TRUE VOLCANOES. 413 



ation of ammonia, through the medium of the almost daily 

 electrical explosions in tropical countries. The influence of 

 nitrogen on vegetation is similar to that of the substratum of 

 atmospheric carbonic acid. 



In analyzing the different gases of the volcanoes which lie 

 nearest to the equator (Tolima, Purace, Pasto, Tuqueres, and 

 Cumbal), Boussingault has discovered, along with a great 

 deal of aqueous vapor, carbonic acid and sulphurated hydro- 

 gen gas, but no muriatic acid, no nitrogen, and no free hy- 

 drogen.* The influence still exercised by the interior of our 

 planet on the chemical composition of the atmosphere in with- 

 drawing this matter, in order to give it out again under other 

 forms, is certainly but an insignificant part of the chemical 

 revolutions which the atmosphere must have undergone in 

 remote ages on the eruption of great masses of rock from open 

 fissures. The conjecture as to the probability of a very large 

 portion of carbonic acid gas in the ancient aeriform envelope 

 is strengthened by a comparison of the thickness of the pres- 

 ent seams of coal with that of the thin coal-strata (seven lines 

 in thickness) which, according to Chevandier's calculations, 

 our thickest woods in the temperate zone would yield to the 

 soil in the course of one hundred years.f 



In the infancy of geognosy, previous to Dolomieu's ingen- 

 ious conjectures, the source of volcanic action was not placed 



of the fixation of the nitrogen of the air in organized beings. When- 

 ever a series of electric sparks passes through the humid atmosphere, 

 the production and combination of nitric acid and ammonia take place. 

 The nitrate of ammonia uniformly accompanies the rain during a 

 storm, and being by nature fixed it can not maintain itself in a state 

 of vapor ; carbonate of ammonia is found in the air, and the ammonia 

 of the nitrate is carried to the earth by the rain. Thus it appears, in 

 fact, to be an electric action which disposes the nitrogen of the atmos- 

 phere to become assimilated by organized beings. In the equinoxial 

 zone, throughout the' whole year, every day, and probably even every 

 moment, there is a continual succession of electric discharges going on. 

 An observer stationed at the equator, if he were endowed with organs 

 sufficiently sensitive, would hear without intermission the noise of 

 thunder." Sal ammoniac, however, together with common salt, are 

 from time to time found as products of sublimation, even in lava 

 streams — on Hecla, Vesuvius, and iEtna, in the volcanic chain of 

 Guatemala (the volcano of Izalco), and, above all, in Asia, in the vol- 

 canic chain of the Thian-shan. The inhabitants of the country be- 

 tween Kutsch, Turfan, and Hami pay their tribute to the Emperor of 

 China in certain years in sal ammoniac (in Chinese, nao-sha, in Per- 

 sian nushaden), which is an important article of internal trade. (Asie 

 Centrak, t. ii., p. 33, 38, 45, and 428.) 



* Viajes de Bonssingaidt (1849), p. 78. 



t Cosmos, vol. i., p. 280-282, 



