ON THE CONSTRUCTION OF THE HIGHLAND RAILWAY. 153 



to 1. This drained off the surface-water; and, after making up the holes 

 and other irregularities of the surface with turf, the space for the railway to a 

 breadth of about 15 feet was covered with two or three layers of swarded 

 or heather tuif, having the sward side of the lower layer undermost, and 

 that of the top layer up, the joints breaking band. In this way a good sus- 

 taining surface has uniformly been obtained*. On this bed of turf the 

 ballast was laid for 2 or 3 feet in depth. This was quite sufficient to support 

 the traffic, but as in some cases the bed of moss was from 20 to 30 feet in 

 depth, the railway merely floated on the surface, and was in the first instance 

 undulating, and yielded in some parts from 3 to 4 inches under the weight 

 of the engines passing over. To obviate this undulation longitudinal beams 

 of timber were tried at one place, 30 to 40 feet long, below the sleepers, but 

 this was found objectionable, as rendering it more difficult to raise or repair 

 the surface of the road ; and an additional sleeper (making the sleepers 2 

 feet 6 inches from centre to centre, instead of 3 feet) was found preferable. 

 There was nothing for it, at the worst, but to hft the road every other week 

 as it sunk, until it had acquired a soUd bearing. In many places we had to 

 lay on 4, 5, or 6 feet in depth of additional gravel, and in one place no less 

 than 27 feet, before the road became solid. In the course of two or three 

 years, however, with due attention, the rails being fished, the lines through 

 these mosses were aU that could be desired for solidity and permanence. 



As the writer has said, in crossing so many mountain-rivers, bridges of 

 magnitude had to be constructed, involving considerable varieties of execution. 

 The principal of these bridges may now be described, and any peculiarity 

 will be noticed which may have arisen during the progress of the works. It 

 will be observed that the beds of the rivers in the north of Scotland differ in 

 many respects from what is common in England, consisting frequently of 

 depths of 10 or 12 feet of gravel and boulders, the solid and compacted debris 

 of successive floods, below which, if the country is of rocky formation, there 

 is usually hard clay, and then rock, or, as in one case at the mouth of the 

 River Ness, after penetrating 12 feet of shingle and boulders, a sort of ad- 

 mixtui'e of whitish clay and sand was obtained. In some cases we had to 

 deal with soft clay and mud of great depth, but these were exceptions. Nor 

 was it possible in general to ascertain, by boring, the precise nature of the 

 foundations, because many bf the boulders in the gravel were of large size, 

 and were often mistaken for rock. The only way in which an approximate 

 knowledge of the foundations could be obtained was by driving ii-on rods at 

 various places, and, when the bed of the river admitted of it, wooden piles. 

 StUl we worked very much in the dark ; but the writer's long experience of 

 these rivers, and of the natiu-e of their floods, was of great advantage in 

 enabling him to fix the depth of the foundations and the precise description 

 of works, to secure the necessary stability of construction. In only two or 

 three cases was there any fear of sinking. What had chiefly to be guarded 

 against was sudden and impetuous floods, sometimes accompanied with 

 floating ice and trees, undermining the foundations and damaging the piers ; 

 it was therefore important to provide ample waterway. The construction of 

 these bridges ranged over twelve years, and during that time there has been 

 considerable changes in bridge building, by the adoption of iron cylinders for 

 piers, and lattice girders in spanning the waterways, so that, as the works 

 progressed, these improvements were adopted where found suitable. 



* Had this plan, whicli the writer has found to answer so well both for roads and 

 railways, been adopted in the clayey ground at Balaklava in the Crimea, a good road might 

 hare been formed. 



1867. M 



