14. =Miscellaneous Items.= On Indian canals the chainage[24] is marked at every thousand feet. Five thousand feet is called a “canal mile.” The distance marks are often cast iron slabs, fixed in a cylindrical block of brickwork about 2·1 feet in diameter and 1·5 feet high, the upper edge being rounded to a radius of ·4 feet. The wedge-shaped bricks for these blocks are specially moulded. The iron slab should project about eight inches and have about a foot embedded in the brickwork. [24] In India, instead of the simple word “chainage” the term “reduced distance” is used. It is the distance reduced to a common starting point as levels are reduced to mean sea level. The expression is puzzling to non-professionals and new comers. On a canal having a wide bank the distance mark is put at the outer edge of the patrol bank, earth being added, if necessary, to increase the width. On a distributary with a narrow bank the mark should be on the opposite bank not the patrol bank. To enable the miles to be easily distinguished the masonry block can be sunk only ·5 foot in the ground, the others being sunk a foot. In all cases the masonry block rests on a pillar, 1·7 feet square, of bricks laid in mud, carried down to the ground level. Profile walls (Fig. 21, page 92) used occasionally to be built at frequent intervals along a distributary. They will not prevent scour occurring, if the stream is tending to scour, unless very close together. Such walls are of some use as showing whether the channel is altering, but they are expensive and have to be altered if, as often happens, the channel is remodelled. It is a much better plan to lay down blocks--about 1¹⁄₄ foot cubes--of masonry or concrete, along the centre line at every 500 feet, with their upper faces level with the bed. If the bed scours they may be displaced but otherwise they are useful not only for showing what silt, if any, has deposited, but for showing the centre line of the channel. Without them the centre line is liable to be altered in silt clearances or berm cuttings. To enable a block to be readily found and to be replaced in proper position if displaced, there should be two small concrete pillars exactly opposite to it and equidistant from it, one on either bank of the channel. Such blocks and pillars may with advantage be placed at quite short intervals on curves.