SALSES. 205 



twenty seconds before each eruption. A very thin burning 

 wax taper was instantly extinguished in the gas, which was 

 twice collected with great care ; this was also the case with 

 a glowing chip of the wood Bombax Ceiba. The gas could 

 not be ignited. Lime-water was not rendered turbid by it ; 

 no absorption took place. When tested for oxygen with 

 nitrous acid gas, this gas showed no trace of the former in 

 one experiment ; in a second case, when the gas of the Vol- 

 cancitos had been confined for many hours in a bell glass 

 with water, it exhibited rather more than one hundredth of 

 oxygen, which had probably been evolved from the water 

 and accidentally intermixed. 



From these analytical results I then declared, perhaps not 

 very incorrectly, that the gas of the Volcancitos of Turbaco 

 was nitrogen gas, which might be mixed with a small quan- 

 tity of hydrogen. At the same time, I expressed my regret 

 in my journal that, in the state of chemistry at that time 

 (April, 1801), no means were known by which, in a mix- 

 ture of nitrogen and hydrogen gases, the numerical propor- 

 tions of the mixture might be determined. The expedient, 

 by the employment of which three thousandths of hydrogen 

 may be detected in a. gaseous mixture, was only discovered 

 by Gay-Lussac and myself four years afterward.* During 

 the half century that has elapsed since my residence in Tur- 

 baco, and my astronomical survey of the Magdalena River, 

 no traveler had occupied himself scientifically with the small 

 mud volcanoes just described, until, at the end of December, 

 1850, my friend Joaquin Acosta,| so well versed in modern 



* Humboldt and Gay-Lussac, Memoire sur Vanalyse de Tair atmos- 

 phcrique in the Journal de Physique, par Lamitkerie, t. lx., p. 151 (see 

 my Kleinere Schriften, bd. i., s. 316). 



f "It is with emotion that I have just visited a place which you 

 made known fifty years ago. The appearance of the small volcanoes 

 of Turbaco is such as you have described ; there is the same luxuri- 

 ance of vegetation, the same form of cones of clay, and the same ejec- 

 tion of liquid and muddy matter ; nothing has changed, unless it be 

 the nature of the gas which is evolved. I had with me, in accordance 

 with the advice of our mutual friend, M. Boussingault, all that was 

 necessary for the chemical analysis of the gaseous emanations, and 

 even for making a freezing mixture for the purpose of condensing the 

 aqueous vapor, as the doubt had been expressed to me that nitrogen 

 might have been confounded with this vapor. But this apparatus was 

 by no means necessaiy. As soon as I arrived at the Volcancitos, the 

 distinct odor of bitumen set me in the right course ; I commenced by 

 lighting the gas upon the very orifice of each small crater. Even now 

 one sees on the surface of the liquid, which rises intermittently, a 

 delicate film of petroleum. The gas collected burns away entirely, 



