69 



have called the Cunningham Plains) must have formed in 

 succession a deep land-locked baj, a lake, and a salt marsh 

 before it assumed its present aspect, gradually brought about 

 by the detritus from the surrounding hills being washed into it 

 and filling it up by degrees. Yorke Valley will, at the same 

 time, have been a long narrow arm of the sea, probably the 

 estuary of a gently-flowing tidal river communicating with 

 Spencer's Gulf near about Port Victoria (several other, but 

 much smaller, similar low areas exist along the southern branch 

 of Horse Gully). That matters really were as represented 

 appears to be proved by the physical aspect and the nature of 

 the deposits. In Torke Valley, for example, there exists 

 some low ground, about four miles N.E. of Maitland, which is 

 still covered by water, though only very shallow, through the 

 wetter portion of the year, but even in summer a few feet of 

 sinking reach the level of permanent water, though of brackish 

 taste, clearly indicating that there had existed a lake of some 

 dimension before filled up by the mud brought by the rains 

 from the neighbouring hills. The deposits are of but recent 

 origin, and reach a thickness of more than 170 feet at a well 

 near Mr. Rogers' Yorke A^alley station, about one and a 

 half miles S.E. of Maitland, i.e., somewhat below sea level, and 

 the strata pierced by it consisted wholly, as far as my infor- 

 mation goes, of clays and gravels similar to those met with in 

 the Ardrossan cliffs. 



The lake that presumably occupied the site of the present 

 Cunningham Plain was finally drained by the erosion of its 

 outlet through Horse Gully, which certainly seems to have 

 been formed much anterior to this period, but re-closed during 

 the subsequent submersion, and again washed out by the out- 

 flowing of water. At present not a drop of the water supplied 

 by an average of about twenty inches rainfall per annum finds 

 its way to the sea above ground, the fall of the land being so 

 slight and the soil (arenaceous and marly clay, succeeded by 

 sub- globular calcareous concretions, &c.,) so porous that the 

 supply of the heaviest showers is almost immediately absorbed. 

 Again, at the narrow outlets very little below the general level 

 the underground drainage appears to be prevented by the rocks 

 rising to very near the surface, and the wells and springs 

 along the seashore exhibit such very weak inflow, entirely 

 inadequate to requirement in proportion to the area drained, 

 that the question naturally arises, what becomes of the supply 

 of rain-water ? The only well sunk in this area is in Section 

 83, is said to be ninety feet deep, piercing only clays, gravels, 

 and sands, while the elevation of the surface is only estimated 

 at about thirty to fifty feet above sea level, thus also placing 

 the brackish water found at that depth below the sea, proving 



