11. =Outlets.=--The top of the head and tail walls of an outlet are level with the F.S. levels in the distributary and watercourse respectively. The steps in the head wall enable the cultivators to go down either to stop up the outlet or to remove any obstruction. The stepping is arranged so as to fall inside the side slope ultimately proposed. It is usual, in some places, to have the entrance to the “barrel” of the outlet made of cast iron. The cast iron pieces are made of various standard sizes. This to some extent prevents the “barrel” being built to a wrong size. A discrepancy between the size of the masonry barrel and that of the iron would be noticed, but if the masonry barrel is built too large the iron head does not always restrict the discharge. The action is the same as in a “diverging tube” well known in hydraulics. For sizes up to about 50 or 60 square inches the barrel should be nearly square. For larger sizes the height should exceed the width. Up to about 100 or 120 square inches the width can be kept down to 7 or 8 inches so that an ordinary brick can be laid across to form the roof. For larger outlets the height can be from 1·5 to 3 times the width, and the roof can be made of large bricks, concrete blocks or slabs of stone or of a flat arch of brickwork or by corbelling, but in this last case there should be two complete courses above the top of the outlet. The less the width the cheaper the roof, the easier the adjustment of size and the less the tendency to silt deposit during low supplies. If pipes are used they should be laid in concrete. If cast iron head pieces are to be used there should be several sizes of one width and the widths of the masonry outlets should be made to suit these widths. A masonry outlet is not generally built till the watercourse has been sometime in use. The exact position of the outlet should then be so fixed that the watercourse shall run out straight or with a curve and should not be crooked. The width between parapets should be, for a driving road or one to be made into such, 10 ft. (if the bank is wider, it should be narrowed just at the outlet site) and for a non-driving road, 8 feet to 3 feet according to the ultimate width of the bank. Earth backing should be most carefully put in and rammed, otherwise a breach may occur and the outlet be destroyed. Various attempts have been made to provide gates or shutters for outlets. The chief result has been trouble and increased cost. If grooves are made and shutters provided, the shutters are soon broken or lost by the people. Hinged flap shutters are objectionable because they are often closed by boys or by malicious persons or by neighbours who wish to increase the supply in their own outlet. The cultivator, when he wishes to reduce the supply or to close the outlet, can easily do this by obstructing the orifice with a piece of wood or an earthenware vessel or a bundle of brushwood or grass.