234 ECONOMIC GEOLOGY 
water to the surface like the expanding compressed air in 
an air-lift pump. 
The basin of flowing wells in East Central Australia occu- 
pies an area of 602,000 square miles in Queensland, New 
South Wales, and South Australia. The wells render possible 
the pastoral use of the country, as the water is good enough 
for stock, though not for irrigation. The country consists 
of a foundation of contorted ancient rocks covered to the 
south by compact fresh-water Jurassic sandstones, and to 
the north by marine Permo-Carboniferous rocks. The 
sandstones are covered by clays, limestones, and thin sand: 
stones of the Rolling Downs Formation (Cretaceous). The 
sandstones outcrop in the eastern part of the plateau at 
levels of 2000 feet; and they dip westward until in the Lake 
Eyre basin they are 5000 feet below sea-level. Wells bored 
into the sandstones yield supplies of water which rise to the 
surface in places with sufficient force to work turbines for 
wool scouring and electric light plants. The water is hot, 
and from many wells its temperature as discharged was above 
200° F., and in one well was 210°. The rise of temperature 
beneath the surface, if the water comes from the level of 
the bottom of the bore, would be sometimes as rapid as 
1° F. for 22 feet in descent; rarely is the rate as low as 1° 
in 53 feet, which in some parts of the world is regarded as 
the normal gradient. The high temperature indicates that 
some of the water reaches the sandstones from a much 
greater depth than the bottom of the bore. The water is 
generally rich in alkaline carbonates, including those of 
soda, potash, lime, and magnesium. It is low in sulphates 
and sodium chloride. The wells reach a depth of 7000 feet, 
and some of them gave an initial yield of over 4,000,000 
gallons a day, and many vielded over 1,000,000 gallons a 
day. 
The usual explanation was that these flowing wells dis- 
charge rain-water that fell on the Eastern Highlands of 
Australia, percolated through the sandstones from the out- 
crop, and is forced to the surface by the pressure of the 
water in the higher part of the bed. It was calculated that 
the renewal of the well water from the rainfall so greatly 
exceeded the discharge from the wells that their outflow was 
relatively insignificant. In 1891 the Lower House of the