380 Report S.A.A. Advancement of Science. 



crevices or cavities in the pervious strata. Such water can be 

 reached and recovered by means of tunnels, if in the hill side, or 

 else by boreholes or wells. A paper on this subject will be read 

 during the present session, and it is not necessary, therefore, to say 

 here more than that the cost of raising such water to^ the surface is, 

 owing to the scarcity and high price of fuel in the Colony, at present 

 prohibitive except when dealing with comparatively insignificant 

 quantities. 



The same drawback exists in the case of rivers with high banks, 

 where the lands tO' be irrigated are situated some 30 to 40 feet above 

 the river bed. Several very promising irrigation schemes on the 

 Orange and other Colonial river systems had tO' be abandoned 

 through this cause, the local conditions being such that only by an 

 abnormally long canal, the maintenance of which would be much too 

 co.stly, could water be conveyed to such lands by gravitation. 



With regard to the second main point, namely, the utilization of 

 the water collected and stored, this falls partly within the scope of 

 the Engineer and partly within that of the Agriculturist and Chemist. 



To the Engineer belongs the construction of the head works, 

 the main canal, sluices, aqueducts, flumes, flood gates, overflows, 

 bridges, and so forth. 



The main difficulties are met with in the construction of the 

 main canal, passing as it does through soils and materials of all sorts, 

 now through hard rock, next through gravel or thrcnigh sand, \\hen 

 pitching with stone or puddling with stiff clay may become 

 necessary. 



Rivers and swamps have to be dealt with in the most economical 

 manner, and overhanging krantzes negotiated by laying pipes or 

 flumes on brackets fastened tO' the rock. Careful and accurate 

 levelling is of the utmost importance in order that the water may have 

 a gradual fall towards the end. The hydraulic gradient must be 

 reduced to a minimum in order that a maximum of irrigable land may 

 be commanded, in recent cases the fall being as little as 8 to 9 inches 

 per mile. 



Much trouble is caused to weirs and canal l)anks by moles, cral)s, 

 and rats, which burrow for sustenance and moisture under the 

 bottom and through the banks, and cause serious leaks which are 

 difficult to locate and to stop. The tramping of cattle and sheep u]) 

 and down the banks in search of water also causes frequent damage, 

 and last, though not least, thunderstorms and winter floods fre- 

 quently destroy in the course of a few hours the work of many 

 months. 



IntO' the question of applying the water when it has been brought 

 to the lands it is not the object of this paper to enter — it is a verv 

 large and very important subject for this Colony, and will probal^K 

 be dealt with on a future occasion. 



Under the Acts enumerated above only two public schemes have 

 so far been constituted. 



Some 15 years ago an Irrigation Board was established at 

 Warrenton on the Vaal River, and has been in existence since. It is 



