142 Mr. D. Forbes's Researches on the 



the tidal lagoons by the decomposition of sea-salt, effected by the 

 agency of carbonate of lime and organic matter of all kinds, 

 both terrestrial and marine vegetation in particular. No doubt 

 such lagoons or swamps in a tropical climate would be sur- 

 rounded by a luxuriant growth of marine and other plants of 

 semiaquatic habits ; but, independent of this, the whole country 

 in the immediate vicinity, although now perfectly arid and 

 without a drop of surface-water, must then have been clothed 

 by immense and luxuriant forests. This is attested by the 

 occurrence everywhere of enormous quantities of wood, trees 

 with branches and roots perfect and of immense size, found all 

 over this district (buried in the plains themselves), and appa- 

 rently of the same species as now grow in the country. The 

 wood of such is found in all states, from nearly perfect preserva- 

 tion to extreme decay ; and it may not generally be known that 

 for many years, at the commencement of the nitrate trade, and 

 in parts even now, these accumulations of ancient wood formed 

 the supply of fuel for carrying on the process of boiling out 

 the nitrate, and that it was only much later that coal, imported 

 from England and Chile, became the chief combustible, as might 

 be expected, from the great demand created by the subsequent 

 great development of the trade. 



Reeds, rushes, and other vegetable matter, as well as sea-shells, 

 are constantly met with in the deposits ; and at the workings of 

 La Noria*, it was stated that a quantity of what appeared to be 

 guano, had also been found imbedded in the nitrate. 



A chemical examination of the nitrate of soda from the depo- 

 sits at LaNoria about thirty miles east of Iquique, and 3052 feet 

 above the sea, was made with the subjoined results. 



The specimen taken was picked out of a large mass of the 

 more impure " caliche " or crude nitrate, and was pronounced to 

 be of the finest quality, and was in most parts a transparent 

 and colourless aggregate of crystals of small size, but evidently 

 rhombohedral. Hardness =1*75, being below rocksalt, but 

 scratching talc. Its specific gravity was found by taking it in 

 petroleum, and at 60° Fahr. (15°-5 cent.) was 2*18, water being 

 1-000. 



A careful qualitative examination showed the presence of 

 soda, nitric acid, chlorine, sulphuric acid, and lime, with minute 

 traces of alumina, magnesia, and potash, but iodine could not 

 be detected by any of the usual processes. 



* The workings of La Noria and La Corolina pertain to Mr. George 

 Smith, of Iquique, to whom the author is much indebted for the assistance 

 afforded him in his investigations. The development of this district, both 

 as regards nitrate of soda and the borates of lime, is greatly indebted to 

 Mr. Smith's labours ; and his map of the saliferous district, published in 

 Lima, is a valuable contribution to science. 



