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dence of scenes of life and activity when every other relic has utterly disappeared! But numerous as bird-footprints are—and they occur in ahundance at Storeton in Cheshire, Corncockle in Dumfriesshire, Cummingstone in Morayshire, Hildburghausen in Germany, and on the Connecticut in America—no traces of bird-bones have been detected save in a single instance, and that not altogether free from doubt, in the sandstones of the Connecticut. But what is doubtful in the Trias becomes obvious in the Oolite and Chalk, and the comparatively recent discovery of the skeleton of the archaiopteryx* (ancient bird) in the lithographic limestone of Solenhofen, confirms the fact that Bird-Life, whether existing or not in the primary periods, became at all events an established feature in the secondary ages. Yet so it ever appears with the great scheme of vitality; advancing slowly but incessantly, and displaying at every stage more complicated forms and higher functional activities!
Conformable to this progress, mammals also make their appearance during the secondary ages — scantily in the Trias, but more abundantly and unmistakably in the Oolite and Chalk. As might be expected, and in accordance with a progressional scheme, those mammals belong to the lower or marsupial orders—that is, to those which, like the opossum and kangaroo, are furnished with a marsupium, or external pouch in which they carry about their immature young. These marsupials or pouch-bearers stand lower in the scale than the true mammals that bring forth their
* This ancient bird, according to Professor Owen, was about the size of a rook, and differs from all known birds in having two free claws belonging to the wing, and also in having the vertebne of the tail (about twenty in number) free and prolonged as in mammals—each vertebrae supporting a pair of quill-feathers which give to the tail a long and vane-like appearance. This unique specimen (now in the British Museum) exhibits in its tail a retention of structure which is "embryonal and transitory in the modern representatives of the class Aves, and consequently a closer adhesion to the general vertebrate type."
young in a perfect state. They are sometimes termed ovoviviparous, and, so far as this function of gestation is concerned, hold an intermediate place, as it were, between birds and the ordinary mammalia. Numerous teeth and jaws of a small size (about that of a rat or rabbit) have been discovered, some indicating herbivorous, some carnivorous, and others insectivorous habits, but all apparently belonging to the same pouch-bearing orders. It is true that in the chalk marls some bones of a doubtfully higher character have been detected, but beyond these fragments nothing higher in the scale of Life than birds and marsupials is known to belong to the secondary ages.
Here then, during these secondary ages, which embrace a long period of the world's history, we have seas of moderate depth and broad shallow estuaries in which all the ordinary sediments were deposited—shelly and coralline limestones in the outer waters, muds and clays in the stiller recesses, and sands on the open shores. Here and there masses of rock-salt and gypsum accumulate in detached lagoons and sea-reaches; while during the oscillations of the land the swamp and forest growths of a genial climate are repeatedly submerged and converted into coal. We say genial climate, for the cycads, zamias, palms, tree-ferns, and broad-leaved pines (which are the prevailing forms) point to warm and equable conditions; while the frequent oscillations of the land are amply shown in the numerous seams of coal and "dirt-beds" or ancient soils on which the forest-growths had flourished for ages.* And while these genial conditions prevail over sea and land, both are equally exuberant with life—the former teeming with foraminifera, sponges, corals, encrinites, star-fishes, shell-fish of every order, fishes and reptiles; and the latter with gigantic ferns, reed-like grasses, cycads, zamias, palms, and pine-trees, which became the chosen food or shelter of numerous insects—of reptiles, terrestrial, arboreal, and aerial—of birds, and of marsupial mammals. What a busy panorama of life, growth, and decay is presented by these secondary ages! And not alone mere growth and decay, but development and progress; for during the long periods that elapsed between the commencement of the Trias and the close of the Chalk, thousands of forms became extinct—newer and higher ones taking their places, and at every stage approaching nearer and nearer to those of the Tertiary and Current epochs. So perceptible, indeed, is this approach, that it has been proposed to arrange the geological formations into two great divisions only—tbe "palceozoic, embracing all to the close of the Permian; and the neozoic, all from the commencement of the Trias up to the present day. But whatever may be the value of such arrangements, the fact of progression is everywhere obvious —so obvious, that even the non-scientific observer could have little difficulty in distinguishing between the fossil forms of the primary and secondary ages.
* One of the best known examples of an oolitic soil is the celebrated "dirt-bed" of Portland—an earthy, carbonaceous mass, replete with the roots and prostrate trunks of cycads, zamias, and other vegetation characteristic of and peculiar to those secondary formations. In fact, a genuine forest-mould, with its rotted leaves, fallen trunks, and imbedded rootstools.
Let those who refuse their assent to a plan of vital development only study for a day or two the magnificent collection of secondary fossils in our National Museum, or even peruse their figures as given in ordinary geological works; and if at all capable of comparing, they cannot fail to perceive the vast advance that has been made upon the primary or palaeozoic forms. Not only is there the introduction of birds and mammals formerly unknown, but the stamp impressed upon all the lower orders—corals, molluscs, crustacea, fishes, and reptiles — is that of greater complexity and specialisation. Let them next compare them with tertiary and existing forms, and note in these not only the further introduction of the true timber-trees and the higher birds and mammals, but also the still greater degree of specialisation both in form and function which characterises the whole; and unless blinded by prejudice or incapable of discernment, they cannot refuse assent that there has been a progress, and that this progress has taken place in a way so connected and definite as to lead to the unavoidable conviction of an all-pervading law of development.
As Economic Eepositories the secondary formations are year after year assuming greater importance. Not many years ago, building - stone, limestone, lithographic slabs, fuller's earth, rock-salt, gypsum, and chalk, were the principal products extracted; but now ironstone like that of Cleveland in Yorkshire, coal from many fields (Austria, India, Indian islands, Brazil, Virginia, Vancouver, and other regions), coprolites or phosphatic nodules for manure, hydraulic cements, and other substances are largely obtained, and as foreign surveys are extended, will in all likelihood be met with in still greater abundance. The geological mapping of the world, by competent authorities, is merely in its infancy;* but as this proceeds the secondary systems
* The survey of our own islands, though commenced many years ago, is not half completed; and those of our colonial possessions—Canada, the West Indies, India, Australia, and New Zealand — are merely in their first stages. The same may be said of other European countries, most of which have made some progress with their surveys, hut still feel the want of more minute and accurate information. The American States survey, begun with great ardour, has been finished only in a few instances; while with the geology of South America, Arctic America, Asia, and Africa, we have the slightest and most imperfect acquaintance. Till all these areas have been more thoroughly explored, it were presumptuous to dogmatise, and idle to speculate, either as to the scientific aspects or the economic importance of the several stratified systems.
are gradually revealing a larger amount of economic treasures, and exciting an interest more in keeping with that which has so long been attached to their paleeontological and purely scientific aspects. In corroboration of this we need only refer to such discoveries as the Cleveland ironstone, which within the last dozen years has wrought such a revolution on the aspects and industry of northern Yorkshire; to the deposits of rock-salt near Middlesborough on the Tees and in Antrim; and, above all, to the fact that the main coal-fields of India and the East are of secondary origin. How changed the aspect of opinion within the last thirty years, when our predecessors, generalising from their limited knowledge, regarded coal and iron as belonging alone to formations of earlier date, and sought for traces of their existence only in connection with these primary systems! But so it ever is; the more limited our acquaintance with nature and nature's operation, the more restricted our notions of her bounties, and the less prepared are we to avail ourselves of their benefits and amenities. It is only when mankind have taken the wider survey that they can arrive at sounder conceptions, and forego the conclusions they had drawn from their local and circumscribed experience.