E— Q-sB fTa l— j Ujj j aa aa gia cB gaJa^ — ^ 



LLLLUiiLLLLLJ 



Figure 43. — Above, Double lighthouse at Cap 

 de la Heve outside the harbor of Le Havre. 

 At right, Arrangement of the steam engines 

 and the Alliance generators in the south 

 lighthouse. From E. AUard, Phares et balises, 

 vol. 5 of Les Travaux publics de la France, 

 L. Reynaud, ed., Paris, 1883, pp. 59, 109. 



tabulation, the Alliance generator produced approx- 

 imately the same carcels per horsepov\'er as it had 

 in the South Foreland tests, the Gramme dynamo had 

 improved somewhat, and the De Meritens magneto, 

 surprisingly enough, pro\-ed to be about as efficient 

 as the Gramme machine: 









Mechan- 

 ical hp. 



Mean sphericat 

 intensity {Carcels') 



Generator 





R.p.m. 



absorbed 



Total 



Per hp. 



Alliance 





450 



4.6 



275 



60 



Gramme, large 





550 



11. 5 



1010 



88 



Gramme, small 





600 



5.5 



493 



91 



Gramme, improved small 



680 



4.2 



342 



81 



De Meritens, low 



speed 



431 



5.8 



537 



93 



De Meritens, high 



speed 



827 



11.9 



1015 



85 



From these figures and from the results of other 

 tests that are mentioned below, it can readily be seen 

 that the dynamo was a great advance over the older 

 machines in terms of bulk, weight, candles produced 

 per horsepower, and initial cost. Despite such 

 advantages, the magnetoelectric machine was not 

 displaced by the dynamoelectric machine until the 

 end of the 1870's, and even then not completely. 



The changes that made possible a mechanically 

 and electrically more efficient generator were intro- 

 duced into experimental machines during the very 

 slow commercial expansion of magneto generators in 

 the 1860's. These basic modifications were changes 

 in the design of the armature, the substitution of 

 electromagnets for pennanent magnets as a means of 

 producing the field, and the introduction of self- 

 excitation where the current induced in the armature 

 passed through the field coils and produced ^the 

 field in which the armature is placed. The last 

 modification was the one that is considered character- 

 istic of the dynamo. Although it took over a decade 

 for these innovations to be combined in one machine, 

 they laid the foundation for the modern dynamo. 



The first basic improvement in the form of the 

 armature was due to Werner Siemens, at that time 

 a well-known telegraph inventor and one of the 

 partners in the Siemens and Halske firm in Berlin. 

 In 1856 he replaced the disk armature that had been 

 used in practically all the previous machines by a 

 much simpler one shaped like a weaver's shuttle, with 



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



369 



