ance of understanding, to the acknowledgement of God, and of the Father, and of Christ.

Colossians, chap. ii. v. 2. But is it credible, that the very acknowledgment of our unworthiness to obtain, and in that respect, our

professed fearfulness to ask any thing, otherwise than only for his sake to whom God can deny nothing; that this should be termed baseness, abjection of mind, or servility-is it credible? Hooker's Ec. Pol. My people do already know my mind; And will acknowledge you and Jessica, In place of lord Bassanio and myself. Thou sun of this great world both eye and soul, Acknowledge him thy greater; sound his praise In thy eternal course, both when thou climbest And when high noon hast gain'd, and when thou fallest. Milton.

Shaks.

Davies.

None, that acknowledge God or providence, Their soul's eternity did ever doubt. There can be no more forcible motive to patience, than the acknowledgement of the divine hand that strikes us. Hall's Contemplations, As teaching bringeth us to know that God is our supreme good; so prayer testifieth that we acknowledge him our sovereign good. Bishop Taylor's Sermons. ALMANZ. Accept this diamond, till I can present Something more worthy my acknowledgment.

Dryden's Conquest of Granada, part ii. We are the subjects of the Almighty; and whether we acknowledge it or not, we live, and cannot but live under his government. Bishop Porteus.

ACKNOWLEDGMENT MONEY, a sum paid by tenants, in several parts of England, on the death of their landlords, as an acknowledgment of their new lords.

ACKWORTH, a village, near Pontefract in Yorkshire; distinguished by a benevolent institution for the education of the children of Quakers. This school belonged originally to the Foundling Hospital, London; but in the year 1777, being offered for sale, with eighty-five acres of adjoining land, the respectable society of Friends bought the property, and endowed it at an expence of £7000 for the education of their own youth of both sexes. The edifice is spacious, and built entirely of stone; and part of the eastern wing has been converted into a chapel.

ACLIDES, in Roman antiquity, a kind of missile weapon, having a thong fixed to it, by which, after casting it out of the hand, it might be drawn back again. Servius describes the aclides as full of spiculæ.

ACLOWA, in botany, a barbarous name of a species of colutea. It is used by the natives of Guinea to cure the itch: They rub it on the body as we do unguents.

ACMASTICA, in medicine, a continued fever. See SYNOCHUS.

AC'ME, aкμn, Gr. the highest point of any thing; the crisis.

ACMELLA. See ACHAMELLA
ACMONIA. See AGMONIA.

ACNE, in medicine, a name given to a small pimple, or hard tubercle, on the face.

ACNIDA, VIRGINIAN HEMP, in botany, a genus of the dioecia order, belonging to the pentandria class of plants; and, in the natural order, associating with the scabrida.

ACNUA, in Roman antiquity, a measure of and, about equal to the English rood.

ACO, a fish found in the lake Como, Italy. and in the Mediterranean, called also aquo and sarachus.

ACOBAMBA, a settlement of Peru, in the province of Argaraes, forming the capital, but Peruvian settlements. now decayed. Also, the name of two smaller

ACOEMETE, or ACOEMETI, from a privative, and kopaw, to sleep, in church history, certain monks, who flourished in the East, in the fifth century; and who had divine service performed, without interruption, in their churches. The religious of the Holy Sacrament, in the church of Rome still keep up a perpetual adoration: some one or other of them praying before the sacrament, day and night. The ancient acoemetæ are supposed, by Wetstein and others, contains a catalogue of the psalms to be sung to have written the Codex Alexandrinus, as it every hour of the day and night.

ACOLCHICHI, in ornithology, the Mexican name for the oriolus phœnicus of Linnæus. ACOLD', or COLD. See COLD.

And as it shulde so betide,
A poure lazar upon a tide

Came to the gate and axed meate :
But there might he nothing geate,
Thus laie this poure in great distresse,
A colde and hongred at the gate.

Gower, Con. A. book vi. v. 9.
-Prick my hand

And it will bleed; a fever shakes me, And the self-same wind that makes the young lambs shrink,

Makes me acold.

Beaumont and Fletcher's Faithful Shepherdess, act i. sc. 1.

