higher. It is found by experiment that two sounds are more or less consonant, when heard together, according as the relation between their vibrations is more or less simple. Thus, when two vibrations of the first are made in one vibration of the second, (which is the simplest ratio possible, when the sounds are really different,) that similarity is observed to which we have just alluded; the first sound is called the octave of the second, and both are denoted in music by the same letter. When the number of vibrations of the two are as 3 to 2, the one which vibrates three times while the other vibrates two, is called a fifth above the other; because in the musical scale of notes

is agreeable. The same may be said of c and its sixth ▲, in which the ratio is that of 3 to 5, or of E and its minor sixth (see Music) c1, in which the ratio is that of 5 to 8; or of E and its minor third G, in which the ratio is that of 5 to 6. We write underneath, the common musical scale in the treble clef, with the denominations of the notes and the fraction of a vibration which is completed, while the first c completes one vibration, which fraction is greater than unity, as the notes are rising. Thus while c vibrates once, D vibrates once and one eighth; or 8 vibrations of c take place during 9 of those of D.

This is the musical scale pointed out by nature, since all nations have adopted it, or part of it at least. It fully verifies our assertion that the ear delights in the simplest combinations of vibrations. It would be hardly possible to place between 1 and 2, six increasing fractions where numerators and denominators should, on the whole, contain smaller numbers. We find, in the six intermediate fractions, only 2, 3, 4, and 5 singly, or multiplied by one another, no product exceeding 15. Neither has the whole of this scale always been adopted. It seems to have been formerly universal to reject F and B, the fourth and seventh of the scale; as is proved by the oldest national airs of the orientals, the northern nations, and even of the Italians. [See SCALE.]

- &c.

Fig. 11.

1

C1 Di EL Fi G1 A1 &c.
15 2 2
3 y &c.

D E F G A B 量 The following table will represent the proportions of the lengths of the sonorous waves which yield the preceding notes. These lengths decrease, as we have seen, as the times of vibration decrease, or as the numbers of vibrations in a given time increase.

Now, let two of these notes be sounded together, for example, c and G, in which two waves of c are equivalent to three of G. The resulting wave is, as we have seen in the preceding part of this article, twice as long as the wave of

c, and the curve which represents the condensation and velocity of the particles of air is compounded, as before described, of those of the waves of c and G. The ear is able to perceive three distinct sounds, one of which is almost imperceptible, and indeed inaudible, unless carefully looked for. The two perceptible sounds are those of c and G from which the wave was made; nor are we well able to explain how this can be. Undoubtedly, if the curve, which is the type of the compound wave, were presented to a mathema

pleasant sensation is derived. Thus in a passage, which has a strong echo, that is, where waves are reflected from wall to wall, as in the tube closed at both ends, already described, if the foot be struck against the ground, a faint musical note is heard immediately after the echo has ceased. By the action of the foot, shorter waves are excited, as well as the long wave, by the reflection of which the echo is caused. None of these would be repeated were it not for the reflection; but when the main sound is

tician, he would be able, with consideration and measure- | ment, to detect its elements; and to make that resolution which is done by the most unpractised ear. But we may, perhaps, assert that a savage, or a person totally unused to music, would not separate the sounds, but if c and G were sounded separately, and afterwards together, would imagine he had heard three distinct notes. The third sound, which is very faint indeed, is that belonging to the whole compound wave, which, being twice as long as the wave of c, belongs to the note called c, an octave below the first c of the preced-weakened by reflection, the shorter waves begin to produce ing scale, which may be denoted by c,. We may perhaps give an idea of this combination in the following way :-Let us suppose a series of equidistant balls to roll past us at the rate of two in a second, and another series at the rate of three in a second,—and let us moreover suppose that these balls roll in tubes placed one over the other, so that we only see each as it passes an open orifice in its tube, as in the figure.

Fig. 13.

