3S6 NINETEENTH CENTURY. 





atmosphere at that moment set up such strong electric cur- 

 rents in the wires of the telegraphs all over the world, that the 

 signalmen at Washington and Philadelphia received severe 

 electric shocks; a telegraphic apparatus in Norway was set 

 on fire, and a stream of electric light followed the pen of 

 Bain's electric telegraph, which writes down the message on 

 chemically prepared paper. Moreover, beautiful auroras 

 were seen in both hemispheres, and these brilliant lights are 

 believed to be caused by magnetic currents. The magnetic 

 storms on this occasion lasted for several days, and there 

 could no longer be any doubt that the sun at a distance of 

 nearly 92,000,000 miles can produce a complete hurricane 

 of magnetic disturbance on our earth. This connection of 

 the storms with the sun-spots seems indeed, as I have said, 

 P- 353> to suggest that the sun must have the power of pro- 

 ducing magnetic currents in some more direct way than 

 merely through the action of electric currents set up by the 

 varying heat on different parts of the earth. 



Invention of the Electric Telegraph by Wheatstone and 

 Cooke, 1837. — We have spoken in the last paragraph of the 

 electric telegraph, and though this is more strictly an inven- 

 tion than a step in science, yet we can hardly close an 

 account of electricity and magnetism without showing how 

 the discovery of these two forces has made it possible for 

 our thoughts to be carried in a few moments of time across 

 land and sea to the most distant parts of the world. 



Ever since Volta showed, in 1800, that an electric current 

 can be sent for any distance along a wire the two ends of 

 which are joined to the poles of a battery, scientific men had 

 speculated whether it might not be possible to use this 

 current for making signals at a distance. But there was 

 always the difficulty of how to make the signs at the other 



