536 ON THE FOR>L\TION OF ROCKS. [August, 



the greater part of tlie Vivarais ; at Montpellier and 

 Agde in France ; at Carthagena in Spain ; in patches 

 along tlie foot of the south side of the Alps, from tlie 

 valley of Falsa to Lago Majore, &c. &c. On the 

 continent of America, north of the Gulf of Mexico^ 

 and east of the Mississippi, none of this formation has 

 yet been found ; the nearest to it is the trap, which co- 

 vers the oldest red sandstone, but it has no basaltic 

 columns, nor does it contain any peridot or pyroxine ; 

 and in other respects does not much resemble this 

 class of rocks : tliough this trap approaches nearer to 

 it, than any other yet found. Neither have any ac- 

 tive or extinct volcanoes been found in that country, 

 which is a species of proof in favour of common ori- 

 gin 5 for if the first and second orders of this class had 

 been found in the United States, and none of the 

 third order, it might have given reason to doubt of 

 their origin ; or if tlie third order had been found, and 

 tlie first and second orders of this class were wanting, 

 it would have been equally the cause of doubts ; but 

 absence of all the three orders, implies the absence of 

 ilre, the origin of the three orders. 



CLASS lU, 



Coniaisiing rocks that have some distant resem- 

 blance both to t]]e rocks originating in water, and in 

 fire, but no distinct analogy to either : whose origin 

 must remain in doubt, depending on simple conjec- 

 ture 



