OF ARKANSAS. 45 



3. Sandstone, hard and quartzose. 



4. Variegated shales, including the Terra Sienna earth and segregations 



of hydraulic (?) limestone, and some mudstone shale interstratified. 



5. Thin-bedded, light-grey limestone. 

 G. Buhrstone, G to 8 feet thick. 



7. Light-colored magnesian limestone, of silurian date? 



8. Compact, flinty siliceous rocks. 



J. E. Ware is of opinion, the best quality of buhrstones, of any required 

 dimensions, can be obtained either in Camp creek hollow or the ridges 

 opposite his flouring mill, on the North Fork, equal in quality to the 

 French buhr. 



Small particles of sulphuret of copper have been picked up by J. E. 

 Ware, in the Camp creek hollow, disseminated sparingly in a gangue of 

 calc-spar; but no regular vein has, as yet, been detected. 



MARION COUNTY. 



The prevailing rocks of this county are varieties of magnesian lime- 

 stones, which crop out in terraces and low cliffs on the sides of the hills. 



Some sandstone is intercalated, chiefly towards the upper and lower 

 part of the hills. The upper sandstone is of variable thickness, from a 

 few inches to 50 or 60 feet. It appears, in many places, as if the under- 

 lying magnesian limestone had suffered from irregular denudation; having 

 been locally scooped out into deep hollows, into which sand was subse- 

 quently swept, and became, afterwards, indurated into a hard, solid rock. 



The lower sandstone I have only had a good opportunity of examining, 

 as yet, in the adjacent county of Carroll, on township 20 north, range 18 

 west, of the 5th principal meridian, where it has the hard quartzose 

 character of the lowest sandstone of Wisconsin and Minnesota, as it 

 occurs on the Minnesota, Baraboo, and Wisconsin rivers. 



The upper sandstone is generally overlaid by limestones, capable of 

 receiving a good polish. Some of the beds are pink, variegated with 

 white, or light grey; others, nearly white, or light grey, and often studded 

 with tntrocfiitcs: that is, the disjointed stems of those singular flower-like 

 animals, known by the name of encrinites, which flourished in such pro- 

 fusion in the ancient seas, in which the deposits and chemical precipitates 

 were accumulating, that produced the so-called silurian, devonian, and 

 carboniferous rocks. These contribute greatly to the beauty of the 

 marble of which they form a part; appearing, often, of different shades of 

 color from the matrix in which they are enclosed, and giving to the roek 



