148 D. C. DAVIES ON COAL SEAMS IN 'THE PERMIAN.

mining operations since the present maps were issued have fur­nished information on this point, which was wanting before, andhave rendered the changes indicated necessary.

Since the above paper was read, I have twice been over thedistrict in question with Mr. J. Dickenson, F.G.S., Inspector ofMines, who by the occurrence of Ooal Measures above the " redground," which he, in common with others, had taken to belong toPermian strata, has been led to include the whole series in theCoal Measures proper. The red beds correspond, in his estimation,to similar beds which divide the Upper from the Lower OoalMeasures in North Staffordshire. If this be so, then the greaterpart of the red beds of the kingdom which hitherto have beenmapped as Permian must now be included in the Ooal Measures.There still remains the great thinning out of beds, which I havedescribed as existing between the base of the red ground and theOoal Measures from Hafod-y-bwch to Sweeney and Drill, andwhich may be gradually traced nearly all the way between theextreme points. However, I prefer that the Paper should appearas it was originally read. It will possibly excite discussion out ofwhich the true position of the beds described will be elucidated.Much depends upon the identity of the" red beds" of Ifton andof Sweeney, and that identity will be ascertained by collieryoperations in which I am now engaged.

2. ON A WELL SECTION AT FINCHLEY.

By OALEB EVANS, ESQ., F.G.S.

The various deep wells that have been constructed in and around

the metropolis enable the Geologist to form a general idea of thestratification of the London Tertiary District, although thereare many minor details which, without clear and continuous sections,cannot be determined. The valuable work of Mr. Whitaker, "Onthe Geology of the London Basin," in which 488 of these wellsections more or less perfect have been published, has added con­siderably to our knowledge on this subject. The majority ofthese well sections have been recorded from within or in theimmediate neighbourhood of the Metropolis, and there are many

O. EVANS ON A SECTION AT F INOHLEY. 149

parts of the environs of London at a considerable distance fromany of these published sections, and any new sections formed inthese intermediat e areas are, therefore, both int eresting to th eGeologist and valuable for practical purposes, more especially asthe deposits, both above and below the London Clay, in NorthMiddlesex vary greatly in mineral characte r.

In th e summer of th e present year (1872), the Eas t Barn et Gasand Water Company commenced the const ruction of a deep wellat the north end of Finchley, but I was not aware of this under-

. tak ing until it had been some t ime in progress, and I was, there­fore, una ble myself to note the higher deposits passed through, andI have only been able occasionally to watch the operations. Underth ese circumstances when the Qorers bad penetrated to the Chalk,I applied to the Water Company for information, and throughth e kindness of J. Stokoe, Esq., the Resident Engineer, I havebeen furni shed with th e following details of the strata passedth rough in this well.

THE FINCHLEY NEW WATER WORKS.(WELL EIGHT F EET DIAMETER.)

I.-Clay ...2.-Sand with Wat er3.-Blue Clay with Chalk F lints4.--Dark Clay, and Black P ebbles, And Flints5.-Sand and Gravel, with Water6.-Blue Clay ...7.-Clay-stones with Shells8.-Coloured Clay9.- Gravel with Water10.-Mottled Clayn.-Black Pebbles with a lit tle W aterl 2.-Dark Sand with a little WaterFliut s and Chalk.

F eet.2046

1213

1692

2132

257

The well was sunk to bed No.9, and from that depth a boringwas continued to the Chalk, which at the end of October last hadbeen penet rated to a depth of 90 feet, and the boring was to becontinued to a greater depth ."

The level of the surface of th e country in the neighbourhood ofthis well is about 290 feet above the Ordnance Datum, the well

llt I have learnt from a fri end th at on th e 4th Dec., 1872, the borin g had reached500 feet from th e sur face, and th e work was st ill in progress in Oct., 1873, atwhich time a depth of above 600 feet had been reached,

150 C. EVANS ON A SECTION AT FINCHLEY.

having been sunk from the top of the plateau that extends fromFinchley to Whetstone. Of the strata traversed by this wellsection the five highest beds belong to the deposits of the GlacialEpoch, which occupy the upper portion of the Finchleyplateau. Theydiffer, however, slightly in character from the deposits exposed inthe section by the Finchley Railway Station, which were describedby Mr. H. Walker, F.G.S., in his paper, read before this Associa­tion in December of last year." The variable character ofdeposits derived from the action of glaciers and icebergs is seenin the sections around Finchley, Bendon, and Whetstone, thematerials appearing in some spots to have been derived from theBagshot Saud and London Clay and in other cases from moredistant formations.

