Manchester Alemoirs, Vol. xlvi. (1901), No. S. 5 



happens when the locomotive decreases its speed with 

 moderate suddenness, and naturally also when coming to 

 rest ; but in these cases, of course, it is the buffers and 

 not the couplings which have to bear the blows. Under 

 favourable conditions one may occasionally notice a re- 

 flection of the pressure-pull wave from the last truck, 

 particularly if it be an empty one, because the pull between 

 the two last trucks is in excess of the wheel friction, and 

 imparts to this truck a velocity 2V \ this is imparted to 

 the next truck, and so on, and we thus hear first a wave of 

 successive blows travelling along the train from the engine 

 to the last truck, and then travelling back again. 



Suppose that the chains and buffers are elastic, as with 

 passenger cars, and suppose also that there is no wheel 

 friction, while the energy expended by the locomotive is 

 just sufficient to keep it moving steadily at the velocity F, 

 in spite of the ever-increasing load ; then, when the wave 

 returning from the last car reaches the front end, the whole 

 train will be moving with a velocity 2 V. The locomotive is 

 still expending energy and will now at once acquire the 

 velocity 3F; a new wave transmitting this velocity will 

 travel to the tail end, and on its return will impart a still 

 higher velocity to the locomotive. Thus a steady pull of 

 a locomotive accelerates the train in jerks. Similarly, 

 with a gas explosion in a pipe, although the combustion 

 may be steady, the pressure ought to rise in jerks. This 

 conclusion, leading to a questioning of the second law of 

 thermodynamics, seems to have been Dr. Ritter's chief 

 objective, but he also deals with Dr. Hopkinson's theory, 

 that the pull on a wire is twice as great at the fixed end 

 as at the loose one. If Dr. Ritter's views are correct, and 

 there can be little doubt about them, the explosion of a 

 gas in a tube should be a musical note of rapidly in- 

 creasing pitch, which, under favourable conditions, might 

 be recorded in a phonograph. 



