DETAILED DESCRIPTIONS OF ROCKS. 63 



To the north of the hill at Siner there is another large mass of 

 the hornblendic granite, in the range a short distance west of the 

 village of Indrana. On the south-west side of the range the rhyolites 

 are in contact with the granite, but here the former dip directly 

 towards it, that is to the east-north-east at an angle of about 30 (Pi. 

 Ill, fig. 2). The junction of the granite and rhyolite is very well snown 

 on the western slope of the hill beneath the survey mark (1,346 feet). 

 The granite abuts vertically against the rhyolite and has thrown off 

 numerous veins into it ; in addition the granite has torn off large blocks 

 of the rhyolite and included them. 1 he rhyolite, near the contact with 

 the granite and in the included blocks, is considerably altered; and is 

 full of small nests of hornblende. The granite of the veins is usually 

 very coarse in texture, especially towards the middle of the vein, where 

 the hornblende crystals are frequently from 3 to 4 inches in length. 

 A good instance of the manner in which the granite veins penetrate the 

 rhyolites is seen at the western end of a detached mass of granite to 

 the south of the range (PI. IV, fig. 3}. A dyke of dolerite 12 feet wide 

 runs through the rhyolites from north to south, a short distance from 

 the boundary between the granite and rhyolite and parallel to it. 



The range a few miles further to the west and parallel to the In- 

 drana range is entirely composed of rhyolites. At the southern end 

 they exhibit good flow-structure and dip to the nort'i east at about 25 . 

 Further north are red rhyolites only slightly porphyritic. In the midst of 

 these there is a well defined band of breccias about 20 feet thick, which 

 can be traced to near the northern end of the range. Here the beds 

 are inclined to the east at about 30 . In a small detached hill to the 

 east of the middle of the range a thick band of much decomposed dia- 

 base, apparently interbedded with the rhyolites, is exposed ; it is over- 

 laid by green rhyolites with porphyritic crystals of bright red felspar. 



Some five or six miles to the south of Siwana is a very large mass 

 of hills, extending for nearly 17 miles from east to west and cbout 6 

 miles across in its broadest part, rising to an altitude of 3,199 feet 

 above the sea at its highest point, or about 2,500 feet above the plain. 



( 63 ) 



