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On the geology and physical features of the Bagshot district
429
ON THE GEOLOGY AND PHYSICAL FEATURES OF TIlE BAGSIIOT DI STRICT.
By PROFESSOR T. RUPERT JONES, F.R.S., President of th e Geologists' A ssociation, &c. (R ead May 7t h, 1880.) CONTEN TS.
§ 1. Are a of th e Dis trict described. § 2. F eatures of the Bagshot District. § 3. Fauna and Fl ora. § 4. Na tural Drainage and Water.supply. § 5. Geological Structure of th o District: the Bagshot Sands,-oZ, Upper; b, Middle; 0, Lower Bagshot Sands; d, Sarsden Stones. § 6. Geological History of th o District: 1. 'I'he Bagshot Sands an d the underlying Strata thrown into undulations.-2. The Denudation of the Arches or An ticlin es.-3. The High-level (or Pl ateau) Gravel.-4. Th e L ow-lev el Grav els (or High.level Valley-gravels); the partial Dest ruc tion of th e higher Gravels; Sarsdeus in both sets of Gravels; Local pa tch es; Va lley-bot toms, § 7. Antiquities.
§ 1. .dl'ea.-The sands and clays of the group of Tertiary strata kn own as the "Bagshot- Sands" occupy in th e Bagshot district an ar ea of about 300 square miles, extending about 24 miles from E sher on th e east to Willchfield on th e west , and 12 miles from A scot on the north to Al dershot on the south ; and th ey reach an altitude of about 400 feet above the sea-level. In ot her words, th is division of the Lower Tertiari es is well developed in t hose parts of Hampshire, Berkshire, Surrey, and Middl esex that lie between the Chalk ranges of the H og' s-back and th e Surrey Hill s on one side, and th e line of the Thames on th e oth er, with th e Chalk ranges of Berks and Buckingham shire parall el to it. Th e hill-ranges of Easthampstead Plain, the Chobham Ridge s, Finchampstead Ridges, and th e Fox Hills, separated by th e Blackwater from the Hartford-b ridg e Flats, which extend west. ward in the direction of Odiham and Basingstoke, are all composed of the "Bagshot Sands." Th ese strata lie on "London Clay," II Bag shot, a hamlet of Windl esha m, was brought to notice as a post ing station on the main r oad fr om L oudon to Salisbury and th e West.
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T.
RUPEH T JON ES
ON Til E G EO LOG Y AN D
r esting on Ie W oolwich and R eading Beds," below which is Chalk , in a broad shallow" syncline." Gra vel coat s th e tops of the hills, fringes th e hillsides here and th ere, and covers th e valley-bottoms at various levels. § 2. Features.-This country of the Bagshot Sand s mainly consists of flat-topp ed hill-r anges or small plateaux, formed of sandy stra ta, with g ra velly tops. Al ong th eir edges they are cut int o frequent g ullies and spurs, sloping downward quickly into valleys. These are na rrow at th eir upper sources, where they leav e the bill-l and, and broad and shallow below, where the y reach th e river-lines. Thu s they open int o the wide vall eys of th e \Vey, Blackwat er, and Loddon, to which th ey bring tribu tary streamlets j and all merge int o the g reate r valley of th e Thames. The district is not rich with fossils, nor free to expose many geological charms in quarries or other sections j but its physiography is very intoresting.e Lo okin g around from the floors of many of the valleys, we can r eadily discern th e main feature of th e area, characteristically mark ed by th e long line of level crest all around, standing out against th e sky. E ven where the hilltops (as frequently occurs) are crowned with pine-woods (the only tre es finding congenial soil for full development), th e same general level of the terrain is apparent ; and, indeed, th e evident general levelness of th e upper line of th e country cannot fail to be st riking to th e intelligent observer. The flat hill-top s keep their long l evel edge-lines, because of th e hard er gravel and seams of sand, closely cemented by iron-rust, which pr otect th e weaker materials below. The more promin ent spurs and other marked features of th e landscape, with th eir regul ar slopes and elegant outlines, lire dne to th e existe nce of this " pan," which lies from 3 to 12 feet below the platform. The formation of thi s irony layer was caused by water lodgin g here and th ere on the once-continuous gravel plain (since cut into separate hills and ridges). and carrying the iron-oxide downwards by percolation to the first imper vious layer, which is often th e und erlying sand itself "puddled," or made water-tight, by the ferru gin ous cement filling its pores and interstices. Similar " pan " or "rust " also underli es th e gravelly sur face in the vall eys at many places.
* See als o Proceed . Geol. Assoc., Vol.
vi. p. 329, &c.
PHYSICAL FEATURES OF
THE BAGSHOT DISTRICT.
431
Along the borders of the main hill-ranges, or more strongly marked table-lands, there are many outlying hills and "uuderfeatures," consisting of' similar sandy materials. Those on the outside of the area are based on the London Clay. Those within the area consist of Upper, or of Middle Bagshot Sands, as the case may be. Some of these "outliers" reach the level of the plateau-gravel, and retain a capping of it, hardened and preserved by the irony "pan." Others, at a lower level, have bare sand tops; others bear valley-gravel at different levels, according to position. § 3. Flora and Fa1lna.- Vegetation is not luxuriant, as far as diversity of plants is concerned. The up-land bears Firtrees, Furze (Gorse or Whin), Heath, and Whortleberry as its chief plants." The low-land, lying nearer the clay, and therefore more silty or loamy, and better supplied with water, contains a more varied flora. In these hollows much of the land is boggy. Thus the long Marsh-grasses, the Bog-moss, the Bog-myrtle, Cross-leaved Heath, Cotton-grass, Kingspear, Sun-dew, and Alder find congenial sites, with smaller and less noticeable vegetation, in these parts. Still lower down, in wider valleys and in stiffer soil, the Oak and Elm attain their normal proportions. SOME COMMON HEATH Ulex europeeus, Common Furze ... Ulex nanus, Dwarf Furze Genista anglica, Petty Whin
..."'15
PLANTS.
i
Sarothamnus scoparius, Common Broom Erica tetralix, Four-leaved Heath Erica cinerea, Ashy Heath Calluna vulgaris, Scotch Heather Myrica gale, Bog-myrtle
{ {
Chiefly on the lines of roads or paths, but sometimes On the tops of hills. Road-sides. Abundant (in dampish places). More abundant (on the Heaths). Most abundant (do.) Swampy parts of Heaths, along the edges of streams or ponds.
Drosera rotundifolia, Round-leaved Sundew Drosera longifolia, Long-leaved Sundew
Wet Bogs.
Pedioularis sylvatica, Common Lousewort Polygala vulgaris, Milkwort
Damp parts of Heaths.
* See
Kingsley's" Miscellanies" (My Winter Garden), Vol. ii, p. 110, &c.
432
T. RUPEHT JONES ON THE GEOLOGY AND
f
Habenaria alba. Butterfly-orchis
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Marshy ground round Hawley Pond.
Juncus bufonius, Toad.rush Juncus squarrosua, Heath-rush Carex dis tans, Distant Carex
}
Damp Heaths.
Mollinea ceerulea, Purple Mollinea
{
Agrostis setacea, Bents ... Nardus striota, Mat.grass
::: }
{
Everywhere in the low gronnds. By the sides of all heath paths or tracks, especially in marshy parts.
Sphagnum, Lycopodium, and Equisetum are found in the Bogs and Ponds. [A. H.
CLAYPOLE.]
Many birds inhabit the district. In a short walk through some plantations (chiefly fir) in one of the valleys, the late S. P. Woodward recognized the notes of more than a dozen kinds in an afternoon of June. The magpie, jay, and woodpecker are still not uncommon, in spite of the destructive gamekeeper. A pair of hawks aloe sometimes seen. Sq uirrels and hedgehogs, grasssnakes, vipers, slow-worms, and lizards are common, the Coronella snake seems to be rare, but perhaps is frequently killed in mistake for the others; frogs and toads are common, and young toads swarm over the paths and roads of the woods and heaths near water in the spring. The fauna and flora of this part of the country is carefully tabulated in the- Annual Reports of the Wellington College Natural Science Society. § 4.. Water-supply and Dlainage.-The streams, which have their channels in the larger valleys, are fed by the streamlets formed by water leaking from the gravelly tops and sandy sides of the hills. Such upland lines of drainage are marked in summer by long verdant stretches of luxuriant marsh-grasses, the apex of the outdrawn bright-green triangle pointing up to the spring or leakage in the gravel above, on the edge of the plateau, and the base widening out over the narrow marshy valley at the hill's foot. In winter, the grassy verdure is replaced by light-brown, dry, coarse hay; to be again renewed in spring and summer. The rainfall is about 23 inches a year; and the water is largely stored in the gravels and sand-beds for the permanent springs ; and the peaty patches of the higher valleys help in the storage of water to supply the amount carried down by the rivers.
PHYS ICAL FEATURES OF TilE BAGS HOT DISTRI CT.
433
Thu s the wat er-sup ply and, the refore, th e river-drainage wholly depend on rainfall, rul ed by the geological st ructure of th e area. W ells are supplied with water at differ ent levels. There are shallow wells in the gravels. Others, sunk to Middle-Bagsho t beds, which are clayish, have a much better supply, especially when near the lakes which lie at that level. A deeper sinking pierces the lower sands, full of water, on th e L ondon Clay. Only B few borings are driven through this thi ck clay to th e still better water-bearing W oolwich Sa;lds and the Chalk beneath .· § 5. Geological S trllctUl·e.- T his st ructure may be briefly defined as plateaux, hills, and valleys cut out of flat layers of- I , Gr avel (glacial); 2, Bagshot Sand, Clay, and Sand (Eocene); resting on, 3, London Clays; on 4, Woolwich Sands and Clays; and on 5, Chalk. On the valley-sides, moreover, are benches and terrac es of highlevel and low-level valley-gravels. The following is a general section of the strata] : 1.
2.
3. 4, 5.
Gravel, wi th loam 12 feet. ( Upp er Bagsh ot Sands, with Sarsden St ones in place, and some t hin seams of irony loam , occasiona lly fossiliferous, with Turritell a, Na tioa, Cardium , i Ostrea, Nnmmul ites, &C. ... i50 feet. Middle Bagshot Sands, with argillaceous.I and ligniti fer ous beds, some pyrites and fossils, Cardita. pla nicosta, &c, 50 feet. l Lower Bagshot Sands 100 feet. L ondon Clay .. . '" 400 feet . Woolwich and Reading Serie s '" 65 feet. Chal k .. . ... 600 feet or more. (Seen out sid e the district, an d reached in it by boring.)
