507 



when required, or it may detach itself by vibration ; in the 

 first case not giving a signal, in the second not giving a 

 signal when required. 



The exhibition of a flag or a light would afford an excellent 

 means of communication if the attention of the party to 

 receive the signal could be first obtained with certainty. 



A simple mechanical contrivance for effecting a communi- 

 cation between the last carriage of the train and the engine, 

 so as to ring a bell or communicate with a steam-whistle, 

 perhaps affords the best means of attracting the attention of 

 the driver, and is the most likely to be generally adopted if 

 certain inconveniences be obviated. 



It has been proposed to make a communication by means 

 of a cord extended along the train. Such cord would be 

 liable to require too much attention to its connexions or 

 couplings when carriages are removed or added to the train ; 

 and if this objection were overcome, the lengthening and short- 

 ening of the train by the extension of the tug-rods and the 

 compression of the buffers (amounting to ten, fifteen, or even 

 twenty feet on a long train) might break the cord, give false 

 signals, or, if the cord were very slack, prevent the giving 

 a signal until a considerable length of cord had first been 

 wound up. 



It has occurred to me that the most perfect method of 

 making communications on railway trains is by the circular 

 motion of rods, extending under the carriages so as to form 

 a system of shafting, which I call torsion-rods. This I 

 propose to effect by means of rods moving in slides and 

 having springs attached, so as to extend the rods in like 

 manner as the buffers of the carriages; each set of rods 

 having a portion in the centre capable of revolving on 

 bearings attached to the framework of the carriage or 

 carriage- wheels, and connected by universal joints with the 

 sliding portion of the rods; and which revolves in, and is 



