March 1 8, 1875] 



NA TURE 



391 



current; Faraday in 1831, who discovered the electric 

 current induced in a hollow coil of wire when a steel per- 

 manent magnet or an electro-magnet is introduced or 



PcpuIsioBS. AtlraclioDS. 



Fig. 4. — Law of the attraction and repulsion of a current by a current. 



withdrawn from the coil ; and Wheatstone, who in 1843 

 proposed to register observations of astronomical instru- 

 ments with a view to determine 

 longitude, and who shortly after- 

 wards published, in the Pliilo- 

 sophical Transactions, his in- 

 vestigations into the laws that 

 regulate the transmission of 

 electric currents through me- 

 tallic conductors — were not 

 then developed into any prac- 

 tical form ; it was only about 

 that time that public attention 

 became directed to the pro- 

 bable future of the electric tele- 

 graph. The exhibition instru- 

 ments open to the public at 

 one shilling each, between 

 Paddington and Slough, were 

 the means of bringing to justice 

 the perpetrator of a foul crime. 

 These early double-needle instruments, long since obsolete 



Fig. 6 —The Cocli and Wheatstone double-needle Telegraph ; 1845. 



as regards construction, have been preserved as indicating 

 he first era in telegraphic communication. 



In those days electrical knowledge was in its infancy : 

 the very wire between Paddington and Slough was insu- 

 lated partly by silk and suspended through goose-quills 

 attached to the posts along the Great Western Railway. 

 In those days of electrical innocence the practical value 

 of the return-circuit by means of the earth was un- 

 developed. As early as 1840 Wheatstone first con- 

 ceived the idea and published his plans for trans- 

 mitting messages under the sea by means of a sub- 

 marine cable. That scientific men at that time considered 

 that such a discovery would lead to most important 

 results is testified to by the Abbe Moigno, who writes that 

 it was announced by Wheatstone in 1S40 that he had 

 found the means of transmitting signals between Eng- 

 land and France, notwithstanding the obstacles of the 

 sea ; and he emphatically adds : " 1 have touched with 

 my hands the conducting wire . 



which, buried in the depths of 1 



the ocean, will unite instan- 

 taneously the shores of Eng- 

 land with the shores of France." 

 In 1844, at Swansea Bay, off 

 the Mumbles Lighthouse, the 

 first practical experiment took 

 place, and signals were trans- 

 mitted from an open boat to 

 the shore from a considerable 

 distance. In the boat sat the 

 inventor, Wheatstone, his eyes 

 eagerly watching his galvanometer for the coveted signals 

 — signals that would tell him his hopes were realised, and 



jf_ 



Fig. 7. — System of two magnetic 

 needles, with their poles reversed , 

 forming: an astatic combination, 

 neutrahsingthe effects of terres- 

 trial magnetism. 





that he had triumphed over the elements. The last twenty- 

 eight years have given birth to many wonderful and 

 practical results. Between 1S44 and 1848 railways were 

 in their infancy ; their limit of distance as compared 

 with their present extent was very circumscribed. Equally 

 so was electrical knowledge, as compared with the 

 requirements of extended distance. In 1848 Holmes gave 

 to telegraphy the practical result of his researches as 

 regards the rapid transmission of signals over extended 

 circuits. In those early days the five-inch astatic needles 

 and coils of the Cook and Wheatstone system were abso- 

 lutely useless for longer distances than one hundred miles, 

 and as railways extended, so telegraphic difficulties were 