It is evident that we thus obtain three distinct successions: 1, that by which we might count 3 in a second from the lower tube; 2, that by which we might count 2 in a second from the upper tube; 3, that by which we might count single seconds, from observing when two balls pass together, and waiting till the same happens again. And we must recollect that any sound, however unmusical in itself, produces a musical note, if it be repeated regularly and often; so that it is not from the phenomenon itself, but from the frequency of its succession at equal intervals, that the

19

the effect of a musical note, being, as we must suppose, less weakened than the longer wave. And we may here take occasion to observe, what will be further discussed in the articles PIPE and CHORD, that it is difficult to excite a perfectly simple wave, unaccompanied by shorter ones, which latter are always contained an exact number of times in the longer. Thus, if the note called c1, or an octave below c in fig. 11, be struck on a piano-forte, the sounds G and ɛ1 (see the figure) will be distinctly heard as c becomes weaker, the waves of these notes being respectively onethird and one-fifth of those of c. When two notes are struck together, the effect is not pleasing, except when the numbers of waves per second in the two bear a very simple proportion.

We have noticed all the cases which the musicians call concords; the remainder, though contributing much to the effect of music, being called aiscords. Thus, if F and G be sounded together, in which (fig. 11) F makes of a vibration while & makes, or F makes 8 vibrations while G makes 9, the effect is disagreeable, at least if continued for some time. On the piano-forte, in which the notes when struck subside into comparative weakness, this is not so much perceived; but on the organ, in which the notes are sustained, the effect is intolerable, and accompanied by an apparent

shaking of the note, producing what are called beats, which of the voice. For information as to the use made of these we shall presently explain. Nevertheless, it becomes en- beats, see the article TEMPERAMENT. durable, if not too long continued, provided r, the discordant It only remains to consider the different character of note, as it is called, is allowed to pass to the nearest sound, sounds. The same note, as to pitch or tone, may be sounded which will make one of the more simple combinations of by a horn and a flute; nevertheless, each instrument has a vibrations with G. The nearest such sound is E, which character of its own, which enables every one to distinguish makes 5 vibrations, while & makes 6. For further imforma- between the two. It is not to the different loudness of the tion, we must here refer to the article HARMONY. two, for either, by skilful players, may be made to give the weaker sound; neither does it depend on the number of vibrations, for that, as we have seen, determines only the pitch of the note; the only difference between one wave and another of the same length, is in the form of its type; that is, in the different manner in which the air is condensed and rarefied. There is also only this feature left, to account for the difference between the tones which different players will draw out of the same instrument; since both Paganini and an itinerant street musician would make the same string vibrate the same number of times in a second. The late Dr. Young, to whom the world is much imdebted on this

We now come to the absolute number of vibrations made by musical notes; all that we have said hitherto depending only upon the proportions which these numbers of vibrations have to one another; so that any sound might be called c, provided the sound produced by twice as many vibrations in a second were called c1, and so on. We do not know that any measurements have lately been made in this country, but, from the Memoirs of the Academy of Berlin for 1823, it appears that the middle A of the treble clef, or the A in fig. 11. was produced by the following numbers of waves per second in the following different orchestras, showing a small variation between them, but one by no means insen-subject, as on almost every other, examined the string of a sible to the ear.

From this we may form an idea how many vibrations are necessary to create the sensation of a musical sound, and also at what point of the scale the vibrations per second would become so numerous that this effect should cease. If we take one of Broadwood's largest piano-fortes, and recollect that they are generally tuned (for private purposes) a little below the pitch of the orchestra, we shall not be far wrong in assuming that the A above-mentioned on these instruments is the effect of 420 vibrations per second. The lowest note, which is almost inappreciable, (that is, though perfectly audible as a sound, yet hardly distinguishable from the notes nearest to it), is the fourth descending c from this A, and the highest is the third above it, though the c above that, or the fourth ascending c from the A, can be well heard, and may be had by whistling into a very small key. We must however remark, that the point at which a series of undulations ceases to give a sound either from its slowness or rapidity, is different to different ears; sometimes so much so, that while one person complains of a note as too shrill, another cannot hear it at all. We write the above scale below, putting the A whose vibrations we know in its proper place,

C3 C2 C1 CACI C3 C3 C4.

2

1

On looking at fig. 11, we see that A makes 5 vibrations while c makes 3; that is A making 420 vibrations per second, c makes 252; therefore c, makes the half of this, or 12; c, makes 63, and c 31. Again, c1 makes twice as many vibrations per second as c, or 504; c2 makes 1008, c3 2016, and 6, 4032 vibrations per second. That is to say in round numbers, the ear receives a musical impression from any sound which arises from a number of vibrations between 30 and 2000; and we may certainly say that, in every orchestra, the hearers are employed in distinguishing and discriminating between various rates of succession in the undulations of the air around them from 60 to 2000 per second.

violin when in motion, and by throwing a beam of light upon it, and marking the motion of the bright spot which it made, he found that the string rarely vibrated in the same plane, but that the middle point would describe various and very complicated curves, corresponding to different manners of drawing the bow. [Lectures on Natural Philosophy, vol. ii. plate 5.]

