80 The Sedimentary, Metamorphic, 



traces of schistose structure in a linear arrangement of the 

 minerals. It is composed of rounded crystals of triclinic 

 felspars and numerous angular grains of felspar and quartz ; 

 there are also magnesia-mica, chlorite, and small masses and 

 veins of pinite. The felspars are in preponderance. The 

 larger number are triclinic, and of first consolidation. Many 

 of them are extraordinarily worn and eroded. 



The chlorite is pale in colour, and but slightly dichroic, 

 and is the alteration-product of a brown magnesia-mica, 

 portions of which are still remaining. The quartz is the 

 residual constituent in very numerous interlocking grains. 



At 14 the schists become much distorted, and have coarse, 

 and also "fine-grained, crystalline-granular veins and folia- 

 tions, which in places preponderate over the schist itself. 

 From 14 to 15 there are no rocks visible in the stream, 

 but they reappear at 15, which is close to the ford. The 

 rocks at this place are very siliceous, grey or greenish-grey 

 coloured, often much contorted schists, showing minute 

 plates of a silvery alkali-mica here and there on the folia- 

 tions. They also contain crystalline-granular foliations, and 

 small masses of red felspar, quartz, and magnesia-mica, or 

 chlorite, and in places also plates of a silvery alkali-mica. 

 These schists are also crossed by strings and patches of quartz. 



I examined, both microscopically and chemically, a sample 

 of a schistose rock close to 15, and of which I have given a 

 rough sketch on Plate III., fig. 2. 



The schistose part is mainly composed of angular grains of 

 felspar, and still more angular grains of quartz, which fill in 

 all the spaces, and interlock with each other, like a puzzle-map. 

 Parts of the mass are occupied by pinite pseudomorphs, after 

 some mineral of which now not even the smallest unaltered 

 portion remains. The schistose structure of this rock is 

 marked by the winding, yet linear, arrangement of the 

 plates of mica (and its alteration to chlorite), and successive 

 patches of pinite, connected by veins of the same. The 

 felspars are of two kinds. One is simple, having the appear- 

 ance of orthoclase, and a good deal altered to mica and 

 pinite ; the other is a triclinic felspar, of an appearance 

 suggesting oligoclase, as do also its low angles of obscuration, 

 of which I obtained several measurements. 



The mica is in small, ragged-sided crystals, and, so far as 

 one can judge from its colour, and from the pale and only 

 slightly dichroic chlorite which results from its alteration, it 

 is a magnesia-mica, in which that base preponderates over iron. 



