12 7

REPORT OF AN EXCURSION TO THE ASSYNT

DlSTRICT OF THE NORTH-\VEST HIGHLANDS.

JULY 3RD TO 11TH, 1914.

By JOHN HORNE, LL.D., F.R.S, Director of the Excursion.

July 3rd.

THE party left King's Cross by the 7.55 p.m. express for Scotland,and reached Inverness on Saturday morning, where they werejoined by Professor Daly, of Harvard University, and ProfessorMolengraaff, from Delft, Holland. The excursionists numberedtwenty-eight. Miss G. M. Bauer acted as Excursion Secretary.

July 4th.

The party reached Lairg about 1 p.m., and proceeded bymotor-cars to Inchnadamff. For a distance of over twenty milesfrom Lairg the region occupied by the Crystalline Schists of theMoine Series was traversed. Several typical sections of theserocks, which lie above the Moine thrust-plane, were examined, toshow the marked difference in lithological characters betweenthese Eastern Schists and the types of Lewisian Gneiss betweenInchnadamff and Lochinver to the west of the great post­Cambrian displacements. Along the line of route the rocksare comparatively uniform. They consist mainly of flaggyquartz-biotite-granulites, granulitic quartzo-felspathic schists withmuscovite and biotite, and garnetiferous mica-schists occurringas thin bands in this region. The members of this series arebelieved to be of sedimentary origin, but, in places, bands offoliated granite and other igneous rocks are intercalated withthem. There is, however, a marked absence of those syntheticgneisses, due to the introduction of granitic materials, which areso conspicuously developed in the north of Sutherland. Andfurther, no inliers of gneisses of Lewisian type have as yet beendetected in the Moine Series along the Oykell Valley.

The first halt was made on the moor about four miles eastfrom Rosehall, where flaggy quartzo-felspathic biotite-schists areexposed. Here the rocks are much more highly mineralised thanin the belt near the Moine thrust-plane. In the River Oykell,close to the Oykell Inn, well-marked mullion structure wasexamined. Along this part of the Oykell Valley the MoineSchists are arranged in sharp axial folds, trending W.N.W. andKS.E. But in the sections by the roadside near Loch Craggie, andin Allt Ealag-a tributary of the Oykell River-the strike of the

128 JOHN HORNE,

schists is N.N.E., and the dip of the axial planes is E.S.E. Atthe latter locality, within half a mile of the outcrop of the Moinethrust-plane, the flaggy fine-grained quartz-biotite-granuliteswere visited, and compared with the types near Lairg Here therocks are holocrystalline, and show no trace of original clasticstructures. The grade of metamorphism is low. Passing west­wards to the southern slope of Cnoc Chaoruinn, we findmylonised rocks close to the great line of displacement at thebase of the Moine Series.

fitly 5th.

We left Inchnadamff Hotel in the forenoon by motor carsfor the south slope of Quinag, and drove to a point on the northside of Loch Assynt about four miles from the hotel. Thismountain, which rises to a height of 2,653 ft., is composedmainly of Torridon Sandstone resting unconformably on anuneven floor of Lewisian Gneiss. On the eastern slope the basalCambrian quartzites pass transgressively across successive beds ofred grits and sandstones, while on the south side of Loch Assynt,on Beinn Gharbh, the Cambrian transgression is more complete.At the latter locality the basal quartzites overlap the TorridonSandstone and rest directly on the Lewisian Gneiss near thehead of the loch. Fortunately the day was fine, the hills wereclear of mist, and these striking geological features were seen toadvantage.

Leaving the motor-cars on the north side of Loch Assynt, theparty ascended the southern slope of Quinag, after examining thepebbly grit, or breccia, which rests upon decomposed LewisianGneiss at the roadside near the loch. The succession of felspathicgrits and sandstones with scattered pebbles of various materials,some of them not now found in place in the Lewisian Gneissarea to the west, here forms the conspicuous feature. Thefreshness of the microcline felspar in the coarse sediments, theoccasional occurrence of wind-eroded pebbles (dreikanter), andthe irregular false-bedding, point to arid or desert conditionsduring the deposition of this division of the Torridonian system.Attention was directed to the evidence on the north side of themountain indicating the highly-eroded land surface on which theTorridon Sandstones lie (see Plate 12). On the northern slope ofSail Ghorm the red sandstones abut against a pre-Torridonianhill of gneiss which rises to a height of about 1,200 ft. abovethe general level of the gneiss plateau.

