PROBLEMS OF THE ARTESIAN WATER SUPPLY OF AUSTRALIA. 135 



"Flow from rock pressure demands as its first condition that the 

 rock of the water-bearing stratum has lost its cohesion. It must 

 be plastic and mobile, crushed and comminuted ; otherwise it 

 exerts no more pressure on the water in its interstices than do the 

 iron walls of a water-main on the water flowing within them. The 

 walls of a high building exert great pressure on their foundations, 

 but it would hardly be suggested that this ' rock pressure ' 

 exerted upon the water pipes passing through or beneath these 

 foundations, is the cause of the rise of water from them to the 

 upper stories of the building. And not only must the rock of the 

 water-bearing stratum be crushed aud incoherent in order to 

 transmit rock pressure to the water which it contains; that water 

 must also have entered the stratum before the pressure was 

 exerted upon the rock, or before the rock was in a condition of 

 mobility so that it could transmit the pressure to the water. For 

 a pressure sufficient to squeeze water out of a stratum is sufficient 

 to prevent the entrance of water into that stratum. A flow from 

 rock pressure is limited, therefore, to the amount of water which 

 the water-bearing stratum will hold without replenishing. 



"With the theory of rock pressure as a general cause of artesian 

 flows, Arago's summary dealing is still sufficient (Sur les Puits 

 Fores. Annuaire par le Bureau des Longitudes, pp. 228 — 229, 

 Paris, 1835). He showed that there are three cases of rock 

 pressure which may be considered. The rocks above, and including 

 the upper impermeable stratum, either continue to yield until 

 they come in contact with the lower impermeable stratum, or 

 they stop in a position of equilibrium before that contact, or they 

 experience an oscillatory movement. In the latter case the flow 

 will be intermittent, and in the first two cases it will stop entirely, 

 and thus in any case the theory is incompetent to account for the 

 steady flow of artesian wells." 



With the object of ascertaining whether Mr. Robert 

 Hay's explanation (quoted by Professor Gregory) as to the 

 cause of the Kansas flowing wells, had received official 

 endorsement in the United States, I wrote to the Hon. Dr. 