ACOLIN, in zoology, the name of a bird of the partridge kind, common in the Spanish West Indies.

ACOLYTHI, in ecclesiastical history was first applied to young people, who continually attended the bishops, and were generally candidates for the ministry. In the Romish church their functions became different. They were such as had only received the first of the four lesser orders, and whose business was to light the tapers, carry the candlesticks, and the incense-pot, and prepare the wine and water.

ACÒLYTHUS, a title in the Grecian empire, given to the captain or commander of the Varangi, a body of guards appointed for the security of the emperor's palace.

ACOMAC. See ACCOMAC.

ACOMINATUS, (Nicetas,) was secretary to Alexius Comnenus and to Isaacus Angelus successively; he wrote a history from the death of Alexius Comnenus in 1118, where Zonaras ended his, to the year 1203, which has undergone many impressions, and is much applauded by the best critics in history.

ACON, an instrument used in the ancient exercises, like the discus. Also an ancient order of knights, who joined the Hospitallers.

ACONCAGUA, a province of Chili, South America, bounded on the north and west by Quillosa, on the east by the Andes, and south by Santiago. The mountains furnish immense quantities of copper ore; and the neighbourhood

abounds with greens and fruits. There is a royal road through this province, across the Cordilleras to Mendoza and Santiago, by which the mails of Europe are regularly received once a month. The treasures which pass by this road in winter, are frequently interrupted by means of snow falling down from the mountains, and provisions for continual stoppages are a necessary part of the equipage. The territory itself is level, and contains a population of 8000 souls. ACONCAGUA, a trading town of Chili, the ancient capital of a province, now reduced.

ACONCAGUA, a considerable river of Chili, which, rising in the Cordilleras, and passing through Quilot, Cirvon, &c. enters the Pacific at about 33° S. lat.

ACONCROBA, in botany, a plant that grows wild in Guinea, and is much esteemed for its virtue in the small-pox. It is given infused in wine. ACONE, in antiquity, 1. A stone used as a whetstone, and more usually known among the Romans by the name coticula. 2. A mortar for the purpose of levigation.

ACONITA, in chemistry, a vegetable poison recently extracted from the aconitum Napellus, or wolf's-bane, (properly alkaline,) by Mr. Brande. The analysis has not yet been made public.

ACONITI, aкovirog, without dust, in antiquity, an appellation given to some of the Athletæ, but differently interpreted: i. e. 1. Of those who only anointed their bodies with oil, but did not smear themselves over with dust, which was the usual practice. 2. Of those who conquered easily without dust, q. d. akoviri apay, with little trouble.

ACONITON, in medicine, signifies not plastered, and is applied to vessels not lined within. ACONITUM, ACONITE, WOLFSBANE, or MONKSHOOD; a genus of the trigynia order, belonging to the polyandria class of plants. In the natural order, it associates with the multisiliquæ.

ACONQUIJA, a lofty mountain of Tucuman, in the vice-royalty of Buenos Ayres, covered with perpetual snow, and said to be very productive of the precious metals.

ACONTIAS, from Akovriov, Gr. a name with Pliny and others, for a sort of comet, or meteor. Also a serpent of Calabria and Sicily, whose bite is very poisonous. It is an obsolete name of the anguis jaculus, or dart-snake. See AN

GUIS.

ACONTIUM, aкovrtov, in Grecian antiquity, a kind of dart or javelin resembling the Roman pilum.

ACONTIUS, (James,) a philosopher, civilian, and divine, born at Trent: in 1557, he embraced the reformed religion; and coming into England in the reign of queen Elizabeth, was much honoured by her, which he acknowledges in his celebrated Collection of the Stratagems of Satan, dedicated to that queen. He also wrote De Methodo sive recta Investigandarum, 1558, which

is considered his best work and Ars Muniendorum Oppidorum, 1585.

ACOOTAN, one of the Aleutian or Foxislands, containing some very lofty mountains. ACOPA or ACOPICA, in botany, a name given by Dioscorides, and some authors, to the menyanthes trifoliata, or buck-bean.

