Figure 36. — Side and end elevations of Holmes' magneto generator that was installed at 

 Dungeness. From Minutes of Proceedings of the Institution of Civil Engineers, 1878- 1879, 

 vol. 57, pi. 5. 



machines, with that of the dynamo generator. At 

 the time the magnetoelectric machines were in 

 coinmercial use, the system of practical electrical 

 units had not been worked out; consequently, what 

 little information is available is not always meaningful, 

 but at least one can obtain some sense of the relative 

 merits of the equipment. 



One method of measuring the output of an electrical 

 machine was to determine it in terms of the chemical 

 cell. In tests inade in 1862 it was shown that a 4-disk 

 Alliance machine was equivalent to 64 Bunsen cells. '' 

 The tests that Jamin and Roger performed in 1863 

 showed that a 6-disk Alliance machine produced a 

 voltage equal to that of 226 Bunsen cells when the 

 disks were connected in series and, as might be 



anticipated, a voltage equal to 38 Bunsen cells when 

 the disks were connected in parallel.™ 



Also, one could obtain a crude comparison of the 

 efficiency of various machines by determining the 

 amount of light that each machine produced per unit 

 horsepower. However, these comparati\'e estimates 

 are necessarily nominal because the candlepower of the 

 arc and the horsepower necessary to produce the 

 candlepower were not measured together, at least 

 until 1880; consequently, such estimates should be 

 considered with caution. Another factor that casts 

 doubt on these estimates is that the figures were used 

 to sell the generators rather than to represent scien- 

 tific measurements. Nevertheless, the figures are 

 indicative of the order of magnitude, and they became 



^"Cosmos, 1862, vol. 20, pp. 686-694. 



'Jamin and Roger, op. cit. (footnote 64). 



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



363 



