following with the eye the motion of the bell as indicated by the arrow in No. 2, she will be seen to turn over, bringing the fillet G past N; then, winding the rope round the wheel as she moves, she will arrive at the position of the bell in Fig. 3—this is called the 'back-stroke' blow.
The first thing a ringer has to learn is so to swing his bell by the use of the rope, that he can be quite certain to bring her from one stroke to another, pulling her with proper judgment, so as just to throw her over the balance as shown in Figs. 2 and 3. If however too much force is used, there is a danger of breaking the stay or some other part of the machinery, and the ringer himself may be seriously injured.
An alteration in the method of hanging the bell to the stock has been invented by Sir E. Beckett, though only occasionally carried out. By the ordinary make the 'canons' for hanging are so arranged as to serve only for one position of the bell in regard to the stock, so that turning the bell in order to get the stroke of the clapper in a new position, after it has worn the bell, is impossible. Sir E. Beckett's plan consists in having only four instead of six canons, at right angles to one another and forming a cross, on plan, on the crown of the bell. By this means the position of the bell can be altered by merely unstrapping it and turning it on the stock. As the clapper must always fly in the same plane, it is in this plan bolted to the stock, the bolt passing through a hole in the centre of the crown of the bell.
[ C. A. W. T. ]
BELLY. The belly or upper part of the instruments of the violin tribe, is perhaps the most important of all, as it is the first to receive through the bridge the vibrations of the strings, and to communicate them to the whole body of the instrument. Soft wood being more easily set in vibration in all its parts, the belly is invariably made of deal, while the back and sides, which are not intended to vibrate to the same extent, but rather to throw back the waves of sound, are made of harder wood—maple.
As a rule, wood of narrow grain is preferred for the belly, although there are some fine old instruments with bellies of wide-grained wood. The thickness of the belly is also of very great importance: if too thick, the instrument will be weak in tone; if too thin, the tone will be hollow and bellowing. The power of resonance is enhanced by the slightly arched form of the belly. The wood is thickest in the centre, and gradually gets thinner toward the sides. The gradation in which this is executed varies greatly with different makers, and also depends on the special qualities of the individual piece of wood of which a belly is made. The position and shape of the so-called f-holes likewise greatly influence the quality of tone. The great makers of the Brescia school, Caspar da Salo and Maggini, made the f-holes large and almost upright; the Amatis, Stradivari, and Guarneri gave them a more slanting position, made them smaller, and infinitely more graceful in shape. Close to the edge the belly is inlaid with a single or double line of purfling, which is merely intended to improve the outward appearance of the instrument.
[ P. D. ]
BELLY or SOUNDBOARD of pianoforte. (Fr. La Table d'harmonie; Ital. Tavola armonica; Ger. Resonanzboden, Resonanztafel). The broad flat of wood, usually of Swiss pine, extended under the strings of a pianoforte, and connected with them by a bridge of hard wood over which they are stretched, is technically called the belly, but is also called the sound- or sounding-board. The strings when set in vibration, owing to their small surface in contact with the air, would be scarcely audible, were it not for the belly, an auxiliary vibrating body of large surface, to reinforce them. Thus the tone of a pianoforte essentially depends upon the movement and variable pressure of the strings at the point of contact with the bridge, by which their vibrations are conveyed to the belly to be intensified by the vibrations of the fibres of this elastic support. There is no sonorous body for which we may calculate movement under varied conditions, and then verify the calculation by trial, to compare with a stretched string. The problem is far more complicated of a resonant surface, as the belly, and appears to have offered less attraction to research. We are mainly indebted to Chladni for what we know of the forms of vibration of resounding substances. His determination of the nodal lines by means of fine sand placed upon vibrating surfaces has been of great importance to theory, and has been the foundation upon which the law of the practice of ribbing the belly diagonally to the direction of the grain with slender bars of pine has been finally established by Dr. Schafhaeutl, who has proved that this contrivance creates nodal lines of rest, and prevents the transversal vibration of the belly as a whole which would be inimical to the production of tone. But up to this time, in the construction of bellies, experiment alone has effected what has been achieved. The difference in the character of tone of pianofortes by different makers, depends very much upon variations in the proportions, direction of the grain, and barring of the belly; but as other important variations of structure invariably and simultaneously exist, the question is too complex