328 Transactions. 



The rocks are traversed by numerous nearly vertical foliation-planes, 

 which divide them up into layers of varying thickness. The joints have 

 been mistaken for bedding-planes by previous investigators, who have 

 recorded a dip varying from 84° to vertical. 



There is another outcrop of the rocks further up the harbour, at 

 Green Point, but here they are less metamorphic. They strike west- 

 north-west to east-south-east. 



The rocks are readily divided into two main kinds. One is a coarse 

 dark-coloured rock consisting, as may be seen in the hand-specimen, 

 almost entirely of hornblende. It forms the basic class of this paper. 

 In the other rocks hornblende is also apparent, but no well-formed 

 crystals may been seen in hand-specimens, as the rocks are much finer 

 grained and more schistose in character. They form the acid class in 

 this paper. 



Glass I. — Acid Metamorphic Rocks. 



These rocks vary much macroscopically in the amount of hornblende 

 and biotite, but under the microscope all prove to be varieties of horn- 

 blende scist. 



1. Hornblende, Schist. 



Two complete series of sections were made from varieties of rock 

 obtained by crossing the strike at right angles. Series A was obtained 

 along the line marked AB on the map (fig. 2). Series B was obtained 

 along the line CD. 



Notes of the microscopical examination of series A are appended. 



A 1. - -Low-water mark, 157 ft. from high-water mark. Feldspar 

 phenocrysts fairly abundant; cloudy and decomposed; some contain 

 needles of hornblende. Hornblende in small crystals; especially nume- 

 rous in the vicinity of feldspars; parallel arrangement. A little biotite. 

 Grains of quartz, magnetite, and feldspar form groundmass. 



A 2.-97 ft. Much the same as A 1. 



A 3. — 67 ft. Phenocrysts of feldspar, some showing Carlsbad twin- 

 ning, decomposing as in A 1 and A 2. Increase of hornblende relative 

 to feldspar compared with A 1 and A 2. A little epfdote. Groundmass 

 as before. 



A 4. — 37 ft. Hornblende still more prominent. Feldspar phenocrysts 

 much smaller and more decomposed. Schistose structure marked. 

 Magnetite abundant in groundmass. 



A 5. - - 7 ft. Hornblende dominant; longitudinal axes of crystals 

 parallel. No phenocrysts of feldspar. Magnetite abundant. A little 

 epidote. Groundmass grains of feldspar and quartz, feldspar pre- 

 dominant. 



A 6. — High-water mark. Rock chiefly hornblende. Schistose struc- 

 ture perfectly shown. One section showed remains of a feldspar pheno- 

 cryst. Grains of feldspar, quartz, and magnetite, and other accessories 

 between crystals of hornblende. 



As will be seen from the map, the B series is actually a continuation 

 of the xV series. It is not necessary to describe the rocks in detail. They 

 are perfectly schistose in structure. Half the rock is hornblende. There 

 are no phenocrysts of feldspar, but the grains of quartz and feldspar 

 in the groundmass are clear, as though due to recrystallization. Biotite 

 is more abundant. 



Summing up the results of the examination of this series of rocks, 

 we find that — (1) the phenocrysts of feldspar are more and more broken 



