other places quit-e even-grained and very dark and compact. 

 As one goes round the northern margin of the island, walking 

 eastwards from the end of the jetty, the first of these masses 

 is to be seen commencing from behind the tramshed, while the 

 other is encountered a little further along. The width of the 

 two masses together is about 60 yards. 



The first mass may be traced for some distance up the 

 slope in a southerly direction, but is soon lost; the other 

 passes up behind the harbour-master's house, and appears 

 again in a good strong section on the south side of the island. 

 Another section on the cliffs of the south side, but more to 

 the west, may be the continuation of the first mass, but the 

 capping of "travertine" and soil which covers the higher parts 

 of the island makes it difficult to trace the outcrops. 



Of the two sections seen on the north side of the island 

 the first, or more westerly, is the denser and finer in grain; 

 the other is rather more coarsely crystalline and richer in the 

 large felspar and quartz crystals. On the whole there is a 

 gradual increase from west to east in grainsize and in propor- 

 tion of large crystals. This is not maintained on the cliff- 

 sections on the south side of the island, where the rock is 

 moderately studded with phenocrysts, which are rather more 

 numerous near the contact with the granite and decrease 

 towards the centre of the mass. 



The field relations between the granite and the finer- 

 grained rock are such that the determination of relative age 

 is difficult. On the one hand, inclusions of the diorite are 

 found in the granite, like basic secretions; but on the other 

 hand, at the contact tongues of diorite are seen to penetrate 

 the granite and vict verm, so that at one time the diorite, at 

 another the granite, seems to be the intrusive rock. 



The boundaries of the two rocks are not sharply defined, 

 and this is best seen on the south side of the island. The 

 junction lines are frequently curved and twisted, and there is 

 a suggestion of blending, as if at the time of intrusion both 

 rocks had not been wholly solidified. No chilled contacts 

 were observed. 



At all events, whichever of the two was injected first, it 

 is certain that no great time-interval separated the acts of 

 intrusion, and the precise order is of no great moment. 



Both the granite and the quartz mica diorite are diver- 

 sified in places by veins and veinlets of pink aplitic rock. 



(2) ROSETTA HEAD. 



J'o/ phf/rific Granite. — This is similar to that of Granite 

 Island. 



