1869,] Engineering — Civil and Mechanical. 283 



no heavy works for construction, tlie gradients nowliere exceeding 

 1 in 60, and there being no curve of less than 30 chains radius. 

 Whilst the possibihty of working steep gradient lines is thus clearly 

 proved, there can be no doubt with reference to their greater 

 economy in construction ; with our present advancement of know- 

 ledge, however, a gradient of 1 in 40 is probably the steepest that 

 should be allowed when practicable, and coupled engines only should 

 be employed, of as great weight as can be obtained, and having 

 a good long wheel base. 



Under the provisions of an Act of Parliament passed last 

 session, all trains running distances of twenty miles and more, 

 without stopping, must, after the present month (April), be sup- 

 phed with some sufficient means of in tercom m unication between 

 passengers and guards. With a view to test the different means 

 for accomplishing this object, some experimental trips were under- 

 taken on the line between York and Scarborough at the latter end 

 of November last, and on the London, Chatham, and Dover Rail- 

 way, between London and Sevenoaks, during the following week. 

 Three systems have been proposed for the purpose, viz. — 1. The 

 rope pulls, which is the oldest of them all. 2. The electrical sig- 

 nalling system, of which there are many varieties, and some of 

 them have already been in use for a length of time on the various 

 lines of railways. And 3. The pneumatic system, which, whilst 

 it is the newest, is also in many respects the most efficient. Space 

 will not admit of our giving a detailed description of the several 

 systems that were submitted to trial. The principle of the rope 

 and electric bell systems will probably be well known to most of our 

 readers, and we shall not therefore make further reference to them 

 here. The pneumatic system, being novel, may, however, fairly 

 claim a brief notice. The signalhng apparatus consists of a heavy 

 gong upon the engine or tender, and a smaller one in the guard's 

 van. Both these gongs are struck by hammers, which receive 

 direct motion from the train, when a signal is given. When no 

 signal is passed from passengers or others, these hannuers are kept 

 away from the gongs, and they are put into gear in the following 

 manner. A tube runs along the whole train, beginning at a pump 

 in the tender, passing from carriage to carriage, and ending in a 

 plug at the back of the train. This pipe, which is worked by 

 the machine, keeps pumping the air out of the pump, and sustains 

 in it a partial vacuum. Underneath those vehicles, which are 

 supplied with gongs, there are shallow cylinders in connection with 

 the vacuum-tube, from which the air being exhausted, their pistons 

 are drawn backwards, and pull thereby the striking portions of the 

 bells out of gear. Over each compartment a T-piece is inserted in 

 the tube, and a plug is fitted into its lower stem so as to keep the 

 tube air-tight. The passengers give signals by pulling out these 



