620 ELECTRICAL ENGINEERING 



figure in the study of the problem before us. The cost of the equip- 

 ment is a different matter; it does cut a very important figure 

 in the operating expenses of the road, and it seems to be admitted 

 on all sides that the cost of the electrical traction equipment 

 would be considerably higher than that which accompanies the 

 employment of the steam locomotive. But the increased transpor- 

 tation capacity of the tracks and the increased safety of trans- 

 portation would and should more than balance this increase in the 

 cost of equipment. 



The third question is: Can the continuity of service be suffi- 

 ciently well secured with the prevailing methods of electrical trac- 

 tion? To find a complete and satisfactory answer to this question 

 is the most difficult part of the problem. 



With the present method of steam locomotive traction every 

 train with its locomotive is an independent unit, so that an acci- 

 dental derangement of any one of the units does not interfere very 

 seriously w r ith the operation of the rest of the road. A blizzard or 

 a flood may, to be sure, cause a suspension of operations on the whole 

 road, but nothing short of this inimical action of the elements is 

 capable of producing this result. In electrical traction, on the 

 other hand, the various units on the road are all interconnected 

 through the conducting wires which connect them with the power 

 stations. Any accident which suspends the operativeness of a power 

 station will bring to a standstill the whole traffic on the section 

 which is fed by that particular station. This difficulty, however, 

 exists also in the electrical distribution of power for lighting pur- 

 poses in large towns, and past experience shows that the present 

 methods of electrical central station construction and manage- 

 ment make the risks of discontinuity in the service on this score 

 extremely small. It must be remembered, however, that distri- 

 bution of power for lighting purposes in large towns employs un- 

 derground conductors, which is one of the most effective means 

 of protecting the continuity of service against the hostile action of 

 seasons and elements. In heavy electrical traction, underground 

 conductors are out of question for reasons which are so evident 

 that they need no further discussion. This introduces one of the 

 most serious difficulties into our problem. 



The third-rail method limits the practicable electrical pressure 

 at which the electrical energy is conveyed into the train; besides, 

 it introduces the very serious difficulty of maintaining a sufficiently 

 good electrical contact during the winter season when the ground 

 is covered with ice and snow, not to mention several other diffi- 

 culties which, it is generally admitted, render the third-rail method 

 entirely inadequate to heavy electrical traction. The overhead 

 trolley seems, in the opinion of the majority of competent engineers, 



