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southerly and warmer latitudes. But the mere lying within more southerly latitudes does not altogether determine the nature of a climate or the geniality of external conditions. Insular or continental arrangement of the landmasses, altitude above the sea-level, the direction of mountain-ranges and valleys, the amount of rainfall, and the set of ocean-currents from colder or warmer regions, all influence less or more the climate of a country; and these, as affecting the future lands of our globe, we have no means whatever even of guessing at. All that we know for certain is, that the existing continents are gradually passing into newer forms and dispositions, and that these dispositions must of necessity be accompanied by other climates and by other vegetable and animal appointments. All that we can offer as a legitimate geological inference is, that the land-masses more immediately succeeding the existing will be more subtropical and tropical in their position, and, cceteris paribus, more congenial in their physical surroundings.
In the third place, if the present continents and islands are to be superseded by others possessed of different external conditions, it follows that these newer lands must be characterised by different distributions of plants and animals. At present it is presumed that each plant and animal occupies the station and habitat best suited to its growth and perfection; but if these situations be interfered with, no matter how slowly, certain races must succumb to the change, while others will usurp their places. Were the future continents, for example, to be gradually evolved within lower latitudes, their flora and fauna would as gradually assume a tropical aspect—existing forms, on the other hand, disappearing stage by stage with the external conditions to which they had been originally adapted. The disposition of the existing continents is mainly longitudinal, hence they are subjected to extreme diversity of climate, and consequent variety of vegetable and animal life; were the lands of the future to be arranged more latitudinally, a greater uniformity of climate would prevail, and with this uniformity a corresponding sameness in the specific distribution of vitality. The existing land-masses bulk most largely in the northern hemisphere; we can readily perceive how different the climatic and vital arrangements of the globe were they mainly disposed in the southern. The tradewinds, tides, and oceanic currents—the great modifiers of climate—are interrupted in their normal continuity by the longitudinal disposition of the existing continents, and thrown into minor and complex deviations; how different the result did the disposition of the land permit them to revolve in simple and unbroken continuity! On the whole, it may be safely assumed, that the greater the difference between future and existing continents in position and climate, the greater will be the difference in their vital appointments; and thus the future, from those physical causes alone, would present a totally different life-picture from the present. There might be no new creations nor developments, but there would be extensive re-arrangements and re-assortments of the existing—extermination of certain genera and species and increase of others, and along with these a corresponding redistribution of the varieties of the human family itself. "We have said, "there might be no new creations nor developments," and yet it is difficult to conceive of any extensive alterations in the distribution of sea and land, without associating with them newer phases of vegetable and animal existence. In the history of the past, new developments of life are so intimately associated with geographical changes, and every newer formation so distinctively characterised by its own peculiar and higher species, that whatever the law by which the succession of vitality on our globe is governed, external conditions are undoubtedly one of its principal factors; and thus, with other distributions of sea and land, we may anticipate not only other distributions, but other and newer phases of their flora and fauna.
But, fourthly, if we are to be guided in our speculations respecting the future by our knowledge of the past, another and more important element comes to be considered, and that is, the continuous ascent from lower to higher lifeforms which is traceable throughout the whole of the geological periods. If there has been such an ascent throughout the past by some process of development, or whatever it may be, the reasonable presumption is, that the same process will continue to manifest itself in the future. It is by no means asserted that investigators have anything like completed the geological record; but all that has been done, whether in Europe, Asia, America, or Australia, tends to the establishment of an ascent in the main—from the cryptogam to the phanerogam, from the invertebrate to the vertebrate; from the endogen to the exogen, from the fish to the reptile, from the reptile to the bird, and from the bird to the mammal. Even within these great sections there has been a corresponding ordinal advance; and although new discoveries occasionally compel us to modify our views as to the time when certain orders and genera made their first appearance, still no discovery has ever been made that militates in the least against the general doctrine, that the more lowly organised have regularly preceded the higher and more specialised orders. We say "regularly preceded," for though systematists are occasionally puzzled with apparent breaks in the continuity, these breaks are either the result of local obliterations, or they arise from limited and imperfect observation. Such having been the progressive evolution of life during the long and physically-varying cycles of the past, the geologist is surely entitled to presume that a similar evolution will continue to mark the onward course of creation.
It is true, it may be argued, and indeed has been argued, that the system of Life has culminated in the present epoch, and is, consequently, subject to no further development; and if it has not so culminated, that new races ought now and then to be making their appearance. Such rea soning, however, is altogether at variance with the slow and gradual evolution of events as impressively taught by Geology. During the past, well-defined genera and orders make their appearance only after the lapse of ages; and two thousand or twenty thousand years of the current epoch may be too short a period for the full development of new and higher races. All that seems necessary for our argument is, that physiology can prove a tendency to variations in existing genera and species; and if such a tendency can be demonstrated, no matter how slight and slow, the widest subsequent divergence, even to the extent of new families and orders, is only a question of time and continuation. This is all that Geology contends for; and surely the variations in plants and animals which are continually taking place under change of external condition and under the influence of culture and domestication, must be sufficient to convince every mind capable of ordinary reasoning, that the susceptibility to newer developments is a quality as operative now as during any of the former epochs. It is vain to argue that no introduction of newer forms has been witnessed during the last three or four thousand years of human history. It is little more than half a century since such questions began to attract the attention of philosophers; and all that went before—erroneous notions of natural history, limited acquaintance with the geography of the world, ignorance of geology, and total absence of all reliable record — renders any arguments founded on this ground utterly idle and worthless. If vast physical changes have passed unmarked by our ancestors, what marvel need there be that the minuter phenomena of vital variations should have wholly escaped their attention 1 If the variations, descent, and dispersion of the human family be a matter of doubt and uncertainty to historians and ethnologists, what marvel need there be that the varieties, descent, and dispersion of the lower races should have passed unnoticed and even unsuspected 1 But if the introduction of new genera and species cannot be positively proven, we know that numerous forms have disappeared from certain localities, and that several (the dinornis, aepiornis, dodo, solitaire, great auk, rhytina, &c), within a comparatively recent period, have become altogether extinct. As extinction and creation ever went side by side in the past, so the fair presumption is that extinction is attended by a similar creation in the present. The minutest scrutiny can detect no decay in the physical accompaniments of life, no decline in the powers of vitality itself, and no change whatever in any of its discoverable relations to external nature; and surely on these, as on all the grounds formerly mentioned, we are entitled to believe in a continuance of vital development, as firmly as in a continuance of the physical changes which are daily and hourly taking place around us. The one may be less perceptible than the other, but not on that account the less real; slower in their rate of progress, but not the less certain and continuous.
Such a progression being granted, the Life of the future must differ from that of the present, as that of the present differs from all that went before. Old genera and species must pass away, and newer and higher ones take their places. As the ratio of development among the different classes and orders, both of plants and animals, seems