perversion of expression. Secondly, All the qualities of matter have a direct reference to space or extension, and are conceived in some measure as attributes or qualities of the space within which they exist. When we say that a particular body is solid, we mean merely that a certain portion of space is impenetrable; when we say that it is colored, we mean that the same portion of space appears of one hue, and so of the other qualities; bat sensation or thought is never conceived to occupy space, or to characterise it; nor can these faculties be at all conceived as definite portions of space, endued with perceptible properties. In the third place, all the primary qualities of matter are inseparable from it, and enter necessarily into its conception and definition. All matter must necessarily be conceived so extended, solid, and figured. It is obvious, however, that thought or sensation is not an inseparable attribute of matter, as by far the greater part of matter is entirely destitute of it; and it is found in connexion with those parts which we term organized, only while they are in a certain state, which we call alive. If it be said, however, that thought may resemble those accidental qualities of matter, such as heat or color, which are not inseparable or permanent; then we reply that none of these things can properly be termed matter, more than thought or sensation; they are themselves substances, or matter possessed of inseparable and peculiar qualities, as well as those which address themselves to the other senses. Light is a material substance, from which the quality of color is inseparable; and heat is a material substance, which has universally the quality of exciting the sensation of warmth. If thought be allowed to be a substance, in this sense, it will remain to show that it is material, by being referrible to space, and liable to attraction, repulsion, condensation or reflection, like heat or light.

The notions of the ancients were various with regard to the seat of the soul, and the mode of its action on the body. Some have maintained that it is equally diffused through every part of it; and others say that, whilst it influences and acts upon every part of the body, it has its principal residence in some particular part. Since it has been discovered, by the improvements in anatomy, that the nerves are the instruments of perception, and of the sensations accompanying it, and that the nerves ultimately terminate in the brain, it has been the general opinion of philosophers that the brain is the seat of the soul; and that it perceives the images that are brought there, and external things, only by means of them. Des Cartes, observing that the pineal gland (see ANATOMY) is the only part of the brain that is single, all the other parts being double, and thinking that the soul must have one seat, was thus determined to make that gland the soul's habitation; to which, by means of the animal spirits, intelligence is brought of all objects that affect the senses. Others have not thought proper to confine the habitation of the soul to the pineal gland, but to the brain in general or to some part of it, which they call the sensorium. Even the great Newton favored this opinion, though he proposes it only as a query, with that

modesty which distinguished him no less than his great genius. Is not,' he says, 'the sensorium of animals the place where the sentient substance is present, and to which the sensible species of things are brought through the nerves and brain, that there they may be perceived by the mind present in that place? And is there not an incorporeal, living, intelligent, and omnipresent Being, who, in infinite space, as if it were in his sensorium, intimately perceives things themselves and comprehends them perfectly, as being present to them; of which things, that principle in us which perceives and thinks, discerns only in its little sensorium, the images brought to it through the organs of the senses?' His great friend Dr. Clarke adopted the same sentiments with more confidence. In his papers to Leibnitz, we find the following passages. 'Without being present to the images of the things perceived, the soul could not possibly perceive them. A living substance can only there perceive when it is present, either to the things themselves (as the omnipresent God is to the whole universe), or to the images of things (as the soul of man is in its proper sensory). Nothing can any more act, or be acted upon, where it is not present, than it can be where it is not. We are sure the soul cannot perceive what it is not present to, because nothing can act, o be acted upon, where it is not.'

Locke expresses himself in such a manner, that, for the most part, one would imagine that he thought the ideas, or images, of things, which he believed to be the immediate objects of perception, are impressions upon the mind itself; yet in some passages he rather places them in the brain, and makes them to be perceived by the mind there present. From such passages, cited by Dr. Reid (ubi infra), it may be inferred that he thought there are images of external objects conveyed to the brain. But whether he thought, with Des Cartes and Newton, that the images in the brain are perceived by the mind there present, or that they are imprinted on the mind itself, is not obvious. This hypothesis is founded on three assumptions; and, if any one of them fail, it must fall to the ground. 1. That the soul has its seat, or, as Mr. Locke calls it, its presence-room, in the brain: 2. That images are formed in the brain of all the objects of sense: 3. That the mind or soul perceives those images in the brain; and that it perceives not external objects immediately, but only perceives them by means of those images. The first assumption is not sufficiently established to warrant our founding other principles upon it. Of the second there is no proof or probability, with regard to any of the objects of sense. The brain has been dissected times innumerable, by the nicest anatomists; every part of it has been examined by the naked eye, and with the help of microscopes; but no vestige of any external object was ever found. The brain seems to be the most improper substance that can be ima gined for receiving or retaining images, being a soft, moist, medullary substance. The third assumption is as improbable, as that there are images of external objects in the brain to be per ceived. If our powers of perception, says Dr.

