98 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
or so for which it is designed, while if both motors were 
in series on a 1000 volt circuit, a short circuit in one of 
them, would probably cripple its mate. Even slipping of 
one might overload the other and imperil both. On the 
other hand, serious relative slipping, throwing the load on 
  
F1c. 58. 
one motor when operating in series, is not common on the 
dirty city streets where the series connection is most used, 
and would be still less likely to occur on the comparatively 
clean and unobstructed tracks of a long.line. When one 
set of wheels slips the other soon follows suit, from the 
same cause, and there is usually a strong mechanical ten- 
dency to equalize slipping. FEven admitting the difficulty, 
there would certainly be no serious trouble of this sort if