484 EEV. J. F. BLAKE ON THE 



nnless we assign, as is most natural, the granite to this epoch. The 

 granite is anterior to the conglomerate, and the diabase is posterior 

 to the granite, and, possibly, also to the conglomerate. This last 

 rock is the most interesting in the locality, since it is composed of 

 fragments not represented elsewhere in the district. This Ordo- 

 vician breccia contains many kinds of rocks, some almost approach- 

 ing red sandstone, and others like an unaltered portion of the 

 chloritic-schist group. The difficulty of assigning an early origin 

 to all these seems to have led the surveyors to suggest a Carbo- 

 niferous age for the conglomerate. However, to the east it passes 

 into typical Ordovician shales, and most of the materials could 

 probably be found in an extension of the South-Stack series. At 

 the northern end, by the lake, however, the fragments are of gneiss 

 and granite, and of other rocks such as we shall find within the 

 granitic area in the central district. We thus learn that a similar 

 group of rocks must have occurred here also, not far removed from 

 sight. In other words, the synclinal which separates the two dis- 

 tricts affects the lower rocks also, which are continuous across it 

 at some depth. 



Summary of the Western District. 



The rocks in this district commence at their base with a vast 

 development of quartzite, which more or less gradually changes, 

 through micaceous and gritty rocks, into laminated chloritic schists, 

 which are so sporadically metamorphosed as to remain in certain 

 places as purple slates. These, with occasional bands of grit and 

 isolated areas of sericitic schists, occupy a wide country to the east. 

 Into this is intruded a large mass of gabbro and serpentine, and 

 patches of limestone and of epidosite are occasionally found. The 

 upward continuation of the rocks on the north is diff'erent from 

 that on the south. In the former they pass continuously but rather 

 rapidly into a vast accumulation of unstratified tujff and ashes, 

 which increase in bulk as we go north, and ultimately come to a 

 climax by the development of agglomerates and the intrusion of 

 granite and felsite. In this volcanic material are found narrow 

 lenticular bands of limestone, with mosaic crystallization, and also 

 rounded upstanding knobs of quartz, which it is suggested are the 

 bases or pipes of ancient geysers. The metamorphism of the rocks 

 is very variable, in some much chlorite being developed. The 

 coarser material is often compressed into lenticles, forming a lenti- 

 cular pelite. The finer makes a mottled rock or marbled slate. 

 In the southern direction the volcanic material is absent, but the 

 chloritic schists pass up into a series of well-bedded rocks, including 

 two thick bands of quartzite. In some parts these rocks are in- 

 tensely cleaved, with foliation along the cleavage-planes ; in others 

 there is neither cleavage nor foliation, but in all there are vast 

 undulations and contortions, forming a synclinal on the whole. 

 They may be called the South-Stack series. At the extreme east of 

 the district a small mass of granite is found, overlain by the Ordo- 

 vician breccia, and not connected with the chloritic schists ; it is 



