S. SHARP ON THE GEOLOGY OF NORTHAMPTONSHIRE. 243

" Sketch of a Geological Map of Victoria j" from Henry Wood­ward, Esq., F.R.S., F.G.S., F.Z.S., Pres. G. A.

" Further Remarks on the Relationship of the Xiphosura to theEurypterida and to the Trilobita and Arachnida," by Henry Wood­ward, F.R.S., F.GS , F.Z.S., Pres. G. A. j from the Author.

" On the Denudations of Norfolk," by the Rev. O. Fisher, M.A.,F.G.S. j from the Author.

" The Coprolite Pits of Cambridgeshire," by the Rev. O. Fisher,M.A., F.G.S. j from the Author.

" Descriptive Guide to the Fossil Collection in the Museum ofthe Leeds Philosophical and Literary Society j" from W. Whitaker,Esq., B.A., F.G.S.

" On the Geological Position and Features of the Coal andIronstone Bearing Strata of the West of Scotland," by JamesGeikie, F.R.S.E., Edinburgh j from W. Whitaker, Esq., B.A.,F.G.S.

" Sketch ofthe Geology of the Neighbourhood of Banbury," byThomas Beesley, F.C.S. j from the Author.

The following were elected Members of the Association :­

Arthur M. Butt, Esq. j Rev. Robert Dixon, M.A, LL.B.F.G.S.; Frederick Rovenden, Esq., F.R.M.S.; Thomas JessonEsq., B.A., F.Z.S.; Edward Powell, Esq. j and William Priest­land, Esq.

The following Papers were read:-

1. SKETCH OF THE GEOLOGY OF NORTHAMPTONSHIRE.

By SAMUEL SHARP, ESQ., F.S.A., F.G.S.

The county of Northampton possesses many points of greatgeological interest. It is situated about midway upon the greatbelt of Oolitic and Liasic formations, which traverses England fromthe coast of Dorsetshire on the south, to the northern shores ofYorkshire on the' north-east. Taking a general section of thecounty, we find that the Lias forms the great basal formation, andhas an aggregate thickness of about 850 feet, consisting of from150 to 200 feet of the Upper Lias, about 30 feet of the MiddleLias, or Marlstone, and something like 650 feet of the Lower Lias.The clay of the Upper Lias is largely worked for brick-making;but the bricks of Northamptonshire are not remarkable either forquality of material or for colour, either when new or weathered.

244 S. IlHARP ON THE GEOLOGY OF NORTHAMPTONSHIRE.

Thi s clay abounds with palreontological remains ; such as those oflarge I chthyosauri and T eleosauri , Ammon ites and B elmnites,Gryphcea, Ostrea, and other bivalves, &c. It has also yielded aunique crustacean, a clawless lobster (like a large prawn), P eneusSharpii, Woodward.

Th e Middle Lias, or Marlstone, is an abundant water-bearingformation, and from thi s, by a well 168 feet deep, th e W ater Com­pany of Northampton furnishes to the town a copious supply ofpure and not hard water. It is characterized by the presence ofRhynchonella tetraedra , Sow., very large P ecten cequivalois , Sow., &c.

Above the Lias, repose th e peculiar and interesting InferiorOolite beds of the" Nortbampton Sand" (so called by tb e Govern­ment Survey), having an aggr egate thickness of about 80 feet.These beds have been classified into two divisions-the lower divi­sion, of about 60 feet in thickness, being that which yields anabundance of iron ore, for wbich Northamptonshire bas become sofamous. 'Ihis ore has now (1873) been worked for upwards oftwenty years, and during that tim e a quantity exceeding a millionand a half tons of pig-iron has been produced. At the presenttime, about 20,000 tons per week of the ore are being excavated,yielding on an average nearly 40 per cent . of pig-iron. One-fourthof this ore is smelt ed in the distri ct, but the gr eater portion is sentoff for admixture with other ores to Merthyr Tydvill, in SouthWales, to tbe Tees, and to Staffordshire. It is remarkable thatin th e Roman tim es-probably in the third and fourth centuries­Northamptonshire was a great iron-producing district; but it sresources in this direction remained dormant until about the year1850, when the discovery of the gre at value of these iron-bearingbeds was again made. The beds of th e lower division, dependingupon local favourable conditions , yield easily-worked, durable, andrichly-coloured building stone. They are highly fossiliferous, andhave yielded many species not known in other districts : amongthese are a star fish-Stellaster Sharpii, Wright j and the bivalves-Lima Sharpiana, Etheridge; L. Dustonensis, Eth.; L . del­toidea, Eth.; L. Rodburgensis, Lyc ett, M.S.; and a large Limaallied to L. Grandis, Romer j Trigonia Sharpiana, Lycett; andoth ers not yet described; a t ooth and pelvic bone of Jl.fegalosaurus, adorsal scute of an undescribed species of Teleosaurus, &c.

