574 



Copiapo. 



past n. 



zontal elevation has been in the district of Copiapo 

 about 10,000 feet. 



In the valley of the Despoblado, the stratification, 

 as before remarked, has been much disturbed, and in 

 some points to a greater degree than I have anywhere 

 else seen. I will give two cases : a very thick mass of 

 thinly stratified red sandstone, including beds of con- 

 glomerate, has been crushed together (as represented 

 in the woodcut) into a yoke or urn-formed trough, so 

 that the strata on both sides have been folded inwards : 

 on the right hand the properly underlying porphyritic 

 claystone conglomerate is seen overlying the sandstone, 

 but it soon becomes vertical, and then is inclined to- 

 wards the trough, so that the beds radiate like the 



No. 40. 



spokes of a wheel : on the left hand, the inverted por- 

 phyritic conglomerate also assumes a dip towards the 

 trough, not gradually, as on the right hand, but by 

 means of a vertical fault and synclinal break ; and a 

 little still farther on towards the left, there is a second 

 great oblique fault (both shown by the arrow-lines), 

 with the strata dipping to a directly opposite point: 

 these mountains are intersected by infinitely numerous 

 dikes, some of which can be seen to rise from hummocks 

 of greenstone, and can be traced for thousands of feet. 

 In the second case, two low ridges trend together and 

 unite at the head of a little wedge-shaped valley; 



