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last century. When well-directed observation shall have been brought to bear upon this all-pervading power, as upon the former, it is scarcely possible to indulge too sanguine hopes of the practical advantages which may flow from such extended knowledge. The forces of nature, indeed, are the powerful, but submissive, servants of man; and through their agency he has been endowed with a subordinate power of creation; but their respective actions have been limited by laws which cannot be transgressed; and in a knowledge of these limits consists the secret of their application.
§ 3. There are two great mistakes which are commonly committed by those who enter upon a systematic course of physical inquiry; and not only by those who are commencing, but by those who undertake to direct, such studies: the first is, the neglecting to form a proper connection with previously acquired knowledge, the undervaluing the results of their ordinary experience as parts of the system,-as the first rounds of that intellectual ladder by which they aspire to scale the loftier heights of philosophy; and the second is, the substitution of names for things, the vague acquirement of certain terms, certain forms of expression, instead of a real understanding of objects and principles to which they have been applied :"terms of ignorance, and of superficial contemplation,” as Lord Bacon calls them.
The process may be repulsive to the too common self-sufficiency of imperfect knowledge, but when invited to reflect and reason upon the simple observations of childhood (simple indeed, but not more easy than those which he will be called upon progressively to make), the student ought to feel no more offence than when in the outset of his geometrical studies he is referred to the axioms, or self-evident truths, that "things equal to the same are equal to one another," and "the whole is greater than its parts." It is from the known that he must ascend to the unknown, and it is all-important that he make his footing sure, and miss no step by the way.
§ 4. Something more, indeed, is necessary than the mere observation of phenomena; there must be a process of reflection upon the evidence of our senses: the foundation must be crowned with a superstructure of thought and reason.
Professor Whewell, in his recent History of the Inductive
Sciences, has accurately remarked*, that "two things are requisite to the formation of science;-facts and ideas; observation of things without, and an inward effort of thought; or, in other words, sense and reason. Neither of these elements, by itself, can constitute substantial general knowledge." It is owing to a defect in this mental process that different arts have often attained to a considerable degree of perfection long before they could be said to form parts of a general structure of science. The chemical arts of glass-making, metallurgy, dyeing, and many others, were known to the ancient Egyptians, who, probably, were utterly ignorant of the principles of chemical philosophy.
The aim of the student then must be not only to obtain distinct facts, but clear ideas of the connection of those facts. Now it is by processes of thought, and operations of mind, which are quite familiar, that the observations of experience and experiment are connected into the order and structure of science; for the principles of natural philosophy are but the principles of common sense.
In the ordinary occurrences of life we are struck with some appearances, some phenomena we may call them,-which are out of the ordinary course of our experience: the mind immediately suggests the familiar inquiry, "What can these be?" We form a conjecture, and we try whether the supposition will include all the circumstances of the case; we reject it, and we guess again; and we proceed in this tentative method till our reason is satisfied that we have taken a right view of the subject. The formal course of philosophy differs not from this.
Amongst a variety of facts, or phenomena, collected together as having some general resemblance or connection with each other, some governing principle is sought, which may apply successfully to the explanation of all their varieties ;-suppositions, guesses, or hypotheses, are first attempted; some with greater, some with less extent, but all, perhaps, without success; each after each failing in the solution, for want of generality and comprehensiveness; till at length, after infinite labour on the part of the inquirer, the LAW is evolved; or a governing principle which combines all together in one comprehensive view, or theory. When by this simple, but laborious process of induction, the mind has once been led up to such laws of nature, they are found to be distinguished by their exceeding simplicity * WHEWELL'S History of the Inductive Sciences, vol. i. p. 6.
both of form and essence. When theories, however, are firmly established and recognised as indisputably true, so as to require no conscious act of thought in their application, they become facts, and as such may enter into the foundation of more comprehensive theories.
The full force and range of the application of the laws of nature are, however, only manifested when, subsequently to their discovery by this inductive process, they are employed in the converse process of deduction, to resolve the various cases which were originally proposed to be determined, and are found to include under their government not only these, but a host of others, which were not contemplated in the first investigation. It is then that the most ignorant and simple-minded are capable of understanding what is thus rendered most self-evident; and the multitude of such governing principles, so established and registered in her archives, constitutes the great advantage of modern science.
