452 Transactions.— Geology. 
termed schistose. The various mineral layers blend into each other, and 
are composed chiefly of quartz, felspar, mica, and tale or chlorite, while 
veins of quartz ramifying through clay, slate, or other non-siliceous rock, 
render them convertible into argillaceous mica-schist or phyllite, mica-schist, 
granulite; or less siliceous kinds, forming talc, chlorite, hornblende, or 
actinolite-schist, or schorl rock. 
Schistose structure has been found also to be occasionally produced in 
lavas, the vesicles in which have been compressed and attenuated in the 
direction of flow (Rutley, Q.J.G.S., vol. xxxvi., p. 285). 
A further alteration of these rocks takes place into gneiss, which has a 
schistose structure, the quartz, felspar, and mica, and often hornblende, of 
which it is composed, being arranged in layers, the foliation constituting 
the chief difference from granite. Gneiss, and schistose rocks, with inter- 
calated beds of crystalline limestone, form the laurentian rocks of Canada. 
The schist containing beds of graphite, or unoxidized carbon and apatite, 
(Dawson, Q.J.G.8., vol. xxxii., p. 285), denotes plant, and the limestone, - 
animal life. Graphite occurs also at Pakawau, in Nelson, under similar con- 
dition in metamorphosed strata, and its presence denotes that no extreme 
temperature was attained during metamorphosis of the rock. 
Gneiss has been found in many cases to merge into granite, so that the 
extreme of metamorphism may be regarded as granite, the fundamental 
rock throughout our earth; and its massive crystalline texture and its 
chemical combination of elements, namely, quartz, felspar and mica, must 
now be regarded as the ultimate crystalline condition, under great pressure, 
of sedimentary strata, either by slow consolidation after having been con- 
verted into a molten state, or by gradual chemical and structural change. 
The quartz in granite often has cavities and enclosures of other minerals, 
principally rutile and chlorite; these cavities generally contain pure water, 
oceasionally liquid carbonic acid, or a solution of chloride of sodium; 
they also contain bubbles, or rather vacuous spaces which show the ¢on- 
traction which the imprisoned fiuid has undergone during the cooling of 
the rock. Dr. Sorby and others have endeavoured to caleulate the amount 
of pressure shown by these contractions in volume. Spaces or beads of 
glassy or amorphous quartz, also occur, which denote that the quartz had 
first become viscous, and in consequence solidified without erystallizing- 
The liquefaction proved by the liquid cavities to have ‘once been the eondi- 
tion of granite, has caused it in places to burst through adjacent rocks in 
an eruptive manner, when disturbed perhaps | is * an — pressure, 
_ While other portions —— adua blend . into schi - . ae 
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