structure of this kind of rock, the nature of its mate- 

 rials, and the exquisite polish of which it is suscepti- 

 ble, we shall not be surprised that sculptured speci- 

 inens of it have been preserved entire, amid the ruins 

 of ancient cities, for three thousand years ; nor hesitate 

 to admit, that if there be a substance in nature, capable 

 of resisting the all-powerful influence of time, it is that 

 of porphyry.* 



Among the variety of other kinds of rocks that com- 

 pose this ridge of mountains, and which have in like 

 manner withstood the changes of seasons and the in* 

 tensity of frost, is one that is highly interesting in this, 

 as well as a geological point of view. It is a species 

 of sandstone with an argillaceous cement, occasionally 

 striped and handsomely variegated with the oxid of 

 iron. It has been remarked, that it occurs opposite to, 

 or about eight or nine miles east of Hagerstown, Mary- 

 land, t There is reason to believe, however, that it 

 prevails at nearly the same elevation to a great extent. 

 I have found that the top of the Sugar Loaf, a conical, 

 high, and isolated mountain in Frederick county, Ma- 

 ryland, about seven miles east of the South Mountain, 

 is composed of this kind of sandstone. I also find it 

 upon the highest points, only, of the same ridge in 

 Pennsylvania ; so that in every instance it appears at 



* In describing some of the ruins of Egypt, Lord Valentia ob- 

 serve-, ;< near it was a Marahout, the dome of which was supported 

 by four jasper columns, t'-e polish of which was as perfect as on the 

 daij they were finished." Vz\*r\t. Trav. Vol. III. 



t Cleaveland's Mineralogy, p. 624. 



