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Imperial Gazetteer of India, v. 3, p. 318.

3I8 TI1E ITADIAN EM1PIRE [CHAR Madras deltas, command nearly the whole of the lands lying between the main rivers in the former and the branches or arms of the deltas in the latter. In the Peninsula proper, conditions are less favourable. and the formation of the country prevents canals being taken far out of the river valleys. It must be remembered, too, that some large rivers, such as the Narbada and the Tapti, are throughout useless for irrigation, by reason of their deep and often rocky channels. Overlap- Although these three types are in themselves as distinct as ping of the sources of supply on which they depend, they sometimes types. overlap. Lifting appliances are often required to raise water from canals to ground on a higher level, and the cultivation under some tanks and canals can only be matured by the use of supplemental wells. Large storage works are incomplete without a network of distributing channels; and canals taking off from rivers in which the supply is uncertain and inter- mittent require storage works which may be constructed either at some distance up-stream from the head-works, in the valley of the main river or of a tributary, or as 'tail tanks' at suitable points on the line of the canal itself. But although in particular cases all three classes may be found in combination, each is so distinct from the others that it deserves separate consideration. Area irri- An important point in connexion with pure lift-irrigation gated from works is that they have been constructed by private enterprise wells. on the part of the owners or cultivators of the soil. The works are all of a petty character, and irrigate an area which may be as low as one acre and seldom exceeds twenty. Such works cannot conveniently be owned or maintained by the state, which can do no more than encourage their construction by agricultural loans and by liberal rules in the matter of land- revenue assessment. But although these works are small and have cost the state nothing, their importance in the aggregate is very great. Taking the average area annually irrigated from works of all classes in British India at 44,000,000 acres, it is found that nearly 13,ooo,ooo acres, or about 30 per cent., are irrigated from wells. Well-cultivation is moreover of the highest order; and it may be safely estimated that the produce annually raised from pure lift-irrigation is, in value, considerably more than a third of the out-turn from irrigation works of all kinds. The most favourable conditions for well-irrigation are found in the alluvial plains of Northern India, the subsoil of which contains an inexhaustible supply of water. Out of the 13,000,00o acres thus irrigated more than 9,500,000 are in the United Provinces and the Punjab, and about 2,750,0oo in the