Artesian Wells. 3^9 



from the decomposition of iron pyrites. When, however, the gas 

 from the latter has been evaporated by exposure to the atmosphere, 

 the water is often drinkable : indeed, cattle have sometimes been found 

 to prefer it to pure water, and vegetation flourishes when watered 

 by it. 



UTILISATION OF SUPPLIES. 



The existence of such supplies of .subterranean water would be 

 of little value unless a more economical method of reaching them 

 could be found than digging wells, but the advances made during 

 late years in boring machinery and methods of sinking boreholes 

 have practically solved the question, and the extensive experiments 

 made have proved that this magnificent store of water — one of the 

 Colony's most valuable assets^ — can be tapped and utilised at a cost 

 within the means of any stock-farmer or agriculturist. The boreholes 

 as yet put down, although admirable for the stock-farmer, are not 

 large enough to^ be used for extensive irrigation. However, one of 

 the principal improvements aimed at in sinking artesian wells is 

 the increase of the supplies by enlarging the diameter of the bore- 

 holes and deepening the same if necessary. From the small 

 beginnings already made in this direction developments of a highly 

 satisfactor}^ character are expected, which the addition of more power- 

 ful machiner}- to the boring plant has made possible in the future. 



DEPTH OF SUPPLIES. 



The depth at which water is struck varies considerably with the 

 geological formation and the earth-movement to which it has been 

 subjected, and ranges from lo to 800 feet. Search at greater depths 

 has not been carried on, because it is only now that boring machinen,^ 

 capable of sinking deeper has been provided, except in the case of 

 one bore in the Lower Karroo, which was put down to a depth of 

 1,500 feet with a machine of obsolete pattern, but produced no re- 

 sult from which anything could be learned on this subject. 



RISE OF THE WATER. 



The water in about one-third of the artesian wells rises to the 

 surface and sometimes above it. owing to the geological conditions 

 being such that the water-bearing stratum contains the water under 

 hydrostatic pressure. Some of these are the well-known conditions 

 where porous beds, which being exposed at the surface receive 

 supplies from the rains or rivers, are underlaid and also covered by 

 impervious strata, and the series of strata are bent into a basin or 

 trough with no escape for the water until boreholes are pierced 

 through me upper impervious beds, when the pressure forces the 

 water to the surface. Other less familiar conditions, producing a 