ACOPA, Gr. from a privative, and Korog, weariness, in medicine, remedies against lassitude or weariness, such as tensions, pains in the bones, &c. Acopis, is a fossile salt, described by Pliny, and used by the ancients, mixed with oil for this purpose.

ACOPON, ACOPUM, or ACOPOS. See ACOPA. ACOR, in medicine, sourness or acrimony, as in the stomach, &c.

ACORDINA, in chemistry, Indian tutty.

ACORI, in natural history, BLUE CORAL. The true aco is very scarce; some, however, is obtained on the coasts of Africa, near the river Camarones. That of the kingdom of Benin is also much esteemed. It is also a name for the greater Galangal root.

The ACORN, in early ages, was a common article of food, and so late as 1709, was extensively used in France during a scarcity. It was divested of its husk and then boiled. In Spain, it is said in former times to have been served at table as a delicacy. It has often been substituted for coffee when roasted.

ACORN, in medicine, the seed of the oak, used as an astringent.

ACORN, in maritime affairs, a little piece of wood, fashioned like a cone, and fixed on the uppermost point of the spindle, above the vane, on the mast head, to keep the vane on.

ACORUS, CALAMUS AROMATICUS, SWEET FLAC, or SWEET RUSH: a genus of the monogynia order, belonging to the hexandria class of plants; and ranking in the second natural order, piperitæ.

ACORUS, in natural history. See ACORI.

ACOSTAN, a mountainous island in the north seas between Asia and America, observed by Captain Cook.

ACOTYLEDENES, of a, priv. and korvλndov, lobeless, in botany, a class of plants without lobes, or seminal leaves. It is the first class in the natural order of Jussieu.

ACOUS, or Accous, a town of France, in the province of Bearn, department of the Lower Pyrenees, and arrondissement of Oleron. Population 1600. It is about nine leagues southwest of Pau.

ACOUSMATICI, from arew, to hear, such of the disciples of Pythagoras, as had not completed their five years' probation. They are sometimes called by Latin writers, acoustici.

ACCOUSTIC DISCIPLES. See ACOUSMATICI ACOUSTIC DUCT, in anatomy, the meatus auditorius, or external passage of the ear. See ANA

TOMY.

ACOUSTIC INSTRUMENT, or auricular tube, See ACOUSTICS.

ACOUSTIC MEDICINES, remedies against imperfections and disorders of the ear.

ACOUSTIC NERVE, the auditory nerve. See ANATOMY.

ACOUSTIC VESSELS, in the ancient theatres, were a kind of vessels, made of brass, shaped in the bell-fashion, which being of all tones within the pitch of the voice or even of instruments, rendered the sounds more audible, so that the actors could be heard through all parts of the theatres, when they were even 400 feet in diameter.

ACOUSTICA, or ACOUSTICs, from akovo, audio; called also, PHONICS, from pwvn, vor, vel sonus, a voice, or sound, is the doctrine or science of sounds. Some authors divide it into two branches, and entitle that which treats of the properties of sounds that come directly to the ear, DIACOUSTICs, and that which illustrates the nature of reflected sounds, CATACOUSTICS; but these distinctions do not appear to be of any real importance. In treating of this subject, we propose to give a concise view,

I. OF THE DIFFERENT THEORIES of SOUND.
II. OF THE DIFFUSION of SOUND.
III. OF ITS VELOCITY, and

IV. OF ITS REVERBERATION : closing our article with a few familiar experiments that will illustrate the laws of this science.

SECT. I. OF THE THEORY of SOUND.Strange it is, that upon a topic which has exercised the powers of a Bacon, a Newton, and a Boyle, and to which some of our most accurate modern experimenters have also directed their attention, so little that is satisfactory in theory can be produced. There is, in fact, hardly any doctrine of acoustics, that can be offered with confidence to the reader. Embracing phænomena, which must have attracted the attention of mankind from the earliest period of history, and which in its connection with music, and every modulation of the human voice, offers much that is in the highest degree essential to the pleasure of social intercourse, a philosophical theory of sound seems as yet to have eluded research. We shall, in this article, therefore only attempt a record of the best opinions upon the subject that have been given by our predecessors: fairly avowing to our readers, that we look to a better digest of past experiments, and many future additional ones, for a more satisfactory theory than any that has yet been offered every one that we have yet seen being in many important pomts, inconsistent with well-recorded facts and observations. And the progress of our work will give us an opportunity (under EAR, ECHO, HARMONY, HEARING, MUSIC, SOUND, &c.) of recording any thing that may, for a short time,

be added to the philosophical materials of the subject.