The upper division of tho " Northampton Sand" consists of anearly white siliceous sand, frequently intercalated with clay (worked

Fig l.-8ection from Lincolnshire at Stamford throughNorthamptonshire into Huntingdonshire, nearly on the line of the GreatNorthRoad.

Horizontal Scale-One inch to a mile. Vertical Bcale-AbO'Ut OM-tlmth of an inch to 30 feet.Survey Bench-marka.

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1.- 0xforol C1ny.2.- Cclrnl no:l ,,11.3.- Cln,·. "·l. - I .i ll ip KtOl1(t. Jf. Grout Oolite.l'i, - UPIUl l' Jo;...t unr-lno .

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246 S. SHARP ON THE GEOLOGY OF NORTHAMPTONSHIRE.

for terra cotta in the neighbourhood of Stamford); and in placesexhibits, in situ, a plant bed, with horizontal layers of super-growth,overlying a bed (running to 18 inches) of vertical root perforations.Some geologists, however, have considered that the latter are notroot perforations, but are the traces of equisetal plants. Some­times this white sand is found sufficiently indurated to constitute agood building stone. Many important buildings, including theNorthamptonshire General Infirmary, were built during the lastcentury of this stone.

The upper division and the upper part of the lower division ofthe Northampton Sand, as indicated by the presence of plant re­mains, much drifted wood, certain bivalve and univalve fossils, andby the frequent occurrence of ripple-marked surfaces, had partly anestuarine and partly a littoral origin. The upper division has beentermed by the most recent geologists, in contradistinction to higherbeds in the district having similar characteristics, the " LowerEstuarine" series.

The Lower Estuarine series, in the Northern and Eastern partsof the County, is surmounted by a very important formation, madeup of several and very various beds, chiefly of oolitic limestone,and which, traversing Rutland and passing into Lincolnshire, whereit has attained its greatest development (a thickness of about 200feet), has hence been called the" Lincolnshire Limestone." Thefossiliferous contents of these beds demonstrate that they are alsoInferior Oolite; and other reasons there are for concluding that theyare the uppermost group of the Inferior Oolite series in this district.

At the base of the" Lincolnshire Limestone," occurs, at Colly­weston and Easton, a thin bed of a calcareo-arenaceous character,which, upon exposure to frost, readily splits up into slates, not inthe planes of cleavage as in the case of Welsh or Westmorelandslates, but in the planes of its finely laminated stratification. Thisslate is extensively used in the district, having, in ancient times,formed the prevalent roofing material of the locality, and' has beenemployed by Sir G. Gilbert Scott, the celebrated architect, forthe roof of the new chapel of St. John's College, Oambridge, asalso for that of the rebuilt nave and aisles of St. Sepulchre'sOhurch, Northampton, and other important erections. The pro­duction of these slates forms the staple trade of the two importantvillages named above, and furnishes employment to a considerableindustrial population. These slate beds are probably a local varia­tion only. Among the more remarkable fossils found in them are-

Fig. 2.-Sections Illustrating the Relations of the LincolnshireLimestone to the Northamptonshire Oolite.

[Reprintedfrom tke " Q UAUTERLY JOURNAL OF THE GEOLOGICAL 80CIETY," bypermission of the Cbunci1.J

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248 8 . 8HARP ON THE GE OI.OGY OF NORTHA~IPTONSHIRE.