The party next proceeded to examine the unconformableboundary line between the Cambrian quartzites and the redsandstones beneath. The contrast between this base-line andthat separating the Torridon Sandstone from the Lewisian Gneisswas emphasised. The evidence points to the conclusion that theLewisian Gneiss and Torridonian strata were subjected to pro-

PROC. GEOL. Assoc., VOL. XXVI, PLATE 12.

[Photo by R. LU1Zl', H.M. Geological Survey.

TORRIDON SANDSTONE CAPPED WITH CAMBRIAN QUARTZITE, QUINAG.

I o face page 128

EXCURSION TO THE ASSYNT DISTRICT. 129

longed denudation before the deposition of the Cambriansediments. Hence we find the double unconformability of theCambrian quartzites on the Torridon Sandstone and LewisianGneiss so plainly seen on Beinn Gharbh south of Loch Assynt.

The great development of Cambrian quartzites on theeastern slope of Quinag was next referred to, the lower portionconsisting of false-bedded flaggy grits and quartzites. and theupper composed of fine-grained quartzites with worm-casts andburrows (the pipe-rock subdivision). The five subzones of thepipe-rock were examined, and it was shown how the worm-castsare arranged vertically in the quartzites in the undisturbed arealying to the west of the post-Cambrian displacements. In thisrespect they differ in a remarkable degree from the members ofthis subdivision in the displaced masses near the Moine thrust,where the pipes are bent and flattened in the direction of thepost-Cambrian movements.

July 6th.

We left Inchnadamff by motor-cars and crossed the plateauof Lewisian Gneiss for a distance of nine miles to Lochinver andStrathan. Unfortunately the day was wet and unfavourable forthe examination of the sections of Lewisian Gneiss. Only a partof the programme was accomplished. In the course of thisexcursion special atten tion was directed (I) to the FundamentalComplex of the Lewisian Gneiss, (2) to the basic and ultra-basicdykes traversing this complex, and (3) to the modification of thegneiss and dykes along lines of movement in pre-Torridoniantime.

On the south side of Strathan Bay one of the interestingtypes of the Fundamental Complex was visited. It consists of agrey basic mass with dark streaks containing small garnets. Inplaces it is rudely banded and has the appearance of a massiveigneous rock. Dr. Teall regards the variety without garnet,which contains hypersthene, augite, and plagioclase, as a typicalexample of the Baltimore gabbros. It is traversed by veins ofacid pyroxenic gneiss without chilled margins which are bandedwith the basic material. This mass is intersected by severalnorth-west basic dykes. The party followed the boundary linesof one of these dykes and found clear evidence of chilledmargins.

At Lochinver we examined typical exposures of the quartz­pyroxene-gneiss, which is so largely developed in the unmodifiedareas between Lochinver and the base of the Torridon escarp­ment in the Assynt region. The most characteristic feature ofthis type is the blue or semi-opalescent quartz. In addition tothe pyroxene, hornblende is also an essential constituent, and inplaces there is a gradual passage from the pyroxene-gneiss intogrey hornblende-gneiss. Near the mouth of the Inver River

13° JOHN HORNE,

one of the basic dyke s was examined at a point where ittraverses the undefonned portion of the Fundamental Complex.

Between Lochinver and Brackloch a halt was mad e to seethe modification of the gneiss and dykes alon g line> of pre­Torridonian movem ents trending in a W.N.W. direction. Nearthe junction of the Lochinver and Stoer roads the gneisses havebeen folded on vertical axes, the plan es of foliati on being nearl yverti cal. The boundary line between the quartz-pyroxene-gneissof the Fundamental Co mplex and this belt of secondary foliationis well defined. Within th is belt the gneisses appear as flaggy,granulitic, hornblend e-biotit e-gneisses, and the dykes as horn­blende-schists.

Owing to the unfavourable weather we were prevented fromvisiting one of the prom inent cast and west lines of movementnear Loch a' Ghleannan Shalai ch, two miles W.N .W. of TornoreLodg e, Loch Assynt. This was a disappointing featur e, foralong this belt the gradual changes in the gneiss as the narrowshear-zone is approached are clearly seen. Here the blue colourin the quartz of the pyroxene-gneiss disappears, biotite isdeveloped, and the felspars are granulitised. Within the shear­ZOne the rock is completely reconstructed. It occurs as aflaggy, granulitic, micaceous gne iss, whose planes of foliationcoincide with the dir ection of the lines of movement. Thenorth-west basic dykes are deflected on approach ing this beltof secondary foliation, are con verted into horn blende-schists,and in places appear as detached lenti cles.