We give three specimens merely to show how much the vibration produced by one player may differ from that of another. The waves proceeding from all three will be of the same length, the vibrations being performed in the some time; but the condensations and rarefactions will evidently be such as to give very different relative states to contiguous particles of air. The middle of the stretched wire de

Fig. 14.

scribes the curve on which it is placed during what we have hitherto called two vibrations.

It might tend to throw light upon this part of the subject, if practical musicians would observe in the same manner the curves which they produce, and describe the different qualities of tone arising from them. As yet, we have no direct experiments which tend to connect any particular form of vibration with any particular quality of sound. We shall enter upon the best method of doing this in the article CHORD.

Some confusion arises in books on this subject, from the use which different authors make of the words vibration and wave. Some mean, by a vibration, a motion to and fro, which in this article, we have called two vibrations; and by a wave, the complete succession of condensations and rarefactions, which we have called two waves, one of condensation, the other of rarefaction. For further information, we refer the reader to Sir J. Herschel's article already cited, to Robison's Mechanical Philosophy, Biot's Precis Elementaire de Physique, and Pouillet's Traité de Physique.

We have previously alluded to a phenomenon of sound, or rather of combined sounds, called a beat. If two notes whose vibrations are either nearly in the same ratio, or nearly in one of the simple ratios above-mentioned, be sounded together, the effect of their being out of tune is a tremulous motion of the sound, the pulsations or beats of which can be counted if the notes be not too high. For example, suppose two simultaneous notes whose vibrations are 100 and 104 per second. Here 25 vibrations of the first are made during 26 of the second; and the reader who has studied the preceding part of this article will see that the resulting wave is as long as twenty- ACQUAPENDENTE, a town in the Roman States, six of the second waves; but that if the waves from the two near the confines of Tuscany, on the high road from Flobe much alike in their types, this resulting wave will consist rence to Rome. (Lat, 42° 46′ E., long. 11°. 52'.) The name of a cycle of rarefactions and condensations very much is derived from the fall of water from the rock on which it resembling the separate waves. The whole resulting wave stands. It is built on a steep hill which rises above the river being twenty-six times as long as the second wave, will run Paglia, and is surrounded by walls. Girolamo Fabrizio, a celethrough all its changes four times in a second, which is not brated anatomist and professor of Padua in the sixteenth sufficient to give a musical sound, but will only add to the century, was a native of this town. It was but an insound of one of the waves the periodical tremulous sensation significant place until 1650, when Pope Innocent X. having which is called a beat, which may be imitated by ringing razed to the ground the neighbouring town of Castro, the syllables who, ah, in rapid succession on the same note where a bishop had been murdered, transferred the see to VOL. I.-O

NO. 13.

ACQUITTAL (from the French acquitter, to free or discharge) signifies a deliverance and setting free of a person from a charge of guilt; thus a man who, upon his trial for a criminal offence, is discharged by the jury, is said to be acquitted. The acquittal by the jury has, however, no force in law until judgment has been given upon the verdict by the court in which the proceedings are instituted.

Acquapendente. The town looks ill-built and dull; it place very strongly, and built a new mosque, according to belongs to the delegation or province of Viterbo, and is Turkish fashion adorning it with columns that once belonged seventy miles N. N. W. of Rome. It contains a cathedral, to the old Greek edifices of the neighbouring cities. The and about 2400 inhabitants. streets of Acre are narrow, and the houses, which are of stone, have flat roofs. The port is small and not deep, yet it is one of the best along this coast. Europeans carry to Acre cloth, lead, tin, &c., and receive in exchange some cotton and rice. The great celebrity of Acre, in more recent times, is owing to Bonaparte's attempt to storm the place in the spring of 1799, when he entered Syria at the head of 12,500 men. The obstinate defence of the garrison commanded by Jezzar, and aided by Sir Sidney Smith with English sailors, saved Acre from the repeated assaults of the French general, who, after spending more than sixty days before it, and losing near 3000 men, retreated to Egypt. Since the seige in 1799 the fortifications have been repaired, but, in the last year (1832), Acre has had to withstand another seige, and is at present in the hands of the Pasha of Egypt, who took it from the Sultan of Constantinople, his master, on the 2d of July.

