214 REACTION OF THE INTERIOR OF THE EARTH 



in 1834, saw the gas easily kindled and burning with a 

 clear blue flame, leads me to believe that, in dif- 

 ferent stages, the exhalations undergo chemical altera- 

 tions. Mitscherlich, at my request, has recently de- 

 termined the limits of inflammability in artificially 

 prepared mixtures of nitrogen and hydrogen gases. 

 The result was that mixtures of one part hydrogen and 

 three parts nitrogen would not only be ignited by a light 

 being brought near to them, but also would continue to 

 burn : when the proportion of nitrogen was augmented 

 so that the mixture consisted of one part hydrogen and 

 three and a half parts nitrogen, it would still ignite, 

 but would not continue to burn. It was not until the 

 mixture consisted of one part hydrogen and four parts 

 nitrogen that no ignition at all took place. The gaseous 

 exhalations, which, on account of their easy inflamma- 

 bility and the colour of their light, are usually called ex- 

 halations of pure and carburetted hydrogen, need there- 

 fore only in fact have as much as one third part of that 

 gas in their composition. In the more rare mixtures of 

 carbonic acid and hydrogen, on account of the capacity 

 for heat of the former, the limit of capability of igni- 

 tion is modified. Acosta is right in throwing out the 

 question, "whether a tradition subsisting among the 

 natives of Turbaco, descendants of the Indios de 

 Taruaco, according to which the volcancitos were once 

 all burning, and were all changed from 'volcanos de 

 fuego' into f volcanos de agua' by the adjurations of a 

 pious monk, and being sprinkled by him with holy 

 water, ( 296 ) may not have related to a former condition 

 which is now returning ? " Analogous examples are pre- 

 sented by, at one time the eruption of great flames, and 