Below all these lie th e Gault, about 100 feet thick, and the L ower Greensand (or Neocomian Sand), about 800 feet, &c• • Sn ch 8S the deep well at Wokingh am, lately described in the" Geol. :Mag." Ser 2, Vol. vii, p. 421. t F or details, see Prof. Pre stwich' s Memoir in the" Quart, J ourn. Geol. Soo.," VoL iii, p. 378; and Whit ak er and others in the" Memoirs Geol. Su rv ey," Vol. iv, r- 308, &c. ! Some of these are loam y sand s, the sand being mixed with a slight q ua ntit y of clay; and this latter , being somet imes in very small scat tere d lum ps, shows that it was derivative, and that intermediate ero,sioDS had taken place during the deposition of this seri es. H enc e evidence of great lapse of time , and possibly of imp erfect record.
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T . R UPERT J OSES OS
THE GE OLOGY ASP
Though th ere are not any considerable sections exposed in the area under notic e, t he above est imates can be fairly gathered from the neighbouring rail way-cuttings and ot her sections, as well as by the deep wells made, of late years, at Bearwood, Wellington College, W okingbmn, and elsewhere, and by the old wells in th e neigh bourh ood of the villages, as far as th eir evidence g oes. Th e sides of t he valleys tak e t heir chara ct ers from the condit ions of outcrop of th e successive horizontal beds j th e par allel contours being approximat ely equal t o the lines of outcrop. F rom thi s circumstance th e nature of dist ant hill-sides, whether on th e near or the far face of th e hill, can be inferred from the nat ure of anyo ne hill. The heads of many of the valleys are separated, one from anoth er, by 101V "cols"; and th ere are many "under-features," or nearly isolated low outliers, caused by the unequal degradation of th e spurs by weather and rain-action, or held up by high- or lowlevel valley-gravels, according t o the local distribution of th ese materials, forming benches or terra ces. Thus the gravel edges, especially at the crest of th e hill s, are , as a rul e, steep, and g ive out water ; th e sand slopes are much more g entl e, and give SOlUe water, t hough not so much in proportion as the g ravel; and th e clay bottoms, which are nearly flat, or have only a slig ht inclination, ha ve always a wet surface, as th e spring - and rain-wate r set tling on them, wit hout soaki ng in, finds it s way to lower levels. The strata consti tu ti ng t he district are pra ctically flat; but theoretically th ey ar e synclinal, being t urne d up at th eir north and south edges, t og ether with the nnderlying Chalk, Gaul t , and Greensand, as seen in th e chalk-pits and other sections near Guildford, Tongh am, &c. T hus th ey form part of the so-called "London Basin " (really a trough). which, with the anticlinal r idge of Wilts, &c., as a complement , is conterminous with th e syncline of Hants and th e Isle of Wight. a. It cannot be too often pointed out that the Bagshot- Sand series of this neighbourhood is one that teaches the broader lessons of ph, sical geology rather th an stratification or palreont ology. It teaches these physical results in th e modern configurati on of the gro und, and, therefore, it is useful in dir ecting th e observer's eye to alt eration s and changes in other formations, which hav e followed th e same laws. Some of the Up per and Middle Bagshot Sands, however, show
PHYSICA l, FEATURES OF TH E BA GSHOT n rSTRICT.
435
many interesting fossils, mostly of a molluscous nature. F alsebedding, the result of wind and tide action, are in some places well represented. Exc ept in certain beds, fossils are ra re, and, as a ru le, in the state of cast s; for the water, percolatin g easily bet ween t he particles of sand, has been able to get at the sh ell-matter and dissolve and remove it. No modern sand -ban k is rich in animal life, at least as r esidents. Sand -banks are, as a rule, shoals, or lie in sh allow water, where wave-wash and trit uration by sand must be ag reeable to few creat ures unless " to the manner born." Shells are thus easily removed. and broken j and , if broken, more easily d issolved and destroyed than in the quieter waters of greater depths, where the mud and finer particl es have found rest. Casts of Turritella, Natica, Calypt1'(l!a, Cardita, Cardium, Pe ctnncuius, L ucina, &c., are found at several spots :-Neat' " Cresar's Camp," on Easthampstea d P lain j near the Criminal Lun atic Asy lum of Broadmoor ; on the Windsor Rid e nea r the Royal Military College j by Hawley Pond j along the road by Long Cross, near ' Vindlesham ; and elsewhere. I n excavating a well at Wellington Oollege, several fossils of t he above kinds were found, and a seam with Osirea and Nummulites lceoiqatu« was pass ed through . So also at Weking Nummulites were brought up from the well at the Coun ty L unatic Asylu m. These are suffi cient to prove the geolog ical h orizon and age of these strata, The Upper Bag shot Sands contain lit tle or no clay. b. Th c middle set of strata which ap pear at th e bottoms of some of the lower vall eys hereabouts are much more loamy and g reenish. As the oxide of ir on in the common yellow sands of the Bagshot series underg oes a ch emical chang e in the p resence of sta gnant water with decomposing organic mat ter in it, and becomes g reen (drying to a greenish g rey), it is difficult sometimes to discri minate at first sight between real green "Bagsho t" and the greenish loamy and silty sand of some of th e drainage lin es leading towards th e st reams. By the presence of glauconite in the real " Bag shot ," as well as by the position of th e successive beds, the distinction can be made. Some, however, of th e Middle Bagshots, in which there is much vegetable matter, may hav e received t heir green ti nts partly or wholly from t he peculiar oxidation of the iron above refer red to. At Bng shot and Ileal' Saudh urst th e Middle Bag shots are ~
1
436
T. RUPERT JONES ON THE GEOLOGY AND
exposed, and their loamy beds are sometimes used for brickmaking. Close to the railway-station at Wellington College, the railroad is continually wet with the rain-water which percolates the thin sand over these clays, and weeps out on their surface where exposed by the cutting. The Middle Bagshots are best seen in the well-known cutting of Goldworthy Hill, not far from Woking, on the South-Western Railway. c. The Lower Bagshots are visible near W okingham and Virginia Water; also between W oking and Weybridge; at Ash, Aldershot, and elsewhere. They consist of yellow sands, and rest on the London Clay, as can be seen near Weybridge, Aldershot, W okingham, Snnningdale, and elsewhere. Resting on this impervious clay, they form a good reservoir of water; but the water is not everywhere good, for it is often contaminated by the pyrites of the clay giving off sulphurous salts and iron. Near the exposed junction of this sand with the London Clay, it often thins out over the latter, owing to the slope of denudation and the lie of the beds. In this case it is better timbered than where the sands are thick; for the trees have a firmer soil and more water. The clay grounds can be readily distinguished by the vegetation of their surface; for the eye recoguizes at once better herbage, finer crops, and a free growth of oak and elm. The recognition of the presence of hard clay under an out-thinning edge of similar sands in the New Forest, Hampshire, enabled the late Mr. Menzies, when a young man, to account for the stagheading and decay of trees, which had long puzzled older heads than his. d. Sarsden Stones.-In the Upper Bagshot Sands are numerous blocks of fine-grained, compact, white sandstone, lying not far apart one from another, along one horizon (near the surface ofthe Frimley Ridges, for instance) j and, doubtless, once occurring as far as these Upper Sands extended. They are roughly oblong, about 12 feet long, and less; rounded below, flatter, usually, above; with a friable and ferruginous exterior where they meet the sands in which they are imbedded. They are evidently portions of the sands consolidated locally by siliceous cement; but how the silex became dissolved and reset is a very difficult question, not yet solved. These stones, in many instances, have been freed from their sandy matrix, and lie in the derivative gravels, in either a slightly or much worn state. Some have become more ferruginous and friable j some retain
PHYSICAL FEATURES OF THE BA OSHOT DI ST RICT.
43 7
Se veral show traces of the rootlets and th eir internal hardn ess. t h in ste ms origin ally enclose d in th e sa nd ; some (p ossibl y from Occasionally the a little distance) contain flint-fragm ents. weath erin g ha s di ssect ed t he m so far as to show a decided concre t ionar y str uct ure , to which also th eir convexity, or roughly lenticul ar shape, ha s reference. Elsewhere these st ones lie about on th e surface of th e coun try in large quantities, and have been call ed" g rey wether s," since th ey look like sh eep; and by the older nam e of" Sarsdens," supposed by th e late R ev. J. A dams t o be of Sa xon origin, meaning " sail' " (sor e, troublesom e), " stan es , . (s tones), as, ind eed, th ey were t o early sett le rs and cultiva t ors of the soil. The se stones are als o called "Sarsen " or" Sa ssen," equivalent to the Saxon " Sesan," stones (" R. F.," in "Geological Magazine," 1874). The bibliography of these Tertiary concretionary blocks is extensive. Much information about them, with references to writers on th em, will be found in the " Quart. Journ. Geol. Soc.," vol, x, p. 123; vol, xviii, p. 271 ; "Memoirs Geol. Surv.," vol, iv, p. 193 ; G eol. Mag. ," vol. iii, p. 296 ; vol. x, p. 200 j "Geol. Mag.," n. s. , vol. i, p. 96 j vol, ii, p. 588; "Mag . Wilts Arch. N . H. Soc. " ( Codrington) , 18 65; " Transac t. Newbur y F ield Club," vol. i, p. 107; vol, ii, p. 248 ; ., J ourn. Proc. Winch est er Sc . and Lit. Soc.," vol. i, part 4, 187 4. Th ese Sa rsdens are sough t for with an ir on rod on th e Frimley R idges, and when found are exposed by digging, and br oken up in to small square stones for pavin g or building . Th e deserted holes ar e dang erous pitfalls for man and beas t. Large specim en s found in the gravels of railw ay- cu tti ngs are similarly br ok en up , dr ess ed, and used for pitch ing or masonry. Being dense sil iceous sands to ne, 01' q uartzite, th ey are very lasting. § 6. Geological H istory of the District.-W e now turn to the g eol ogi cal h ist ory of t he Bag sh ot Dist rict. 1. The Bagsh ot Sands are th e shall ow-wat er and west ern equ ivalents of the great Nummulitic Formation, which is represented in the east by the th ick Nummulite-limestones, deposited in the open ocean of the peri od. Having been laid down by the E arly Tertiary (Eocene) seas, and perhaps overlaid with deposit s equivalent to the Fluviomari ne se ries of the Isle of Wi ght (of which beds, howev er, no t races remain hereabouts), they partook of th e g rea t undulat ory an d crush ing movem ent of th e crust of the earth, which rea ched, with greater and great er folds, far away
,i
438
T.
