Figure 49. — Ritchie's motor. From Philosophi- 

 cal Transactions oj the Royal Society oj London, 

 1833, vol. 123, p. 316, pi. 7. 



polarization and secondary action, as was true of all 

 its predecessors. 



Beginning in the middle 1830's chemical cells were 

 being invented that avoided the polarization and 

 local action of earlier cells. These new cells were 

 good sources of current, and they could produce 

 this current over a longer period of time than could 

 the earlier cells. In addition scientists understood 

 better how to build a strong electromagnet, and how 

 to turn its force on and off by a commutator. It was 

 no accident that electric motors began to seem prac- 

 tical to inventors in the 1830's, for the main elements 

 of a motor were present; it was not long before 

 inventors began to assemble these elements into a 

 device that could be used to drive machinery. 



In 1836 William Sturgeon ^^ asserted that he had 

 constructed an electric motor in the fall of 1832 (fig. 

 51), had demonstrated it in March 1833, and had 

 later used it to run models of machinery. Francis 

 Watkins *^ made electric motors (fig. 52) in 1835 

 that could also be used to drive mechanical models. 



In May 1834 M. H. Jacobi '* built an electric 

 motor (fig. 53) that could lift 10 to 12 pounds at a 

 speed of one foot per second when tested by a Prony 

 brake. Further details on this motor, showing how 

 much zinc was needed to produce a given amount 

 of mechanical work, appeared the following year.*^ 

 Jacobi claimed that a half-pound of zinc would 

 deliver the "demi-force d'un homme" for 8 hours. 



S9 William Sturgeon, "Description of an Electro-Magnetic 

 Engine for Turning Machinery," Sturgeon's Annals of Electricity, 

 1836, vol. 1, pp. 75-78. 



" Francis Watkins, "On Magneto-Electric Induction," 

 Philosophical Magazine, 1835, vol. 7, pp. 107-113; "On Electro- 

 Magnetic Motive Machines," Philosophical Magazine, ser. 3, 

 1838, vol. 12, pp. 190-196. 



88 M. H. Jacobi in Vlnstitut, 1834, vol. 2, pp. 394-395. 



8° Jacobi, op. cit. (footnote 76). 



Figure 50. — Edmondson's motor. From Ameri- 

 can Journal of Science, 1834, vol. 26, p. 205. 



Figure 51. — Sturgeon's motor. From Stur- 

 geon's Annals of Electricity, 1837, vol. i, pi. 2, 

 fig. 17. 



In a petition in May 1837 to the Russian czar, 

 Jacobi expressed his high hopes for a well-supplied 

 workshop and 8,000 rubles for 8 years in order to 

 "cover the Neva rather than the Thames or Tiber 

 with magnetic boats." ^^ By 1838 Jacobi was able 



'" D. V. Efremov, The Electromotor in its Historical Development, 

 Moscow and Leningrad, 1936, pp. 230-247. (In Russian.) 



262 



BULLETIN 228 : CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



