BY C. A. SUSSMILCH AND H. I. JKNSEN. 167 



Youiig Man Canobolas, and two of the Bald Hills; they form the 

 bulk of Watt's Pinnacle, and almost entirely encircle the central 

 area of acidic rock. The distribution of these lavas, with their 

 associated tuffs, indicates a central point of eruption, somewhere 

 adjacent to what is now called the Devil's Hole. This valley 

 itself has somewhat the appearance of a huge crater, but is pro- 

 bably a valley of denudation. The plugs of solvsbergite which 

 occur at the top of the Young Man Canobolas and on The Pinnacle, 

 are the probable vents from which this series was erupted. 



All the tuffs so far observed are associated with the melano- 

 cratic trachyte-lavas. The following section taken from the 

 divide between the head-Avaters of Summer Creek and Cadianju- 

 long Creek, immediately south from Plowman's Farm, shows three 

 distinct beds of tuffs. 



The lowest bed, which rests directly upon the comendite, is 

 somewhat fine-grained, and contains numerous fragments of 



VERTICAL r 



SCALE ° ^ 12 3obFEET 



Fig.2. — Section at Cadianjulong Creek, showing tuffs and lavas. 



comendite. The upper beds are much coarser, and contain 

 ejected blocks of all sizes. About 2 miles further south, on the 

 Cadianjulong Creek, a tuff-bed, 340 feet thick, occurs, as shown 

 in the accompanying sketch (fig.2). 



