NOVEMBEE H), 1905.] 



SCIENCE. 



579 



is not possible to keep more than about four 

 cCres watered by one shadoof, so you may 

 imagine what an army is required to 

 irrigate a large surface. Another method, 

 largely used by the natives of northern 

 India, is the shallow bucket suspended be- 

 tween two strings, held by men who thus 

 bale up the water. A step higher is the 

 water-wheel, with buckets or pots on an 

 endless chain around it, worked by one or 

 a pair of bullocks. This is a very ordinary 

 method of raising the water throughout the 

 East, where the water-wheel is of the rudest 

 wooden construction and the pots are of 

 rough earthenware. Yet another method 

 of water-raising is very common in India 

 from wells where the spring level may be 

 as deep as one hundred feet or more. A 

 large leathern bag is let down the well by 

 a rope passing over a pulley and raised by 

 a pair of bullocks, which haul the bag up 

 as they run down a slope the depth of the 

 well. An industrious farmer with a good 

 well and three pairs of good bullocks can 

 keep as much as twelve acres irrigated in 

 northern India, although the average is 

 much less there. The average cost of a 

 masonry well in India varies from £20 to 

 £40, according to the depth required. But 

 it is obvious that in many places the geo- 

 logical features of the country are such 

 that well-sinking is impracticable. The 

 most favorable conditions are found in the 

 broad alluvial plains of a deltaic river, the 

 subsoil of which may be counted on as con- 

 taining a constant supply of water. 



PUMPS AND WINDMILLS. 



All these are the primitive water-raising 

 contrivances of the East. Egypt has of 

 late been more in touch with Western civ- 

 ilization, and since its cotton and sugar-cane 

 crops yield from £6 to £8, or even £10 per 

 acre, the well-to-do farmer can easily afford 

 a centrifugal pump worked by steam power. 

 Of these there are now many hundreds 



fixed or portable working on the Nile banks 

 in Egypt. Where wind can be counted on 

 the windmill is a very useful and cheap 

 means of raising water. But everything 

 depends on the force and the reliability of 

 the wind. In the dry western states of 

 America wind power is largely used for 

 pumping. It is found that this power is 

 of little use if its velocity is not at least 

 six miles per hour. (The mean force of 

 the wind throughout the whole United 

 States is eight miles per hour.) Every 

 windmill, moreover, should discharge its 

 water into a tank. It is evident that irri- 

 gation can not go on without cessation day 

 and night, and it may be that the mill is 

 pumping its best just when irrigation is 

 least wanted. The water should, therefore, 

 be stored till required. In America it is 

 found that pumping by v/ind power is 

 about two-thirds of the cost of steam power. 

 With a reservoir five to fifteen acres may 

 be kept irrigated by a windmill. Without 

 a reservoir three acres is as much as should 

 be counted on. Windmills attached to 

 wells from 30 to 150 feet deep cost from 

 £30 to £70. 



AETESIAN WELLS. 



Up to now the artesian well can not be 

 counted on as of great value for irrigation. 

 In the state of California there are said to 

 be 8,097 artesian wells, of a mean depth of 

 210 feet, discharge .12 cubic feet per sec- 

 ond, and original cost on an average £50. 

 Thirteen acres per well is a large outturn. 



In Algeria the French have bored more 

 than 800 artesian wells, with a mean depth 

 of 142 feet, and they are said to irrigate 

 50,000 acres. But this is scattered over a 

 large area. Otherwise, the gathering 

 ground would probably yield a much 

 smaller supply to each well than it now 

 has. In Queensland artesian wells are 

 largely used for the water supply of cattle 

 stations, but not for irrigation. 



