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834 house in Berlin for the use of his plating apparatus, and Wilhelm was dispatched to England to introduce the inventions there. Besides the galvano-plating patent, which was sold to Elkington & Co. for £1,500, there were processes for nickel-plating and for anastatic printing, etc. A journey to London to assist Wilhelm in some financial difficulty, in which he visited Paris and Brussels on his return, gave him new and higher views of his work, while its results satisfied him that the road to wealth did not lie through speculation in inventions. He entered upon a more thorough course of study, formed associations with the young naturalists of the time, some of whom have since become famous, joined in the foundation of the Physical Society, interested himself in the Polytechnic Society, and sought to promote the technical applications of science. He became acquainted with manufacturers, and published articles in the scientific journals on "The Application of Hot Air as a Motive Power," in which he accepted Mayer's and Helmholtz's doctrine of the conservation of force; describing his differential regulator; and "On the Application of the Electric Spark to the Measurement of Velocity."

Werner Siemens became warmly interested in the experiments which Leonhardt was making, at the instance of the general staff of the army, in the substitution of an electrical apparatus for optical telegraphy. He had seen a model of Wheatstone's telegraph in the house of one of his comrades, and had tried to establish a communication between the house and a mineral-water establishment across the garden. He devised an improvement in the apparatus for generating and controlling the current, which attracted the attention of the mechanician Halske, who eventually gave up his business and associated himself with Siemens in telegraphy.

Siemens's plans were again embarrassed by the results of his and his companions' inconsiderately signing a paper connected with the religious movement of John Ronge, which was considered seditious. His brigade, to punish the offenders, was ordered to a retired post. It was important for him to remain in Berlin to prosecute his researches, and he devised a means to induce the Government to keep him there. Schönbein had made his first discovery of gun-cotton, but the material he produced was poor and unreliable. Siemens spent a day in experimenting upon it; added treatment with sulphuric acid, and obtained a certain and really practicable explosive. He communicated his discovery to the Minister of War, and was ordered to continue his experiments at the Spandau Arsenal, while his punishment was forgotten. Unfortunately, Prof. Otto, of Brunswick, who had independently discovered the same method, anticipated him in publication, and thus deprived him of the credit of priority.