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444 Mr. H. Wilde on some Improvements in 



So far as I have communicated the results of my investigations 

 on the principle of accumulative action in electrodynamics, they 

 have been obtained with machines designed with reference to the 

 peculiar form of armature contrived by Dr. Werner Siemens, of 

 Berlin. While possessing several advantages in point of efficiency 

 over that of Saxton, the Siemens armature requires to be driven at 

 a high velocity to produce a succession of currents sufficiently 

 rapid to be available as a substitute for the voltaic battery. Little 

 inconvenience, however, arises from the high speed when the ar- 

 matures are of small dimensions; but as the dimensions increase 

 it becomes necessary to lower the speed, and the large machines 

 are consequently not proportionately powerful in comparison with 

 the smaller ones. Besides this, the advantage possessed by this 

 form of armature, in having the moving mass of metal near the 

 axis of rotation, is neutralized as the dimensions increase, by the 

 excessive heat generated by the magnetization and demagnetiza- 

 tion of the iron. It would also be convenient in some circum- 

 stances to drive a machine direct from the crank or flywheel of 

 a steam-engine without the intervention of multiplying gearing. 



Considerations of this nature led me, towards the end of 1866, 

 to propose to myself the construction of an electromagnetic 

 machine with multiple armatures, which should remove the in- 

 conveniences inherent in those hitherto constructed by produ- 

 cing a greater number of currents for one revolution of the 

 armature axis. Since that time I have been engaged, with 

 more or less interruption, in carrying out this design, and have 

 at length constructed a machine the performance of which sur- 

 passes all my previous essays in this direction in regard to power 

 and efficiency, and with a considerable reduction in the quantity 

 of the materials employed*. 



The machine in which these results are embodied is repre- 

 sented in Plate VIII. figs. 1 and 2. In these views A y , A y are the 

 two sides of a circular framing of cast iron, firmly fixed together 

 by the stay rods B y , B y and the bridge C r A heavy disk, D,, of 

 cast iron is mounted on a driving shaft E,, running in bearings 

 fitted to each side of the framing. One of these bearings, F ; , is 

 carefully insulated from the framing by suitably formed pieces 

 of ebonite, and also from the shaft by a cylinder of the same 

 substance. Through the side of the disk and parallel with its 

 axis sixteen holes are bored, at equal angular distances from 



* To afford myself leisure to carry out my designs on a large scale with- 

 out being involved in questions affecting the priority of my results, a general 

 description of the improvements which form the subject of this paper was 

 deposited in due form with the Commissioners of Patents, London, De- 

 cember 1866 and March 1867, and with the Ministere de I'Agriculture et 

 des Travaux publics, Paris, June ,1867. 



