The rocks which actually represent the Upper Cretaceous period divide themselves naturally into six series; but British and French geologists make some distinction: the former dividing them into i, Macstricht and Faxoe beds, said not to occur in England; 2, White Chalk, \s\\ flints; 3, White Chalk, \\t\o\it flifits; 4, Chalk Marl; 5, Upper Greensand; and 6, Gault. The latter four are divided by foreign geologists into i, Turo7iian; 2, Se7ionia7i; 3, 2?^;z/^;/.

The Gault is the lowest member of the Upper Cretaceous group. It consists of a bluish-black clay mixed with greensand, which underlies the Upper Greensand. Near Cambridge, where the Gault is about 200 feet thick, a layer of shells, bones, and nodules, called the *' Coprolite Bed," from nine inches to a foot thick, represents the Upper Greensand, and rests on the top of the Gault Clay. These nodules and fossils are extensively worked on account of the phosphatic matter they contain, and when ground and converted into superphosphate of lime they furnish a very valuable agricultural manure.

The Gault attains a thickness of about loo feet on the south-east coast of England. It extends into Devonshire, Mr. Sharpe considering the Black Down beds of that countty as its equivalents. It shows itself in the Departments of the Pas-de-Calais, the Ardennes, the Meuse, the Aube, the Yonne, the Ain, the Calvados, and the

Seine-Infe'rieure. It presents very many distinct mineral forms, among which two predominate: green sandstone and blackish or grey clays. It is important to know this formation, for it is at this level that the Artesian waters flow in the wells of Passy and Crenelle, near Paris. The glaucous chalk, or Upper Greensand, which is represented typically in the departments of the Sarthe, of the Charente-Inferieure, of the Yonne and the Var, is composed of quartzose sand, clay, sandstone, and limestone. In this fonnation, at the mouth of the Charente, we find a remarkable bed, which has been described as a submarine forest. It consists of large trees with their branches imbedded horizontally in vegetable matter, containing kidney-shaped nodules of amber, or fossiUsed resin.

The Turonian beds are so named because the province of Touraine, between Saumur and Montrichard, possesses the best-developed type of this strata. The mineralogical composition of the beds is a fine and grey marly chalk, as at Vitry-le-Frangois; of a pure white chalk, with a very fine grain, slightly argillaceous, and poor in fossils, in the Departments of the Yonne, the Aube, and the Seine- Inferieure; granular tufaceous chalk, white or yellowish, mixed with spangles of mica, and containing Ammonites, in Touraine and a part of the Department of the Sartlie; white, grey, yellow, or bluish limestone, inclosing Hippurites and Radiolites. In England the Lower Chalk passes also into Chalk Marl, with Ammonites, and then into beds known as the Upper Greensand, containing green particles of glauconite, mixed, in Hampshire and Surrey, with much calcareous matter. In the Isle of Wight this formation attains a thickness of loo feet. The Senonia?t beds take their name from the ancient Se7ioiies. The city of Sens is in the centre of the best-characterised portion oi this formation; Epernay, Meudon, Sens, Vendome, Royau, Cognac, Saintes, are the typical regions of the formation in France. In the Paris basin, inclusive of the Tours beds, it attains a thickness of upwards of 1,500 feet, as was proved by the samples brought up, during the sinking of the Artesian well, at Crenelle, by the borings.

In its geographical distribution the Chalk has an immense range; fine Chalk of nearly similar aspect and composition being met with in all directions over hundreds of miles, alternating in its lower beds

UPPER CRETACEOUS PERIOD, 3II

with layers of flints. In England the higher beds usually consist of a pure-white calcareous mass, generally too soft for building-stone, but sometimes passing into a solid rock.

The Danian beds, which occupy the summit of the scale in the Cretaceous formation, are finely developed at Maestricht, on the Meuse; and in the Island of Zeeland, belonging to Denmark \ where they are represented by a slightly yellowish, compact limestone, quarried for the construction of the city of Faxoe. It is slightly represented in the Paris basin at Meudon, and Laversines, in the Department of the Oise, by a white and often rubbly limestone known as pisolitic limestoiie. In this fonnation Ammo7iites Danicus is found. The yellowish sandy limestone of Maestricht is referred to the Danian type. Besides Molluscs, Polyps, and Polyzoa (Bryozoa), this limestone contains remains of Fishes, Turtles, and Crocodiles. But what has rendered this rock so celebrated was that it contained the remains of the great animal of Mcestrickt, the Maesasaurus.

At the close of the geological period, whose natural physiognomy we have thus traced, Europe was still far from displaying the configuration which it now presents. A map of the period would represent the great basin of Paris (with the exception of a zone of Chalk), the whole of Switzerland, the greater part of Spain and Italy, the whole of Belgium, Holland, Prussia, Hungary, Wallachia, and Northern Russia, as one vast sheet of water. A band of Jurassic rocks still connected France and England at Cherbourg — ^which disappeared at a later period, and caused the separation of the British Islands from what is now France.

Fig. 147.— Exogym conica. Upper Greensand and Gault, from Blackdown HilL

312

TERTIARY PERIOD.

