154 REPORT — 1867. 



In planning these works, the writer, while having every regard to economy, 

 felt the importance of their being of the most substantial character, seeing 

 that they were exposed in these districts to every vicissitude of climate and 

 flood ; but indeed he feels that aU permanent public works involving the 

 safety of the lives of the community should be of undoubted stability. On 

 the whole system there are only three timber bridges, which he was forced 

 to adopt, chiefly with a view to save time, but these are very substantial of 

 their kind. All the other bridges are constructed of stone, and where iron 

 is adopted the piers are in general constructed of masonry. 



The iron work of the bridges on all these lines were constructed by Messrs. 

 Fairbairn and Sons of Manchester, for about ,£20 per ton on the average, 

 and are admirable specimens of workmanship in this department. 



Accompanying this paper, the writer furnished the working drawings of 

 fourteen of these bridges, with the sections and dimensions in detail. They 

 exhibit a variety of forms suited to the localities in which they are built. 



No. 1 is an iron-girder bridge across the Tay, 6 miles north of Dunkeld, 

 with stone abutments and pier, constructed on platforms and piles in the 

 usual way. The banks are low, and the river is spanned by two openings, 

 one of 210 feet, and the other of 141 feet. The cost of this work was 

 £20,395. Extreme length 515 feet; height above the bed of the river 

 67 feet ; cost per lineal foot £39 12s. 



Nos. 2 and 3 are the most recent bridges erected by the writer ; and here 

 he has taken advantage of the modern plan of using cylinder piers to carry 

 the girders. Both bridges are constructed in the same manner, and on the 

 same principle. The cyhnders form the piers in the centre and abutments. 

 Each cylinder is 8 feet in diameter, and has been sunk into the bed of the 

 river 27| feet in their extreme depth, by means of divers. When these cy- 

 linders were adjusted and brought to the full depth, about 3 feet of cement 

 concrete was lowered into the Taottom. On the concrete setting, the water 

 was pumped out, and the interior fiUed in vrith rubble masonry, laid with 

 Portland cement. To provide for extreme floods, two side openings were 

 made, 41 1 and 35 feet span, of plate girders, one end resting on the masoniy 

 in the cast-iron cyhnders, and the other on a stone abutment landward, secured 

 on a platform and pUes. These bridges answer their purpose very satisfactorily. 

 The cost of No. 2 bridge, which consists of two openings of 122 feet, and two 

 side openings of 35 feet span, was £11,156. Total length of No. 2 350 feet ; 

 cost per lineal foot £31 17s. Qd. ; height above the bed of the river 36 feet. 



The cost of No. 3 bridge, consisting of two openings of 137 feet span, and 

 two side openings of 41| feet span, the cylinders being sunk into the bed of 

 the river 25 feet, amounted to £13,772. Length of No. 3, 419| feet; cost 

 £32 16s. Id. per lineal foot; height above the bed of the river 49 feet. 



No. 4 is the viaduct in the Pass of Killiecrankie already alluded to. It 

 consists of 10 arches of 35 feet span, with an extreme height from the foun- 

 dations to the top of the parapet of 54 feet, and is built with a curve of 20 

 chains radius. The Pass of Killiecrankie is a well-known object of picturesque 

 beauty, and it is generally admitted that the railway, now that the slopes 

 have attained their proper verdure, has in no way diminished its attractions. 

 Indeed this viaduct is thought to give it additional interest. 1 he cost was 

 £5720. It is adapted to the single line, and is 17 feet in width over 

 parapets. Length 508 feet ; cost per lineal foot £11 5s. 



No. 5 is a viaduct across the Biver Tilt, near Blair Atliole, spanning the 

 river by one wrought-iron girder of 150 feet. The abutments are of stone, 

 laid three feet below the bed of the river on a platform of timber 6 inches 



