39

EXCURSION TO JOYDEN'S WOOD AND DARTFORDHEATH.

SATURDAY, SEPTE~IP,ER 22ND, 191].

REPORT BY ARTHUR L. LEACH, F.G.S., Director oj tileExcursion,

NEARLY 30 members assembled at Bexley station at 2.30 p.m.At the entrance to Joyden's Wood the Director drew attentionto features developed on the outlier of Lower Tertiary strata overwhich this woodland extends. The outlier supplies an interestingcontrast with that at Well Hill, where similar beds, at about 500

to 600 ft. O.D. occur on the summit of the ridge between therivers Darent and Cray. In Joyden's Wood, Eocene beds spreadover a large area, but their elevation is low, and the groundexhibits none of those steep slopes and funnel-like swallow-holeswhich compose much of the interest of the Well Hill surfacefeatures.

At Cavey Spring, on.the margin of the wood, attention wasdirected to some of the numerous depressions which indicate thepositions of deneholes, and with the aid of a diagram, thedimensions and usual arrangement of the chambers and shaft ina denehole were explained. The whole woodland containsabout 120 deneholes, some, as at Cavey Spring and Stankey'sWood, associated in large groups, others scattered here andthere about the wood. Many have partially collapsed, theirsites being marked by pits, but a large number are still open andaccessible by means of ropes, the chambers, except for hugemounds of debris accumulated beneath the shafts, remainingquite as they were when work finally ceased in these puzzlingexcavations.

Passing reference was made to the numerous suggestionsbrought forward to account for the origin of deneholes, and tothe work done by the Essex Field Club 30 years ago, in thegroup at Hangman's Wood, near Grays, in Essex. The contro­versy upon their age and purpose, revived vigorously about 10

years ago, has again subsided and the problems for most peopleare narrowed down to these questions :-Were deneholes merelyexcavations to obtain chalk for economic purposes, viz., manure,and brick and pottery making; were they primarily slink toobtain chalk and afterwards used as storehouses for grain, fodder,straw, etc.; or were they originally intended to be granaries andstorehouses. the value and lise of the chalk being secondaryconsiderations?

To each view objections can be raised, and the adoption of

.j.0 ARTHUR L. LEACH,

anyone certainly leaves some difficult questions unanswered, butthe simple chalk-hole explanation seems most feasible, and inthe opinion of the writer, no proof has been brought forward oftheir use as granaries, storehouses or underground refuges. Thesituation of several of the pits in Cavey Spring seems directlyopposed to their use for storing any kind of vegetable foods ormaterials, for they are sunk in the floor of a small valley downwhich water flows after heavy rains, and one streamlet actuallyruns into a denehole and has almost choked it with a down­wash of sand and mud. The Director made this rathercurious discovery here some years ago. He had gonedown into a denehole in the valley floor, and on reachingthe bottom of the shaft, landed on a smooth floor of hard mudwhich filled up all the chambers to within a few feet of the roof.On seeking an explanation of this very unusual, in fact, unprece­dented state of things, a hole was found running from the shaftthrough the base of the Thanet Sand at its junction with theChalk. The passage was just large enough to permit him tocrawl along it for some yards, sufficiently far to enable him to seethat it opened in the side of the shaft of another denehole. Whathad happened seemed clear. The upper denehole had becomegradually filled with silt swept in by temporary streams duringheavy rains. This silt had made the floor watertight and held upwater which at some time reached above the roof of the chambersand up to the top of the Chalk. Drainage had then commencedthrough a crevice or joint in the Thanet Sand, and the channelhad been widened by successive flows until it became a smalltunnel through which, whenever the upper denehole becamefilled, the excess water escaped, carrying with it sand and silt whichin process of time had almost filled the lower excavation. Dene­holes in such situations could hardly have served as storeplaces,for, even if the stream were prevented from flowing into the uppershaft, the situation of the chambers below the valley floor musthave been always damp, especially in winter when presumablystoreplaces would be most needed.

Following the path through the woodland other depressionswere noted on the sites of collapsed or choked up deneholes. Astream channel (dry) leads directly into one large pit, abovea collapsed denehole chamber, where the shaft could be seen to adepth of about 20 ft. below the ground level. The way now ledthrough a rectangular earthwork enclosed by a single fosse andvalium. The path runs almost diagonally through the camp areawhich is thickly overgrown. The site has not been explored, butpottery of Romano-British types is said by Spurrell to have beenfound. A plan given in the" Victoria History of Kent" shows a"British Road" running along the eastern side of the camp.This feature-is undoubtedly an ancient disused road, leadingprobably from the neighbourhood of Crayford and Dartford

EXCURSION TO lOYDEN'S WOOD AND DARTFORD HEATH. 41

towards Ruxley and the Cray Valley. Where it passes the campthe hollow way has been modified. The centre of the track hasbeen deepened, and the excavated earth thrown up in a bankon each side. According to Colonel Ruck's opinion, quoted inthe" Victoria History of Kent," this was done by the Romanengineers to strengthen the defences of the camp. The twobanks and the three ditches certainly exist outside the mainvallum of the camp. Whatever explanation may hold good, thearrangement of these structures seems too regular to have arisenexcept by deliberate design. A shaft, about 102 ft. deep, examinedwithin the camp area, is not a denehole but probably an ancientwell, possibly connected with the original occupation of the camp.A party descended the shaft in 1883, but apparently did notexamine the debris at the bottom, and until this is done the ageof the excavation must remain in doubt. A lining or "steining"of large flints surrounds the upper part of the shaft. Many of thestones are loose and great risk would attend a descent of theshaft in its present condition.

From the eastern margin of the wood a good view opened outof the outlier at Puddledock. Although small in extent it issteep sided and well wooded, and forms quite a prominent surfacefeature. The party walked thence along the Birchwood Road toDartford Heath to examine the High Terrace gravel in pits nearBowman's Lodge and above Wansunt. Some time was also spentin an examination of the implementiferous channel described byMr. R. H. Chandler and the Director (see References). Theseexcavations have often been visited, and nothing fresh was seenon this occasion. Former papers and reports contain full detailsof the position and constituents of the gravel. The partyreturned to Bexley for tea by the path through the fields and leftby the 6,34 train.

REFERENCES.

Geological Survey Map, London District (Drift), NO.4.1907. CHANDLER, R. H., and LEACH, A. L._H Excursion to Crayford

and Dartlord Heath." Proc, Geol. Assoc., vol xx, p. 122.1907. NEWTON, E. T._u Note on specimens of Rhaxella Chert or

Arngrove Stone [rom Dartford Heath." Proc, Geol, Assoc.,vol. xx, p. 127.

1912. CHANDLER, R. H., and LEACH, A. L._H On the Dartford HeathGravel, and on a Paleeolithic Implement Factory." Proc. Geoi.Assoc., vol, xxiii, P: 102.

1913. LEACH, A. L._HOn Buried Channels in the Danford HeathGravel." Proc, e~ol. Assoc., vol. xxiv. p. 337.

1914. DEWEY, H., and SMITH, R. A.-" The High Terrace of the Thames:Report on Excavations made on behalf of the British Museum andH.M. Geological Survey in 1913." Archaotogia, vol. lxv, p. 187.

PROC. GEOL. Assoc., VOL. XXIX, PA'RT I, 19I1l.]