[Proc. Rot. Soc. Victoria, 33 (N.S.), 1921]. 

 Akt. V. — A Geologist's Notes on Water-Divining. 



By GRIFFITH TAYLOR, D.Sc, BE., BA. 



(With Plate IV. and two Text Figures). 



[Read July 8th, 1920]. 



In view of the widespread belief in Australia in the powers 

 -of the Water Diviner, the following personal experiences (fol- 

 lowed by the authoritative opinions of others) should be of in- 

 terest to members : — 



On a recent visit to the Federal Capital Territory, I devoted 

 several days to the question of water supply for the repatriated 

 soldiers in the valley between the Ainslie-Majura ridge and the 

 Black Mountain ridge. 



The general geology is simple. The valley runs north and 

 south, and consists essentially of Silurian shales and clay-slates 

 covered by a variable thickness of recent alluvial. These shales 

 are flanked on the west by the harder sandstones and quartzites 

 of Black Mountain, which form a ridge about 800 feet above 

 the plain. (See Text Figs. 1 and 2.) 



On the east is a ridge of hard porphyry or tuff. These eruptive 

 rocks are probably later than the sedimentary shales and sand- 

 stones. This porphyry constitutes Mount Ainslie and Mount 

 Majura. The line of junction between the porphyry and the 

 shale runs north and south except for a spur of porphyry, which 

 forms the low ridge at Ainslie Post Office. These features are 

 shown in a general fashion in the coloured map by D. J. Mahony 

 and myself. (Report of Geological Reconnaissance, 1913.) 



There is nothing- unusual in the conditions in the Ainslie 

 Valley, save perhaps that the unbroken rampart of hard rocks 

 (see contours on figure 1) on each side indicates that the water 

 supply will be fairly reliable if ordinary geological precautions 

 are taken in sinking wells. 



Here, as everywhere, a large portion of the water sinks un- 

 derground through the porous surface soils, debris, gravel, talus 

 and alluvium generally, until it reaches the solid impervious 

 rock beneath. Both the formations here represented are of an 

 impermeable nature, i.e., the solid shales and solid porphyry. 



The water, on reaching this region, forms a more or less con- 



