BV \\. N. BENSON. 357 



prisms of hornblende alsu occur, with fibrous extensions, and 

 rarely large grains of magnetite. 



The Penno-Curbonij'crous Sandstones. 

 Nothing need be added to what has already been published con- 

 cerning these rocks (3, pp. 586-7) save in regard to their relation 

 to the faulting, which is discussed in a later section (p. 360). 



Tertiary Basalt. 



The occurrence of the Tertiary basalt is confined to a few locali- 

 ties. It is found only in necks and dykes. The largest neck is» the 

 mass of Black Jack itself, a roughly circular area of basalt in 

 which a thickness of about 300 feet of this rock are exposed. 

 There is absolutely no sign of underlying gravels, and the varying 

 height of the lower limit of the exposed basalt seems to depend on 

 the relation of the surface-topography to the margin of a vertical 

 column of rock. Half a mile to the north is another small plug of 

 basalt cutting through tlie limestones. This is only 100 yards in 

 diameter. A third occurs near the mouth of Hyde's Creek (5, 

 p. 172). 



Finally, a small dyke of basalt has been noted near the head of 

 Reedy Creek, running in a direction parallel 1o tlie trend of the 

 dip-faults. These are (piite normal olivine-basalts, ccjiicerning 

 which no special petrological features are Avorthy of record. 



Becettt Drift and Allaviam. 



These terms are employed in the same sense as before (6, 

 l)p. 590-51)2). The greatest accunudation of drift is in the large 

 Hat near the head of Reetly Creek, a topograpliic feature Avhose 

 significance is not quite clear. The alluvium of the flood-plain of 

 the main river includes about eleven feet of loam lying above 

 gravel, which, in the single test known to the writer, reached a 

 thickness of thirty feet. The thickness of tlie upper stratum of 

 loam is subject to rapid variation. ;Mr. R. H. Dowe informed the 

 Avriter that in Portion 59, a fence four feet in height was com- 

 pletely covered in twenty-five years, while nearby, in the hole left 

 by a tree which had burnt down to the roots, it was obvious that 



