206 cosmos. 



geognosy and chemistry, made the remarkable observation 

 that at present "the cones diffuse a bituminous odor" (of 

 which no trace existed in my time) ; " that some petroleum 

 floats upon the surface of the water in the small orifices, and 

 that the gas pouring out may be ignited upon every mud- 

 cone of Turbaco." Does this, asks Acosta, indicate an al- 

 teration of the phenomena brought about by internal pro- 

 cesses, or simply an error in the earlier experiments? I 

 would admit the latter freely, if I had not preserved the leaf 

 of the journal on which the experiments were recorded in 

 detail,* on the very morning on which they were made. I 



without any residue of nitrogen (?), and without depositing sulphur 

 (when in contact with the atmosphere). Thus the nature of the phe- 

 nomenon has completely changed since your journey, unless ice admit an 

 error of observation, justified by the less advanced state of experi- 

 mental chemistry at that pei'iod. I no longer doubt that the great 

 eruption of Galera Zamba, which illuminated the country in a radius 

 of 100 kilometres (62 miles), is a salses-like phenomenon, developed 

 on a great scale, since there exist hundreds of little cones, vomiting 

 saline clay, upon a surface of 400 square leagues. I propose examin- 

 ing the gaseous products of the cones of Tubara, which are the most 

 distant salses from your Volcancitos of Turbaco. From the powerful 

 manifestations which have caused the disappearance of a part of the 

 peninsula of Galera Zamba, now become an island, and from the ap- 

 pearance of a new island raised from the bottom of the sea in 1848, 

 and which has since disappeared, I am led to think that it is near 

 Galera Zamba, to the west of the delta of the Rio Magdalena, that 

 the principal focus of the phenomenon of salses in the province of 

 Carthagena is situated" (from a letter from Colonel Acosta to A. von 

 Humboldt, Turbaco, 21st December, 1850). See also Mosquera, Me- 

 moria politica sobre la Nueva Granada, 1852, p. 73; and Lionel Gis- 

 borne, The Isthmus of Darien, p. 48. 



* During the jvhole of my American expedition I always adhered 

 strictly to the advice of Vauquelin, under whom I worked for some 

 time before my voyage : to write down and preserve the details of ev- 

 ery experiment on the same day. From my journals of the 17th and 

 18th April, 1801, I here copy the following: "As, therefore, the gas 

 showed scarcely 0*01 of oxygen from experiments with phosphorus 

 and nitrous acid gas, and not 0*02 of carbonic acid with lime-water, 

 the question is, what are the other 97 hundredths ? I supposed, first 

 of all, carbureted and sulphureted hydrogen ; but no sulphur is de- 

 posited on the margins of the small craters in contact with the atmos- 

 phere, and no odor of sulphureted hydrogen was to be perceived. 

 The problematical part might appear to be pure nitrogen, for, as above 

 mentioned, nothing was ignited by a burning taper ; but I know, from 

 the time of my analyses of fire-damp, that a light hydrogen gas, free 

 from any carbonic acid, which merely stood at the top of a gallery, 

 did not ignite, but extinguished the pit candles, while the latter 

 burned clearly in deep places, when the air was considerably mixed 

 with nitrogen gas. The residue of the gas of the Volcancitos is, 

 therefore, probably to be regarded as nitrogen, with a portion of hy- 



