432 Expedition to the 



Horizontally stratified limestone is met with in many parts 

 of this formation, but is most abundant in the central por- 

 tions, about the beds of the great rivers^ and in those parts 

 which have the least positive elevation. Compact limestone 

 is a name sometimes used to designate all the varieties of 

 that rock occuring in districts of secondary, but is certainly 

 inapplicable to the limestone about Cape Girardeau, and in 

 many other places which is, notwithstanding, manifestly se- 

 condary. Some of the limestone northwest of the primitive, 

 on Hudson's river, about the Catskill and Heiieberg Moun- 

 tains IS of this crystalline variety, but abounds in marine ex- 

 uviae • — That of Lake Champlain, as well as the greater part 

 of that in the interior and western parts of the state of New 

 York, is of the compact blue variety. From the falls of the 

 Ohio at Louisville, to Cincinnati, a mixed kind partaking of 

 the character of both of the before mentioned varieties, is 

 found along the river, and for some distance on each side. 

 This limestone is confined to a small district, and is on all 

 sides bounded by sandstone, which rises from below it, and 

 on which it is supposed invariably to rest.* It is an inierest- 

 ing subject for future inquiry, whether the red standstone 

 which is found on the southwestern branches of the Arkansa, 

 in a horizontal position, and which in strata, highly inclined, 

 skirts, the base of the Rocky Mountains, extends also to 

 distant portions of the secondary, and whether like the old 

 red sandstone of England, Scotland, and Germany,f it is the 

 substratum of the great western coal series. 



Throughout the country adjacent to the Ohio river, the 

 prevailing and basis rock, is a gray horizontal sandstone, of- 

 ten approaching in character, those varieties which contain 

 coal. It embraces extensive beds of coarse conglomerate, 

 and supports, or alternates with compact limestone. Here, as 

 in many parts of the vallev of the Mississippi, the limestones 

 and sandstones, like those of Turimiquiri, and Cumanacoa, 

 in South America,:}: alternate frequently with each other. 



Sect. IV. — Of the Alleghany Mountains. 



By this name we intend to designate the great range of 

 mountains extending parallel to the Atlantic coast, from the 

 sources of the St. John's river in New Brunswick, in the 



* Picture of Cincinnati, p. 64. 



t Annals of Philos. for Aug. 1822, p. 90. 



I See Humb. Pers. Nar. vol. iii. p. 94. 



