chap. xiy. Section of the Uspallata Range. 529 



no doubt by the great accumulation of lavas and sedi- 

 ment, is also indicated. 1 



In nearly the middle of the range, there are some 

 hills [Q], before alluded to, formed of a kind of granite 

 externally resembling andesite, and consisting of a 

 white, imperfectly granular, feldspathic basis, including 

 some perfect crystals apparently of albite (but I was 

 unable to measure them), much black mica, epidote in 

 veins, and very little or no quartz. Numerous small 

 veins branch from this rock into the surrounding 

 strata ; and it is a singular fact that these veins, though 

 composed of the same kind of feldspar and small scales 

 of mica as in the solid rock, abound with innumerable 

 minute rounded grains of quartz : in the veins or dikes 

 also, branching from the great granitic axis in the pen- 

 insula of Tres Montes, I observed thab quartz was more 

 abundant in them than in the main rock : I have heard 

 of other analogous cases : can we account for this fact, 

 by the long-continued vicinity of quartz 2 when cooling, 



. * At first I imagined, that the strata with the trees might have 

 been accumulated in a lake : but this seems highly improbable ; for, 

 first, a very deep lake was necessary to receive the matter below the 

 trees, then it must have been drained for their growth, and afterwards 

 re-formed and made profoundly deep, so as to receive a subsequent 

 accumulation of matter several thousand feet in thickness. And all 

 this must have taken place necessarily before the formation of the 

 Uspallata range, and therefore on the margin of the wide level expanse 

 of the Pampas ! Hence I conclude, that it is infinitely more probable 

 that the strata were accumulated under the sea : the vast amount of 

 denudation, moreover, which this range has suffered, as shown by the 

 wide valleys, by the exposure of the very trees and by other appear- 

 ances, could have been effected, I conceive, only by the long-continued 

 action of the sea ; and this shows that the range was either upheaved 

 from under the sea, or subsequently let down into it. From the 

 natural manner in which the stumps (fifty-two in number) are grouped 

 in a clumjj, and from their all standing vertically to the strata, it is 

 superfluous to speculate on the chance of the trees having been drifted 

 from adj fining land, and deposited upright : I may, however, mention 

 that the late Dr. Malcolmson assured me, that he once met in the 

 Indian Ocean, fifty miles from land, several cocoa-nut trees floating 

 upright, owing to their roots being loaded with earth. 



2 See a paper by M. Elie de Beaumont, *Soc. Philomath.' May, 

 1839 (' L'Institut,' 1839, p. 161). 



