[Peoc. Roy. Soc. Victoria, 30 (N.S.), Pt. II., 1918]. 



Art. XVl. — Oii the Formation of "Natural Quarries" in 

 iSub-arid Western Australia.^ 



By J. T. JUTSON 



(Geological Survey of Western Australia). 



(With Plates XXVIII., XXIX.). 

 [Read December 13th, 1917]. 



Introductory. 



The sub-arid interior of Western Australia possesses many strik- 

 ing surface features, which are as yet but little kiTown, and still 

 less have been the subject of investigation. Amongst minor forms, 

 the remarkable hollows, to which the writer has applied the name, 

 " natural quarries," are worthy of record. They differ in origin 

 from, the natural quarries due to ice action ; and in normally moist 

 climates they have no definite parallel. Their nearest topographic 

 forms in such climates are certain scars left in places on steep 

 hillsides, owing to land-slips, but for reasons stated below such 

 an origin cannot be postulated for any of the quarries described 

 in this paper. 



Summary. 



" Natural quarries," in sub-arid Western Australia are of three 

 kinds, circular, rectangular and triangular. They are distinct 

 excavations (resembling artificial quarries) in the hillsides of 

 various rocks; and are chiefly due to the mechanical gouging or 

 lindermining action of rain under certain special conditions. 



Description. 



There are three kinds, broadly speaking, of natural quarries. 

 They may be described as the circular, the rectangular and the 

 triangular types, such terms being based on the kind of plane 

 figure formed by the outline of the quarry on the normal surface 

 slope. There is, however, a certain amount of transition between 

 the different forms. 



The Circular Quarry/. — This kind forms a more or less circular 

 hole of varying diameter and depth, on a hillside; and in many 



1 By permission of the Director of the Geological Survey of Western Australia. 



