74 8 THE POPULAR SCIENCE MONTHLY. 



fuel, it possesses many points of superiority over the present cumber- 

 some, noisy, smoky locomotive. Indeed, in long passages such as those 

 in the mines at Zankerode, where a Siemens electric railway is now 

 running, a steam-locomotive would be not only undesirable but im- 

 possible. 



In the Zankerode-mine railway, the current is sent from the dy- 

 namo along the roof of the tunnel through one of the inverted T-rails 

 shown in Fig. 2, which thus acts as a conductor, and upon which slides 

 a contact-carriage connected with the motor on the car by one of the 

 flexible conductors, also shown. The return current coming from the 

 motor goes to the other inverted T-iron by the other flexible conduct- 

 or, and thence back to the dynamo. 



The most extensive electric railway now in use is that constructed 

 by Messrs. Siemens in Ireland, which runs from Portrush to Bush- 

 mills, a distance of about six miles. As at present operated, a dynamo 

 revolved by a stationary steam-engine supplies the necessary current ; 

 but it is intended to utilize the waste power of a waterfall situated 

 about three quarters of a mile from the end of the line, as soon as the 

 necessary works can be constructed. The cost of running the electric 

 locomotives is found to be less than that of running steam-locomotives 

 over the same track, and it will be much reduced as soon as the utiliza- 

 tion of the power of the waterfall (twenty-four feet) is made possible. 



By another system of electric propulsion, it has been attempted to 

 carry batteries of electric accumulators in the car, instead of conveying 

 the current to the car by conductors. By this system, as yet unde- 

 veloped, a large stationary engine is to be used to turn a dynamo 

 which will generate a current that will charge the accumulators or 

 " storage-batteries," as they are sometimes called ; these accumulators 

 to lie under the seats or in some other convenient place, and render the 

 current to the motor direct. 



As accumulators may play an important part in electric railroading, 

 and as much that is incorrect has appeared in print concerning them, 

 a few words of description may not be out of place. 



Probably the most prevalent conception of an accumulator is a box 

 or other receptacle in which electricity is put and from which it can 

 be drawn when desired ; and for practical purposes this idea is suffi- 

 ciently correct. From a scientific point of view, however, it is more 

 satisfactory to regard an accumulator as a battery in which the elec- 

 trical energy of the current which it renders arises from a chemical 

 action due primarily to another current which was sent through it. 

 To speak more in detail, the ordinary accumulator (Fig. 3) consists of 

 two lead plates standing in acidulated water and capable of behaving 

 like an ordinary voltaic battery, after they have been acted upon by a 

 strong current. This current, called the charging current, when it goes 

 through the liquid, decomposes it, the oxygen, separated, going to one 

 lead plate and the hydrogen to the other lead plate. The oxygen at- 



