THE ELECTRIC LIGHT 453 



mature currents were obtained vastly stronger than those 

 generated by the small magneto-electric machine. These 

 currents might have been immediately employed to pro- 

 duce the electric light; but instead of this they were 

 conducted round a second electro-magnet of vast size, 

 between whose poles rotated a Siemens armature of cor- 

 responding dimensions. Three armatures therefore were in- 

 volved in this series of operations: first, the armature of 

 the small magneto -electric machine; secondly, the arma- 

 ture of the first electro -magnet, which was of considerable 

 size; and, thirdly, the armature of the second electro-mag- 

 net, which was of vast dimensions. "With the currents 

 drawn from this third armature, Mr. Wilde obtained ef- 

 fects, both as regards heat and light, enormously tran- 

 scending those previously known. 1 



But the discovery which, above all others, brought the 

 practical question to the front is now to be considered. 

 On the 4th of February, 1867, a paper was received by 

 the Royal Society from Dr. "William Siemens bearing the 

 title, "On the Conversion of Dynamic into Electrical Force 

 without the use of Permanent Magnetism. ' ' 8 On the 14th 



1 Mr. Wilde's paper is published in the "Philosophical Transactions" for 

 1867, p. 89. My opinion regarding Wilde's machine was briefly expressed in 

 a report to the Elder Brethren of the Trinity House on May 17, 1866: "It gives 

 me pleasure to state that the machine is exceedingly effective, and that it far 

 transcends in power all other apparatus of the kind." 



2 A paper on the same subject, by Dr. Werner Siemens, was read on Janu- 

 ary 17, 1867, before the Academy of Sciences in Berlin. In a letter to "Engi- 

 neering," No. 622, p. 45, Mr. Robert Sabine states that Professor Wheatstone's 

 machines were constructed by Mr. Stroh in the months of July and August, 

 1866. I do not doubt Mr. Sabine's statement; still it would be dangerous in 

 the highest degree to depart from the canon, in asserting which Faraday was 

 specially strenuous, that the date of a discovery is the date of its publication. 

 Toward the end of December, 1866, Mr. Alfred Varley also lodged a provisional 

 specification (which, I believe, is a sealed document) embodying the principles 



