132 Trans. Acad. Sci. of St. Louis. 



The equation of the surface is therefore 



E= m * 



1 +6i 



See p. 112, 



E= 1.945 11,1 



1 + 0.635 i 



from figs. 14 and 16. 



This surface is given on fig. 17. The element of the sur- 

 face giving the condition of operation for constant resistance 

 being indicated. The surface is explained in connection with 

 figs, 5, 6, and 7. 



It follows therefore from the computations just given that 

 experimentally the relation between n 2 , i, and E may be de- 

 termined in the most convenient way and then this relation 

 may be used to obtain instantaneous values of the 

 speed of the apparatus to which thi3 small machine is con- 

 nected. This method has been used practically to determine 

 the fluctuations of speed of an engine caused by sudden 

 changes in its load. 



He. 



The Predetermination of the Operation of a Single 

 Series Motor as the only Load of a Series Generator. 



This problem was first defined by Gisbert Kapp who sums 

 up his observations in substance as follows — there can usu- 

 ally be found some speed and some resistance at which the 

 motor will operate at constant speed for all loads.* He has 

 been successful in obtaining the result desired in the installa- 

 tions he has made in England. 



Eric Gerard, f an eminent French authority, indorses 

 Kapp's solution of the problem. 



C. E. L. Brown, while with the Oerlikon Engineering Co., 

 of Switzerland, has also succeeded in operating motors installed 



* " Electrical Transmission of Energy," 4th edition, p. 199. 

 t u Lecons sur L' Electricity," Tome second, p. 189. 