The Clay (No.1), extending from the surface to a depth of 20feet, is greenish brown in colour, at least in the upper part, and itresembles in appearance the clay which was exposed at East End,Finchley, at the time when the railway cuttings were formed atthat spot. A similar clay is seen in the Manor brickfields, whereit contains drifted fossils and blocks.

The bed of Sand (No.2) is doubtfully represented in the rail­way sections, but sands occur at Hendon and gravel at Whetstoneconsiderably above the base of the Glacial deposits.

The beds (Nos. 3 and 4) described as "Blue Clay with ChalkFlints" and" Dark Clay with Black Pebbles and Flints" repre­sent probably the clays with masses of chalk seen in the lower partof the section at the Finchley Railway Station and, although nomention is made by Mr. Stokoe of chalk as one of the materialscontained in these clays at the well section, I think it highlyprobable that that rock is present in addition to the "ChalkFlints" and pebbles.

The bed of Sand and Gravel (No.5) is the lowest of the Glacialdeposits in the neighbourhood of Finchley and is of considerableimportance, as it forms the principal water-bearing deposit of thedistrict around Hendon, Finchley, and Whetstone, and the springswhich issue from the lower portion of this bed serve as useful in­dications of the junction of the Glacial deposits with the LondonClay below.

The straturn (No.6), described as "Blue Clay," presents for the

I« Proe, Geol, Assoe., vol, ii., p. 289.

C. EVANS ON A SECTION AT FINCHLEY. 151

greater portion of the thickness of 169 feet the ordinary charactersof the London Clay, consisting of a stiff clay with bands of septaria.The fact that this clay is not more than 169 feet thick at Finchleyindicates that the lower portion only of the deposit now thereremains, and that more than 200 feet of the stratum had beenremoved by denudation prior to the deposition of the Glacial beds.

Fossils do not appear to be very numerous in the London Clayof this well, but I was informed by one of the workmen that at adepth of about 130 feet from the surface there was a layer of theclay containing many fragments of Pentacrinus, a specimen ofwhich he showed to me. This fact is of considerable interest, sincethe depth above mentioned would place this layer at about 100 feetfrom the bottom of the Lond014 Clay, and it is at about the sameposition in the clay that this fossil occurs so abundantly at Gatti'sIce Well in the Caledonian Road, and at the Gas Works atBattersca as described by Mr. Coombs.*

Although no change of character is recorded by Mr. Stokoethroughout the 169 feet of " Blue Clay," the lower portion of thebed (in which the excavation was proceeding at the time' of myfirst visit) becomes coarser and more mixed with green sand, andthis portion also contained many vegetable fragments and slighttraces of wood bored by the Teredo, and occasionally isolatedpebbles.

The most remarkable deposit in this portion of the section is aband of compact lignite, about one inch thick. Although noanimal remains have been met with in this sandy clay, there islittle, if any, indication of freshwater conditions, the stiff clayabove and the stone below being both. clearly marine; moreover,this lignite shows no evidence of having been formed from driftedwood, and it is difficult to imagine under what conditions thislayer could have been deposited.

In most of the sections in the neighbourhood of London, in whichthe lower part of the London Clay is exposed, a thin group of bedsis present, which has been termed by Mr. Prestwich "The Base­ment Bed of the London Clay." In most localities the principalstratum of the Basement Bed consists of a layer of rounded flintpebbles, and in these instances the bed is devoid of organic remains,with the exception of the teeth of Lamna ; but in other spots,

>If< Proc, Geo!. Assoc., vol iii., p. 33.

152 C. EVANS ON A SECTION AT FINCHLEY.

where the pebbles are not so abundant, some of the layers arehighly fossiliferous. This is especially the case in the neighbour­hood of Reading, and at Hedgerley, near Slough.

A group of fossils similar to those met with at Reading andHedgerley, is also recorded from Batchworth Heath south ofRickmansworth, from Bnshey near Watford and from the well atthe Lower Heath, Hampstead.

The bed (No.7) of " Clay-stones with Shells" is evidently therepresentative of the Basement Bed, in which group the sandyclay immediately above and the band of lignite should perhapsalso be included.

"The stone varies slightly in mineral character, some portionsapproaching to a crystalline limestone, and others consisting of an

argillaceous limestone. Occasionally the stone resembles septariaand is traversed by cracks filled with veinstono,

The fossils are chiefly found in one or more bands in the form ofsharply defined casts and impressions, which are frequently suffi­ciently perfect fo admit of identification. The most abundant shellis a Cypl'ina closely resembling the C. planata of the LondonClay. This species is not recorded by Mr. Whitalter from theBasement Bed, but an undescribed species of this genus and alsoC. M01'risii are mentioned from several localities in the Londondistrict. C. planata is also very abundant in the Bognor Beds ofthe Isle of Wight and at Portsmouth. It is also a very commonfossil in the Lower Tertiary beds of East Kent.

