the canal at the rate of twelve miles per hour. On this occasion eight persons and the steersman were in the gig; when a distance of two miles was accomplished with one horse in ten minutes, without any surge or agitation of the water, so as to injure the banks." p. 13.

Similar experiments were tried with twin-boats with rather better success; the only difficulty being the necessity of keeping the horse or horses in full gallop. With steam-power this difficulty would vanish. The surge was always found to diminish as the velocity increased. This was the opinion of Mr. Hunter, the proprietor of the boats, before the experiment was tried, which was a shrewd conjecture, for it appears that they had formed no idea of the principles on which these results were founded, for it is remarked:

"But whether the decrease of wave arose from the steersman of the boat, having become better acquainted with their trim in the canal, or from whatever other cause it arose, their effect was evident to every one on board."—"No danger is to be apprehended from the stoppage of the double or single boats, however suddenly, as they brought themselves up almost instantaneously." p. 15.

In some of these trials the speed amounted to fifteen miles an hour for some miles, and seemed only limited by the power of the horses. It is further remarked:

"Three different results from the above experiments are worthy of attention; first, the ease with which the boats were brought up or stopped, when moving at a high rate of velocity: second, the little additional labour in drawing, occasioned to the horse when drawing the boat at this high rate, as compared with a low rate of velocity; and third, the apparent diminution of the surge or agitation in the water at a high rate of velocity. The best explanation of these matters (continues Mr. Graham the reporter of these experiments) is by the supposition, that at a high rate of velocity the flat boat rises towards the surface, and skims over instead of cutting the water. The moment the towing line is slacked off, the boat sinks to the usual depth, and of course brings herself up immediately, owing to the increased resistance of the additional column of water, which she must cut. On the other hand when moving at a high rate, and skimming near the surface of the water, the labour of the horse is diminished in proprotion to the diminution of the column of water displaced, and the wave or surge is diminished in a like ratio." p. 17

These conjectures of Mr. Graham, however vague in themselves, are still ingenious, but they are no more than what the

* Mr. Graham means no doubt here the real diminution of the agitation of the

water.

experiment suggests. The real cause, and the real ratio or proportion in either of these cases, is not even hinted at; and Mr. Fairbairn, at the conclusion of this report, remarks:

"The diminution of wave or surge, consequent on very rapid motion through the canal, stated to have been observed by Mr. Graham, the writer of the above account, appeared very anomalous and contrary to all previous theory; and was, by many persons present at the experiment, considered as ideal." p. 18.

It is thus, that all previous theory is judged of by men who, in all probability, never studied a particle of it.

For the remaining experiments made on the Ardrossan and Paisly canal, as well as on the Forth and Clyde canal,* which are given much in detail, we must refer to the work itself. We shall, however, select one or two more from some few peculiar circumstances connected with them.

"In the month of April last, a number of experiments were made on the Forth and Clyde canal, with two gig-boats fixed together, constructed by Mr. Hunter, and thus forming what is called twin-boats. The object of these trials was to ascertain the rate of speed, at which vessels might be propelled along the canal; and the effect of a light double or twin-boat, in giving that degree of steadiness, which it was apprehended would be so much wanting in a light single boat. The only fact which it seems necessary to repeat here, is the remarkable circumstance, that the quicker the boats were propelled through the water, the less appearance there was of surge or wave on the sides of the canal. This result, so contrary to every previous theory, was doubted by several of the parties present at these experiments. The surge was, at no time, and in no instance, to any extent; and the apparent diminution of it at a high rate of velocity was supposed to be imaginary." p. 19.

It is again remarked, that

"The quicker the boat went, the more entire was the disappearance of all wave and surge, except where the water escaped in the centre of the canal, and met in two very noisy and rapid currents from each side of the boat at the rudder. This noise and rush of water was so great behind as to induce persons on board to look round, expecting to see a great wave or surge on the bank of the canal, but on the banks there was hardly a ripple. The two rapid noisy currents seemed to be completely spent and exhausted by the shock of their concourse behind the boat. Here, therefore, there was no reason to doubt of the correctness

*The Ardrossan canal is a very small barge canal, as before observed, fitted for boats of twenty-five or thirty tons burthen, while the Forth and Clyde canal is ten feet deep and of a proportional breadth. Thirty tons may average about two hundred bales of cotton.

of the reports of the Forth and Clyde canal experiments. It was not merely to be said, that the greater the speed the less the surge or wave, but was demonstrated that at a high rate of speed, surge and wave were done away with altogether." p. 22.

Another experiment, made with the Swift, a boat sixty feet long and eight feet six inches broad, twin-built, and fitted to carry from fifty to sixty passengers, is described as follows:

"On Wednesday, the 7th of July, she started from port Dundee, at sixteen minutes past nine in the morning, having on board thirty-three passengers (all men,) with their baggage. Proceeding through the Forth and Clyde canal, and Union canal, she reached Edinburgh at twenty-nine minutes past four in the afternoon. She thus made a voyage of fifty-six and a half miles in the space of seven hours and fourteen minutes. In the course of this voyage, she passed through fifteen locks, eighteen draw-bridges, a tunnel, seven hundred and fifty yards long, and over three long, narrow aqueduct-bridges, and under sixty common bridges, which carry roads over the Union canal. Her average rate of speed, during the voyage, was nearly eight miles per hour, including every stoppage."

