MAGNETIC TELEGRAPH. 37 



variometer; and was the germ of the electro-mag- 

 net. For four years this beautiful discovery was 

 experimented with by all the scientists in Europe 

 before another step was taken; and then William 

 Sturgeon, of England, produced the electro-magnet. 

 It consisted of a large soft iron wire, bent into 

 a horse-shoe form, coated with varnish, and 

 wrapped with a spiral coil of naked copper wire 

 from end to end, through which the voltaic cur- 

 rent might be passed. This bent wire became a 

 magnet while the current flowed, but lost its mag- 

 netism when the current ceased. 



Here then was born into the world an apparatus 

 capable of exerting a stronger power at the will of 

 the operator, by merely opening and closing the 

 voltaic circuit; and it was then thought that the 

 difficulties in the way of the telegraph were con- 

 quered. The experiment was soon tried with 

 Sturgeon's magnet by Barlow, an eminent scien- 

 tist ; and in January, 1825, he published his results 

 in the "Edinburgh Philosophical Journal" in 

 these words: 



" The details of this contrivance" (a telegraph) 

 " are so obvious, and the principle on which it is 

 " founded so well understood, that there was only 

 " one question which could render the result 

 " doubtful; and this was, is there any diminu- 

 " tion of effect by lengthening the conducting 



