« ForrigeFortsett »
succession upwards, they are still distinguishable by their organic products and as we approach the most recent beds, there are fewer remains of extinct quadrupeds, and more numerous specimens of such as now inhabit the earth. We find, in the different strata, the bones of the mammoth, the megatherium, the elephant, the tapir, the rhinoceros, the hippopotamus, the stag, the ox, the horse, and with them the skeletons of their natural enemies of the feline tribe, and the bear and the hyæna, the bones of some of which prove them to have been of greater strength and size than those now alive.*
Over the earth's surface, there are evidences that deluges have swept with inconceivable power, brushing off the superficial strata, rolling immense rocks, and depositing the debris, so as to fill chasms, form new accumulations, and with successive elevations and subsidences, to change the whole character of the earth's surface. It was then that the globe assumed its present confines of land and sea, and that the valleys and the courses of rivers were determined. Out of these convulsions and revolutions has come that condition of the world which we now enjoy; and, as I shall have occasion to repeat, no previous state of the earth would have been suitable to our constitution.†
My admiration of the labours of our geologists partakes of a feeling of gratitude. But yet there is something in the subject which leads the devoted student to be over ambitious, and to frame theories almost too comprehensive. It is not enough to say that, after all, the changes on the earth's surface are not greater, in comparison with the size of the earth, than the cracks in the varnish are to the globe that stands on the table. It has been
*See Sir C. Lyell's works, for his Classification of the Tertiary Formations.
When doctrines or principles are laid down dogmatically, there is an end of reasoning; "they are as fetters on the feet, and like manacles on the right hand." In this way, the most famous schools have sunk; for if it become a crime to doubt or investigate, the mind decays. When God informed us of our duties to Himself and to each other, the exercise of our affections was enjoined and left free. To have taught mankind the nature of physical things,
would have made it the duty of the pious to seek no further knowledge, and researches into them would have implied presumption. But by the constitution of the mind, we learn that had we been left in a state of passive obedience, without object or impulse, the loss of the affections as well as of reason would have followed; our sense of goodness and benevolence would have become obtuse, and the charities of life and the love and duty we owe to God must have decayed in us.
Why, then, do geologists quote Scripture, and form their opinions
part of our object to show that the features of our earth, and the phenomena around us, are suited and intended to excite the faculties and imagination. Accordingly, when the geologist, extending his survey from the mountains, over extensive plains, and into ravines and valleys, persuades himself that he can explain when and how they have been formed, he is tempted to indulge in an enthusiasm which can only be permitted to the poet.
Wonderful improvements have, indeed, been made in this science by our countrymen who have associated themselves for that purpose. Buckland, Conybeare, and Mantell, are especially distinguished for the discovery of those large Saurian reptiles; whilst other geologists have exerted their genius and industry with equal effect in different departments. But it is in contemplating the labours of Cuvier, that we have the earliest and best proofs of the importance of comparative anatomy, in giving extraordinary interest to geology. In him was combined an attention to minute objects, with a power of generalising, highly characteristic of genius. Years had been passed in accumulating fossil specimens from the tertiary beds round Paris; and out of these heaps of animal remains, which lay confused as if the fragments of bone had been washed to his feet by a torrent, he was enabled, by following the principle which the early part of this chapter has shown to prevail-the co-relation of the parts of the skeleton-to put together the separate members, to build up the bodies of extinct animals anew, and to present them to us with a precision which we could only have expected from the dissection of the recent animals.
of the structure of the earth on the Mosaic account of the Creation? It does not require deep theological knowledge to comprehend what was intended by that sublime announcement. It was addressed to a people ever prone to fall into the idolatries of surrounding nations. In teaching the Creation of the world, it affirmed the existence of One God pre-existing and eternal. It denied the existence of gods and demons sprung from the earth: it denied that the Deluge was one of a necessary succession of events: or that the earth was subject to be successively de
stroyed or restored: or that those who flourished to the advantage of mankind in one period, should be restored to a similar existence in another. It taught the just relations of the heavenly bodies to the earth, and that they were not the abodes of deified mortals-for these were opinions maintained by the surrounding nations. Surely, then, men are inconsistent, when they expect to find in the Scriptures, which teach the unalterable religious and moral duties, the principles of an uncertain science.
The phenomena visible in the heavens, on the earth, and within it, are of a nature, taken by themselves, to overwhelm the inquirer's mind. To learn his own value, man must consider himself, his physical endowments and capacities, and compare them with the elements around. Without a true conception of his position and relations, the whole range of natural science is barren of consolation; the periods of the revolution are too vast, the objects too distant, to seem to have as their prospective design the condition of the human race.
