F A R JNl E R S ' REGISTER. 



613 



If ihe above is worthy of a place in your Cabi- 

 net, it is at your service. 



Yours, ie^-pectl'u!ly, Colluton. 



July 18-10. 



NATIVE NITRATE OF SODA. 



From the Proceedings of the Boston Society of Natural History, 

 1840. 



Dr. M. Gay read the Ibllovving communication 

 from A. A. Ilayes, Esq., of Roxbury, on liie 

 Native Nitrate of Soda, lound in South Peru. 



'I'he existence of beds ol' Nitrate of Soda in Peru 

 has been long known, and the inhabitants of a 

 most arid and desolaie region have made it by 

 simple operations an important article of commerce 

 and manuliicture. 



This salt has claims of scientific interest quite 

 equal to those of any mineral hitherto discovered. 

 It indicates to us, vviio are accustomed to a humid 

 climate, with heavy rain storms, a stale of atmo- 

 spheric dryness, as far removed h'om our experi- 

 ence as the singular products there deposited are 

 ironi our own rocks aud soils. 



During the scientific tour ol' Mr. John II. Blake, 

 of Boston, a great nuiuber of specimens, illustrat- 

 ing the Ibrms and composition of this salt, were 

 collected, and 1 have been able to learn some 

 iiicls Irom 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 

 feel below the saline soil, or forming that soil in 

 various places, from Arica on the north and west, 

 to the course ol'the river Loa on the south. The 

 country is an elevated pampa, having the ibrm of 

 a shallow basin, bounded by the coast cliffs on the 

 west, by the higher pampas on the north, by sand- 

 stone 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 Icet above the 

 level of the Pacific. 



The western border or coast presents gianite, 

 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 Ibrming 

 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 Irom the Cordilleras How at times. A re- 

 markable lijature is disclosed by these ravines ; a 

 section always presents a higher level on the north 

 than on the south side, so that each pampa pre- 

 sents a steppe, rising as we advance northward. 

 The sandstone hills Ibrming the eastern boundary 

 are of moderate elevation ; they contain beds ol 

 gypsum, and form the western barrier of another 

 basin, the eastern bounds of which are the Cor- 

 dilleras. 



The pampa is mostly uninhabitable, but s[)ots 

 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 mahogany, but are brittle. The gaseous 

 constituents of recent wood seem to have been 

 lost, Ibr although resinous, it burns without flame. 

 From personal examination of the country, east 

 of the sandstone elevations, Mr. Blake concludes 

 that a lake of considerable extent once covered the 

 space between these and the Cordilleras. Nume- 

 rous volcanic rents now exist among the moun- 

 tains, and it is probable that the saline matter pro- 

 duced by them was dissolved in the water, form- 

 ing a lake at the base of the mountains. This 

 lake subsequently broke its barriers, and prostrated 

 a lorest then growing where the saline matter is 

 now Ibund. I have carei'ully examined the earthy 

 matter which is mixed with the nitrate of soda 

 from different parts of the province of Tarapaca 

 and find that the larger part is composed of i'rag- 

 menls of finely powdered shells, the color being 

 unchanged. A brown marl Ibrms the remainder, 

 such as results from the washing of sandstone, 

 — these liacts I consider as supporting the conclu- 

 sion of Mr. Blake. The surlace of the pampa is 

 mostly sand, clay, and saline matter. The latter 

 is composed of sulphate of lime and soda, salt, 

 and nitrate of soda — some parts present the nitrate 

 of soda at the surliice — at others, a lew feet below. 

 Those salts have all the physical and chemical 

 characters ol salts produced by decomposition and 

 separated by evaporation from solutions. The 

 nitrate of soda is Ibund in distinct strata, a thin 

 layer of brown loam separating the parts ; it is 

 also Ibund mixed with salt, and forming a small 

 portion of the whole mass. The refining opera- 

 lions are rude and simple. The richest masses of 

 the native salt are blasted or broken and divided 

 into small portions ; with these, copper kettles are 

 in part filled, and water, or the mother water of 

 lormer operations, is added, and heat applied until 

 a boiling and saturated solution is obtained. The 

 solution is transterred to wooden coolers, where 

 the nitrate of soda crystallizes. The undissolved 

 salt remaining in the kettles is thrown aside, fresh 

 salt being used each time, although not one half 

 ol'the nitrate of soda is dissolved. The coolers 

 are emptied after the crystals of nilrate have ceased 

 to Ibrm ; it is dried, packed in bags, and sent to 

 the coast on mules. The wood used in the opera- 

 tions is transported Irom a distance on the backs 

 of mules Irom the borders of the pampa. Of late, 

 ailention has been turned to using the altered wood 

 of the buried forest, and some excavations pro- 

 mised a supply. Water is Ibund by sinking wells 

 in some places, below the saline soil. The sub- 

 sistence of the workmen, drivers and mules, is 

 mostly drawn from Valparaiso. The quantity of 

 nitrate of soda which exists in beds is immense, 

 and in addition it is probable that the saline soil 

 would aflbrd a large supi)ly. 



Native nitrate of soda, in fractured masses, has 

 a granular structure, arising Irom the aggregaiion 

 of irregular rhombic crystals, varying irom fine 

 grained to coarse grained. It is brittle, but yields 

 more easily in one aireclion, separating into angular 

 parts, resembling loaf sugar closely, in some spe- 

 cimens. Color varies from snow-white to reddish 

 brown and gray. Some specimens have a lemon 