After judgment of acquittal, if the party be indicted a second time for the same offence, he may plead his former acquittal as a bar or a complete answer to the second charge, and upon such former acquittal being admitted or proved, the person indicted will be entitled to be discharged, as the law will not permit a man to be twice put in danger of punishment for the same offence.

ACQUITTANCE is a discharge in writing of a debt, or sum of money due. A general receipt or acquittance in full of all demands will discharge all debts, except such as are secured by what are termed specialties, viz., bonds and instruments under seal; which are considered by the law as of too great force to be discharged by a verbal concord and agreement, or any less formal and solemn acquittance than a deed. Where an acknowlegement of satisfaction is by deed, it may operate as a good answer to an action on the debt, even though nothing has ever been actually received. Courts of equity, and even courts of law, will in some cases order accounts to be gone into anew, notwithstanding the production of a general acquittance or receipt in full of all demands, upon proof that such acquittance was obtained by fraud or given under a mistake, and that the debt or other demand has not been in fact satisfied.

ACRE, a measure of land, of different value in the different parts of the United Kingdom. When mentioned generally, the statute or English acre is to be understood. Its magnitude may be best referred to that of the square yard by recollecting that a square whose side is 22 yards long is the tenth part of an acre; whence the latter contains 22 x 22 x 10, or 4840 square yards. The chain with which land is measured is 22 yards long; so that ten square chains are one acre. This measure is divided into 4 roods, each rood into 40 perches, so that each perch contains 30 square yards. Thus::

Acre is also the name of one of the Syrian pashalicks which in late years has been bounded to the north by that of Tripoli, to the south and east by the pashalick of Damascus, and on the west by the Mediterranean. Its chief ports are Acre and Beirout. We propose to describe the whole country under the more permanent and general name of SYRIA.

ACROCHO'RDUS (a word formed from the Greek, which signifies a wart), in Zoology, a genus of serpents discovered in Java by the traveller Homstedt, and described in the Memoirs of the Stockholm Academy of Sciences for 1787. This genus is easily distinguished from others of the innoxious family of serpents by the innumer. able small scales which cover every part of the head and body both above and below, and which in preserved specimens, or when the live animal distends the lungs and body with air, assume the appearence of so many granulated warts or tubercles. This circumstance has suggested the name of acrochordus, which conveys a pretty accurate idea of the external covering of the animal described in Homstedt.

5.5

The Irish acre is larger than the English, inasmuch as 1000 Irish acres are very nearly equivalent to 162 English acres. More correctly, 121 Irish acres are 196 English acres; but the former ratio points out an easier arithmetical operation, and will not be wrong by so much as one acre out of 5000.

The Scottish acre is also larger than the English, 48 Scottish acres being equal to 61 English acres. There are also local acres in various parts of England, such as the Cheshire acre of 8 yards to the pole. The English statute acre is used in the United States of North America.

The French Are is a square whose side is 10 metres, and 1000 English acres are equivalent to 40,466 ares.

For further information on the comparison of English and other acres, we refer the reader to Kelly's Cambist, a very useful work.

ACRE (ST. JEAN D'), a town of Syria on the seacoast (N. lat. 32° 54', E. long. 35o 4'), and on a small promontory, which, with Mount Carmel lying to the south, forms a circular bay: it is sometimes called Acra and Acca. [Acrochordus, from Lacepède, Hist. Des Ovipar.] Its oldest name was probably Acco, which was changed to The acrochord, in fact, is covered with scales, like all other that of Ptolemais during the sovereignty of the Greeks in serpents, though they are minute and separate from one Syria: the name of Acco was revived after it fell into the another: each of them is marked with three small ridges, and hands of the Saracens. Acre is well known in the history it is only when the skin is inflated and apparent between the of the Crusades, having been taken in 1191 by Philip scales, that these assume the granulated or warty appearance Augustus of France and Richard 1. of England. It was for expressed by the name. The head of the acrochord is flat, some time in the possession of the Knights of Malta, during the mouth provided with a double row of small, sharp teeth, whose occupation it was strongly fortified, and filled with but without poison fangs, and the throat capable of enormous churches. Acre was in a very ruinous condition in the dilatation. Though deprived of the ordinary apparatus by middle of the seventeenth century, when Thevenot visited which venomous serpents convey their poison, zoologists it, but it has since been improved, and is now said to contain are not yet agreed in considering the acrochord as altogether 15,000 (some authorities say 20,000) inhabitants. This innocent. M. M. Appel, and De Blainville affirm that they restoration was due to Sheik Daher, who, in the middle of have found a peculiar bone in the head of this serpent, which the eighteenth century, strengthened the town and revived they conceive to supply the place of the poison fang. its commerce. Jezzar Pasha, his successor, fortified the Cuvier, on the other hand, denies the existence of this

