XXXIV. ABSTRACT OF PROCEEDINGS — APPENDIX. 



laishwaram, near Rajahmundry, at the head of the Goda- 

 very Delta ; the Kistna system of canals taking off at the 

 head of the delta at Bezwada; the Oauvery system of 

 canals taking off the rivers Coleroon and Oauvery near 

 Trichinopoli ; the canals taking off just above the Delta 

 Barrage in Egypt, which irrigate the delta. 



The foregoing systems of perennial canals are fine ex- 

 amples of their kind, and they will be mainly considered in 

 regard to their efficiency in supplying water to irrigate the 

 land under cultivation. They are all artificial channels 

 supplied from rivers giving an ample supply of water, and 

 are separated into branches, each of which is provided with 

 major or minor channels supplying directly the water 

 courses connected with the irrigated areas. Great care is 

 necessary in designing these canals in order that they may 

 fulfil their purpose efficiently and economically, and the 

 proper site and nature of the head works are of the greatest 

 importance. 



The head works consist of a weir across the river pro- 

 vided w itl> under sluices. The entrance to the canal is 

 through head sluices for regulating the supply of water. 

 The main objects of a weir across the river are to raise the 

 level of the water in the dry season, when the river is low, 

 and to provide a means of forcing it through the head sluices 

 of the canal. The under sluices, which are constructed in 

 the weir itself, are necessary to create a scour during the 

 flood season to keep a definite channel open above the weir 

 in the neighbourhood of the canal head, so that there may 

 be no difficulty in leading the water to the head sluices 

 when the river is low. 



In India weirs are divided into six classes : — 1. Founded 

 on rock. 2. In the boulder formation at the head of rivers 

 near the hills. 3. In clay or kunkur soils. 4. On sand 

 overlying clay or rock which can be reached in a reasonable 