RUPERT JONES ON THE GEOLOGY AND
into the Alpine region of Europe; and they were left in the synclinal position above referred to, the Chalk and strata beneath being also bent in the same great hollow curve, and equally sharing in the crush and crumpling with the superincumbent strata. 2. The great arches of these undulated strata were doubtlessly subjected to wave-action as they rose to the sea-level; and they have been destroyed down to the Chalk and the strata far below it, as seen in the Wealden area. 'I'hos e Tertiary beds which were let down into the hollow curves of the London and Hampshire districts, respectively, have not wholly escaped destruction, for they have been greatly denuded. The Chalk, being homogeneous and relatively hard, has kept its outcrop at a higher level than the soft Tertiary sands and clays, even 800 feet above the present sea-level in some of the Downs; and here and there the ferruginous and cherty sandstones of the Neocomian and Wealden series have hills of equal height; thus indicating, according to Prof. Ramsay, an old plain of marine denudation, whilst the lower flats, cut out of Tertiary material, would be a second plain of like origin; but, according to the views of other geologists, these plains rcpresent the average local level left by the wear and tear of ordinary atmospheric denudation (even without sea-action) on strata of average consistencies. The soft sub-Cretaceous clays and sands, on one hand, have been worn away deeply into the complex valley-system of the Wealds of Kent, Surrey, and Sussex; and, on the other, the London and Hampshire Tertiary areas have each its own system of flat-topped hills and divergent valleys, worked out from a gravel-capped plateau, of much less elevation (about 400 feet) than the bordering Chalk hills (about 800 feet). How far sea-action, with waves, and how far weather-action, with frost, snow, and rain, have severally operated in reducing the South-east of England to its present levels, it is difficult to define. 3. It is not, however, the Tertiary Sands that form the actual surface of the Bagshot District, but certain Gravels, which have The been referred to as coating the plateaux and hill-tops. denudation, 01' wearing away, of the surface of the disturbed Tertiary and Cretaceous strata (perhaps then not quite at rest from oscillation) was probably effected by slow marine erosion in the Later Pliocene Period, when the northern area of what is now the British Islands was uuder an arctic sca, with periodical coast-ice, and probably frequent ice-floes and icebergs. The shallow waters
PHYSICAL FEATURES OF THE llAGSHOT DISTHICT.
439
of this more southern district did their wave-work, with storms and winter-ice; and, having planed down the comparatively resisting cliffs and shoals, they ultimately left the area between Chalk hills of Snrrey and Bucks, and of Sussex and Picardy, bestrewn with the wreck of denudation. vVhatever younger beds of Tertiary date (Upper-Eocene or Oligocene) may have originally overlain the "Bagshot Sands," these latter at one time, being bared and worn down, were part if not of the Pliocene, certainly of the Post-tertiary sea-bottom, whether formed in a shallow sea, 01' in wide estuarine flats, loaded with shingle (gravel) and mud (loam). The gravel consists chiefly of subangular flints from the Chalk, with Tertiary pebbles (nsually dark in colour) ; there is also a large percentage of chert from the Neocomian sands of South Surrey, a free sprinkling of qnartz* in small pebbles (rarely so large as a thrush's egg), and occasional large blocks of concretional sandstone from the Bagshot Sand. The railway-cntting through Portesbury or Orawley Hill gives a section of a part of a Post-tertiary bank. limiting the plateaugravel against a water-worn slope of the Upper Bagshot Sand. 4. When the erosive, abrading, or denuding action began to lose its power the currents ceased to remove all the detritus which the waves had made; and the fragments of the harder rocks were left in greater 01' less profusion over the surface. Thus the broken and partially rolled (and even raw and unwom) flints from the Chalk, which cropped out along the borders of this Bagshot area, and even fragments of the southern chert-beds of the Neocomian Sands beyond, were dispersed on banks and shoals, and mixed with pebbles from the Lower Eocene pebble-beds lying on the Ohalk and exposed with it along its ant-crop. The "Bagshot Sands" of some parts of the area supplied also quantities of sand and loam, and many "Barsens." Shifted here and there hy changeable currents and coast ice, sorted in one place, massed together in another, and worked upon sometimes by floating ice, gravel coated the flats, formed a nearly continuous level, and, together with the adjoining higher lines of Chalk, was ultimately deserted by the sea, either from slow upheaval, or by the retiring of the water, the quiet flood-waters or gentle tides leaving loam at the last. This completion of the high-level ;; Derived, probably at second-hand, from old wreckage of the primmval land once lying to the west of the Hugshot area.
440
T. RUPERT
JO~E8
ON THE GEOLOGY AND
gravel-flats may be looked upon as a special datum-level in the history of the Bagshot District. 4. As this extensive gravel-fiat or sub-marine plain came nearer to the surface, and finally appeared above it, the shallowing water, becoming sea-creeks, ate out the rising plateau, with the aid of winter-ice, and roughly carved out the present valleys. Then sub-aerial agencies took part in the further alteration of their features. The valleys were deepened and widened by rain and snow. The heavy rainfall of the Pluvial Period, with its fierce storms, not only cut out the spurs and ridges more definitely, but formed lakes, in the lines of drainage, having gravel lips or beaches which were to be the benches and terraces of the valleygravels at different levels, as we now see them. Certain portions of the plateau-gravel obstinately resisted denudation, being fortified by the hard, compact, ferruginous character of its lower layer.* Hence, probably, limits were set here and there to the destruction of the plateau; and decidedly certain spots so well opposed the abrasive action going on around, that they figure as conical, and almost isolated, hills at the present day. Such are the Obelisk Hill at Camberley, and Edgebarrow Hill, near Sandhurst.] These layers of irony sand and gravel are not limited to the bottom, but occur here and there in the mass of the gravel, whereever water, percolating downwards, met with or made impervious Such illfiltered layers, choked or "puddled" with iron-oxide. oxide occurs in gravels at many levels over the district; wherever water brings the oxide from higher grounds to soak into the superficial gravel. At Windlesham 'the rust takes the form of bog-iran-ore, six inches thick, under peat, on clay, where gravel is absent. A point of much interest is the occurrence of this" pan" (as it is called) in the plateau-gravel, in the limited spots, now defined Water in some cases by the circumdenudation of conical hills. must have collected and lain iu certain hollows, and accumulated the ferruginous matter by percolation, before the cutting-out of gullies and valleys destroyed the old flat, or high plain. It may have been some of the sea-water whilst retreating, or it may have been long-standing fresh-water in an interval of great duration. In both sets of gravel (that of the plateaux and that of the iF
t
See" Proc. Geol. Assoe.," Vol. vi, p. 208. See ., Proc, Geol. Assoc.;' Vol. vi, p. 334.
PHYSICAL FEATURES OF THE BAGSHOT DISTRICT.
4H
valleys) we find numerous Sarsens, or blocks of compact sandstone, derived from the Upper Bagshot Sand. They are broken and water-worn; but those in the Low-level Gravel to a much greater extent than those in the higher gravel. The breaking-up of these masses (in their native matrix of the Frimley Ridges, sometimes 12 feet long, by five, and two feet thick) may have been due to frost rather than to violence; but the surfaces bear evidence of having been slowly worn by sand and pebbles washed over them persistently, worrying out cup-shaped hollows and funnel-like holes, especially where the small trumpet-shaped apertures of the tubes, due to the congenital root-marks, or the ends of small stems on fractured faces, presented depressions suitable for the erosive action of eddying sand and water. In some instances a highly glazed surface occurs on the stones, due to the polishing action of blown sand. As this latter operation must take place on a shore or shoal above the water-level, and yet these stones have been imbedded in strata laid-down by water, we have here, as elsewhere, indications of a lapse of time, while the several natnral operations were taking place, with intermediate oscillation of level, though possibly only of the local sand-banks and beach-lines. Neither the plateau-gravels nor those at lower levels in the neighbourhood of Bag-shot and Sandhurst have as yet furnished any fossils, except those in the flints derived from the Chalk, and the sponge-spicules in the Neoeomian chert. No mammalian bones nor stone-weapons of Archaic ;\ian have been yet met with in the high-level valley-gravels here as they have elsewhere been found in the Thames Valley, at Reading, and lower down by London. The low-level valley-gravel is also barren here, though rich with remains of wild animals, and not destitute of human relics, in the valleys of the Kennet and Thames. In the latest deposits of silt and sand, however, in the deserted bed of one of the affluonts of the Blackwater, namely, along a branch of the Wish, just within the Surrey boundary, and within a few hundred yards of the Staff College, flint-flakes and implements have been left by Prehistoric Man. When To return to the history of the Gravel of the Valleys. tbe estuarine or partly lacustrine waters drained away as the land slowly rose (or the water sank), when the land was, as it well may have been, shoals and variable islets, the wash and swirl of tide and storm mnst have been the first instruments in ronghly carving-ont the present features. Floods and pack-ice of hard winters would
442
T.
RUPERT JOliES ON THF: GEOLOGY AND
account for many of the evenly -scooped valleys, and, still more, for the presence of the lower-level gravel, irregularly scattered at various elevations. These gravelly benches, showing where the waters rested for a time, lie at equal, or nearly equal, levels on the sides of the greater valleys. Between the Blackwater River and the summit of the Chobham Ridges, three distinct levels or benches occur, where the gravel thus rests; and these must have been deposited there by a more powerful agency than ordinary rains and 'I'he gravel is of the same character as floods of the present day. that on the high level, that is, somewhat water-worn, or subangular, not pebble-like in character, only having some Tertiary pebbles mixed with it. Much-worn fragments of "Barsens" and chert are also present. Except at a few spots, this gravel is paler and looser than the higher gravel, having less iron-oxide in it j this material baving been largely washed out during the rearrangement of the gravels. Such a bench or terrace of gravel is particularly apparent at Camberley, a little above the Railway-station, at and behind the Staff College, and along the 270 feet contour round the spurs of the plateau. Yorktown Church also stands on an outlier of this terrace. A gravel of lower level is worked for road-metal in the Frimley Road, near Yorktown, and its terrace crosses Yorktown. 'I'hese have corresponding terraces, at nearly the same levels, on the other side of the Black water, on the sloperising to Hartford-bridge Flats. In relation to the higher valley-gravels, there are some patches that seem to have a somewhat different origin. Near the Obelisk Hill, for instance, which is a small isolated conical hill, owing its shape to a very tough band of pan-ironstone, and which stands out from the spurs descending from Easthampstead Plain, is a gravel-bed lying in the bend between the hill and the neighbouring spurs of It is difficult to Diamond and Portesbury* or Crawley Hills. imagine how this came to be deposited, unless we suppose (as suggested by my friend Capt. C. C. King, F.G.S.) the neighbouring slopes, then shoals, just" a-wash," to have been covered by stranded pack-ice, which, having carried off masses of plateau-gravel from the cliff of the upper part of the creek, had floated them into deeper water, to be stranded against Obelisk Hill, where they melted. N ear Hawley, on the west side of the Blackwater, the Same thing
*
I regret not having- examined this "bury" for earthworks before the railway was cut through it. A groat; of Edward II. was found bere when the cutting was first made, about ten years since.
