258 



THE POPULAR EDUCATOR 



the engines and carriages. The precise width of the narrow- 

 gauge approved by Parliament for this country was determined 

 by its having been already largely used by the Stephensons in 

 the important lines constructed under their superintendence. 



Supposing a double line of railway to be required, a space of 

 6 feet known as the " six-foot way " is usually left between 

 the two lines, making a total of 16 feet, including the thickness 

 of the rails. The space left on the outer sides of the rails is 

 determined by circumstances, but the entire width of a double 

 line is usually between 28 and 37 feet. Beyond this width a 

 space is left on either side for the drainage of the line. 



The excavators having cleared away the surface earth, the 

 ballast is next laid down along the line, to form a solid road- 

 way. The ballast consists of gravel, cinders, burnt clay, 

 broken bricks, or whatever material of a similar character may 

 be most readily procured. It is generally laid 2 feet in depth, 

 1 foot or more being under the sleepers, and the rest around 

 and above them. The sleepers are blocks of sound, seasoned 

 wood, laid across the roadway at distances of about a yard 

 apart, to form a foundation and resting-place for the iron rails. 

 The sleepers are frequently formed of larch trees cut in halves, 

 and laid with the flat sides downward. Iron sleepers have 

 occasionally been employed, but their use at present is rare. 



The rails are of wrought iron, usually weighing from 70 to 80 

 pounds to the yard, and varying in shape in different lines and 

 countries. We give an illustration of the transverse sections of 

 some of the rails in most general use. The first is the rail com- 



SIDE SECTION OF IRON KAILS. 



monly used on English lines ; the second is employed in bridges, 

 and on the Great Western Railway; the third is largely used in 

 America. They are made in short lengths, carefully fastened 

 together by " fish-plates " at the sides, and are set in cast-iron 

 chairs. These chairs are affixed to the sleepers by means of 

 trenails, and when the rails are laid in the chairs, wedges of 

 compressed wood are employed to tighten them up in their 

 position ; and the space between rail and rail is carefully 

 adjusted all along the line by means of a measuring gauge. 

 The annexed cut will show the relative positions of sleepers, 

 chairs, and rails. 



RAILWAY SLEEPERS, CHAIRS, ETC. 



These particulars will be sufficient to enable our readers to 

 understand the ordinary process of making a level line of rail- 

 way. Even on a continuous level, however, great impediments 

 have occasionally to be encountered, from the varying character 

 of the soil, and the occasional difficulty of providing a secure 

 foundation for the line. We may mention as a notable instance 

 that which was successfully contended with by George Stephenson, 

 in throwing his line for the Manchester and Liverpool Railway 

 over the Lancashire bog known as Chat Moss. The ground 

 here was so soft in many places that a man stepping on it would 

 eink in, and even, in some parts, a piece of iron thrown upon it 

 would sink by its own weight ; and it was thought by many 

 persons that it would be impossible to throw a line of railway 

 across it, much less to make it safe and durable for traffic. 

 The great engineer succeeded, by throwing huge fagots or 

 hurdles across the treacherous earth, until he had secured a 

 tolerably firm basis for his operations ; and then, partly by 

 drainage, and partly by piling on more and more fagots, he at 

 last made a sound and substantial roadway. 



Where a line of country departs from the level, it becomes 

 necessary that the roadway should be raised in some places and 



1 lowered in others. This is done, when the change of level is 

 slight, by means of cuttings and embankments ; but when con- 

 siderable, tunnels, viaducts, and bridges must be constructed. 



Cuttings are excavations which form a small valley wherein 

 the line may run. Wherever it is necessary to carry the rail- 

 way below the surface of the ground, and the depth at which it 

 must run does not amount to more than from 50 to 60 feet, a 

 cutting is the means employed to effect the purpose. For a 

 greater depth than 60 feet it is usual to make a tunnel, unless 

 the line runs through solid rock or chalk, as in the case in many 

 parts of the London and Brighton Railway, where much deeper 

 cuttings may be employed with safety, and the sides may be 

 left almost perpendicular. Otherwise, cuttings are made with 

 sloping sides, which must be carefully formed, so that the earth 

 does not slip in from above. Some soils are very treacherous, 

 and the vibration produced by the passage of trains, added to 

 the disintegrating influence of weather, would soon bring the 

 upper earth down into the cutting, if the sides were not sloped 

 at a sufficient angle, and well secured. The drainage of cuttings 

 also requires attentive consideration. 



Embankments carry the line above the surface of the country 

 by an artificial roadway. They are built of earth, much broader 

 at the base than at top, to afford a secure foundation. But care 

 must be exercised to guard against the possibility of any giving 

 way of the soil below, for serious accidents have occasionally 

 been caused on embankments by the sinking of the lower strata, 

 although the engineer's work near and above the surface may 

 have been perfectly sound. 



The slopes of embankments generally have a width of 1J feet 

 horizontal to 1 foot perpendicular ; but this depends partly on 

 the material of which they are composed. Every kind of mate- 

 rial has an angle of its own called " the angle of repose" at 

 which it will remain most steady, and this has to be studied in 

 the formation of embankments and cuttings. The sides of both 

 are more durable when protected by turf, which is generally laid 

 or sown for this reason. 



As before remarked, where the inequality of the ground is so 

 great that cuttings and embankments would be impracticable, 

 the engineers have to resort to tunnels and viaducts. Probably 

 every one who will read these pages has had practical experience 

 of the nature of a tunnel, but the labour and the skill involved 

 in constructing one may not be generally known. In the first 

 place, the earth or rock has to be picked out inch by inch, and 

 foot by foot, from the hill or mountain, and close observation is 

 required to ensure that the underground workers will go without 

 deviation to the point which has to be reached on the other side. 

 Where the tunnel is of great length, two parties commence the 

 excavation from opposite ends, meeting in the centre. As the 

 hollow is formed, and the earth removed, the tunnel has to be 

 arched over and under with double brickwork, and culverts 

 must be placed under the roadway to ensure effectual drainage 

 But before all this can be done, difficulties, and even dangers, 

 must frequently be met. Sometimes they arise from the friable 

 nature of the material through which the tunnel must be exca- 

 vated, causing a frequent falling in upon the works. Sometimes 

 they are met in the form of an immense quantity of water which 

 percolates through the hill-side, or is found in the strata of 

 which the hill is partly composed. As an instance, we may 

 mention that in the construction of the Kilsby tunnel, on the 

 London and North- Western line, the quantity of water tapped 

 in its progress was so great that it was the work of eight 

 months to exhaust it, although the pumping out proceeded at 

 the rate of many hundreds of gallons per minute. 



The section of an ordinary tunnel in which two lines are laid 

 will best show the kind of work of which such a structure is 

 composed. It will be found on the previous page. 



While precipitous hills are penetrated by tunnels, correspond- 

 ing declivities are arched over by viaducts or bridges. Viaducts 

 are usually formed of brick or stone arches on which the railway 

 rests ; and sometimes, where a deep valley has to be spanned 

 over, these arches rest tier above tier, forming a double length. 

 A fine example of such a viaduct, and of the kind of country 

 these erections are constructed to traverse, is given in our illus- 

 tration, which represents the viaduct of Rigole Froide, on the 

 Semmering Railway, which unites Vienna to Trieste. 



Railway bridges over rivers and streams are now most fre- 

 quently constructed of iron ; and these, in their various forms, 

 will engage our attention in another paper. 



