Gravel and sand were swept away by the rapids at the wiers, and deposited in banks and shoals in the ponds below. During floods, the works were overtopped by the water, and frequently injured; and the crooked navigation, with the trackage against the stream, was at all times laborious and dilatory. These difficulties suggested the propriety of leaving the natural bed of the river, and led to the formation of a separate cut, with pond-locks. The first work of this kind, was the Sankey Canal, in Lancashire, which was quickly followed by a far more bold and extensive enterprise, by the Duke of Bridgewater, in the same county. This spirited nobleman, having found in Mr Brinley an ingenious projector, crossed streams, embanked valleys, and bored through mountains; and thus completed a work which was at first pronounced impracticable, but the success of which, notwithstanding so many natural obstacles, gave a wonderful impulse to the system. A generation had not passed away, after this important operation was completed, till between two and three thousand miles of canal navigation had been constructed in England alone, constituting an aggregate of inland navigation, not to be equalled in the world; in the construction of which, all kinds of difficulties had been experienced, and had been overcome by the talents and perseverance of an ingenious and industrious nation.

Under the present head, my main object is to notice the architectural skill, which this branch of improvement has called forth; and I shall therefore confine myself to the notice of aqueducts, which, in some situations, form the most difficult part of the art, as connected with the construction of canals. When the course of a canal crosses that of a river, it becomes necessary to build a bridge, and, upon it, in place of a common road, to form a channel and towing-path for the canal; the height of the aqueduct being regulated by the relative levels of the river and canal, and its breadth by that of the canal. Most works of this kind differ little from that of a

road-bridge of similar dimensions. But, about the year 1795, Mr Telford, having been entrusted with the management of the Shrewsbury and Ellesmere Canals, had his attention drawn to the construction of some large aqueducts; and having observed, in several instances, the masonry of aqueducts, where puddle was employed, to be cracked, and very subject to leakage, was led, by these circumstances, to employ cast-iron work in forming the bed of the canal. This he did, in the first instance, upon the Ellesmere Canal, at Crick, where the aqueduct was six hundred feet long, and sixty-five feet high above the river. Here he rejected the method of puddling; built the spandrels over the arches, with longitudinal walls only; and across these walls laid flaunched plates of cast-iron, as a bottom to the canal, and the means of bending the walls horizontally. These were well jointed, screwed, and caulked; while the sides of the water channel were built of stone facings, and brick hearting, laid in water-lime mortar. By this mode, the quantity of masonry was much reduced, and the purpose, at the same time, effectually secured.

On the same canal, it was found necessary to cross the river Dee, at the bottom of the fine valley of Llangollen, at Pontcysylte, at the height of nearly a hundred and thirty feet above the surface of the river, and for a thousand feet in length. In this stupendous work, Mr Telford introduced a still more decided deviation from the usual form, by building upright piers only, and, instead of arches of masonry, placing cast-iron ribs between them, constructing the canal part by cast-iron flaunched plates, for the sides as well as the bottom; and, in order to preserve as much as possible of water-way, projecting the towing-path over the water in the canal. The canal part is twelve feet in width, which admits boats of seven feet beam, and a towing-path. Where the embankment commences, the height is seventy-five feet, and it is carried, on both sides, to an extent amounting in all to fifteen hundred feet.

This is the greatest aqueduct and embankment ever made for a navigable canal. Other works of the same kind, however, have since been constructed, of great magnificence, among which I may mention the three aqueducts erected on the Edinburgh and Glasgow Union Canal, in which the modes of the two aqueducts already mentioned have been combined; that is to say, the masonry of the arches and spandrels are finished as at Crick, and cast-iron plates for the bottom and sides, as in Pontcysylte, are introduced within the masonry. An improvement is made in the piers, by forming them hollow throughout; which mode, with an equal quantity of masonry, embraces a greater extent of base, and, having more external, as well as internal, surface, insures better materials and workmanship.

