4 . (KELLY's

THE GEOLOGY OF BEDFORDSHIRE.

• THE rocks of Bedfordshire have been carefully examined THE CRETACEOU3 FoRMATION.-As the Upper Oolitic by different geologists, to whose thorough and minute work beds-the Pur beck and Portland strata-are here absent, we we owe our knowledge of the geological structure of the pass at once fro~1 the thick ~o_litic _Clays to those rocks of county. The beautiful maps, coloured so as to show exactly which the Chalk 1s the most d1stmgmshed member. where each stratum reaches the surface, issued •by the The Lower Greensand.-This bed presents a complete con­ Geological Survey in 1864 and '65, were chiefly the work of trast to those last noticed, being a light buff-coloured or red­ Messrs. Hull, Whitaker, Green, llauerman and Howell, and dish-brown sand often showing false bedding and full of it is to be regretted that they are not accompanied by full fragments and doncretions of brown peroxide. of iron; it "descriptive memoirs. M_r. ~aunders, of Lut?~• has done enters the county at and Lmslade, and good work in the Chalk district, and the coprohtiC beds ha\·e passes by Little and Great Brickhill_an~ Waven~on. Planta­ been well described by Mr. Teal!. To the surface geology tions to , and FhtwiCk, const1tutmg here Mr. J. Wyatt, of , has made most valuable contri­ the well-known Woburn Sands. Fullers' earth has been dug butions, and we also owe much to Professor H. G. Seeley, at Wavendon, where the beds have a thickness of from • so Dr. J. Mitchell, and others. The general structure of the to 200 feet ; thence by Ampthill and Shefford the sands county is plainly owing to the fact of the central line bei_ng extend to , Sandy and , where they pass occupied by a broad band of clay, to the nor~h-west of whiCh out of the county. In the South, near Little Brickhill, these we have undulating ridges of limestone, while on the south­ beds are 250 feet in thickness, and they occupy a belt of east rises the chalk escarpment; thus the town of Bedford country 4 miles wide ; at Millbrook, ne~r Ampthill, the is 100 feet above the sea level, whilst is 351 feet, thickness is not more than one-tenth of th1s amount, or 25 483 feet, and Dunstable Downs 799. feet respec­ feet, the. upper portion having pro_bably been removed. by tively. As is usual, the oldest beds are found m the north­ denudatiOn · near Potton the senes IS about 100 feet th1ck, west of the county, and we shall commence with them. and is capped' by about- 35 feet of Car stone (or Quern THE OOLITES.-The lower oolitic strata do not enter the stone). At Bandy these Lower Cretaceous beds form a very county ; the well-known white·limestone whic_h we find in the picturesque escarpment on the right bank of the I vel; north-west corner is of Great Oolite age, bemg of the same between Sandy and Potton they are well expo!'led in the age as that which at Bath and elsewhere in the West of cuttin(J"s of the Cambridge and Bedford Railway: The land furnishes such excellent building stone. We can is so barren •in some parts as to produce little except trace it from Cold Brayfield by Carlton and Harrold, north­ plantations of Scotch fir; but where it is mixed wi~h clay, wards to Puddington and Farndish and eastwards along the as along the western side of the Great ~orthern_ hne, t_he {)use valley to the western suburbs of the ~wn of Bedford, result is a sandy loam of great productiveness, m wh1ch where it is seen in a stone-pit on the north s1de of the Ouse, onions, potatoes, and market produce gener~lly are grow_n towards ; it is a compact stone, got in some places with great success. Over the greater part of 1ts extent th1s for lime burning, but good sections of it are rare ; it is asso­ rock forms a range of undulating hilly ground with beautiful ciated with bands of Great Oolite Clay, which form a cold, woodland scenery. Economically the Lower Greensand is unkindly, but often well-wooded district. One or two s~all celebrated for the band of phosphatic nodules which occurs species of oyster, as Ostrea subrugulosa and 0. Sowerbyt are at the base ; this varies from 6 inches to 2 feet in thickness, -<:ommon in the fossil state. . '" and is full of water-worn fossils, including many saurian The Cornbrash.