On the Formation of Saltpetre. 335 



the surface of the ground, while in our own climate we 

 cannot collect it, if it exists there at all times. 



But it may be asked, Does nitre exist in our soil ? This 

 cannot be doubted for a moment, since we extract it from 

 several plants, such as lettuce, onions, turnips, &c., par- 

 ticularly turnsole. Now it has been clearly established 

 that it is not formed by the act of vegetation, but rather 

 that it existed ready formed in the soils in which these 

 plants have been cultivated*. 



It remains therefore to explain how the nitre is formed 

 in the bowels of the earth. Is it to the decomposition of 

 animal and vegetable substances that the formation of ni- 

 trates is owing? Without doubt nitric acid is formed ia 

 this decomposition, and consequently nitrates, since there 

 are salifiable bases for saturating this acid : but I do not 

 think that this is the priucipal cause of the formation of the 

 nitre ; for, in fact, we know extremely well that the nitric 

 acid in artificial saltpetre works is produced very slowly, 

 and cannot be formed except in a humid and stagnant at- 

 mosphere, at a temperature always uniform and rather low. 

 Now not one of these conditions is fulfilled either in Spain 

 or the East Indies. We cannot therefore attribute to the 

 decomposition of animal and vegetable substances the 

 formation of nil re in the bowels of the earth ; or at least it is 

 but a very trifling cause compared to the effects. 



Does nitre exist ready formed in the bowels of the earth, 

 as we find the sulphates, carbonates, borates, muriate of 

 soda, &c. } This has not been hitherto proved bv any one 

 factf ; and even if it be found in mines, does it follow that 

 this salt must be diffused over the whole surface of the 

 globe ? Sea salt, however, which is so abundant in nature, 

 IS not to be seen efflorescing on the high roads in Spain. 



Nitre not being ttie result of the decomposition of ani- 

 mal and vegetable substances, nor being a natural produc- 

 tion, we ought to seek its origin in the atmosphere; and 

 this will be verv easy to find. 



The rains which fall in the Indies and Spain are fre- 



* Recuril (le MimoiTes sur la Salpetre, published by tjie Acadtmie dcs 

 Sci'-ni a. 



■)■ A letter from M. JJolomieu in the Memoirs above quoted, speaks of a 

 mine of saltpetre found at I<atera in the kingdom of Naples. This mine, 

 accordinff to the report made to him, was so considerable, that oue cavity 

 alone contained more than .TO.OOO (jnintals of pure saltpetre ; and as it con- 

 tained a jrre.il luuiiber of these cavities, it may be regarded as inexhaustible. 

 This fact, nut having been recorded iu other works, particuiarJv in thoso of 

 Fourcroy ;iiid Huuy, I pre>uuie tnu;iC have been very inaccurate. 



qucntly 



