IREIGATIOTI WOBBrg. 239 



which is to be rid of its superfluous moisture. Here it is essential 

 that the lower layers shall receive as little as possible of the atmos- 

 pheric precipitation, that this precipitation shall affect as thin a 

 layer as possible of the earth's surface, and that the entire stratum 

 containing an excess of moisture shall be drained. Hence the 

 principles to follow in the present case will differ from those 

 observed in designing, cutting and constructing the drains in the 

 other case mainly in the following respects : — 



(i) None of the drains should be covered, so that they may act 

 as quickly and with as little delay as possible, and allow as little 

 as possible of the atmospheric precipitation to sink into the earth. 



(ii) The recei-\dng and outflow drains should be given a more 

 rapid fall, and must therefore be more carefully protected against 

 erosion. 



(iii) The collecting drains should be as deep as the greatest 

 depth down to which superfluous moisture penetrates. 



SECTION lY. 



Irrigation Works. 



The great Changa Manga plantation owes its remarkable success 

 to the excellent system of irrigation adopted there ; and indeed 

 we may go so far as to say that it is owing to this irrigation that 

 the plantation has at all been possible. Almost everywhere out- 

 side the Himalayas drought is one of the greatest obstacles to the 

 stocking of bare wastes ; to it must be traced most of our numer- 

 ous failures even where the annual rainfall exceeds 40 inches, and 

 to it is due the now proverbial charge made against us of inability 

 to restore, within a reasonable time, the enormous areas of ruine 1 

 forests that past improvidence has handed down to us. Such being 

 the case, wherever the Canal Department has water rmming to 

 waste, or natural facilities exist for the construction of a cheap but 

 effective system of irrigation works and the requirements of the 

 population in respect of forest produce are insufliciently met, there 

 irrigation should be resorted to without hesitation, as the certainty 

 and rapidity of success will repay over and over again the special 

 outlay entailed. Even well irrigation will be practicable and 

 remunerative near large markets where the water level up to the 

 early part of March is not more than 10 to 15 feet from the surface 

 and no rock has to be bored through. 



For canal irrigation no better treatise on the construction of the 

 necessary works specially adapted to the conditions of this country 



