The

recognized principle of natural philosophy is extended to the domain of chemistry, and the material particles are supposed to be as utterly inert as the masses built up from them. idea of inherent forces—of attractions and repulsions, of gravity, cohesion, and chemical affinity-is discarded, as wholly incompatible with the nature of matter. The component atoms of a body can no more possess the power of self-motion, than the body itself. Every change—whether from rest to motion or from motion to rest-must be impressed upon them by forces from without. The only power or capability which we can rationally ascribe to the atoms is that of receiving, modifying, and transmitting these forces. The sun is the great primary source of all the physical activities of which our globe is the theatre. Impulses of mechanical force are continually emanating from that mighty orb. Propagated through a universally diffused electric medium, they reach the earth, where, modified by the several elementary and compound substances, they appear under as many different forms as these exhibit powers and properties. Oxygen, hydrogen, carbonic acid, and ammonia are subtile mechanisms, each dependent for its power of changing the direction of the impulses reaching it upon the peculiar grouping of its component atoms. Light, heat, electricity, magnetism, cohesion, and chemical affinity are only different exhibitions of force, whose characters are severally determined by these mechanisms. They are readily convertible into one another, and are all traceable, either directly or indirectly, to the sun.

The existence of a universally diffused electric fluid is inferred from the necessity of some medium for transmitting through space the impulses of gravity, as well as from the positive proofs of the existence of such a fluid around, and within the earth. Although a species of matter, it is supposed to possess perfect mobility, and to be capable of propagating without loss or diminution whatever impulses are communicated to it; and as it fills all space, such impulses when once imparted must continue to course and recourse its soundless depths through all time. They can no more be lost than matter can be lost. They must be as indestructible as

the fluid which they traverse. They can be annihilated only by the fiat of the Almighty.

But bodies moving rapidly through the electric fluid disturb, as experiment shows, its equilibrium, and develop impulses of force. May we not, therefore, suppose the so-called forces of nature to be but diffusions of the strength of that arm which launched the planetary orbs in space, and gave to each its proper motions? May not the tide of life and motion, ever ebbing and flowing within and around us, be only ceaselessly recurring waves of a divine energy poured into our system at the time of its creation?

Such in outline is Mr. Allen's Philosophy of the Mechanics of Nature. Whether true or false, the conception of the material universe presented by it is one of surpassing simplicity and grandeur. Although some may not be disposed to grant the postulate upon which the system is based, and others may call in question the logical processes connecting its several parts, no one can fail to recognize in it proofs of high creative power associated with rare philosophic genius. Considered as a theory for the explanation of phenomena, - the only light in which we suppose its author to regard it, — it is to be judged of solely by its adequacy and its simplicity. All such theories must, from the nature of the case, be incapable of demonstration. They relate to the causes or essences lying back of the phenomena, and consequently wholly hidden from human view. So long as they explain all the known facts in a natural and simple manner, they are to be regarded as sound and legitimate. When from the progress of discovery they have ceased to do this, they must be set aside, and others sought to take their places.

That the physical sciences have outgrown many of the hypotheses still connected with them, that for some time past they have been advancing in spite of these hypotheses, rather than through them,- will, we think, be generally admitted. More especially is this true of the branches relating to what are called the imponderables. The suppositions made for explaining the laws of light, heat, electricity, and magnetism, although originally simple and satisfactory, have taken on so many additions in accommodating themselves to new phases

of these sciences, that they no longer conform to any of the requirements of a good theory. They are inadequate. They are complex. They are contradictory. The rich veins of truth to which they originally pointed have been exhausted, and they now serve only to prolong research in unprofitable directions. Instead of aiding, they hinder discovery by blocking the entrance to the paths that lead to it. Nor do we believe that any great advance will be made in this department of human knowledge until these obstructions shall be removed, - until some Samson arise, who, breaking the cords of theory and shaking himself free from the withes of hypothesis, shall bear away the gates of Gaza, and open new fields for investigation. Whether this has been accomplished in the work before us, must be left for time to determine.

But whatever may be thought of Mr. Allen's Philosophy of the Mechanics of Nature, the generalizations connected with it are exceedingly beautiful, and are, moreover, in strict accordance with facts, so far as made known by science. They will constitute in the estimation of many, we presume, the most valuable portion of his labors. We can only indicate them in the briefest manner.

