AUSTRAL-AMERICAN REGIONS. 



107 



ingredients ; but in general, rapidly disintegrating, crumbling, yielding 

 to the rains, in some places decomposing in situ into banks of clay ; and 

 in one observed instance, from the breaking up of veins, forming a sort * 

 of pseudo-conglomerate. The easy slopes of the mountains seemed in 

 some degree due to the yielding character of the rock ; for in the nor- 

 mal granite of Brazil, almost every eminence presented inaccessible 

 surfaces. 



Beyond Coracovi, with the mountain-ridge, a trachytic or trap for- 

 mation commenced ; the rock being close-grained, full of fissures, easily 

 decomposable, and unattended, as ftir as I could discover, with any 

 marked change in the configuration of mountain-surfaces. This trap 

 formation extended to the limit of our excursion : but on the upper 

 portion of the Andes, there was a large intermixture of chlorite, of 

 jaspery aluminous rock, and according to Mr. Dana, of conglomerate. 



Climate. By astronomical calculation, April, the month in which 

 we arrived, should be the middle autumn month of the Southern 

 Hemisphere. The country was everywhere parched and brown ; 

 and of the thinly-scattered vegetable growth, the amiual plants and 

 most of the grasses were withered and dry. During our stay, the sun 

 was much of the time obscured by clouds, and never very powerful ; 

 woollen under-garments, usually oppressive in the daytime, proving 

 always grateful in the cool evenings. 



Rain fell in the night of the 22d, and in sufficient quantity to 

 render the road muddy during the forenoon of the following day; a 

 decided freshening at once became manifest in the vegetable growth. 

 This was the first rain of the season ; and according to the testimony 

 of residents, the rains at Valparaiso "are always light, and fixU almost 

 exclusively during the winter ; which is the season of flowers, and of 

 humming-birds, and the only part of the year when the hills are green." 

 At this time also, hnlhous-rooted plants may make their appearance. 

 The temperature was said " never to descend below 58° Fahr." 



One of the finest sunsets within my experience, I witnessed from 

 the heights back of Valparaiso; the tints less varied and less brilliant 

 than often at home ; but there was sombre grandeur in the heavy 

 clouds hanging in the East over massive mountains, the intervals 

 between revealing the far-distant Andes ; while, in looking West, down 

 upon the sea, the whole of its wide, expanse was changed in color to 

 deep reddish-purple. 



The aspect of the landscape and the growing plants indicated a cli- 



