39^ Report S.A.A. Advancement of Science. 



him tO' walk about with a forked twig in his hands, which twig bows 

 itself down when the man passes over water under the ground. More- 

 over, if the " dowser " is exceptionally gifted, his twig, by other signs, 

 Avill tell him exactly at what depth the water will be found and the 

 quantity in gallons. As a professor in a Science College has written 

 428 pages on the subject, and presumably educated men, such as 

 Noblemen, Bishops and Members of Parliament, employ these clair- 

 voyant though illiterate men, it is not surprising that the Karroo 

 farmer should have developed a partialitv for the " dowser's " 

 mysterious art. 



PERCENTAGE OF SUCCESS. 



The degree of success, however, in finding water achieved by 

 the Government without any supernatural assistance in the selection 

 of sites, has been gratifying, as about 75% of the number of bore- 

 holes put down have yielded a satisfactory supply. There is, of 

 course, a certain element of chance in the striking of a good supply 

 of water, which has in the nature of things to be allowed for, but 

 which makes the work more fascinating than the almost certain 

 methods which can be applied to the collection of surface water. 



SIZE OF BORES. 



Some 3,500 boreholes have been sunk since the first machine 

 was imported in 1890. During the first two or three years little 

 progress was made, but the numbers have steadily increased since 

 then, and with the present plant about 500 boreholes can be jmt 

 down per annum. These vary in depth from 10 to 800 feet, and in 

 diameter from 2 to 6 inches. Many of these were originally put down 

 of the smaller diameters of 2 or 3 inches and were afterwards reamed 

 out tO' 4h or 6 inches, when the supply of water struck was large 

 enough to warrant it, in order to insert a deep well pump-barrel of 

 sufficient capacity. Only boreholes in the softer formations are lined, 



•or when the harder formations are interstratified with layers of looser 

 material which will not stand alone. Both collar-jointed and flush- 

 jointed tubes are used, as may be most suitable to the method of 



iboring adopted. 



YIELD OF BORES. 



The yields of these bores vary, in relation both to the size of 

 the hole and the strength of the supply, between 100 gallons and 

 100,000 gallons in each 24 hours. Generally, the water stands in 

 the boring much higher than where it was struck, but when it does 

 not flow at the surface it is raised by an ordinary deep well pump 

 and a windmill, or other power. Siphons, where the configuration 

 of the ground allows them, and suction pumps are made use of where 

 the water rises in the borehole to near the surface, and where the 

 •drawing off or pumping does not lower it enough to interfere with the 



