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And also ap
necessity to general life, it might seem worthy of incessant Divine intervention, yet it is in fact accomplished automatically.
Of past organic history the same remark may be made. The condensation of carbon from the air, and its inclusion in the strata, constitute the chief epoch in the organic
life of the earth, giving a possibility for the pearances and appearance of the hot-blooded and more in
tellectual animal tribes. That great event was
occasioned by the influence of the rays of the sun.
And as such influences have thus been connected with the appearance of organisms, so likewise have they been concerned in the removal. Of the myriads of species which have become extinct, doubtless every one has passed away through the advent of material conditions incompatible with its continuance. Even
now, a fall of half-adozen degrees in the mean temperature of any latitude would occasion the vanishing of the forms of warmer climates, and the advent of those of the colder. An obscuration of the rays of the sun for a few years would compel a redistribution of plants and animals all over the earth; many would totally disappear, and everywhere new comers would be seen. The permanence of organic forms is altogether dependent
on the invariability of the material conditions of organisms under which they live. Any variation therein,
no matter how insignificant it might be, would bility of external condi. be forthwith followed by a corresponding vari
ation in the form. The present invariability of the world of organization is the direct consequence of the physical equilibrium, and so it will continue as long as the mean temperature, the annual supply of light, the composition of the air, the distribution of water, oceanic and atmospheric currents, and other such agencies remain unaltered, but if any one of these, or of a hundred other incidents that might be mentioned, should suffer modification, in an instant the fanciful doctrine of the immutability of species would be brought to its true value. The organic world appears to be in repose, because natural influences have reached an equilibrium. A marble may remain for ever motionless upon a level table; but let the
due to immo
surface be a little inclined, and the marble will quickly run off. What should we say of him, who, contemplating it in its state of rest, asserted that it was impossible for it ever to move ?
They who can see no difference between the race-horse and the Shetland pony, the bantam and the Shanghai fowl, the greyhound and the poodle dog, who altogether deny that impressions can be made on species, and see in the long succession of extinct forms, the ancient existence of which they must acknowledge, the evidences of a continuous and creative intervention, forget that mundane effects observe definite sequences, event following event quence of conin the necessity of the case, and thus constitu- ditions is folting a chain, each link of which hangs on a pre- derly organic ceding, and holds a succeeding one. Physical changes. influences thus following one another, and bearing to each other the inter-relation of cause and effect, stand in their totality to the whole organic world as causes, it representing the effect, and the order of succession existing among them is perpetuated or embodied in it. Thus, in those ancient times to which we have referred, the sunlight acting on the leaves of plants disturbed the chemical constitution of the atmosphere, gave rise to the accumulation of a more energetic element therein, diminished the mechanical pressure, and changed the rate of evaporation from the sea, a series of events following one another so necessarily that we foresee their order, and, in their turn, making an impression on the vegetable and animal economy The natural influences, thus varying in an orderly way, controlled botanical events, and made them change correspondingly. The orderly procedure of the one must be imitated in the orderly procedure of the other. And the same holds good in the animal kingdom; the recognized variation in the material conditions is copied in the organic effects, in vigour of motion, energy of life, intellectual power.
When, therefore, we notice such orderly successions, we must not at once assign them to a direct intervention, the issue of wise predeterminations of a voluntary agent; we must first satisfy ourselves how far they are dependent on mundane or material conditions, occurring in a definite
Universal control of
agents over organisms.
and necessary series, ever bearing in mind the important principle that an orderly sequence of inorganic events necessarily involves an orderly and corresponding progression of organic life. To this doctrine of the control of physical agencies over
organic forms I acknowledge no exception, not
even in the case of man. The varied aspects he physical
presents in different countries are the necessary
consequences of those influences. He who advocates the doctrine of the unity of the human race is plainly forced to the admission of the absolute control of such agents over the organization of man, since the originally-created type has been brought to exhibit very different aspects in different parts of the world, apparently in accordance with the climate and other purely material circumstances. To those circumstances it is scarcely necessary to add manner of life, for that itself The case of arises from them.
