Figure 45. — Generator room in the south lighthouse at Cap de la Heve, showing the two sets 

 of Alliance generators. From E. Allard, Phares et balises , vol. 5 of Les Travaux publics 

 de la France, L. Reynaud, ed., Paris, 1883, 48th plate at end of volume. 



the same weight. Also, the more compact form made 

 possible a more rigid structure, and Siemens could 

 reduce the air gap between the magnetic pole and the 

 armature to a very small amount, thus increasing the 

 magnetic flux cut by the wires of the armature as 

 well as the speed of rotation. Moreover, the armature 

 was located between the poles where the flux density 

 was greatest instead of beside the poles where the 

 flux density was much less. Consequently, the over-all 

 electrical efficiency was increased to the point where 

 the heating of the armature became a problem for 

 the first time. Because of these advantages, the 

 shuttle armature was used in the most successful 

 generators of the next decade or so. Siemens applied 

 his shuttle generator to operate an indicator telegraph. 

 Another innovation that seemed to promise still 

 greater efficiency was the ring armature, first devised 



by a man named Elias in the 1840's (fig. 50). Antonio 

 Pacinotti, a student at the University of Pisa, again 

 invented such an armature for an electric motor in 

 1863 (figs. 51, 52) but his call to military duties pre- 

 vented him from developing it.''^ The practical de- 

 velopment of the ring armature was due to Zenobe 

 T. Gramme who, in 1870, patented a magneto gen- 

 erator with a toroidal core of soft iron wire that had 

 many coils of copper wire wound around the core and 



"s Antonio Pacinotti, ''Descrizione di una macchinetta elet- 

 tromagnetica," 11 Nuovo Cimento, 1863, vol. 19, pp. 378-384; 

 "Sur line Machine electromagnetique, construite en 1860, 

 d'apres le meme principe que la machine de M. Gramme," 

 Comptes rendus, 1871, vol. 73, pp. 543-544; Franklin L. Pope, 

 "The Genesis of the Modern Dynamo — Antonio Pacinotti," 

 Electrical Engimer, 1892, vol. 14, pp. 259-262, 283-284, 307, 

 339-341. 



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



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