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branches. To guard against some of this risk, the skull, the most exposed part, is found to exhibit more than usual defence against injury. It is more cellular than is usual with other animals, and the inner and stronger plate is covered with an outer table and intermediate walls, to resist a sudden and violent shock.
Thus does it appear, that, at a very recent geological period, and perhaps not long before the actual introduction of man upon the earth, a multitude of strange and monstrous animals tenanted various districts; that each group was, then, as it is now, distinct from the rest, although so organized as to perform the same part in nature; and yet more, that each group possessed certain peculiar characters, exhibiting a relation with the animals still inhabiting the same districts, although the actual species are greatly changed, being modified in form, in proportions, and in habits. It would not be easy to imagine sets of phenomena more instructive, or more suggestive of new ideas and new views of creation; nor could any plan that we can conceive have indicated so clearly the uniformity of action, and the multitude of different means used to bring about the same great end. We shall consider in the next chapter the general conclusions that are suggested from this study of ancient nature.
GENERAL CONSIDERATIONS CONCERNING THE RESULTS OF GEOLOGICAL INVESTIGATION.
No one can properly consider the nature of geological researches, and the extent to which they indicate the ancient history of the globe and its inhabitants, without being struck by the simplicity and grandeur of the great plan of creation, and the adaptation of certain typical forms of organic life to a vast variety of different conditions, examples of which seem to have been introduced in regular order from the beginning of the world till now. In the preceding pages I have endeavoured to give, in the way of narrative, an idea of some detached but characteristic events of this history, and a number of sketches of the different epochs, or times when the conditions were most peculiar and most instructive.
In carrying out this object, however, I have frequently been forced to dwell rather upon the differences than the analogies that may be traced in the structure and adaptation of successive groups, and have directed attention so often, and in so marked a manner, to these differences, that some of my readers perhaps might over-estimate their importance, did I not now, in summing up the nature and value of the evidence already given in detail, explain how far such an impression may be considered correct. In the present concluding chapter, therefore, I propose to
take a general view of the whole subject, tracing as far as I am able the gradual development of life upon the globe.
Now a very superficial glance at general natural history will show, that however great the difference may be between the groups characteristic of any two geological periods at the same spot a difference, therefore, corresponding to a lapse of time-the distinction is equally marked at the present day in living groups with respect to space. Whatever, also, may have been the law anciently in force with reference to the succession of organic beings on the earth, and the introduction of new ones, that law, so far as we can tell, is permanent and uniform.
It appears, therefore, that a vast and comprehensive plan, still perhaps only partially unfolded, marks at once the infinite wisdom, the infinite power, and the infinite goodness of the Creator; and we may also conclude, that this method of action, or, if we will so call it, this law, may involve in its vast compass, not merely our own planet, but some or all of those orbs which circle round our sun, and perhaps, also, those unnumbered systems, which, like our own, are in motion through space. It is possible that all these bodies may in their progress exhibit an analogous method of development, consisting of the elaboration of series of groups, alike and yet different, each perfectly adapted to its purpose in its own way, and each having direct reference to all the rest.
It should, however, be distinctly understood, that there is not the slightest reason to suppose any actual repetition of the same plan. The evidence we have on the subject would rather lead us to conclude the contrary; but there may still be that amount of analogy which involves unity of plan.
I am quite prepared to admit that the advance of accurate scientific knowledge may be so considerable as to enable man at some future day to comprehend not only a few of the details, but even the general nature of this great plan of development. But he is certainly not yet in a condition to perceive the bearing of all those facts which are presented for his study, or to obtain a comprehensive view of the broad generalisations they involve; and in the attempt to include them within the compass of his imagination, and express their true relation in language, he has hitherto always failed. Convinced as I am of this, I offer with great diffidence those general conclusions on the subject in question which I have to suggest; and if I should be myself accused of speaking less cautiously or more dogmatically than may seem fit, I can only repeat this expression of my earnest endeavour to avoid such a form of speech. On the other hand, while I would not wish to blame others for giving decided expression to their own views, I would still caution my readers against the premature and unwise attempts that have been made by some authors to explain and bring within the compass of an assumed law of development the obscure and isolated phenomena hitherto observed and apparently bearing on this subject,* whatever those views may be.
If, from the study of fossils, we seem to attain any definite notions concerning the general plan of creation, these, it must be remembered, are only valuable so far as they can bear comparison with
*The law of development to which I here allude, supposes the successive elaboration of organic beings, each new form exhibiting higher or more complex organization.
observations concerning existing nature, and the sent condition and relations of organic and inorganic matter. The moment that we pass beyond this limit, that moment we launch without compass into a vast and boundless ocean of conjecture, guided only and warned by the appearance of innumerable wrecks, the results of similar attempts, which serve to point out the danger, but hardly teach us how to avoid it.
In the actual condition of the earth's surface we find abundant proof of change of almost every kind. Nothing is permanent, nothing continues in a condition absolutely the same for more than the shortest possible time there is movement, disturbance, modification going on, above the surface, on the surface, and beneath the surface-everything is in motion, not a particle of matter in the whole universe stands still, and everything is manifestly tending to a somewhat different state, though there appears every probability that the new state will be strictly analogous to the old one.
In the case of inorganic nature, this perpetual turmoil is now universally recognised. Not only does the earth move as a mass, but every particle of matter seems to be constantly changing its position in relation to the adjacent particles. The air is constantly receiving, conveying, and distributing particles of earth and water. The water is in constant movement from the action of the winds and tides, from the influx of rivers, and from unequal evaporation from its surface. But the surface itself is yet more decidedly exposed to change; for not only is part carried from one place and deposited in another by every dash of the never-tiring wave, and every