Sound then has been said to be strictly a sensation or perception of the mind, communicated by the ear; or the effect of some external collision of bodies which has produced a tremulous motion or vibration, communicated to the ear. In popular language, the surrounding air or atmosphere, is generally understood to be the medium of sound, but a slight observation of facts will shew that air is by no means the only conductor of sound; fluids generally, and bodies of all degrees of hardness and of elasticity are also mediums of its diffusion.

Philosophers, in attempting to find the immediate cause of sonorous motion, tell us that all bodies consist of an infinite number of invisible parts or corpuscles perfectly hard and incompressible; that these are surrounded by particles differing according to the different union and figures of their component parts; and that these last being compressed by an external power or impulse, have a constant tendency to restore themselves to their settled and former state. It is this motion of the latter particles which M. Perrault and others consider as the proximate cause of sound. So that if we rightly understand this theory, it is simply the struggle of the elastic portion of bodies which produces the phenomenon in question. But what proof has ever been offered of the existence of these hard and incompressible portions?

Other writers have contended that all bodies are essentially elastic, and are composed of parts connected throughout by a system of mutual attraction and repulsion. When this arrangement is disturbed, a force, of infinite variety in its degrees of power, is exerted to restore the equilibrium, and that hardness and softness, solidity and fluidity, are but relative and comparative, and not absolute qualities of bodies. When, therefore, we strike a substance thus composed, the particles immediately proximating yield to the impression, but press against the next particles in the series, and thus convey a vibratory motion like the oscillations of a spring or pendulum along the whole chain; the rapidity of the transmission depending upon the relative elasticity of the body. In some bodies, in a bell, glasses, &c. when struck, this sympathetic movement of parts is very evident, and the manner in which, with the finger, we can deaden or stop the sound, by assisting to set the particles at rest, seems to confirm this view of the subject.

Professor Leslie has examined with some care, the laws of this interior mechanism of bodies to which he attributes sound. He says, we may determine the celerity of transmission, by the elasticity of the medium compared with its gravity; or by obtaining the height of a column of the same density as the conducting substance, whose weight would measure its elasticity. This he terms the modulus of its elasticity, and observes that it may be demonstrated upon

the

principles of Dynamics, that the rapidity of the transmission of sound through any medium, is equal to what a descending body would acquire in falling through half the height of the modulus of elasticity; and that this celerity for any second of time may be obtained in English feet, by multiplying the square root of half the modulus by eight. One easy method which he suggests for ascertaining the modulus of elasticity in solid rods or planks is, to observe their swag or curvature when laid in an horizontal position on props. He found by experiments of this kind, that the modulus of Memel fir was equal to 671,625 feet; and that its particles would therefore convey a vibratory impulse with a velocity of 4636 feet in a second, nearly four times the rapidity with which sound travels through the

air.

Several foreign philosophers have directed their attention to the velocity with which the tremor of sound passes through various bodies. M. Biot ascertained that sound was conveyed through a train of iron pipes of 2550 feet in length, in 2.79 sec.; through the air, it would have passed the same distance in 2.5 sec. M. Hassenfratz has attempted to make similar calculations, in the subterranean quarries of Paris, upon the transmission of sound through brick and stone; but no precise results have as yet been given to the world.

Professor Chladni has endeavoured to obtain data upon this curious point, from a very different source: viz. the musical note which a bar of a given substance would emit when struck; and he thus contends that sound may be reckoned to pass through glass and iron at the prodigious rate of 17,500 feet, or upwards of three miles in each second.

