EXCURSIONS ILLUSTRATIVE OF THE GEOLOGICAL CHARACTERS AND ORGANIC REMAINS OF THE TERTIARY DEPOSITS OF THE LONDON BASIN.

In leaving London for any part of England, the reader will remember that the area on which the metropolis is situated, as well as the surrounding district to a distance varying from a radius of ten to twenty or thirty miles, consists of the marine Tertiary eocene strata (see p. 24), which have been deposited in, and still occupy, a depression, or excavation of the Chalk, called the London Basin (Wond. p. 229). Around this formation, the Chalk forms a distinct boundary on the south, west, and north, rising up into chains of hills or downs; but on the east the range is broken, and the Tertiary basin lies open to the sea, affording a passage for the Thames and its tributary streams. From this geological character of the metropolitan district, it results, that all the lines of railroad proceeding from London traverse, for the first ten or twenty miles, beds of clay, loam, and loosely aggregated sand and gravel; hence the numerous slips that have taken place in the embankments; as for example, at New Cross, Wandsworth Common, near Hanwell, &c.; and in all these lines it is obvious, from the nature of the strata and the steepness of many of the cuttings, that similar catastrophes will again occur.

The next geological feature observable in the lines of all the London railroads is the Chalk, which is invariably passed either by steep cuttings, or tunnels, or both; as for example, from near Croydon to Merstham, by the South-Eastern; from near Basingstoke to beyond Winchester, by the South-Western; from Maidenhead to beyond Wallingford, by the Great Western; and from beyond Watford to near Ivinghoe, by the Birmingham line.

After passing through the Chalk, and over the marls and sandstone strata of the Cretaceous formation, the Oolitic group (consisting of Portland stone, Kimmeridge clay, &c.), the Lias, New Red or Triassic, and Carboniferous deposits successively appear on the lines of railroad; excepting on those of the South-Eastern, which, upon leaving the Chalk-formation, traverse the fluviatile beds of the Wealden, as we shall hereafter more particularly describe.

EXCURSION TO THE ISLE OF SHEPPEY.

Every one knows that Sheppey is a small island about ten miles in length, lying at the mouth of the Thames, at the distance of between forty and fifty miles east from London; but every one does not know that the Isle of Sheppey is an inexhaustible mine of fossil treasures; and that from its cliffs, and on its shores, may be gathered innumerable relics of tropical plants, of quadrupeds, birds, serpents, turtles, fishes, crabs, lobsters, shells, &c. all belonging to species that now no longer exist.

A visit to the town of Queenborough afforded me, when a boy, the first opportunity of beholding fossil remains in such a state of preservation, and in such profusion, as to excite in my mind an uncontrollable desire to investigate the nature and origin of objects which I had been taught to believe were either produced spontaneously in the earth, or were left in their present situations by the waters of a universal deluge. At a short distance from the inn where we sojourned, was a vitriol manufactory, and considerable plots of ground were covered with the pyritous clay, obtained from the neighbourhood. To my great astonishment, I perceived that masses of this fossil earth were almost wholly made up of stems, twigs, and fragments of wood, with innumerable fruits, seed-vessels, and berries, of kinds altogether unknown to me. These fossils were of a dark colour, some quite black, very heavy, and permeated with the mineral substance termed sulphuret of iron, or pyrites. Many were so brittle as to fall to pieces upon being handled, but others were of a stony hardness, and I quickly filled a handkerchief with my newly discovered treasures, and hastened home to examine them at leisure. They consisted of the usual kinds of fossil fruits so abundant in the island (see Lign. 63 and 64, p. 188), with casts of shells, and a few claws of crabs, and teeth of fishes.

