BY C. A. SUSSMILCII AND H. I. JENSEN. 169 



flow of lava, on the highest point of which the Trigonometrical 

 Station now stands. South of the neck the beds of scoriae 

 dip first northerly towards the neck, and then qua-qua-versally 

 chiefly from west towards south at an angle of 20° up to 40", as 

 far as the western edge of the mountain, where the scorise pass 

 into a coarse volcanic agglomerate composed chiefly of large 

 pieces of cellular andesitic lava." 



The writers of this paper were unfortunate on the day they 

 visited the Old Man Canobolas, in meeting with dense mists and 

 heavy rain, which made a detailed examination impossible. They 

 saw enough, however, to satisf}-- themselves of the general 

 correctness of Prof. David's views. One of the best outcrops of 

 these andesites can be seen at the Hopetoun Waterfall, where 

 one of the flows is over 100 feet thick; good outcrops also occur 

 in the road-cuttings on the Towac Road, near the Canobolas 

 Public School. 



The decomposition of the andesites gives rise to excellent soils 

 for agricultural and fruitgrowing purposes, as evidenced from 

 some of the farms and orchards which occur on the andesite soils 

 along the Towac Road. 



(c/) The Basalts. — These are typical compact olivine-basalts, 

 and frequently exhibit columnar structure. An examination of 

 the accompanying map will show that they completely encircle 

 the Canobolas Mountains, and occur at and about the 3000 feet 

 level. Nowhere do they occur on any of the high hills, the 

 highest point to which we succeeded in tracing them being 3300 

 feet, on Summer Creek (Molong Creek). Their distribution 

 and occurrence suggest that they were poured out from fissures 

 in the sides of the mountains, flowed into and submerged many 

 of the shallow mature valleys of the tableland, and spread out 

 over the tableland-level, extending to many miles beyond the 

 limits of the area mapped. 



2. D y k e s and Necks. 



{a) Dykes. — These are not abundant. A biotite-trachyte dyke 

 (X.613) outcrops on the saddle between the Old and Young Man 



