This formation, marked g7, is capable of being divided into two well-marked zones or stages-similar to those which have been shown to exist in the neighbourhood of Cheltenham, and extending eastward into Oxfordshire1:-the lower zone, which comprises the Stonesfield slate; and the upper, of which the typical section occurs in this sheet at Sapperton Tunnel. LOWER ZONE. At the base of the Great Oolite, along the margins of Stroud and Nailsworth valleys, a few inches or feet of brown sandy slates with partings of clay may frequently be observed, which probably represents the Stonesfield slate of Eyeford and Sevenhampton, although the characteristic fossil Trigonia impressa is wanting. This is surmounted by from 20 to 40 feet of white shelly oolite, in which false bedding is prevalent, being, indeed, a characteristic feature of this zone. The fossils are very abundant, as has been shown by Mr. Lycett, but they are generally in a fragmentary state, and give evidence of having been drifted by currents. These beds furnish the valuable "Bath freestone," which near Corsham is worked underneath the Forest marble by means of vertical shafts and tunnel work.23 One of these at Lower Pickwick In the excavation of a portion of the Box tunnel, the beds of the Fuller's Earth were reached and great quantities of it were drawn up one of the shafts and spread on the "spoil bank," on the top of the hill. This afforded a grand opportunity for studying the fossil forms which are abundant in some of the beds. And even at the present time many specimens may be obtained among the bushes with which the banks are overgrown. 1 See Memoirs of the Geological Survey,- Geology of Cheltenham, p. 53, et seq. * It is probable that the greatest amount of mineral wealth in the county of Wilts, is to be found in the Great Oolite-the "Bath Freestone." It is to be hoped that the Pisolitic Iron Ore of Westbury, and the Lower-Green-Sand Ore of Seend may, one of these days, yield large profits, but as yet the Freestone bears the palm in a commercial point of view. The following account of the Great Oolite at Box, from the pen of Mr. J. S. Randell, is extracted from a paper read at the Meeting of the British Association, Bath, 1864. Nowhere, I believe, in Great Britain (indeed in Europe) are the lower members of the Jurassic group of rocks so extensively developed as in the Bath district, where each group seems to have attained its fullest recognized development. Nowhere can the whole Jurassie (Oolitic) series be so readily studied-nowhere so readily understood. This applies to the Lias in its three divisions; to the Inferior Oolite, the Fuller's Earth, the Bath or Great Oolite, distinguished here for its economical value, and at Minchinhampton and other places for its fine and typical organic remains; and above this series, but intimately associated with it, to the Forest Marble and Cornbrash, which are highly developed, and succeeded by the Oxfordian and Kimmeridgian groups,-not omitting the Portlandian beds at Swindon, and the Purbecks of the vale of Wardour. I purpose to direct attention to the Bath Oolite only, determining the position of that zone from which the freestone is extracted, and on which the wealth and comfort of the population of this neighbourhood, engaged in quarrying operations, so much depend. The natural grouping of the beds constituting the Great Oolite in this district, falls under three well marked divisions, all well exhibited in the sections exposed at Murhill, Westwood and Farley Downs, Combe and Hampton Downs, Box and Corsham Workings, &c., &c. Throughout the Bath area, immediately below the Forest Marble (when present), we meet with the following groupings:1, The Upper Ragstones. 2, The fine Freestones or Building Bed. 3, The Lower Ragstones. These constitute a series varying from 60 to 120 feet in thickness. The Upper Ragstones.-This series consists, in the upper part, of coarse shelly limestones, with usually a few beds of white fine-grained limestone, possessing distinct and well defined oolitic structure, and containing finely comminuted shells; these are again succeeded by tough argillaceous beds of limestone, usually of a pale brown colour and smooth in texture. The whole ranging from 25 to about 50 feet in thickness. No beds of workable value occur in this upper series. The fine Freestone or Building Beds. -Succeeding the Upper Ragstones above-mentioned, and commencing the second series, there appears to be everywhere in this district a peculiar bed, extending over a large area, termed the "cover" or "capping," varying in thickness but generally hard in texture; this forms the roof or ceiling to the fine economical building freestones below, and is a marked feature in extensive underground workings, both for