Most of the specimens fell to pieces in the course of three or four months, but a few were durable, and these still occupy a corner in my cabinet as precious mementos of my juvenile researches. Many years afterwards I revisited Sheppey, and made a large collection of its fossils, which is now in the British Museum. Of late years, the increasing taste for PalÆontology has brought numerous visitors to the island, which steam navigation has now placed within a few hours’ distance of the metropolis; and the demand for choice fossils has given rise to several local dealers. The student may, with but little trouble or expense, visit the island, make himself familiar with its geological character, and return laden with the fruits of the ancient spice islands, of whose ruins this mass of clay, in the embouchure of the Thames, is almost wholly composed. As it is some years since I last visited this interesting spot, I have obtained, as a Cicerone for the reader, the most indefatigable and successful investigator of its fossil Flora, Mr. Bowerbank; and as the courtesy of this gentleman is equal to his intelligence and scientific attainments, the traveller will have no reason to regret the absence of the author. A trip from London to Sheppey and back, affording time to procure a good collection of fossils, may be easily accomplished in three days.

EXCURSION TO THE ISLE OF SHEPPEY, BY J. S. BOWERBANK, ESQ. F.R.S.[785]

"The best conveyance is by the Southend and Sheerness steam-packets, which leave London-bridge on Tuesdays, Thursdays, and Saturdays, at 11 o’clock in the morning, and reach Sheerness about 4 or 5 o’clock in the afternoon. The town is divided into two parts,—the one contained within the limits of the garrison being designated the Blue town, while that beyond the fortifications to the north-east is designated the Mile-town; and it is to this portion that I should recommend the visitor to proceed, and take up his quarters either at the Royal Hotel, or at the Wellington: the latter is an exceedingly snug and comfortable house, to which I have resorted for many years. After having established himself in the inn, he should request the attendance of Mr. Hays (better known perhaps by the name of Paddy Hays), from whom he may purchase, at a reasonable rate, some good fossils, such as crabs, lobsters, heads and portions of fishes, and numerous species of fossil fruits. Our traveller will then have accomplished all that can be done towards the acquisition of fossils until the following morning; there not being, I believe, any other collector in the town from whom purchases can be made.

"On the following morning an early breakfast is desirable, as a considerable extent of ground is to be traversed. It is advisable to go provided with live or six sheets of soft paper, to wrap fragile specimens in; and a few cotton or linen bags, of about four or five inches in diameter, to separate the large from the small fossils; the whole to be carried in a good-sized blue bag, or haversack; a chisel and light hammer are the only instruments required. If the geologist has a desire to view the great section of the London Clay, afforded by the cliffs on the north shore of Sheppey, and is content with the comparatively few fossils which he may be able to procure by his own exertions, he may proceed in the following manner:—Leaving Sheerness by the new town, he will pass along the sea-wall, towards Minster, until he reaches Scaps-gate, where the cliffs begin to rise from the low lands of the western end of Sheppey. A few cottages are scattered round this point, some of the inhabitants of which work upon the beach, collecting either cement-stone or pyrites, the latter being better known by the name of copperas. To these application should be made for ‘curiosities,’ and very frequently excellent specimens, and at a small price, may be thus procured. From this point the route will be under the cliffs upon the shingle, amidst which, dark patches, ten or fifteen yards in length, will be observed, composed of nodules of pyrites, intermixed with pyritized fragments of branches of trees, in great abundance. It is at such spots that the numerous and beautiful specimens of fossil fruits are found; but, to ensure success, the collector must be content to go upon his knees, and carefully search among the fragments. The whole of the beach, from about the parallel of Minster church to Warden Point, abounds with these patches of pyrites; and I have by this means obtained in the course of a morning upwards of one hundred fine fruits of various sizes. Care must be taken in such an investigation of the coast, that it be undertaken during the falling of the tide, or unpleasant consequences may arise from being shut in between the banks of mud which are projected into the sea at many points of the coast.

