. Bulletin. Science. Figure 62.—Gramme's first commercial dy- namo for electroplating. From Revue indus- trielle, November 25, 1874. p. 406, fig. 5. consequences delayed the entrepreneurs for a time. Instead the Societe commissioned the instrument- maker Breguet to make magneto generators with a ring armature in the early 1870's for laboratory and small shop use.^' The experience gained by varying the form of these small magneto generators served as a guide in the later construction of the Gramme dynamo. In 1871 Gramme presented to the Academic des Sciences a generator based on Ladd's design b
. Bulletin. Science. Figure 62.—Gramme's first commercial dy- namo for electroplating. From Revue indus- trielle, November 25, 1874. p. 406, fig. 5. consequences delayed the entrepreneurs for a time. Instead the Societe commissioned the instrument- maker Breguet to make magneto generators with a ring armature in the early 1870's for laboratory and small shop use.^' The experience gained by varying the form of these small magneto generators served as a guide in the later construction of the Gramme dynamo. In 1871 Gramme presented to the Academic des Sciences a generator based on Ladd's design but with Gramme's ring armatures instead of Siemens' shuttle armatures. A parallel pair of horizontal bar- electromagnets, one above the other, had ring armatures between the poles at each end of the pair. One ring armature supplied current for the electro- magnets and the other supplied the output current. An article appearing in the Comptes renins brought the new kind of armature to the attention of the scientific world and served to stimulate several investigators to try to determine how the current was induced in it.'- Gramme patented in 1872 a machine that combined the use of the ring armature, wire brushes to collect the current from the armature, and field excitation by a magneto, the armature of which was on the same arbor as that of the electromagnet generator. By the end of that year the first commercial Gramme generator appeared on the market (figs. 62, 63).'' While this machine was still based on the design of Ladd's apparatus, the modifications considerably improved the efficiency. Instead of using bar- electromagnets arranged horizontally. Gramme used cylindrical electromagnets and arranged them verti- inventions of the 1860's were based on magneto- electric machines of the multiple-disk Woolrich type, although one of the specifications in his patent of February 26, 1867, implied self-excitation.^" As mentioned previously, he patented the ring armature in 18
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