Mousehold Heath and Poringland near Norwich, Wymondham, &c.

Traces of gravel occur further south in Essex on Langdon Hill, in Middlesex on Hampstead Heath, in Kent on Shooter's Hill, &c. They are usually made up largely of flint and quartz pebbles, and are seldom of great thickness, varying usually from 2 or 3 to 10 or 12 feet.

The Tertiary hills of Berkshire and Surrey are capped by gravels of uncertain age.'

Hessle and Kelsea Beds.-The district of Holderness in Yorkshire, a tract of low-lying ground south-east of the Chalk Wolds, is made up of an interesting series of gravels, sands, and clays, which have been described by Prof. Phillips, Mr. Prestwich, Mr. S. V. Wood, jun., and others. The deposits include:

Hessle (Boulder) Clay, a brick-red clay with a few large pebbles, and characterized by fragments of coal-smut, about 10 feet in thickness. Hessle Gravel, including yellow sands and gravels, 10 feet in thickness.

They rest upon the Boulder Clay (Upper Glacial).

Mr. Wood considers the Hessle Clay as one of the latest Glacial deposits, formed when the land was emerging gradually from the sea.

At Kelsea Hill near Hull, the Hessle Clay with underlying gravel and sand (Kelsea Hill Gravel) is estimated by Mr. H. F. Hall to have a thickness of 65 feet. The Kelsea Hill bed contains Cyrena fluminalis, and marine mollusca, such as Ostrea edulis, Tellina Balthica, Buccinum undatum, Purpura lapillus, &c. A similar bed occurs at Paull Cliff.

At Hornsea lacustrine clays occur above the Hessle Clay. (See p. 332.)

In these gravels are found subangular pieces of quartz or rock-crystal called Bagshot Diamonds,' which have been drifted far, by many stages, whether from the Breton, Cornish, or Welsh area of old rocks. (T. R. Jones.)

Messrs. Wood and Harmer correlate the gravels of Hunstanton and March, and also the fluviatile deposit of Barnwell in Cambridgeshire, with the Kelsea beds.

They have, however, not been able to trace the overlying Hessle Clay further south than Steeping in Lincolnshire.

Brickearth of the Nar.-With the Kelsea beds may be associated the Brickearth of the Nar, so well known through the labours of Mr. C. B. Rose.

The Nar is a tributary of the Ouse, and the brickearth, a bluish sandy clay, has been traced from Narford to Watlington. It has a thickness of 20 feet or more, and contains, amongst other shells, Turritella communis, Aporrhais pespelicani, Ostrea edulis, Litorina litorea, Natica nitida, &c. The shells are in fine preservation; and there can be little doubt, according to Messrs. Wood and Harmer, that the deposit was formed in an estuary connected with that sea, which a Post-Glacial depression, shown by the Hessle beds, caused to overflow the lower elevations of the eastern side of England.

Sands and gravels containing marine shells, many of them now existing in British seas, but which indicate on the whole colder conditions, have been found at the heights of 1,200 feet at Macclesfield, and 1,350 feet at Moel Tryfaen near Caernarvon.

At Macclesfield, according to Mr. R. D. Darbishire, the shells include Cytherea chione, Cardium rusticum, Arca lactea, Tellina Balthica, Cyprina Islandica, Astarte arctica, Turritella communis, &c.

At Moel Tryfaen the following mollusca are most abundant, Tellina Balthica, Cyprina Islandica, Cardium edule, Turritella communis, Fusus antiquus, &c. The Drift here is described by Mr. Mackintosh as consisting of 35 feet of

irregularly stratified gravel and sand, which rises from the floor of the highest excavation of the Alexandra Slate Quarry to within a few yards of the rock-crested summit of the hill. In the opinion of Mr. Wood, it has not yet been satisfactorily shown that these deposits are the equivalents of the Middle Sands of the Lancashire coast. These latter, at Blackpool Cliff, &c., have yielded Nassa reticulata, Buccinum undatum, Aporrhais pes-pelicani, Purpura lapillus, Litorina litorea, Astarte borealis, Cardium edule, Tellina Balthica, Ostrea edulis, Mytilus edulis, &c. Similar shells occur in the Lower and Upper Boulder Clays of North Wales, Cheshire and Lancashire, and Mr. S. V. Wood, Jun., regards this Upper Boulder Clay as not improbably the same as the Hessle Clay. (See p. 305.)