At Brackloch the party stopped to hamm er a typical exampleof the ultra-basic dykes which are later in time than the north­west basic series. H ere the rock is still massive, and containsolivine, hornblende, chlorite and carbonates ; and yet when thisdyke is traced in a W.N.W. direction, to a point near R iccairnit is converted into a schist with chlorite, hornblende, and kn otsof siderite, where it is affected by a line of movement.

On the north sho re of Loch Assynt, about two miles fromthe hot el, the party left the motor-cars to see the exposures ofthe fucoid-beds, the serpulite-grit and the basal dolomite belong­ing to the Olenellus horizon of the Cambrian system . Thepassage upwards from the highest sub-zone of the pipe-rock tothe fucoid-beds is here clearly seen. Attention was directed tothe flattened worm-casts, so characteristic of the latter zone, andalso to the soft cream-coloured shale near its top, which hasyielded fragments of Oienelius lapworthi. Next in order followsth e serpulite-grit with the small tubicolar Salterel/a overlain by thebasal dolomite with Saiterelia. The succession of Cambrian stratafrom the slopes of Quinag eastwards to this point on the north shoreof Loch Assynt is normal. H ere it is int errupted by th e first lineof displacement within the belt of complication. East of thispoint all the rocks ar e affected by post-Cam brian movements.

EXCURSION TO THE ASSYNT DISTRICT. 13 1

fitly 7th.The main purpose of this excursion was to study the

phenomena associated with the Glencoul thrust, the mostwesterly of the great post-Cambrian displacements in theAssynt region. Unfortunately the forenoon was misty, withoccasional showers, but as the day advanced the weatherimproved, and, at night, on the return, journey to Inchnadamff,the sky was cloudless.

On the way to Kylesku we halted at Loch na Gainmhich tosee the basal quartzites folding over the Lewisian Gneiss abo vethe Glencoul thrust-plane, the actual plane being there concealedby drift and peat. On the slope below Loch na Gainmhichwe observed, not far to the east, the double unconformability ofthe Cambrian quartzites upon the Torridon Sandstone, andLewisian Gneiss north of Cnoc Coir a' Bhaic.

From Kylesku we went by boats up Loch Glencoul to apoint on the south shore, about a mile and a half aboveUnapool House. On both sides of the sea-loch there is a finedevelopment of the undisturbed floor of Lewisian Gneiss,covered unconformably by the Cambrian quartzites. We crossedseveral subzones of the pipe -rock in normal sequ ence. Thencewe climbed the slope and examined the piled-up fucoid-beds,serpulite - grit, and basal dolomite (imbricate structure) inadvance of the Glencoul thrust. Hi gher up the declivity wesaw a beautiful exposure of the plane of this great displacement,and followed its line of outcrop for a short distance. Thedestruction of the old foliation of the Lewisian Gneiss and thedevelopment of new planes ' of schistosity in the mylonised rocksmore or less parallel with the plane of thrust were seen toadvantage.

Thence we proceeded by boats to the head of the sea-loch,and landed near Glencoul cottage, where the party had anopportunity of not ing the immense thickness (about 1,5°0 ft.) ofthe slice of Lewisian Gneiss driven westwards by the Glencoulthrust (see Plate 14.A). They observed also the clear evidence ofthe transgression of the thrust gneiss for about a mile across thepiled-up Cambrian strata on the north side of the sea-loch .Thereafter we traversed the section of displaced gneiss withits basic dykes exposed along the forest path by the side of theGlencoul River, thence up the hill slope to the base of theStack of Glencoul. Here, at an elevation 01 about 1,250 ft.,a fine view was obtained of the broad tract of thrust LewisianGneiss stretching southwards to Glas Bheinn and Beinn Uidhe,where the Cambrian quartzites app ear. Near the base of theStack of Glencoul we hammered the mylonised basal quartzites,and lower down the slope we observed the pipe -rock with itspipes flattened and bent over towards the W.N.W., in thedirection of the line of movement.

J OH N HORNE,

The Stack of Glenco ul is formed of puckered schi sts with thinsiliceous streaks which overlie the plan e of th e Moine th rust. Atth e base of the Stac k occur int ensely myloni sed rocks with thinlaminse, compose d probably of a mixture of gneiss and qua rtzit e.

J uly 8th.

