The. Petrography of the Fundamental Gneusone Complex. 43 



numerous extruded grains of magnetite, a little enstatite, some 

 bronzite, many plates of brown biotite secondary from the pyroxenes, 

 some large granules of magnetite, and a few prisms of apatite. The 

 rock is traversed by minute cracks filled with serpentine. It is a 

 galjbro or a biotite-gabbro. 



Near the foot of the rapids somewhat to the west of the preceding 

 rock, but in the same belt, a dark-grey rock of specific gravity 3-08 

 occurs. This rock shows in places a transition from a massive to a 

 foliated structure. A slide showing the transition from one into the 

 other was prepared, and it showed that the rock consists of a mosaic 

 of granules of feldspar, both striated and water-clear, in one part of 

 which are masses cf colourless augite with man}" extruded gi-ains of 

 magnetite, while in the other part the p5"roxenes are more or less 

 replaced by a green hoi-nblende, having hei-e and there kernels of a 

 ferriferous enstatite, whilst extruded magnetite forms large irregular 

 granules. Some granules of magnetite, with borders of leucoxene, are 

 also present in both parts. The part which contains the augite altered 

 to hornblende has a perceptibly foliated structure. 



At the foot and middle of the rapid specimens were obtained 

 of a schistose dark-coloured variety of the I'ock, of specific gravity 

 2-97, having the following structure : — 



Areas of labradorite in laths, with well-defined edges, in parts 

 showing the commencement of granulitisation, in others broken up 

 into aggregates of small granules ; large patches of green horuljlende, 

 some with very abundant extruded grains of magnetite, and with 

 numerous small kernels of augite, many scattered small crystals of 

 hornblende, some patches of zoisite and some grains of epidote. The 

 greater part of the rocks exposed at the rapids consists of this variety. 



Near the head of the falls is a belt of a well-foliated variety, dark-grey 

 in colour, and of specific gravity 2-81. This rock is made up of a 

 mosaic of granules of water-clear feldspar, and of masses of green 

 hornblende, more or less broken up into granules, and in places partly 

 altered to chlorite. Epidote is present in small granules in some 

 abundance. Small flakes of chlorite after biotite are also found. 

 Grains of magnetite occur scattered here and there through the rock. 

 It possesses a well-marked fissile structure. 



The series of specimens collected below and at the Upper Mariwa 

 Rapids, show very clearly the passage of rather fine-textured gabbro 

 into epidote-hornblende-schist. 



rrot''r abase. — On the southern peak of the Blue Mountain Hills, 

 at an altitude of about 700 feet, a dark -coloured, compact rock, having 

 a specific gravity of 3'0, occurs. It is made up of plates of nearly 

 colourless augite changed at their periphei'ies to pale-green horn- 

 blende ; in places there are patches of hornblende which show no 

 indications of pyroxene, but, as a rule, even in the more altered parts, 

 more or less of the original augite remains as kernels in the masses of 

 hornblende. In the less altered augite plates the eflects of strain are 

 well marked. The ferro-maij;nesian minerals occur in an ill-defined 



