NOTES. Ixix 



et sans deposer du soufre (au contact de 1'atmosphere). Ainsi la nature du 

 phenomene a complement change depuis votre voyage, a moins d'admettre une 

 erreur d 'observation, justified par 1'etat moins avance de la cbimie expe'rimen- 

 tale a cette e'poque. Je ne doute plus maintenant que la grande eruption de 

 Galera Zamba, qui a eclaire le pays dans tin rayon de 100 kilometres, ne soit 

 mi phenomene de salses developpe sur une grande echelle, puisqu'il y existe.des 

 centaines de petits cfines, vomissant de 1'argile sale'e, sur une surface de plus de 400 

 lieues carrees. Je me propose d'examiner les produits gazeux dcs cSnes de Turbara, 

 qui sont les salses les plus eloignees de vos volcancitos de Turbaco. D'apres les 

 manifestations si puissantes qui ont fait disparaitre une partie de la pe'ninsule de 

 Galera Zamba, devenue une lie, et apres 1'apparition d'une nouvelle ile, soulevde 

 du fond de la mer voisine en 1 848 et disparue de nouveau, je suis porte a croire 

 que c'est pros de Galera Zamba, a 1'ouest du Delta du Eio Magdalena, que se 

 trouve le principal foyer du phenomene des salses -de la province de Carthagene." 

 (From a letter from Colonel Acosta at Turbaco to myself, 21 Dec. 1850.) 

 Compare also Mosquera, Memoria politica sobre la Nueva Granada, 1852, p. 

 73; and Lionel Gisborne's Isthmus of Darien, p. 4-8. 



( 295 ) p. 213. Throughout the whole of my American expedition, I strictly 

 followed the advice given me by Vauquelin (under whom I had worked for some 

 time previously), to write down the details of every experiment the same day, 

 and to preserve the record. From my journals of the 17th and 18th of April, 

 1801, I subjoin the following extract: " As, according to this, the gas, when 

 tried with phosphorous and nitrous gas, showed hardly O'Ol of oxygen, and 

 with lime-water less than 0'02 of carbonic acid, I ask myself, what are the re- 

 maining ninety-seven parts? I first surmised carburetted and sulphuretted 

 hydrogen ; but no sulphur is deposited on the margins of the little craters, in 

 contact with the atmosphere, nor was any smell of sulphuretted hydrogen per- 

 ceived. The problematical part might seem to have been pure nitrogen, since, 

 as above remarked, a lighted taper caused no ignition ; but I know from the 

 time when I made analyses in the Grubenwetter, that a light hydrogen gas, free 

 from any carbonic acid, which was merely near the roof of a gallery of the mine, 

 also did not ignite ; but, on the contrary, extinguished the miners' candles, which 

 burnt clear at points further in the interior, where there was a considerable 

 mixture of mephitic gas. The residue of the gas of the volcancitos may, there- 

 fore, be called nitrogen with a portion of hydrogen, of which we are not yet able 

 to state the quantity. May there be, under the volcancitos, the same carbonife- 

 rous schist, which I saw to the westward at Eio Sinu, or marl, and alum? l\Iay 

 atmospheric air penetrate through narrow cracks into cavities which have been 

 formed by water, and, in contact with dark-gray mud, become decomposed, as in 



