The vibrations of a column of air in a pipe may be regarded as obeying the same general laws: notes are naturally higher in proportion to the shortness of the pipes. The air-waves impelled through the Pandean pipes, the pipes of an organ, a flute, a clarionet, or a trumpet, impart corresponding vibrations to the sounding material, and hence the difference in the tones and intensity of different instruments. That musical notes are thus produced in solid masses is proved by placing a bar of metal, which has been heated, to cool, with one end supported upon a wedge-shaped piece of metal, of another kind, as in Fig. 132;-a piece of iron, for example, upon a piece of lead. Mu

sical sounds, si

milar to the

tremulous notes

of an Eolian

Fig. 132.

harp, are produced under these conditions, and they will be found to vary under almost every change of the circumstances. These tones are due to the molecular disturbance producing very rapid pulsations, in a regular series, along the bar.

Musical notes may also be produced by placing a long bar of metal within a helix of copper wire, resting its extremities upon some fine edge of a non-sonorous body, and then, by connecting the wire with a galvanic battery, producing an electrical disturbance along the wire :-every time connection is made or broken, a distinct musical

note is distinctly heard. The chemical harmonicon is an interesting exemplification of another of these wave phenomena. The best mode of safely trying the experiment is as follows:—Take a large bottle, and fit into the cork of it a tube which has a very fine orifice. Place some granulated zinc in the bottle, and pour upon the metal some very diluted sulphuric acid, and insert the cork. Hydrogen gas is thus formed, which will issue from the jet with some degree of force. Allow the gas to escape for a few minutes, that the atmospheric air which was in the bottle may be got rid of, and then ignite the jet of gas issuing out, which will burn with a small blue flame, giving but little light. If over this flame a glass tube is held, and gradually moved up and down, a very clear note is produced, the pitch of the note varying with the thickness of the glass in the tube, its length, and many other The musical notes are produced in this instance by a rapid succession of small explosions, as the hydrogen gas mixes with common air in the tube.

causes.

The organs of speech present to us an exceedingly beautiful contrivance, adapted for the production of every variety of sound. They consist of the windpipe, a tube extending from one extremity of the throat to the other ending in the lungs, through which the air passes to and from these organs of respiration; the larynx, formed of four cartilages, the cricoid, the thyroid, and two arytenoidthese are moved and varied by means of different sets of muscles; the glottis, formed principally by the chorda vocales,

which are merely a very elastic tissue; and the ventriculi Morgagni, which form a sort of second glottis. The following figures show the formation of the larynx :—the

VVA

Fig. 133.

first represents an anterior, the second a lateral, the third a posterior, and the fourth a superior view of this organ. The formation of notes in the larynx is pre

cisely similar to that of reed-pipes, as may be illustrated by the following arrangement :Take a piece of sheet India-rubber, and fold it around a glass cylinder, as in Fig. 134; then, by warming the two edges, they may be easily Fig. 134. united, and form an external cylinder of caoutchouc. This represents the mouth and by blowing into the

:

glass cylinder, and stretching out the Indiarubber, so as to imitate the action of the lips, a great variety of tones may be produced.

A curious pipe is employed in the Organ to imitate the human voice (Fig. 135). It is composed of a very short conical tube, the base upwards surmounted by a short cylinder, and the pitch is regulated entirely by the reed. There is a circular operculum which half closes the open Fig. 135.

end of the cylinder, to imitate the lips; the reed performing the part of the larynx, and the pipe itself of the cavity of the throat and mouth.

Fig. 136 represents the so-called chimney-pipes

Fig. 136.

of the same instrument, which are closed at the upper end by covers, through the centre of which passes a pipe of small diameter, as a continuation to the lower one; these produce sounds intermediate between the tones of

open and stopped pipes. The construction of

them is given, as showing a very

simple form of pipe by which, with the one previously drawn, a great variety of interesting experiments may be made.

Such are the principal phenomena which belong to the interesting subject of sonorous wave-vibration.

་

ELECTRICITY,-from nλeктpov, electron, amber ;- Thales of Miletus having first observed a peculiar attractive and repulsive power in that substance, which was eventually proved to be due to a subtile principle, supposed to pervade all nature, and which certainly is one of the most important of the great physical agents.

Some of the peculiar phenomena of electricity are very easily rendered evident :-Take a stick of sealing-wax, and after having rubbed it freely upon a coat-sleeve, or with a piece of woollen or silk, pass it an inch or two above small fragments of paper or metal leaf, when they will be forcibly attracted, and cling to it.

Or, take a sheet of ordinary writing-paper, and having dried it by the fire, place it upon a dry painted table