408 T, W. E. DAVID. 
eruptive rock, which there occurs in the form of a dyke of decom- 
posed basalt about twenty feet in width. This barytes has 
probably been derived from the basalt. 
At Pyrmont Sandstone Quarries barytes occurs under similar 
circumstances, and at the Pennant Hills Quarries it occurs in thin 
segregated veins in the basalt itself, at a depth of over fifty feet 
below the surface. 
Norres on ARTESIAN WATER tn NEW SOUTH WALES 
AND QUEENSLAND. 
(PARE EIS) 
By Professor T. W. E. Davin, B.A., F.G.S. 
[Read before the Royal Society of N. S. Wales, October 4, 1893. | 
In some previous notes communicated to this Society on November 
Ath, 1891, the author referred specially to natural artesian water 
in the form of mud or mound springs. On the present occasion 
it is his intention to read a few short notes explanatory of the 
lantern views exhibited to-night illustrative of artificial artesian 
water, and the principal artesian bores of New South Wales. The 
photographs from which the lantern slides have been prepared, 
were taken by Mr. Kerry during a recent tour in the artesian 
water district. A working model is also exhibited illustrative of 
the convexity of the curve of the hydraulic grade in the artesian 
basin of the Darling River. 
I. Artres!AN WELLS OF THE SAHARA. 
In the first place attention might be called to the experience 
lately gained by the French engineers in artesian boring in the 
Sahara. According to an official report,* the geological forma- 
* Rapport a Monsieur le Governeur Général del’ Algerie sur les Forages 
artésiens exécutés dans la Division de Constantin, de 1860 4 1864. 
