1897. NOTES AND COMMENTS. 229 



Artesian Water. 



We have more than once drawn attention to the valuable work in 

 searching for artesian water that is being carried out by the Geo- 

 logical Survey of Queensland. This has lately given rise to two 

 papers (Proc. Roy. Soc. Queensland, vol. xii.), one by A. G. Maitland, 

 " On the geological structure of extra-Australian Artesian Basins," 

 which deals chiefly with those in North America. It appears from 

 this that nowhere in that region, except perhaps at Denver, are the 

 water-bearing rocks disposed in the shape of the textbook diagram. 

 On the contrary, the water-carrying beds are so arranged that there is 

 only one side of a synclinal trough, so that the strata present abundant 

 facilities for the escape of the water, which can actually be seen to 

 leak from them in the form of rivers. 



Similar questions are dealt with in the second paper, that by 

 R. L. Jack, " On the submarine leakage of Artesian Water." His con- 

 clusions are given as follows : — " The question at issue is no longer 

 whether the water which, when tapped by bores, issues in artesian 

 wells, occurs in porous strata lying underneath impermeable strata. 

 The bores themselves have settled that, and the outcrops of the 

 strata have been to some extent mapped, and found at altitudes 

 sufficient to give a ' head ' capable of forcing the water to the 

 surface in the lowlands of the West. These outcrops, moreover, 

 have been detected in the act of absorbing, year by year, more 

 than water enough to supply the wells and springs. The question 

 is, whether the strata form a sealed basin, or crop out beneath 

 the ocean in such a manner as to give rise to a circulation of the 

 underground water. A mass of evidence has been accumulated to 

 prove that, as the strata are periodically filled up with water, they 

 must first have lost a certain amount by leakage. In the case of 

 Australia the only possible escape is beneath the ocean, and although 

 we cannot observe this leakage with the bodily eye, we may believe in 

 it, as we believe in many things we cannot see. A powerful confir- 

 mation of this view is supplied by the fact that some important 

 artesian basins elsewhere leak out on land, while the rest have 

 the physical conditions which must inevitably lead to submarine 

 leakage." 



Differentiation in Rock-magmas. 



In the ]a.nuaTy nnmher oi the American Journal of Science, Dr. G. F. 

 Becker, under the title "Some Queries on Rock Differentiation," 

 makes a weighty attack upon certain hypotheses which have been 

 advanced by petrologists to account for the apparent derivation of 

 different rock-types from a common source. He approaches the 

 subject from the physical side, and considers in turn the two distinct 

 suggestions of diffusion in a magma owing to differences of temperature, 

 etc., and the separation by cooling of parts of a magma which are 

 miscible only above a certain critical temperature. 