its horizontal extent, and for its importance as a protection to the workmen. At Bradford, Westwood, and Murhill, this bed is a coarse, shelly, hard limestone. At Corsham and Box, it is a closer grained and tough rock. Succeeding this, is the true "Bath Stone," or fine freestone, which I believe, with minor differences, occupy the same position or horizon over the whole of the Bath district. It is from 20 to 30 feet in thickness. The beds worked for commercial purposes, are usually evenly grained in texture, regularly bedded, yield well to the saw, are not fossiliferous (or the shelly matter is very finely comminuted), and give evident proof of having been accumulated in a somewhat deep and tranquil sea, or away from any littoral or wave disturbance: this the almost total absence of organic remains seems to confirm. The size and structure of the oolitic grains, the presence or absence of silicious particles, or of finely divided shelly matters; materially affect the stone during the process of working, or influence it after it is placed in position and subjected to weathering under atmospheric changes. In some localities the beds assume an earthy structure, are indistinct in texture, smooth and close grained, and hold more moisture. From general observation and the correlation of measured sections, it appears that these fine-grained regular beds thin away in a south easterly direction; indeed it cannot be doubted that the Great or Bath Oolite as a group, exists under irregular conditions and dies out and disappears as a wedge-shaped or lenticular mass, to the east and south-east. The Lower Ragstone,-This series appears to be persistent everywhere throughout the entire area, and rests upon the Fuller's Earth. There are numerous and generally well defined beds of a coarse shelly texture and hard crystalline limestone, exhibiting much false-bedding especially towards the base. Many species of mollusca are found in the bottom beds, such as Ostrea accuminata, Terebratula ornithocephala, Rhynconella concinna, Trichites, Tancredia, &c. Fine sections may be seen at Murhill on the north side of the Bradford Valley, and Upper Westwood on the south. Detached masses of these rocks frequently occur on the inclined slopes of the valleys, owing to the slipping of the Fuller's earth on which these Lower Ragstones immediately rest. The chief economical use of these beds is confined to local purposes, it being utterly unfit for architectural work or exposure to atmospheric influences. The stone used in the construction of the aqueduct conveying the canal over the river Avon at Avon-cliff was obtained from the beds of this series in the Westwood quarry, and although in situ the stone appears to be of fine texture and quality, yet it rapidly decomposes on exposure, and the stone-work of the Avon-cliff aqueduct is a perishing evidence of its non-durability. At the Box and Corsham quarries these lower beds, though not observable at the surface, are nevertheless 43 feet in thickness, and are chiefly composed of fine textured limestones, but are not worked, as they are of no commercial value. 3 The mode of working the stone from the Box quarries has been so ably described in the "Builder" of August 30th, 1862, that we are glad to transfer extracts from it to the Magazine, and at the same time to thank the Proprietor of the "Builder" for the loan of the illustrative woodcuts. Box-hill itself forms the centre of the oolitic district, roughly triangular in outline, and comprising an area of about three square miles. Many parts of this and the neighbouring locality have been worked for stone, with more or less activity, from a very early date; but though quarries were opened here as many as 300 years ago, it was not until after Brunel's tunnelling operations had demonstrated how large an amount of good material might be got out of the district, that the workings began to receive any adequate development. The construction of the Great Western Railroad, however, gave a great impulse to this previously limited industry, and the facilities for transit which its completion afforded, soon attracted the attention of practical men. The present proprietors of the Box and Corsham Quarries, Messrs. Randell & Saunders, were not long in seizing upon the opportunity which these circumstances appeared to offer for the establishment of a large trade, and in 1845 they commenced the undertaking, which has since attained its present large proportions. Nothing can be more unlike the ordinary experiences of mining excursions than a visit to the Corsham Quarries. Those who have suffered in various parts of the country from hot, damp, and dirty scrambles through underground passages, will have a sense of surprise and pleasure when they first set foot within