FRENCH UNIT OF SUPPLY. 27 



rnnst the allowance be for those districts where the rain 

 fall is 10, 15, or 20 inches, and where the winds, almost 

 completely deprived of moisture, thirst intensely for it ? 

 Here is a consideration of great importance, and one 

 which cannot be disregarded. 



It will be evident to the thoughtful reader, that much 

 will depend upon the condition of the surface of the 

 soil maintained by the cultivator. The amount of evap 

 oration can be largely controlled by keeping the soil in a 

 finely divided and mellow condition, in which it holds its 

 moisture with the greatest tenacity. But there are crops, 

 such as wheat, oats, etc., which do not admit of cultivation 

 during their season of growth, and these must necessarily 

 require a larger quantity of water than such crops as corn, 

 or roots, which can be cultivated. 



In the dry and hot climate of Provence, a district in 

 the south of France where irrigation is extensively prac 

 ticed, it has been found necessary to use for each water 

 ing of the soil a volume of water equal to a depth of 3 1 1 2 

 to 4 inches over the whole surface every 10 to 12 days, 

 the usual interval between the waterings. This is equal 

 to about 24 cubic inches, or nearly half a quart per second, 

 continually flowing for each acre of surface. This allow 

 ance, which in French measures is equal to 1 litre per 

 hectare, or 61 cubic inches (=1 litre) per 107,640 square 

 f ee t (=1 hectare), is the basis for all contracts between 

 the government which controls or supervises the water 

 supply, and the owners of the canals (compagnies con 

 cessionaires de canaux), and between the latter and the 

 farmers who buy the water from them. It is the official 

 and legal unit of supply, as it were, and is a valuable 

 general indication, applicable to any locality or country, 

 where water may be used to irrigate soils of different 

 characters and for different crops. This may be taken 

 as the mean quantity, to be decreased or enlarged as cir 

 cumstances may necessitate the change. 



