The Union and Monkland Canals.
There are two canals that are in the same locality as the Forth and Clyde, already alluded to, but of greatly subordinate importance. The Monkland serves the important iron and coal mining and manufacturing districts in the West, of which Airdrie and Coatbridge are the principal centres, and gives access therefrom to the Clyde. The Union Canal is really a feeder to, and branch of, the Forth and Clyde Canal, some distance further east.
The Union Canal joins the Forth and Clyde Canal near Falkirk, and stretches thence to Edinburgh, being 31½ miles in length. It is 40 feet wide at the top, 20 at the bottom, and 5 deep, It was completed in 1822, but has been, in all respects, a most unprofitable undertaking. For many years the proprietors have not received any dividend, and their prospects, we understand, are not improving.
A canal intended to form a communication between Glasgow, Paisley, and Ardrossan was commenced in 1807, but only that portion connecting Glasgow with Paisley and the village of Johnston has hitherto been finished. This part is about 12½ miles long, the canal being 30 feet broad at top, 18 at bottom, and 4½ deep. It was here that the important experiments were originally made on quick travelling by canals, which demonstrated that it was practicable to impel a properly constructed boat, carrying passengers and goods, along a canal at the rate of 9 or 10 miles an hour, without injury to the banks.
The Caledonian Canal.
A valley remarkable for its uniformity, straightness, and depth, and extending from sea to sea, between two parallel ranges of steep mountains, divides the Highlands of Scotland into two nearly equal parts. The general direction of this chasm is from north-east to south-west, making an angle of about 35 degrees with the meridian; and, besides being entered at each extremity by an arm of the sea, viz., by the Moray Firth on the north, and Loch Linnhe on the south, the rest of its bottom is for the most part occupied by a series of rivers and lakes. The remarkably elongated form and contiguity of these lakes had long ago suggested the facility of forming an inland communication between the Atlantic Ocean and the German Sea. In order to accomplish this important object, it seemed sufficient to connect these lakes and the firths by several short canals amounting together to 23 miles, and thereby obtain a navigable line to an extent of more than 100 miles; and this was farther recommended by the summit-level only rising 94½ feet above the sea.
So far back as the year 1773, this line had been surveyed by James Watt, who reported favourably of it, and proposed that the lakes should be connected by a canal of a very moderate size. Nothing further, however, was done till early in the present century, when the subject was taken up by Government, and new surveys were made by Messrs. Jessop and Telford, who recommended a canal of such dimensions as should admit frigates of thirty-two guns, and the greater part of merchant ships, particularly that class which trade between the Baltic and the ports of Ireland and the west coast of Britain; thus avoiding, it was hoped, a tedious, and often dangerous navigation by the Orkneys. The dimensions proposed by Telford, and mainly adhered to, were a width of 50 feet at bottom, 120 feet at top, and 20 feet deep; the locks from 170 to 180 feet long, and 40 wide, with a depth of 20 feet of water besides the lift, or rise. The canal has, however, only been excavated to the depth of 15 feet in the summit-level, though the width has been increased to 122 feet at the top, with such a break in the slope that there is on each side a horizontal shelf 6 feet broad at the depth of 2 feet under the surface of the water. The design in this break in the slope of the sides is to keep large vessels from approaching too close to the edge of the canal, and destroying the upper part of the banks, either by contact or by the eddy produced between the vessel and the sides of the canal. On the north, the Caledonian Canal commences with a sea lock at Clach-na-Carry, in a sheltered bay of Loch Beauly, which is the more inland part of the Moray Firth. The sea-lock here is about two miles north-west of Inverness, and three-quarters of a mile west of the Ferry of Kessock, which is near the mouth of the river Ness. In order to have sufficient depth of water at ordinary neap-tides, it was necessary, on account of the flatness of the shore, to place this lock 400 yards within sea-water mark, an operation attended with difficulty on account of the softness of the bottom. This lock is 170 feet long, 40 wide, with