The messenger approaching to him spake, But his waste words returned to him in vain ; So sound he slept that nought might him awake. Faerie Queene. Now when that idle dream was to him brought, Unto that elfen knight he bad him fly, Where he slept soundly, void of evil thought.

Id.

Whom although to know be life, and joy to make mention of his name; yet our soundest knowledge is to know that we know him not as indeed he is, neiher can know him; and our safest eloquence concerning him is silence. Hooker.

The wisest are always the readiest to acknowledge, that soundly to judge of law is the weightiest thing which any man can take upon him. Id.

This presupposed, it may stand then very well with strength and soundness of reason, even thus to

answer.

Id.

I am fallen out with my more headier will, To take the indisposed and sickly fit For the sound man. Shakspeare. King Lear. He hath a heart as sound as a bell, and his tongue is the clapper; for what his heart thinks his tongue speaks. Shakspeare.

When Duncan is asleep, Whereto the rather shall this hard day's journey Soundly invite him. Id. Macbeth. The doctrine of the church of England, expressed in the thirty-nine articles, is so soundly and orthodoxly settled, as cannot be questioned without extreme danger to our religion.

Bacon.

They did ply
My feet and hands with cords, and to the mast
With other halsers made me soundly fast.

Chapman's Odyssey. The men are very strong and able of body; and therefore either give sound strokes with their clubs wherewith they fight, or else shoot strong shots with their bows.

We can preserve
Unhurt our minds, and understanding sound.

New waked from soundest sleep,

Soft on the flowery herb I found me laid

In balmy sweat.

Who had so often in your aid So many ways been soundly paid.

Abbot.

Milton.

Id. Paradise Lost.

The king visits all around,

Hudibras.

Comforts the sick, congratulates the sound;

Honours the princely chiefs.

Dryden.

But Capys, and the rest of sounder mind,

The fatal present to the flames designed,

Or to the deep.

Id.

When the succession of ideas ceases, our percep

When a word, which originally signifies any particular object, is attributed to several other objects, on account of some evident reference or relation to the original idea, this is peculiarly called an analogical word; so a sound or healthy pulse, a sound digestion, sound sleep, are all so called, with reference to a sound and healthy constitution; but if you speak of sound doctrine, or sound speech, this is by way of resemblance to health, and the words are metaphorical. Watts's Logick.

As the health and strength, or weakness of our bodies, is very much owing to their methods of treating us when we were young; so the soundness or folly of our minds are not less owing to those first tempers and ways of thinking, which, we eagerly received from the love, tenderness, authority, and constant conversation of our mothers. Law.

SOUND, v. a., v. N., of Lat. sub unda (thus the Spanish have sondear). To search with a plummet; try depth, as of a wound; try or examine generally as a verb neuter, to try with a sounding-line: a sound is a shallow sea, such as may be sounded.

& n. s. Fr. sonder, sonde,

In this secret there is a gulf, which while we live

Behold I come, sent from the Stygian sound,
As a dire vapour that had cleft the ground,
T'ingender with the night, and blast the day.

Ben Jonson. Invites these lords, and those he meant to sound. Daniel.

Beyond this we have no more a positive distinct notion of infinite space than a mariner has of the depth of the sea, where having let down a large portion of his sounding line, he reaches no bottom. Locke.

I've sounded niy Numidians, man by man, And find 'em ripe for a revolt. Addison's Cato. The patient being laid on a table, pass the sound Till it meet with some resistance. Sharp's Surgery. Him young Thoosa bore, the bright increase Of Phorcys, dreaded in the sounds and seas. Pope. SOUND, n. s., v. n., & v. a.` Fr. son; Span. SOUND BOARD, n. s. SOUNDING, adj.

Locke.

this procedure have been no less fatal to the progress of true knowledge in modern times than in the schools of ancient Greece; and the ethereal philosophers of modern times, like the followers of Aristotle, have filled ponderous volumes with nonsense and error. It is strange, however, that this should be the effect of a great and a successful step in philosophy: but the fault is in the philosophers, not in the science. Nothing can be more certain than the account which Newton has given of the propagation of a certain class of undulations in an elastic fluid. But this procedure of nature cannot be seen with distinctness and precision by any but well-informed mathematicians. They alone can rest with unshaken confidence on the conclusions legitimately deduced from the Newtonian theorems; and even they can insure success only by treading with the most scrupulous caution the steps of this patient philosopher. But few have done this; and we may venture to say that not one in ten of those who employ the Newtonian doctrines of elastic undulations for the explanation of other phenomena have taken the trouble, or indeed were able, to go through the steps of the fundamental proposition. But the general results are so plain, and admit of such impressive illustration, that they draw the assent of the most careless reader; and all imagine that they understand the explanation, and perceive the whole procedure of nature. Emboldened therefore by this successful step in philosophy, they, without hesitation, fancy similar intermediums in other cases; and, as air has been found to be a vehicle for sound, they have supposed that something which they call ether, somehow resembling air, is the vehicle of vision. Others have proceeded farther, and have held that ether, or another something like air, is the vehicle of sensation in general, from the organ to the brain.

