Vol. 65.] ANNIVERSARY ADDRESS OB" THE PRESIDENT. CVli 



superficial, but by underground streams. The Nile loses in volume 

 owing to evaporation after passing Aswan, yet at the same time 

 fresh water exists underground ; and that this is not stagnant but 

 flowing, is shown by the fact that it is inhabited by freshwater fishes, 

 crabs, and other organisms. Below the Sahara there is a flow of 

 underground water, directed towards the south. Several distin- 

 guished geologists in Australia consider that the subterranean water 

 of the central desert flows out under the Ocean, and issues through 

 its floor. Prof. David asserts that it does not discharge under the 

 •channel of the Darling River, but probably finds an outlet somewhere 

 in the Great Australian Bight. 1 David & Pittman inform us that 

 the porous beds which hold this water are exposed over an area of 

 18,000 square miles and receive a rainfall of 25 inches, a large part 

 of which is absorbed. An absorption of 20 per cent, would furnish 

 a supply amounting to 14-2 cubic miles, and most of this must 

 somehow find its way to the sea. In West Australia also, according 

 to Pittman, 2 the subterranean water finds an issue below the sea : 

 thus at Perth, an artesian well afforded a supply of 500,000 gallons 

 per day from a depth of 500 feet. Abundant streams escape from 

 the foot of the Darling range, but disappear before reaching the 

 •coast only 15 miles distant to the west. 



Subterranean water, as a rule, is comparatively rich in dissolved 

 material ; in South Australia it contains sodium-carbonate. 



Submarine outflows of fresh water are by no means restricted to 

 the neighbourhood of desert-regions. They will occur wherever th.e 

 structure of the ground affords the necessary conditions. Instances 

 •on a small scale occur off our own shores, as on the northern coast 

 of County Clare in Ireland, where at a place close to Ballyvaghan, 

 as Mr. J. A. Douglas informs me, fresh water bubbles up from the 

 beach at low tide. Shepherds bring their flocks to this spot to 

 drink. Similar cases occur on the coast of France, as in the 

 Departement des Bouches du Rhone, where spriugs jet up from the 

 bottom of the sea, one of them giving rise to a considerable current 

 at the surface. It is asserted that the water discharged by con- 

 cealed affluents into the Mediterranean, between Nice and Genoa, 

 amounts to at least 216 cubic feet per second or 0-016 cubic mile 

 per annum, a little more than one half of the Pecos at Pecos. 



Not a single persistent stream enters the Red Sea from the sur- 

 face of the land, but there are several, it is said, which escape from 

 its floor. 



1 T. W. E. David, Proc. E, Soc. N. S. W. vol. xxvii (1893) pp. 422, 423. 



2 Animal- Keport, Dept, Mines & Agric. N. S. W. 1897, p. 137. 



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