bone altogether, and brings forward the testimony of M. | Leschenhault in favour of the harmless nature of the acrochord; and as the latter gentleman travelled for some time in Java, and made various experiments upon the live animals, for the purpose of ascertaining this point, there seems to be no reason to doubt the truth of his report. The tongue of the acrochord is short and thick, the vent simple and without the horny spurs which are common to many other genera of serpents. The only species sufficiently known at present is

loftier and more commanding eminence than that of Athens. The view from the summit is extensive, and the temple on the Acropolis of Athens, nearly fifty miles distant, is distinctly seen. An eminence close upon the modern Argos in the Peloponnesus was the Acropolis of the ancient Argos, and then it was called Larissa. A ruined castle of comparatively modern construction occupies the summit of this rocky eminence, and shows in some parts traces of much earlier building. The Acropolis of Messene in the Morea, situated on Mount Ithome, is another remarkable specimen The Oular Carron of the Javanese, the Acrochordus Java- of these natural bulwarks which were once fortified according nicus of Lacepède and others. The scales of this serpent are to the principles of Greek military science. [See Leake's marked by three small carinated elevations; the body is black Morea, 3 vols. 8vo.-Society's Plan of Athens.] above, greyish-white beneath, and the sides are marked with ACROSTIC, a Greek term, signifying literally the beblack spots on a ground of the same colour as the belly. The ginning of a line or verse. An acrostic is a number of verses head is covered with small scales, the mouth is contracted, and so contrived that the first letters of each, being read in the the under jaw shorter and broader than the upper. This animal order in which they stand, shall form some name or other averages from six to eight or ten feet in length, and its shape word. According to some authorities, a writer named Poris altogether peculiar; the body does not gradually become phyrius Optatianus, who flourished in the fourth century, thinner from the middle towards either extremity, as in the has the credit of being the inventor of the acrostic. It is generality of serpents, but grows gradually thicker from the probably, however, of older date. Eusebius, the bishop of head to the vent, and there suddenly contracts, so as to form Cæsarea, who died in a. D. 340, gives in his Life of Cona very short, slender tail. In the thickest part of the body, stantine, a copy of Greek verses which he asserts to be the immediately above its junction with the tail, the individual composition of the Erythræan Sibyl, the initial letters of procured by Homstedt, of which the entire length was eight which make up the words ΙΗΣΟΥΣ ΧΡΙΣΤΟΣ ΘΕΟΥ ΥΙΟΣ feet three inches, measured three inches in diameter, whilst ETHP, that is, Jesus Christ, the Son of God, the Saviour. the greatest breadth of the tail did not exceed half an inch, These verses, which are a description of the coming of and its length was scarcely a ninth part of that of the whole the day of judgment, have also been translated into body. This individual was a female, and, when opened, was Latin hexameters so as to preserve the acrostic in that found to contain five young ones perfectly formed, and about language, in the words JESUS CHRISTUS DEI FILIUS SERnine inches in length. It was caught in a plantation of pep-VATOR. The translation, however, wants one of the wonderper-trees, and the Chinese, who accompanied Iomstedt, ful qualities of the original; for it will be observed that the cooked and ate its flesh, and reported it to be of a most deli-initial letters of the five Greek words being joined together, cious flavour. The stomach contained a quantity of half-di- form the word Ixorz, that is, the fish, which St. Augusgested fruit, from which it has been inferred that this serpent tine, who quotes the verses in his work entitled De Civitate is frugivorous, and, contrary to the habit of all other known Dei, informs us is to be understood as a mystical epithet of species, feeds upon vegetable substances. Cuvier is incre- our Saviour, who lived in this abyss of mortality without dulous upon this point: it is certainly a singular circum- contracting sin, in like manner as a fish exists in the midst stance, and should be received with caution; but, on the of the sea without acquiring any flavour of salt from the salt other hand, we have no reason to doubt the testimony of water. This may be therefore called an acrostic within an Homstedt; and the mere singularity of the fact does not acrostic. But there are also other ways of complicating necessarily destroy its probability. We know, moreover, that these ingenious productions. Addison, who notices this tortoises, turtles, some genera of fishes, and even certain along with other sorts of false wit, in his lively papers on species of lizards, -all of them cold-blooded animals, and some that subject in the first volume of the Spectator, says, there approaching very nearly, in nature and organization, to the are compound acrostics, where the principal letters stand two family of serpents to which the acrochord belongs,-live or three deep. I have seen some of thein, where the verses entirely upon vegetable food; and the knowledge of this have not only been edged by a name at each extremity, but fact ought to prepare us beforehand to expect the discovery have had the same name running down like a stream through of similar habits among certain tribes of serpents, rather the middle of the poem.' There are even instances of the than to reject them as impossible and as absurd fictions. same name being five times repeated in so many successive ACRO NYCHAL (sometimes incorrectly written Acro- columns. Such an acrostic has been designated a pentanical, and Achronical), a word derived from the Greek, sig-crostic. This species of elaborate trifling was extremely nifying that which determines the extremities, or the begin- fashionable among the early French poets, from the age of ning and end, of the night.' It is only used in reference to Francis 1. down to that of Louis XIV. Some also of our the rising or setting of the stars; and a star is acrony- English poets of considerable eminence used formerly to chal or rises acronychally when it rises at or very near sun- amuse themselves in the same way. Thus, for instance, set, and consequently sets at or near sunrise. To deter- among the works of Sir John Davies, are twenty-six short nine what stars rise acrony chally on any given night, elevate poems entitled Hymns to Astrea, each of which is an the pole of a common globe so that the arc intercepted acrostic on the words Elizabetha Regina. These, which were between it and the horizon may be equal to the latitude first published about the end of the sixteenth century, are of the place. Turn the globe until the sun's place is on perhaps the most elegant compositions of this description in the horizon at the western side, then will all stars which any language. Afterwards such puerile ingenuity fell into are either on or within a short distance of the horizon on disrepute; and Dryden, in his Marflecknoe (published 1682), the eastern side be acronychal. contemptuously makes the dying monarch of the realms of nonsense and dulness address his son and successor Shadwell:

