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The St. Helen's Sands comprise pale green, yellow, and white sands, hardening into sandstone, with white and yellow marls and clays, having a total thickness of about 80 feet.

The Nettlestone Grits, which underlie them, include beds of grit, soft sandstone, clay and limestone, having a thickness of about 20 feet.

The sections vary much in detail. They yield Chara Lyelli, Limnæa longiscata, Paludina lenta, Melania excavata, Planorbis, &c.

BEMBRIDGE BEDS.

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This series was subdivided by Prof. Forbes into :-
Upper Bembridge Marl, consisting of marls and laminated grey clays,

yielding in great abundance Melania turritissima. Lower Bembridge Marl, comprising unfossiliferous mottled clays alternating with fossiliferous laminated clays and marls, with

Cerithium mutabile, Cyrena pulchra, &c. Bembridge Oyster Bed, a band containing Ostrea Vectensis. Bembridge Limestone, comprising the uppermost shell-limestones of

Headon Hill, Sconce, Hempstead Ledge, Gurnet Bay, Cowes, Binsted, Bembridge, &c. This limestone is sometimes hard and compact, at others soft and tufaceous. It contains Bulimus ellipticus (Bulimus limestone), Helix globosa, Planorbis discus, and Limnæa longiscata (Limnæan limestone).

The Bembridge limestone has been largely quarried at Binsted, East Cowes, &c.; but the beds are now seldom worked.

The Bembridge Beds have yielded remains of Trionyx ; also the Mammalia, Anoplotherium, Chæropotamus, and Palæotherium.

HEMPSTEAD BEDS.

These beds, deriving their name from their occurrence at Hempstead, were divided by Prof. Forbes into :

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Corbula Beds, brown and greenish clay with shelly bands,
Corbula pisum, C. Vectensis, &c.

96 Upper, containing Cerithium plicatum, C. elegans,

Corbula, Rissoa, Hydrobia, Melania, PaluFreshwater dina, &c. .

40 0 and Estuarine

Middle, with Cyrena semistriata, Cerithium,

, ' Marls Rissoa, Panopæa minor, &c. .

50 0 Lower, with Melania muricata, Melanopsis cari

nata, Cyclas Bristovii, Unio Gibbsii, &c. 65 0 These beds have been classed as Lower Miocene by Sir Charles Lyell, as Prof. Heer has recognized among some plant-remains found in them, four species common to the lignite of Bovey Tracey.

MIOCENE.

Until the year 1857 no traces of Miocene beds were suspected to exist in England; at that time attention was drawn to the lignites of Bovey Tracey in Devonshire; but it was not until 1860 that the question was finally settled. Then through the liberality of Miss Burdett Coutts these lignite-beds were minutely investigated by Mr. Pengelly, and the plant-remains collected under his superintendence were submitted for determination to Dr. Oswald Heer, who pronounced them to be undoubtedly Miocene. Lyell places the beds in the Lower Miocene division, as also the Hempstead Beds.

BOVEY BEDS.

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The celebrated clays and lignite-beds of Bovey Tracey have been long known, for the · Bovey Coal' has probably been worked for the last 150 years.

Sometimes spelt Meiocene.

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The Bovey Beds comprise two well-marked divisions, the lignite-beds which are developed at Bovey Tracey, and the clay-beds which are so largely worked near Kingsteignton and Newton Abbot.

The exact relations between these two divisions cannot readily be ascertained, for the lignite-beds are cut off by a fault (determined by Mr. Divett), where the vertical displacement is estimated at 100 feet; but so far as I could determine from personal examination the lignites form the upper series above the clays.

The beds opened up at Bovey (according to Mr. Pengelly) are as follows:

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Ilead,' superficial drift
Plastic clay
Quartzose sand
Clays and lignites
Sand.
Clay
Sand and fine conglomerate
Clays and lignites.
Quartzose sand with lenticular patches of clay
Clay and lignites

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A boring made east of the fault showed upwards of 80 feet of sands and clays, with some coaly beds in the lower portion.

The clay-beds of Kingsteignton are about 40 feet in thickness, resting on sand, and containing occasional sandy beds.

The total thickness of the Bovey deposit can only be conjectured as between 200 and 300 feet.

The beds extend over a considerable tract of low-lying heath-land bounded by ranges of hills. The physical and palæontological evidence points to the deposit having been formed in a fresh-water lake, which probably extended from Bovey Tracey to Kingskerswell, without being open towards Teignmouth. The purely sedimentary matter was evidently derived from the waste of the Greensand and of the granitie rocks of Dartmoor: the clays being due to the decomposition of the felspars, and the quartzose sands being the relics of the harder material. (See fig. 12, p. 110.)

It has been conjectured that the Lower Bagshot beds of Poole were similarly derived, and although there is great similarity in the general character of these beds and those of Bovey, yet it appears that the plant-remains of the two deposits are very distinct.

From Dr. Heer's investigations it seems that the woods covering the slopes which surrounded the old lake consisted mainly of a huge coniferous tree (Sequoia Coutssiæ), whose figure resembled in all probability its highly admired cousin, the Sequoia (Wellingtonia) gigantea of California.

The leafy trees of most frequent occurrence were the cinnamons and an evergreen oak like those which now are seen in Mexico. Species of evergreen fig were rarer. The trees of the ancient forest were evidently festooned with vines, beside which the prickly Rotang-palm twined its snake-like form. In the shade of the forest throve numerous ferns; one species of Pecopteris seems to have formed trees of imposing grandeur, while on the surface of the lake were expanded leaves of the water-lily.'

The lignite, which has been used extensively for fuel, is very little employed now, as it gives off a sulphurous smell when burning

The clay-beds yield excellent pipe and potters’-clay. The best clay is shipped at Teignmouth, whence it is sometimes termed Teignmouth Clay. According to Mr. Hunt's Statistics above 42,000 tons were sent from the port of Teignmouth in 1865. The mode of raising the clay is extremely simple—the gravel head is removed, and a large rectangular pit is sunk, which is supported by wood. The workmen cut out the clay in cubical lumps weighing about 30 lbs. each, and Hing them from stage to stage by means of a pointed staff; it is then carried to the clay cellars, and when properly dried sent to the potters.

| Phil. Trans., Part II. 1862.

Iron-pyrites is abundant in the lignite-beds, and from its presence spontaneous combustion sometimes takes place after heavy rain in the refuse-heaps.

The clays are employed for whitening stones, &c.; they have also been used in the manufacture of alum.

PLIOCEVE.

The Pliocene deposits of England, so far as known, occur in the Eastern Counties, and are recognized not only by position, but by the large per-centage of recent species of Mollusea which they contain. Their exact relations, however, to the Miocene period are not by any means definite, and some authorities have classed the lowermost division of the series—the Coralline Crag—as Miocene; but this seems to be an unnecessary complication in classification, and certainly the Crag deposits are closely united as well in their physical as in their paläontological characters.

Certain ferruginous sands containing casts of molluscs which occur on the Chalk in Kent and Surrey, were at one time considered as Cray, but their age is extremely doubtful, and it is uncertain whether they all belong to one period. (See p. 261.)

Some of the pebbly gravels which cap the Tertiary hills

1 Sometimes spelt Pleiocene. The term Icenian was proposed for the Pliocene strata, because their order of succession was first determined in the Eastern Counties. (S. P. Woodward.)

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