46 



OUTLINES OF GEOLOGY. 



sub-appenine hills, it is found at considerable heights, as it is 

 on the slopes of iEtna ; and instances are quoted where it has 

 been elevated 15,000 feet. 



In the United States, it forms a band, nearly parallel to 

 the coast, which may be traced from Long Island to 

 Florida. 



103. Rocks of volcanic origin are frequently intercalated 

 among the formations of the superior order, showing that 

 this species of action prevailed at the time of their deposit. 



II. SUPERMEDIAL ORDER. 



Cretaceous, Oolitic, and Sand-stone Group es, Delabeche ; Terrains Yzemeniens } 

 Telagiques and Abyssiques, Brogniart. Newer secondary formations, 



104, The Supermedial order may be divided into four 

 groups, three of which take their names from the prevailing 

 rock, viz: — 



1 . Cretaceous, or Chalk ; 



2. Green Sand ; 



3. Oolitic; 



4. Triasic. 



105. The formations of this order are readily distinguished 

 from those of the Superior ; (1) by their chemical charac- 

 ter ; (2) by greater compactness in their mechanical struc - 

 ture, which better entitles them to the name of rocks ; (3) by 

 so marked a difference in their organic remains that they may 

 be ascribed to a different creation ; (4) by a want of con- 

 formity in their strata, those of the supermedial being rarely 

 parallel to those of the superior order, and of the two, the for- 

 mer has been most disturbed and changed from its original 

 horizontal position. The mode of occurrence of their or- 

 ganic remains is also a distinctive character. In this order 

 they are mostly petrified, a case of rare occurrence in the 



