376 Miscellmiies. 



This salt has claims of scientific interest quite eqnal to those of 

 any mineral hitherto discovered. It indicates to us, who are accus- 

 tomed to a humid climate, with heavy rain storms, a state of atmos- 

 pheric dryness, as far removed from our experience as the singular 

 products there deposited are from our own rocks and soils. 



During the scientific tour of Mr. John H. Blake, of Boston, a great 

 number of specimens, illustrating the forms and composition of this 

 salt, were collected, and I have been able to learn some facts from 

 the chemical examination of them, but have to regret that the loss of 

 Mr. Blake's journal has prevented our having a full account of their 

 geological relations. 



The Nitrate of Soda exists in large beds, a few feet below the sa- 

 line soil, or forming that soil in various places, from Arica on the 

 north and west, to the course of the river Loa on the south. The 

 country is an elevated pampa, having the form of a shallow basin, 

 bounded by the coast cliffs on the west, by the higher pampas on the 

 north, by sandstone hills on the east, and the ravine through which 

 the river Loa falls into the sea on the south. The elevation of the 

 pampa of Tamarugal in the province of Tarapaca is nearly 3300 feet 

 above the level of the Pacific. 



The western border or coast presents granite, on which the pale 

 flesh-colored feldspar porphyry, peculiar to volcanic regions, reposes. 

 This rock is doubtless trachyte, and its extent and volcanic character 

 make it one of the most important of known rocks. Imbedded in the 

 soil and forming, extensive tracts, are shells of the same species as 

 those now existing in the ocean. A saline soil and other appearances 

 denote that a long line of coast has been elevated from below the 

 ocean's waters. In travelling north, Mr. Blake found that the pam- 

 pas were broken by ravines, through which the waters from the Cor- 

 dilleras flow at times. A remarkable feature is disclosed by these 

 ravines : a section always presents a higher level on the north than on 

 the south side, so that each pampa presents a steppe, rising as we ad- 

 vance northward. The sandstone hills forming the eastern boundary 

 are of moderate elevation ; they contain beds of gypsum, and form 

 the western barrier of another basin, the eastern bounds of which 

 are the Cordilleras. 



The pampa is mostly uninhabitable, but spots where water can be 

 obtained, and parts of the ravines are cultivated. Nearly midway 

 between the eastern and western limits of this pampa there exists a 

 buried forest of large trees, mostly of the Algorabo species. The 

 trees are inclined towards the southwest, and the wood is singularly 

 well preserved. Specimens have the color and grain of old mahoga- 

 ny, but are brittle. The gaseous constituents of recent wood seem 