" beautiful and previously unkn own winged univalve, termedPterocera Bentleu i, after a gentleman well known in th e district;8 crustacean of the genus P seudophyllia (a small lobster}; and aunique star fish, found by th e writer-Astropecten Cotteswoldice,val'. S tamfo rdensis, Wright.

Of .the limestones above this so-called Collyweston Slate, th elower beds are, for the most part, marly and soft, and occasionallysupply a pure cream-white stone, well adapted and much used forinterior domestic work, and for carved work in churches. High erbeds yield good rough durable building stone, and are traversed bya very shelly and partially crystalline bed, the stone of which,taking a good polish, has been termed the" Stamford Marble," andis very ornamental for chimney-pieces. The whole of these bedsare quarried extensively for lime-burning, the lime produced beingof excellent quality.

Passing upwards from these marly beds of limestone, our atten­ti on is drawn to one of the most important building stones in th ekingdom-the widely known " Ketton Freestone"; th e equivalentstone in Northamptonshire being the " Weldon Stone," quarried atthe place of that name. Both Ketton itself and Casterton, wherea very fine example of th e same stone is quarried, are only ju stwithout the confines of the county, in Ru tland, which abuts on th emid portion of the north ern limit of the Northern Division ofNorthamptonshire . Thi s stone is of that peculiar grain fromwhich th e term "oolite" (or roe-stone, or egg stone) is derived.It is composed enti rely of small egg-shaped grains, embedded in acalcareous matrix. A polished section of the stone generally showsth at each of these ova-shaped grains ha s a minute nucleus (eithersiliceous or consisting of a shell fragment) enclosed in concentriccalcareous films. It is a stone very easily work ed, is of a goodcream colour , and very durable, hardening under at mospheric ex­posure. St. Dunstan's Church, in Fl eet Street, London, several ofthe colleges at Cambridge, and many churches in th e district, arebuilt of it. It is not very fossiliferous, but has yielded th e charac­teristic forms-Terebratula fimbria, Sow.; Rhynchonella spinosa,Schlott; R: Crossii, Walker; Pholadomyafidicula, Sow.; P . Zieteuii,Ag.; Trigonia hemiephcerica, Lycett; Pterocera Bentleyi, Mol'. andLye. ; Natica Leckhamptonensis, Lycett; Cidarie Foui leri, Wright;C. fVdghtii, Desor.; numerous fine corals; Aroides Stu tterdi,Carruth., and other plants , &c.

Classing with, but higher in the geological scale of the county

B. SHARP ON THE GEOLOGY OF NORTHAMPTONSHIRE. 249

than the" Ketton Freestone," is a very shelly kind of stone called"Barnack Rag." This stone was quarried at Barnack even sofar back as the time of the Romans, and has proved to be of a verydurable nature, many of the churches and several of the cathedralsof the district having been built of it. .Some beds of this stoneseem to be composed almost entirely of shells agglutinated togetherby a calcareous cement. The Barnack quarries have been ex­hausted for nearly 400 years, and at this time the stone is notworked in any other locality.

Above these several beds of the" Lincolnshire Oolite" lies un­conformably a series of argillaceous or clay beds, having at theirbase a ferruginous band. These form, in this district, the lowestbeds of the Great Oolite. The ferruginous baud is rich in fossilsof this geological division. The clays themselves have yielded, inmore than one locality, remains of the gigantic crocodilian saurianthe Cetiosaurus, also two varieties of a bivalve peculiar to this dis­trict-Nerera Ibbotsoni, Morris. The presence of the brackishbivalve Cyrena, of drifted wood, of a plant bed, and of similarcharacteristics to those of the" Upper Division" of the" North­ampton Sand," indicate that these clays are also of an estuarineorigin, and they have therefore been termed the" Upper Estuarine"series. They are worked for brick-making.