Turning to the south coast of Ergland, we find at Brighton, and westwards, between the Chalk-hills and the sea, that the surface of the country is formed, first, by a raised terrace of red gravels,' lying on the sloping base of the Chalk-hills, and on the old Tertiary deposits; secondly, by the gravels of the Chichester Levels, or the 'white gravels.' These latter are distinctly bedded and seamed with sand, and are more water-worn than the red gravels which pass under them; and thirdly, the white gravels are overlaid by brickearth,' which is somewhat variable in its characters. These, with their equivalents, are described by Mr. Godwin-Austen as the Glacial deposits of the district.

At Selsea the Glacial deposits are about 25 feet in thickness, and contain a variety of pebbles and boulders of granitic, slaty, and old fossiliferous rocks. One boulder measured 27 feet in circumference.

Near Selsea, on a branch of Pagham Harbour, there is a remarkable phenomenon called the 'Hushing Pool.' This, according to Mr. P. J. Martin, is simply the bubbling and hissing produced by the disengagement of the air from the gravel before the incoming tide.

Mr. Godwin-Austen thinks it probable that the superficial brickearth of the district under notice was formed in a land-locked lagoon, subject to periodical freezing; and that the Elephant-bed' at Brighton is one of its many and variable equivalents (in this case probably subaërial).

Sir Charles Lyell, speaking of these deposits, remarks that they are the most southern memorials of ice-action and of a Post-pliocene fauna in England. A marine deposit, exposed between high and low tide, occurs on both sides of the promontory called Selsea Bill, in which Mr. Godwin-Austen found thirty-eight pieces of shells, and the number has since been raised to seventy. This assemblage is interesting because, on the whole, while all the species are recent, they have a somewhat more southern aspect than those of the present English Channel. What renders this curious is the fact that the sandy loam in which they occur is overlaid by yellow clayey gravel with large erratic blocks which must have been drifted into their present position by ice when the climate had become much colder. These transported fragments of granite, syenite, and greenstone, as well as of Devonian and Silurian rocks, may have come from the coast of Normandy and Brittany, and are many of them of such large size that we must suppose them to have been drifted into their present site by coast-ice. The gravel contains a few littoral shells of living species, indicating an ancient coastline. (Lyell.)

At Brighton, east of Kemp Town, the beds exposed are:

The Elephant Bed, provincially termed Coombe rock, is

Y

chiefly made up of chalk rubble. It contains remains of the Mammoth (Elephas primigenius), Horse, Ox, Red Deer, Whale, &c.

MARINE DEPOSITS.

Raised Beaches.

These consist of accumulations of sand and shingle generally containing recent marine shells, which have been formed by the sea, but yet occupy such positions at a height above the present reach of the breakers, as to necessitate the opinion that changes of level in the land have taken place since their deposition.

As Mr. Kinahan has pointed out, littoral deposits may be accumulated at varying levels at the present day, owing to the variations in tide heights in different localities. Therefore if we find raised beaches occupying different elevations in a certain district, it does not necessarily follow that the land has been unequally uplifted since the formation of the beaches.

Our Raised beaches may be connected with oscillations that occurred in the Glacial period. Long ago, in describing the raised marine beds on the Devon coast, and commenting upon the paucity of the molluscan remains contained in them, Mr. Godwin-Austen observed that not only are the characteristic forms of our south-western coasts entirely wanting, but we miss all those other shells which any beach, at the present day, would readily supply. This is only negative evidence, but it suggests that the period of these raised deposits may have been one less favourable than the present to the development of marine life, owing, perhaps, to a lower temperature; such as the broken up or detrital edges of the slate rocks would also indicate. (See p. 317.)