However

roadway on which the carriage runs. much, therefore, some may consider as questionable the supposed advantages of rails laid on continuous bearings, the defect, if any, cannot appertain to the principle, which, the more it is examined, will carry the more conviction with it; but it must appertain to the details of the construction. For instance, on some railways with continuous bearings, the rails are fastened into chairs, and rest upon intermediate saddles.

When the iron rails are laid down, however, in this manner, the tension and elasticity of the bar-bound at intervals, like the strings upon the bridge of a violin-are not removed; in fact, there is no difference in the principle from rails laid upon cross sleepers: and it may fairly be admitted, that rails so laid upon longitudinal sleepers are inferior, in many respects, which could be pointed out, to rails laid upon transverse sleepers.

It should therefore be kept closely in view, that when a railway is said to be laid on continuous bearings, it is meant that the base of the rails rests entirely upon the solid timber. It has been shown that the old tram-road, first used in this country, was nothing but continuous logs of wood, with cross ties, adapted to the width of the carriage-wheels. When this system was intro

duced in America, where, from convenience, it has been extensively adopted, it was farther improved, rendering it more adapted for steam power; and on the Continent some railways have been similarly constructed. The introduction of this form of railway in America has been attributed to the abundance of timber, an advantage which this country does not possess: but the question which the public are most interested in, is not, where the material comes from, or even the cost of it, but what is really the best plan.

One of the first engineers who has made the attempt to introduce into this country a railway on the American construction, but with iron edge-rails, was Mr. I. K. Brunel, who did so on the Great Western railway; and it required both courage and ability to attempt an entire alteration in the railway system which had for several years previously worked so well; and perhaps few engineers would have attempted the bold experiment at once, which he did, of constructing so many miles of a railway differing so much in detail from the method of laying the rails previously in general use. The principle is therefore deserving of most careful consideration; for if it ultimately turn out, by successive future improvements, as successful as it has already proved,

this form of continuous railway may supersede the common mode of construction, and perhaps lead to the remodelling of many railways now in existence.

It is generally understood that the objects which Mr. Brunel sought to attain, in proposing a railway on the American construction in this country, was, that while it could be made at no more expense than on the common method, it might be cheaper maintained, and much more agreeable to travel over, as there would be less concussion and jolting, and a smooth, equal, and elastic road, without any undue yielding; in fact, that though there would be a less unyielding surface to pass over, than on rails laid on stone blocks, there would be sufficient firmness for safety, and less liability to the parallelism of the rails being disturbed, while both vertical and lateral deflection of the rails would be diminished.

That he has not been disappointed in his surmises, in many of the points, can be disputed by few that his views were not fully realised in the construction of this railway, arises from the inexperience which surrounds so many points of an infant science. It may be objected, that a fair comparison cannot be drawn between the Great Western, from its great breadth, and common

railways: but there are other lines in this country, of the common gauge, laid with continuous bearings, by which a comparison can be made.

Before proceeding to describe the manner of laying the sleepers on the Great Western railway, it is necessary to notice the form of the iron rail which Mr. Brunel adopted, as it differs entirely from those previously described, requiring neither cast-iron chairs nor wedges. It is the more necessary to understand the construction of the rail, as on the stability of the rail, and its proper adaption to the road, much of the safety of carriages running at high velocities will depend.

Fig. 31. is the form of rail which was first laid

Fig. 31.

down on the Great

Western. It consisted of

a hollow malleable iron bar, made in 15-feet

lengths, having two broad flanches perforated at intervals of 16 inches, for admitting the screwbolts for fixing the rail to the timbers; the outer bolt having the head raised above the flanch, and the head of the inner bolt being counter-sunk or flush with the iron: the original rails were only 44 lbs. to the yard, and were 14 inch high. This form of rail is termed the bridge or hogtroughed rail.

LONGITUDINAL SLEEPERS, OR BEARINGS, ON THE GREAT WESTERN.

As the plan which Mr. Brunel has adopted for the sleepers or frame-work of the Great Western, as now arranged, does not differ greatly from the American railways, and others which have been laid in this country, it will easily be understood. It may, however, be instructive to describe the first plan of forming the line of way laid down from London to Maidenhead, 22 miles; but which is now in the course of being entirely altered. On this part of the line Mr. Brunel made use of piles driven at intervals, in order to give greater security to the continuous timbers, so that they might not rise up or go down; but these piles have been found to be unnecessary, and so to add much to the cost of the railway, without any corresponding advantages: they are therefore now being entirely removed, and longitudinal timbers of greater scantling substituted.

Fig. 32. is a transverse section of a pile driven into an embankment.

In forming the railway, when the road was constructed, beech piles, 10 inches in diameter,