cnAP. xiv. Central Chile. 471 



quartzose and jaspery rocks, the latter occasionally 

 assuming the character of the basis of clay-stone por- 

 phyry : trap-dikes are numerous. Nearer the Cordillera 

 the ranges (such as those of S. Fernando, the Prado, 1 

 and Aconcagua) are formed partly of granitic rocks, 

 and partly of purple porphyritic conglomerates, clay- 

 stone porphyry, greenstone porphyry, and other rocks, 

 such as we shall immediately see form the basal strata 

 of the main Cordillera. In the more northern parts of 

 Chile, this porphyritic series extends over large tracts 

 of country far from the Cordillera ; and even in Central 

 Chile such occasionally occur in outlying positions. 



I will describe the Campana of Quillota, which 

 stands only fifteen miles from the Pacific, as an instance 

 of one of these outlying masses. This hill is conspicuous 

 from rising to the height of 6,400 feet : its' summit 

 shows a nucleus, uncovered for a height of 800 feet, of 

 fine greenstone, including epidote and octahedral mag- 

 netic iron ore ; its flanks are formed of great strata 

 of porphyritic clay-stone conglomerate, associated with 

 various true porphyries and amygdaloids, alternating 

 with thick masses of a highly feldspathic, sometimes 

 porphyritic, pale-coloured slaty rock, with its cleavage- 

 laminae dipping inwards at a high angle. At the base 

 of the hill there are syenites, a granular mixture of 

 quartz and feldspar, and harsh quartzose rocks, all be- 

 longing to the basal metamorphic series. I may ob- 

 serve that at the foot of several hills of this class, where 

 the porphyries are first seen (as near S. Fernando, the 

 Prado, Las Vacas, &c), similar harsh quartzose rocks 

 and granular mixtures of quartz and feldspar occur, as 

 if the more fusible constituent parts of the granitic 

 series had been drawn off to form the overlying por- 

 phyries. 



1 Meyen, ' Reise urn Erde,' Th. 1, S. 235. 