PHYSI CAL
FEAT UR E S OF Til E DAGSH OT DI STRI CT.
443
seems to have occurred j for lin isolated patch of red g ravel bas been plac ed th ere, probably by float ing icc, which , escaping fr om the obstacle of Obelisk Hill, had been swept down th e valley to th e west by th e same pr evalent Easterly wind. Oth er slighte r pat ches th a t h ere and th ere coat the hill sides were probably caused by th e mere wash of wind and tide under ordinary circumst ances of weath er ; th e sto rmy spring winds from t he northeast probably leavin g th e stronge st marks on th e wes tern slopes . Th ese g ra vels, th en, lire important in g iving sha pe to th e land, and character to i ts veg etati on. The scanty-s oiled h illt ops, with th eir impervious band of " pan ," only afford subsistence to th e firtrees and heath er. Tap-rooted t rees g row badly th er e j and the experienced physical-ge ologi st would see without excava tion th at that condition was due to want of depth of even a sand-soil, and though to insufficiency of water in g en eral, yet also to its over-abundance at times, making a swampy turf. The rain-water fails to penetrate the "pan," and weeps ont at a definite level along the hill sides, at th e edg e of th e platea u- a level marked by the head of a widenin g t ra in of coarse marsh- grass down the slopes , and a relat ively more luxn rian t veg etation. Th ese lin es of wate r-issue, we may reasonably assnme, ha vc to 1\ considerable degree helped to modify th e hill-features, which had been roughly carved out by th e retreat ing sea and by t he floating winter-ice." Not only does rainwat er , ru nnin g over the exposed edge of hard " pan " hollow out th c sand below, but wat er , issuin g below the gravel, bring s with it, wh en in force, so much sand th at th e ha rd bed s a re undermined , and fall bit by bit at th e vall ey-h ead. \ Ye must, however, ask for g reatcr water-p ower, compa red with t hat of to-day, to have exist ed fon nerly-c-wheth er as ra in or snow-Hoods, for th e e xcavation of such upper valleys, mere cul-desacs, with heavy coverings of large flints, as that betw een Cra wley and Diamond H ills, and th at ope ning int o \V ishm oor on the ot her side of Diamond Hill. T he lat ter short vall ey seems also to have been snfficiently full of wat er to have received a depo sit of silt and sand 18 inch es th ick, in which flint-Hakes and implements are found (as above mentioned), pointing to former occupation by Prehistoric Man. t
* Sinc e writing this paper I hav e seen a very interesting and suggestive paper, on th e geol ogy of th e San dhur st di strict, by the Rev, Alex. Irving, n.sc., F. G.S., in th e" San dhn rst Parish :Magazin e," 1880 . t See " Pro c, Geol. Assoc.,' • Vol. vi, p. 329; and" J ourn al Anthropologi cal In sti tute," Vol. ii, p. 365. 2
K
444
T. RUPERT JONES ON THE GEOLOGY AND
§ 7. Antiquities.-Of later date than the Flint-implement Station abovementioned, the traces of successive occupation of the hill and valley-lands are numerous about this district. The track-ways, at places hollow, converging from the east on the old ford over the river at what was once known as Broadford, subsequently as Blackwater Ford, and Bridge, and now as Blackwater, are nutnerous and deeply worn. They occur on both sides of the intervening hills, as Obelisk Hill at Camberl-y, and Osnaburgh Hill in Yorktown. Near these old lines of route were probably many halting-places, especially where the side -trucks entered the main cast and west artery of traffic or of passage. There the British nomad re-fashioned and re-chipped his arrow-heads and celts of flint. Thus at the abovementioned stone-station, near the Staff College, on the little stream draining into \Vishmoor,* also in the gardens of the Royal Military College Terrace, bordering the lower part of the \Vislimoor stream, and in the neighbonring part of Yorktown, at the old ford-ways ncar Sign Farm (Fl'imley), near the church at Sandhurst, and in the grounds of \Vellington College, flint-flakes, more or less dressed and used, have been found in varying quantities. Outside our particnlar district, flakes and implements have been gathered along the northern slopes of the Hogsback, overlooking this area, as at Wanborough ; also at Scale and Puttenham, on the south side; and further away, at Greywell an.l \Vanborough, near Odihaui. A small cinerary urn (British or Brit-Roman) and some fragments of similar pottery, have been found at a gravel-pit on the Frimley Road, neal' Yorktown. Here a Low-level gravel forms a slight rise, marked by a small gronp of cottages, above the marshy ground of the lower part of the Cam berley Valley, and has been evidently the site of an old occupation, on the south side of a pond iuad« by damming the little stream. This was called Prance or French Pond on old maps; and has been completely drained within the last fifty years. The Bagshot District still possesses some prehistoric tnmuli of the great men of their day:On Easthampstead Plain, near Wickham Bushes, in Easthampstead Park, near Woden's Hill, and again on the Hartford-bridge
*
This IS an ancient name, meaning the great d,·ink.tuatej·; see Mr Buckley's remark at page 365 of the" Journal Anthropological Institute," Vol. ii., 1873.
PHYSICAL FEATURES OF
THE BAGSHOT DISTRICT.
445
Flats, near Minley, where a fine polished celt (now in the possession of MI'. Raikes Currie) was found in what appears to have been a primary interment, with ashes and burnt bones, near the site of J\linley Church. One large tumulus on Hartford-bridge Flats was opened many years ago, and the urn C?) is said to have been taken to Hugenden in Bucks by 1\11'. Norr'is, who had had the mound examincd. With these indications of carly life may be classed the British Camp and the Roman Road described by the Rev. A. Irving' and Capt. C. C. King in the" Proceed. Geol. A ssoc.," Vol. vi, p. 331, &c. The earthworks overlook Brnckuell, and is known as "Crusar's Camp."* After thcse come traces of Roman or Brit-Homan life in the old Station at ,Vickham Bushes, with its British and RomanoBritish pottery, tiles, and coius.] This clearing, with its close smooth turf and ancient hawthorn trees, in the depth of the pinewood, has its counterpart in another and similar spot further 'eastward, which lias, however, yielded no remains. The Roman Hoad, altered in name to the" Devil's Highway," and uniting Silchester (Calleva Attrebatum) with Staines (Pontes), runs not far from this old yillage of'W ickham Bushes, the derivation of w liich from Vicus is sufficiently evident. Near this same' road, "on property now called Broom Hall, which is about a mile east of Charter's Pond, and near Sunuingdals Station,"t the ancient marble statue of a Roman warrior (Emperor ?) now in Mr. ,Vaterer's garden at Bagshot, was found. It may have been left there on its way from the landing-place at Staines to decorate the Forum of Calleva, when the Saxon raid, which destroyed that seat of Roman Power, swept by. Homan remains have been recorded from Hadley or Rapley's Farm and elsewhere on the old hi ghway to the eastward towards Staines.
*
In his" Itinerarium Curiosum," &c., 1724 fol. London, 1'. 169 (Iter -vii.), Dr. 'V. Stnkely wrote as follows ;-" Upon the great moor between Bagsbot and Okingham, near East-hamstead park, we saw a large camp upon a hill, doubly ditch'd, commonly call'd CfESa1"s camp, as many more, without any reason. There has been a well in it, and both roman. and british coyns have been found there-one of Cunobelin in silver. Its figure is not reguJar, but conformable to the top of the hill. Near it are two large barrows, Ambury and J;;dgbnry." t See" Work at Wickham Bushes" in tbe "Tenth Annual Report of the Wellingtou College Kat. Sci. Soc.," 1880, p. 90, with four plates. :t: John Waterer, Esq., has favoured us with this information.
446
T. R. JONES ON THE GEOLOGY OF THE BAGSHOT DISTRICT.
Lastly, traces of a later and less interesting history are conpled with the name of Bagshot Heath. Hangman's Clump, Gibbett Hill, Gallow's Lane, and Gallow's Stem (the site of an old gallows, a portion of which stood till of late years) all point to the time when travelling from London to Southampton and Salisbury was a journey of no mean danger, or at least, of anxiety, thanks to Turpin and his gang-one of whose most notorious haunts was the ancient "Golden Farmer" publichouse, near the modern" Jolly Farmer" inn, at the junction of the Portsmouth and Southampton Roads, a mile west of Bagshot. NOTE.-According to a map constructed by the Officers of the Senior Department of the Royal Military College in 1836, the Roman road from Silchester (Calleva Attrebatum) to the Bridges at Staines (Pontes) entered the Bagshot area at the west of the Finchamstead district, crossing the Blackwater at Thatcher's Ford, and passing through West Court to Crowthorne. From this it was continued in a perfectly straight line over Easthamstead Plain, and between the two westernmost of the four or five ponds which lie south of Rapley Farm to Duke's Hill. In rising over the western spur of the plateau, a small road diverges from LodgeHill to "Wickham Bushes," returning to the main road at the eastern side of the plain. Where it passed between the ponds at Rapley the water, either by neglect or' by design, has been allowed to cut through the roadway, thus forming one pond instead of two. At both Rapley Farm and Duke's Hill Roman and RomanoBritish pottery has been found. From Duke's Hill the road ran direct to a small island in the Thames, lying about one-third of a mile north of the present bridge, and about one-eighth of a mile south of "London stone." As this passage must have been effected by two bridges, the origin of the name of "Pontes" is distinctly traceable. In its course the road touched the southern end of Charter's Pond, and passed over what is now the southern creek of Virginia Water, which lies west of the Wheatsheaf Inn, through the yard of which inn it also passed. Foundations have been found there, with bricks and pottery. Similar remains were also found at Bakeham House, further on.-O. O. KING.
