220 COSMOS. 



Does not this pleasarrt odor afford indications of naphtha? 

 The same thing is also referred to by Kotzebue, in his Rus- 

 sian voyage of discovery, in connection with an igneous 

 eruption (1804) of the volcanic island of Umnack, newly 

 elevated from the sea in the Aleutian Archipelago. During 

 the great eruption of Vesuvius, on the 12th August, 1805, 

 which I observed in company with Gay-Lussac, the latter 

 found a bituminous odor prevailing at times in the ignited 

 crater. I bring together these little-noticed facts, because 

 they contribute to confirm the close concatenation of all 

 manifestations of volcanic activity, the intimate connection 

 of the weak salses and naphtha springs with the true vol- 

 canoes. 



Circumvallations, analogous to those of the craters of ele- 

 vation, also present themselves in rocks which are very dif- 

 ferent from trachyte, basalt, and porphyritic schists ; for ex- 

 ample, according to Elie de Beaumont's acute observation, 

 in the granite of the French Alps. The mountain mass of 

 Oisans, to which the highest* summit of France, Mont Pel- 

 voux, near Briancon (12,905 feet), belongs, forms an amphi- 

 theatre of thirty-two geographical miles in circumference, in 

 the centre of which is situated the small village of La Be'- 

 rarde. The steep walls of this circular space rise to a height 

 of more than 9600 feet. The circumvallation itself is gneiss ; 

 all the interior is granite.f In the Swiss and Savoy Alps 

 the same formation presents itself repeatedly in small dimen- 

 sions. The Grand Plateau of Mont Blanc, in which Bravais 



forth, fire rose out of the earth (sec Curtius, Pcloponncsos, bd. i., s. 42 

 and 46). On the " indescribable pleasant odor" which followed the 

 stinking sulpffurous odor, near Santorin (September, 1650), see Ross, 

 Reisen aufden Griech. Inseln des agaischen Mceres, bd. i., s. 196. Upon 

 the odor of naphtha in the fumes of the lava of the Aleutian island 

 Umnack, which appeared in 1796, see Kotzebue's Entdeckungs-Reise, 

 bd. ii., s. 106, and Leopold de Buch, Description phys. des lies Cana- 

 ries, p. 458. 



* The highest summit of the Pyrenees, that is, the Pic de Nethou 

 (the eastern and highest peak of the Maladetta or Malahita group), has 

 been twice measured trigonometrically ; its height, according to Re- 

 boul, is 11,443 feet (3481 metres), and, according to Coraboeuf, 11,167 

 feet (3404 metres). It is, therefore, 1705 feet lower than Mont Pel- 

 voux, in the French Alps, near Brian9on. The next in height to the 

 Pic de Nethou, in the Pyrenees, are the Pic Posets or Erist, and of 

 the group of the Marbore, the Montperdu, and the Cylindre. 



f Meinoirepour servir a la Description Geologiquede la France, t. ii., 

 p. 339. Upon "valleys of elevation" and "encircling ridges" in the 

 Silurian formation, see the admirable description of Sir Roderick Mur- 

 chison in " The Silurian System," pt. i., p. 427-442. 



