The aeolian harp is a musical instrument which is set in action by the wind. The instrument, which is not very well known, is yet very curious, and at the request of some of our readers we shall herewith give a description of it.
FIG. 1. - KIRCHER'S aeOLIAN HARP.
According to a generally credited opinion, it is to Father Kircher, who devised so many ingenious machines in the seventeenth century, that we owe the first systematically constructed model of an aeolian harp. We must add, however, that the fact of the spontaneous resonance of certain musical instruments when exposed to a current of air had struck the observers of nature in times of remotest antiquity.
Without dwelling upon the history of the aeolian harp, we may say that in modern times this instrument has been especially constructed in England, Scotland, Germany, and Alsace. The aeolian harp of the Castle of Baden Baden, and those of the four turrets of Strassburg Cathedral are celebrated.
FIG. 2. - FROST & KASTNER'S IMPROVED aeOLIAN HARP.
We shall first describe Kircher's harp, which this Jesuit savant constructed according to an observation made by Porta in 1558. The instrument consists of a rectangular box (Fig. 1), the sounding board of which, containing rose-shaped apertures, is provided with a certain number of strings stretched over two bridges and fastened to pegs at the extremities. This box carries a ring that serves for suspending it. Kircher recommends that the box be made of very sonorous fir wood, like that employed in the construction of stringed instruments. He would have it 1.085 meters in length, 0.434 meter in width, and 0.217 meter in height, and would provide it with fifteen catgut strings, tuned, not like those of other instruments to the third, fourth, or fifth, but all in unison or to the octave, in order, says he, that its sound shall be very harmonious. The experiments of Kircher showed him the necessity of employing a sort of concentrator in order to increase the force of the wind, and to obtain all the advantage possible from the current of air that was directed against the strings. The place where the instrument is located should not, according to him, be exposed to the open air, but must be a closed one. The air, nevertheless, must have free access to it on both sides of the harp.
The force of the wind may be concentrated upon such a point in different ways; either, for example, by means of conical channels, or spiral ones like those used for causing sounds to reach the interior of a house from a more elevated place, or by means of a sort of doors. These latter, two in number, are adapted to a kind of receptacle made of boards and presenting the appearance of a small closet. In the back part of this receptacle there is a slit, and in front of this the harp is hung in a slightly oblique position. The whole posterior portion of the apparatus must be situated in the apartment, while the doors must remain outside the window (Fig. I). In later times the aeolian harp has been improved by Messrs. Frost and Kastner, whose apparatus is represented in Fig. 2. It consists of a rectangular box with two sounding boards, each provided with eight catgut strings. In order to limit the current of air and to bring it with more force against the strings, two wings are adapted near the thin surfaces opposed to the wind, so that the current may reach each group of cords on passing through the narrow aperture between the obliquely inclined wing and the body of the instrument.
The dimensions of the resonant box are as follows: height, 1.28 meters; width, 0.27 meter; and thickness, 0.075 meter. Distance between the two bridges, or length of the sonorous portion of the cords, about 1 meter; width of the wings, 0.14 meter. Distance between the sounding board and the wings, 0.42 meter. Inclination of the wings, 50 degrees.
FIG. 3. - aeOLIAN HARP IN THE OLD CASTLE OF BADEN BADEN.
The celebrated aeolian harps of the old castle of Baden Baden are entirely different, and merit description. One of them (Fig. 3) is formed of a resonant box, the construction of which differs from that of aeolian harps with a rectangular box, in that it is prolonged beyond the place occupied by the strings, and is rounded off behind. In the opposite side there are two long and narrow apertures. To prevent the apparatus from being injured by the weather, it is inclosed in a sort of case occupying the recess of the window in the old ruined castle in which it is exposed. Behind the harp there is a wire lattice door, the purpose of which seems to be to protect the instrument against the attempts of robbers or the indiscreet contact of tourists. We annex to the general view of the instrument a front and profile plan (Fig. 4). The aeolian harp has often inspired both writers of prose and poetry. Chateaubriand, in Les Natchez, compares its sounds to the magic concerts that the celestial vaults resound.
Without attributing such effects to the instrument, it must be admitted that it possesses remarkable properties, which act upon the nervous system and cause very different impressions, according to the temperament of those who listen to its accords.
FIG. 4. - PLAN OF THE BADEN BADEN INSTRUMENT.
Hector Berlioz, in his Voyage Musicale en Italie, has given as follows the curious effects that an aeolian harp produced upon his lively and impassioned imagination: "On one of those gloomy days that sadden the end of the year, listen, while reading Ossian, to the fantastic harmony of an aeolian harp swinging at the top of a tree deprived of verdure, and I defy you not to experience a profound feeling of sadness and of abandon, and a vague and infinite desire for another existence."
An English physician, Dr. J.M. Cox, in his practical Observations upon dementia, asserts that unfortunate lunatics have been seen whose sensitiveness was such that ordinary means of cure had to be given up with them, but who were instantly calmed by the sweet and varied accords of an aeolian harp. Other observers narrate that they have heard the efficacy of Aeolian sounds spoken of in Scotland for producing sleep.
Telegraph wires are often, under the influence of the winds, submitted to vibrations which reproduce the phenomena of the Aeolian harp. The electric telegraph, which, before the construction of the Kehl bridge, directly traversed the Rhine, very frequently resounded, and the observer who placed his ear against the poles on the bank of the river was enabled to hear something like a far-off sound of bells. - La Nature.