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and gas distribution, telegraphic wires, and steamships, are the giant offspring of her coal - fields; and wherever the sound of these is heard, or their influences felt, new activities and industries are awakened, and on industry and commerce are ever founded the surest hopes of civilisation and refinement. Strange, as we have before remarked, that the mere physical operations of the earth's remotest ages should be so intimately associated with the industrial and intellectual operations of the present! Inexplicable, if creation were not the unfolding of a great moral as well as of a great physical scheme—a scheme in which every element and operation in time past as in time present plays an essential part, and from which not a jot or tittle could be abstracted without marring the symmetry and perfection of the whole.

THE SECONDAEY AGES.

THE SECONDARY AGES, EMBRACING THE NEW RED SANDSTONE, OOLITE, AND CHALK SYSTEMS—THEIR PLACE IN GEOLOGICAL HISTORY— COMPOSITION AND SUCCESSION OF THEIR STRATA—PHYSICAL CONDITIONS UNDER WHICH THEY WERE FORMED—THEIR FOSSIL FLORA AND FAUNA—EXCESS OF CHAMBERED SHELLS—EXUBERANCE OF REPTILIAN LIFE—CURIOUS PHASE OF BIRD-LIFE — THE ARCH.ffiOPTERIX—LIFE - CONDITIONS OF THE SECONDARY PERIODS— ECONOMIC PRODUCTS OF THE SECONDARY SYSTEMS—SECONDARY COAL-FIELDS—THEIR GROWING IMPORTANCE.

When the earlier geologists arranged the rocks of the earth's crust into Primary or first-formed, Secondary or secondformed, and Tertiary or third-formed, they made a most important improvement in geological classification; and though a somewhat different meaning is now attached to these terms, they are still retained in the nomenclature of the science as general and convenient designations. Accepting Trimary merely in the sense of early or ancient, it embraces all the stratified systems prior to the New Eed Sandstone; while Secondary, on the other hand, refers to the New Eed Sandstone, the Oolife and Chalk. Even this New Eed Sandstone, when critically examined, is found to differ widely in its fossils—the lower portion containing palaeozoic forms closely related to those of the Coal-measures, and without much error may be considered as the close or capping of that system; while the upper portion is characterised by mesozoic forms, or such as have a closer relationship to those of the Oolite and Chalk. In this way the " New Eed Sandstone" of our forefathers has been separated into two distinct systems—the "Permian" or Lower New Eed, so called by Sir Eoderick Murchison because typically displayed in the province of Perm in Eussia; and the "Triassic" or Upper New Eed, so named by the German geologists because consisting of three well-marked series of strata, the Bunter or variegated sandstone, the Muschelkalk or shell-limestone, and the Keuper or copper-marls. Adopting this view—and it is more by nature of the fossils than by the character of the sediments that the relative antiquity of strata can be satisfactorily determined—the secondary ages, which form the subject of the present sketch, comprehend the Triassic, Oolitic, and Chalk systems, whose chronological place will be best understood, perhaps, by a glance at the annexed tabulation:— Cainozoic

'Quaternary or Recent Accumulations.
, Tertiary.

or
Tertiary.
Mesozoic ( Cretaceous or Chalk,

or < Oolitic or Jurassic.

Secondary. ( Triassic or Upper New Red Sandstone.

[ Permian or Lower New Red Sandstone.

Carboniferous or Coal.
I Old Red Sandstone and Devonian.

Silurian.

Cambrian,
i Laurentian.

Paleozoic

or

Primary.

These secondary systems— the Trias, Oolite, and Chalk— hold a middle place, as it Vere, in geological history, less obscure than the primary, but still not so obvious either in their vital or geographical arrangements as the tertiary and recent. The mode in which their strata have been aggregated is for the most part apparent, and their fossils, though differing widely in genera and species from existing forms, have still more of a new-world aspect about them, and the palaeontologist feels he has less difficulty in establishing their botanical and zoological relations. Unless in highly igneous centres, few of the strata have suffered much metamorphism; the areas and boundaries of the seas of deposit are much more apparent; and birds and mammals, unknown in previous systems, are now met with in some abundance. Of course, as the secondary ages embrace several systems and formations, there will necessarily be considerable difference, both in rocks and fossils, between its respective series; but notwithstanding these differences there is still similarity sufficient to enable us to treat them as a great group, or rather a's occupying a continuous and connected portion of the earth's geological history. And after all, it is only by groupings and generalisations of this kind that the nonscientific reader can be expected to catch a glimpse of worldhistory, the details and reasonings of which must be worked out by the slow and patient research of the professional inquirer.

The earliest of these Secondary systems, we have said, is the Trias, a series of reddish-coloured sandstones, shelly limestones, and saliferous or salt-yielding marls; the second, the Oolite, a series of calcareous freestones, clays, and shales, with occasional coals and ironstones; and the third, the Chalk, so notably composed in the south of England of that white, soft, earthy limestone we call " chalk," and its underlying clays and greensands. With the exception of a subordinate series of strata that lie between the Oolite and Chalk, and known as the "Wealden" from their occurrence in the wolds or woodlands of Kent and Sussex, all the strata of these secondary formations are eminently marine, and are charged throughout with marine organisms. The Wealden sands, sandstones, and clays point more to estuarine conditions, and where they occur the coals and lignites of the Oolite and Chalk indicate the existence of land-surfaces; but all the other strata—the shelly and coralline lime*stones and sandstones, the saliferous marls, the shales and clays* replete with the exuviae of shell-fish, crustacea, and fishes—are strictly sea-formed, some littoral or along-shore, and others pelagic or in deeper waters. This marine origin is pre-eminently observable in the Trias and Chalk, and it is only in these oolitic districts where coal and ironstone are found that we have evidence of estuarine and terrestrial conditions of formation.- Of course we are here alluding

* A better idea of the composition of these Secondary Systems may be obtained, perhaps, by a perusal of the annexed tabulation :—

Chalky marls and thin-bedded limestones. Chalk rock, with and without imbedded flints. Chalk Greensands and cherty limestones.

or 'Blue tenacious clays, locally known as "gault"

Cretaceous. ] or"golt."

Green and ferruginous sands, sandstones, and cherty limestones. f Wealden clays, sands, and flaggy sandstones. Upper Oolite—consisting of fine-grained oolitic limestone with interbedded clays and bituminous shales (coals). Middle Oolite—consisting of coarse-grained shelly and coralline limestone, with blue clays and shelly calcareous grits. J Lower Oolite—consisting of coarse shelly limestone and grits; thick-bedded blue clays (coals); thick-bedded sandy oolitic limestone; flaggy grits and marls; and calcareous freestone. Upper Lias—consisting of dark bituminous shales

and indurated marls or marlstone. Lower Lias—dark laminated limestones and clays, bands of ironstone, layers of jet and coal, calv careous sandstones.

/ Keuper—consisting of variegated marls, sandy layers, limestone layers, gypsum, and rockTriassic salt.

or { Muschelkalk— grey shelly limestone, with marl

Upper New Red. I partings and beds of magnesian limestone.

I Bunter—soft variegated sandstones; coarse-grained
V grits and conglomerates.

Oolitic

Jurassic.

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