Figure 15. — Another form of the differential 

 arc-light regulator of Lacassagne and Thiers. 

 Two circuits — one permitting and one stop- 

 ping the flow of mercury from the reservoir 

 (a) — controlled the position of the float, to 

 which the lower carbon was fixed. A similar 

 differential principle formed the basis for all 

 the later successful regulators. From J. 

 Dredge, Electric Illumination, London, n.d. 

 (about 1882), vol. I, p. 392. 



invented by Faraday himself in November 1831. He 

 called this new device a magnetoelectric generator, 

 in contrast to the electrostatic generator; later, the 

 term was shortened to "magneto." This first mag- 

 netoelectric generator was, interestingly enough, 

 the converse of Barlow's "wheel," a simple electric 

 motor. Faraday's generator could not produce sparks 

 or electrolyze water, but it did deflect the needle of 

 a galvanometer. 



A somewhat more efficient device was produced by 

 Hippolyte Pixii, who had been instrument-maker 



Figure 16. — One of the earliest (1857) versions 

 of .Serrin's arc-light regulator. From T. du 

 Moncel, Expose des applications de I'electricite, 

 Paris, ed. 2, 1856-1862, vol. 4, p. 493. 



to D. F. J. Arago and A. M. Ampere for a number of 

 years. Pixii's magneto generator (fig. 21), which was 

 first demonstrated in a lecture by Ampere at the 

 Sorbonne in September 1832, consisted of a 2-kg. 

 horseshoe magnet mounted on a vertical axis that 

 could be rotated before the poles of an electromagnet 

 that acted as armature to the magnet. The electro- 

 magnet was about 8 cm. high and had 50 meters of 

 copper wire on it. The alternate passage of first a 

 north and then a south pole before the poles of the 

 electromagnet produced an alternating current that 

 went first in one direction along the wire and then 

 the other, in contrast to the current from chemical 

 cells that always went in the same direction. Al- 

 though the resulting gases were mixed, Pixii's magneto 



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



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