Two processes, not only entirely dissimilar, but directly opposite in character and tendency, are everywhere in progress, -oxidation and deoxidation. The former occurs in ordinary combustion, in the corrosion of metals, in the wasting of animal tissue, and in the decay of all organic bodies. It is always attended by an exhibition of force varying in character according to circumstances. Steam power is due to the oxidation of the wood or coal placed under the boiler of the engine. Electro-magnetic power is due to the oxidation of the zinc element of the battery. Animal power is due to the oxidation of brain and muscle, and not to the will, which merely determines its manifestation.

Deoxidation is confined to the leaves of plants. In these, under the influence of the sun's rays, carbonic acid, and water, the sulphates and the phosphates undergo resolution. The greater part of the oxygen is thrown off, while the carbon, the hydrogen, the sulphur, and the phosphorus are wrought into the vegetable tissues. These substances all exist naturally in

the state of oxides, and when reclaimed from that state more or less speedily return to it. The leaf of the plant is an apparatus specially devised for the application of sun-power to reclaiming them. All the vegetable products have been thus deoxidized, and may consequently be regarded as representatives of sun-power. Brain and muscle built up from these products also represent sun-power. Charcoal, and metals reduced from the state of ores by it, represent sun-power. The beds of bituminous and anthracite coal found in different parts of the earth—all of vegetable origin-represent sun-power. Steam-power, electro-magnetic power, and animal motivepower, resulting from the return, under different circumstances, of these substances to the state of oxides, are all, therefore, representatives of sun-power; or, adopting the theoretical views of Mr. Allen, they are sun-power modified by the material mechanisms through which it is transmitted.

The power of wind and of running water is also traceable, through a different channel indeed, to the same source. The currents of the atmosphere arise from disturbances of its equilibrium by solar heat. The currents of the ocean have a similar origin. Rivers are waters on their return from regions whither they have been borne through the agency of heat. Wind-power and water-power, therefore, still represent sunpower; or, as Mr. Allen would say, are sun-power modified in its transmission through material mechanisms.

Man cannot originate force. He may discover and lay open the natural sources of motive-power lying around him, but he can create no new sources. Even volition, which metaphysicians have been accustomed to regard as the type of all proper causation, and from which many would derive the only idea of power, merely determines its manifestation. It is the mere touch of the key by the operator of the telegraph. Without a supply of motive-power in the brain, the will could as easily create an arm as move it.

Nature cannot originate force. The different forms of matter, whether ponderable or imponderable, can only receive and propagate it. As well might we suppose the elements selfformed as self-moved; as rationally ascribe to them spontaneity of origin, as spontaneity of motion. The varied impulses

to which they are continually yielding must all come from without. Every form of motive-power, wherever appearing, or however emerging, is but the welling-up of sun-power; and sun-power is but the ceaseless flux and reflux of a force divinely imparted to our system at the time when the morning stars sang together, and all the sons of God shouted for joy.

The work of Dr. Wayland is designed not so much to advance the science of Intellectual Philosophy, as to present its known and admitted truths in a simple and accessible form. Although well adapted to interest the general reader, it is intended more especially for the college student; and it is in the character of a text-book, chiefly, that we should regard it, if we would justly appreciate its merits. In the Preface the author says: "I have not entered upon the discussion of many of the topics which have called into exercise the acumen of the ablest metaphysicians. Intended to serve the purposes of a textbook, it was necessary that the volume should be compressed within a compass adapted to the time usually allotted to the study of this science in the colleges of our country. I have, therefore, attempted to present and illustrate the important truths in intellectual philosophy, rather than the inferences which may be drawn from them, or the doctrines which they may presuppose. These may be pursued to any length, at the option of the teacher." The course adopted in this respect we believe to be a wise one. In addition to the cogent reasons assigned for it, others, of almost equal weight, present themselves. Even if, in the distribution of the brief period allotted to a college course, among the different branches of knowledge claiming attention, a larger portion of time were allowed to the metaphysics, we should doubt the expediency of introducing classes to the higher and more difficult problems of the science. As a general thing, they are not prepared for them. With here and there an individual exception, they have neither the age nor the mental training fitting them for such inquiries. As well might the young geometer be initiated into the mysteries of the calculus, or of the Mécanique Céleste. The power of noting, comparing, and analyzing the mental processes is of comparatively late growth. The mind is at first occupied exclusively with the outward