662 TEE POPULAR SCIENCE MONTHLY. 



graph is taking other directions. On the common lines the messages 

 are sent by the operator at the rate of about thirty or forty words a 

 minute. But inventions are in progress, and are now being introduced, 

 which will enable a thousand words a minute to be sent. Think of 

 sending messages from Boston to New York over one wire, and record- 

 ing them there, at the rate of a thousand words a minute ! Few peo- 

 ple speak at the rate of two hundred words a minute. 



Those of us who are in the habit of receiving messages, often get 

 them printed on long strips of paper. The invention used in sending 

 messages in that way is one which enables a man in New York, by 

 touching keys like those of a piano, to operate a printing-machine in 

 Boston or Chicago. 



The highest achievements in telegraphy are undoubtedly reached 

 in the ocean telegraph. It demanded a whole line of inventions pecul- 

 iar to itself. A simple wire could not be used for a conductor. It 

 would give out the electricity to the water so fast that none would 

 reach the farther end to deliver the message, and the wire itself would 

 be speedily destroyed. A coating must, therefore, be found for it 

 which would at once protect the wire from the action of the water 

 and keep the electricity from going off into the water. When such a 

 coating had been invented, it was found necessary to strengthen the 

 copper wire used for the conductor by the addition of steel wires, 

 which must not touch the co2:)per wire, but surround it, and this too 

 must be protected by a coating. Then machinery had to be invented 

 to combine the copper and steel wires with the coating material into 

 a cable. Other machinery had to be invented to deliver the cable 

 from a ship as she sailed over the course where the cable was to be 

 laid. Only the steamship could be used for the purpose, and thus the 

 invention of the steam-engine gave to man the power to establish ocean 

 telegraphs. New instruments of the most wonderful sensibility had 

 to be invented both for sending and receiving the messages. A minute 

 magnet carries a tiny mirror and is suspended by a thread so as to 

 yield to the slightest impulse. A ray of light from a lamp falls upon 

 this mirror and is reflected upon a screen some feet distant. This ray 

 of light is the finger which the operator watches upon the screen. As 

 the current in the wire varies under the action of the sending instru- 

 ment, the magnet turns one way or the other, and the spot of light on 

 the screen moves one way or the other and indicates the signals of the 

 Morse alphabet to the operator and enables him to spell out the words. 



Sometimes a fault is developed in the wire as it lies on the bottom 

 of the ocean, and signals can not be sent. Does it seem possible that 

 man can tell whereabout on three thousand miles of wire, two miles 

 under water, the fault is? He has invented instruments which en- 

 able him to do it, and to send a vessel to the very spot over the wire 

 where the fault is, pick up the wire and mend it, and return it to its 

 resting-place. 