ON THE GEOLOGY AND PHYSICAL FEATURES OF TIlE BAGSIIOT DI STRICT.
By PROFESSOR T. RUPERT JONES, F.R.S., President of th e Geologists' A ssociation, &c. (R ead May 7t h, 1880.) CONTEN TS.
§ 1. Are a of th e Dis trict described. § 2. F eatures of the Bagshot District. § 3. Fauna and Fl ora. § 4. Na tural Drainage and Water.supply. § 5. Geological Structure of th o District: the Bagshot Sands,-oZ, Upper; b, Middle; 0, Lower Bagshot Sands; d, Sarsden Stones. § 6. Geological History of th o District: 1. 'I'he Bagshot Sands an d the underlying Strata thrown into undulations.-2. The Denudation of the Arches or An ticlin es.-3. The High-level (or Pl ateau) Gravel.-4. Th e L ow-lev el Grav els (or High.level Valley-gravels); the partial Dest ruc tion of th e higher Gravels; Sarsdeus in both sets of Gravels; Local pa tch es; Va lley-bot toms, § 7. Antiquities.
§ 1. .dl'ea.-The sands and clays of the group of Tertiary strata kn own as the "Bagshot- Sands" occupy in th e Bagshot district an ar ea of about 300 square miles, extending about 24 miles from E sher on th e east to Willchfield on th e west , and 12 miles from A scot on the north to Al dershot on the south ; and th ey reach an altitude of about 400 feet above the sea-level. In ot her words, th is division of the Lower Tertiari es is well developed in t hose parts of Hampshire, Berkshire, Surrey, and Middl esex that lie between the Chalk ranges of the H og' s-back and th e Surrey Hill s on one side, and th e line of the Thames on th e oth er, with th e Chalk ranges of Berks and Buckingham shire parall el to it. Th e hill-ranges of Easthampstead Plain, the Chobham Ridge s, Finchampstead Ridges, and th e Fox Hills, separated by th e Blackwater from the Hartford-b ridg e Flats, which extend west. ward in the direction of Odiham and Basingstoke, are all composed of the "Bagshot Sands." Th ese strata lie on "London Clay," II Bag shot, a hamlet of Windl esha m, was brought to notice as a post ing station on the main r oad fr om L oudon to Salisbury and th e West.
430
T.
RUPEH T JON ES
ON Til E G EO LOG Y AN D
r esting on Ie W oolwich and R eading Beds," below which is Chalk , in a broad shallow" syncline." Gra vel coat s th e tops of the hills, fringes th e hillsides here and th ere, and covers th e valley-bottoms at various levels. § 2. Features.-This country of the Bagshot Sand s mainly consists of flat-topp ed hill-r anges or small plateaux, formed of sandy stra ta, with g ra velly tops. Al ong th eir edges they are cut int o frequent g ullies and spurs, sloping downward quickly into valleys. These are na rrow at th eir upper sources, where they leav e the bill-l and, and broad and shallow below, where the y reach th e river-lines. Thu s they open int o the wide vall eys of th e \Vey, Blackwat er, and Loddon, to which th ey bring tribu tary streamlets j and all merge int o the g reate r valley of th e Thames. The district is not rich with fossils, nor free to expose many geological charms in quarries or other sections j but its physiography is very intoresting.e Lo okin g around from the floors of many of the valleys, we can r eadily discern th e main feature of th e area, characteristically mark ed by th e long line of level crest all around, standing out against th e sky. E ven where the hilltops (as frequently occurs) are crowned with pine-woods (the only tre es finding congenial soil for full development), th e same general level of the terrain is apparent ; and, indeed, th e evident general levelness of th e upper line of th e country cannot fail to be st riking to th e intelligent observer. The flat hill-top s keep their long l evel edge-lines, because of th e hard er gravel and seams of sand, closely cemented by iron-rust, which pr otect th e weaker materials below. The more promin ent spurs and other marked features of th e landscape, with th eir regul ar slopes and elegant outlines, lire dne to th e existe nce of this " pan," which lies from 3 to 12 feet below the platform. The formation of thi s irony layer was caused by water lodgin g here and th ere on the once-continuous gravel plain (since cut into separate hills and ridges). and carrying the iron-oxide downwards by percolation to the first imper vious layer, which is often th e und erlying sand itself "puddled," or made water-tight, by the ferru gin ous cement filling its pores and interstices. Similar " pan " or "rust " also underli es th e gravelly sur face in the vall eys at many places.
* See als o Proceed . Geol. Assoc., Vol.
vi. p. 329, &c.
PHYSICAL FEATURES OF
THE BAGSHOT DISTRICT.
431
Along the borders of the main hill-ranges, or more strongly marked table-lands, there are many outlying hills and "uuderfeatures," consisting of' similar sandy materials. Those on the outside of the area are based on the London Clay. Those within the area consist of Upper, or of Middle Bagshot Sands, as the case may be. Some of these "outliers" reach the level of the plateau-gravel, and retain a capping of it, hardened and preserved by the irony "pan." Others, at a lower level, have bare sand tops; others bear valley-gravel at different levels, according to position. § 3. Flora and Fa1lna.- Vegetation is not luxuriant, as far as diversity of plants is concerned. The up-land bears Firtrees, Furze (Gorse or Whin), Heath, and Whortleberry as its chief plants." The low-land, lying nearer the clay, and therefore more silty or loamy, and better supplied with water, contains a more varied flora. In these hollows much of the land is boggy. Thus the long Marsh-grasses, the Bog-moss, the Bog-myrtle, Cross-leaved Heath, Cotton-grass, Kingspear, Sun-dew, and Alder find congenial sites, with smaller and less noticeable vegetation, in these parts. Still lower down, in wider valleys and in stiffer soil, the Oak and Elm attain their normal proportions. SOME COMMON HEATH Ulex europeeus, Common Furze ... Ulex nanus, Dwarf Furze Genista anglica, Petty Whin
..."'15
PLANTS.
i
Sarothamnus scoparius, Common Broom Erica tetralix, Four-leaved Heath Erica cinerea, Ashy Heath Calluna vulgaris, Scotch Heather Myrica gale, Bog-myrtle
{ {
Chiefly on the lines of roads or paths, but sometimes On the tops of hills. Road-sides. Abundant (in dampish places). More abundant (on the Heaths). Most abundant (do.) Swampy parts of Heaths, along the edges of streams or ponds.
Drosera rotundifolia, Round-leaved Sundew Drosera longifolia, Long-leaved Sundew
Wet Bogs.
Pedioularis sylvatica, Common Lousewort Polygala vulgaris, Milkwort
Damp parts of Heaths.
* See
Kingsley's" Miscellanies" (My Winter Garden), Vol. ii, p. 110, &c.
432
T. RUPEHT JONES ON THE GEOLOGY AND
f
Habenaria alba. Butterfly-orchis
<.
Marshy ground round Hawley Pond.
Juncus bufonius, Toad.rush Juncus squarrosua, Heath-rush Carex dis tans, Distant Carex
}
Damp Heaths.
Mollinea ceerulea, Purple Mollinea
{
Agrostis setacea, Bents ... Nardus striota, Mat.grass
::: }
{
Everywhere in the low gronnds. By the sides of all heath paths or tracks, especially in marshy parts.
Sphagnum, Lycopodium, and Equisetum are found in the Bogs and Ponds. [A. H.
CLAYPOLE.]
Many birds inhabit the district. In a short walk through some plantations (chiefly fir) in one of the valleys, the late S. P. Woodward recognized the notes of more than a dozen kinds in an afternoon of June. The magpie, jay, and woodpecker are still not uncommon, in spite of the destructive gamekeeper. A pair of hawks aloe sometimes seen. Sq uirrels and hedgehogs, grasssnakes, vipers, slow-worms, and lizards are common, the Coronella snake seems to be rare, but perhaps is frequently killed in mistake for the others; frogs and toads are common, and young toads swarm over the paths and roads of the woods and heaths near water in the spring. The fauna and flora of this part of the country is carefully tabulated in the- Annual Reports of the Wellington College Natural Science Society. § 4.. Water-supply and Dlainage.-The streams, which have their channels in the larger valleys, are fed by the streamlets formed by water leaking from the gravelly tops and sandy sides of the hills. Such upland lines of drainage are marked in summer by long verdant stretches of luxuriant marsh-grasses, the apex of the outdrawn bright-green triangle pointing up to the spring or leakage in the gravel above, on the edge of the plateau, and the base widening out over the narrow marshy valley at the hill's foot. In winter, the grassy verdure is replaced by light-brown, dry, coarse hay; to be again renewed in spring and summer. The rainfall is about 23 inches a year; and the water is largely stored in the gravels and sand-beds for the permanent springs ; and the peaty patches of the higher valleys help in the storage of water to supply the amount carried down by the rivers.
PHYS ICAL FEATURES OF TilE BAGS HOT DISTRI CT.
433
Thu s the wat er-sup ply and, the refore, th e river-drainage wholly depend on rainfall, rul ed by the geological st ructure of th e area. W ells are supplied with water at differ ent levels. There are shallow wells in the gravels. Others, sunk to Middle-Bagsho t beds, which are clayish, have a much better supply, especially when near the lakes which lie at that level. A deeper sinking pierces the lower sands, full of water, on th e L ondon Clay. Only B few borings are driven through this thi ck clay to th e still better water-bearing W oolwich Sa;lds and the Chalk beneath .· § 5. Geological S trllctUl·e.- T his st ructure may be briefly defined as plateaux, hills, and valleys cut out of flat layers of- I , Gr avel (glacial); 2, Bagshot Sand, Clay, and Sand (Eocene); resting on, 3, London Clays; on 4, Woolwich Sands and Clays; and on 5, Chalk. On the valley-sides, moreover, are benches and terrac es of highlevel and low-level valley-gravels. The following is a general section of the strata] : 1.
2.
3. 4, 5.
Gravel, wi th loam 12 feet. ( Upp er Bagsh ot Sands, with Sarsden St ones in place, and some t hin seams of irony loam , occasiona lly fossiliferous, with Turritell a, Na tioa, Cardium , i Ostrea, Nnmmul ites, &C. ... i50 feet. Middle Bagshot Sands, with argillaceous.I and ligniti fer ous beds, some pyrites and fossils, Cardita. pla nicosta, &c, 50 feet. l Lower Bagshot Sands 100 feet. L ondon Clay .. . '" 400 feet . Woolwich and Reading Serie s '" 65 feet. Chal k .. . ... 600 feet or more. (Seen out sid e the district, an d reached in it by boring.)
