RAILWAY CONSTRUCTION. 195 



equal in effect to the falling-weight test. The rails form such 

 an important part of the trackway, almost the very basis on 

 which the traffic has to depend for its safety, that, apart from the 

 question of wear, no effort should be spared to ensure their 

 thorough soundness and efficiency. 



In modern practice rails are generally used in lengths vary- 

 ing from 25 feet to 30 feet. There is no difficulty in making 

 them longer ; but any excess over the above lengths is found to 

 be inconvenient for transport, for handling in the line, and for 

 making the necessary allowance for contraction and expansion 

 at the joints. Steel rails are generally marked on the vertical 

 web with the initials of the railway company, the name of the 

 manufacturer, and the year in which they are rolled. This is 

 done by cutting out the letters in the last pair of rolls through 

 which the rails have to pass before they are completed, so that on 

 the rails themselves the letters stand out in raised characters, 



thus: G.N.R.I C. CAMMELL & CS 1896. In this 



manner the rails always carry for reference the name of maker 

 and date. 



When comparing the relative merits of the flange -rail and 

 bull-head-rail permanent way, the question of strength and 

 durability must be considered, as well as that of economy. The 

 flange-rail road has undoubtedly fewer parts and fastenings, and 

 when the flange is wide, the sleepers sound, and the rail securely 

 held down to the sleepers, the result is a smooth running road. 

 So long as the rail can be maintained in a constant close contact 

 with the wooden sleeper, the running is almost noiseless, the 

 jarring on the rails being absorbed or taken off by the timber ; 

 but so soon as a little space or play takes place between the 

 spikes or other fastenings and the upper surface of the flange, 

 the rail obtains a certain amount of rise, or lift, which comes into 

 action upon the passing of every rolling load, producing un- 

 steadiness in the rail and a clattering noise in the running. A 

 flange of 5 inches, on a sleeper 10 inches wide, has a bearing 

 surface of 50 square inches (assuming the sleeper to be square 

 cut, without any wane on the edges), and this area of 50 inches 

 is only about half of the bearing surface on the sleeper of an 

 ordinary modern cast-iron chair. 



Main-line locomotives have weights on the driving-wheels 

 varying from 16 to 18 and 20 tons. Taking 18 tons as repre- 

 senting a common practice for a large express engine, would 



