■~4ailiiB£irCiijiiiuu» 1 



lUiiljli 



Figure 30. — Woolrich's second magneto gen- 

 erator, made in 1851. From VV. H. Carbutt, 

 "Early Electro-Plating Machines," The Metal 

 Industry, new ser., February 1914. vol. 12, 

 p. 61. 



probable that a good part of Holmes' later difficulties 

 stemmed directly from these restrictions. 



Holmes sought to meet the requirements imposed by 

 Trinity House by reversing the role of the permanent 

 magnets and the electromagnets, and by increasing 

 the strength of the magnetic field between the two. 

 He filed for a patent on the revised form of his 

 generator in 1857 (fig. 35).^" In the new version, 

 two disks bearing the electromagnets were rotated 

 between three banks of stationary permanent magnets. 

 The steam engine was shown in the patent drawing 

 as directly coupled to the generator. The number of 

 permanent magnets was increased from 6 per disk 

 to 20 per bank and the coils from 24 per bank to 80 

 per disk. The air gap between the electromagnets 

 and the permanent magnets was considerably reduced. 



Two machines of the preceding design were tried at 

 the relatively new South Foreland lighthouse on the 

 eastern end of the Straits of Dover. They were about 

 twice as large as those used in the preliminary trials 

 at Blackwall, each being 9)i feet wide, 5J^ feet deep, 

 9 feet 6 inches high, and weighing 5}^ tons. Each 



generator was coupled directly to a 3-hp. steam 

 engine that drove it at the maximum permissible 

 speed of 90 r.p.m. A Duboscq regulator maintained 

 the carbons of the electric arc at the proper distance. 



The trials began on December 8, 1858, but results 

 were unsatisfactory and they were discontinued; they 

 were started again in March 1859 and continued 

 until the early months of 1860. The arc was apt to 

 go out several times during a night, so that an extra 

 attendant was required just to watch it, but the light 

 could be started again at a touch. After Faraday 

 examined the arc in April 1859 he declared that 

 "Holmes has practically established the fitness and 

 sufficiency of the magneto-electric light for lighthouse 

 purposes."^' Faraday recommended that Holmes' 

 system be permanently installed and tried under 

 actual operating conditions in a lighthouse for a 

 much longer period of time. Also, he reported 

 publicly on the results of Holmes' system in a lecture 

 given in March 1860 before the Royal Institution, 

 again declaring the result of the experiment to be 

 successful.''' The point source proved to be admirably 

 adapted to the Fresnel lens system, and the arc light 

 that was so glaring pro\'ed to be visible at greater 

 distances than an oil flame. But there was still the 

 problem that had to be faced with all new inventions: 

 whether the initial capital investment might prove 

 to be too great and whether the equipment could 

 be economically maintained. No final decision on 

 its use had been made, for there was the "matter 

 of expense and some other circumstances to be 

 considered." 



In the meantime Holmes had devised a regulator 

 similar to that of Serrin. The Holmes system was 

 exhibited in the lighthouse at Dungeness (fig. 36) 

 at the western end of the Straits of Dover in February 

 1862,'"' but it was not permanently installed until 

 June 6, 1862, because three more men had to be 

 added to the personnel at the lighthouse and it was 

 difficult to obtain competent keepers. The machinery 

 used was the same as that installed at South Foreland. 



37 British patent 2628 (.\pril 14, 1858). 



^'^ Electrician, London, 1862, vol. 3, p. 67; 1863, vol. 3, p. 

 288; vol. 4, pp. IH-T). See also Holmes, op. cit. (footnote 36) 

 and Richard, op. cit. (footnote 36). 



3' Michael Faraday, "On Lighthouse Illumination — The 

 Electric Light," Proceedings oj the Royal Society, 1858-1862, vol. 

 3, pp. 222-223; Electrician, London, 1863, vol. 4, pp. 68, 

 122-124. 



■"> Holmes, op. cit. (footnote 36); Richard, op. cit. (footnote 36). 



354 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



