DETAILED DESCRIPTIONS IF ROCKS. 71 



and the granite is not seen anywhere in contact with the rhyolites. 

 A number of smali isolated hills of a similar granite occur scattered 

 over the plain to the souh-west in the direction of Jalor. In one of 

 these, near the village of Sakarna, 5 miles east of Jalor, a large 

 mass of rhyolite is seen running through the granite like a dyke, and 

 at first sight apDarently intrusive in it. It is, however, traversed by 

 veins from the granite, and is evidently a mass of rhyolite that has 

 been split off and imbedded in the granite. The rhyolite has ap- 

 parently been partially remelted at the edges, for a fluidal structure 

 following the irregularities of the boundary has been developed in it 

 and it has lost its dark colour for about half an inch from the junction. 



'I he granite of these hills is sometimes traversed by dykes of diabase 

 running from west-north west to east-south-east. One of these, at the 

 southern end of the hill at Godhan, near Sakarna, is about 50 feet wide. 



The large hill on which the fort at Jalor is built, and the greater 

 portion of the hill called Roza, to the west of the fort, is formed of 

 the same granite. The western part of Roza hill, however, consists 

 of Malani rhyolites, which rest upon the granite and dip away from it. 

 The boundary between the two is everywhere concealed by talus and 

 scrub jungle, but it appears to run nearly north and south along the 

 ridge, rising to 2,< 18 feet on the west side of Roza hill. The rhyolite 

 also appears in the two isolated hills west of Tarwa, about seven miles 

 west of Jalor, and in the more northerly of the two is in contact with 

 granite. Here the latter is clearly intrusive, sending off large dyke-like 

 masses among the rhyolites. A small hill of rhyolite also occurs to the 

 north, on the right bank of the Joai river, near the village of Saparo. It 

 seems likely that the rhyolites underlie most of the plain, and may 

 extend to the north-west to the large mountains south of Siwana, and 

 that the granite forms bosses protruded through them. Except where 

 these isolated hills appear above the plain, however, the ground is 

 entirely covered with blown sand. 



In the neighbourhood of Jalor the granite is traversed by several 



( 71 ) 



