ground for an hundred years without any material 

 change, it would not lose one inch in thickness during 

 the period of a thousand years : consequently, if all 

 the rocks upon the surface of this globe had been 

 composed of these varieties of sand stone, equally 

 exposed and liable to disintegration from the com- 

 mencement of time, or for six thousand years, we 

 should not, at present, have ten inches of soil from 

 this source upon the face of the earth. 



Among the red sand stones, there is a species of a 

 ferruginous slaty kind that is peculiarly subject to 

 disintegration from the above causes. It occurs in a 

 number of places in these United States, and perhaps 

 in every other country : but mostly I believe in what 

 are considered coal districts. 



It occurs in Frederick county (Maryland) on the 

 Monocasy, near Pipe Creek, having a declination of 

 about 40 or 45. It is also abundant in New-Jersey 

 about New-Brunswick, on the Haritan river and else- 

 where. It likewise occurs in Connecticut, running 

 in a N. E. direction and crosses the Connecticut river 

 between Suffield and Windsor. Also below, and in 

 the town and city of Hartford. Where this rock is 

 exposed to the weather, the covering or upper strata is 

 particularly disposed to be broken up in small rhorn- 

 boidal, or quadrangular laminae, which in some in- 

 stances form a complete covering to, and screen the 

 rocks below from the further operations of the weather, 

 by their being below the limits of frost. There are 

 some other kinds of the schistic rocks which, in like 