The phenomena connec ted with the Ben More thrust wereinvest igated during thi s excursion. The party left Inchnad amffon foot, and walked across the plateau of thrust Cambrian lime­sto ne for a distance of about five miles, to the Beallach of Coinne­mheall, the pass between Coi nne-rnhea ll and Breabag. Attentionwas directed to the structure of thi s limestone plateau, whereth e three lowest subdivision s of the Cambrian calcareous seriesare represented, viz., th e Ghrud a idh, ' the Eilean Dubh, andSailmhor groups. The outcrop of the Glencoul thrust was indi­cated. It runs alon g the base of the western slop e of GlasBheinn j thence it trends south -eastward to the Beallach ofCoinn e-mheall and th e Oykell Vall ey, where it is overla pped byth e Ben More thrust.

T he party ascended the northern slope of th e pass, andexam ined the outcrop of the Ben More thrust-plan e where it isexposed in dip sec tion. Beneath the plane the Cambrianquartzit es are repeated by inverted folds and minor thrusts up toth e 2, 5 0 0 ft. contour line. H ere they form a thin covering overth e conce aled Lewisian rocks, which ha ve been driv en westwardsby the Glencoul thrust. Abo ve the plane th e members of theparty hammered th e deformed Lewisian Gnei ss covered uncon­formably by the T orridon Sandstone, with a well-mark ed band ofcon glom erate at th e base. Spec ial attention was dir ected to th emanner in which th e sands tones fold over and bu ckle underth e western face of disru pted gneiss.

Thereafter the excursionists followed the crags of gneiss roundto the great corrie of D ub h Loch Mo r on the south side of BenMore, where they saw the great mass of Lewisian rocks d rivenwestwards by the Ben Mor e thrust (see Plate 13). Here th erocks of the Fundamen tal Complex include pyrox enites andhornblendites, pyro xene-gneiss, and grey hornblende-gneiss withblu e quartz. The basic dykes are numerous and preserve theirW.N. W. trend. The original structures in the gneiss and dyk escan still be recognised. On the northern slope of th e corrie th eTorridon grits, sandstones an d shal es resting unconformably onthe Lewisian floor form a consp icuous feature, being th ere overlainby a thin cake of basal Ca mbr ian quartzites, which are seen tooverlap th e Torridon Sandstone and to rest dir ectly on th eLewisian Gneiss. Fortunately the corrie was clear of mist a t

PROC. GEOL. Assoc., VOL. XXVI. PLATE 13

[PllOto by R. LUII71, 1I.M. Geological Su,,'ey.

THRUST LEIVISIAN GNEISS, CaIRE DVER LOCH MaR,

To face pa,(Je 132

EXCURSION TO THE ASSYNT DISTRICT. 133

the time, and these striking geological features were distinctlytraceable.

Several members of the party walked along the platform ofLewisian Gneiss, on the Plat Reidh, to examine some of thestream sections on the east side of the Oykell Valley. Here thesequence of Torridonian strata is inverted beneath the BenMore thrust gneiss, and the deformation of the rocks along thejunction line is very marked. The matrix of the basal Torridonconglomerate has been rendered schistose, and the pebbles havebeen elongated in the direction of the planes of schistosity. TheLewisian Gneiss has been sheared and the old structures havebeen entirely effaced. These new structures have been developedby the post-Cambrian movements.

July 9th.The main purpose of this excursion was to examine the

phenomena connected with the Moine thrust and certain typicalexposures of the plutonic mass of Cnoc na Sroine and LochBorrolan.

The Moine thrust is the most easterly of the great displace­ments produced by the post-Cambrian movements in the north­west Highlands. In the Assynt region it overlaps across allunderlying thrusts and displaced masses till the Moine Schistsrest directly on the undisturbed Cambrian rocks to the west.The party travelled by motor-cars to the Knockan Cliff, wherethis line of disruption is clearly seen. Attention was firstdirected to the structure of the ground in the undisturbed areato the west of Knockan, The geological relations of the strataon CuI Mar (2,786 ft.) closely resemble those on Quinag. Thismountain, situated to the west of the hamlet of Knockan, is com­posed of a succession of Torridon sandstones and grits restingon an uneven floor of Lewisian Gneiss. Two small outliers ofbasal Cambrian quartzites form the two highest peaks, while theeastern slope is partially covered by the same subdivision, restingunconformably on the red sandstones. The various subzones ofthe pipe-rock follow in normal order, the highest being visibleclose to the road beneath the Knockan Cliff.