a lift of 8½ feet; and proceeding from it, the canal is formed by embankments till it passes the sea-mark, where another lock of the same size, with a lift of 6 feet, is built on firm ground. On the south of this is the Muirton basin, 967 yards long and 162 yards broad, with a wharf for the trade in that quarter, being about a mile from Inverness. At the southern extremity of this basin is a swivel or swing bridge for the public road between Beauly and Inverness; and then four locks, which, however, from their being connected, have only five double gates in the whole. These raise the canal 32 feet, which puts it on the ordinary summer level of Loch Ness. Each lock is 180 feet between the gates, and 40 feet wide. The canal thence proceeds until it meets, and runs along the north-west bank of the river Ness to the small lake Doughfour, which is about 2100 yards long, and from 5 to 9 fathoms deep, and is 6½ miles from Clach-na-Carry. It communicates with Loch Ness by the pass of Bona Ferry. The intended line of canal being on the west side of the river Ness, which in three different places approached close to the steep sides of the hills on the west, it was necessary to alter the course of that river, so as to obtain room for the canal without cutting into the hills. At the entrance to Loch Doughfour is a regulating, or guard-lock, without any lift, to prevent any overflow from the lake. It is 170 feet long, and 40 wide. It was necessary to deepen this small lock in several places by dredging, and to raise it 6 feet to the level of Loch Ness by a weir, and embankment. The next part of this navigation, and by far the most extensive lake in it, is Loch Ness, a fine sheet of water about 24 miles long, and from 1 to 1½ miles broad. Its depth is so great that it never freezes, being from 5 to 129 fathoms, and along the middle it averages 100. It affords good anchorage at each end, and also in a few bays, although the sides of this lake are generally straight. It was proposed to introduce buoys for more convenient moorings. There are nowhere in it either rocks or banks detached from the shore.
Loch Ness receives the river Oich in its western shore not far from its southern extremity, and a little south of this the canal leaves the lake, whilst almost quite at the southern end stand the fort and village of Fort Augustus. From this the canal ascends 40 feet by five locks, and at Callachie, about 2½ miles further on, it rises 8 feet by another lock. Three miles more bring it to Loch Oich, where a regulating lock raises it 30 inches, so as to be even with that lake, which is on the summit level.
To obtain a proper line for the canal upon the south-east side of the river Oich, the channel of that river has been somewhat altered. Loch Oich, which forms the summit-level of this navigation, is about 3¾ miles long, and on an average a quarter of a mile broad. In one place in the middle, and at both ends, it had to be deepened by dredging. The water which falls into this lake, particularly from the river Garry, affords at all times an ample supply for the canal. Between Loch Oich and the next lake in the line, Loch Lochy, there is no natural communication. The interval is about 1¾ miles, and rises 20 feet above the Loch Oich, which, with the depth of the canal, required a cutting of 35 feet. Loch Lochy, which was 21 feet 9 inches lower than Loch Oich, has been raised about 12 feet by an embankment to avoid rock-cutting, and the canal descends to it 9 feet 9 inches by two locks, one of which is also a regulating, or guard lock. Loch Lochy is 10 miles long, and averages one in breadth. In some places it is 76 fathoms in depth. About half a mile of the course of the river Lochy had to be shifted into a new bed to make room for the canal, which, now in its last stage, proceeds from the lake for 8 miles along the north-west bank of that river over a rugged surface to the shore of Loch Eil, which is the more inland part of the Firth, called Loch Linnhe. A little south of Loch Lochy there is a regulating lock; and about a mile from Loch Eil there are eight connected locks, called Neptune’s Stairs, by which the canal descends 64 feet. At Corpach shore it falls 15 feet by two locks, and, after expanding into a basin 250 yards long and 100 broad, it finally descends 7 feet 9 inches by the sea-lock into Loch Eil near Fort William.
The entire length of this navigation is 60½ miles, and that of the artificial part, including Loch Doughfour, is 23 miles. There are in all twenty-eight locks. This canal has, as yet, been a most unprofitable speculation, not even paying the expense of its maintenance.