440 Mr. H. Wilde on some Improvements in 



intensify their magnetism, which, in its turn, reacts upon the 

 armatures and intensifies the current." 



Whether it be that electricians are not in the habit of reading 

 engineering journals, or that information communicated to them 

 in the form of letters is lost in the plethora of printed matter of 

 all kinds which engages the attention of the reading public, Mr. 

 Murray's warning to inventors against patenting his idea has 

 been disregarded, as a patent was taken out on December the 

 24th of the same year by C. and S. A. Varley for " improvements 

 in the means of generating electricity," wherein is described a 

 machine consisting of two electromagnets and two bobbins. The 

 bobbins are mounted on an axle, on which also a commutator is 

 fixed; the ends of the insulated wire surrounding the bobbins 

 are connected with this commutator, and through it with the 

 insulated wire of the electromagnets, forming the whole into one 

 electric circuit. Before using the apparatus, an electric current is 

 sent through the electromagnet for the purpose of securing a small 

 amount of permanent magnetism in the iron core of the electro- 

 magnet. On revolving the axle, the bobbins become slightly mag- 

 netized in their passage between the poles of the electro-perma- 

 nent magnets, generating weak currents in the insulated wire 

 surrounding them. The effect of the current passing through the 

 electromagnets is to increase their magnetism and magnetize in 

 a higher degree the bobbins when passing between the poles of 

 the electromagnets; and in this way the electromagnets and the 

 bobbins act and react on each other, causing the circulation of 

 increased quantities of electricity. 



Another patent for the same idea was taken out by C. W. 

 Siemens, F.R.S., on January the 31st, 1867, as a communica- 

 tion from Dr. Werner Siemens, of Berlin. The invention is de- 

 scribed as having for its object the obtaining of powerful electric 

 currents without the aid either of large batteries or of permanent 

 magnets, by the following method : — A movable keeper or arma- 

 ture surrounded with a coil of insulated wire is arranged in front 

 of the poles of an electromagnet; and after rotatory motion is 

 imparted to the armature, a magnetic impulse is given to the 

 electromagnetic arrangement by the momentary insertion of a 

 galvanic battery into the circuit, which steadily and rapidly aug- 

 ments simultaneously with an increasing electric current in the 

 coils. For reproducing a current after the machine is arrested 

 no fresh impulse from the battery is needed, because the resi- 

 dual or permanent magnetism of the electromagnet is sufficient 

 to commence inductive action. 



Although private letters addressed from one person to an- 

 other ought never to be received as evidence in questions affecting 

 the priority of scientific discovery or invention, yet, for the pur- 



