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in tracing the canal, that the water was not contained by the made earth to a greater depththan from 2 to 3 feet; when the earth was not of a nature to hold water, the banks werelined with clay 2 feet thick, founded on the solid earth or on layers of shells, or in defaultof these at 4 feet below the bottom of the canal. This lining rises vertically to the level ofthe water, at 2 feet distance from the smaller set-off; where the canal is raised above theland, the bottom is lined 2 feet in thickness; the slope of the banks is either sown with hayseeds or turfed. In places where stone was common, the interior of the canal to the levelof the water was faced with dry stone, 97 centimetres thick at the summit, giving it a slopeof one and a quarter ; in such places the canal is only 33 feet wide at the bottom.

Locks all have a fall of 10 feet, except the two guard locks. The length between thegates is 108 feet, the breadth of the lock is 17 feet; at 6 feet above the bottom thefacing to the side walls slopes one-sixth; the thickness at the summit is 4 feet, andat the base 9 feet; the height above the bottom is 16 feet, the water rising to within 18inches of the summit; the side walls are prolonged by winged and return walls ; the platformat bottom is formed of a concave arc, 9 inches versed sine, its least thickness being 26 inches.In light soils it is made 3 feet 4 inches ; in bad foundations piles were driven, and theplatform laid on arches. The wall over which the water is discharged is curved in front togive additional strength to the frame of the gates, its projection is 5 feet 3 inches; under itare the channels through which the water passes to fill the lock ; they are 20 inches indiameter, and spring from the middle of the recess in which the gates are placed; they wereclosed by a wooden plug, which was found inconvenient from the pressure of the atmosphereafter the water was lowered, and they were afterwards exchanged for valves, which answeredbetter. The entrance is furnished with a frame, to which a sector is adjusted, closing itperfectly. 'Hie sector is moved by a lever, acting on a stone arranged for the purpose atthe top of the walls of the lock. The water passes from one lock to the other by channelsformed in recesses made in the side walls, so that it cannot in any way injure the platformof the lock. All the masonry of the walls is in freestone 14 inches thick, and generallycramped with iron run with lead. The whole is lined with beton, 8 centimetres thick, toprevent filtration ; at the back of all the walls is a coating of clay 28 inches thick.

Gates of the Locks. — The upper gates are 10 feet, and the lower 19 feet in height, so thatthe top rail rises 18 inches above the ordinary level of the water. The width of the gates is10 feet 8 inches, the frame 12 inches square, the sills are 9 inches, and the braces 6 by 7 inches ;they are covered with deal 2 inches in thickness, ami the joints are securely caulked. Thehanging posts are cut partly circular, the diameter being 12 inches, and in part bevelled ; theframework is morticed and tenoned together ; the iron work let into the rails is an inchwide, and half an inch thick ; the pivots and socket are of cast iron; the collars at top are12 inches in diameter, their height 2 feet, and their thickness about an inch ; they carry afemale screw ; the male screw passes into timber secured in the masonry ; they are 10 feetlong, and an inch thick; the timber under water is pitched, all the other is painted in three oils.

Houses of the Lock-keepers ; they are in length 33 feet, and 23 feet wide, outside di-mensions ; they contain a chamber 9 feet square, a smaller one, and a scullery ; in this is astaircase to the garret and cellar ; there is also an oven 5 feet in diameter, the cellar is vaulted,and extends under the smaller chamber and scullery, the height of the chamber is 9 feet.

The aqueducts and drains are five in number, and from 3 to 9 feet span ; where a greaterspan is made use of, there are several arches, their breadth varies according to that of thetowing path ; platforms of timber are laid under all; the height of the piers is at the least3 feet, and their thickness 20 inches ; it is 3 feet 4 inches when the span of the aqueduct is9 feet. The piers of the arches of 6 feet span are 18 inches thick, and those of the archesof 9 feet are 21 inches ; the thickness of the vaults is 18 inches ; the facings of the head andwing-walls are of freestone, the rest is of moellon. It was attempted to make the aque-ducts pass as near as possibly under the mur de chute, by which one wall was saved ; andthe canal being there more elevated, it was easier to make the aqueduct pass below it.Experience shows some inconvenience from this arrangement, as it is not possible to constructthe mur de chute as it ought to be — to guard against the pressure or weight of water whenthe lock is full; and to prevent the water filtering through the wall, care was taken,whenever an aqueduct was reconstructed, to place it above the lock, and to separate itentirely.

Bridges — Those on the great roads are from 25 to 26 feet in width, those for the crossroads are 18 feet 6 inches, their span is everywhere 25 feet, and their height, from thebottom of the canal to the soffite of the vault, is 18 feet. The arches are segments of a circle,one-sixth of their circumference ; the thickness of the arch is 2 feet 3 inches on the face,and 2 feet on the interior; the abutments are perpendicular before and behind, theirthickness is 6 feet 9 inches, that of the wing-wall is 3 feet 6 inches. The slope for bridgeson great roads is one-twenty-fourth, and one-twelfth for those on cross-roads. A quay wallfaces the towing path, in breadth 8 or 9 feet between the parapets; the thickness ofthe wall is 3 feet at the summit, 3 feet 6 inches at the base, and its height is 6 feet. Thebridges over the locks are the same height and breadth as the others, but their span is only

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