232 SCIENTIFIC RECREATIONS. 



The poles of the magnet display the same phenomena as regards 

 attraction and repulsion, as do the opposite kinds of electricity. If we 

 suspend a magnet and bring the north pole of another to the north pole of 

 the suspended magnet, the latter will turn away; but if we apply the north 

 pole of one to the south pole of the other they will be attracted just as 

 opposite electricities attract each other. 



MAGNETIZATION is the term applied to the making of artificial 

 magnets, which act is accomplished by bringing the needle in contact 

 with other magnets, or sometimes by means of the electric current. If we 

 carefully stroke the needle with the magnet, always in the same direction, 

 lifting the magnet and beginning afresh every time, we shall magnetize the 

 needle, but with a different polarity from the pole it was rubbed with. A 

 magnet rubbing its north pole against a needle will make the latter's point 

 soutJi, and vice versa. 



Now that we have seen how the '* magnetic needle " is arrived at, we 

 can proceed to explain the electric telegraph. The term telegraph is derived 

 from the Greek words tele* " far," and graphein, " to write," and now includes all 

 modes of signalling. Signalling, or telegraphing, is of very ancient origin ; 

 the Roman generals spelt words by fire. The beacons fired on the hills, the 

 " Fiery Cross," and other ancient modes are well known. The semaphore 

 and flags have long been and are still used as modes of signalling, while the 

 flashing of the heliograph " telegraphs " to a distant camp. 



The Semaphore was invented by Chappe, and was really the first 

 practical system of telegraphy. It was adopted in 1794, but before this, in 

 1753, a letter appeared in the Scots Magazine, by Charles Marshall, sug- 

 gesting that signals should be given by means of electric wires, equal in 

 number to the letters of the alphabet. Soon afterwards Lesage, of Geneva, 

 made an electric telegraph to be worked by frictional electricity, and many 

 ingenious attempts were subsequently made to utilize electricity for signalling 

 purposes, but without any permanent success ; indeed, the British govern- 

 ment were quite content with their semaphores, for they wrote that " tele- 

 graphs of any kind are now wholly unnecessary, and no other than the one 

 now in use will be adopted " ! 



The Electric Telegraph has had considerable antiquity claimed for it, 

 but it is pretty certain that the discovery made by Doctor Watson, in 1747, 

 that electricity would pass through wires, and that the earth would complete 

 the circuit, gave the first impetus to the Electric Telegraph. Doctor Watson 

 was enabled to transmit shocks across the Thames, and made experiments at 

 Shooters Hill. Franklin did likewise across the Schuykill in 1748, and 

 De Luc performed the same experiments on the Lake of Geneva. Both 

 Lesage and Lomond caused pith balls to diverge at distant points, and in 

 1794 Reizen made use of the electric spark for transmitting signals, and 

 made strips of foil show out certain letters when the spark passed. He had 

 a wire and a return wire for each letter of the alphabet. 



These were all slow advances, and subsequently many learned men in 