§ 5. In framing the hypotheses, or suppositions which commonly precede the discovery of the real laws and true theory of phenomena, there is one useful guide which is so often referred to as to render it expedient to explain its nature and appellation, and that is analogy, or similitude. Design soon becomes apparent in the order of creation; and this design, as far as our limited faculties can trace it, is uniform; and in the system of the universe, every part is doubtless proportioned to the whole. No intelligence but that of OMNISCIENCE can comprehend the plan the theory of the universe: but, from the plan of such small portions as have been mastered, we are often enabled, successfully, to anticipate the order of other portions, and thus to obtain a guide to experiment, to which the ultimate appeal must always be made. Analogy, therefore, may serve to suggest and limit hypotheses; and of such conditional speculations we have the highest authority for saying, that "a facility in framing them, if attended with an equal facility in laying them aside when they have served their turn, is one of the most valuable qualities a philosopher can possess*." But, after all, the mind must not be allowed to rest upon any hypothesis as disclosing the real cause of the phenomena which it explains; for this would prevent any effort to search for any other, and perhaps the true cause. The history of science
* HERSCHEL's Discourse.
abounds with Warnings of this error. In fact, it must be remembered that it is not the province of science to study causes of phenomena or the mode of their production; the legitimate use of hypothesis is to furnish a bond or cement which may unite a number of insulated facts, which, thus united, are often capable of indicating new phenomena.
§ 6. Now, to apply these few plain principles to our present purpose:-With regard to precision of terms, the mere enunciation of the object of the following pages will afford us an opportunity of exemplifying and enforcing our meaning; it is an inquiry into THE FORCES OR POWERS OF MAtter. Let us endeavour to ascertain and define the meaning of the expressions MATTER and FORCE: the words are of common occurrence; but have we that distinct notion of them, those clear ideas concerning their import, which it behoves us to have, in the strict and accurate investigation upon which we are about to enter?
§ 7. Our first knowledge of matter is derived from our touch: a consciousness of resistance in surrounding objects to this sense with which our bodies have been endowed, impresses us with a conviction of their substance,―of their extension,of their impenetrability,—of their power, that is, to exclude every thing of the same kind from being in the same place. This tactile property is possessed by different parts of the skin, in very different degrees; and some parts of the body, from their peculiar organization, are capable of much more delicate impressions from objects with which they may be placed in contact than others. With regard to extension, for instance, it appears from the experiments of Weber, that the tips of the fingers, or the tongue, are capable of appreciating the distance between the points of a pair of compasses which are only one line apart; while the arm or the thigh would confound the two impressions together, even at the distance of thirty lines. Those whose touch has been educated by practice can rule, by their feeling, fine linear divisions which are totally inappreciable to the most experienced eye.
Some philosophers have maintained that the sense of touch alone is not sufficient to convey the conception of form or extension; but that to this is superadded a sixth sense, which they have termed the muscular sense: that is, the conscious exertion by which we move our limbs. Thus we ascertain the
form and position of bodies, by perceiving the course which the fingers take in order to follow the surface of the body, or to pass from one point to another. The muscles of the body, no doubt are, in this respect, auxiliary to our senses, but that can scarcely be deemed a new sense, which is incapable of performing its functions alone.
Different degrees of resistance may even inform us of the different states in which matter exists: a touch will satisfy us that the parts of some bodies are immovable amongst each other; that the particles of others are movable with little resistance; while the passing breeze of air will convince us that matter exists in a form which yields to the lightest breath. A little reflection upon our sensations may thus establish a difference between solid, liquid, and aëriform matter. Experience, again, and the oft-repeated experiments, it may be said, of infancy, teach us to combine observations of touch with those of sight and hearing; and thus we learn to substitute the indications of one sense for those of another, and to judge of distant forms of matter.
If we be curious to know what matter is, we plunge at once into that deep which surrounds us on every side, and which never yet was fathomed by human intellect.
With regard to its ultimate constitution, we cannot hope to attain to a clearer conception than that which presented itself to the comprehensive, but humble, mind of Newton; and that transcendent philosopher has thus embodied the result of his patient investigations:
"It seems probable to me that GOD, in the beginning, formed MATTER in solid, massy, hard, impenetrable, moveable particles, of such sizes and figures, and with such other properties, and in such proportion to space, as most conduced to the end for which He formed them; and that those primitive particles, being solids, are incomparably harder than any porous bodies compounded of them; even so very hard as never to wear or break in pieces; no ordinary power being able to divide what GOD himself made one in the first creation."
But this hypothesis, however convenient and consonant with our prejudices, is not absolutely necessary to the explanation of natural phenomena; for it may be conceived, according to the theory of Boscovich, that matter consists not of solid particles, but of mere mathematical centres of forces attractive and repulsive, whose relations to space were ordained, and whose actions