On Nitrate of Soda. 



355 



sition ; and now let the land be upheaved, and we have as much salt as at 

 Cesemeno." 



But whence comes the nitrate of soda ? Dr. Daubeny* answers 

 the question as follows : — 



" Wherever salt lakes occur, which become partially or wholly dried 

 up during a part of the year, carbonate ofsoda will be formed from the decom- 

 position of common salt. This I have observed myself on the sandy j)lains 

 of Hungary, in the neighbourhood of Pesth. Now, if any circumstances 

 should concur in such spots calculated to generate nitric acid, the latter by its 

 stronger affinity for the alkali would take the place of the carbonic acid, and 

 nitrate of soda would be the result. This however, being a deliquescent salt, 

 would not accumulate on the surface, except in countries like Peru, remarkable 

 for their extreme dryness." 



This solution of the problem is singularly strengthened by the 

 recent accounts of Mr. Bollaert, who finds in the nitrate-beds the 

 very intermediate substance assumed by Dr. Daubeny, carbonate 

 of soda, and again salt-beds changing at bottom into pure nitrate. 

 It may confirm his view that nitrate is also found at the base 

 of similar salt-beds near the Dead Sea.t Whether the nitric acid 

 proceed from decayed animals, as he supposes, or spring from 

 volcanic fumes, as I would conjecture, appears to me doubtful ; 

 but that this vast and valuable layer has been deposited from the 

 ocean, and been afterwards in some way transformed into cubic 

 nitre, seems now beyond doubt. I have been already, however, 

 led too far into speculation by the singularity and value of the 

 deposit, and by the novel information which has just reached 

 us, but hope to be excused by the magnificence of the causes 

 which have conspired to produce this unique phenomenon — the 

 steady sweep of the trade-wind and the mountain-barrier which, 

 drying that wind, has thus preserved a most deliquescent salt ex- 

 posed on the soil's surface for years that are numberless — the 

 series of successive earthquakes which have heaved up the bottom 

 of the ocean and thus precipitated its brine — the volcanic exhala- 

 tions which still issuing in flame from the neighbouring moun- 

 tain-tops have perhaps by more tranquil passage through the 

 pores of the soil converted that brine into a mineral treasure for 

 other arts and for agriculture. 



We now come to the practical questions — How has this mine 

 of fruitfulness been hitherto worked, and can it be worked better 

 hereafter, so as to yield its product at a cheaper rate ? The 

 existence of cubic saltpetre in Tarapaca has been known in 

 Europe about a century, but none was sent to England until 

 1820 ; guano had been known for 200 years to be accumulated 



* Lectures on Agriculture, p. 79. 



f Lumps of nitre were scattered along the base (of the ridge of salt on the S."W. 

 of the Dead Sea), of which we picked np several as large as the fist. — Bohinson's 

 Palestine^ ii. p. 492. 



