II 



ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



shore, near the mouth of the estuary of the Plata. These countries consist 

 either of an undulating surface, clothed with turf, or of perfectly level plains with 

 enormous beds of thistles. Except on the banks of the rivers, trees nowhere 

 grow ; there are, however, thickets in some of the valleys, in the more hilly parts of 

 Banda Oriental. During the winter and spring of this hemisphere, a considerable 

 quantity of rain falls, and the plains of turf are then everywhere verdant ; but in 

 summer the country assumes a brown and parched appearance. 



Bahia Blanca forms a large bay, in latitude 39° S. on a part of the coast, 

 which falls within the territory of the province of Buenos Ayres, but which from 

 its physical conditions would more properly be classed with Patagonia. The ter- 

 tiary plains of Patagonia, extend from the Strait of Magellan to the Rio 

 Negro, which is commonly assumed as their Northern boundary. This space 

 of more than seven hundred miles in length, and in breadth reaching from the 

 Cordillera to the Atlantic Ocean, is everywhere characterised by the dreary 

 uniformity of its landscape. Nearly desert plains, composed of a thick bed of 

 shingle, and often strewed over with sea-shells, (plainly indicating that the land 

 has been covered within a recent period by the sea,) are but rarely interrupted by 

 hills of porphyry, and other crystalline rocks. The plains support scattered tufts 

 of wiry grass, and stunted bushes ; whilst in the broad flat-bottomed valleys, dwarf 

 thorn-bearing trees, barely ornamented with the scantiest foliage, sometimes unite 

 into thickets ; and here the few feathered inhabitants of these sterile regions resort. 

 There is an extreme scarcity of water ; and where it is found, especially if in lakes, 

 it is generally as salt as brine. The sky in summer is cloudless, and the heat 

 in consequence, considerable ; whereas the frosts of winter are, sometimes, severe. 

 The principal localities visited by the Beagle, were the Rio Negro, in latitude 

 41° S., Port Desire, Port St. Julian, and Santa Cruz. At the latter place, a 

 party, under the command of Captain FitzRoy, followed up the river in boats, to 

 within a few miles of the Cordillera ; and an opportunity was thus afforded of 

 verifying the nature of the country in its entire breadth. At the Rio Negro the 

 plains are much more thickly covered with bushes, (chiefly acacias,) than in any 

 other part of Patagonia. 



Tierra del Fuego may be supposed to include all the broken land south of 

 a line joining the opposite mouths of the Strait of Magellan. The land is moun- 



