Description of the Bare Hills. 351 



kind is seen to interrupt the view, or change the barren aspect of 

 this solitary waste. 



About midway from the summit to the base of the hills, on the 

 north, an excavation was commenced in the rocks, in making the 

 turnpike road, and which, as we descend the hill, deepens and 

 exposes the rocks upon the right hand, to a considerable depth, 

 thereby affording an excellent opportunity of examining their struc- 

 ture and composition, which is, perhaps, as interesting as that of any 

 other place, that has hitherto been exposed to view in this district. 



At the base of the hill, where the serpentine formation terminates, 

 the road passes over a small stone ■ bridge of one arch, and under 

 which runs a brook or small stream of water that comes from the 

 hills to the west, constituting an auxiliary branch of Jones's Falls, 

 with which it unites at a short distance east of the bridge. Thence 

 the stream pursues an easterly direction, at the base of Bare Hills, 

 and so passes around the eastern slope in a semi-circular course, un- 

 til it crosses the turnpike road at the base of the southern slope, 

 near the point at which the rail road intersects the turnpike. 



I have remarked, that on arriving at the summit of the hill, 

 we observe the commencement of the serpentine formation. As 

 such, it has hitherto been considered, and is uniformly well un- 

 derstood. But, in order to avoid exceptions which may hereafter 

 be made to the character given to these rocks, it seems necessary 

 that I should be a Httle more explicit as to their true character. With 

 this view, I venture the opinion that the aggregate formation of the 

 rocks of Bare Hills is not strictly serpentine. It is true, that real 

 serpentine exists in this district, and that even noble serpentine, in 

 small specimens has been found here ; but, the aggregate mass of 

 the rocks of these hills, according to the classification of Brongniart, 

 to which I know of no one that is preferable, falls under the denomina- 

 tion of ophiolite, which he describes as being " a paste of serpentine 

 enveloping oxidulous iron and other accessory minerals dissemina- 

 ted :" — Hence Brongniart describes as " principal varieties," ferrife- 

 rous ophiolite, chromiferous ophiolite, diallagic ophiolite and gametic 

 ophiolite — all of which, with the exception of gametic ophiolite, are 

 found, at nearly every point of the Bare Hills. The chromiferous vari- 

 ety seems most abundant; for the rocks, in nearly the entire district, on 

 being broken, present the granular chromate of iron, as a component 

 part. 



