72 NATURAL HISTORY. 



mountain which burns incessantly. This volcano, 

 like the rest, throws out many cinders and stones ; 

 and the Portuguese, who have attempted several times 

 to erect habitations in this island, have been constrain- 

 ed to abandon this project, through the dread of the ef- 

 fects of the volcano. The Canaries, the Peak of Tene- 

 riffe, and some of the highest mountains in the world, 

 throw out fire, cinders, and large stones ; from the top, 

 rivulets of melted sulphur flow, which are distinguish- 

 able at a great distance. The matters which volcanoes 

 throw out, generally come forth in the form of a tor- 

 rent of melted minerals, which inundates all the envi- 

 rons of these mountains. These rivers of liquified 

 matters extend even to considerable distances, and 

 when cooled, form horizontal or inclined strata, which 

 for position are like the strata formed by the sediment 

 left by the waters. But it is very easy to distinguish 

 the strata produced by the expansion of matters thrown 

 out by volcanoes, from those which have the sediment 

 of the sea for their origin. 1. Because these strata 

 are not of an equal thickness: 2. Because they contain 

 only matters which are easily perceived to have been 

 calcined, vitrified, or melted, and because they do not 

 extend to any great distance. When coal mines are 

 opened, which are generally met with in argillaceous 

 earth at a great depth, it sometimes happens that these 

 matters have taken fire. There are even mines of coal 

 in Scotland, Flanders, &c. which have burnt for a 

 number of years. The communication of the air suffices 

 to produce this effect, but the fires which are lightes 

 ed in these mines, produce only slight explosions, and 

 do not form volcanoes, because all being solid and full 

 in these places, fire cannot be excited, like that of vol- 

 canoes, in which there are cavities and void place* 