The party climbed the slope and passed in succession thefucoid-beds, containing a band which has yielded fragments ofOlene/lus, the serpulite-grit with Saiterella, and a small portion ofthe basal dolomite. All these beds have not been affected bythe post-Cambrian movements. Above this horizon the normalsequence is int.errupted by a thrust which brings forward thewhite dolomite of the Eilean Dubh group (A in Plate 14.B). Thiszone is immediately truncated by the Moine thrust (B inPlate 14.B), the plane of which is clearly exposed. Above theplane, rolled out platy mylonites (C, Plate 14.B) appear, whichhave probably been derived from Lewisian rocks, and these in.

134 JOHN HORNE,

turn are overlain by mylonised Moine Schists (D, Plate I4.B). Atthe southern end of the cliff the Moine thrust has overlapped thewhite dolomite, and the rocks above that plane rest directly onthe undisturbed Cambrian dolomite. Here there appears to be aconformable passage upwards from the Cambrian rocks to theeastern schists, but this appearance is entirely deceptive. Forwhen the outcrop of this line of disruption is followed eastwardstowards Am Pollan, bed after bed of the Cambrian dolomitesand limestones, and even isolated patches of materials lyingabove the Ben More thrust-plane, rise from underneath it.

The excursionists walked eastwards from the Knockan Clifffor about a mile to see some of the evidence which proves thiscomplete discordance. They saw how the mylonites and over­lying granulitic schists of the Moine Series swing round with aneasterly strike while the beds of Cambrian dolomite and lime­stone are in turn overlapped, the strike of the latter being N.N.E.and S.S.W. Farther east they walked on the plane of the thrustwhere a streamlet has been deflected along its outcrop, and sawhow the dolomites pass below the mylonites. The demonstrationhere is complete.

The afternoon was spent in examining various exposures ofthe plutonic mass of Cnoc na Sroine, Loch Borrolan and Allt a'Mhuilinn, The party rejoined the cars at the township ofKnockan and drove to the' escarpment formed by the intrusivemass opposite the Ledmore River. The higher portion of themass round Cnoc na Sroine consists of granite or quartz-syenitein which ferromagnesian constituents are poorly developed.Two felspars are present, viz., orthoclase and albite. Lower downthe slope the quartz disappears, and on the plain skirting theescarpment at Ledmore basic modifications are met with. Speci­mens were collected of the type to be found in the LedmoreRiver, which has been termed by Dr. Teall a melanite­syenite, or melanite-syenite verging on borolanite. To thisvariety Dr. Shand has given the name Ledmorite, as it differs insome respects from the true borolanites, the essential constitu­ents being orthoclase, melanite, pyroxene, biotite, apatite. NearAultnacealgach Hotel the less quartzose nordmarkite type of theintrusion was seen.

Special attention was directed to Dr. Teall's typical borolanitelocality in Allt a' Mhuilinn and in the crags to the east of thatstream. Here the dominant constituents are orthoclase andmelanite together with plagioclase, an alteration product afternepheline, and biotite in smaller proportion. The peculiarspherical or ellipsoidal white patches in the borolanite attractedmuch attention, as Dr. Teall bad compared them to the pseudo­leucites found in the leucite-syenites of Magnet Cove, Arkansas.These white patches are aggregates composed chiefly of ortho­clase and an alteration product after nepheline.

PROC. GEOL. Assoc. VOL. XXVI. PLATE 14.

[Photo by R. Lou», H.M. Gcologhal Survey.

A.-THRUST LEWISIAN GNEISS, GLEl\'COUL

[Ptroto by R. Lums, H.M. Geologic-a! Strruey,

B.-THE MOINE THRUST-PLANE, THE KNOCKAN CLIFF.

To faa page 134·

EXCURSION TO THE ASSYNT DISTRICT. 135

Before returning to Inchnadamff the party visited the exposureof nepheline-syenite at the base of the north-west slope of Cnocna Sroine, and they hammered the marble near Ledbeg. Refer­ence was made to the contact alteration of the Cambrian dolo­mite by this plutonic mass and its apophyses, and to tbe dis­tribution of the igneous sills in the Assynt region, some ofwhich had been observed in the course of the previous excursions.

July 10th.

The work laid out for this day was comparatively light, inorder to leave sufficient time to make preparations for departureearly on the following morning. The excursionists left bymotor-cars for a point near Loch Awe, about four miles southfrom Inchnadamff Hotel. The object of the excursion was toexamine outliers of thrust materials (KlipjJen) above the BenMore thrust-plane, which now form the hills Beinn an Fhuarainand Beinn nan Cnaimhseag on the east side of the valley.

