CHAMBERS'S INFORMATION FOR THE PEOPLE. 



was merely looked on as a scientific curiosity, till 

 1837, when no less than three practical systems 

 were independently tried. In June of that year, 

 Cooke and Wheatstone patented a five-needle 

 telegraph, which was soon after put in action on 

 the Great Western Railway. Their lines were 

 underground insulated wires, and were undoubt- 

 edly the first used for general purposes. Cooke 

 had seen in the lectures of Professor Muncke of 

 Heidelberg, one of Baron Schilling's horizontal 

 needle telegraphs, and had been struck by its 

 practical value. In July of 1837, Steinheil, at 

 Munich, established a system of wires, upwards 

 of seven miles in length, stretching them over the 

 houses of the town. He was thus the first to 

 have an air-line. He also first made use of the 

 earth as ' a return wire.' He had three ways of 

 telegraphing by the deflections of a needle, by 

 the sounding of two bells, and by printing on a 

 strip of paper dots to right and left with positive 

 and negative currents. In October of the same 

 year, Professor Morse of New York exhibited his 

 printing instrument, which we have already de- 

 scribed ; but it did not come into practical use till 

 1844. During these years also appeared new 

 forms of galvanic battery, DanielPs in 1837, 

 Grove's in 1839, and Bunsen's in 1843, the im- 

 portance of the telegraph having given a stimulus 

 to the study of galvanic action. Faraday, in 1 840, 

 by a series of testing experiments, seemed to 

 establish the chemical theory of the galvanic 

 current ; yet thirty years later, and the balance 

 of opinion has apparently turned in favour of 

 the contact theory, which Sir W. Thomson may 

 be said to have put beyond dispute. The first 

 successful submarine cable was laid in 1851 



between Dover and Calais. In 1858, the first 

 Atlantic cable was completed ; but it and a 

 second laid in 1865 were not fortunate; that of 

 1866 was, however, permanently successful. Now 

 there are not a few Atlantic cables, English, 

 American, or French ; and there is telegraphic 

 communication (partly submarine) between Europe 

 and India, China, Australia, and the Cape of 

 Good Hope, as there is between Chili and the 

 United States. The perfection of the telephone 

 about 1876, by which sounds, articulate or other, 

 are communicated at a distance by electricity, 

 marked a new application of electric science. 

 The gradual development of magneto-electric or 

 dynamo-machines and electro-magnetic apparatus 

 led in 1881 to an electric tramway at Berlin, 

 followed by one at Portrush in Ireland. Electric 

 boats have also been successfully used ; and 

 amongst most recent developments, tricycles 

 lighted and propelled by special tricycle electro- 

 motors have to be mentioned. 



With regard to the modern development of 

 electrical science generally, it is remarkable that 

 it should have taken an almost identical shape 

 both in frictional and in current electricity. The 

 machines of Holtz and Tcepler alongside of those 

 of Wilde and Ladd, shew that induction supplies 

 the link between mechanical force and electric 

 energy of whatever form. Of modern contribu- 

 tions to electricity, we cannot here attempt an 

 outline. They are associated with a host of 

 illustrious names, such as Becquerel, De la Rive, 

 Jacobi, Ohm, Harris, Du Moncel, Ruhmkorff, 

 Wheatstone, Berlin, Siemens, Joule, Jenkin, 

 Varley, Edison, Graham Bell, and Sir William 

 Thomson. 



45- Cooke and Wheatstone's Single Needle Instrument. 



