The Gyroscope, an instrument now familiar to most scientific persons, is still a problem of which the solution has not yet been found. It may be called the paradox of mechanics, for although it depends on gravitation, it appears to be entirely indifferent to it.
An American scientist has applied electricity to the gyroscope, so as to make its movements as continuous as possible, and to enable us to study it more at leisure and with better results. The gyroscope is mounted on a pedestal which tapers to a point, and supports the instrument. The bar of the gyroscope on which the electro-magnets are fixed rests upon the top of the pedestal. One of the extremities of the bobbin is fixed to the cavity, when the bar and support join, the other extremity communicates with the bar which joins the nuts of the magnets.
An insulator of hardened caoutchouc is so placed that it just touches the axis of the wheel twice in every revolution of that wheel. Its plane of rotation is at right angles to the magnets, and carries an armature of soft iron which turns very close to the magnet without touching it. The armature is put en rapport with the surface of contact of the cylinder, so that when the armature approaches it is attracted; but immediately afterwards, as it reaches the opposite side, the current is interrupted, and the impulse acquired is sufficient to move the wheel to the spot where the armature can again come under the influence of the magnet.
The magnets, the wheel, and all the parts of the instrument together can move around in any direction. When two or four Bunsen cells are put in connection with the gyroscope, the wheel turns with tremendous rapidity, and by permitting the magnets to work (an operation which requires some little dexterity), the wheel not only sustains itself, but also the magnets and the other subjects which are between it and the extremity of the pedestal—in opposition to the laws of gravitation. The wheel, besides turning rapidly around its axis; revolves slowly around the point of the column in the same direction taken by the lower part of the wheel.
When attaching the arms and counter-poise of the machine, so that the wheel and the magnets may balance themselves exactly on the pointed pedestal, the machine remains stationary. But if we give any preponderance to the wheel and magnets the rotation of the apparatus is in a direction opposite to that which would result from turning the upper part of the wheel.
The gyroscope illustrates the persistence with which a body that submits to rotation maintains itself in the plane of its rotation, notwithstanding the force of gravitation. It also shows the result of the combined action of two forces tending to produce rotation around two separate axes, which are, however, situated in the same plane.
The rotation of the wheel round its axis is produced in the present case by the electro-magnet; and the tendency of the wheel to fall, or to turn in a vertical plane parallel to its axis, results in the rotation of the entire instrument upon a new axis, which coincides with the pointed pedestal.
The American Money-Box.
During a recent visit to London, as I was one day walking in the Crystal Palace, my attention was attracted by a curious money-box, surmounted by a pictorial representation of one of the London streets. The carriages, horses, and pedestrians were represented by figures cut out of cardboard, arranged in a groove. A large placard bore this inscription: “Notice to visitors: Throw a penny in the money-box; and the figures will perform.”