74 Professor W. E. Ayrton on Electric Bailways. [March 24, 



But more than this, not only does the train take off current from 

 the section 1 when it is just leaving it, and entering section 2, but no 

 following train entering section 1 can receive current or motive power 

 until the preceding train has entered section 3. [Experiments were 

 then shown proving that with this system a following train could not 

 possibly run into a preceding train even if the preceding train stopped 

 or backed.] Now why does the following train when it runs on to a 

 blocked section pull up so quickly ? The reason is because it is not 

 only deprived of all motive power, but is powerfully braked, since 

 when electricity is cut off from a section the insulated and non- 

 insulated rail of that section are automatically connected together, so 

 that when the train runs on to a blocked section the electro-motor 

 becomes a generator short circuited on itself, producing, therefore, a 

 powerful current which rapidly pulls up the engine. [Experiments 

 were then shown of the speed with which an electro-motor, which had 

 been set in rapid rotation and then deprived of its motive current, 

 pulled up when its two terminals were short circuited.] 



Whenever, then, a train, it may be even a runaway engine, enters 

 on a blocked section, not only is all motive power withdrawn from it, 

 but it is automatically powerfully braked, quite independently of the 

 action of the engine-driver, guard, or signalman. No fog, nor colour- 

 blindness, nor different codes of signals on different lines, nor mistakes 

 arising from the exhausted nervous condition of overworked signal- 

 men, can with this system produce a collision. The English system 

 of blocking is merely giving an order to stop a train ; but whether 

 this is understood or intelligently carried out is only settled by the 

 happening or non-happening of a subsequent collision. Our Absolute 

 Automatic Block acts as if the steam were automatically shut off and 

 the brake put on whenever the train is running into danger ; nay, it 

 does more than this — it acts as if the fires were put out, and all the 

 coal taken away, since it is quite out of the power of the engine-driver 

 to re-start his train until the one in front is at a safe distance ahead. 



But all trains will undoubtedly be lighted with electricity ; must, 

 then, the train be plunged into darkness when it runs on to a blocked 

 section to which no electric energy is being supplied ? No ! If some 

 of the electric energy supplied to the train when it is on an unblocked 

 section be stored up in Faure's accumulators, such as are at present 

 used on the Brighton Pulman train, the lamps will continue burning 

 even when the train has ceased to receive electric energy from the 

 rubbed rail. 



When, then, we commit the carrying of our power to that fleet 

 messenger to which we have been accustomed to entrust the carrying 

 of our thoughts, then shall we have railways that will combine speed, 

 economy, and safety ; and last, but not least to us Londoners, we shall 

 have the entire absence of smoke, the presence of which nearly causes 

 the convenience of the Underground Railway to be balanced by the 

 pernicious character of its atmosphere. 



[W. E. A.J 



