_Lens la Deûle Canal._—Lens, a town of 11,800 inhabitants, and the capital of the coalfields of the Pas-de-Calais, has recently been connected with the existing system of navigable waterways by a canal, which passes near a great number of pits belonging to the companies of Lens and of Courriéres, the most important of the district, and serves the Liévin mines, which previously possessed no water communication. The probable traffic on this canal has been estimated at 290,000 tons, with a prospect of future increase. The canal starts a little beyond Lens, and passes close to the town; and after a course of 4 miles 7 furlongs it joins the Souchez Canal at Harnes. This canal, about 2 miles 1 furlong in length, was constructed about 1862, and connects the Lens Canal with the Deûle Canal a little beyond Courriéres. The total fall of the Lens Canal is 31 feet 10 inches, which is effected by three locks, the first by a fall of 8¼ feet and the other two of 11 feet 9½ inches. It has a bottom width of 17¾ feet in the straight portions, and in the curved portions the width at the bottom is regulated according to the formula (17¾ × 1246/R) feet; and its depth is 7¼ feet for an available draught of 6½ feet. Crossing places, 31 feet wide at the bottom and 360 feet long, have been formed about every 5 furlongs; and places for barges to wait in have been constructed of the same width, at the commencement and end of the canal, 2300 and 1800 feet long respectively. Above the third lock the canal traverses fissured chalk for a distance of 1640 feet, and has accordingly been lined with concrete up to 1 foot above the water level at a cost of 2_l._ per yard; and where the canal passes over a marsh, filled up with stones from the pits, for about 330 feet, it has been cut off from the marsh by a puddle-trench carried down into a substratum of clay 13¾ feet below the water-level. The locks are of the ordinary type, 17 feet wide, 126⅓ feet available length, and 8¼ feet in depth, with sluices in the gates; and the gates have iron ribs and a wooden skin, and cost on the average 4_l._ per square yard. The canal is fed by the river Souchez only 620 feet from its commencement. The discharge of the river during the long drought of the summer of 1886 did not fall below 4·6 cubic feet per second, whilst the traffic on the canal only required 2½ cubic feet per second, allowing for losses from evaporation and leakage. There is, therefore, an ample supply for other purposes, and for increased demands for traffic. The canal was begun on the 1st of February, 1885, and was opened for traffic on the 30th of October, 1886. The works, including land, cost 74,000_l._, or 15,206_l._ per mile.