Waterways and Water Transport in Different Countries / With a description of the Panama, Suez, Manchester, Nicaraguan, and other canals.

by J. Stephen Jeans

At Walkden Moor, an underground plane was completed in October 1797, upon the Bridgwater Canal, similar to the Ketley plane above described.

Reynolds introduced another form of inclined plane on the Shropshire Canal, where there were three planes employed of 120, 126, and 207 feet rises. The Act for this canal was obtained in 1788, and it was completed and opened in 1792. These planes were of the same construction as those at Ketley, except that there were no locks at the top of the descending planes, but the latter were continued above the surface of the water in the upper canal and terminated in a cross beam, from which another plane and railway descended into the upper canal, this being intended to avoid the waste of water which locks at the top of the planes occasion.

The first incline up which barges were conveyed in a large caisson containing water was at Blackhill, on the Monkland Canal, near Glasgow, the system having been previously introduced, on a small scale, on the Chard Canal in Somersetshire. The Blackhill incline, with a rise of 96 feet, and a gradient of 1 in 10, replaced two flights of four locks each. The wrought-iron caisson, 70 feet long, and 13⅓ feet wide, runs on twenty wheels, and carries barges of 60 tons on the incline. An incline with larger caissons was constructed at Georgetown in 1876, in substitution for two locks connecting the Chesapeake and Ohio Canal with the Potomac. This incline rises 39 feet, with a gradient of 1 in 12; and barges of 115 tons are transferred from the lower to the upper reach in 8 or 10 minutes. The caisson is 112 feet long, 16¾ feet wide, and 7⅚ feet high. It is carried on three trucks, with twelve wheels each, and is drawn up by wire cables worked by a turbine.

A canal incline, as described by Mr. Vernon-Harcourt,[275] consists of two lines of way, laid on a steep uniform gradient, on which barges are drawn up or let down, by wire cables, from one reach to the next, either resting on a cradle, or water-borne, in a caisson, running on wheels on the incline. The cables wind round a drum at the top of the incline; and the ascending barge is generally more or less counterbalanced by another descending, whereby the tractive force required to pull the barge up is considerably reduced. Primitive inclines exist on the Bude Canal in Cornwall. Inclines are often used, as alternatives to locks, as at Hampton Court, on the Thames. Inclines, up which barges are drawn in cradles, were carried out on the most extensive scale on the Morris Canal in America, where there are twenty-three inclines with gradients of 1 in 10, and an average lift of 58 feet. The largest of these is 1100 feet long, and rises 100 feet; and barges of 70 tons are drawn up the inclines.

Locks.

In the great majority of cases, however, locks are the means adopted for overcoming differences of level. In Great Britain it is calculated that on the existing canal system of 2240 miles, there are 1901 locks, being at the rate of one lock to every 1·37 miles of canal, of which 931, or nearly one-half, are 80 feet long or more.[276] This, of course, means very slow transport and great loss of time. On the canal system between Birmingham and London there are about 130 locks in all.

The loss of time due to the passage of locks arises from two causes, one of which, as Mr. Conder points out,[277] it is easy to calculate, while the other varies extremely according to the management of the line, and the nature and volume of the traffic. The rise or fall of the water in the lock occupies an ascertainable time, ranging from three to six minutes; but the time lost in entering and leaving the locks is less easy to calculate. With perfect arrangement the loss is very small; frequently it is, in fact, very considerable. “In the event of a heavy traffic being thrown on our canals, it will probably be advisable to double the locks, a communication being made practicable between the pair, in order to save half a lock full of water at each passage. With this arrangement much time as well as much water may be saved. The average retardation due to the hydraulic requirements alone of the locks on the English canals is from 1¾ to 2 minutes per mile, the average rise to be overcome being under 6 feet per mile of canal.”

In France, on all the more important canal routes, the locks are designed to accommodate the large péniches or boats of 270 tons burden, 116 feet long, and 16 feet beam, which are the usual craft employed. In cases of exceptional traffic, the locks are made 130 yards long by 13 yards wide, in order to allow of several vessels passing through together. These arrangements are very favourable to the transport of large quantities of freight, so much so, that it is no unusual thing to see 25 to 30 barges, each laden with 270 tons of coal, towed by a small tug of 20 horse-power, working a submerged chain or wire rope, which the tug raises from the bottom as it progresses, the rope being nipped between revolving pulleys.

The time occupied in passing through a lock on the French canals used to amount to from 16 to 20 minutes at least. The time is spent in filling or emptying the lock, in closing and opening the lock-gates, and in passing the barge into and out of the lock-chamber. The adjustment of the water-level in the lock-chamber may be hastened by large sluices in the side walls of the lock. The moving of the lock-gates can be rapidly effected by hydraulic machinery. Delays have been experienced in dragging a barge into or out of the lock when it is nearly the width of the lock-chamber, owing to its acting like a piston, and preventing the flowing back of the water along the sides; but this inconvenience can be obviated by carrying the culverts for the sluiceways all along the side walls, and providing lateral openings through which the water finds an exit.

The dimensions of the canal locks resolved upon in France, under the extension scheme of 1878, was 126·2 feet in length by 17 feet in clear width, and 6·56 feet of water on the sill of the lock-gate. Boats of 120 tons burden can make use of such locks without difficulty. No canal in England, except the Gloucester and Berkeley, has locks of this size. The nearest approach to such dimensions is that made by the Grand Junction Canal, with locks 87 feet 6 inches long, 15 feet in the clear, and a depth of 5 feet, allowing, however, for the passage of an 80-ton boat only. The Grand Union Canal, which is connected with the Grand Junction, has only locks of 78 feet by 7 feet 2 inches. It has been computed that the difference between the cost of locks for a 120-ton boat and that of locks suited for an 80-ton boat is not more than 3000l. per mile.[278] Assuming the accuracy of this figure, the cost of enlarging the dimensions of the principal British canals ought not to be a serious item.