river, but even to a surprising number of the marine mollusca, articulata, and radiata. Our knowledge, therefore, of the living creation of any given period of the past may be said to depend in a great degree on what we commonly call chance, and the casual discovery of some new localities rich in peculiar fossils may modify or entirely overthrow all our previous generalizations, so long as they are based on the supposed nonexistence at former epochs of the fossil representatives of large families or classes of plants and animals.

Tertiary Fossils.

When we contrast the botany and zoology of primary and secondary strata with those of tertiary formations, it is more especially incumbent on us to make due allowance for a comparatively deficient acquaintance with the ancient deposits, which are more and more exclusively marine in proportion as we depart farther from those periods during which our existing continents were built up. They are more marine, not because the ocean was more universal in times past, but because, when we carry back our retrospect to epochs so distant that entire continents have been since submerged, we are less favourably placed for exploring strata thrown down in lakes and estuaries, or near the shore. In studying the tertiary strata, as I before remarked, we have opportunities of becoming more thoroughly acquainted with the remains of the flora and fauna which flourished in a great variety of stations; and besides, in these more modern rocks the imbedded fossils are less obliterated by the destroying hand of time. If we conceal or extenuate such circumstances when we argue with an opponent who believes that the primary or secondary fauna was as highly developed as the tertiary, we take an unfair advantage of him; not duly conceding how much the chances of finding examples of terrestrial mammalia are on our side. "We throw with loaded dice," to borrow an expression of Dr Fleming's, in a controversy respecting the evidences of a tropical climate at more ancient periods.

Of the tertiary mammalia, the oldest yet found, perhaps, are those of the lower eocene, occurring in the London clay of Sheppey and the sand of Kyson, near Woodbridge. Although the species are as yet few in number, the quadru

mana are represented by the Macacus Eocenus, the marsupials by the Didelphys Colchesteri, the pachyderms by the Hyracotherium cuniculus; and these types alone indicate as full a development of the mammalia as that exhibited by the middle eocene strata of Hordwell Cliff, the Isle of Wight, and the gypsum of Montmartre, near Paris, where a more numerous assemblage of species has been found. As the mollusca of the upper and lower eocene differ considerably, analogy leads us to expect that the species of mammalia of these two periods (the lower and middle eocene) will differ still more widely. On the other hand, the fossil quadrupeds of the Limagne d'Auvergne, which I refer to an upper eocene group (although some able geologists class them as lower miocene), present another fauna; and a fourth set of mammalia belong to the era of the Faluns of Touraine. Since the falunian epoch the pliocene species came into existence, and a large part of these also have in their turn become extinct, giving place to the mammalia now co-existing with man.

If we desire to satisfy ourselves of the superior facilities we enjoy in studying the tertiary as compared to the secondary mammalia, we have only to reflect on one advantage which a collector of newer pliocene fossils enjoys over one who shall confine his investigations to eocene or miocene remains. In Owen's table of the fossil mammals of the British Isles, the longest list of species is that derived from cavern deposits. All these he refers, and I believe correctly, to the newer pliocene period. We know nothing of the bones which were enclosed in the stalagmite of caverns in the older pliocene or miocene or eocene eras; and the same remark holds good in all those parts of France, Belgium, and Germany which I have visited, and equally so, I believe, in regard to the caves of Brazil, Australia, and New Zealand, from which the bones of extinct mammalia and birds have been derived. But if we remain so ignorant of the inhabitants of caverns in all the tertiary periods except the latest, how little knowledge can we expect to derive from a similar source respecting the terrestrial fauna, when we carry back our inquiries to the Wealden or Carboniferous epochs! We are as well assured that land and rivers then existed, as that they exist now; but it is evident that even a slight geographical revolution or trans

ference of the position of land and sea tends rapidly to diminish our chances of learning what mollusca or mammalia may then have inhabited the land.

Geological Age of Man.

Yet, small as may be the progress hitherto made in deciphering the records of the tertiary periods, we seem entitled to declare that, during several great revolutions in the mammalia, probably not less than five, there has been no step whatever made in advance, no elevation in the scale of being; so that had man been created in the lower eocene era, he would not have constituted a greater innovation on the state of the animate creation previously established, than now, when we believe him to have begun to exist at the close of the pliocene.