Below all these lie th e Gault, about 100 feet thick, and the L ower Greensand (or Neocomian Sand), about 800 feet, &c• • Sn ch 8S the deep well at Wokingh am, lately described in the" Geol. :Mag." Ser 2, Vol. vii, p. 421. t F or details, see Prof. Pre stwich' s Memoir in the" Quart, J ourn. Geol. Soo.," VoL iii, p. 378; and Whit ak er and others in the" Memoirs Geol. Su rv ey," Vol. iv, r- 308, &c. ! Some of these are loam y sand s, the sand being mixed with a slight q ua ntit y of clay; and this latter , being somet imes in very small scat tere d lum ps, shows that it was derivative, and that intermediate ero,sioDS had taken place during the deposition of this seri es. H enc e evidence of great lapse of time , and possibly of imp erfect record.
434
T . R UPERT J OSES OS
THE GE OLOGY ASP
Though th ere are not any considerable sections exposed in the area under notic e, t he above est imates can be fairly gathered from the neighbouring rail way-cuttings and ot her sections, as well as by the deep wells made, of late years, at Bearwood, Wellington College, W okingbmn, and elsewhere, and by the old wells in th e neigh bourh ood of the villages, as far as th eir evidence g oes. Th e sides of t he valleys tak e t heir chara ct ers from the condit ions of outcrop of th e successive horizontal beds j th e par allel contours being approximat ely equal t o the lines of outcrop. F rom thi s circumstance th e nature of dist ant hill-sides, whether on th e near or the far face of th e hill, can be inferred from the nat ure of anyo ne hill. The heads of many of the valleys are separated, one from anoth er, by 101V "cols"; and th ere are many "under-features," or nearly isolated low outliers, caused by the unequal degradation of th e spurs by weather and rain-action, or held up by high- or lowlevel valley-gravels, according t o the local distribution of th ese materials, forming benches or terra ces. Thus the gravel edges, especially at the crest of th e hill s, are , as a rul e, steep, and g ive out water ; th e sand slopes are much more g entl e, and give SOlUe water, t hough not so much in proportion as the g ravel; and th e clay bottoms, which are nearly flat, or have only a slig ht inclination, ha ve always a wet surface, as th e spring - and rain-wate r set tling on them, wit hout soaki ng in, finds it s way to lower levels. The strata consti tu ti ng t he district are pra ctically flat; but theoretically th ey ar e synclinal, being t urne d up at th eir north and south edges, t og ether with the nnderlying Chalk, Gaul t , and Greensand, as seen in th e chalk-pits and other sections near Guildford, Tongh am, &c. T hus th ey form part of the so-called "London Basin " (really a trough). which, with the anticlinal r idge of Wilts, &c., as a complement , is conterminous with th e syncline of Hants and th e Isle of Wight. a. It cannot be too often pointed out that the Bagshot- Sand series of this neighbourhood is one that teaches the broader lessons of ph, sical geology rather th an stratification or palreont ology. It teaches these physical results in th e modern configurati on of the gro und, and, therefore, it is useful in dir ecting th e observer's eye to alt eration s and changes in other formations, which hav e followed th e same laws. Some of the Up per and Middle Bagshot Sands, however, show
PHYSICA l, FEATURES OF TH E BA GSHOT n rSTRICT.
435
many interesting fossils, mostly of a molluscous nature. F alsebedding, the result of wind and tide action, are in some places well represented. Exc ept in certain beds, fossils are ra re, and, as a ru le, in the state of cast s; for the water, percolatin g easily bet ween t he particles of sand, has been able to get at the sh ell-matter and dissolve and remove it. No modern sand -ban k is rich in animal life, at least as r esidents. Sand -banks are, as a rule, shoals, or lie in sh allow water, where wave-wash and trit uration by sand must be ag reeable to few creat ures unless " to the manner born." Shells are thus easily removed. and broken j and , if broken, more easily d issolved and destroyed than in the quieter waters of greater depths, where the mud and finer particl es have found rest. Casts of Turritella, Natica, Calypt1'(l!a, Cardita, Cardium, Pe ctnncuius, L ucina, &c., are found at several spots :-Neat' " Cresar's Camp," on Easthampstea d P lain j near the Criminal Lun atic Asy lum of Broadmoor ; on the Windsor Rid e nea r the Royal Military College j by Hawley Pond j along the road by Long Cross, near ' Vindlesham ; and elsewhere. I n excavating a well at Wellington Oollege, several fossils of t he above kinds were found, and a seam with Osirea and Nummulites lceoiqatu« was pass ed through . So also at Weking Nummulites were brought up from the well at the Coun ty L unatic Asylu m. These are suffi cient to prove the geolog ical h orizon and age of these strata, The Upper Bag shot Sands contain lit tle or no clay. b. Th c middle set of strata which ap pear at th e bottoms of some of the lower vall eys hereabouts are much more loamy and g reenish. As the oxide of ir on in the common yellow sands of the Bagshot series underg oes a ch emical chang e in the p resence of sta gnant water with decomposing organic mat ter in it, and becomes g reen (drying to a greenish g rey), it is difficult sometimes to discri minate at first sight between real green "Bagsho t" and the greenish loamy and silty sand of some of th e drainage lin es leading towards th e st reams. By the presence of glauconite in the real " Bag shot ," as well as by the position of th e successive beds, the distinction can be made. Some, however, of th e Middle Bagshots, in which there is much vegetable matter, may hav e received t heir green ti nts partly or wholly from t he peculiar oxidation of the iron above refer red to. At Bng shot and Ileal' Saudh urst th e Middle Bag shots are ~
1
436
T. RUPERT JONES ON THE GEOLOGY AND
exposed, and their loamy beds are sometimes used for brickmaking. Close to the railway-station at Wellington College, the railroad is continually wet with the rain-water which percolates the thin sand over these clays, and weeps out on their surface where exposed by the cutting. The Middle Bagshots are best seen in the well-known cutting of Goldworthy Hill, not far from Woking, on the South-Western Railway. c. The Lower Bagshots are visible near W okingham and Virginia Water; also between W oking and Weybridge; at Ash, Aldershot, and elsewhere. They consist of yellow sands, and rest on the London Clay, as can be seen near Weybridge, Aldershot, W okingham, Snnningdale, and elsewhere. Resting on this impervious clay, they form a good reservoir of water; but the water is not everywhere good, for it is often contaminated by the pyrites of the clay giving off sulphurous salts and iron. Near the exposed junction of this sand with the London Clay, it often thins out over the latter, owing to the slope of denudation and the lie of the beds. In this case it is better timbered than where the sands are thick; for the trees have a firmer soil and more water. The clay grounds can be readily distinguished by the vegetation of their surface; for the eye recoguizes at once better herbage, finer crops, and a free growth of oak and elm. The recognition of the presence of hard clay under an out-thinning edge of similar sands in the New Forest, Hampshire, enabled the late Mr. Menzies, when a young man, to account for the stagheading and decay of trees, which had long puzzled older heads than his. d. Sarsden Stones.-In the Upper Bagshot Sands are numerous blocks of fine-grained, compact, white sandstone, lying not far apart one from another, along one horizon (near the surface ofthe Frimley Ridges, for instance) j and, doubtless, once occurring as far as these Upper Sands extended. They are roughly oblong, about 12 feet long, and less; rounded below, flatter, usually, above; with a friable and ferruginous exterior where they meet the sands in which they are imbedded. They are evidently portions of the sands consolidated locally by siliceous cement; but how the silex became dissolved and reset is a very difficult question, not yet solved. These stones, in many instances, have been freed from their sandy matrix, and lie in the derivative gravels, in either a slightly or much worn state. Some have become more ferruginous and friable j some retain
PHYSICAL FEATURES OF THE BA OSHOT DI ST RICT.
43 7
Se veral show traces of the rootlets and th eir internal hardn ess. t h in ste ms origin ally enclose d in th e sa nd ; some (p ossibl y from Occasionally the a little distance) contain flint-fragm ents. weath erin g ha s di ssect ed t he m so far as to show a decided concre t ionar y str uct ure , to which also th eir convexity, or roughly lenticul ar shape, ha s reference. Elsewhere these st ones lie about on th e surface of th e coun try in large quantities, and have been call ed" g rey wether s," since th ey look like sh eep; and by the older nam e of" Sarsdens," supposed by th e late R ev. J. A dams t o be of Sa xon origin, meaning " sail' " (sor e, troublesom e), " stan es , . (s tones), as, ind eed, th ey were t o early sett le rs and cultiva t ors of the soil. The se stones are als o called "Sarsen " or" Sa ssen," equivalent to the Saxon " Sesan," stones (" R. F.," in "Geological Magazine," 1874). The bibliography of these Tertiary concretionary blocks is extensive. Much information about them, with references to writers on th em, will be found in the " Quart. Journ. Geol. Soc.," vol, x, p. 123; vol, xviii, p. 271 ; "Memoirs Geol. Surv.," vol, iv, p. 193 ; G eol. Mag. ," vol. iii, p. 296 ; vol. x, p. 200 j "Geol. Mag.," n. s. , vol. i, p. 96 j vol, ii, p. 588; "Mag . Wilts Arch. N . H. Soc. " ( Codrington) , 18 65; " Transac t. Newbur y F ield Club," vol. i, p. 107; vol, ii, p. 248 ; ., J ourn. Proc. Winch est er Sc . and Lit. Soc.," vol. i, part 4, 187 4. Th ese Sa rsdens are sough t for with an ir on rod on th e Frimley R idges, and when found are exposed by digging, and br oken up in to small square stones for pavin g or building . Th e deserted holes ar e dang erous pitfalls for man and beas t. Large specim en s found in the gravels of railw ay- cu tti ngs are similarly br ok en up , dr ess ed, and used for pitch ing or masonry. Being dense sil iceous sands to ne, 01' q uartzite, th ey are very lasting. § 6. Geological H istory of the District.-W e now turn to the g eol ogi cal h ist ory of t he Bag sh ot Dist rict. 1. The Bagsh ot Sands are th e shall ow-wat er and west ern equ ivalents of the great Nummulitic Formation, which is represented in the east by the th ick Nummulite-limestones, deposited in the open ocean of the peri od. Having been laid down by the E arly Tertiary (Eocene) seas, and perhaps overlaid with deposit s equivalent to the Fluviomari ne se ries of the Isle of Wi ght (of which beds, howev er, no t races remain hereabouts), they partook of th e g rea t undulat ory an d crush ing movem ent of th e crust of the earth, which rea ched, with greater and great er folds, far away
,i
438
T.
