1915] on the Visit of the British Association to Australia 349 



One result of the bare fallow system is that the wheat countiy in 

 South Australia and in other regions where similar soils prevail has 

 a very beautiful aspect, owing to the contrast the rich red colour of 

 the bare soil affords with the green of the adjacent fields on which 

 wheat is growing. The effect is very like that to be seen in South 

 Devon. The soils referred to are the so-called Laterites, containing 

 a large proportion of iron oxide, which prevail over a large area in 

 Australia ; such lateritic soils are formed apparently by chemical 

 concentration at the surface of iron oxide from the underlying 

 weathered rock. The laterites are poor soils agriculturally and do 

 not respond to any artificial manures whatever except phosphates, of 

 which they contain a very small proportion. Altogether surprising 

 results have been obtained in various parts of Australia by the 

 application of quite small amounts of a phosphatic manure. Land 

 to the east of Adelaide, in the region known as the 90 mile desert, 

 the so called Mallee country, which was formerly deemed useless, is 

 now being brought under cultivation, as it is found to yield fair 

 crops of wheat after treatment with superphosphate. It is impossible 

 to raise a variety of crops in rotation under the conditions referred 

 to and this is true of the wheat lands generally, I believe ; but 

 under irrigation such lands yield astonishing crops — I saw a field at 

 Roseworthy, near Adelaide, on which Egyptian clover was grown 

 luxuriantly and was told that as much as 36 tons per acre had 

 been cut. 



To obtain a supply of water within the dry areas, artesian wells 

 have been sunk at great expense all over the continent. The basins 

 which within such wells are operative are indicated in the map Fig. 11. 

 The character of these basins may be illustrated by a section across 

 a line drawn from the Gulf of Carpentaria southwards to the Great 

 Australian Bight (Fig. 12). 



The question of the origin of artesian waters has given rise to 

 much discussion and is a problem of great importance. The head 

 has fallen one-third in the course of the last five years. There 

 appears to be little doubt that the water is largely derived from 

 rainfall but it is held by Professor Gregory, in particular, that some 

 may be of plutonic origin — that is to say, that changes are going on 

 in the deep-seated rocks which lead to the separation of chemically 

 combined water ; the injection of this deep-seated water, which is 

 probably superheated, causes a gas pressure in the water of cisternage 

 which forces it to the surface when it is reached by boring. The 

 intake beds are estimated to cover an area of 60,000 square miles in 

 Queensland and 10,000 in New South AVales ; the total length of 

 bores sank in the latter State is 158 miles. 



Tlie character of the outflows will be obvious from the slides now 

 shown. But there are various difficulties connected with the artesian 

 water supply. In certain districts the water rapidly corrodes the 

 iron or steel pipes with which the bore is lined and thev become 



Vol. XXI. (No 109) 2^ 



