VI THE DIRECT-CURRENT MOTOR 



question of sparking. The advanced student will per- 

 ceive the analogy between the law of acceleration given in 

 Chapter VII. and that for the rise of current in an induc- 

 tive circuit, and may be tempted to pursue the subject for 

 himself. 



The numerical accuracy attempted has been limited 

 to that attainable with an ordinary ten-inch slide rule, 

 on which all the examples have been worked out. Impor- 

 tance is attached to the graphic method of solution, and 

 the diagrams are intended to serve as exercises for the 

 student, who should work out similar problems with 

 different data by the same methods. 



I have to thank in any friends for assistance, particularly 

 Mr. H. S. Hering, for allowing me to use the results of his 

 tests on electric cars ; Mr. L. H. Parker, for providing me 

 with particulars of the construction and performance of the 

 electric locomotives 011 the Baltimore and Ohio Railroad ; 

 Mr. H. P. Curtiss, for placing at my disposal the out- 

 come of his experiments on the Buffalo and Niagara Falls 

 Electric Railway ; and the Railway Department of the 

 General Electric Company, for furnishing me with valuable 

 information and data. 



C. A. CARUS-WILSON. 



McGiLL UNIVERSITY, MONTKEAL : 

 February 1898. 



