Precisely similar in principle to this is the Eolina, a little instrument now very common in London. It varies from two to six inches in length, and from one to two in breadth. Along one edge is a row of holes, into which the player blows with his mouth. Each hole is devoted to a separate note, and the whole, varying from four to twelve in number, are harmonized in some determinate order. The breath which is blown into any one hole escapes at another aperture; but it cannot do so without striking against a little metallic tongue, and setting it in vibration, by which the sound is elicited. The springs in connection with the holes are retuned to a certain scale, so as to harmonize with one another.

As this construction is the germ from which many others proceeded, we must explain the action of the spring a little more fully. Let an oblong hole be cut in a metal plate, and a thin metallic spring be formed, almost exactly fitting this aperture, but still a minute degree smaller, so that when the spring is fixed at one end nearly the whole of the remainder will oscillate throught the aperture in the plate. If the plate be now strongly blown upon, part of the air will insinuate itself round the edges of the spring, and setting the latter in vibration, will elicit a musical tone bearing considerable resemblance to that of the hautboy (oboe). The pitch of the tone produced will depend on the proportion between the length and the thickness at the fixed end and at the vibrating end. With any given thickness, the longer the spring, the lower is the tone produced, and with any given length the thinnest spring yields the lowest note. In addition to this, if a spring yielding a given note be made thinner near the fixed end, the sound becomes more grave; but if near the vibrated end, it becomes more acute. From these two rules therefore, it is easy to see how an ingenious workman with a correct musical ear can adjust a serious of springs so as to produce any desired range of notes. It he requires all the natural notes in an octave for instance, he will have eight apertures cut in the metallic plate, and adjust the lengths and thicknesses of eight metallic tongues until they yield the notes C D E F G A B and C. It is in the mode of conveying air to a series of springs such as this, that the main difference between the various instrument which we have mentioned exists.

In 1830, Mr. Faraday delivered a lecture at the Royal Institution on the construction of these instruments and of others more or less ressembling them; and after stating that many contrivances had been made to facilitate the playing of such an instrument, he spoke of the desirability of connecting the springs with the mechanism of an organ or pianoforte, and described such an attempt nearly as follows. It was found that the steel springs might be made to yield any note within the compass of a keyed instrument, while that for the lowest note was not more than four inches in length and one in breadth; so that the mechanism would occupy less space than the smallest cabinet pianoforte. Some difficulties attended the accomplishment of this design; for the springs, under certain circumstances, were bent by the mere vibration beyond the elastic strength of the metal of which they were composed: the consequence was a gradual disintegration of the metal and an alteration of tone, which increased, until at length the springs were actually broken off by use. Another formidable difficulty arose from the tardiness with which the vibration of the spring commenced when the air first aced on it; so that a note when struck did not immediately yield its sound. Means were however adopted that completely obviated both these defects; and in 1829 the Society of Arts presented a medal to Dr. Dowler for an instrument constructed on this principle with keys. The bellows were placed underneath, and the springs arranged over a continued wind-chest, furnished with a valve to each note. The springs, or as they have been called, the tongues, with the exception of the highest octave, were made of an alloy, called German silver, or electrum, which is composed of a mixture of copper, zinc and a little nickel. The springs of the remaining octave were manufactured from extremely thin sheet steel, imported into this country from Switzerland. This instrument was tolerable of its kind, but inferior to one which has been made by Mr. Day, an ingenious mathematical instrument maker, who has considerably improved the manufacture of the springs.

This was the state, in 1830, of an instrument which by subsequent improvements has attained the name of the Seraphine in later times; but at the time alluded to there was an inequality and harshness of the tones, which caused the lecturer to doubt whether, without great improvements, it would ever become a popular instrument.

Somewhat about the same time period Mr. Wheatstone, who has distinguished himself by his researches in sound generally, constructed a little instrument called the Symphonium, which was in fact a keyed Eolina. The instrument was constructed in several different shapes, and was played upon by the fingers somewhat in the manner of a flageolet. The mouth was applied to the mouth-hole, and the fingers, touching small projecting pins, raised the valves which covered the apertures in a plate, and this allowed air to pass through the apertueres and elicit sounds from metallic tongues placed there. It was also proposed by the inventor that instead of blowing air into the instrument by means of the mouth, a small round pair of bellows should be attached to it in such a manner that a current of air could be forced through the instrument and made to act on the metallic springs.

This application of bellows to the Eolina or to the Symphonium brings us at once to the Accordion, an instrument in which springs keys and bellows ar ingeniously combined. We do not know whether the patentee of this instrumentn belongs to England, France or Germany, but nearly the whole of them are made in the two last-named countries.

Most of our readers are probably familiar with the external appearance of an accordion. We may consider it as a rectangular pair of bellows, varying from six to about fourteen inches in length, and from three to six in width. There are from six to twenty finger-keys attached to one of the boards, in a manner convenient for the player; and these keys are in connection, by means of wires, with an equal number of circular valves or stops, which cover circular holes perforated through the board or face of the instrument. Immediately beneath the perforation is a series of oblong apertures with metallic tongues vibrating freely in them, and beneath the tongues is the open cavity of the bellows. The vibrating tongues are not all in communication with each other, there being two placed under each circular hole, and cut off from those in the vicinity. Of the two which form each of these clusters, one can only vibrate when it is impelled by wind from above, and the other when it is similiarly impelled from below. This is affected by means of little valves placed below in the one case, and above in the other: the action of valves in a pump will sufficiently explain this.

