Figure 20. — Some of the various means used by Faraday to induce an electric 

 current by magnetism: (a) coil to induce a momentary current in another 

 coil by making or breaking the galvanic circuit in the first coil, (A, c) inducing 

 a momentary current by making or breaking a magnetic circuit, (d) inducing 

 a momentary current by moving a magnet through a coil of wire, and 

 (e) inducing a continuous current by rotating a conducting disk in a magnetic 

 field. The last was the converse of the Barlow wheel experiment. From 

 Philosophical Transactions, 1832, vol. 122, pi. 3. 



using three instead of two coils, by replacing the 

 single magnet by a compound one, and by placing 

 the axis of the instrument horizontally instead of 

 vertically (fig. 24) . Clarke used only a pair of coils, 

 but sought to increase the current by rotating the 

 coils beside the poles instead of in front of the poles 

 as in the Pixii and Saxton machines. Clarke made 

 two sets of coils for his magneto, one of fine wire for 

 high voltage and the other of coarse wire for large 

 currents (figs. 25, 26). 



Charles Page, of Washington, increased the output 

 of Clarke's magneto by increasing the intensity of the 

 magnetic field. He placed another compound magnet 

 parallel to that of the Clarke machine and then 

 rotated the coils between the two compound magnets 

 (figs. 27, 28). Such devices were made commercially 



Figure 2 1 . — Pixii magneto generator, without 

 commutator. From American Journal of 

 Science, April 1833. '^°'- ^4. P- 146. 



PAPER 30: DEVELOPMENT OF ELECTRICAL TECHNOLOGY IN THE 19TH CENTURY: III 



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