The uses to which the electro-motograph may be applied are various. It can produce mechanical motion even at a distance, and is useful to lessen friction by machinery; and in this way its service to railways and other locomotive systems may be estimated. It is a great help to telegraphy by increasing the speed of transmission, and can ascertain the beatings of the heart of the apparently dead. It amplifies sound in a much greater degree than the microphone, by which even a fly can be heard moving. In fact, the limit of the usefulness of this wonderful machine has not been reached. Another very ingenious apparatus has been developed by Professor Bell. This is for the purpose of ascertaining the position of bullets in the body. The following is condensed from the _Times_:— “Two conductors are used, and the ball completes the circuit. Professor Bell inserts a fine needle in the suspected region. It is connected by wire with one of the binding screws of a telephone, which the surgeon holds to his ear; the other binding screw being connected with a metallic mass applied to the skin. When the needle point touches the ball, an electric couple is formed, and the current generates the sound in the telephone. The surgeon may then use his knife with confidence, guided by the needle. He may make several insertions of the needle if necessary without danger, and any pain may be obviated by etherization. This simple method (which should prove useful on the field of battle) was tried with success with a lead ball introduced into a piece of beef. Contact of the needle with bone had no effect, but a very distinct sound was heard each time the ball was reached. A modification consists in inserting a vibrator in the circuit; this gives a musical note in the telephone at each contact of ball and needle. Again, if the circuit include a battery, the telephone sounds may be heard by several persons at once. A sound is heard, in this case, whenever the needle enters the skin; but, on reaching the ball, it is much intensified, owing to lessened resistance. A galvanometer may be used in place of the telephone.”