Above these clays, is a series of limestone beds, some zones ofwhich are very fossiliferous, and yield a fine stone for chimney­pieces, hearths, &c. They burn into a good lime. A shelly andsub-crystalline bed at Alwalton, near Peterborough, takes a goodpolish, and has been called" Alwalton Marble." The detached slendercolumns of the beautiful Early English west front of PeterboroughOathedral were composed of this marble; but, they having becomedecomposed from atmospheric action, another material has been sub­stituted. In some localities, these beds abound with the remainsof a small lobster, a variety of Elvymaelegans, Oppel, and generallywith the teeth, scales, and spines of several species of fish, of thegenera Hybodus, Lepidotus, Pycnodus, and Strophodus. From thisbed at Blisworth also have been obtained two examples of a fishnot found elsewhere-Pholidophorus Flesheri, Agassiz. From thebed at Kingsthorpe has been obtained a fine cone of a pandana­ceous plant, allied to the " Screwpines " of Norfolk Island, in thePacific Ocean. This plant is not only of a new species, but of 8

new genus, and has been named by Mr. Carruthers, F.R.S., head

250 S. SHARP ON THE GEOLOGY OF NORTHA~IPTONSHlRE.

of the Botanical Department, British Museum, Kaidacarpum Ooliti­cum. Fossil fruit of a plant (Carpolithes) is not uncommon in thesame bed. In the neighbourhood of Oundle also, has been foundan elegant little starfish, having five attenuated and tortuous rays,which has been named Ophiurella Griesbaclui, after the late Rev.A. W. Griesbach, an eminent geologist, who formerly lived at Wol­laston, in this county.

Surmounting this limestone, occurs occasionally a variegatedclay bed, characterised by an abundance of the small Ostrea sub­ruqulosa, Morris & Lycett. This takes the place of the BradfordClay of the West of England. Above this is the Forest Marble,and over a wider area the, Cornbrash, both of which aboundin beautifully preserved fossils: over all, is the Oxford Clay,yielding numerous ammonities, belemnites, large oysters, saurians(including the huge Pliosaurus), masses of wood converted intojet, &c.

The foregoing represent the range of Secondary formationsin the county; but the high lands are frequently capped with athick bed of the Boulder Clay and Glacial gravels, contain­ing fragments from nearly the whole series of Primary andSecondary Rocks :-Liassic, Kimmeridge Clay, and Oxford Clayfossils being frequently found beautifully preserved in masses ofSeptaria. The valley gravels abound with large tusks and teethof Elephas antiquus, E. prim1genius, and an Elephas of an inter­mediate species; and teeth of Rhinoceros tichorhinus, bones ofHippoptamus major, teeth of Equus caballus and E. fossilis, thecore of a horn and part of the frontal bone of Bison priscus, anda head of Bos primigenius, have also been found. The peaty fluvi­atile bed above the gravel contains at its base numerous remainsof the aboriginal small ox Bos longifrons, red deer, horse, wildboar, with human skulls, &c.

As to the geological geography of the county, as has beenobserved, the Lias forms the foundation, so to speak, of the wholedistrict, but is exposed in the valleys. In the North Westerndistricts, the Lower Lias is the prevailing sub-surface formation.The ironstone occurs at its greatest thickness in the neighbourhoodof Northampton, or in the mid-section of the county. It isquarried largely at Duston, Blisworth, Gayton, and Stow NineChurches, to the west of Northampton; and at Cogenhoe, Welling­borough, Finedon, Woodford, Cranford, Glendon, and other places,

S. SHARP ON THE GEOLOGY OF NORTHAMPTONSIlIRE. 251

east and north-east of Northampton. It ranges in the latter sec­tion as far as Stamford, where it is now being quarried upon theestate of the Marquis of Exeter. Smelting furnaces have beenerected at Heyford, Wellingborough, Finedon, Islip, near North­ampton, and elsewhere. The ironstone thins out in the southernpart of the county, and disappears, and the iron ore of the ferru­ginous beds of the Middle Lias, or Marlstone, in the neighbourhoodof Banbury, commercially takes its place.

