. Bulletin. Science. 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 betw
. Bulletin. Science. 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 Pa
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