It is of considerable importance to understand thoroughly this doctrine of sound, that we may see clearly and precisely in what it consists, and what is the precise mechanical fact in which it terminates. For this, or a fact perfectly similar, must terminate every explanation which we derive from this by analogy, however perfect the analogy may be. This previous knowledge must be completely possessed by every person who pretends to explain other phenomena in a similar manner. Then, and not till then, he is able to say what classes of phenomena will admit of the explanation: and, when all this is done, his explanation is still an hypothesis, till he is able to prove, from other indisputable sources, the existence and agency of the same thing analogous to the elastic fluid, from which all is borrowed. Such considerations would justify us for considering with great attention the nature of sound. But a work like this will not give room for a full discussion; and we must refer our readers to the writers who treat it more at large. Much information may be got from the authors of the two last centuries, such as lord Verulam, Kircher, Mersennus, Cafferius in his great work De Voce et Auditu; Perrault, in his Dissertation du Bruit, Murshenbroeck, in his great System of Natural Philosophy, in 3 vols. 4to., and in his Essays de Physique; and the writings of the physiologists VOL. XX.

of the present age. We also refer to what has been said in the article ACOUSTICS. At present, therefore, we must content ourselves with giving a short history of the speculations of philosophers on this subject, tracing out the steps by which we have arrived at the knowledge which we have of it. We apprehend this to be of great importance, because it shows us what kind of evidence we have for its truth, and the paths which we must shun if we wish to proceed farther: and we trust that the progress which we have made will appear to be so real, and the object to be attained so alluring to a truly philosophical mind, that men of genius will be incited to exert their utmost efforts to pass the present boundaries of our real progress.

In the infancy of philosophy, sound was held to be a separate existence, something which would exist, although no hearing animal existed. This was conceived as wafted through the air to our organ of hearing, which it was supposed to affect in a manner resembling that in which our nostrils are affected when they give us the sensation of smell. It was one of the Platonic species, fitted for exciting the intellectual species, which is the immediate object of the soul's contemplation. Yet, even in those early years of science, there were some, and, in particular, the celebrated founder of the Stoic school, who held that sound, that is, the cause of sound, was only the particular motion of external gross matter, propagated to the ear, and there producing that agitation of the organ by which the soul is immediately affected with the sensation of sound. Zeno, as quoted by Diogenes Laertius (lib. vii. § 158), says, 'Hearing is produced by the air which intervenes between the thing sounding and the ear. The air is agitated in a spherical form, and moves off in waves, and falls on the ear, in the same manner as the water in a cistern undulates in circles when a stone has been thrown into it.' The ancients were not remarkable for precision, either of conception or argument, in their discussions; and they were contented with a general and vague view of things. Some followed the Platonic notions, and many the opinion of Zeno, but without any farther attempts to give a distinct conception of the explanation, or to compare it with experiment. But in later times, during the ardent researches in the seventeenth century into the phenomena of nature, this became an interesting subject of enquiry. The invention of the air-pump gave the first opportunity of deciding by experiment whether the elastic undulations of air were the causes of sound and the trial fully established this point; for a bell rung in vacuo gave no sound, and one rung in condensed air gave a very loud one. It was therefore received as a doctrine in general physics that air was the vehicle of sound. The celebrated Galileo, the parent of mathematical philosophy, discovered the nature of that connexion between the lengths of musical chords and the notes which they produced, which had been observed by Pythagoras, or learned by him in his travels in the east, and which he made the foundation of a refined and beautiful science, the theory of music. Galileo showed that the real connexion subsisted between the tones and the 2 T

