HY W. N. BENSON. 573 



veins of red jasper, and hsematitic chalcedony. In microscopic 

 structure, the rocks have many of the features of the kerato- 

 phyres in the breccias of the Gap Hills. When traced north- 

 wards, the keratophyre becomes mixed with breccia, and coarse 

 agglomerates, containing large boulders of a magnetite-kerato- 

 phyre-porphyrite, while the northern extremity of the complex 

 is a mass of coarse agglomerate, 100 yards wide, mixed with 

 intrusions(l) of vesicular hsematitic keratophyre, and large intru- 

 sions of massive keratophyre-dolerite, beside which is a large 

 mass of the porphyrite. Brecciated jasperised chert occurs on 

 either side of this. It would seem that, in this area, the intru- 

 sion of keratophyric dolerite and porphyrite was followed by a 

 disruptive invasion of keratophyre, which broke up or brecciated 

 the massive rocks, and emitted siliceous and ferruginous solu- 

 tions, which jasperised the surrounding cherts. 



Less than 200 yards south of this complex, is yet another 

 feature of the igneous activity of no less interest, though differing 

 greatly from the above. A band of apparently normal tuffaceous 

 rock, at least 500 yards long, runs through Portion 162, ISTe- 

 mingha. It contains numerous small pebbly inclusions at the 

 northern end, which are either angular or rounded and smooth 

 as if waterworn. As we follow the band southwards, the pebbles 

 increase in size until the tuff is full of large boulders, often 

 beautifully smooth and rounded, sometimes as much as a foot in 

 diameter. These pebbles often fall easily out of their matrix, 

 and one would scarcely doubt, from the inspection of a pebble so 

 isolated, that its shape was due to water-erosion. South of the 

 point where the pebbles reach their maximum size, they diminish 

 rapidly, and in oO yards they decrease to their original diameter 

 of less than an inch, and the tuff-band continues thus across the 

 road to the south without any interruption. The distance from 

 the northern to the southern point where the pebbles are not 

 more than half an inch in diameter, is scarcely 200 yards. On 

 either side of this band, which reaches a thickness of 30 yards, 

 is normal, undisturbed, tine-grained, banded chert. There is a 

 clear affinity, in lithological character, between the tuff-matrix 

 and the inclusions. With a few exceptions, the boulders, though 



