426 Observations on the natural Production of Saltpetre. 



action of the external air, or of the moisture of the ground trans- 

 mitted through the substance of tlie wall: but the result of that 

 experiment in which, the action of the air on the interior surface 

 of the wall having been prevented by the intervention of a glass, 

 the formation of nitre took place only to a very slight extent, is 

 in a great mea,sure at variance with such a su])position. 



Again : though it is evident that the natural prpduction of the 

 isaltpetre is closely connected with change;?' in the state of the 

 atmosp!:ere, those changes relating not only to its temperature 

 but also to the degree of its moisture and barometrical presswe ; 

 vet a much longer series of observations, and tiicse not partial 

 like the present, but carried on in various jiarts of the world, 

 is requisite, before even this part of tlie i)roblcm can be accu- 

 rately solved. Tliere still would remain a part of mucli more 

 difficult solution, namely, the source of the metallic base of the 

 alkali of the nitre. 



With respect to this difficult question, if we compare tlie ele- 

 ments present in the composition of the saltpetre formed, with 

 the eleu\ents of the substances present during its formation, it 

 seems a reasonai)le conclusion that the j^otassium, or the metal- 

 lic i)ase of the potash of the saltpetre, is either a simple princi- 

 ple of some of the elements present, or that it results from the 

 union of 'two or more of those principles, or of two or more of 

 the elements themselves*. 



The gross compounds present during the formation of salt- 

 petre, in the instances mentioned in this paper, are atmosphe- 

 rical air and the limestone on which the salt))etre effloresces ; 

 and all the component ))arts of these may be ultimately resolved 

 into the following elements — oxygen, nitrogen, hydrogen, and 

 carbon, together with iron and the njetallic bases of some of the 

 earths. 



The component parts of nitrate of potash, of which the ?alt- 

 j)etre under conr^ideration almost entirely consists, are nitric acid, 

 water, and potash ; v,-hich may be resolved into the following' 

 elements — oxygen, nitrogen, hydrogen, and potassium : and all 

 these elements are experimentally kn.ovvn to be present in the 

 situations where saltpetre is formed, with the excejjtion of po- 

 tassium. 



lu the supposition then that the saltpetre is a product and 

 not an educt of the above process, since no potash can be de- 



* Tlie terms "clement" and " principle" are licrc used in tlie same re- 

 lation to eucii other as tliu early physical philosophers used the terms flT«;;ttT« 

 d^X'"- They supposed that tlie t'uniier, fhoujili incapahle of decomposition 

 hy common means, were not neccssaiily to he consiriercd as ahsohitely 

 sir.iple snhstancLS : tho^e ahsolutely simple subbtanccs they expressed by 

 tiie tetiji aj;^«/. 



tected 