Through fresh water, sound is propagated at a velocity of about 4475 feet in a second, or at a rate four times swifter than through the atmosphere. The waters of the ocean convey sound, about a seventeenth more rapidly. Ice is said to possess the power of transmission about equally with water; an easy proof of which is supplied by the tremor that may be felt underfoot on a frozen river or lake struck, at a distance, long before the sound of the blow reaches the ear. That fishes are endued with auricular organs, has been demonstrated by the late great anatomist, Mr. John Hunter. They have a strong perception of sound, even at the bottom of deep rivers; though it was not until modern times that the seat of their auricular organs was discovered.

While the theory of sound thus involves some singular questions as to its origin and first transmission, its connexion with the auditory nerves of man is also curious. The ear is the immediate and most direct instrument of this perception; but the whole of the skull bone, the palate, the teeth, and even the nostrils, assist in its functions; thus the deaf have been made sensible of sounds by holding a piece of metal between their teeth.

We should not omit to state that the extraordinary rapidity with which sound passes through solid bodies, induced philosophers to suppose, even to a very late period, that its transmission

was instantaneous; and that Sir Isaac Newton himself seems to have coincided with this. It appears now, however, perfectly clear, that its motion is in all cases progressive, and subject to regular, however mysterious, laws.

SECT. II. OF THE DIFFUSION OF SOUND.-The theories and experiments to which we have adverted, trace the transinission of sound in various important ways. Regarding the air, however, now, as the great ordinary medium of sound, we devote this section to the consideration of its functions in this respect.

Sonorous bodies seem to communicate to the air their own tremulous impression, which is then further propagated according to the laws of pneumatics. A few particles being driven from the surface of the sonorous body, propel their contiguous particles into a less space. The medium thus rarefied in one place, becomes condensed in the other; while the air thus compressed in the second place, is restored by elasticity to its former one; and the air contiguous to that becomes compressed. The air less compressed, again expanding itself, a new compres sion is made, and the motion arising from each agitation, produces an undulation of air, analogous to a wave upon the surface of the water, carrying with great velocity all the articulate distinctions and divisions of sound.

In the formation of these waves of air, the particles go and return through very short and equal spaces, after the manner of a pendulum, while it vibrates two oscillations; the velocity of the whole undulation, in the mean time, determining the force and other qualities of every simple sound.

That air is the principal vehicle of sound is universally allowed; and, that, without the medium of it, or some other fluid, we should ordinarily have no sounds at all, is proved by the experiment of a receiver, exhausted of its air, in an air-pump, when a bell, rung in the vacuum, makes no sound whatever: the fact is also now confirmed, that the force of the pulsations depend considerably upon the degree of density, or rarefaction of the air. Dr. Priestley, to ascertain whether the intensity of sound is affected by any other property of the air besides its density, provided an apparatus, with which he performed several experiments, and at last came to the conclusion that the intensity of sound depends solely upon the density of the surrounding air, and not in any measure upon any chemical principle in its constitution. In inflammable air of ten times the rarefaction of common air, the bell could be scarcely heard. In fixed air, the sound could be heard about half as far again as in common air, owing to the superior density of that air. In dephlogisticated air, the sound was sensibly louder than common air. See Experiments and Observations, vol. v. p. 296, &c. Mr. Hauksbee, also, made many experiments of a similar nature, in air of different degrees of condensation, in the course of which, a bell was heard at the distance of thirty yards in common air, at sixty with the force of two atmospheres, and as far as ninety with the force of three. (Phil. Trans. 1709, xxiv. 09, xxvi. 367, 371.)

Philosophers, however, are much divided in opinion, respecting the manner in which sound is conveyed to the ear; i. e. whether it is diffused in the air, in a circular or undulatory manner, like the waves occasioned in a smooth water, by throwing in a stone; or, whether it runs in straight lines, like the rays of light diffused from a centre, in the manner that the electrical fluid runs along a rod of iron. Sir Isaac Newton adopted the former theory, and illustrated the propagation of sound by an undulatory, or rather vermicular motion in the particles of the air, drawn from the familiar instance of the crawling of a worm, which first carries its contractions from the hinder part, to throw its fore part to the proper distance, and then carries them back to bring the hinder part forward. Something similar to this takes place in the air, when agitated by the percussion of a sounding body and thus he supposes there is an alternate condensation and relaxation of the air during one vibration and as the air in its progress forward strikes an opposing body with greater force, than in its retrogradation, Sir Isaac entitles each of these accelerated progressions a PULSE of SOUND: and as all motion upon fluids, in any direction, operates more or less, in a circular or spherical manner all around, so these sounds will be driven in all directions, forward, backward, upward, downward, and on every side, like circles in disturbed water. An idea of the rules of sound, according to this hypothesis, may be formed from observing the tone of a church bell, while its sounds are dying away, and which are owing to the alternate progression and recession of the air; for as each of these pulsations is formed by a single vibration of the string, they must be equal to each, as these vibrations are known to be.

