appearance in the form of motion, it reappears in the form of heat. This heat seeks an equilibrium by transferring itself to the colder air, in which motion reappears in the heated ascending column. But this motion, in turn, disappears when the heated column, by transference of its heat, has ceased to be warmer than the contiguous air. All force is seeking some affinity with which it may be at rest, or it is striving to effect a motion which will bring its activities to rest. In obedience to the force of gravity, rain falls from the clouds, gathers itself into little rills, which, uniting their forces, join arms with the brooklet, and thence glide in company with the rivulet to the outlet of the valley, and wend their way to the sea. In the deep bed of the ocean the waters rest. The demand of gravity is satisfied. The friction of ascending vapors upon the atmosphere disturbs the equilibrium of the electricities; they flash in anger from cloud to cloud, and between the clouds and the earth, ever striving to restore the equilibrium. When that is effected, all the phenomena resulting from electrical action cease, and would forever cease were not a fresh disturbance introduced. If the electricities are again disturbed, it is because some other force is seeking its equilibrium. This other force is out of equilibrium because some third force has created disturbance in the search for its own equilibrium, and thus link hangs upon link in this chain of causation. We know not how far back the remotest disturbing force may lie, but of this we may be certain; there is somewhere, or will be somewhere in the future, a last disturbing force. Behind this, all is rest. When this has attained its equilibrium, all the phenomena. resulting from the struggle of the forces will cease. This is a mere abstract statement of the case. It possesses a higher significance than we may suspect. The ar gument concerns the stability of the very earth on which

we tread. Every one has heard of the chimera of “perpetual motion." Not every one, however, has considered that the impossibility of perpetual motion results from the impossibility of transforming forces in a perpetual circle. Force shuns perpetual motion. It tolerates no such monotony. It is seeking rest. In larger or smaller quantities it steals away from you, and lies down to a quiet slumber, while your machine is deserted and motionless as a corpse. Heat filters in every direction through the atmosphere; motion steals through the bearings of your wheels, and, under the guise of frictional heat, it sneaks away from your

control.

All motion is mechanical. There is no motion in the heavens above, or upon the earth beneath, which is not ef fected by the self-same forces as we incorporate in a steamengine, or vainly strive to chain to the drudgery of perpetual motion. Every movement which we witness upon the earth-whether of winds, or clouds, or waters, or quaking mountains, is but the motion of some part of a machine. The earth is a piece of mechanism. The varied motions which we witness upon its surface arise from the perpetual transformations of force. The solar system is a piece of mechanism. All its visible motions have been demonstrated to arise from the action of the same force as that which drives a water-wheel or a hydraulic ram.

The question then arises whether the motions of a great machine are more likely to be perpetuated than those of a small one. A vast and complicated machine can be nothing more than a concatenation of small ones.

The very

Ter

statement of the case suggests a negative response. restrial forces, like those which impel the locomotive, are wearing themselves out. All their activities are destined to be invaded by the sluggishness of age-by the torpor of death. The cosmical machine, like a clock, is running

down, and, like a clock, will eventually demand the interposition of an Intelligent Will to re-establish its motion. The denial of this proposition drives us to one of the following alternatives: first, that there exists in Nature an endless series of causation-the remotest assignable cause still hanging upon another cause not higher than a material force-a conclusion entirely at variance with our intuitive cognition of primary causation; or, secondly, that one or more of the series of causes can act in different modes, so that what had just been done is presently undone, or done differently, and thus new conditions created for the renewed activity of other forces. But the supposition of a change in the mode of action of any force or cause contradicts a fundamental axiom of philosophy. We have no authority for such an assumption, and are not at liberty to resort to it.

It can not be denied that these are conclusions which are repugnant to the popular apprehension of Nature's operations. The thought of a "machine," moreover, suggests self-action, and seems at first to exclude that intelligent special agency in Nature which we call Providence. The solar system is, nevertheless, a combination of matter and force whose movements can be calculated with the same precision as those of a steam printing-press. If it be neces sary to protect our notion of a Providence, let us suppose that those mighty forces which handle planets as if they were engaged in a "game of ball" are not energies inherent in matter, but the immediate efforts of a divine will. It may be so. There is no logic which can overthrow the assumption. But in either case, these energies are put forth according to intelligible and unvarying methods; and all that science asserts is, that if the methods remain the same—that is, if the laws of Nature continue unchangedthe course of cosmical activities will complete its round.

All the material forces, therefore, of the universe, both mechanical and physiological, with their actions and reactions, their equilibria and perturbations, are tending gradually toward a general and permanent rest. The threads of their mutual connection may be closely interwoven, but somewhere there is a beginning and an end. Within the grand cycle of their active lifetime apparent circles may be described, but, like the eddies of a river stream, they are lost in the general current, or, like the gyrations of a disk descending through the sea, they are only apparent, and wend their way toward ultimate rest. The same exact conditions are never reproduced. [See Appendix, Note IX.]

CHAPTER XXXVI.

WILL THE MOUNTAINS BE LEVELED?

LET us now direct our attention to a more specific ex

amination of the circumstances under which the visible activities of our terrestrial abode are carried on. The fact which first and most strongly arrests our attention is the presence of universal and perpetual change. This fact alone demonstrates that the existing terrestrial order had a beginning. Work is in progress before our eyes; we may easily determine what has been accomplished and what remains to be accomplished. Had these changes been in progress from all eternity, every thing which existing forces are capable of effecting would have been consummated an eternity since, and physical stagnation would now be reigning. It is equally plain that the work which remains to be accomplished is a finite work, and is destined to be accomplished in finite duration.

What is the work with which terrestrial forces are occupied? What are the labors of oceans, and winds, and rains, and frost, and mountain torrents, and swollen streams, and pent-up fires? We witness here a grand antagonism of Nature's energies. While on one hand Nature has exerted herself to rear the continents, on the other hand a different set of forces has been equally assiduous in beating them down. There was a time when the igneous forces possessed the advantage, and island, and continent, and Alp rose triumphant over the sea. That was the age when the igneous forces were in their youth. Then all their elastic energies were commissioned to rear a dwell