;310 REMARKS ON SANDSTONE AND 



lique, Haiiij. It appears, in tlie limited district whic'i we 

 examined, under almost every variety of form and character 

 ever noticed by o;eoloij;ists. Sometimes it is neatly free 

 from any intermixture of hornblende, and is of a tine dark 

 green colour, nearly resembling some varieties of serpen- 

 tine. 



Its minute structure Is often manifestly crystalline ; in 

 which case its fracture is granular. In other instances its 

 particles are not |)erteptibly crystalline, and the fractuie is 

 earthy. Sometimes its colour is a dull grey, giadueiting into 

 brown and black of vaiious shades and intensities. Tiiis 

 rock forms numerous conic hills of considerable elevation, 

 which are irregular in height, and scattered without order in 

 various parts of the plain. These hills are usually of a re- 

 gular and beautiful form. The great plain in vvhich they 

 stand is elevated, and destitute of tintber or water, but oina- 

 merjted with a thick and verdant carpet of grasses and other 

 heri)acious plants. The hills, though steep and high, are 

 sn)ooth and green to the summit, their surface being nearly 

 unl)roken by rocks, and covered with thick turf. The whole 

 forms a scene of singular beauty. During our journey across 

 that district of country which is l)ased upon the rocks now 

 under consideration, we had constant occasion to admire the 

 exuberance and freshness of vegetation. The plains of the 

 Platte and Arkansaw we had seen brown and desolate as if 

 recently ravaged l)y Hre, yet here we passed elevated tracts 

 having a scanty soil, and scarcely affording water for our ne- 

 cessities, yet the vegetation possessed the freshness of spring 

 in the most fertile regions. 



The conic hills above mentioned are not the only nor in- 

 deed the most common form under wliich the greenstone 

 appears. It sometimes forms low ridges extending a con- 

 siderable distance, and slopiirg gradually on l)oth sides into 

 the level of the plain. In the narrow channels which the 

 strf-atTis of water have sunk in it may be seen perpendicidar 

 precipices of considerable elevation : but the valleys are usu- 

 ally much obstructed by large broken masses of the rock 



