termination the surface weights have gently to resume their compressing force on the wind. But if the stroke be begun or concluded too suddenly there will be a momentary over-compression or a jerk in the wind, resulting in either case in a disturbance of the smooth sounding of the pipes.
Again, if several large pipes are sounded together, by many bass keys being put down simultaneously, there will be a great demand upon the wind supply, and a consequent possibility of the small pipes in the treble not being properly 'fed,' the result in that case being a momentary weakness or tremulousness in their speech. On letting the several bass keys suddenly rise, the consumption of wind would as suddenly be checked, and by thus causing for a moment a slight over-compression, the sensitive small pipes would sound too sharp and strong. These tendencies suggested the application of a small self-acting reservoir in the immediate neighbourhood of the pipes, which should add to or subtract from the ordinary wind-supply as occasion might require; and such an apparatus was successfully devised by the late Mr. Bishop, which consisted of side and end ribs, and a board, not unlike a small 'feeder,' with strong springs behind placed horizontally or vertically over a hole cut in the wind-chest or wind-trunk, the whole being called a 'concussion bellows.'
When at rest the concussion bellows stands about half way open, and charged to that extent with air. If a sudden and great demand is made upon the wind it immediately closes, adding its contents to the average supply; and if there is likely to be a redundance it expands, and so reduces it to the average.
[ E. J. H. ]
BELLS. Musical instruments of metal, sounded by percussion, and consisting of a cup or bowl, caused to vibrate by the blow of a 'clapper' or hammer on the inner or outer surface of the bell. The external stroke, however, is only applied in special cases, as when a large bell is connected with a clock, and the hours struck upon it with an external hammer worked by mechanical means; or when a series of bells are arranged so that set compositions can be played upon them by a series of such hammers, and with musical precision. [See Carillons.] A fixed bell can also be played by an internal hammer pulled or struck against the inside. But the essential and typical form of the bell is that in which the stroke is given by a movable clapper hung within the bell, and caused to strike by swinging the latter, either by hand (in the case of small bells) or by a wheel and pulley system in the case of large ones. Bells have also been extensively used as personal ornaments and decorations, from those on the hem of the garment of the Jewish high-priest to those which formed the appendages of the head-dress of the mediaeval jester. This decorative use of bells has also been applied to domestic animals; and the bells of the English waggoner's team were formerly as common an appendage as the sheep-bells and goat-bells in Switzerland and elsewhere, and the cow-bells in the New Forest, still are. In these cases the sound of the bell is excited by the movements of the body. But in all these forms or applications of the bell the principle is the same; it is an instrument with a hammer hung loose inside it, and caused to sound by the agitation, regular or irregular, communicated to it, and by which the hammer is made to strike against the inside. It is important to note this as the essential characteristic of bells, and that which distinguishes their special place among musical instruments. Of music, in the artistic sense of the word, bells in their true form are hardly capable. They may be tuned to a regular scale, and sounded in various successions, but the method of obtaining the sound by swinging the bell till the clapper hits it (by which method alone the full sound can be elicited) necessarily precludes anything like the exactitude in time or the variation in intensity by which form and expression are given to music. All the contrivances for performing music on bells with mechanical precision involve a greater or less departure from the true principle of the bell, and an impairing of its characteristic sound by fixing it instead of letting it swing freely. It will be seen, therefore, that bells form a kind of connecting link between the music of art and the music of nature; their fixed tone and synchronous vibrations connecting them with the art, while the irregular and formless character of the music produced from them even by the best peal-ringers, partakes of the wildness and vague character of natural sounds. It is this wildness of character which is one of the great charms of bell-music on a large scale, and which has caused it to be so much interwoven with the associations of men, both in real life and in imaginative literature.
Like the harp, the bell is prse-historic in its origin; nor would it serve much purpose here to speculate upon the probable origin, or earliest form of the bell, of which in fact we know nothing; or even to dwell on the very uncertain archæology of the instrument. The records of almost all nations of whose early history we know anything imply the use of bells in one shape or another; generally, it would seem, as a sign or proclamation, just as the railway bell, the church bell, and 'that tocsin of the soul, the dinner-bell,' are still used. But there can be no question that the real development of bells and bell-ringing into their highest form is due to the art and the ecclesiastical fervour combined of the middle ages. The influences which led to the development of bell-ringing and bell-founding were not dissimilar to those which led to the great development of architecture in the cathedral form. Not that either architecture or bells were necessarily connected with ecclesiastical predominance; but that the church being the great power and central influence of mediæval