RAILWAY CONSTRUCTION. 79 



streams can be diverted, and the water led away to some lower 

 point without the necessity of actually crossing the railway. 

 With a large stream, where it is essential that the water should 

 be conveyed across the line and continue on its ordinary course, 

 it may be carried over in iron pipes or iron trough if there is 

 ample headway, or in iron syphon pipes where the height is not 

 sufficient. The iron pipes or trough can be supported on masonry 

 or brick piers, or cast-iron columns, the height from the rails to 

 the underside of the conduit being not less than that adopted 

 for the over-line bridges. 



Occasionally the pipes can be carried across on an over-line 

 bridge, either by placing them under the roadway or on small 

 brackets outside the parapet. 



With the syphon arrangement the iron pipes must be laid 

 down the slopes of the cutting and under the road-bed of the 

 permanent way. The pipes must be continuous, strong, and 

 firmly connected at the joints to prevent leakage. The inlet 

 and outlet ends of the pipes should be securely built into 

 receiving-tanks of masonry, brickwork, or concrete, to ensure 

 an uninterrupted flow of the stream, and also to prevent any of 

 the water from percolating through under the pipes and on to 

 the railway. As a precautionary measure, it is well to place 

 iron gratings some little distance in advance of the syphon 

 pipes to intercept and collect any brushwood, straw, or other 

 things which might be brought down with the stream. 



Fig. 73 gives an example of the syphon arrangement as 

 constructed with two cast-iron pipes placed side by side. 



Railway works carried out in cities and large towns, whether 

 they take the form of cuttings, embankments, arching, or 

 tunnels, are certain to cause a very considerable disturbance of 

 existing drains, corporation sewers, gas-pipes, water-mains and 

 underground telegraph wires. Some of these underground 

 works may be so peculiar and complicated as to necessitate a 

 slight deviation from the course originally intended for the line. 

 Suitable provision will have to be made for each of the items 

 interfered with by the railway, and the substituted work must 

 be carried out to the satisfaction of the constituted authorities 

 within the municipal boundaries. 



Bridges. Amongst the many bridges and viaducts which have 

 to be built during the making of a railway those constructed 

 over rivers and waterways are generally the most important 



