chap. xt. Section up the Valley. 541 



This formation is intersected by numerous metal- 

 liferous veins, running, though irregularly, NW. and 

 SE., and generally at right angles to the many dikes. 

 The veins consist of native silver, of muriate of silver, 

 an amalgam of silver, cobalt, antimony, and arsenic, 1 

 generally embedded in sulphate of barytes. I was 

 assured by Mr. Lambert, that native copper without a 

 trace of silver has been found in the same vein with 

 native silver without a trace of copper. At the mines 

 of Aristeas, the silver veins are said to be unproductive 

 as soon as they pass into the green strata, whereas at 

 S. Rosa, only two or three miles distant, the reverse 

 happens ; and at the time of my visit, the miners were 

 working through a red stratum, in the hopes of the 

 vein becoming productive in the underlying green sedi- 

 mentary mass. I have a specimen of one of these green 

 rocks, with the usual granules of white calcareous spar 

 and red oxide of iron, abounding with disseminated 

 particles of glittering native and muriate of silver, 

 yet taken at the distance of one yard from any 

 vein, — a circumstance, as I was assured, of very rare 

 occurrence. 



Section Eastivard, up the Valley of Coquimbo. — 

 After passing for a few miles over the coast granitic 

 series, we come to the porphyritic conglomerate, with 

 its usual characters, and with some of the beds dis- 

 tinctly displaying their mechanical origin. The strata, 

 where first met with, are, as before stated, only slightly 

 inclined ; but near the Hacienda of Pluclaro, we come 

 to an anticlinal axis, with the beds much dislocated and 

 shifted by a great fault, of which not a trace is ex- 

 ternally seen in the outline of the hill. I believe that 

 this anticlinal axis can be traced northwards, into the 



1 See the Eeport on M. Domeyko's account of these mines, in 

 the * Comptes Kendus,' t. xiv. p. 560. 



