From which it appears that Canada collects over a half more duties from British goods than she does from American goods, while the total value of her imports from the United States is over six millions greater than that of her British imports.
TELEPHONING.
Aledo, Ill.
How is the telephone operated in the city of Chicago? Give an illustration of how messages are conveyed by telephone. Is electricity used on all telephone instruments? Does each person having an instrument have a separate wire at the central office?
S. Grady.
Answer.—In telegraphy the wire between stations is a magnet only so long as the electrical current is passing over it, which is the case so long as the wire is connected with the battery. This connection is made or broken by means of a small lever under the finger of the operator at the transmitting station, known as the transmitting key. While the current is on and the wire is a magnet it attracts to itself a piece of soft iron at the receiving station, known in the Morse writing telegraph as the recording style. The instant the connection between the battery and the wire is broken the latter ceases to be a magnet, and the soft iron at the receiving station springs back to its old place. By this means every movement of the transmitting key is instantly repeated at the receiving station. In the telephone two thin metallic plates or diaphragms are substituted for the key and the soft iron recording style. The undulations of the air produced by the voice of the speaker cause the thin plate in the transmitting instrument to vibrate more or less violently, in harmony with the voice. This plate is so connected with the wires running between the battery and the receiving station that the electrical current over the circuit is entirely closed or broken, or varied in intensity, according to the degree of vibration, while the receiving plate, at the other end of the wire, vibrates in unison with the transmitting plate, reproducing undulations in the air at that end of the wire directly corresponding with the undulations made by the voice of the speaker—that is, reproducing the sounds of his voice. Electricity is used in all telephones of any practical value. In Chicago the main wires and the branches from the down-town offices center at a common office, known as the central station, where, by means of couplings made by the movement of certain keys, separate wires are instantly joined or disconnected. Any one wishing to communicate by telephone turns a small crank, which rings a bell at the central office. The operator at the latter place responds by signal. The person who wishes to communicate generally inquires, “Is this the central office?” Having received an affirmative reply, he requests to be put into communication with the number in the telephone register corresponding to the office or residence of the person with whom he wishes to speak. He may now sit down until signaled that some one at the place called for is ready to communicate with him, or the operator at the central office notifies him that he can get no response from the number called for. Besides the main central office there is a district center in each of the principal divisions of the city, North, West, and South, all under the control of the former. It is not necessary for a separate wire to run from each instrument in the city directly to one of these centers. Several individual wires may unite with one common wire before reaching either the central office or a district center.
THE ALHAMBRA—MUNICH.
Marengo, Ill.