"God made the country;" and it is perhaps in surveying plains, and meads, and mountains, remote from man, that the mind is most elevated to pure and high contemplations. But cities, temples, and the memorials of past ages, bridges, aqueducts, statues, pictures, and all the elegancies and comforts of the town, are equally the work of God, through the propensities of His creatures, and, we must presume, for the fulfilment of His design. The condition of the earth has by successive revolutions been made to conform to these works of man, and afford the means for them. The metallic veins of the primitive rocks have been exposed; the carboniferous strata, the lime and freestone, have been disjointed and elevated; the riches of the interior of the earth as well as of its prolific surface, the circulation of water and the formation of springs-all give proof that it was designed that the earth should be subdued to man's that he should not live a selfish, solitary, nomad life, but in society, where his higher faculties should be called into activity and his social virtues exercised.
OF THE MUSCLES OF THE ARM AND HAND-THEIR VITAL - THEIR MECHANICAL ADAPTATION TO THE
MOTIONS OF THE HAND AND FINGERS - FORM OF THE
THE Muscle of the body is that fleshy part with which every one is familiar. It consists of fibres which lie parallel to each other. This fibrous structure has a living endowment, a power of contraction and relaxation, termed irritability. A single muscle is formed of some millions of these fibres combined together, having the same point of attachment or origin, and concentrating in a rope or tendon, which is fixed to a moveable part, called its insertion. Upwards of fifty muscles of the arm and hand may be demonstrated, which must all consent to the simplest action. Yet that gives but an imperfect view of the extent of the relation of parts necessary to every act of volition. We are the most sensible of this combination in the muscles when inflammation has seized any great joint of the body; for then, even in bed, every motion of an extremity gives pain, owing to a corresponding simultaneous movement in the trunk. When we stand, we cannot ise or extend the arm without a new poising of the body, through the action of a hundred muscles.
ON THE ACTION OF THE MUSCLES OF THE ARM.
We shall consider this subject under two heads; first, we shall give examples of the living property of muscles; then, of the mechanical contrivances, in their form and application.
First, In all that regards the living endowment of the muscles, we see the most bountiful supply of power commensurate to the object, but never anything in the least degree superabundant. If the limb is to be moved by bringing a muscle or a set of muscles into action, the power is not bestowed in that excess which would enable them to overcome their opponents; but the property of action is for the time withdrawn from the
opponents; they become relaxed, and the muscles, which are in a state of contraction, perform their office with comparative ease. A stationary condition of the limb results from a balanced but regulated action of all the muscles; which condition may be called their tone. If, in an experiment, a weight be attached to the tendon of an extensor muscle, it will draw out that muscle to a certain degree, until its tone or permanent state resists the weight: but if the flexor muscle be now excited, this being the natural antagonist of the extensor, the weight will fall, by the relaxation of the extensor. So that the motion of a limb implies a change in both classes of muscles, the one set contracting, the other relaxing; and the will influences both classes. Were it not so regulated, instead of the natural, easy, and elegant motions of the frame, the attempt at action would exhibit the body convulsed, or, as the physicians term it, in clonic spasms. The similitude of the two sawyers, adopted by Paley, gives but an imperfect idea of the adjustment of the two classes of muscles. When two men are sawing a log of wood, they pull alternately; when the one is pulling, the other resigns all exertion. But this is not the condition of the muscles—the relaxing muscle does not give up all effort, so as to be like a loose rope, but it is controlled in its yielding, with as fine a sense of adjustment as is the action of the contracting muscle. Nothing appears more simple than raising the arm, or pointing with the finger; yet in that single motion, not only are innumerable muscles put into activity, and as many thrown out of action, but both the relaxing and the contracting muscles are controlled or adjusted with the utmost precision, though in opposite states, and under one act of volition.
By such considerations, we are prepared to admire the faculty which shall combine a hundred muscles so as to produce a change of posture or action of the body. We now perceive that the power taken from one class of muscles, may be considered as bestowed on the other; so that the property of life, which we call the irritability, or action of a muscle, is upon the whole less exhausted than would be the case on any other supposition.
As to the second head;-Our demonstration is of an easier kind. We have said that nature bestows abundantly, but not superfluously; a truth evinced in the arrangement of the muscles. In all the muscles of the limbs, the fibres run in an oblique