-This very continuous band of reddish and fish remains, and the rounded shapeless masses, rubbly limestone can be traced from Newton Blossomville generally termed coprolites. In the pits at Potton we see by Turvey Farm, to just west of Pavenham; here it t~rns under the surface soil about 9 feet of yellowish sands, and 11outh the outcrop having been worn back by tha r1ver then the coprolite bPd, about 2 feet thick, under which again Ouse,'but at Wick End, about a mile north of Stagsden, it is a considerable thickness of 8and,•a well so feet deep not ceases to be traceable. We find it again on the east side of having passed through it ; sometimes the nodule bed is as the Ouse in some brick-pits and lime-kilns, whence it curves much as 6 feet thick ; numerous pebbles of qua;tz occur, round by Clapham to Oakley Hill, where it is cut. off by an which have to be picked out. The word coproltte should east and west fault, re-appearing at Milton Wood about a properly only be applied to the fossil dung or reptiles, fishes mile eastwards· thence it runs northwards out of the county ' . &c. but most of the masses which go by that name are by and Souldrop. The Width of the outcrop pieces of wood mineralized by infiltration of phosphatic is remarkably even, averaging one-quarter of ~ ~ile. The matter, casts of shells, bones &c. and from their worn aml ·beds appear nearly horizontal. Ostrea .ilfarshn IS the most rolled appearance they seem mostly to h_ave b~en washed frequently occurring fossil. . out of earlier deposits, as the Oxford and K1mmendge Clays. 0:1-jord Clay.-This is a bluish clay~ weatheri_ng yellow, They contain 49 per cent. of phosphate of lime, and 7 per _and several hundred feet thick, wh1ch occupies all the cent. of carbonate of lime, according to an analysis by Dr. . central and north-eastern portions of the county. At the Voelcker · at Millbrook there is only IS feet of sand below base sandy beds occur locally, known as ~eltawa_y's Rock, the phosphate bed, and at Little Brickhill it rests upon the wa~ forming a link between the Cornbrash, which accumu­ Oxford Clay. In 1879 there were raised 5,000 ~11s of lated in shallow water, and the Oxford Clay, wh1ch_ was ~ Coprolites from the lower green sand of Bedford!:.hire, the . deep sea deposit. The latter forms a stiff retentive sml value being 28s. per ton. which is largely in pasture, but it is often so deeply covered by surface deposits-tu be noticed furiher on:-a:' not to The Gault is a bed of bluish-grey clay, 200 feet thick, exercise any influence on the character of the sml ; 1t forms which rests upon the Lower Greensand; it decreases in all the substratum of the Fens further north, and Professor thickness as we follow it north-eastward into Cambridge­ H. G. Seeley has proposed the name of Fen-clay for it, a shire. From and Ea ton. Bray~ we can_ trace it term however, which is only locally used; it is largely dug by Milton Bryant, Toudington, Westonmg, Sl11lhngton, for b;ick-making, and for claying the soil of the fe~s. The Arlsey, Shefford, l>unt·m, \Vrestlingworth and Cockayne band of gritty limestone known ~~:s the Coml Ra_g IS 11:bsent Hatley. It furnishes a soil know!_l as "black lanu," and in this district, so that there IS no well-marked lme of forms part of the plain which stretches from_ thCJ foot ?f thtl division between the great mass of the Oxford Clay below, chalk escarpment; it is largely dug for br1~·ks, ~nd 1~ the and the Kimmeridge Cla11 above. The latter has not in con­ excavations at Arlsey a face of so ,"'r 6o f_eet m height IS ex­ sequence been mapped "by the Geological Survey in ~his posed; fossils are tolerably numerow., A vzcula and Plzcatula county, but it is probably represen~ed on the eastern s1?e. being the commonest species. Local geologists must determine th~s by care~ully <:ollec~mg Upper Coprolite Bed.-At least two weli-IJJarkell seams or . and noting the localities of the fossils found 1~ the1r_ neigh- "coprolites" occur in the Gault, south of llarton. North bourhood. From a good section near Ampth1ll foss1ls have of this place, the upper band forms q line between the gault been obtained, which shows that the beds of clay there are clay and the lower marly beds of the Chalk ; the nodules are Iiear the transition line from the Lower to the Upper Clays ; dark-coloured and very rich in phosphate; this is the same they are abont the horizon of the. Coral Rag. In the Oxford band which is so largely worked near Cambridge, and it has ·Clay proper, Gryphaa dilatata, a wide thick-sh_elled kind of been supposed to represent the Upper GreerL:Jand. 1\Ir. Juke:;­ oyster is very common; bones of reptiles, fish-teeth &c. Browne has shown, hflwever, that it is a resnit ot the denu­ fl.bo occur. dation of tlte Gault, aml agrc:)S w1th Mr. "'lutakcr m c.m·