCALE OF 6 I:-:CIlIiS TO I ~III.E.­ P. G. H. Boswell.

short, the area under consideration was a transitional one between the two zones, without a sufficiently distinctive fauna of its own to justify making a separate division of the already much-divided Red Crag to contain it. The characteristics of the Crag of the Bentley district were (I) its transitional fauna, with affinities

• Roswell, 1906 and I<)OS. t The late S. V. Woou always held Ihi,;opinion. 330 P. G. H. COSWELL, EXCURSION TO BENTLEY, SUFFOLK,

rather to the older Red Crag" (2) its comparative poverty in respect of the number of species to be found, univalves, more especially the smaller forms, being decidedly uncommon. This is to be contrasted with the Oakley Crag (Waltonian Zone) where Mr. Harmer has obtained over 700 species and varieties. (3) Its broken character and the comparatively large number of pebbles and boulders included in it. There is much evidence of con­ siderable water-rolling, and the deposit appears to have been rapidly accumulated. Many of the Waltonian species are much water-worn, and the whole character of the deposit suggests that it may have been formed in part from the wreck, by contempora­ neous erosion, of Waltonian deposits already being elevated to the south. Among the most abundant species met with were the following, all being especially characteristic of the Waltonian Zone: Cardium parkrilsolli J. Sow., Dosinia exolela Linn" lIfadra araaita J. Sow., Num/a kevigata J. Sow., Nassa gram/lata j. Sow" N. propi1lfJlIfl ]. Sow., N. /abiosa J. Sow., Neptunea contraria Linn ., TrochliS adansani Payr., T. sube'xcavatus S. Wood, Purpura lapillus Linn. var. oaldeyensis Harmer, and Woodia digilaria Linn. Others, with a wider range in the Crag, collected on the excursion, were: Cardita Sell/tis Lam., C. scaiaris Leathes, Corbu/a groba Olivi, Astarte cOlllpressa Mont., A. oma/ii Laj., A. oblitjua/a J. Sow., Pecrunadus g(}'C/illeris Linn .; and var, slibobliqllllS, P. pil(JsusLinn., Ostrea and Pecten, Na/ica mui/pullclata S. Wood) N. hemic/ausa J. Sow., Capll/lls 1l1lgaricus Linn., Emargimda fissura Linn ., and many others, together with corals, polyzoa, teeth of shark, and ray, etc. The sinistral Nepltmea contraria is very common in the district, but the dextral N. antiqua is very much rarer. After the Director's remarks, members proceeded to examine the beds and collect fossils, a ladder, picks and shovels being called into service. The section as Prestwich figured it (see references) was compared with that figured by the Director in 1907 and with that now showing. It is evident that the pit is decreasing in height as the Crag is being cut away for agricultural purposes, and much of the reef is disappearing for the same reason. It is of little use giving the details of the Red Crag section, as these change continually as the section alters, current -or shore-bedding being the prevailing characteristic. The small patches of flint gravel at the top mar be Glacial or may be of Crag age. Members then walked up the meadows by the stream to the Crag-pit on the south side of the hilI near Tattingstone White • Out of 67 species quoted b}·l\lr. Harmer as most characterist,;c of Waltonian eraI:'. only S2 ha ve not yet been found in the area, and of ,8 northern spe cies rare at W:llton only shave been found at Dentle)'. See Har mer (1900) , P' 712, C. N. I:ROMEHEAD, EXCURSION TO CHERTSEY. 33f

Horse Inn. A short time was spent in collecting here, and then the party moved on to Bentley Park, where Mrs. Hugh Turner and Miss Turner most hospitably entertained the members to tea, in the midst of exceedingly delightful and quaint surround­ ings. The thanks of the members to the kind hostesses, and also to the Director, were excellently voiced by Mr. G. "'. Young. One other Crag-pit, north-west of Rookery Farm, was visited after tea, on the way to the railway station, where the members returned to London by a fast train specially stopped at Bentley for the Association at 8.10 p.m ., by the courtesy of the Great Eastern Railway Company. I\'1r. 1. S. Double acted as Excursion Secretary on this occasion. REFERENCES. Geological Survey Map, I in., Old Series, Sheets 48 N.W., 48 N.R. Geological Survey Index Mar,i in., New Series, Sheet 16 (Drift). 1871. PRESTWICH, SIR JOSEI'H.-u Crag Beds of Suffolk and Norfolk," Part II. Quart. YOUrI/. Geo!.Sec., vol. xxvii, p. 325. 1885. WHITAKER. W .• etc.-_u Geology of the country around Ipswich:' Mem. GIO!.Suru. 18go. REID, C._u Pliocene Deposits of Britain." Mon. Geol Suru. 19oO. HARMEk, F. '''''.-" The Crag of Essex, etc." Qlla,·t. ]01l1'1l. Geol Soc••vol. lvi, p. 705. 1906. RIDLEY, E. P., a nd BOS\I"ELL, P. G. H._" Excursion to Bentley. Suffolk," Proc. Geo!. Assoe., vol. xix, p. 459. 1908. BOSWELL. P. G. H.-" Bentley Excursion." YOllrn. Ipswich F it/a C!1I6, vol. i, p. 13. Jgog. HAH)fER, F. W.-" Pliocene Depos its of the Eastern Counties," Geo/~l.v in the Field, p. 86.

REPORT OF AN EXCURSION TO VIRGINIA WATER AND CHERTSEY.

SATURDAY, APR1L 12TH, 19J3. Bv C. N. BRO:\[EHEAD, B.A., F.G.S., Director ofthe Excursion. THI':: main object of this Excursion was to study the physiography of a small part of the Thames Valley, and in particular a case of stream-diversion ; at the same time something was seen of the general geology of the district. The party started from Waterloo by the 1.10 p.m, train, reaching Virginia Water at [.59 j several members joined at intermediate points and others were already at the station, bringing the total number to 30. The first point to be visited was a pit near Stroude, about a mile north of Virginia Water Station. This was reached by shady paths through Great Wood. The pit has been opened to obtain gravel and sand from the