vibrations of these cords, and that their different degrees of acuteness corresponded to the different frequency of their vibrations. The very elementary and familiar demonstration which he gave of this connexion did not satisfy the curious mathematicians of that inquisitive age, and the mechanical theory of musical chords was prosecuted to a great degree of refinement. In the course of this investigation, it appeared that the chord vibrated in a manner precisely similar to a pendulum vibrating into a cycloid. It must therefore agitate the air contiguous to it in the same manner; and thus there is a particular kind of agitation which the air can receive and maintain which is very interesting. Sir Isaac Newton took up this question as worthy of his notice; and endeavoured to ascertain with mathematical precision the mechanism of this particular class of undulations, and gave us the fundamental theorems concerning the undulations of elastic fluids, which make the forty-seven, &c., propositions of Book II. of his Principles of Natural Philosophy. They have been (perhaps hastily) considered as giving the fundamental doctrines concerning the propagation of sound. They are therefore given in this work in the article ACOUSTICS; and a variety of facts are related, in the article PNEUMATICS, to show that such undulations actually obtain in the air of our atmosphere, and are accompanied by a set of phenomena of sound, which precisely tally or correspond to all the mechanical circumstances of these undulations. In the mean time, the anatomists and physiologists were busily employed in examining the structure of our organs of hearing. Impressed with the validity of this doctrine of aerial undulations being the causes of sound, their researches were always directed with a view to discover those circumstances in the structure of the ear which rendered it an organ susceptible of agitations from this cause; and they discovered many which appeared as contrivances for making it a drum, on which the aerial undulations from without must make forcible impulses, so as to produce very sonorous undulations in the air contained in it. These therefore they considered as the immediate objects of sensation, or the immediate causes of sound. But some anatomists saw that this would not afford a full account of the matter; for, after a drum is agitated, it has done all that it can do; it has produced a noise. But a farther process goes on in our ear: There is behind the membrane, which is the head of this drum, a curious mechanism, which communicates the agitations of the membrane (the only thing acted on by the undulating air) to another chamber of most singular construction, where the auditory nerve is greatly expanded. They conceive, therefore, that the organ called the drum does not act as a drum, but in some other way. Indeed, it seems bad logic to suppose that it acts as a drum merely by producing a noise. This is in no respect different from the noise produced out of the ear; and, if it is to be heard as a noise, we must have another ear by which it may be heard, and this ear must be another such drum; and this must have another, and so on for ever. is like the inaccurate notion that vision is the

It

contemplation of the picture on the retina. See ANATOMY, Index. These anatomists attended therefore to the structure. Here they observed a prodigious unfolding of the auditory nerve of the ear, which is curiously distributed through every part of this cavity, lining its sides, hung across it like a curtain, and sending off fibres in every direction, so as to leave hardly a point of it unoccupied. They thought the machinery contained in the drum peculiarly fitted for producing undulations of the air contained in this labyrinth, and that by these agitations of the air the contiguous fibres of the auditory nerve are impelled, and thus we get the sensation of sound, The cavity intervening between the external air and this inner chamber appeared to these anatomists to have no other use than to allow a very free motion to the stapes or little piston that is employed to agitate the air in the labyrinth. This piston condenses on a very small surface the impulse which it receives from a much larger surface, strained by the malleus on the entry of the tympanum, on purpose to receive the gentle agitations of the external air in the outer canal. This membraneous surface could not be agitated unless completely detached from every thing around it; therefore all animals which have this mechanism have it in a cavity containing only air. But they held that nature had even taken precaution to prevent this cavity from acting as a drum, by making it of such an irregular rambling form; for it is by no means a cavity of a symmetrical shape, like a vessel, but rather resembles the rambling holes and blebs which are often seen in a piece of bread, scattered through the substance of the cranium, and communicating with each other by small passages. The whole of these cavernulæ are lined with a softish membrane, which still farther unfits this cavity for producing sound. This reasoning is specious, but not very conclusive. We might even assert that this anfractuous form, with narrow passages, is well fitted for producing noise. If we place the ear close to the small hole in the side of a military drum, we shall hear the smallest tap of the drumstick like a violent blow. The lining of the cavernulæ is nervous, and may therefore be strongly affected in the numerous narrow passages between the cells.

While these speculations were going on, with respect to the ear of the breathing animals, observations were occasionally made on other animals, such as reptiles, serpents, and fishes, which give undoubted indications of hearing; and many very similar facts were observed or recollected, where sounds are communicated through or by means of solid bodies, or by water: therefore, without enquiring how or by what kind of mechanism it is brought about, it became a very general belief among physiologists that all fishes, and perhaps all animals hear, and that water in particular is a vehicle of sound. In 1767 or 1768 an ingenious gentleman, at the suggestion of the late professor of astronomy in the univer sity of Glasgow, made an experiment in a lake in that neighbourhood, by striking a large hand bell under water, and heard it very distinctly and strongly when his head was plunged in the water at the distance of more than 1200 feet