449 



ages yielded more than 13,000 marks of gold 

 annually to commerce. This alluvial zone is 

 from 10 to 12 leagues broad : it attains its maxi- 

 mum of riches between the parallels of 2° and 

 6° of latitude, is sensibly impoverished towards 

 the north and south, and almost entirely disap- 

 pears between H° of north latitude and the 

 equator. The auriferous soil fills the basin of 

 Cauca, as well as the ravines and plains on the 

 west of the Cordillera of Choco ; it rises some- 

 times nearly 600 toises above the level of the 

 sea, and descends at least 40 toises # . Platina 

 (and this geognostic fact is worthy of atten- 

 tion), has hitherto been found only on the west 

 of the Cordillera of Choco, and not on the east, 

 notwithstanding the analogy of the fragments 

 of rocks, of greenstone, phonolite, trachyte, and 

 ferruginous quartz, of which the soil of the two 

 descents is composed. From the ridge of Los 

 Robles, which separates the table-land of Al- 

 maguer from the basin of Cauca, the western 

 chain forms, first, in the Cerros of Carpinteria, 

 east of the Rio San Juan de Micay, the continua- 

 tion of the Cordillera of Sindagua, broken by 

 the Rio Patias ; then, lowers towards the north, 

 between Cali and Las Juntas de Dagua, to from 



* M. Caldas assigns to the upper limit of the zone of gold 

 washings, only the height of 350 toises. {Seman., Tom. i, 

 p. 18) ; but I found the lavaderos of Quilichao, on the north 

 of Popayan, 565 toises high. (Astron. Obs., Vol. i, p. 303.). 



VOL. VI. 2 H 



