that he can occasionally exert a much greater force than in his ordinary pace; and, far from being the worse for going occasionally uphill and downhill on moderate ascents and descents, he, on the contrary, feels a relief from the change; railways, therefore, as well as common roads, would not be the worse, but rather the better, that they were varied a little uphill and downhill, in their course from time to time; such as to the extent of 1 foot in 30 or 40. I do not say that we should go an inch out of the way to obtain this; but neither should we go a single inch out of the way to avoid it, provided that the distance so to be travelled is moderate, or not exceeding, it may be, a hundred yards or two at a time, and not occurring above twice or thrice in a mile. In a more moderate acclivity, of 1 foot in 70 or 80, the horse would not be oppressed, were the length of such to be a mile at a time, or more; it being always understood, that the horse is to be loaded in moderation, not to the utmost pitch he can move on a level; in which case he could not ascend a single foot uphill.

X. Whether railway waggons can be constructed, so as to be adapted to go occasionally on ordinary roads, or on the streets of a Town?

This does not seem to admit of much discussion. In the form, and in the mode, in which railway wheels are made, they are little fitted to encounter the roughness of an ordinary gravelled road, or the harsh nnyielding surface of a street-causeway. Who

ever will cast their eyes along the surface of either of these ways, will see so many inequalities in them, some rising above the level, and some sinking below it, that they must be convinced, that, even in those places where they are in the best order, a railwaywheel, if drawn along them, would be very liable to be either broken altogether, where made of cast-iron, or shaken out of shape, where made of wood. Even were the wheels to be made so strong as to withstand the rough usage, still the horse, in the draught, would be unable to accomplish more with them than in an ordinary cart. The advantage derived from the railway is owing to the peculiar construction (fitted to each other) of the rail and the wheels: a rough road is incompatible to these.

XI. Whether Railways can be made to suit ordinary Carts, and other Carriages?

Never till ordinary carts adopt the wheels peculiar to the railway, and which, again, are not adapted to an ordinary road.

XII. Whether, on ordinary Roads, and Streets of a Town, there might not be made a Track suitable both to Railway-waggons and ordinary Carts, and other Carriages?

This is certainly practicable to a great degree, so as to be equal, or nearly so, to the flanged railway, or where a convex-rimmed wheel rolls along a flat rail, and smooth surface. The thing is already accomplished, to a certain extent, upon one of the sides

of the common gravelled road, leading up from Glasgow to Port-Dundas. There, the road, in two particular places, was very steep, whilst lower down, it was nearly level; so that a horse could draw a lading there, that he could not draw up the hill at all; and, of course, the lading below was limited to what he could draw up the acclivity. Mr Baird, of the Shotts Ironworks, suggested a kind of railway of cast-iron, that obviated completely the difficulty, and has enabled ordinary carts now to draw, without any alteration in their structure, the same lading uphill that they can accomplish on the plain below. The device is simple. It consists merely in laying flat plates of cast-iron, in two regular lines, corresponding to the ordinary width of the wheel-track of common carts.

The ascent being 1 in 15, requires a power to overcome it more than six times what is required on

level, and yet a horse is frequently loaded with upwards of 2 tons on it, exclusive of the cart, which may be 8 or 10 cwt. more. This fact is corroborative of the theory laid down in the Table, page 77, so far as it goes.

Railways on this principle, might easily be constructed on every street, and every road; but more especially, would be highly beneficial on all steep pulls, of which there are many in the City of Edinburgh, both in the Old and New Town, as well as in other Towns and Roads in Scotland all over. these situations, one side only (the left hand ascending) would require to be laid. they are not wanted. It seems

In

Coming down-hill probable, that this

3

might be accomplished by applying smooth-stonepavement, and of course at less expence. The steepest roads at present known in Scotland, from the Cairn-a-mount in Kincardineshire, to the old Redbrae of Soutra-hill in Lauderdale, might by such means be ascended, with less labour, by carriages, than is at present required on a dead level.

XIII. Whether any mode of package would facilitate the draught?

It is well ascertained, that on carts mounted on two wheels, and having the horse in the shafts, the lading (part of which is always made to bear upon the horse's back) can be so arranged as either to promote or to retard the draught. But, on a waggon mounted on four wheels, (and in which no part of the load can be made to bear on the back of the horse), it does not seem, from previous deduction, to be possible, either to promote or retard the draught, by any mode of packing, (though it is better for the waggon itself, that the lading should be arranged equally over the whole), and from a multitude of experiments that I have made, this turns out uniformly to be the fact. Whether the load was laid altogether to the fore part, or altogether to the hind part, or piled up wholly on the middle of the waggon, there was no perceptible difference in the quantum of power, required to move it along, whether on a level or up-hill. Nay, even in a case where the fore wheels were only one-half of the height of the hind wheels, it made no odds in the draught what end

VOL. VI.

G

went foremost,-whether the low or high wheels, whether up-hill, down-hill, or on a level.*

XIV. Whether it affects the draught, that the Carriage be yoked near to the Horse, or at a distance?

There is this difference betwixt drawing close at hand, and drawing by a lengthened rope or chain at a distance, that, in the latter case, there is an effort required to bring the rope or chain to the full stretch, before the impetus of the moving power reaches to the carriage to be drawn, and this effort requires to be continually kept up, in addition to the power required simply to draw the carriage. And this seems to be more in proportion as the distance is prolonged, than that distance (numerically) should seem to require. For example, it seems to

Since writing the preceding Essay, it has occurred to me, that if, in a train of waggons, drawn by one horse, the foremost one were mounted on two wheels only, it would be quite practicable to make part of the lading bear on the horse's back; to do so, would add to the power of the horse, if done to a moderate extent; say I cwt. This would give an additional impetus to his draught, perhaps equal to all that weight itself, whilst this burden would affect, or retard, his travelling to no greater a degree than if he were mounted by a slender lad of 7 stone weight. Thus, if his ordinary exertion be equal, as supposed, to 80 lb., this weight of 112 lb. laid on his back, pretty far forward, would, without any additional exertion, (farther than as above noticed), encrease his impetus or moving power to 192; at least doubling his ordinary power, allowing part of it, as must be the fact, to be expended in carrying the hundred weight that is laid upon him.