PROBLEMS OF THE ARTESIAN WATER SUPPLY OF AUSTRALIA. 105 



origin in rainfall" has much to commend it. The material 

 point to be argued here is as to whether the artesian water 

 supply of the Australian basin has been derived from rain- 

 fall, and has been stored in the porous sandstones under 

 hydrostatic or hydraulic pressure, or whether, as contended 

 by Professor Gregory, it has been evolved from underground 

 masses of igneous rocks, and is forced above the surface in 

 bores by the influence of temperature and rock-pressure. 

 The Professor refers to the '* simplicity" of the former 

 hypothesis as if it were something reproachful, but it is 

 generally conceded that a simple explanation of a geological 

 problem is to be preferred to one involving far-fetched or 

 complicated reasoning. 



It is proposed to deal first with the objections urged by 

 Gregory against the hydrostatic pressure theory, and then 

 to consider the theory which he propounds in lieu of it. 



Loss of Head through Friction.— The objections are 

 based upon both physical and chemical considerations, and 

 the principal one is that, owing to the great distance (600 

 miles) which the water would have to travel underground 

 between the intake-beds on the flanks of the Dividing 

 Range and the bores at Lake Eyre, friction would cause 

 the disappearance of the whole of the head. 1 



So far as is at present known the Australian artesian 

 basin is the largest in the world, but there are some other 

 well known basins of very respectable dimensions; for 

 instance the Paris basin is about 100 miles wide, 2 while 

 the water-bearing beds of the Dakota basin extend for 

 about 350 miles. 3 



1 The Dead Heart of Australia, pp. 300 - 305. 



3 Prestwich, Quart. Journ. Geol. Soc, 1872, xxviii., p. lix. 



3 The Motions of Underground Waters, C. S. Slichter. Water Supply 

 and Irrigation Papers, U. S. Geol. Sur, No. 67, p. 56. 



