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 dalF Abate 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 

 calorimotor. The calorimotor was one of the best 

 cells available, but even so it was bulky in volume and 

 the current it supplied rapidly decreased because of 



'' W. Ritchie, "Experimental Researches in Electro-Mag- 

 netism and Magneto-Electricity," Philosophical Transactions, 

 1833, vol. 123, pp. 313-321. 



85 T. Edmondson, "The Rotating Armatures," American 

 Journal oj Science, 1834, vol. 26, pp. 205—206. 



PAPER 28: DEVELOPMENT OF ELECTRICAL TECHNOLOGY IN THE 19TH CENTURY: I 



261 



