BY W. N. BENSON. 573 



Between Munro's Creek and Hanging Rock, the rocks west of 

 the serpentine are more slatey, are more or less altered by the 

 magmatic waters associated with serpentine-intrusion, and are 

 greatly disturbed. Some cherty bands and spilites are present 

 here. North of Bowling Alley Point, the same cherty claystones 

 are developed, notably in the knoll that rises from among the 

 Permo-Carboniferous rocks on the Peel River, but are less well 

 marked north of the stream. Small lenses of limestone occur, 

 but rarely. They have been seen on Munro's Creek, but have 

 not yet been found to contain radiolaria. They are only a few 

 inches in width. The maximum thickness of this series is about 

 six hundred feet. 



(6). The Lower Bowling Alley Tuffs and Breccias extend from 

 Chrome Hill across the river to the limestones. Making due 

 allowance for the numerous intrusions of dolerite (but none for 

 possible strike-faulting), they seem to be about 4,000 feet thick. 

 The rock is chiefly a grey -green, felspathic tuff, in which the con- 

 stituent fragments are scarcely more than one-quarter of an inch 

 in diameter, but occasionally it is more coarsely grained, becoming 

 a regular breccia, with angular fragments of chert several inches 

 in length. It consists chiefly of fragments of radiolarian chert, 

 and finely divided igneous material, chiefly chips of spilite, and 

 crystals of plagioclase, augite, and iron-ores ; quartz is less 

 frequent. The rocks are often extremely indurated, and, on 

 weathering, the constituent fragments, or sometimes the cement, 

 are brought out in high relief by natural etching. 



Here and there, throughout the series, are subordinate layers 

 of banded, cherty claystone. Flows of spilite are present, and, 

 in particular, may be noticed the mass that forms the prominent 

 crag, White Rock, that overlooks Munro's Creek (Plate xxiii.). 

 Nevertheless the rock does not appear so abundant as in the 

 upper series. 



A hard, black, basalt-like band near the 'Possum Mine, Bowl- 

 ing Alley Point, has proved to be a peculiarly even-grained, basic 

 tuff. 



(c). The limestones form a series of long or short lenses, ex- 

 tending the whole length of the area (twelve miles). While 