"On the following day, viz: Thursday, the 8th of July, the Swift started from Edinburgh twenty-two minutes past nine in the morning: and returning by the same route, with thirty-three passengers (all men) and luggage, she reached Glasgow precisely at four o'clock in the afternoon, that is in six hours and thirty-eight minutes; going thus at the rate of nearly nine miles per hour.”

"On both days the weather was most unfavourable from much rain and a strong gale of wind directly in her face-the wind having been from the east on Wednesday, and from the west on Thursday. When free from the locks, tunuel, and other impediments, the speed at which she proceeded, varied from six to twelve miles an hour; and the extraordinary results of the previous experiments, made on the Paisly canal, and Forth and Clyde canal, were again completely verified, and ascertained, during her progress through one hundred and thirteen miles of canal navigation. For it appeared that when she moved through the water, at the rate of six or seven miles per hour, there was a great swell or wave constantly in her front, and she was followed by a strong surge or wave, bearing against the bank of the canal. At these times, the hauling-rope was tight and the horses appeared to be distressed; but as the speed was increased, the wave or swelling of water in her front sunk down, and when the speed came to be about nine miles per hour, the swell entirely disappeared; the waters in her front became smooth and level; the hauling-rope slackened; and the horses seemed easy, and little or no surge was to be seen on the banks behind the vessel." pp. 25, 26.

A variety of other experiments in propelling the twin-boat forward at various rates of speed, and with various weights, are detailed and described in an appendix to this work, with a plan and description of the twin-boat, and also plans and descrip

tions of other classes of steam-boats intended for the navigation of canals and the adjoining branches of the sea.

"The result of these experiments shewed, (says Mr. Fairbairn,) that the resistance to a body drawn along a line of water confined within the banks of a canal did not appear to increase in the ratio laid down in theory, and that while at a low rate of velocity, viz: at and under six miles an hour the resistance to the progress of the boat on a broad line of water, was considerably less than on a narrow line; on the contrary, at a high rate of velocity, say about ten miles an hour, the forces necessary to the propulsion of the boat on a broad and narrow line of water, appeared to be the same, if the advantage was not rather in favour of the narrow line." p. 29.

Among the experiments alluded to, Mr. Fairbairn selects those made with the twin-boat, on the Monkland canal, 12th July, 1830, (p. 61.) They are selected evidently with a view of falsifying or subverting the old, and establishing his new theory. As they exhibit distinctly his mode of calculation, we have thought proper to insert them here. We must, however, remark that his antipathy to the old theory, or his partiality for his new, does not at all diminish the importance of the results of the experiments. In this point of view, practical men will be always useful to scientific improvements. Could they, however, unite a little real theory with their experiments, they might be much more useful, from their being more skilfully conducted.

"From the averages arranged in the above, it will be observed (says Mr. F.) that the rates of velocity are to the forces as 4.8-6.2-7.2—11.6 &c. to 82-205-378-433, &c. Which are less than the squares of the velocity, at the rate of 11 and 12 miles per hour, at which time the surge is overcome, and when the boat is moved forward, unaccompanied by the heavy swell that is invariably present at a speed varying from 3 to 8 miles per hour; but this will be more clearly observed by the ratios of the squares of the velocities to the forces, as under," (or annexed.)

"If the ratios of the forces had been as the squares of the velocities, the numbers 3.5—5.4—7.1-3.2-2.8, should have been equal to each other; whereas, only the 4.8 and the 11.6 miles forces approach to that ratio; the intermediate speeds having forces above, and in an increasing ratio; and of those of 12.5 miles in a decreasing ratio.

"It appears that the force required to draw a boat of this form, 11 to 12 miles per hour, is not much increased from that of 74 miles; the increase being little more than 1-7th or 35 to 61 lbs. above 378; but horses are unfit for this purpose, as their strength decreases in a much greater proportion, than their speed increases; and, with these quick velocities, great exhaustion is produced, and a considerable portion of their muscular strength is expended in carrying themselves forward only."

Here Mr. Fairbairn gives the usual formula for horse power from theory, from which he arrives at the above conclusions, but remarks, that "if any reliance can be placed in the theorem, it shews clearly the unfitness of horses for great speed."

From the success of these experiments, it appears that Mr. F. was employed with Mr. Hunter, by the Forth and Clyde Canal Company to construct a light, twin, iron,† steam, passage-boat, to ply between Glasgow and Edinburgh, they having found, from experiment, no doubt, as well as from the theorem, that horses would not answer, when great speed is required. Here another field for research is presented to Mr. F. for he says

"The business I had now in hand was to ascertain how, and at what cost, the object which I recommended the Forth and Clyde Canal Committee to pursue, could be attained. It was not an abstract question of practicability, but how far a very high rate of velocity could be advantageously obtained; at what cost, and what might be the comparative difference of expense, between the proposed new principle, and the present mode of trackage." p. 29.

We have now given, in detail, a number of specimens, which will, no doubt, be sufficient to give a distinct view of the nature

*The formula referred to, is this, f = F(1 + w) where F represents the

whole force of the horse, when it has no velocity, W its utmost velocity when drawing nothing, u any other velocity, and f the force or effect corresponding. We shall advert to this formula in our subsequent remarks.

+ Iron, from its superior strength, and the comparative lightness of the vessels, that may be constructed by means of it, offers many advantages.