414 Expedition to the 



our, about White river it is a dirty yellow; and at the St. Fran- 

 cis, a 2;rayish brown. A corresponding change may also be 

 noticed in the inclination of the strata, and in other par- 

 ticulars. Aside from this apparently intimate connexion, 

 there is a particular resemblance between the petrosilex of 

 the Washita and the flint rock of the Lead Mine district. 

 The rock in both instances falls readily into small masses of 

 a few ounces weight, the hills based on it are usually roun- 

 ded, and often bear open forests of pine, while the timber 

 most frequent on the sandstone hills is usually oak. 



Open woods of pine and oak occur in almost all the up- 

 lands in the Ozark mountains, and are considered unfailing 

 indications of a meagre and flinty soil. This flinty stratum 

 is extensiv"ely distributed, and deserves the particular atten- 

 tion of such as may hereafter visit the interesting region in 

 which it occurs. Our limited observations have induced us 

 to assign it a place, next above the limestones of the coal 

 series, where these are found, but we were disappointed in 

 not being able to trace the outcrop of any stratum, cutting it 

 off from the more ancient petrosilex of the Washita. 



III. — Argillaceous Sandstone. 



The sandstones of this small group of mountains, appear 

 under almost every variety of character, but in most of them, 

 as far as hitherto examined, we discover traces of coal, or of 

 those minerals, and those impressions of vegetables, which 

 usually accompany it. In the inclined sandstone near the 

 Hot Springs, there are, it is true, no indications of coal, and 

 that rock is, in every respect, similar to what are called the 

 transition sandstones, of the Alleghany and Catskill moun- 

 tains; but by following it an inconsiderable distance, either 

 east or west, it is found passing imperceptibly into the coal 

 strata of the Poteau, and of the Little Red river of White 

 river. In this instance, as in that of the stratum last men- 

 tioned, we find a rock apparently possessing as much unity 

 as can belong to such a subject, passing from recent secon- 

 dary through all the intermediate grades to the oldest 

 transition^ and thus demonstrating the fallacy of the doctrines 

 of the original continuity and systematic succession of strata. 

 A conspicuous character in the sandstones, about the cen- 

 tral and western portions of the region under consideration, 

 is the great proportion of mica, in large scales, which enters 

 into their composition. Fragments of the sand-rock, about the 