"If the principal object be the attainment of the greatest quantity of fossils, a different course should be pursued. The collector should then, after having made his purchases at Scaps-gate, direct his steps towards Minster church, passing which, he will proceed on the road towards Warden. About three-quarters of a mile beyond the church there is a lane on the left hand, leading towards the Royal Oak, in which lives a woman named Mummery, and several others, who work upon the beach, and from whom fossils are frequently to be procured. These people will direct him to the cottage of a family named Crockford, who have usually a good assortment of fossils; and to many other parties who also work upon the beach, and reside between this point and Hensbrook, to which place he must now direct his steps. At Hensbrook inquiry should be made for a man named Pead, who has generally a considerable number of good specimens in his possession. From this point (Hensbrook) the collector must proceed along the top of the cliff towards Warden, calling at the various cottages in his way, until he arrives at Warden Point, at which place he must inquire for Mud-row, many of the inhabitants of which work upon the beach, and from whom a considerable addition to the specimens already collected may be purchased. Beyond this point nothing will be obtained, and the best way to return to Sheerness, is by the road which runs through the most level portion of the country; the path along the north cliff undulates very considerably more than the road.

"The course of proceeding thus sketched applies to the supposition that the time is limited to three days, but if a longer period can be spared, I should recommend the tourist not to leave Sheerness without viewing the dock-yard; and the return to London may be made by the way of Chatham and Gravesend, affording the gratification of a view of the dock-yard and lines at Chatham, and of the fine old cathedral and castle at Rochester; at the same time, enabling him to arrive in London on the evening of the day that he quits Sheerness."

If the student’s time will permit, a day or two may be profitably spent at Herne Bay on his return; and search should be made for fossils under Swale Cliff and Studd Hill, where numerous fruits and some unique mammalian remains have been found by William Richardson, Esq. (see p. 791). Should he land at Gravesend, as recommended by Mr. Bowerbank, he should proceed towards the lime-kilns which lie on the London side of the pier, on the right bank of the Thames. To the left of the lime-kilns he will perceive a road leading by some bold chalk cliffs to the high ground above Gravesend; and on the right hand there is a row of cottages, or rather huts, inhabited by the labourers that work in the quarries and kilns. Many of the usual fossils of the Kentish Chalk may be obtained of the women or children in these huts; and sometimes Cidares, or turban Echinites (p. 314), with spines; and Star-fish (p. 306). A visit to the chalk-pits at Purfleet, on the opposite side of the river, is very desirable; many interesting fossils having been found in that locality. The Kentish Chalk in this district is much softer than that of Sussex, and the fossils may be easily cleared with a penknife, or by brushing in water; care should be taken not to wash them roughly, as they will readily separate from the chalk.

The fossils procured from the Isle of Sheppey, by such an excursion, will probably consist of portions of stems and branches of trees, and fragments of wood, perforated by Teredines (see p. 193); specimens of the fruits of palms, resembling the recent Nipas of the Moluccas (p. 188), and of plants allied to the Cucumber, Bean, Cypress, Laburnum, &c. (p. 189); claws and fragments of the shields of Crabs (p. 512); bones of Crocodiles, Serpents, and Turtles; bones and teeth of Sharks (p. 591); Rays (p. 598), and other fishes; and several species of the usual shells of the London Clay (p. 383), and a specimen or two of Nautilus (p. 469).

NOTES FOR AN EXCURSION TO BRACKLESHAM BAT, ON THE WESTERN COAST OF SUSSEX.

The line of low cliffs extending from Selsea Bill to the mouth of Chichester Harbour exhibits a section of the Eocene deposits, varying in height from five or six feet to ten or twelve; it is covered at its base by a bed of shingle, fifteen or twenty yards wide, that extends towards the sea. The space between the termination of the shingle and the limit of low-water-mark is occupied by a bed of dark grey and greenish sand; and at certain seasons, numberless specimens of the fossil shells common in the Eocene strata of the London and Paris basins are thickly spread over this area.

Mr. Webster first directed attention to this locality, in his celebrated Memoir on the Tertiary Strata of England; and my friend, the late John Hawkins, Esq. of Bignor Park, followed up the inquiry. In 1821 I made a fine collection of the Bracklesham fossils, and published a list of them in Foss. South D. and Geol. S. E. Messrs. Bowerbank, Saull, Dixon, Coombe, &c. have subsequently made considerable and important additions to the catalogue; and besides many new species of shells, the vertebrÆ and other bones of Turtles, Serpents, and Crocodiles have been discovered. An excellent notice of this locality, from the pen of Mr. Bowerbank, appeared in Mag. Nat. Hist. (1840); and I am indebted to the kindness of the author for the following notes for the guidance of my readers.

