president's address. 555 



The Government Geologist of South Australia, Mr. Y. L. 

 Brown, who was formerly a Member of the Geological Survey of 

 New South Wales, has during the year made an exploration of the 

 eastern portion of the interior of that colony, and his published 

 report with Map and Sections, furnishes some interesting and 

 important information. The objects of this journey were to 

 ascertain the extension from New South Wales into South 

 Australia of the gold-bearing rocks of Mount Brown, and the 

 Cretaceous formation in which Artesian and other water has been 

 found. The extension of the Cretaceous and Tertiary area into 

 this colony from New South Wales and Queensland, was proved 

 along a distance of 225 miles of boundary of the former, and 300 

 miles of that of the latter colony. 



The southerly extension of this great Cretaceous area is limited 

 by the primary rocks which continue in a westerly direction from 

 the Barrier Range in New South Wales. Artesian Wells have 

 been obtained in the Cretaceous formation, and the numerous 

 conical mounds which have been formed by mud springs still 

 flowing as well as by others now extinct, are evidences of 

 natural Artesian Springs. In places these mounds are so 

 numerous as to give the country the appearance of a deserted 

 diggings. The Flinders and other ranges lying to the south of the 

 plain and sandhill country, act as a dam to prevent the subter- 

 ranean water from reaching the sea ; this gives rise to the natural 

 Artesian Springs, such as Mulligan, Blanche water, etc. The 

 natural Artesian Wells show that in those localities water will 

 rise to the surface when the water-bearing strata has been pierced. 



One of the most marked features of the Cretaceous country are 

 the peculiar sandhills. As to the origin of the sandhills, Mr. 

 Brown says — " I have reason to believe that in many cases, parti- 

 cularly in those of the isolated ridges and mounds traversing the 

 stony desert at long distances apart, the sand has been derived 

 from an underground source through the pressure of subterranean 

 water. There was in all probability an outlet at one time 

 connecting the old Cretaceous sea which occupied the centre of 

 Australia with the ocean. If we suppose a sudden or gradual closing 



