47 



work. I have first related a great number of 

 solitary facts, and then considered them in one 

 general point of view. Every thing announces 

 in the interior of the Globe the operation of 

 active powers, which react, balance, and mo- 

 dify one another. The greater our ignorance 

 of the causes of these undulatory movements, 

 these evolutions of heat, these formations of 

 elastic fluids, the more it becomes the duty of 

 the natural philosopher, to examine the relations 

 existing between these phenomena at great dis- 

 tances, and in so uniform a manner. It is only 

 by considering these various relations under a 

 general point of view, and following them on a 

 large extent of the surface of the Globe, through 

 formations of rocks the most different, that we 

 are led to abandon the supposition of trifling 

 local causes, strata of pyrites, or of coal set on 

 fire*. 



* In a work in other respects equally rich in ingenious 

 views and well observed facts, the Geological Essays of Mr. 

 Steffens ( Geognostich-geologischeAufscetze,]). 325, itis asserted, 

 that, ei hot springs, earthquakes, and volcanic eruptions, 

 take place only where there are strata of coal, because these 

 alone can furnish materials for combustion, and keep up, in 

 the great electro-motive apparatus of the Earth, a strong 

 electrical tension. If travellers have thought they have 

 observed these phenomena in primitive formations, as recently 

 in South America, they have confounded," continues the 

 author, " the secondary porphyries (Jlcetzporphyre) which 