A NEW organic creation makes its appearance in the Tertiary period; nearly all the animal life is changed, and what is most remarkable in this new development is the appearance, in larger numbers, of the great class of Mammifera. During the Primary period, Crustaceans and Fishes predominated in the animal kingdom; in the Secondary period the earth was assigned to Reptiles; but during the Tertiary period the Mammals were kings of the earth; nor do these animals appear in small number, or at distant intervals of time; great numbers of these beings appear to have lived on the earth, and at the same moment; many of them being, so to say, unknown and undescribed.

If we except the Marsupials, the first created Mammals would appear to have been the Pachyderms, to which the Elephant belongs. This order of animals long held the first rank; it was almost the only representative of the Mammal during the first of the three periods which constitute the Tertiary epoch. In the second and third periods Mammals appear of species which have now become extinct, and which were alike curious from their enormous proportions, and from the singularity of their structure. Of the species which appeared during the latter part of the epoch, the greater number still exist. Among the new Reptiles, some Salamanders, as large as Crocodiles, and not very distinct from existing forms, are added to the animal creation during the three periods of the Tertiary epoch. Chelonians were abundant within the British area during the older epoch. During the same epoch Birds are present, but in much fewer numbers than the Mammalia; here songsters, there birds of prey, in other cases domestic — or, rather, some appear to wait the yoke and domestication from man, the future supreme lord of the earth.

The seas were inhabited by a considerable number of beings of all classes, and nearly as varied as those now living; but we no longer find in the Tertiary seas those Ammonites, Belemnites, and

Hippurites which peopled the seas and multiplied with such astonishing profusion during the Secondary period. Henceforth the testaceous Mollusca approximate in their forms to those of the present time. The older and newer Tertiary Series contain fe;w peculiar genera. But genera now found in warmer climates were greatly developed within the British area during the earlier Tertiary times, and species of cold climates mark the close of the later Tertiaries.

What occurs to us, however, as most remarkable in the Tertiary epoch is the prodigious increase of animal life; it seems as if it had then attained its fullest extension. Swarms of testaceous Mollusca of microscopic proportions — Foraminifera and Nummulites — must have inhabited the seas, crowding together in ranks so serried that the agglomerated remains of their shells form, in some places, beds hundreds of feet thick. It is the most extraordinary display which has appeared in the whole range of creation.

Vegetation during the Tertiary period presents well-defined characteristics. The Tertiary flora approaches, and is sometimes nearly identical with, that of our days. "The class of dicotyledons shows itself there in its fullest development; it is the epoch of flowers. The surface of the earth is embellished by the variegated colours of" the flowers and fruits which succeed them. The white spikes of the Graminese display themselves upon the verdant meadows without limit; they seem provocative of the increase of Insects, which now singularly multiply. In the woods crowded with flowering trees, with rounded tops, like our oak and birch, Birds become more numerous. The atmosphere, purified and disembarrassed of the veil of vapour which has hitherto pervaded it, now permits animals with such delicate pulmonary organs to live and multiply their race.

During the Tertiary period the influence of the central heat may have ceased to make itself felt, in consequence of the increased thickness of the terrestrial crust. By the influence of the solar heat, climates would be developed in the various latitudes; the temperature of the earth would still be nearly that of our present tropics, and at this epoch, also, cold would begin to make itself felt at the poles.

Abundant rains would, however, continue to pour upon the earth enormous quantities of water, which would give rise to important rivers; new lacustrine deposits of fresh water were formed in great numbers; and rivers, by means of their afluvial deposits, began to form new land. It is, in short, during the Tertiary epoch that we trace an alternate succession of beds containing organic beings of marine origin, with others peculiar to fresh water. It is at the end of this period that continents and seas take their respective places as

we now see them, and that the surface of the earth received its present form. The Tertiary epoch, or series, embraces three very distinct periods, to which the names of Eocene^ Miocene^ and Pliocene have been given by Sir Charles Lyell. The etymology of these names is derived — Eocene, from the Greek t/«s, dawn^ and Ka.w6^, recent; Miocene, from ii-^'iov^ less, kuivSs^ recent; and Pliocene, from v\dov, more, Kaiuos^ recent; by which it is simply meant to express, that each of these periods contains a minor or greater proportion of recent species (of Testacea), or is more or less remote from the dawn of life and from the present time;* the expressions are in one sense forced and incorrect, but usage has consecrated them, and they have obtained universal currency in geological language, from their convenience and utility. * Lyell's *' Elements of Geology," p. 187.

Fig. 148.— Trigonia jnargaritacea. (Living form.)

315

THE EOCENE PERIOD.

During this period terra finna has vastly gained upon the domain of the sea; furrowed with streams and rivers, and here and there with great lakes and ponds, the landscape of this period presented the same curious mixture which we have noted in the preceding age, that is to say, a combination of the vegetation of the primitive ages with one analogous to that of our own times. Alongside the birch, the walnut, the oak, the elm, and the alder, rise lofty palm-trees, of species now extinct, such as Flabellaria and Palinacites; with many evergreen trees (Conifers), for the most part belonging to genera still existing, as the firs^ the pines, the yews, the cypresses, the junipers, and the thuyas or tree of life.

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