2l6 PATAGONIAN EXPEDITIONS: GEOGRAPHY. 



Diversity in Climate and Topography. — Although this entire region has 

 throughout the essential features of a plain, in that over no part of it are 

 there any extensive districts or isolated upthrusts sufficiently elevated 

 above the general surface to assume the appearance of mountains, it must 

 not be inferred that like, or even very similar, conditions prevail through- 

 out its entire extent. Indeed its topographic and physiographic features 

 are considerably diversified, as are also the climatic conditions. The moist 

 climate and rich pasture lands of the Fuegian plains, as well as those of 

 the mainland which border on the Straits of Magellan, contrast strongly with 

 the constantly increasing semi-arid and comparatively barren plains en- 

 countered as one travels northward. These varying climatic conditions 

 are of the greatest importance from an economic and biotic standpoint, and 

 will be fully discussed and satisfactorily accounted for when I come to 

 treat of the climate and economic resources of Patagonia as a whole. 



Climatic Regions. — With reference to climate these plains may be 

 divided into a southern, or Magellanian Region, and a northern, or Santa 

 Cruzian Region. It is evident that any line fixing the northern limit of 

 the former and the southern limit of the latter must be somewhat arbi- 

 trary. It is believed, however, that if the fifty-first parallel be selected 

 as such dividing line, the division thus made will most nearly express the 

 climatic differences that prevail to the north and south of this line, while, 

 at the same time, it will essentially coincide with the areal distribution 

 and limits of certain topographic features characteristic of each of these 

 two regions and which will be discussed later. 



The Magellanian Region. — This region embraces all that portion of the 

 Patagonian plains lying south of the fifty-first parallel and the Fuegian 

 plains of northeastern Tierra del Fuego. It thus includes, of the plains 

 of the mainland, not only those bordering immediately upon the Straits 

 of Magellan, but all that district to the northward drained by the Coy 

 and Gallegos Rivers and their tributaries. It is characterized, for the 

 most part, by rather low, rolling prairie lands, with a rainfall sufficient to 

 give a usually ample water supply and support a rather abundant growth 

 of grass, which would be really luxuriant, were it not for the poverty of 

 the soil, due to the great bed of shingle that everywhere covers the Pata- 

 gonian plains to a depth of many feet. There are few level pampas, and 

 such as there are, are generally of limited extent and low altitude, 

 though to the north they become both broader and more elevated, and in 



