412 COSMOS. 



bear in mind the powerful influence exerted, according to the 

 admirable investigations of Percival, Saussure, Boussingault, 

 and Liebig, by tlu'ee or four ten-thousandth parts of carbonic 

 acid in our atmosphere on the existence of the vegetable 

 organism. From Bunsen's excellent work on the different 

 kinds of volcanic gas, it appears that among the fumaroles 

 of different stages of activity and local diversity some (as, for 

 example, at Hecla) yield J»|n 0*81 to 0-83 of nitrogen, and 

 in the lava streams of t^^ountain 0-78, with mere traces 

 (0*01 to 0-02) of carbonic acid ; while others in Iceland, as, 

 for instance, near Krisuvik, on the contrary, yield from 0*86 

 to 0-87 of carbonic acid, with scarcely 0*01 of nitrogen.* 

 We find likewise, in the important work on the emanations 

 of gas in Southern Italy and Sicily, by Charles Sainte-Claire 

 Deville and Bornemann, that there is an immense proportion 

 of nitrogen gas (0-98) in the exhalations of a fissure situated 

 low down in the crater of Vulcano, while the sulphuric acid 

 vapors show a mixture of 74-7 nitrogen gas and 18*5 oxygen, 

 a proportion which approaches pretty nearly to the composi- 

 tion of the atmospheric air. On the other hand, the gas 

 which rises from the spring of Acqua Santa,t in Catania, is 

 pure nitrogen gas, as was also the gas of the Volcancitos de 

 Turbaco at the time of my American journey.| 



Are we to conclude that the great quantity of nitrogen 

 dispersed through the medium of volcanic action consists of 

 that alone which is imparted to the volcanoes by meteoric 

 water ? or are there internal and deeply-seated sources of 

 nitrogen ? It must also be borne in mind that the air dis- 

 solved in rain-water does not contain, like the atmosphere, 

 0*79 of nitrogen, but, according to my own experiments, only 

 0-69. Nitrogen is a source of increased fertility,§ by the form- 



sented to it by the ships which traverse it, yet the trace of silver in the 

 sea-water has in recent times become observable on the copper sheath- 

 ing of ships. 



* Bunsen, Ueher die ckemischen Prozesse der VulkaniscJien Gesteins- 

 bildungen, in Poggend,, Annalen, bd. Ixxxiii., s. 242 and 246. 



t Comptes rendus de VAcad, des Sciences, t. xliii., 1856, p. 366 and 

 689. The first correct analysis of the gas which rushes with noise from 

 the great solfatara of Pozzuoli, and which was collected with great dif- 

 ficulty by M. Ch. St.-Claire Deville, gave the following results : Sul- 

 phurous acid(aaV/e sulfureux), 24-5 ; oxygen, 14'5 ; and nitrogen, 61*4. 



X See above, p. 202, 208. 



§ Boussingault, Economie Rurale (1851), t. ii., p. 724-726: "The 

 permanency of storms in the interior of the atmosphere (within the 

 tropics) is an interesting fact, being connected with one of the most 

 important questions in the physical histcrry of the globe, namely, that 



