An artificial cut in the ground, supplied with water from rivers or springs, etc. in order to form a navigable communication between one place and another, and also for supplying towns with water. The advantages to be derived from canals were not unknown to the ancients. Egypt, from the remotest antiquity, contained a number of canals, dug to receive and distribute the waters of the Nile at the time of the inundation; but the most celebrated canal in that country was that which connected the Nile with the Red Sea, which was completed under the second Ptolemy, and was four days' journey in length. It was subsequently neglected, but was afterwards re-opened by one of the caliphs, in 635, after which it was again neglected, so that it is difficult to trace the remains of it at the present day. The aqueducts of the Romans were a species of canal, and they had many also for draining the water from overflowed grounds; and attempts were made (although unsuccessfully) by one of the emperors, to cut through the Isthmus which joins the Peloponnessus to Greece.
But China, in the number and extent of its canals, far exceeds all other nations, there being scarcely a town or village that is not washed by the sea or by a river, but has a canal.
The Great, or Royal Canal, is the most magnificent work of the kind in the world; it is 825 miles in length, 50 feet in width, and 9 feet deep, and extends from Canton to the northern frontiers of the empire. Most of the countries in Europe are provided with one or more works of this kind: those of Holland, from their number and the admirable mode in which they are managed, have long been the theme of travellers; but perhaps the most stupendous work of the kind is the canal of Languedoc, in France, which forms a junction between the Mediterranean and the Atlantic. It was begun in 1666, and finished in fifteen years. The breadth is 144 feet, including the towing paths; the depth is 6 feet, and the length 64 French leagues, and it has 114 locks. Although this country at the present day is superior to any nation in Europe (with perhaps the exception of Holland), in the number and magnitude of its canals, it was one of the last to adopt this important improvement; for if we except the New River Cut for supplying London with water, England, up to the middle of the last century, had not a canal worthy of notice; and the honour of their introduction is due jointly to the spirit and perseverance of the Duke of Bridgewater, and to the skill and talents of the celebrated Mr. Brindley.
The duke had at Worsley, about seven miles from Manchester, a large estate, rich in coal, which had been hitherto useless, on account of the expense of land carnage; he therefore consulted Mr. Brindley as to the practicability of forming a communication by water, who, having surveyed the ground, and declared the scheme to be practicable, the duke, in 1758, obtained an act to make a navigable cut or canal from the township of Salford, to or near Worsley Mill, and to a place called Hollens Ferry, in Lancashire; but extending his views as the work advanced, he subsequently obtained two other acts, the first to carry it over the Irwell to a place called Longford-bridge, and the second to extend it from Longford-bridge to a place on the Mersey River, called the Hempstones. The whole navigation was then proceeded in and completed, being more than 29 miles in length, and having, at its fall into the Mersey, locks which let it down 95 feet. It should be remarked that the locks were formed at Runcorn, instead of the Hempstones.
The completion of these works quickly rendering apparent the important advantages of canals to the commercial and manufacturing interests, new undertakings of the kind succeeded each other with such rapidity, that the bare enumeration of those existing at the present day would occupy more space than we could spare for the purpose. Amongst the principal are the Grand Trunk, or Staffordshire Canal, forming a communication between the Trent and the Mersey, and, consequently, between the German Ocean and the Irish Sea; the Thames and Severn; the Birmingham Canal; Peak Forest and Grand Junction, in England; and the Caledonian Canal, in Scotland. The total number of canals in Great Britain is 103; the total extent 2688 miles; and the capital sunk in their construction is computed at upwards of thirty millions sterling. With two or three exceptions, they were all constructed by the combined exertions of private individuals; and important as these works are now become, none of them were projected prior to 1755. The particular operations necessary for making artificial canals depend upon a variety of circumstances.
When the ground is naturally level and unconnected with rivers, the execution is easy, and the navigation not liable to be disturbed by floods; but when the ground rises and falls, and cannot be reduced to a level, artificial means of raising and lowering vessels must be employed. The ordinary expedients are either inclined planes or locks. The first of these methods, viz. the inclined planes, is chiefly resorted to in cases where the canal is so very scantily supplied with water that its economy becomes an object of the first importance. For this purpose, an inclined plane of masonry is constructed, extending from one level to the surface of the next above it, and the boats are hauled up the plane upon a kind of cradle or sledge, furnished with rollers, and this, it is said, was the only method employed by the ancients, who appear to have been ignorant of the nature and utility of locks. The engraving on the opposite page represents an improvement upon this method of passing boats from one level to another, by which the boats maintain their parallelism whilst ascending the inclined planes. It is the invention of Mr. J. Underhill, of Parkfield Iron Works, near Wolverhampton.
The following is a description of the engraving: a the higher level of the water of the canal; b the lower level; the bottom of the canal is a little excavated at each of these places, to admit of a kind of cradle carriage to be sunk sufficiently deep for a boat to be floated on to or off it. At c is represented a laden boat, placed upon the upper level in its carriage f f; and at d another, similarly circumstanced upon the lower level, in its carriage g g. Each of them is attached by strong chains to a dram-wheel h, properly mounted in a strong framing, and worked by a steam engine or other adequate power. The carriages are mounted upon two pairs of solid iron wheels, which run upon railways that connect the upper and lower levels. These railways form two inclined planes for the ascent of the carriage, and the same for its descent, whilst the two slopes are connected at top by a horizontal plane. This will be clearly understood by reference to the diagram. The boat c is there represented in its carriage, and ascending the double rails or planes r, the hind wheels being on the top rails, and the fore wheels on the bottom rails, but confined in their track by the parallel bars o above, which preserve the carriage from shifting out of the horizontal position.