xxxiv Physical and Geognostic Suggestions, 



Sacramento River, (where a trachytic crater, iu a state of dis- 

 integration, is known as the Butt of Sacramento). Does the 

 auriferous quartz occur in veins, and are these still in situ, or 

 are they broken up ? What description of rock is traversed 

 by these veins ? Does the wash-gold here contain occasion- 

 ally, as in the Ural Mountains, fragments of vein-stones with 

 isolated cavities, in which are found impressions of leaves and 

 membranes, clearly proving that they have not been rolled, or 

 transported by water, any great distance to the spot they now 

 occupy? Have these been found, alongside of gold, dia- 

 monds, platimun, osmium, iridium, or mercury ? 



Should the frigate steer for Acapulco, it may be assumed 

 that there exists an intention to cross the Continent to Mexico 

 and Vera Cruz, from the volcano of Colima (1877 toises) as 

 it were, along the parallel of the range of volcanoes, and 

 greatest heights rising in detached groups between the two 

 seas, about the parallel of 19° N. New astronomical ob- 

 servations are greatly needed for determining- the position of 

 the volcanoes of Colima and Jorullo (667 toises). The 

 volcano of Colima, with its twin peaks defuego and de nieve, 

 should be carefully examined, as also the volcano of Jorullo, 

 with the fragments of granite enclosed in its lava ; the 

 Nevado de Toluca (2372 toises), Popocatepetl (2772 toises), 

 Itztaccihuatl (2456 toises), Cofre de Perote (2098 toises), and 

 the volcano of Tuxtla (18° 28' N.), on the eastern slope of 

 the Sierra St. Martin, from which a column of flame shot up 

 with great violence on 2nd March, 1793, a fair specimen of 



