BY W. N. BENSON. 547 



to the nature and distribution of the several types of rocks 

 developed. 



One of the most striking features is the presence of a large 

 amount of basic rock. This forms long intercalations scattered 

 throughout the Eastern Series as shown (diagrammatically) on the 

 Map(Platel.). These consist of tuffs, breccias, and spilitic rocks, 

 many of which, though more or less altered, are ver}- similar to 

 rocks occurring in the INJiddle Devonian Series. In the neigh- 

 bourhood of the granite, they have been changed, into amphi- 

 boUtes, the zone of metamorphism extending from half a mile to 

 a mile from the granite. This amphibolite occurs, for instance, 

 in the north-eastern corner of the Parish of Nemingha, inter- 

 calated with mica-schist, and other masses run southwards 

 through portion 155. Where the basic rocks cross the creek in 

 portions 147 and 190, they form several narrow bands of spilite 

 interstratified with jasper and chert. There is no clear evidence 

 of pillow-structure, but some suggestion of it. South of this, 

 spilite crosses Spring Creek as a thick band, partly schistose, 

 partly massive, with some trace of pillow-structure. It is inter- 

 sected by bands of jasper, and interstratified with highly crushed 

 banded cherts, and with tuff-breccias like those of the Middle 

 Devonian Series. 



South of the watershed of Spring Creek, is a sharp hill, marked 

 by a thicket of pine-trees. Here the rock is quite different, 

 partly a tuff-breccia, partly a rather de vitrified flow-breccia, of 

 which the brown glass contains crystals of quartz and altered 

 felspar, and pseudomorphs after felspar-augite. This zone of tuff- 

 breccia is of great width, and is interstratified with cherts. It 

 extends southwards across Oakey and Nemingha Creeks, in the 

 beds of which it is well exposed. Many masses of spilite occur 

 with some approach toward a pillowy structure, and intersected 

 by abundant veins of secondary c^hert. The basic breccia is 

 cemented into a uniformly resistant rock, which makes bold 

 rounded outcrops. 



A very perplexing hill is that east of the northern end of the 

 serpentine-belt. At its western base is a large mass of altered 

 basic rock, probably of Middle Devonian age. Above these are 



