OF MARYLAND. 47 



have been quarried; but the masses are not large, the strata in 

 the upper portions of the formation being rather thin. It is 

 possible that at greater depths, tliey will present thicker and 

 more valuable beds. At the debouche of this valley, on the 

 Potomac, there is an extensive deposite of brown haamatitic 

 oxide of iron, wedged in, in nearly a vertical position between 

 layers of blue limestone. Similar ores have been found on 

 the west slope of the Blue-ridge. 



The excavations for the canal and rail-road both at Plarper's 

 ferry arid at the Point of Rocks, the former being the termina- 

 tion of the Blue-ridge in Maryland, and the latter that of the 

 Catoctin mountain, shew that the mass of the South moun- 

 tains is composed of primary rocks. These rocks are talcose 

 slates and quartz rocks, with slight indications of metallic 

 copper; epidotic and chloritic rocks, with amygdaloids, on the 

 eastern slope of the Catoctin and western slope of the Blue- 

 ridge, that are uncovered at the north extremity of the ridge, 

 whence having been detached, they form large bowlders in 

 the fork of the two chains; serpentine rocks; and finally gra- 

 nular limestone, occurring near the foot of the Catoctin on 

 the eastern side. The tops of this mass of mountains are 

 covered by a white remarkably compact sandstone, with veins 

 of crystalized quartz, and containing native copper, pyritous 

 copper, specular oxide of iron, &c. It is doubtless a meta- 

 morphic rock of an elder secondary period; its beds are very 

 much shifted, and its stratification quite undeterminable. It 

 does not appear to contain any organic remains. 



In the upper portions of Frederick-town valley the prevail- 

 ing rocks are the blue hmestone and red sandstone, and in the 

 vicinity of Mechanicksburg the limestone conglomerate, so 

 well known as the breccia of the capitol, consisting here of 

 calcareous pebbles of variable dimensions imbedded in an 

 indurated red shale, crops out in sundry places. East of the 

 Monocacy, on the branches of Pipe creek and Sam's creek, 

 near Liberty and New Market, variegated marbles of great 

 beauty are found. In the vicinity of New London, on the 

 Linganore, specular oxide of iron occurs, and lead has been 

 discovered in that of Union ville, while Woodsborough is the 

 centre of a limestone formation traversed by veins of sulphu- 

 ret of copper, that have already been worked to advantage. 