It is probable, that the art of canal-making has now arrived at its climax, being about to be superseded by an improvement of vast importance,-that of locomotive engines on railways; but the necessity of aqueducts will not, on this account, be dispensed with, and we are perhaps destined to see works, in the progress of this new mode of conveyance, which, in magnificence of design, and skill of execution, shall prove that the art is as yet but in its infancy. The wonderful and unexpected progress which but a few years have made in the power of transit, both as regards extent and speed, has left no bounds to the imagination in looking forward to the future.

ELEVENTH WEEK-SATURDAY.

RAILROADS WITH LOCOMOTIVE ENGINES.THE LIVERPOOL AND MANCHESTER RAILWAY.

THERE is another species of construction, of great magnitude and importance, noticed at the close of the last

paper, to which the present advanced state of science and of commercial intercourse has given rise, and which, though not necessarily connected with architecture, sometimes, like the canal, of which it is the successful rival, draws largely on the resources of this art. I allude to the railroad. This, in its simplest form, is not a recent invention. Nearly two centuries have elapsed since the introduction of tram-roads, rudely constructed of wood, which were afterwards improved by the substitution of iron. In the last quarter of a century, this mode of conveyance has rapidly increased, especially in the neighbourhood of Newcastle and Sunderland, where railroads have for some time been employed by private companies for the transportation of coals to the Tyne and Wear.

The first public railway for the conveyance of general merchandise and passengers, as well as of coals, was that of Stockton and Darlington, which was opened in September 1825. In 1822, a similar undertaking wa was projected, for facilitating the intercourse between Liverpool and Manchester; but it was not till after numerous delays and discouragements that it was completed.

The sagacious projectors of this latter undertaking, were, on good grounds, sanguine of success. Liverpool, as a commercial sea-port, is second only to London; while Manchester is an immense manufacturing town, and the centre and focus of a populous manufacturing district; and although an incessant interchange of commodities, amounting to upwards of a thousand tons per day, and constantly increasing, subsisted between these two towns, the modes of conveyance were at once tedious and expensive. These encouragements to the new undertaking, induced the projectors to persevere, and they at last effected their object at an expense of not less than eight hundred thousand pounds.

On the 15th of September 1830, this celebrated railroad was partially opened; and, on the 4th of December following, it was, for the first time, subjected, by way of experi

ment, to a full load of merchandise, in eighteen waggons, the gross weight of which, independent of the engine, was about eighty tons. This enormous load, which, if drawn along the turn-pike road, would have required eighty horses, employed for the period of sixteen hours, was conveyed from Liverpool to Manchester in less than three hours, by a single locomotive engine. This, however, is considerably more than the ordinary burden, and less than the usual speed. The distance, which is upwards of thirty miles, is commonly passed in about an hour and a half, being at the rate of twenty miles in the hour. But, on inclined planes, the speed is not less than thirty miles an hour.

The utility and safety of this stupendous undertaking, were thus established, and its success was secured, although it was not till sometime afterwards that it was in full operation. By the end of the year 1830, that is, in three months and a half, notwithstanding the imperfect state of the preparations, upwards of 70,000 passengers had been conveyed along the line, to various distances. Since that time, the amount of traffic, and of passengers, has far exceeded the expectations of the projectors, and has been rapidly progressive :-In the year 1832, the gross receipts were £155,600, and in 1836, they amounted to £234,600.

The nature of a railway is too well known to require a particular description. In the work of which I now speak, there were both peculiar facilities and difficulties. The general face of the country was sufficiently level; but there were places which had to be excavated to the depth of 60 or 70 feet in the solid rock, and others which required extensive embankments; while, in one place, a valley was to be passed by a viaduct of nine arches, each 50 feet in span, and, in their greatest height, 70 feet. A peculiar difficulty occurred in carrying the line across an extensive morass or bog, in some places between 30 and 40 feet deep, and so nearly approaching to a fluid state, that an iron rod would sink through it by its own gra