The doctrine of unity demands as its essential postulate an admission of the paramount control of physical agents over the human aspect and organization, else how could it be that, proceeding from the same stock, all shades of complexion in the skin, and variety in the form of the skull, should have arisen? Experience assures us that these are changes assumed only by slow degrees, and not with abruptness ; they come as a cumulative effect. They plainly enforce the doctrine that national type is not to be regarded as a definite or final thing, a seeming immobility in this particular being due to the attainment of a correspondence with the conditions to which the type is exposed. Let those conditions be changed, and it begins forthwith to change too. I repeat it, therefore, that he who receives the doctrine of the unity of the human race, must also accept, in view of the present state of humanity on various parts of the surface of our planet, its necessary postulate, the complete control of physical agents, whether natural, or arising artificially from the arts of civilization and the secular progress of nations toward a correspondence with the conditions to which they are exposed.
To the same conclusion also must he be brought who advocates the origin of different races from different
centres. It comes to the same thing, whichever of those doctrines we adopt. Each brings us to the admission of the transitory nature of typical forms, to their transmutations and extinctions.
Variations in the aspect of men are best seen when an examination is made of nations arranged in a northerly and southerly direction; the result is such as Human variawould ensue to an emigrant passing slowly along a meridional track; but the case would be quite different if the movement were along a parallel of latitude. In this latter direction the variations of climate are far less marked, and depend much more on geographical than on astronomical causes. In emigrations of this kind there is never that rapid change of aspect, complexion, and intellectual power which must occur in the other. Thus, though the mean temperature of Europe increases from Poland to France, chiefly through the influence of the great Atlantic current transferring heat from the Gulf of Mexico and tropical ocean, that rise is far less than would be encountered on passing through the same distance to the south. By the arts of civilization man can much more easily avoid the difficulties arising from variations along a parallel of latitude than those upon a meridian, for the simple reason that in that case those variations are less.
But it is not only complexion, development of the brain, and, therefore, intellectual power, which are thus affected. With difference of climate there must be differences of manners and customs, that is, differences in the modes of civilization. These are facts which deserve our Their politi-' most serious attention, since such differences are cal result. inevitably connected with political results. If homogeneousness be an element of strength, an empire that lies east and west must be more powerful than one that lies north and south. I cannot but think that this was no inconsiderable cause of the greatness and permanence of Rome, and that it lightened the task of the emperors, often hard enough, in government. There is a natural tendency to homogeneousness in the east and west direction, a tendency to diversity and antagonism in the north and south, and hence it is that government under the latter circumstances will always demand the highest grade of statesmanship.
Nature of transitional forms.
The transitional forms which an animal type is capable of producing on a passage north and south are much more numerous than those it can produce on a passage east and west. These, though they are truly transitional as
respects the type from which they have proceeded, are permanent as regards the locality in
which they occur, being, in fact, the incarnation of its physical influences. As long, therefore, as those influences remain without change the form that has been produced will last without any alteration. For such a permanent form in the case of man we may adopt the designation of an ethnical element. An ethnical element is therefore necessarily of a de
pendent nature; its durability arises from its change in an perfect correspondence with its environment.
Whatever can affect that correspondence will
touch its life. Such considerations carry us from individual man to groups of men or nations. There is a progess for races of men as well marked as the progress of one man. There
are thoughts and actions appertaining to specific Progress of
periods in the one case as in the other. Withthat of indivi- out difficulty we affirm of a given act that it
appertains to a given period. We recognize the noisy sports of boyhood, the business application of maturity, the feeble garrulity of old age. We express our surprise when we witness actions unsuitable to the epoch of life. As it is in this respect in the individual, so it is in the nation. The march of individual existence shadows forth the march of race-existence, being, indeed, its representative on a little scale.
Groups of men, or nations, are disturbed by the same accidents, or complete the same cycle as the individual. Communities,
Some scarcely pass beyond infancy, some are like families, destroyed on a sudden, some die of mere old bers in differ- age. In this confusion of events, it might seem ent stages of altogether hopeless to disentangle the law which
is guiding them all, and demonstrate it clearly. Of such groups, each may exhibit, at the same moment, an advance to a different stage, just as we see in the same family the young, the middle-aged, the old. It is thus