CHAP. HI.] ELECTRIC TELEGRAPHY. 543 



CHAPTER III. 



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ELECTRIC TELEGRAPHY. 



I. INVENTION OF ELECTRIC TELEGRAPHY. 



TELEGRAPHY, or the art of communication at a distance, so as to 

 transmit orders, news, or instructions in a detailed and precise manner, 

 is quite a modern invention, a contemporaneous art, as we may say. 

 We have shown in the chapter devoted to telegraphy, what are 

 the elementary means of communication which all nations have used 

 from time immemorial in order to correspond rapidly at great distances : 

 bonfires, speaking-trumpets, the human voice transmitted from watch- 

 man to watchman, firing of cannon, maritime signals consisting of 

 combinations of visible objects, all these methods depend on the rapid, 

 almost instantaneous, propagation, of two physical agents, one, however, 

 much slower than the other, namely, sound and light. 



But it was not till the close of last century that any attempt was 

 made to bring telegraphy to sufficient perfection to be used in the 

 transmission of government despatches, and to insure the secrecy of 

 these despatches, while giving them the same degree of precision as 

 the language itself. Chappe's air telegraphs were adopted in 1793 by 

 the National Convention in France, and soon after spread into civilized 

 countries. But before even these were conceived, attempts had been 

 made in an entirely different direction ; a new science, electricity, had 

 revealed the existence of an agent which is propagated with a velocity 

 comparable with that of light, and the idea of making use of pheno- 

 mena of this kind for rapid communication was spreading on all sides. 

 Fifty years had scarcely passed before the electric telegraph had been 

 invented and had dethroned the air telegraph. 



