Report on the projected Survey of the State of Maryland. 21 



analogies in mineral constitution with the gold districts of Virginia. 

 The undersigned can only say, that in the rapid reconnoissance 

 which they were enabled to make of this part of our state, they have 

 not seen the least indication of the presence of this highly prized met- 

 al. — Three miles westward of Rockville, there is a serpentine forma- 

 tion, which in a systematic plan of examination, it would be necessa- 

 ry accurately to define. Beyond this the geological character of the 

 country changes. Slate rocks make their appearance, and at the 

 mouth of Seneca creek, the quarries of beautiful /rees/o/ie, which the 

 facilities of the Chesapeake and Ohio canal permit to be brought to 

 such profitable account as a building material, exhibit the mineral 

 connection of this portion of Montgomery county with another geo- 

 logical division of the state of Maryland. 



This division, the third in the order of this Report, will coincide 

 with the limits of Frederick county. In its mineralogical and geo- 

 logical relations, it is intimately associated with the preceding divis- 

 ion, which has been previously stated to consist of primary rocks. 

 At its eastern boundary it commences with the clay slates and chlo- 

 rite slates, usually classed among the primary rocks. With these it 

 passes insensibly into that series of rocks described in systematic 

 works under the head of the grauwacke groupe and from these again 

 to the red sandstone, and carboniferous groupes. 



In a scientific point of view it would be a matter of great interest 

 to assign the precise line of demarcation between these different 

 groupes of rocks : while the practical application of the result would 

 also prove of importance. The task however, is not an easy one, 

 owing to the fact already mentioned, of the very gradual passage of 

 one series into the other; nor for present purposes is it required. 



This division, then, viewed generally, may be described as con- 

 sisting of large stratified masses of arenaceous and slaty rocks, in- 

 termixed with deposites of limestone and conglomerates of consid- 

 erable €xtent. Many of the rocks embraced within it are metallif- 

 erous. 



Among the arenaceous rocks which it comprehends, there is an 

 abundant supply of excellent building materials — rendered now avail- 

 able in the facility of transportation by the Chesapeake and Ohio ca- 

 nal. It is not necessary to indicate more than a few localities. 



The quarries of white and colored sandstone, at the foot of the 

 south western slope of the Sugarloaf mountain, may be said to rival, 

 in the beauty of their materials, those already mentioned, as occur- 



