304 Notice of Active and Extinct Volconos. 



" The process, by which these islands, according to Moreau 

 de Jonnes, are in many instances formed, is sufficiently curious ; 

 first a submarine eruption raises from the bottom of the sea 

 masses of volcanic products, which as they do not rise above the 

 surface of the water, but form a shoal a short way below its 

 surface, serve as a foundation on which the Madreporite3 and 

 other marine animals can commence their superstructure. 

 Hence those beds of recent coralline limestone, seen covering 

 the volcanic matter in many of the islands." 



Some valuable geological information respecting the West 

 India islands may be found in the report of Mr. William 

 Maclure, the celebrated American geologist, in the Jour- 

 nal de Physique. 



Continental America. 



Californa. — There are three active volcanos in the penin- 

 sula of Californa ; Mount St. Elia, seventeen thousand eight 

 hundred and seventy-five feet high, being the highest land in 

 North America. Mount del Buen Tiempo, and volcano de 

 las Virgines. 



Mexico. — In this country, in the 24th degree of north lati- 

 tude, commences that great volcanic chain which extends 

 with little interruption to the 2d degree of south latitude. 



The first active volcano is in the parallel of the city of 

 Mexico itself. 



" And here almost in the same line occur five, so placed that 

 they appear to be derived from a fissure traversing Mexico 

 from west to east, in a direction perpendicular to that of the 

 great mountain chain, which extending from north-west to south- 

 east, constitutes the great table land of the American Continent. 

 It is interesting to remark, that if the same parallel line, which 

 connects the active volcanos of Mexico, be prolonged in a wes- 

 terly direction, it would traverse the groupe of islands called the 

 Isles of Revillagigedo, which there may be reason to consider 

 volcanic from the pumice found amongst them." 



The most eastern is a few miles northwest of Vera Cruz, 

 it is called Tuxtla and had a considerable eruption in 1793, 

 on which occasion, the ashes were carried fifty-seven leagues 

 to Perote. 