Antecedently to investigation, we might reasonably have anticipated that the vestiges of man would have been traced back at least as far as those modern strata in which all the testacea and a certain number of the mammalia are of existing species, for of all the mammalia the human species is the most cosmopolite, and perhaps more capable than any other of surviving considerable vicissitudes in climate and in the physical geography of the globe. How far the interior of Asia, the supposed cradle of our race, may hereafter afford geological evidence of higher antiquity than can be deduced from European monuments, we have yet to learn. The observations recently made by Dr Abich on the changes of level going on in the Caspian; the periodical oscillations of level in that sea, due principally to subterranean movements; the shifting of the position of its waters, partly by the encroachment of deltas on one side and the overflowing of the land in other directions; the buildings now seen under water while others are above the sea-level, and yet, like the temple of Serapis, having been drilled by perforating mollusks, bear the marks of former submergence-these proofs of recent changes, coupled with the evidence obtained by MM. Murchison and De Verneuil, of the vast extent of a marine or brackish-water Aralo-Caspian limestone hundreds of feet above the level of the Mediterranean, may encourage us to hope that we may hereafter be able to find a geological date for the origin of

man, less vague than that which we can at present assign to the event. But so far as our interpretation of physical movements has yet gone, we have every reason to infer that the human race is extremely modern, even when compared to the larger number of species now our contemporaries on the earth.

In fluviatile deposits, such as the loess of the Rhine and the Mississippi, where the land and freshwater shells are of living species, we find no human bones or articles fabricated by man; nor in the elevated tufaceous strata near Naples, or the raised beaches of Norway, or the brackish-water strata several hundred feet high, bounding the Baltic, nor in the stratified glacial drift, in all of which marine shells are imbedded, referable, with few exceptions, to living species. I have explained my reasons for not assenting to the alleged antiquity of certain human bones, supposed to have been as ancient as the Mastodon and Megalonyx, in the loess near Natchez on the Mississippi.* In cave deposits which contain the bones of extinct quadrupeds, mixed with the remains of a small number of recent species of the same class, no human skeletons or fabricated articles have been found. There are, indeed, some few alleged exceptions to this rule, but by no means sufficiently authenticated to prove that man co-existed with an extinct mammiferous fauna; for the possibility of human remains having become subsequently mingled with those of older date, whether by natural causes or by burial in the stalagmite and alluvium of caverns, must be taken into account. In South America no less than 800 caves were explored by those indefatigable naturalists, Lund and Clausen, and they obtained the bones of 101 species of mammalia belonging to 50 genera, a fauna more rich and varied than that now inhabiting the same country. Among all these, only one species of quadruped could be identified with the recent. After ransacking so many hundred caves they met with human bones in six only, and in one of these alone were they mixed with the remains of extinct animals in such a manner as to seem to imply that they had belonged to the same epoch. In this one example, the bones are said

* See my Second Visit to the United States, vol. ii., p. 196.

to have been in the same state or condition as those of the extinct quadrupeds, the human skull being referable to the same type as that of the American Indian of Brazil. But although such fossils may have been very ancient, historically speaking, we must wait for additional testimony before we allow this single instance to convince us that the human race co-existed with the extinct Brazilian and Pampean fauna, in which case it must have outlived one assemblage of mammalia and witnessed the coming in of another, perfectly distinct. Nor can we reconcile the facts of the case with the hypothesis that man was the exterminating agent of the quadrupeds which have disappeared. Not only have the Megatherium, Auchenia, Mastodon, and other huge quadrupeds died out since these caves were filled with fossil bones, but several also of the contemporary minute creatures, such as seven species of bats and thirty-two of Glires, and many small opossums. The five extinct apes, moreover, described by Lund, were not associated with fossil bones of the living species of apes which now abound in Brazil, and in the extirpation of which man has made but little progress.

As all the vertebrate, and nearly all the invertebrate eocene fossils belong to species now no more, we could never reasonably expect the remains of man to form part of an eocene fauna. Previously to experience, the utmost that analogy entitled us to look for in rocks of such high antiquity was the occurrence of some dominant species, different from the human, yet holding a corresponding position in the then living creation. Neither the osseous remains nor the handiwork of such a being have ever been detected; and as I before stated, although there have been, since the lower eocene epoch, so many complete changes in the species of warm-blooded quadrupeds inhabiting the land, no progress whatever has been made in filling up the chasm which now separates man from the inferior animals. In that rich fauna, probably of miocene date, brought to light by the exertions of Dr Falconer and Major Cautley, in the SubHimalayan or Sewâlik Hills, there are many extinct species

*For an abstract of Lund's discoveries, see Archiac, Hist. des Progrès de la Géol., tom. ii., p. 385.