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upper beds of the Chalk contain very few nodular flints, so that the bedding is not well shown: sometimes thin layers of flint fill the narrow vertical openings of the even joints. These beds he calls the Margate Chalk; they have a thickness of about 80 feet. Below, the series called the Broadstairs Chalk is distinguished by containing layers of tabular and nodular flint. The Margate Chalk contains fossils identical with those of Norwich, where the upper beds have been compared to the Chalk of Maestricht in Holland and Faxoe in Denmark, in which countries the Chalk exhibits gradations into the Tertiary strata above.
An excellent description of the Chalk of Dover was published many years ago by William Phillips, and the following Table shows the chief divisions which he made; to these are appended some local names and the palæontological zones determined by Prof. Hébert : Chalk with few flints (Margate Chalk) Chalk with numerous flints:
Micraster cor-anguinum. (6. Broadstairs Chalk Ramsgate Chalk
cor-testudinarium. a. St. Margaret's Chalk ')
One of the most interesting discoveries in the Chalk was that of a Granitic boulder at Purley near Croydon, described by Mr. Godwin-Austen. It was originally about 3 feet long, and was accompanied by some decomposing fragments of a felspathic rock and with a compact mass of siliceous sand. Mr. Godwin-Austen considered that an ice-Hoe was the agent by which alone such a block could have been lifted from the coast and conveyed far out to sea.
At Grays Thurrock the thickness of the Chalk is upwards of 660 feet: at Harwich it was proved to be 888 feet, and at Kentish Town 640 feet. (See fig. 19, p. 257.)
1 These names were given by Mr. G. Dowker.
Economic Products, &c., of Chalk. The Chalk Downs produce a scanty herbage, to which sheep are largely devoted.
In some parts good crops of barley, turnips, and wheat are produced. The Lower Chalk and Chalk Marl are, as a rule, more fertile than the Upper Chalk. The ponds generally require to be clayed.
The Chalk Downs are considered to retain their ancient .character more than any other tracts of country. Beech trees grow exceedingly well on the Chalk where covered with clay-with-flints or brickearth, and in Buckinghamshire they are largely used for Chair-making.
In many places there is no durable stone save the scattered Sarsens.' 1 In other places, as before mentioned, hard beds have been worked for building-purposes.
The flints are largely used for road-metal and for buildingpurposes. When burnt and ground they are employed in the manufacture of china, porcelain, and fint-glass.
Gun-flints in former times were largely manufactured from the chalk-flints, and are still made at Brandon and Norwich for export to Africa.
The Chalk pits vary from 50 to 150 feet in depth. The men work at the top of the pits with levers (or where the chalk is very hard, with gunpowder), and throw the Chalk down in great masses, which break to pieces in their fall. The joints are taken advantage of in excavating the Chalk.
The Chalk is extensively burnt for lime: it is also prepared for whiting at Grays, Kintbury, and other places.
1 These will be described in the sequel.
2 The most remarkable blowing up of Chalk took place some years ago at the Round Down Cliff, Dover, when hundreds of tons were thrown into the sea to make an opening for the railway beneath the cliff.
3 The whiting is prepared by grinding the soft Upper Chalk, dug on the spot, to a fine pulp with water, and allowing the whole to flow into
Sulphuretted hydrogen, produced by the decomposition of iron-pyrites and water, is sometimes rather troublesome to well-sinkers, and Carbonic acid gas (Choke damp) is apt to accumulate in tunnels and borings in Chalk.
The Chiltern Hills and the North and South Downs are everywhere celebrated for the extent of their prospects. The boldness of the escarpment and the whiteness of the substance have given the idea of ornamenting the country in various parts by cutting away the turf. The White Horse, above Uffington in Berkshire, occupies about an acre of ground, and may be seen from some points of view at the distance of twelve miles. There is another land-mark of the same kind at Chervil, near Calne in Wiltshire, and a third in the neighbourhood of Thetford. On the chalk hill that faces Weymouth is a representation of George III. on horseback. Near Cerne is a figure of a giant holding a club in one hand and extending the other; this colossal figure is 180 feet in height. Near Prince's Risborough a large Cross has been cut.
a series of tanks or reservoirs connected with each other. The sediment is formed into cakes and dried. (H. W. Bristow.)
| These notes are partly taken from Cony beare and Phillips, Geology of England and Wales.
TERTIARY OR KAINOZOIC.1
EOCENE, MIOCENE, AND PLIOCENE.
Our English Tertiary strata when looked at in a large way stand out in marked contrast to the Secondary and Palæozoic strata by reason of their lithological characters. They are composed for the most part of soft clays, and sands, with occasional pebble-beds. The marked lines of stratification so conspicuous in most of the Secondary strata are not recognized, and naturally, because the beds are less consolidated. We see in them the transitional strata between the rocky or stony formations and the recent deposits. The organic remains now begin to approach very closely to existing types: every stage brings us into contact with forms nearer to those now living.
It was for this reason that Lyell proposed the terms Eocene, Miocene, and Pliocene for the three great divisions into which European Tertiary deposits had been divided. These terms were based upon the percentage of recent mollusca found in the strata to which they were applied. Thus the Eocene strata (dawn of recent) contain a very small proportion of living species; the Miocene strata (less recent), although containing more recent species, yet contain a minor
The term Kzinozoic (Cainozoic, or Cænozoic) signifies recent life.
proportion compared to the Pliocene strata (more recent), which contain a plurality of recent species.
The Tertiary strata are characterized by numerous genera of large Mammalia, many genera and species of Mollusca identical with those now living, and dicotyledonous plants.
The Eocene strata have been divided and sub-divided as follows, and mainly from the researches of Prestwich, and Edward Forbes:
Corbula Beds. ( Hempstead Beds.
| Freshwater and Middle
London (Plastic Clay).
Tertiaries. Thanet Beds.
| The Ilempstead Beds have by some geologists been regarded as Miocene.