. Bulletin. Science. Figure 48.—Dal Negro's electromagnetic machine. From Annali delle Scienze de Regno Lombardo-Veneto, March 1834, pi. 4. It had the essentials of a modern DC motor: a magnet to provide the field, an electromagnet as armature, and a commutator to apply the mechanical forces at the right time. The reciprocating motion of an arma- ture, see-sawing up and down, made and broke con- tact during the motor's cycle so that the electromagnet pulled on the part of the armature farthest away. Salvatore dal Negro '^ of the university at Padua reported in 1834 on an invention that he had
. Bulletin. Science. Figure 48.—Dal Negro's electromagnetic machine. From Annali delle Scienze de Regno Lombardo-Veneto, March 1834, pi. 4. It had the essentials of a modern DC motor: a magnet to provide the field, an electromagnet as armature, and a commutator to apply the mechanical forces at the right time. The reciprocating motion of an arma- ture, see-sawing up and down, made and broke con- tact during the motor's cycle so that the electromagnet pulled on the part of the armature farthest away. Salvatore dal Negro '^ of the university at Padua reported in 1834 on an invention that he had worked out in 1831 of a permanent magnet pendulum kept in oscillation by an electromagnet that changed its polarity by a commutator switch (fig. 48). He added a linkage device so that he could raise a weight with it and found it lifted 60 grams, 5 centimeters in one second. A similar pendulum-instrument was made in 1834 by J. D. Botto«^ in Turin. '2 Salvatore dal Negro, "Nuova Macchina elettro-magnetica immaginata dalFAbate Salvatore dal Negro," Annali delle scienze de regno Lombardo-Veneto, March 1834, pp. 67-80. ^ J. D. Botto, "Note sur I'application de relectro-magnetism a la mecanique," Bibliothique universelle, sciences et arts, 1834, vol. 56, pp. 312-316. Probably the first man to produce the rotary motion of an electromagnet was an English experi- menter, Rev. William Ritchie,** in 1833. At the end of an article on the attractive force of an electro- magnet, he described how an electromagnet could be made to spin and how he was able to set the magnet in sufficiently rapid rotation to raise several ounces over a pulley (fig. 49). About the same time. Dr. T. Edmundson of Baltimore, Maryland, devised a kind of magnetic paddlewheel motor *^ (fig. 50). During the period of the 1820's and early 1830's, the most successful experimenters with electro- magnetism—men like Faraday, Barlow, Sturgeon, Henry, and Ritchie—used chemical cells like Hare's calor
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