184 Transactions of the American Institute. 



The earth is indeed a powerful magnet. Then why not use the 

 electric current we have evolved from it ? Let us put it in har- 

 ness and make it work for us. But to swing this coil is laborious, 

 and to facilitate this I will strap it on this large wooden ring, and now 

 we literally have it in harness. Let not this simple mechanical inter- 

 vention between the coil and the galvanometer perplex you ; in fact, 

 it is only here to enable me to give a continuous revolution to the 

 coil, and, by means of this brass circle, and these metal bands to 

 which its ends are connected, to cause the current evolved in it always 

 to issue from the same end of the coil. This current of electricity, 

 continuously evolved, can do many things ; it can give out heat and 

 light, and rend the elements of matter asunder ; but the grandest 

 application of electricity is to convey thought ; and why not convert 

 our apparatus into a telegraph % Here, in this ring, is the generator, 

 which produces an electric current directly from the earth's magnet- 

 ism. Here is the wire leading to the distant galvanometer. Here I 

 separate the wire and reconnect through a telegraph key, and behold 

 " a needle telegraph." This wheel is now turned, and look ! the 

 needle goes from 0° up to 90°, and now it stands steady at 80°. "We 

 can easily make an alphabet. Let one deflection to the left mean A ; 

 two, B ; three, C ; one to the right, followed by one to the left, D ; 

 one to the left, then one to the right, followed by one to the left, E ; 

 and so on. Thus we can form a series of signals that will spell out 

 whatever we desire, and the galvanometer can speak for us through the 

 deflection of the needle produced by the magnetic-electric currents of 

 the south. Now I will bring the needle to from 0° to the left ; it is 

 coming to 0°, and now I hold it there by rotating the coil, and thus 

 opposing its motion. I now deflect it, one to the right, then one to 

 the left, and so on. You see we have actually telegraphed with a cur- 

 rent from electricity, and evolved from this great magnet, the earth. 



Now we have finished our experiments, and what have they shown ? 

 I have temporarily magnetized a bar of soft iron, by pointing it 

 toward a pole of our large magnet. I did the same with the bar and 

 the earth. I permanently magnetized an iron bar by directing its 

 length toward the pole of the magnet, and vibrating it with a blow 

 of a hammer. I did the same with a bar, struck when pointed toward 

 the earth's magnetic pole. I have shown you the action of a small 

 magnetic disc on iron filings placed above and around it. You saw 

 that the earth produced the same action on the beams of the aurora. 

 I showed you the action of this disc on a freely suspended magnetic 

 needle ; and pointed out to you the earth's similar action on a dip- 



