

Figure 5. — Scene from the last act of the ballet "Electra, or 

 the Last Pleaid." From Illustrated London News, May 5. 1849. 

 vol. 14, p. 293. 



be carried on at night. These preliminary results ' 

 were very encouraging, but Staite's death brought an 

 end to the project. 



A portion of Staite's success was due to his inven- 

 tion of a practical automatic regulator that eliminated 

 the necessity of moving the carbons by hand as they 

 were consumed (fig. 6).* The amount of current 

 flowing through the arc controlled the spacing of the 

 carbons by balancing a mechanical force with the 

 attractive force of a solenoid. As the carbons burned, 

 the arc became longer and the current became less 

 due to the increased resistance. The decreased 

 attractive force of the solenoid permitted the carbons 

 to move closer together in .Staite's 1847 regulator 



^Mechanics Magazine, 1849, vol. 50, pp. 538-539; 1850, 

 vol. 52, p. 35; 1851, vol. 54, pp. 411-412; vol. 55, pp. 316- 

 317; 1852, vol. 57, p. 217. 



8 British patents 11449 (November 12, 1846), 11783 (July 3 

 1847), 12212 (July 12, 1848), 12772 (September 20, 1849) 

 634 (March 14, 1853); Mechanics Magazine, 1848, vol. 48, pp 

 49-56; 1849, vol. 50, pp. 49-58, 73-80; 1850, vol. 52, pp 

 246-248; Illuslraled London .V«M, January 1849, vol. 14, p. 58 



by controlling a clockwork and in his 1853 regulator 

 by controlling the height of a float. This solenoid 

 control came to be a basic feature in the design of 

 all the later successful regulators. Other factors 

 contributing to the success of Staite's lamp were the 

 semi-enclosure of the arc in a chamber to reduce 

 the consumption of the carbons (a feature that was 

 not again used until the 1890's, but then with great 

 success) and the use of the hard carbon from coke 

 retorts rather than the much softer charcoal. Fou- 

 cault's regulator was based on the same solenoid 

 principle as that of Staite's, but it was set up hori- 

 zontally so that, as the attractive force due to the 

 solenoid became weaker due to the lengthened arc, 

 a detent released a clockwork that moved the elec- 

 trodes together. 



In the meantime, other regulators had appeared 

 (figs. 8, 9). In France, Archereau, in 1849, also in- 

 vented a regulator that iaalanced the weight of the 

 carbon electrode against the attractive force of a 

 solenoid (fig. 10), but the system was too insensitive 



338 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



