240 PROGRESS OF SCIENCE. 



battery), Jacobi, in 1830, established in Russia, between the 

 Emperor's palace and his minister Klamachi's office, the 

 EARLIEST ELECTRIC TELEGRAPH, but for a short distance 

 on ly a feat also ascribed to Baron Schiling, of Kanstadt, 

 who seems to have tried to utilise Oersted's discovery. Gauss 

 and Weber, in 1834, constructed a telegraph which com- 

 municated signals to the distance of one mile and a quarter. 

 Steinheil made a similar attempt in 1837. In 1832, Jacobi con- 

 structed another line twenty-one miles long between the 

 Winter Palace and the Summer Palace of Tsarskoie Selo, the 

 wires running through glass tubes. All these, however, were 

 abortive attempts for practical purposes ; but the names of 

 these precursors of Wheatstone should be nevertheless re- 

 membered and preserved from oblivion. 



1802 1876. Wheatstone made a RINGING APPARATUS 

 for electric telegraphy, the current of which was produced by 

 a constant battery ; then he devised RELAYS which ensured 

 the transmission to any distance an invention which made 

 THE ELECTRIC TELEGRAPH practically WORKABLE at last, 



-and made it one of the scientific marvels of our epoch (1837). 

 Soon afterwards several kinds of telegraphs were invented : 

 one by Steinheil in Germany, another by Morse in America ; 

 the latter being much used because the needle pricks holes 

 in a paper strip, and the strips of paper with the messages 

 they convey can be kept. The electrochemical telegraph, 

 invented by Bain, prints the marks on chemical paper ; the 

 telegraphic writing machine, invented by Cowper (1879), 

 actually reproduces the handwriting. Wheatstone, com- 

 pleting Steinheil's discovery, detected that the earth, besides 

 being an excellent conductor, actually intensifies electric 

 currents. He also invented the STEREOSCOPE, as well as a 

 photometer ; also the RHEOSTAT, by which the resistance of 

 any given electrical circuit can be increased or decreased 

 without opening the circuit ; invented the balance or bridge 

 which bears his name, to determine the electrical conductivity 

 of bodies; measured the VELOCITY OF ELECTRICITY, and 

 found it to be 288,000 miles per second, which is about 

 100,000 miles swifter than light. The speed through a con- 

 ductor is slower; Maxwell's determination reducing it to 