The" Lincolnshire Limestone" is the characteristic stone of theNorthern Division of the county, north of the river Nene; but itthins out near Kettering and near Maidwell, about eight miles northof Northampton, and does not recur in the Southern Division. Itsplace, for all purposes of a limestone, is taken in the middle of thecounty, and in the Southern Division, by the" Limestone" of theGreat Oolite, which generally caps the high lands. The ForestMarble, as a hard rock, only occurs in the neighbourhood ofPeterborough, and over a very limited area. The Cornbrashcrops out from under the Oxford Clay (Lased by the KellowayRock) on the southern escarpment of the Nene Valley, rangiugin from Bedfordshire at a point upon the boundary of the countynear Rnshden, and extends, by Onndle, nearly to Peterborough.In like manner, it crops out north of the Nene, near Sudborough,extending by Lowick to the Aldwinckles, and reappearing uponmany escarpments neal' Oundle, It also caps the high groundsnorth of the Addingtons and Woodford, at Islip, at Bnlwick, atUpton (near Castor), occurs at a lower level at Helpstone, and isthe surface rock over a large area to the north and north-west ofPeterborough.

The Oxford Clay overlies, and is almost conterminous withthe Corn brash, where, as stated, the latter crops out upon thesouthern escarpment of the Nene Valley, and it spreads out overa considerable area of elevated land far into Bedfordshire: con­siderable patches of it also occur in the same elevated position tothe north of the Aldwinckles, and to the north and west of Oundle ;while in the neighbourhood of Peterborough it occupies only thelow grounds, and spreads out over the great level of the Cambridge­shire and Lincolnshire fens.

Very high table land occurs about Naseby, from the water-shed ofwhich rise :-The Avon, which flowswestwards (forming the northernboundary of the county from Welford until it passes into Warwick­shire), and by Warwick and Stratford-on-Avon, into the Severn

252 B. SH ARP ON THE GEOL OGY OF NORTHAMPTONBHIllE.

and the Bristol Channel; the W eHand, which takes an east erlydirection, and passing by Stamford to Spalding , flows into th eBoston Deeps, forming the northern boundary in that dir ection, toa point near Crowland; and the Nene, which flows southward, untilat Northampton it forms a conflux with its western branch, andturn s easterly, passing by P eterborough and Wisheach, also to theBoston Deeps. The Nene forms th e southern boundary of thecounty between Elton and Peterborough . In the Southern Di visionof th e county, rise th e south ern branch of the Nene; and nearTowcester, the Ouse, which passing through Buckinghamshire,Bedfordshire, Huntingdonshire , Cambridgeshire, falls into theWash at Lynn in Norfolk j and near Weedon, th e Cherwell, atributary of the Thames . There are many minor streams tributaryto these the important rivers of Northamptonshire, which is thusint ersected by numerous valleys, upon the escarpment of which,owing to the prevalent alternation..of pervious and impervious beds,occur the numerous spring s of pure water for which the county hasa reputation.

It will be seen from the foregoing sketch that th e county is for­tunat e in it s mineral wealth-in its iron , its richly-colour ed ferru­ginous and its more excellent oolitic building-stones ; its lime, itsCollyweston roofing-slates, its brick-clays, its sand, and its gravel.More than a quarter of a century ago, some £ 30,000 was expendedin sinking a shaft at Kingsthorpe,in a fruitl ess search for coal.Recently, the question of the presence of coal in the county hasagain been mooted j but to geologists it is an idle question. Fromthe nature aud thickness severally of th e strata of the nearest coalfield of Warwickshire, and of th e int ervening district, it is notimpossible .that below th e present shaft at Kingsth orpe (967 feetdeep) would be found th e Trias beds to the thi ckness of 800 feet,the Permian beds 2,000 feet , and the Coal Measures (before work­able coal could be found), 750 feet: a depth in all of more th an4500 feet ; being nearly twice th at of any existing mine, andreaching far below th e point at which, with known appliances, it ispossible to extract coal. Moreover, Mr. Hull, F.R.S., Directorof the Government Geological Survey for Ireland, who, more thanany other scientific man, ha s made coal and the coal-fields hisspecial study, concludes that th e great English coal-field never didextend into Northamptonshire , and that therefore, at any depth,coal cannot be found in th e county.