The more southernly outlier on Beinn an Fhuarain measuresabout a mile and a-half from north to south. It is composedmainly of Torridon Sandstone with a core of Lewisian Gneissand Cambrian quartzites resting unconformably on both. Allthese displaced materials rest on Cambrian dolomites andlimestones. We climbed the south-west slope of the hill to thecrest of the ridge and noted the exposures of dolomite beneaththe plane of thrust. We hammered the crushed and shatteredTorridon grits above the plane, and examined the small coreof Lewisian Gneiss with a basic dyke on the western face ofthe hill. Attention was next directed to the inversion of theCambrian quartzites on the south-west declivity and to theirline of contact with the gneiss and red sandstone.

We walked northwards along the ridge to Allt nan Uamh andsaw the outcrops of Cambrian dolomite beneath the Torridon Sand­stone. The same relationship is visible on Beinn nan Cnaimh­seag, These outliers are situated from two to three miles westof the main outcrop of the Ben More thrust, which lies to theeast of the Breabag watershed. They point not only to thefolding of the plane, but to extensive denudation of the materialsabove that line of displacement.

DESCRIPTION OF THE PLATES.

PLATE 12.-Quinag seen from the north-east in the undisturbed areawest of the post-Cambrian displacements-a mountain composed mainly ofTorridon Sandstone, capped by Cambrian quartzite, and resting on anuneven surface of Lewisian Gneiss. The ridge to right of the greatcorrie is Sail Ghorm, that to left of the corrie is Sail Gharbh. The pre­Torridonian hill of Lewisian Gneiss is seen on the right in middle distance,on the slope of Sail Ghorm and near the entrance to the corrie,

PLATE 13.-Coire Dubh Loch Mor, Ben More, Assynt, showing the

136 R. H. CHANDLER AND A. L. LEACH, EXCURSION TO WELL HILL.

great mass of thrust Lewisian Gneiss above the Ben More thrust-plane,with remnants of Cambrian quartzite on the crest of the ridge. The hillsin the distance to right are composed of the Eastern Schists.

PLATE I4.A.-Thrust Lewisian Gneiss above the Glencoul thrust-plane.The characteristic contour of the Lewisian rocks in the undisturbed area tothe west of the post-Cambrian displacements is here reproduced in the thrustmass behind Glencoul cottage. The hill in the distance to right is the Stackof Glencoul, composed of Eastern Schists above the Moine thrust-plane.

PLATE I4.B.-Outcrop of the Moine thrust-plane 011 the Knockan Cliff.Mylonised rocks lie above the plane of disruption, the position of which isindicated by the arrow. Beneath the plane occurs a zone of white Cambriandolomite brought forward by a minor thrust. The lower slope is formed ofundisturbed Cambrian strata (serpulite-grit and fucoid-beds with O/end/us).

REFERENCES.

Geological Survey Map, Sheets 101, 107.Bartholomew's ~-in. to I mile map, Scotland. Sheet 24.1907. I, The Geological Structure of the North-West Highlands of Scotland."

Mem. Geo]. Survey.1914. II Guide to the Geological Model of the Assynt Mountains." Mem.

Geo/. Survey.

REPORT OF AN EXCURSION TO WELL HILL.

SEPTEMBER 5TH, 1914.

By R. H. CHANDLER and A. L. LEACH, F.G.S.,Directors of lite Excursion.

THE Excursion was .devoted to the physiographical aspect of thegeology of the district, and to the examination of the Eoceneoutliers and Drift gravels upon the ridge between the valleys ofthe Cray and of the Darent, At Well Hill, 610 O.D., where alarge outlier of Thanet Sand and Woolwich Beds controls thescenery and cultivation of the ridge, the Eocene beds are cappedby Drift composed of large subangular flints, intermixed withTertiary flint pebbles and containing a small proportion of LowerGreensand chert, rare quartzites and material of Wealdenorigin. Flints, claimed as Eoliths, have been found in it.

On the slopes of the hill the Directors have found someferruginous sandstones with casts of fossils (indeterminable),apparently derived from Lenham Beds.

On the eastern side of Well Hill a dry valley-TimberdenBottom-falls very sharply towards the Darent, from which, inits upper part, it is separated by Meenfold Hill, a narrow and verysteep-sided ridge of Chalk capped by Clay-with-flints. From theeastern slope of this ridge the wide-mouthed" gorge," by whichthe Darent traverses the North Downs, may be seen, with theVale of Holmesdale and the range of Lower Greensand hillsbounding the prospect towards the south.