366 AMAZONIA AND LA PLATA. 



liills, where have been accuuiulated prodigious quantities of débris from the 

 moraines left by the old glaciers at the entrance of the plains. 



The finer particles, raised by the winds in clouds of dust, are wafted to great 

 distances and strewn over the surface in layers of sund analogous to the "yellow 

 earth " of Central China. But the coarser sands form veritable dunes, "land 

 waves," so to say, heaving and falling under the pressure of the aerial currents. 

 In the region of the Colorado and Rio Negro especially these formations oi^cupy 

 vast spaces, stretching nearly across the whole width of the Continent. Acting 

 in the same way as the dunes of oceanic origin, they are arrested under the 

 influence of the rains, and resume their slow forward movement during the dry 

 periods. They are often solidified and transformed to hills gradually covered 

 with a vegetable humus by the binding action of plants with long trailing 

 rootlets and branches. Certain species of trees with strong roots, such as the 

 aJgarrohos, continue to thrive in the midst of the moving sands by which they 

 have been overtaken. 



The eruptive craters of the Andes also contribute to change the aspect of the 

 Patagonian lands. The whole of the E-ios Chubut and Santa Cruz basins have 

 been covered with ashes of diverse colours, which are deposited in regular layers, 

 and which are evidently erupted matter ejected by the volcanoes of the Cordilleras, 

 and wafted to great distances by the western and north-western winds. 



In 1886 a great shower of such volcanic dust rained over the whole of the 

 Santa Cruz valley, on the surrounding heights, and even reached Punta Arenas. 

 In some districts travellers found it difficult to breathe, and could scarcely discern 

 objects ten yards off. Many animals perished for want of water and fodder, 

 springs and pasturage having disappeared beneath the layer of ashes. For a time 

 the Santa Cruz itself ceased to flow, and then suddenly rose to a great height, 

 doubtless having burst the temporary dam formed by the volcanic débris. In 

 1893 the Chilian volcano, Calbuco, supposed to be extinct, ejected scoriaî as fur 

 as the mouth of the Chubut and Nuevo Bay. So rapidly had the clouds of ashes 

 traversed the vast distance that they fell while still warm, covering the navigation 

 as if with a mantle of snow. 



Despite their generally dreary and monotonous aspect, the Patagonian steppe 

 lands seem to produce a strange, fascinating impression on all observers. " In 

 calling up the images of the past," writes Charles Darwin, " I find the plains of 

 Patagonia frc quently cross before my eyes ; yet these plains are pronounced by 

 all to be most wretched and useless. They are characterized only by negative 

 possessions ; without habitations, without water, without trees, without mountains, 

 ihey support only a few dwarf plants. Why then — and the case is not peculiar 

 to myself — have these arid wastes taken so firm possession of my mind ? Why 

 have not the still more level, the greener, and more fertile pampas, which are 

 serviceable to mankind, produced an equal impression ? 



" I can scarcely analyse these feelings, but it must be partly owing to the free 

 scope given to the imagination. The plains of Patagonia are boundless, for they 

 are scarcely j)racticable, and hence unknown. They bear the stamp of having 