the wide, lofty, and well ventilated roads which ramify for miles through the bowels of Box-hill. The accompanying map will explain the general arrangement of the quarries. All the workings which have yet been opened, are situate on the northern side of the tunnel. They are divided into two districts, called respectively the Corsham Down and Box-hill quarries; the former occupying the eastern, and the latter the western, side of the hill. Entrance to both of these is obtained at the Corsham end, where the main road (A) joins the Great Western Railway on a level; a communication between the two sides being established by means of the road (B), along which all the Box stone is hauled to the railway trucks. Both these roads run parallel with the tunnel, debouching, as we have seen, upon the main line, and puzzling visitors strange to the locality with the apparently anomalous phenomenon of a double entrance to Mr. Brunel's great work. The dimensions of this approach almost rival those of its neighbour, permitting the ingress of two rows of waggons for some distance, but presently narrowing to one line of broad-guage rails, which are continued as far as the first of the Corsham workings, where they terminate opposite the discharging platform, to be more fully described hereafter. From the main roads the workings spread northwards and westwards, as shown upon the plan, into complex reticulations of great and yearly increasing extent, all of which communicate by means of gently falling tramways with the discharging platform. The utilization of gravity as a means of locomotion, is carried out with much completeness throughout the works. In drawing from the Box side, horses are employed to haul the stone only through a portion of the distance; more than half of it being accomplished by gradients. The natural disposition of the strata has greatly assisted in laying out the quarry thus. The ventilation is very efficient throughout the quarry. In all colleries where the ventilation is effected by means of upcast and downcast shafts, it is usual to heat the upcast by means of fires, which, increasing the volume and decreasing the weight of the atmospheric column within it, assists in producing a sufficient draught. At Box, however, no artificial stimulus is needed to keep up the circulation. The downcast shaft being here represented by a wide and lofty road entering the hill upon a level, admits air so readily that a few "upcasts' here and there communicating with the surface suffice to establish an abundant current. Nowhere throughout the whole quarries is there anything approaching to a scant supply of oxygen, and the visitor is never conscious of breathing under conditions at all different from those of ordinary life. A walk of about a furlong brings us opposite the point where all the stone taken out is loaded into railway trucks, a process effected with great simplicity and economy. The single line of broad-guage rails which we have hitherto followed, stops here, but it is met and accompanied through the last few hundred yards of its length by a narrow tramroad, about 23 feet guage, running parallel with the main line, but laid at such a level as to bring the little trollies forming its "rolling stock," to the same height as the larger waggons, into which the blocks are readily shifted by means of two powerful cranes, without any lifting whatever. By this arrangement, a large amount of work is got through in the course of a day, one crane alone being capable of loading up some 6000 feet of stone, or nearly 400 tons in ten hours. This discharging platform, as we have previously named it, is in direct communication with the whole of the workings, every one of which has its own branch of narrow-guage rails; and along some of these feeder lines the small trucks are constantly passing with their burdens. Immediately opposite where we stand, is an entrance to the first of the Corsham side workings, lying a little off the main road, and approached by a narrower passage cut almost at right angles to it. Turning into this, we shortly find ourselves in a large open space, lighted with tolerable brilliance by many candles, and occupied by a group of workmen all busily engaged in various quarrying operations-some sawing, others hoisting; some moving great blocks on rollers towards the trollies in waiting, and others manning the handles of a crane occupying the centre of this little amphitheatre, We will make this "working" our pattern card. One uniform system of getting stone prevails, suggested and occasionally slightly modified by the natural peculiarities of the rock itself. Like almost all other stratified deposits, the Bath oolite lies in "beds," as they are named both by geologists and quarrymen; the successive |