"The part of the bay most interesting to the geologist is that immediately in the neighbourhood of Bracklesham Barn, especially at about a furlong to the east of that spot, where there is a small break or chine in the low clay cliff. At this place, and at a few paces east and west of it, beneath about six or seven feet of clay, there is a stratum of light green marly sand, abounding in remains of Venericardia planicosta and other shells, but which is often entirely hidden by thrown-up shingle, and it is very rarely that more than a few feet in length of this bed can be seen. It is from this bed, or from one exceedingly like it, somewhat lower in the series, that perhaps most of the interesting shells of this district are to be procured. If we proceed from this little break or chine westward, for about forty paces parallel to the coast, and then in the direction of a line at right angles to the cliff, and at the time of low water, we shall find, near the low-water-mark, the bed we have described as abounding in fossils exposed by the action of the sea in the most favourable manner. At this spot Venericardia planicosta is found literally by thousands, with the valves united, the shells resting upon their edges, and packed close to each other, exactly in the manner that we might expect to have found them, supposing them to have been recent shells with the animals yet inhabiting them. Comparatively very few are gaping, and their condition and position strikingly impress upon the mind the idea that when alive they must have inhabited the spot from which they are now disinterred; especially as there are numerous small and fragile species of other well-known London Clay shells, which could not have remained whole had they been subjected to much attrition amid the larger shells surrounding them. On the sands in the vicinity of this spot, I found large masses of Nummulites lÆvigatus cemented together, and numerous detached specimens of the same shell.

"At the eastern extremity of this bed, which, at the time of my visit, was opened for about fifty yards, I found Sanguinolaria Hollowaysii, a rare and fragile, but very beautiful shell, in a fine state of preservation. At about twenty or thirty yards westward of the western end of this interesting patch of shells, there are large blocks of this bed, which, being of a firmer texture than the surrounding parts of the deposit, have suffered less from the action of the water, and project about twelve or eighteen inches above the surrounding sand, and, by presenting an obstruction to the ebbing tide, they usually induce the formation of a small pool amidst which they stand. At the south-eastern side of this pool on one occasion I found the stratum, which is usually covered by the sand, completely exposed. At this spot there was scarcely a specimen of Venericardia planicosta to be seen, but instead of this shell, Turritella conoidea and T. edita were imbedded in a dark green marly sand; and among them, together with Fusus longÆvus and other well-known London Clay shells, I found Venericardia acuticostata and V. mitis, and a splendid specimen of Conus deperditus, fully equal in size to the one figured by Deshayes. Westward of this point I did not meet with anything particularly interesting.

"About midway between Bracklesham Barn and the Thorney coast-guard station, a series of patches of a deposit of chalk-flints was exposed; the first of these was nearly at low-water-mark, and the remainder of them ran, at short distances from each other, in a diagonal line towards the coast, nearly in the direction of a straight line drawn from their western extremity to the Thorney station-houses. Apparently, this stratum of flints has not, at any time, exceeded eight inches or a foot in thickness; they are, indeed, so thinly scattered, as rarely to occur piled upon each other: very few of them have suffered from attrition, and the greater part retain their original form and whitened surface. They are imbedded in the same light green marly sand which I before described as occurring at the bottom of the London Clay in the neighbourhood of the little chine near Bracklesham Barn. Amongst the flints there are numerous remains of the roots of trees, in the state of soft bog-wood; which indicate that this portion of the strata has been very thinly covered by the superimposed clay.

"Upon one of the bouldered flints, firmly imbedded in the marly sand. I found the most interesting of the valuable series of fossils which I had the good fortune to obtain during this excursion, namely, a fine specimen of AstrÆa[786] attached to the upper and exposed surface of a flint."

[786] AstrÆa, a species of coral; see p. 262.