THE VOYAGE OF THE BEAGLE 57 



covered by thickets, and on the banks of the larger streams, 

 especially to the north of Las Minas, willow-trees are not 

 uncommon. Near the Arroyo Tapes I heard of a wood of 

 palms; and one of these trees, of considerable size, I saw 

 near the Pan de Azucar, in lat. 35. These, and the trees 

 planted by the Spaniards, offer the only exceptions to the 

 general scarcity of wood. Among the introduced kinds may 

 be enumerated poplars, olives, peach, and other fruit trees: 

 the peaches succeed so well, that they afford the main supply 

 of firewood to the city of Buenos Ayres. Extremely level 

 countries, such as the Pampas, seldom appear favourable to 

 the growth of trees. This may possibly be attributed either 

 to the force of the winds, or the kind of drainage. In the 

 nature of the land, however, around Maldonado, no such 

 reason is apparent; the rocky mountains afford protected 

 situations, enjoying various kinds of soil; streamlets of 

 water are common at the bottoms of nearly every valley; 

 and the clayey nature of the earth seems adapted to retain 

 moisture. It has been inferred with much probability, that 

 the presence of woodland is generally determined 2 by the 

 annual amount of moisture; yet in this province abundant 

 and heavy rain falls during the winter; and the summer, 

 though dry, is not so in any excessive degree. 3 We see nearly 

 the whole of Australia covered by lofty trees, yet that coun- 

 try possesses a far more arid climate. Hence we must look 

 to some other and unknown cause. 



Confining our view to South America, we should certainly 

 be tempted to believe that trees flourished only under a very 

 humid climate; for the limit of the forest-land follows, in a 

 most remarkable manner, that of the damp winds. In the 

 southern part of the continent, where the western gales, 

 charged with moisture from the Pacific, prevail, every island 

 on the broken west coast, from lat. 38 to the extreme point 

 of Tierra del Fuego, is densely covered by impenetrable for- 

 ests. On the eastern side. of the Cordillera, over the same 

 extent of latitude, where a blue sky and a fine climate prove 

 that the atmosphere has been deprived of its moisture by 

 passing over the mountains, the arid plains of Patagonia 



2 Maclaren, art. " America," Encyclop. Britann. 



3 Azara says, " Je crois que la quantite annuelle des pluies est, dans 

 toutes ces contrees, plus considerable qu'en Espagne." Vol. . p. 36- 



