56 LA TOUCHE: GEOLOGY OF WESTIRN R4JPUTANA. 



Proceeding southwards from this point one is struck on approach- 

 ing the hills near Meli, about three miles from the river, with their 

 rounded aspect as compared with the usual rugged character of the hills 

 composed of rhyolite, and on reaching the hills one finds that this 

 difference in appearance is due to a radical change in the composition 

 and texture of the rocks. The ridge which runs in a north-westerly 

 direction for about six miles from the village of Deora is in fact mainly 

 composed of a coarse granite, the microscopic constituents of which 

 are quartz, felspar and hornblende and no mica. This rock weathers 

 into rounded, exfoliating masses and frequently assumes somewhat 

 fantastic forms. The fragments that fall from the sides of the hills 

 formed of it are quickly broken down into a coarse sand, and the 

 bare sheets of granite rise abruptly from the plain, with no covering of 

 talus, such as is found on the slopes of the hills of rhyolite. 



The relations of the granite with the rhyolite are well 'seen in the 

 ridge immediately north-west of Meli, on its northern side. The 

 rhyolite occurs in patches at the base and here and there on the flanks 

 of the hill, sometimes running up to the crest, and generally dipping 

 to the north at angles corresponding with the slope of the surface of 

 the granite, as though the latter had been forced up from beneath as a 

 dome or boss, and thrust aside the sheets of lava above. The boundary 

 between the two is always perfectly abrupt, and the granite is evi- 

 dently intrusive. It sends off narrow veins into the rhyolite ramifying in 

 all directions through the latter. The granite of the veins is frequently 

 a coarse pegmatite, containing well shaped crystals of hornblende an 

 inch or more in length. Near the junction the joint planes of the 

 rhyolites are often covered with a thin glaze of granite, the latter 

 having evidently been-forced in among the rhyolites under great pres- 

 sure and in a very fluid state. The rhyolites here do not appear to 

 have been altered by the intrusion, but in other localities, to be noted 

 later on, signs of alteration are not wanting. Along the southern side 

 of the ridge the rhyolites are not exposed, probably having beeu 

 ( 56^ ) 



