48 GEOLOGICAL STRUCTURE OF THE 



We shall now conclude this essay by a few re- 

 marks on the transition chain of mountains which 

 traverse the Arkansa territory. 



§ III. OBSERVATIONS ON THE TRANSITION MOUN- 

 TAINS of arkansa: 

 The first appearance of this formation, as well as 

 the first rock which attracts our attention in ascend- 

 ing the Arkansa, commences about 200 miles above 

 the village or post of Arkansas. From the unusual 

 appearance, and inconsiderable comparative eleva- 

 tion which the hills here present, the place has re- 

 ceived the name of the Little Rock. The strata 

 which are schistose and destitute of organic reliquiae, 

 dip at an angle of more than 45° to the north-east, and 

 consist of dark-grey, or greenish-grey, argillaceous 

 sand- stone, of a fine grain, and intermingled with 

 mica: it appears to be a grauwacke slate, bordering on 

 argillite, and is traversed by massive veins of quartz 

 containing crystals. It is here alternated with a soft 

 and pale coloured slate clay, which decomposes into 

 something resembling pipe- clay, and which the inha- 

 tants have employed for white- washing the interior 

 of their cabins. As we proceeded westward, those 

 hills at length assumed the elevation of mountains, 

 being schistose towards the base, and arenilitic at 

 the summit. The sand-stone of a coarse grain, light- 

 ish grey color, and lesser dip, is likewise destitute 

 of organic remains. At Piatt's settlement, we came 

 in full view of a conic topped mountain, rising not 

 less than one thousand feet above the neighbouring 