The tuning of the instrument is thus managed. Suppose, for simplicity of illustration that there are only four finger-keys; these will open as many circular holes; but as each hole is connected with two springs, eight notes can thereby be produced. The two springs opening under one hole are made to yield adjoining notes in the musical scale, so that the first key is in connection with the springs C and D, the second with E and F, the third with G and A, and the fourth with B and C, thereby making up an octave. Nearly the same plan is observed when the number of keys is greater, except that in some complicated instruments all the semitones, as well as the natural notes, are introduced.

This being the arrangement of the keys, the mode of plaaying is as follows: there are no openings in the case of the instrument but what are stopped by keys; so that some keys must be touched before the bellows are drawn out, else there would be a partial vacuum in the instrument, and it would be liable to burst. Suppose then we draw out the bellows and press down the key in connection with the springs C and D, the circular hole is opened - air enters - passes by one of the springs (say D) into the body of the instrument, and sets the spring into vibration, thus eliciting its sound. On closing the bellows the air rushes back again, but cannot pass the spring D on account of a valve placed there, but passes the spring C, and elicits its sound. But if we want any other two notes, say E and F, we touch the adjoining key, draw out the bellows to produce one note, and close them to produce the other. By a skillful choice therefore of the keys which we touch, we can go through all the varieties of a melody, and even of harmony by using two or three keys at once.

There is also an extra key to produce a harmonized chord, or bass; a key to act as a vent without producing sound, and a variety of intricate contrivances which could not be adequately explained without a longer description than we can devote to them. But the foregoing will suffice to give a general idea of the instrument.

We have to speak lastly, of an instrument which, for beauty of sound, facility of playing, and extent of power, excells all which have been here mentioned - we mean the Seraphine. This instrument, as constructed by Mr. Green and other able makers at the present time, appears to be similar in principle, as regards the more prominent points, to the one alluded to in Mr. Faraday's lecture, but a continued series of improvements has brought the instrument to a high degree of excellence.

The Seraphine is about the size of a chiffoniere or small pier table, and the bulk of the instrument is occupied by a cavity serving the office of a wind chest, into which wind is forced by means of a pair of bellows worked by the foot of the performer. At the top of the wind-chest is a metallic plate perforated with as many oblong apertures as there are notes in the instrument, generally about five octaves; in these apertures vibrate as many metallic tongues, in the manner before described. The apertures are covered above by valves connected with the finger-keys, so that when a key is pressed down by the finger, and a current of air is forced up from the bellows through the wind-chest to the springs, the spring governed by the key in question is set into vibration, and will continue to sound as long as the bellows are worked. There is thus a considerable difference between the accordion and the seraphine, for in the latter the air passes only one way past the springs, while in the former it passes both ways; one key governs two springs in the accordion, but only one in the seraphine. There is an occasional advantage resulting to the accordion from these circumstances, but the balance is decidedly in favour of the seraphine, since a performer can elicit any number of notes from one to ten at once; or two players could sit down at the instrument, and, if required, could produce twenty notes at once.

The bellows are, as we have said, worked by the feet of the performer by means of a pedal. But as it required some practice to effect this where the performer has not been accustomed to an organ, there is sometimes a handle brought out at the end of the instrument, by which the bellows are worked.

The difference between a sounding-board and soft cushions in their effects on sound was never perhaps better exemplified than in the seraphine. If the cover of the instrument be removed, the sounds have a power and grandeur nearly equal to that of an organ. If a piece of leather be laid on, the tones are instantly changed in character; and when a soft stuffed cushion is similarly applied, the sounds have much of the sweetness of the hautboy. The performer is provided with a means of varying the number and thicknesses of the cushions and covers employed, by which a considerable range in the character of the sound is attained. The reader is probably aware that the organ owes much of its power to a facility of producing notes resembling more or less those of several different instruments. A similar power, together with the compactness and portability of the instrument, has caused the seraphine to be much used in chapels and small churches. Not unfrequently it occupies a place in the ministers's pew and is played upon by some of his family. The practical or manual skill required in playing is probably midway between that required for the piano-forte and that for the organ.

The most difficult part of the manufacture of this instrument, and the one in which the makers find fewest workmen able to assist them, is in adjusting the springs to the proper pitch. The minutest particle of metal scraped from them will alter the pitch, by altering the rapidity of vibration. A delicate hand, a correct ear, and great patience are the grand requisites.

In closing this paper we wish to remark that we have not professed to enter at all upon the subject of precedence in the invention of several of these instruments. We may however observe that Mr. Green states the first idea of the Seraphine to have been suggested to him by a contrivance of an ingenious mechanic in Germany several years ago. With regard to instruments of the accordion kind, we may remind our juvenile readers of certain little wooden dogs which have been sold at fairs and toy-shops for more than one generation, and from which a queer sort of bark or squeak is elicited by the action of bellows under his feet, forcing wind through an aperture. May we not dignify this with the name of a primitive accordion?