The proportions of this work far exceeded anything of the kind that had up to that time been attempted in England. It was a very costly structure; but Telford, like Brindley, thought it better to incur a considerable capital outlay in maintaining the uniform level of the canal than to raise and lower it up and down the sides of the valley by locks at a heavy expense in works, and a still greater cost in time and water. The aqueduct is an admirable specimen of the finest class of masonry, and Telford showed himself a master of his profession by the manner in which he carried out the whole details of the undertaking. The piers were carried up solid to a certain height, above which they were built hollow with cross walls. The spandrels also, above the springing of the arches, were constructed with longitudinal walls, and left hollow. The first stone was laid on the 17th of June, 1796, and the work was completed in the year 1801. AIRE AND CALDER CANAL. The Aire and Calder Canal, in Yorkshire, which is connected with the Leeds and Liverpool Canal at Leeds Bridge, and thence communicates with the Mersey at Liverpool, was originally constructed with locks 60 feet long by 15 feet wide, and with a depth of 3 feet 6 inches. It has been subsequently twice reconstructed in all its main features. In 1820, the diversion between Knottingley and Goole was constructed, with locks 72 feet long, 18 feet wide, and with 7 feet depth of water; but this being found inefficient, the whole of the works between Goole and Leeds, on the Aire branch of the navigation, and Wakefield on the Calder, have been again reconstructed, with locks of 215 feet long, 22 feet wide, and 9 feet on the sills. In addition to this, the undertakers have purchased and improved the Barnsley Canal, and also, to some extent, as lessees, they have extended their improvements to the Calder and Hebble Navigation. From time to time, the port of Goole, which forms a part of the Aire and Calder Navigation, has been improved, and its capacity enlarged, new docks and entrance-locks have been built, and the channel has been generally improved. The accompanying diagrams show the lines of canal communication between the Severn at Bristol and the Thames, and between the ports of Liverpool, Goole, and Hull. They give the length and profile of each canal, and require but little explanation. The Aire and Calder Canal has been in many respects one of the most remarkable in England. Its original capital was 150,000_l._, but it is now stated to amount to 1,697,000_l._ The difference has mainly resulted from accumulations of profit. After deducting the cost of maintenance, the sum available for distribution in 1888 was 85,000_l._ The gross yearly income is now as large as the original capital. MIDLAND CANALS.