176 AN AMERICAN GEOLOGICAL -RAILWAY GUIDE. (MD. & D. C.) 



5. The Western Maryland Railroad has copper mines, chrome, serpentine, talc, steatite, 

 asbestos, carbonate of iron, and most beautiful marbles of every color, from black, dark red, 

 salmon, &c., to pure white even statuary marble besides the breccias of every degree of size in 

 their component pebbles or pieces, both round and angular. P. R. U. 



6. By Prof. William M. Fontaine, of Morgantown, West Virginia. 



7. Baltimore is situated near the junction of the Azoic metamorphic rocks, with a series of 

 clays and sands, underlying the cretaceous beds. The age of these clays has not been fixed. Some 

 consider them to be Lower Cretaceous, others Upper Jurassic. They are probably Upper Jurassic, 

 and not far distant in age from the Fredericksburg sandstones of Virginia. The surface clays in 

 South Baltimore are probably of Post Pliocene age. 



8. The rocks of the eastern portion of the Azoic area in Maryland, as in Virginia, are granites, 

 gneisses and hornblendic rocks, probably of Laurentian age. This belt extends to near Parr's 

 Ridge, where it is succeeded by Argillites, with some metamorphic limestone, probably of 

 Huronian age. This latter belt extends to some one and a half miles west of Harper's Ferry, 

 where it is succeeded by the Primordial and overlying strata. 



9. The Azoic area passes some distance to the west of the railroad from Baltimore to Wash- 

 ington, consequently this road runs entirely in formations similar to those found at Baltimore. 

 Washington has a geological position similar to that of Baltimore, but here the subjacent rocks 

 are plainly similar in age to the Fredericksburg sandstones, and are probably Upper Jurassic. 



10. On the west side of the Monocacy River a belt of Triassic rocks occurs, extending to near 

 the east base of the Catoctin Range. Along the west margin of this belt occurs the remarkable 

 limestone breccia called the Potomac Marble. This is well exposed near Point of Rocks. This 

 Triassic belt is flanked immediately on the northeast and east by a belt of rather impure slaty 

 limestone, belonging to the Azoic area. 



11. The gorge at Harper's Ferry is cut through metamorphic rocks, of probably Huronian ape. 

 One and a half miles west of the station, a fault brings down the Potsdam and Calciferous rocks 

 against the Azoic. From this point, 83 miles, to near North Mountain, 107 miles, a wide belt of 

 Lower Silurian limestone occurs, with occasional bands of slate, embracing the rocks from the 3 a. 

 Calciferous to and including the 4 c. Hudson River. These have never been separated in this 

 region. The limestone predominates by far, and will be spoken of as the 2^1. Siluro-Cambrian. 