ACRO'POLIS, a Greek compound word signifying the highest point of a city.' It was used to denote some hill, rock, or natural elevation, such as we find forming part of the sites of many ancient cities in Greece. It seems natural to conclude that such strong holds were among the places first occupied, and that they served as the kernel of a larger city. In course of time, when building spread, such eminences became strong posts analogous to castles or citadels in modern cities; and in many instances the possession of such posts was considered as equivalent to the possession of the cities themselves. Religious edifices also generally formed part of the structures of an Acropolis.

Leave writing plays, and choose for thy command

Some peaceful province in acrostic land '

་

The acrostic, being addressed merely to the eye, and conveying no pleasure either to the imagination or to the ear, cannot of course add to the poetical effect of the lines which it ornaments-any more than would the printing of the initial letters in a differently coloured ink. But it is sometimes useful, as an aid to the memory, in recollecting such verses as are composed only to be got by heart, for the sake of the facts of which they forin a summary. Thus, in some In modern times they have often served as places of refuge editions of the Latin dramatist Plautus, we find prefixed to to the inhabitants from the attacks of an enemy, or from each play a few verses which contain at the same time an the incursions of corsairs. The term Acropolis is now most acrostic on its name and a sketch of the plot. In this commonly applied to the rocky eminence of Athens, on case, the knowledge of the initial letter of each line must which the remains of the Parthenon or Temple of Minerva help the memory to recover it, if it should be forgotten. stand; but this is only a limited use of the word. Corinth There are two epigrams in the Greek Anthology, one in had an Acropolis called Acro-Corinthus, which is a much honour of Bacchus and the other of Apollo, which are called