Another common fossil of this stratum at Finchley is the so­called Panopcea intermedia (which in some of its characters ap­proaches to the extinct genus Myacites). This shell is but rarelyfound in the London Clay in the neighbourhood of the metropolis,but is more abundant in Berkshire, Hampshire, and at Bognor, andit is present in many of the sections of the Basement Bed.

Another species, abundant in the Finchley shell-rock, CardiumLaytoni, prevails in the Lower Tertiaries, but has not been obtainedfrom the London Clay. It is common in the Basement Bed atHedgerley. Aporrhais Sowerbyi, another Finchley fossil, is a shellalso characteristic of the Basement Bed. Natica labellata, a fossilwhich ranges throughout the whole of the Eocene strata, is alsocommon, and a fragmentary specimen perhaps indicates the pre­sence of Natica subdepressa,

In addition to the above the Finchley stone contains two or

C. EVANS ON A SECTION AT FINCHLEY. 153

three species of Cytherea, some probably undescribed, also a shellresembling a Sanquinolaria or Glycimeris, and some small casts ofunivalves. Ditrupa plana, a fossil which is present in great num­bers at Hedgerley and Reading, has not been found at Finchley.

The greater number of the sheUs of the Lamellibranchiata occuras single valves, and the animals did not perhaps live exactly atthe spot where their remains are now found, but as the impressionsare in general sharp and unworn, the shells had probably not beendrifted from any great distance. In a few instances Panopcea oc­curred between the layers of shells in an oblique position approach­ing to that in which the animal was placed when living. Thewhole fauna of this shell bed indicates a depth of about 70 fathoms,and a temperate climate.

The strata, that intervene in tbe Finchley Well between thefossiliferous Basement Bed and the Chalk, are the representativesof the Woolwich and Reading Series and perhaps of the ThanetSands. The Woolwich and Reading Series is represented inHampshire by a thick deposit of red mottled clay, and in theneighbourhood of Reading, and generally to the west and north ofLondon, by mottled clay associated with layers of sand and pebbles,

while in West Kent estuarine and freshwater conditions prevailed,and in East Kent the series is represented by marine sands.sThe Thanet Beds (fossiliferous in East Kent) form in West Kentthick beds of sand, which thin out rapidly to the west and north.

A comparison of the Finchley section with the published wellsections, nearest to that spot, shows that the bed (No.8) ofcoloured clay extends over a considerable area, but appears -tothin out to the north, since it is 21 feet thick at Finchley andabout the same thickness at Colney Hatch, but the correspondingbed at New Barnet to the northward is 16 feet thick, and atHampstead to the south it is 40 feet in thickness,

The bed (No. 11) of flint pebhles in sand is 25 feet thick; thisis an unusual thickness for this pebble bed in North Middlesex, asis shown by other well sections. At Colney Hatch the bed of pebblesis 6 feet thick, and at The Hyde near Hendon not more than2 feet thick, with 9 feet of mottled clay above and 12 feet ofmottled clay below it. At Harrow 5 feet of pebbles occur beneath17 feet of mottled clay. At Hampstead the presence of pebble

* See Proc. Geol, Assoc., vol. ii. p. 67.

154 C. EVANS ON A SECTION AT FINCHLEY.

beds is doubtful, but at Barnet, as at Finchley, there are two pebblebeds separated by a thin band of mottled clay, but at the formerplace the higher bed is only 1 foot, and the lower 7 feet thick.

The great thickness of the pebbles at Finchley appears to havebeen formed at the expense of the sand below (the doubtfulrepresentative of the Thanet Sands), which is there 7 feet thick,while at Colney Hatch it is 25 feet, at The Hyde 11 feet, andat New Barnet 13 feet in thickness.

This sand (No. 12) is the lowest of the Tertiary strata atFinchley, but I was informed by one of the well-sinkers that a bedof flints about two feet thick intervened between it and the Chalk j

this is probably the well-known deposit of "Green-coated Flints."With regard to the Chalk little could be learnt, owing to the

wet and disintegrated condition in which the material was broughtto the surface. Indications were seen of several bands of flintnodules and of a band of tabular flints.

The foregoing deposits do not present any features of greatnovelty j but I have thought that the details of a Tertiary well­section at a considerable distance from any already published areof sufficient interest to be recorded in the "Proceedings of theGeologists' Association."