WILLIAM SIEMENS, F.R.S. 163 



Academy of Sciences on the same subject fully a month previous 

 to the two communications referred to in your article. 



This communication was not published at the time the Royal 

 Society papers were presented, but suffices to give Dr. Werner 

 Siemens a prior claim. 



Yours faithfully, 



C. WILLIAM SIEMENS. 



12, QUEEN ANHE'S GATE, WESTMINSTER, Oct. 20, 1877. 



To THE EDITOR OF "ENGINEERING." 



SIR, Among the letters written to you in consequence of your 

 article on " The Electric Light," contained in your issue of the 

 19th inst., is one by Mr. C. Varley, claiming to be the original 

 discoverer of the dynamo-electric or reaction principle involved 

 in the machines now employed for producing intense light. 

 Mr. Varley refers your readers to a provisional specification which 

 he filed on the 24th of December, 1866, and which will have been 

 published in due course by the Patent Office in July, 1867. 



It appears strange that when the first publication of the 

 principle in question took place through the reading of my paper 

 sent into the Royal Society on the 14th of February, 1867, and 

 Professor Wheatstone's sent in on the 24th, Mr. Varley did not 

 come forward to join in the discussion, which created considerable 

 interest among scientific men at the time, nor did Mr. Varley ever 

 file a complete specification of his patent. As a matter of fact, 

 therefore, the first publication of the principle took place in the 

 Proceedings of the Royal Society in February, 1867. 



But as regards the dates of invention, I may add that my 

 brother Werner tried his first experimental machine in December, 

 1866. I was present at Berlin during these early trials, which 

 were in fact undertaken in consequence of a discussion between 

 my brother and myself regarding the question whether the 

 dynamical principle of the convertibility of natural forces was 

 applicable generally. 



It occurred to my brother that if this were the case an electric 

 current must result in driving an electro-magnetic machine in the 



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