S4 GEOLOGICAL STRUCTURE OF THE 



cient in springs of water. While on the contrary, 

 the calcareous country of the Salaiseau, of Grand- 

 river, of the Illinois, of Arkansa, and also the undu- 

 lated arenelitic lands towards the borders of the great 

 Saline river, abound in springs, that continue to flow 

 throughout the hottest months of the summer, and 

 produce around them morasses, which from their de- 

 ceiving depth, are dangerous to the appioach of the 

 larger quadrupeds. 



While ascending the Missouri in the summer of 

 1810, I could not ascertain the existence of the com- 

 pact calcareous rock, containing organic reliquiae, 

 beyond the confluence of the river Platte ; yet the 

 sand-stone hills, and woodless plains, in the rear of 

 the Maha village, were precisely such as we met with 

 along the northern borders of the Arkansa, within 

 the limits of Pottoe, and the Saline rivers. In the ter- 

 ritory of Arkansa we could no where distinctly ascer- 

 tain the existence of those more ancient and deep beds 

 of uniform argillaceous matter which so often along the 

 banks of the Missouri, bury out of sight the inferior 

 rocky stratum, in such a manner, as at length entirely 

 to conceal its character. This clay formation, en- 

 tirely unconnected with that of the Mississippi, and 

 the lower part of the Arkansa, is of a blueish-grey, 

 abounding in pyrites and xylanthrax, and is the 

 active seat of those pseudo- volcanoes and their re- 

 mains existing in the upper part of the Missouri ter- 

 ritory. Excepting wood, even whole trunks of trees, 

 in every state of siliceous penetration and petrifac- 

 tion, a fossil Ostrea or my a, and what my friend Mr. 