RUPERT JONES ON THE GEOLOGY AND
into the Alpine region of Europe; and they were left in the synclinal position above referred to, the Chalk and strata beneath being also bent in the same great hollow curve, and equally sharing in the crush and crumpling with the superincumbent strata. 2. The great arches of these undulated strata were doubtlessly subjected to wave-action as they rose to the sea-level; and they have been destroyed down to the Chalk and the strata far below it, as seen in the Wealden area. 'I'hos e Tertiary beds which were let down into the hollow curves of the London and Hampshire districts, respectively, have not wholly escaped destruction, for they have been greatly denuded. The Chalk, being homogeneous and relatively hard, has kept its outcrop at a higher level than the soft Tertiary sands and clays, even 800 feet above the present sea-level in some of the Downs; and here and there the ferruginous and cherty sandstones of the Neocomian and Wealden series have hills of equal height; thus indicating, according to Prof. Ramsay, an old plain of marine denudation, whilst the lower flats, cut out of Tertiary material, would be a second plain of like origin; but, according to the views of other geologists, these plains rcpresent the average local level left by the wear and tear of ordinary atmospheric denudation (even without sea-action) on strata of average consistencies. The soft sub-Cretaceous clays and sands, on one hand, have been worn away deeply into the complex valley-system of the Wealds of Kent, Surrey, and Sussex; and, on the other, the London and Hampshire Tertiary areas have each its own system of flat-topped hills and divergent valleys, worked out from a gravel-capped plateau, of much less elevation (about 400 feet) than the bordering Chalk hills (about 800 feet). How far sea-action, with waves, and how far weather-action, with frost, snow, and rain, have severally operated in reducing the South-east of England to its present levels, it is difficult to define. 3. It is not, however, the Tertiary Sands that form the actual surface of the Bagshot District, but certain Gravels, which have The been referred to as coating the plateaux and hill-tops. denudation, 01' wearing away, of the surface of the disturbed Tertiary and Cretaceous strata (perhaps then not quite at rest from oscillation) was probably effected by slow marine erosion in the Later Pliocene Period, when the northern area of what is now the British Islands was uuder an arctic sca, with periodical coast-ice, and probably frequent ice-floes and icebergs. The shallow waters
PHYSICAL FEATURES OF THE llAGSHOT DISTHICT.
439
of this more southern district did their wave-work, with storms and winter-ice; and, having planed down the comparatively resisting cliffs and shoals, they ultimately left the area between Chalk hills of Snrrey and Bucks, and of Sussex and Picardy, bestrewn with the wreck of denudation. vVhatever younger beds of Tertiary date (Upper-Eocene or Oligocene) may have originally overlain the "Bagshot Sands," these latter at one time, being bared and worn down, were part if not of the Pliocene, certainly of the Post-tertiary sea-bottom, whether formed in a shallow sea, 01' in wide estuarine flats, loaded with shingle (gravel) and mud (loam). The gravel consists chiefly of subangular flints from the Chalk, with Tertiary pebbles (nsually dark in colour) ; there is also a large percentage of chert from the Neocomian sands of South Surrey, a free sprinkling of qnartz* in small pebbles (rarely so large as a thrush's egg), and occasional large blocks of concretional sandstone from the Bagshot Sand. The railway-cntting through Portesbury or Orawley Hill gives a section of a part of a Post-tertiary bank. limiting the plateaugravel against a water-worn slope of the Upper Bagshot Sand. 4. When the erosive, abrading, or denuding action began to lose its power the currents ceased to remove all the detritus which the waves had made; and the fragments of the harder rocks were left in greater 01' less profusion over the surface. Thus the broken and partially rolled (and even raw and unwom) flints from the Chalk, which cropped out along the borders of this Bagshot area, and even fragments of the southern chert-beds of the Neocomian Sands beyond, were dispersed on banks and shoals, and mixed with pebbles from the Lower Eocene pebble-beds lying on the Ohalk and exposed with it along its ant-crop. The "Bagshot Sands" of some parts of the area supplied also quantities of sand and loam, and many "Barsens." Shifted here and there hy changeable currents and coast ice, sorted in one place, massed together in another, and worked upon sometimes by floating ice, gravel coated the flats, formed a nearly continuous level, and, together with the adjoining higher lines of Chalk, was ultimately deserted by the sea, either from slow upheaval, or by the retiring of the water, the quiet flood-waters or gentle tides leaving loam at the last. This completion of the high-level ;; Derived, probably at second-hand, from old wreckage of the primmval land once lying to the west of the Hugshot area.
440
T. RUPERT
JO~E8
ON THE GEOLOGY AND
gravel-flats may be looked upon as a special datum-level in the history of the Bagshot District. 4. As this extensive gravel-fiat or sub-marine plain came nearer to the surface, and finally appeared above it, the shallowing water, becoming sea-creeks, ate out the rising plateau, with the aid of winter-ice, and roughly carved out the present valleys. Then sub-aerial agencies took part in the further alteration of their features. The valleys were deepened and widened by rain and snow. The heavy rainfall of the Pluvial Period, with its fierce storms, not only cut out the spurs and ridges more definitely, but formed lakes, in the lines of drainage, having gravel lips or beaches which were to be the benches and terraces of the valleygravels at different levels, as we now see them. Certain portions of the plateau-gravel obstinately resisted denudation, being fortified by the hard, compact, ferruginous character of its lower layer.* Hence, probably, limits were set here and there to the destruction of the plateau; and decidedly certain spots so well opposed the abrasive action going on around, that they figure as conical, and almost isolated, hills at the present day. Such are the Obelisk Hill at Camberley, and Edgebarrow Hill, near Sandhurst.] These layers of irony sand and gravel are not limited to the bottom, but occur here and there in the mass of the gravel, whereever water, percolating downwards, met with or made impervious Such illfiltered layers, choked or "puddled" with iron-oxide. oxide occurs in gravels at many levels over the district; wherever water brings the oxide from higher grounds to soak into the superficial gravel. At Windlesham 'the rust takes the form of bog-iran-ore, six inches thick, under peat, on clay, where gravel is absent. A point of much interest is the occurrence of this" pan" (as it is called) in the plateau-gravel, in the limited spots, now defined Water in some cases by the circumdenudation of conical hills. must have collected and lain iu certain hollows, and accumulated the ferruginous matter by percolation, before the cutting-out of gullies and valleys destroyed the old flat, or high plain. It may have been some of the sea-water whilst retreating, or it may have been long-standing fresh-water in an interval of great duration. In both sets of gravel (that of the plateaux and that of the iF
t
See" Proc. Geol. Assoe.," Vol. vi, p. 208. See ., Proc, Geol. Assoc.;' Vol. vi, p. 334.
PHYSICAL FEATURES OF THE BAGSHOT DISTRICT.
4H
valleys) we find numerous Sarsens, or blocks of compact sandstone, derived from the Upper Bagshot Sand. They are broken and water-worn; but those in the Low-level Gravel to a much greater extent than those in the higher gravel. The breaking-up of these masses (in their native matrix of the Frimley Ridges, sometimes 12 feet long, by five, and two feet thick) may have been due to frost rather than to violence; but the surfaces bear evidence of having been slowly worn by sand and pebbles washed over them persistently, worrying out cup-shaped hollows and funnel-like holes, especially where the small trumpet-shaped apertures of the tubes, due to the congenital root-marks, or the ends of small stems on fractured faces, presented depressions suitable for the erosive action of eddying sand and water. In some instances a highly glazed surface occurs on the stones, due to the polishing action of blown sand. As this latter operation must take place on a shore or shoal above the water-level, and yet these stones have been imbedded in strata laid-down by water, we have here, as elsewhere, indications of a lapse of time, while the several natnral operations were taking place, with intermediate oscillation of level, though possibly only of the local sand-banks and beach-lines. Neither the plateau-gravels nor those at lower levels in the neighbourhood of Bag-shot and Sandhurst have as yet furnished any fossils, except those in the flints derived from the Chalk, and the sponge-spicules in the Neoeomian chert. No mammalian bones nor stone-weapons of Archaic ;\ian have been yet met with in the high-level valley-gravels here as they have elsewhere been found in the Thames Valley, at Reading, and lower down by London. The low-level valley-gravel is also barren here, though rich with remains of wild animals, and not destitute of human relics, in the valleys of the Kennet and Thames. In the latest deposits of silt and sand, however, in the deserted bed of one of the affluonts of the Blackwater, namely, along a branch of the Wish, just within the Surrey boundary, and within a few hundred yards of the Staff College, flint-flakes and implements have been left by Prehistoric Man. When To return to the history of the Gravel of the Valleys. tbe estuarine or partly lacustrine waters drained away as the land slowly rose (or the water sank), when the land was, as it well may have been, shoals and variable islets, the wash and swirl of tide and storm mnst have been the first instruments in ronghly carving-ont the present features. Floods and pack-ice of hard winters would
442
T.
RUPERT JOliES ON THF: GEOLOGY AND
account for many of the evenly -scooped valleys, and, still more, for the presence of the lower-level gravel, irregularly scattered at various elevations. These gravelly benches, showing where the waters rested for a time, lie at equal, or nearly equal, levels on the sides of the greater valleys. Between the Blackwater River and the summit of the Chobham Ridges, three distinct levels or benches occur, where the gravel thus rests; and these must have been deposited there by a more powerful agency than ordinary rains and 'I'he gravel is of the same character as floods of the present day. that on the high level, that is, somewhat water-worn, or subangular, not pebble-like in character, only having some Tertiary pebbles mixed with it. Much-worn fragments of "Barsens" and chert are also present. Except at a few spots, this gravel is paler and looser than the higher gravel, having less iron-oxide in it j this material baving been largely washed out during the rearrangement of the gravels. Such a bench or terrace of gravel is particularly apparent at Camberley, a little above the Railway-station, at and behind the Staff College, and along the 270 feet contour round the spurs of the plateau. Yorktown Church also stands on an outlier of this terrace. A gravel of lower level is worked for road-metal in the Frimley Road, near Yorktown, and its terrace crosses Yorktown. 'I'hese have corresponding terraces, at nearly the same levels, on the other side of the Black water, on the sloperising to Hartford-bridge Flats. In relation to the higher valley-gravels, there are some patches that seem to have a somewhat different origin. Near the Obelisk Hill, for instance, which is a small isolated conical hill, owing its shape to a very tough band of pan-ironstone, and which stands out from the spurs descending from Easthampstead Plain, is a gravel-bed lying in the bend between the hill and the neighbouring spurs of It is difficult to Diamond and Portesbury* or Crawley Hills. imagine how this came to be deposited, unless we suppose (as suggested by my friend Capt. C. C. King, F.G.S.) the neighbouring slopes, then shoals, just" a-wash," to have been covered by stranded pack-ice, which, having carried off masses of plateau-gravel from the cliff of the upper part of the creek, had floated them into deeper water, to be stranded against Obelisk Hill, where they melted. N ear Hawley, on the west side of the Blackwater, the Same thing
*
I regret not having- examined this "bury" for earthworks before the railway was cut through it. A groat; of Edward II. was found bere when the cutting was first made, about ten years since.
