RAILWAY CONSTRUCTION. 49 



increased temperature which expands the tyre, contracts the 

 wood, and must loosen and weaken the entire wheel. 



On all steep gradients the road-bed should be of the most 

 substantial character, and the permanent way of a strong 

 description, and maintained in perfect order, as the engines for 

 working the traffic must necessarily be of a heavy type. The 

 rails will be severely tested by the pounding and slipping of the 

 engines on the ascending journey, and by the action of the 

 brakes on the descending journey. 



In the early days of the railway system, rope-haulage was 

 adopted on -some of the main lines for working the trains on 

 steep inclines near the principal terminal stations. A. powerful 

 stationary engine, located at the highest point, was employed to 

 work an endless rope which passed round large drums at the top 

 and bottom of the incline, and was supported on sheaves or 

 pulleys fixed between the rails. The connection between the 

 carriages and endless rope was effected by means of a short piece 

 of rope called the messenger, which was coiled round the main 

 rope in such a manner as to be readily detached when the train 

 reached the summit. There are many persons who will remem- 

 ber the time when the passenger trains were hauled by an 

 endless rope up the 1 in 66 incline from Euston to Camden 

 Town, a distance of about a mile and a half, and up the 1 in 

 48 incline from Lime Street, Liverpool, to Edge Hill, a distance 

 of about a mile and a quarter, and several others. The rapid 

 strides made in locomotive construction, and the increased 

 pressure used in the boilers, enabled much more powerful engines 

 to be built, until one by one the rope-haulage machinery has 

 disappeared from nearly all the inclines where for years it had 

 been considered indispensable. Rope-haulage on inclines is now 

 very rarely met with, except at collieries and ironworks, where 

 occasionally the rope may be seen so arranged that the loaded 

 waggons descending pull up the empty waggons on the opposite 

 or parallel line. 



Curves. The degree of curvature of a railway curve is 

 generally expressed by giving the radius in feet, chains, metres, 

 or other national standard measure. 



When laying out a line of railway, the natural features of 

 the country will necessitate the introduction of curves, and the 

 question for consideration will be whether they are to be made 

 of small or large radius. In some cases sharp curves are 



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