TRANSACTIONS OF THE SECTIONS. 19 
On an Acoustic Telegraph. By W. Lavo. 
This instrument consists essentially of two distinct pieces of apparatus. That 
for transmitting the signal has a small mouth-piece. On the right-hand side there 
is a finger-key, forming part of the circuit, and an electro-magnet, with a vibrating 
armature and binding-screw to connect with one of the line wires. Within a case, 
under a glass cover, is an elastic membrane, in the centre of which is fixed a 
platinum plate in connexion with the finger-key. A light piece of angular metal, 
resting on three pins, is so placed that the pin at the angle rests on the plate in the 
centre of the membrane, the other two resting in cups on its edge, so as to allow of 
free motion on the points. In the body of the receiver-box is suspended a soft 
iron core, surrounded by a coil of silk-coyered wire, one end of which is in con- 
nexion with the finger-key and the other with the binding-screw. The method of 
producing sound in the receiving instrument depends upon the fact that, at the 
moment of magnetizing or demagnetizing a piece of iron, there is an alteration in 
the arrangement of the particles, which gives rise to a slight ticking noise. 
Having connected the transmitter, by means of an insulated wire, with the re- 
ceiver, and the binding-screws having been brought in connexion with a battery of 
three or four elements, if the finger-key on the transmitter be pressed, the person 
at the receiying-station hears the ticking noise. To convey a musical note or 
sound, the operator places his mouth to the tube in front of the instrument and 
sings a note, when immediately the membrane begins vibrating in accordance with 
the note sounded, and at each vibration breaks contact between the pin and plate 
in its centre. This, forming part of the circuit, causes the iron core in the receiy- 
ing instrument to be magnetized and demagnetized a number of times equal to the 
number of vibrations of the membrane, and so conveys to the receiver an impres- 
sion of a musical sound, The finger-keys and small magnet at the sides of the 
instruments are for the purpose of varying the methods of communication by the 
combination of single sounds, and can also be used with the other parts for the 
purpose of regulating the lengths of the notes and dividing them imto varying 
pomans, so as to form a sound-alphabet somewhat similar to the signals written 
y Morse’s telegraph. 
An Electromotive Engine, exhibited and described by W. Lavo. 
The electromotive machine exhibited and described by the author consisted of 
two coils forming a powerful electro-magnet, revolving on an axis parallel to the 
axes of these coils, and at equal distances between them. On the stand four 
pillars, forming coils, were planted in the circumference of a circle round the re- 
volving electro-magnet, aed at such a distance from it as just to permit its free 
motion. By asimple contrivance, similar to the commutator, the electric current 
was so transmitted and reversed as to make each of the pillar-coils a magnet, with 
the pole it presented to that of the revolving coil as it approached it, of the oppo- 
site name, south or north; but the instant it passed, reversing it into one of the 
same name: thus, while advancing it is attracted; but the instant it begins to 
retire, repelled ; and so a constant motive force is applied to keep it revolving. 
The engine exhibited was mounted with bevel wheels, carrying an axle, on which 
a cord could wind up a weight of some pounds. It was also furnished with a 
friction-break, by which its power (which was, even with only two Grove’s cells, 
considerable) could be exactly measured. 
On Galvanic Copper and its Applications. By M. Ovpry. 
Communicated by the Abbé Moreno. 
M. Oudry, haying been commanded by the Emperor to endeavour to protect some 
of the public monuments of France and chefs-d’ ceuvre of art by the electro-plating 
process, found insurmountable difficulties in depositing 4 uniform and brilliant coat 
of copper on iron, either malleable or cast; but having succeeded by mechanical 
means in reducing electrotype plates of copper to a completely impalpable powder, 
he used this as a paint, with a medium the basis of which was benzoin instead of 
linseed oil or any of the oils used with ordinary paints. He had completely suc- 
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