Gibb’s modules have been tried on various distributaries in the Punjab and found to give good results. It is believed however that in only one case has a whole distributary been moduled. The distributary is a large one, its length being 35 miles. It appears that the discharge reaching the tail of the distributary is not constant but varies, as was to be expected, when the head discharge varies for any length of time. The command on the distributary is good. There is nothing to show that matters would not have been improved, and money saved, by leaving some of the outlets without modules. It has been remarked above, that at the downstream end of a reach ending in a fall, the F.S. level of a distributary is not affected by silt. At the upstream end of the reach it is affected. There are thus two gradients, one flat, and one steep. It appears to have been decided in one case in the Punjab, that the minimum limit of supply for the module should be about half an inch below the flat line and the maximum limit ·3 feet above the steep line. In many cases a greater range would be required,[55] say a foot. [55] It is understood that a range of a foot can easily be arranged for, and that ranges of 3 or 4 feet can be introduced at slightly increased cost. In Chapter III. Art. 7, the case of a distributary without modules but with the outlets carefully adjusted, was considered. The question to be decided in each case is whether such an arrangement is preferable to moduling some of the outlets. This turns largely on the amount of attention which would be bestowed on the case. In view of the difficulty of securing such attention and of the trouble of constantly making alterations in a certain number of outlets, it is probable that moduling will in many cases be considered preferable. The question of moduling the heads of distributaries has also been considered in the Punjab. For minor or small distributaries modules are feasible. For a large distributary a module would be expensive and it appears that the present system of regulating is preferable. Kennedy’s “Gauge Outlet,” which is a kind of semi-module is described in Appendix K. It is being tried in the Punjab. APPENDICES. APPENDIX A. DIVIDE WALL ON LOWER CHENAB CANAL. (See page 50, first footnote.) [Illustration: FIG. 27.]