1870.] 



419 [Maack. 



influence than the configuration of this elevation. In short, all 

 the natural circumstances in the Argentine Republic are of such a 

 character that they afford broader and more extensive areas for 

 the development of the same geological formations, as well as of 

 the same plants, animals and human beings, and make the tran- 

 sition from one specific organic province to another less abrupt 

 and more evident., But just for this reason, the Argentine Repub- 

 lic is to the naturalist one of the most instructive countries for 

 studying the distribution of plants and animals, as well as their 

 dependence upon the geological constitution of the country. 



This La Plata plain, the western boundary of which, as I have 

 already mentioned, is formed by the Cordilleras de los Andes, ex- 

 tends from the 2 2d to the 5 2d degree of south latitude, and embraces, 

 inclusive of Patagonia, an area of 1,281,000 square miles, with 

 1,710,000 inhabitants. This area forms, with the plain of the 

 Orinoco and Venezuela, and that of the Rio Negro and of the 

 Amazons, the three great divisions into which the low lands of 

 South America can be divided. Generally speaking, this La 

 Plata plain consists of two entirely different parts, the limits of 

 which are traced by a line commencing at the foot of the Cordilleras 

 under the 31st degree of south latitude, near San Juan, and running 

 over San Luis della Punta, La Reduccion, and Frayle Muerto to the 

 Rio Salado, which discharges itself into the river Parana. 



The influential character of this line is especially produced by the 

 Sierra de Cordova and its branches, the elevation of which has a 

 meteorologic influence of the first rank, and consequently an influ- 

 ence also upon the development of plants and animals. This 

 characteristic feature of the Sierra de Cordova has led the national 

 government of this Republic to erect an observatory at Cordova, 

 the capital town of the province, which lies eleven hundred and 

 seventy-eight feet above the level of the ocean, under the direc- 

 tion of the distinguished American astronomer, Dr. Gould, of Cam- 

 bridge. No doubt Dr. Gould will make, during his stay in that 

 country, important meteorological observations, and contribute in 

 this way much towards a better understanding of its different 

 physical features. 



The great value of a correct observation and understanding of 

 the different physical and meteorological phenomena, is clearly 

 shown by the following striking fact. In general, the land of 

 the north-western provinces is not fertile, and the vegetation is 



