CHAPTER XII.

ON CANALS.

THE immense capital embarked in canals, renders it a subject of very great importance, to determine their relative utility with railroads, in the transit of goods from one place to another. We shall, therefore, in the first place, endeavour to ascertain the power required to convey goods on canals, at different rates of velocity; and then, from such information as we have obtained, determine the actual cost of conveying goods and passengers, upon this description of internal communication. After which we shall compare these with the resistance, to the motive power on railways, and with the cost of conveyance, by that mode of transport.

Not having an opportunity, from our own personal observation, of ascertaining, with sufficient accuracy, the weights which a horse can drag in a boat upon a canal; we shall be obliged to have recourse to the reports of those engineers, whose practice in that line has enabled them to obtain the necessary data.

§ 1.-Experiments on the Resistance of heavy

Boats.

Mr. R. Stevenson, of Edinburgh, in his report on the Edinburgh railway, in 1818, states, “upon the canals in England, a boat of thirty tons burden is, generally, tracked by one horse, and navigated by two men and a boy; on a level railway it may be concluded, that a good horse, managed by a man or lad, will work with eight tons. At this rate, the work performed on a railway by one man and a horse, is more than in proportion

of one third of the work done upon the canal, by three persons and a horse;" and Mr. Stevenson, in his calculations, afterwards, assumes the power of a horse of a horse upon a good railway equal to ten tons.

Mr. Sylvester, in his report on the Liverpool and Manchester railway, gives twenty tons as the performance of a horse upon a canal, travelling at the rate of two miles an hour.

The variation between these two statements, may have arisen from the observations being made on canals of different widths. Mr. Stevenson, in another report, states, that the striking difference between the draught of horses, on coming out of a narrow canal into a more capacious one, induced the reporter to give the subject particular attention; and by means of experiments made with the dynamometer, so far as he had an opportunity of carrying the experiments into effect, the difference appeared to be at least one fifth in favour of the great canal.

We have been favoured by Mr. Bevan with some experiments and observations on the force of traction, with different loads and velocities, on canals.

In these experiments, the resistance was ascertained by a spring dynamometer, attached to the towing-rope. The length of the boat was 69.5 feet, breadth 6·92 feet. The correct transverse section of the canal was not obtained, but was from 90 to 100 feet; the immersed part of the boat being about nineteen feet, or one fifth of the channel.

The force of traction, required to move this boat, loaded with 23.77 tons, at a mean velocity of 2.45 miles an hour, was, on an average, of fifty-four observations, 79.5 lbs., which is equal to three pounds and a half per ton of useful load. With this load, Mr. Bevan remarks, one horse generally travelled twenty-six miles and a half

a day; which would give the effect of a horse, 2106 lbs. moved one mile per day.

The same gentleman has also favoured us with the following experiments, made on the Grand Junction canal at Paddington :

Transverse section of canal

Loaded boat

142 feet.

17.2 feet.

A weight of 72 lbs., acting over a pulley, drew the empty boat at the rate of 3.45 miles an hour.

A weight of 77 lbs., acting in a similar way produced a medium velocity of 2.5 miles an hour, when the boat was loaded with twenty-one tons of cast iron. And all circumstances the same as in the last experiment, it required a weight of 308 lbs. to produce a mean velocity of 3.83 miles an hour.

Mr. Bevan adds, "the length of the towing-line may be considered ninety-eight feet, and the mean distance of the boat from the towing path twenty feet." From this experiment, considering that the canal in that part was of greater area than it is upon an average, it may be inferred, that to maintain a velocity of four miles an hour, with a loaded boat, it would require the aid of four horses, provided the safety of the banks would allow; but, as the canal is now formed, it would not be capable of withstanding the waste produced by such a velocity.

Mr. Chapman, (Canal Navigation, page 73,) states, that he observed a boat, eight feet width of floor, ten feet width of water line, fifty feet extreme length, loaded with fourteen tons, and drawing 2.25 feet water, dragged against a stream, the velocity of which was five miles and a half an hour, with twenty-eight trackers, and three men in the boat, pulling it on, and yet it did not advance more than a quarter of a mile an

Mr. Smeaton's estimate was twenty-two tons burthen, from two to two miles and a half an hour, with one horse.

Mr. James Walker, of London, made some experiments in the London Docks, on the relative resistances, at different velocities, the result of which he communicated to the Royal Society, (May 31st 1827,) which being very conclusive, and conducted with great care, we give an abstract of them. (Note S. Appendix.) The result of these experiments was, that the resistance increased in a greater proportion, than the duplicate ratio of the velocities. The respective resistances being as follow:

Mr. Palmer gives, in the first volume of the Transactions of the Civil Engineers, an account of experiments made on the resistance of canal boats in different canals, and dragged at different velocities, which having been conducted on a large scale, are valuable. The following Table shews the result of these experiments.