The iron work of the bridges on all these lines were constructed by Messrs Falkiner of Manchester, for about £30 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 details. They exhibit a variety of forms suited to the localities in which they are built.

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 foundations 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 attractiveness. Indeed this viaduct is thought to give it additional interest. The cost was £5,720. It is adapted to the single line, and is 17 feet in width over parapets. Length 508 feet; cost per lineal feet £11. 5. 0.

No. 5 is a viaduct across the River Tilt, near Blair Atholl, 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 thick secured to piles. As it is situated close to Blair Castle, it has been made somewhat more ornate than was otherwise necessary. The cost of this bridge is £6,500, being for a single line. Length 256 feet; cost £25. 7. 9d. per lineal feet.

No. 13 is a good example of a swing bridge built across the Caledonian Canal, which the line spans on a skew of 65 degrees. It consists of 2 girders of 126 feet in length, 78 feet of which, from the centre of the turntable, spans the canal, and the remaining 48 feet forms the balance weight. Advantage was taken of the canal being emptied for repairs to lay the foundations of the masonry, which are on a platform and piles in the solid gravel, 9 feet below the surface of the water. The depth of the canal is 18 feet and the width of the locks 40 feet, the canal banks being 130 feet apart. Some difficulty occurred at first during hot weather from the expansion of the iron affecting the adjustment and closing of the bridge, which was remedied by means of a powerful screw, and the bridge has been worked with satisfaction and safety for the last five years. This bridge, with its machinery, timber, wharves for protection from vessels, distant and station signals, &c. complete, cost £4,718.

There are many other bridges, so may be supposed, over so great an extent of country, and a country so much exposed to floods, but those above described are the principal; the entire waterway spanned over the entire system being 9828 feet.

On the Central Railway from Dunkeld to Forres, 104 miles, being a single line, there are 8 viaducts, 126 bridges over streams, 119 public and accommodation road-bridges, and 8100 yards of covered drains, varying in size from 18 to 36 inches square. There are 1650 lineal yards of breastwalls, 304,700 cubic yards of rock cutting and 3,416,000 cubic yards of earthworks, being including rock and earth, at the rate of 35,776 cubic yards to the mile. The largest embankment was at Refford near Forres, which contained 208,000 cubic yards.

The permanent way consists of larch and natural-grown Scotch fir sleepers of the usual size, 3 feet apart; the chairs are 22 lbs. In weight; the rails weigh 75 lbs. to the lineal yard, are in lengths of 24 feet, and are fished at the joints.

The total cost of the works, including all extra and accommodation works, amounted for the 104 miles to £798,311; and the land including severance to £79,000; and the preliminary Parliamentary, Engineering, and law expenses to £50,893, making the cost of this portion of the Company's lines £919,204, or £8.860 per mile. The extra work claimed by one contractor is still unsettled, but is valued and paid at the rate at which the extra works on 160 miles of this system of railways have been amicably settled.

The contracts were entered into immediately after the passing of the Bill in July 1861; the first turf of the railway was cut out on the 17th of October of the same year, and the whole line was passed by the Government Inspector, and opened for Traffic on the 9th of September, 1863, being one year and ten months, and unprecedentedly short time for works of such magnitude. The works between Forres and Dunkeld were divided into nine contracts let by public competition, and were completed at 18 per cent over the Engineer's estimate, including 4 per cent for accommodation works ordered by land valuators.

The traffic has been worked successfully and without accident for four years. The mail trains perform the journey between Inverness and Perth (144 miles) in 5½ hours. It was proposed to Post Office, but not agreed to, on account of the expense, to run them in four hours.

An ordinary goods train of 20 wagons, or 200 tons gross load, is drawn up the steepest inclines by one engine, having 17-inch cylinders and 24-inch stroke.

The traffic rapidly increasing. The sheep and cattle which used to reach the southern markets by a toilsome journey of a month or six weeks, are now conveniently transported in a day at less cost, the Company having carried in one week upwards of 21,000 sheep.

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