With regard to the velocity of sound, (which will be more particularly treated of in Sect. III.) Newton has determined it by a very intricate calculation, to be in proportion to the density of the parts of the air, and the distance of these parts from each other; proving that each part moves like a pendulum; from whence he infers, that if the density of the atmosphere were the same every where as on the surface of the earth, a pendulum, reaching from its highest surface down to that of the interval, is thus lost to sense: just as a flame in proportion to the velocity. And he shows, that the velocity of each pulse would as much exceed, that of such a pendulum, swinging with one complete vibration, as the circumference of a circle exceeds the diameter. From all this he calculates that the motion of sound should be 979 feet in a second; but, upon taking an additional consideration of vapours in the air, he finds the exact velocity of sound to be 1142 feet in a second, or about thirteen miles in a minute, a proportion established by experience.

This theory of Sir Isaac Newton's met with many opposers. Even Bernoulli, his disciple, and one of his principal followers, owned he did not understand this part of his Principia. He attempted therefore to give a more perspicuous demonstration of his own, that he might confirm and illustrate the Newtonian theory. "he sub

ject seemed to reject elucidation: his theory is obviously wrong, as D'Alembert has proved in his Theory of Fluids. Various objections have been made to the Newtonian system of sounds. It is urged, that this theory can only agree with the motion of sound in the elastic fluid, whereas sounds are known to move forward through water that is not elastic. To explain their progress therefore through water, a second theory must be formed: so that two theories must be made to explain a similar effect; which is equally contrary to the simplicity of true philosophy, and of nature. It is further argued, that the slow vermicular motion, but ill represents the velocity with which sounds travel. In short, it is urged, that such undulations as have been described, when coming from several sonorous bodies at once, would cross, obstruct, and confound each other; so that, if they were conveyed to the ear by such means, we should hear nothing but a medley of discordant and broken articulations. But this is equally with the rest, contradictory to experience, since we hear the fullest concert, not only without confusion, but with the highest pleasure. These objections, have given rise to another theory: which we shall likewise lay before the reader; though it appears also liable to objections, which shall be afterwards noticed.

Every sound may be considered as driven off from the sonorous body in straight lines, and impressed upon the air in one direction only: but whatever impression is made upon a fluid in one direction, is diffused upon its surface into all directions; so that the sound first driven directly forward, soon fills up a wide sphere, and is heard on every side. Thus, as it is impressed, it instantaneously travels forward with a very swift motion, resembling the velocity with which we know electricity flies from one end of a line to another. Now, as to the pulses, or close shakes as the musicians express it, which a sounding body is known to make, each pulse is itself a distinct and perfect sound, and the interval between every two pulses is profoundly silent. Continuity of sound from the same body, is only a deception of the hearing; for as each distinct sound succeeds at very small intervals, the auditory nerves have no time to transmit its distinct images to the mind, and the interval is thus lost to sense: just as a flaming torch, flared round in a circle, appears to be a ring of fire. In this manner, a beaten drum, at some small distance, presents us with the idea of a continuing sound; and, when a child runs with his stick along a piece of railing, a continuing sound is heard, though the stroke against each rail is perfectly distinct and insulated. According to this theory, therefore, the pulses are nothing more than distinct sounds repeated by the same body, the first stroke or vibration being always loudest, and travelling farther than those that follow; while each succeeding vibration gives a new sound but with diminished force, till at last the pulses die away totally, as the force decays that gives them existence. All bodies whatsoever that are struck, return more or less a sound: but some, wanting elasticity, give back no repetition of the sound; the noise is at once begotten and les