PHYSI CAL
FEAT UR E S OF Til E DAGSH OT DI STRI CT.
443
seems to have occurred j for lin isolated patch of red g ravel bas been plac ed th ere, probably by float ing icc, which , escaping fr om the obstacle of Obelisk Hill, had been swept down th e valley to th e west by th e same pr evalent Easterly wind. Oth er slighte r pat ches th a t h ere and th ere coat the hill sides were probably caused by th e mere wash of wind and tide under ordinary circumst ances of weath er ; th e sto rmy spring winds from t he northeast probably leavin g th e stronge st marks on th e wes tern slopes . Th ese g ra vels, th en, lire important in g iving sha pe to th e land, and character to i ts veg etati on. The scanty-s oiled h illt ops, with th eir impervious band of " pan ," only afford subsistence to th e firtrees and heath er. Tap-rooted t rees g row badly th er e j and the experienced physical-ge ologi st would see without excava tion th at that condition was due to want of depth of even a sand-soil, and though to insufficiency of water in g en eral, yet also to its over-abundance at times, making a swampy turf. The rain-water fails to penetrate the "pan," and weeps ont at a definite level along the hill sides, at th e edg e of th e platea u- a level marked by the head of a widenin g t ra in of coarse marsh- grass down the slopes , and a relat ively more luxn rian t veg etation. Th ese lin es of wate r-issue, we may reasonably assnme, ha vc to 1\ considerable degree helped to modify th e hill-features, which had been roughly carved out by th e retreat ing sea and by t he floating winter-ice." Not only does rainwat er , ru nnin g over the exposed edge of hard " pan " hollow out th c sand below, but wat er , issuin g below the gravel, bring s with it, wh en in force, so much sand th at th e ha rd bed s a re undermined , and fall bit by bit at th e vall ey-h ead. \ Ye must, however, ask for g reatcr water-p ower, compa red with t hat of to-day, to have exist ed fon nerly-c-wheth er as ra in or snow-Hoods, for th e e xcavation of such upper valleys, mere cul-desacs, with heavy coverings of large flints, as that betw een Cra wley and Diamond H ills, and th at ope ning int o \V ishm oor on the ot her side of Diamond Hill. T he lat ter short vall ey seems also to have been snfficiently full of wat er to have received a depo sit of silt and sand 18 inch es th ick, in which flint-Hakes and implements are found (as above mentioned), pointing to former occupation by Prehistoric Man. t
* Sinc e writing this paper I hav e seen a very interesting and suggestive paper, on th e geol ogy of th e San dhur st di strict, by the Rev, Alex. Irving, n.sc., F. G.S., in th e" San dhn rst Parish :Magazin e," 1880 . t See " Pro c, Geol. Assoc.,' • Vol. vi, p. 329; and" J ourn al Anthropologi cal In sti tute," Vol. ii, p. 365. 2
K
444
T. RUPERT JONES ON THE GEOLOGY AND
§ 7. Antiquities.-Of later date than the Flint-implement Station abovementioned, the traces of successive occupation of the hill and valley-lands are numerous about this district. The track-ways, at places hollow, converging from the east on the old ford over the river at what was once known as Broadford, subsequently as Blackwater Ford, and Bridge, and now as Blackwater, are nutnerous and deeply worn. They occur on both sides of the intervening hills, as Obelisk Hill at Camberl-y, and Osnaburgh Hill in Yorktown. Near these old lines of route were probably many halting-places, especially where the side -trucks entered the main cast and west artery of traffic or of passage. There the British nomad re-fashioned and re-chipped his arrow-heads and celts of flint. Thus at the abovementioned stone-station, near the Staff College, on the little stream draining into \Vishmoor,* also in the gardens of the Royal Military College Terrace, bordering the lower part of the \Vislimoor stream, and in the neighbonring part of Yorktown, at the old ford-ways ncar Sign Farm (Fl'imley), near the church at Sandhurst, and in the grounds of \Vellington College, flint-flakes, more or less dressed and used, have been found in varying quantities. Outside our particnlar district, flakes and implements have been gathered along the northern slopes of the Hogsback, overlooking this area, as at Wanborough ; also at Scale and Puttenham, on the south side; and further away, at Greywell an.l \Vanborough, near Odihaui. A small cinerary urn (British or Brit-Roman) and some fragments of similar pottery, have been found at a gravel-pit on the Frimley Road, neal' Yorktown. Here a Low-level gravel forms a slight rise, marked by a small gronp of cottages, above the marshy ground of the lower part of the Cam berley Valley, and has been evidently the site of an old occupation, on the south side of a pond iuad« by damming the little stream. This was called Prance or French Pond on old maps; and has been completely drained within the last fifty years. The Bagshot District still possesses some prehistoric tnmuli of the great men of their day:On Easthampstead Plain, near Wickham Bushes, in Easthampstead Park, near Woden's Hill, and again on the Hartford-bridge
*
This IS an ancient name, meaning the great d,·ink.tuatej·; see Mr Buckley's remark at page 365 of the" Journal Anthropological Institute," Vol. ii., 1873.
PHYSICAL FEATURES OF
THE BAGSHOT DISTRICT.
445
Flats, near Minley, where a fine polished celt (now in the possession of MI'. Raikes Currie) was found in what appears to have been a primary interment, with ashes and burnt bones, near the site of J\linley Church. One large tumulus on Hartford-bridge Flats was opened many years ago, and the urn C?) is said to have been taken to Hugenden in Bucks by 1\11'. Norr'is, who had had the mound examincd. With these indications of carly life may be classed the British Camp and the Roman Road described by the Rev. A. Irving' and Capt. C. C. King in the" Proceed. Geol. A ssoc.," Vol. vi, p. 331, &c. The earthworks overlook Brnckuell, and is known as "Crusar's Camp."* After thcse come traces of Roman or Brit-Homan life in the old Station at ,Vickham Bushes, with its British and RomanoBritish pottery, tiles, and coius.] This clearing, with its close smooth turf and ancient hawthorn trees, in the depth of the pinewood, has its counterpart in another and similar spot further 'eastward, which lias, however, yielded no remains. The Roman Hoad, altered in name to the" Devil's Highway," and uniting Silchester (Calleva Attrebatum) with Staines (Pontes), runs not far from this old yillage of'W ickham Bushes, the derivation of w liich from Vicus is sufficiently evident. Near this same' road, "on property now called Broom Hall, which is about a mile east of Charter's Pond, and near Sunuingdals Station,"t the ancient marble statue of a Roman warrior (Emperor ?) now in Mr. ,Vaterer's garden at Bagshot, was found. It may have been left there on its way from the landing-place at Staines to decorate the Forum of Calleva, when the Saxon raid, which destroyed that seat of Roman Power, swept by. Homan remains have been recorded from Hadley or Rapley's Farm and elsewhere on the old hi ghway to the eastward towards Staines.
*
In his" Itinerarium Curiosum," &c., 1724 fol. London, 1'. 169 (Iter -vii.), Dr. 'V. Stnkely wrote as follows ;-" Upon the great moor between Bagsbot and Okingham, near East-hamstead park, we saw a large camp upon a hill, doubly ditch'd, commonly call'd CfESa1"s camp, as many more, without any reason. There has been a well in it, and both roman. and british coyns have been found there-one of Cunobelin in silver. Its figure is not reguJar, but conformable to the top of the hill. Near it are two large barrows, Ambury and J;;dgbnry." t See" Work at Wickham Bushes" in tbe "Tenth Annual Report of the Wellingtou College Kat. Sci. Soc.," 1880, p. 90, with four plates. :t: John Waterer, Esq., has favoured us with this information.
446
T. R. JONES ON THE GEOLOGY OF THE BAGSHOT DISTRICT.
Lastly, traces of a later and less interesting history are conpled with the name of Bagshot Heath. Hangman's Clump, Gibbett Hill, Gallow's Lane, and Gallow's Stem (the site of an old gallows, a portion of which stood till of late years) all point to the time when travelling from London to Southampton and Salisbury was a journey of no mean danger, or at least, of anxiety, thanks to Turpin and his gang-one of whose most notorious haunts was the ancient "Golden Farmer" publichouse, near the modern" Jolly Farmer" inn, at the junction of the Portsmouth and Southampton Roads, a mile west of Bagshot. NOTE.-According to a map constructed by the Officers of the Senior Department of the Royal Military College in 1836, the Roman road from Silchester (Calleva Attrebatum) to the Bridges at Staines (Pontes) entered the Bagshot area at the west of the Finchamstead district, crossing the Blackwater at Thatcher's Ford, and passing through West Court to Crowthorne. From this it was continued in a perfectly straight line over Easthamstead Plain, and between the two westernmost of the four or five ponds which lie south of Rapley Farm to Duke's Hill. In rising over the western spur of the plateau, a small road diverges from LodgeHill to "Wickham Bushes," returning to the main road at the eastern side of the plain. Where it passed between the ponds at Rapley the water, either by neglect or' by design, has been allowed to cut through the roadway, thus forming one pond instead of two. At both Rapley Farm and Duke's Hill Roman and RomanoBritish pottery has been found. From Duke's Hill the road ran direct to a small island in the Thames, lying about one-third of a mile north of the present bridge, and about one-eighth of a mile south of "London stone." As this passage must have been effected by two bridges, the origin of the name of "Pontes" is distinctly traceable. In its course the road touched the southern end of Charter's Pond, and passed over what is now the southern creek of Virginia Water, which lies west of the Wheatsheaf Inn, through the yard of which inn it also passed. Foundations have been found there, with bricks and pottery. Similar remains were also found at Bakeham House, further on.-O. O. KING.