1824.] Volcanos at present in Activity. 205 



little below the true crater. One of these currents did not 

 reach the sea till the 9th of March. Some time after the 

 explosion, there fell in many parts of the island, a shower 

 composed of black ashes, and long flexible threads of glass, 

 resembling golden-coloured hair. This phenomenon, which was 

 chiefly noticed in 1766, has been considered as peculiar to the 

 volcano of Bourbon ; but Hamilton states, that he found similar 

 glassy filaments mixed with the ashes by which the atmosphere 

 of Naples was obscured during the eruption of Vesuvius in 

 1779. 



Those persons who have not particularly studied volcanic 

 phenomena will probably be surprised to learn, that in 1821 the 

 ignited lava of the volcano of Bourbon should be six whole days 

 in traversing, upon inclined ground, the short distance from the 

 crater to the sea. But it ought to be observed that lavas are not 

 perfect fluids, and that in proportion as they cool, their progress 

 must slacken. In 1805, M. de Buch observed a torrent of lava 

 issue from the summit of Vesuvius, and reach the sea shore in 

 three hours ; but the history of volcanos offers few instances of 

 similar rapidity. 



In general the motion of lavas is slow ; those of Etna are 

 whole days in flowing a few feet in the flat lands of Sicily. The 

 external part is sometimes fixed and stationary ; while the cen- 

 tral mass, still fluid and incandescent, continues to flow. The 

 great viscidity of the lavas, when slightly cooled, occasions them 

 to be extremely thick on the edges even when they flow in a 

 level country. 



Zibbel-Tier, accordingto Bruce, is in 15 T V degrees north latitude. 

 The summit of the mountain has four openings, through which 

 there issue thick columns of smoke. 



Few details are known respecting the volcano of Ascension 

 Island. As to that of Madagascar, which is stated to project 

 immense columns of aqueous vapour visible at a distance of 10 

 leagues, its existence has not appeared to me sufficiently proved 

 to induce me to insert it in the catalogue. 



Volcanos of America. 



NortJi-west Coast. 



Mount Saint-Elia. 

 Mount del Buen Tiempo. 

 Volcan de las Virgenes ? 



Mexico. 



Orizaba or Citlaltepetl. 



Popocatepetl or volcan de la Puebla. 



Tuxtla. 



Xorullo. 



Colima. 



