254 76 



apparatus to pump the air down into the subterranean cavities, where it mixes 

 with the original spring gases. 



The air decomposes the sulphuretted hydrogen in the spring gases, and thus 

 prevents the destructive effect of this gas on the rocks. In this way the inter- 

 mixture of the air with the spring gases perhaps serves to uphold the periodicity 

 of the springs. On the other hand, the oxygen will doubtless affect the solubility 

 of the rocks in spring water containing carbonic acid. The characteristic deposits 

 of silica at Hveravellir have possibly some connection with the comparatively lai'ge 

 quantity of oxygen in the spring gases there. 



1 have assumed that the relatively large amount of nitrogen in the spring 

 gases from Hveravellir and in Reykjafoss No. 1 is of atmospheric origin. I cannot, 

 however, adduce direct proofs of this supposition, but it seems to me that the pre- 

 sence of nitrogen in the spi'ing gases is readily and naturally explained in this 

 manner; and the oxygen in the spring gases bears evidence to the same effect. 



BuNSEN went still further. ' It was his opinion that the nitrogen in the Ice- 

 landic spring gases was entirely of atmospheric origin. But when we take into 

 consideration the fact that the spring gas at several places, (at Reykir. at Laugaras 

 and, generally speaking, at Grafarbakki) consists solely of nitrogen, it is open to 

 question whether all this nitrogen really originated from the asmosphere, and by 

 what means the soil is enabled to retain the atmospheric oxygen so that not a 

 trace of it is to be found in the spring gases. 



Before my journey to Iceland, I did not know that such nitrous springs 

 existed in that country." However, I considered the question of the origin of 

 nitrogen in the spring gases of so great importance, that I decided to make a closer 

 investigation on the point. I thought that a determination of the proportions in 

 which argon and nitrogen are found in the spring gases would most probably give 

 a decisive answer to this question, because it was very improbable that these 

 gases would combine with other substances. But Ramsay's^ investigations have 

 since indicated the probability of argon being produced by radio active substances 

 under certain conditions, and the determination of the proportion between argon 

 and nitrogen in the spring gases can therefore only give reliable information 

 concerning the origin of the nitrogen, in the event of the amount of argon being 

 smaller, in comparison with the nitrogen, than in the atmosphere. In this case, 

 however, it is most probable that some of the nitrogen is due to chemical pro- 

 cesses down in the earth, for at present we know no instance of argon combining 

 with other substances. 



> Liebigs Ann. 62, 5. 1847. 



2 I have since noticed that Bunsen, (Gasometrische Methoden, 2. Aufl. 1877, p. 78). has made an 

 analysis of an Icelandic spring gas whicli consists cliiefly of nitrogen, (99-48 "In nitrogen, 052 "In hydrogen). 

 As this spring gas is stated to have come from a small group of liot springs to the nortli of "Mælifell", 

 it probably originates from the spring group "Reykir in Sliagafjöröur". 



' Nature. 1907. p. 269. 



