20 THE SCIENTIFIC PAPERS OF 



whether the rails might not be used as metallic conductors, he re- 

 discovered the conducting power of the earth itself, which, it 

 appears, had been lost sight of since it had first been discovered 

 by Franklin with regard to static electricity, and proved also with 

 regard to voltaic electricity, in 1803, by Erman, Basse, and 

 Aldini. 



The first recording instrument, and the telegraphic earth circuit, 

 are discoveries which entitle Steinheil to a high position among 

 the originators of the electric telegraph, although the means he 

 proposed for its execution were too refined for the time, and did 

 not lead on that account to immediate practical results. 



At the time when Steinheil was absorbed in his labour, Professor 

 Wheatstone was also engaged upon a series of experiments on the 

 velocity of electricity, with a view to the construction of electric 

 telegraphs, and in June, 1837, he joined Mr. Cooke in a patent 

 for a needle telegraph of five line wires (besides one wire for the 

 return current), and as many needles, which, by an ingenious 

 system of permutations, could be so deflected that any letter of 

 the alphabet was pointed out upon a diamond-shaped board by the 

 convergence of two needles towards it. The line wires were 

 proposed to be coated with insulating material, such as fibrous, 

 substances saturated with pitch, and to be drawn into leaden pipes,, 

 in order to exclude the moisture of the ground into which they 

 were intended to be laid. An experimental line of telegraph on 

 this principle was established in the same year at the Euston 

 Railway Station, and the results obtained left, it appears from 

 documentary evidence, no doubt upon the mind of the then resi- 

 dent engineer of the London and Birmingham Company, the 

 present Sir Charles Fox, of its ultimate success. That success,, 

 however, was not obtained without a struggle against practical 

 difficulties, in the course of which the system underwent important 

 modifications, of which the double needle instrument, such as is 

 still used extensively in this country, and (in 1843) a return to> 

 overground line wires, were the results. 



To Cooke and Wheatstone is due the credit of having estab- 

 lished the first commercially useful lines of electric telegraph, 

 namely, the lines between Paddington and Dray ton, commenced 

 in 1838, and between London and Blackwall, commenced in 

 December, 1839, which were soon followed by others. 



