51 



the slate, it is passed by for the present, with the remark that the 

 general direction of the cleavage planes in the limestone follows 

 strictly that which prevails almost universally in the slate, the 

 dip and strike of these planes of cleavage being in both formations 

 entire, independent of the direction of the dip of the strata. 



Axes of elevation affecting the Formation. — Seeking by the study 

 of the external phenomena of a formation, to understand either 

 the revolutions in the past physical condition of its district, or the 

 present structure of that portion of the earth which it constitutes, 

 we shall find it essentially important to examine in an early stage 

 of the inquiry, the nature, extent, and relative situation or direc- 

 tion of all the axes of elevation, which may disturb its beds from 

 their original nearly horizontal position. These axes of elevation, 

 marking the lines along which tiie subterranean forces have ex- 

 erted themselves in their greatest energy, are the surest guides 

 we can possess, not merely to the changes which the strata may 

 have undergone, both of displacement and of alteration of struc- 

 ture; but to the existing position of every thing they may regu- 

 larly include, whether it may interest science only, or prove 

 particularly useful to the wants of man. They show us what 

 portions of the formation have become deeply buried beneath the 

 surface, and often at what depths, whether accessible or inacces- 

 sible, and they inform us what portions of the formation have 

 been removed from the surface, by the crushing and washing 

 away of the strata along the lines where they were most up- 

 lifted. They constitute, in fact, an indispensable clue to the 

 operations of the miner, the quarryman, and even the road- 

 maker, in every much convulsed district where they may abound. 



As, therefore, the primary chain of the State, and the whole of 

 the great valley which borders it upon the northwest, arc tra- 

 versed longitudinally by a most extensive system of such axes, 

 lying mutually parallel and closely contiguous, and connected 

 intimately with nearly every point in their geological structure, 

 both general and local, I deem it important to introduce here a 

 systematic enumeration of all such as are of much note, intend- 

 ing, as I proceed, to exhibit their relations to the disturbances 

 and changes of structure, caused in the adjoining strata. 



Pursuing our usual course, from the northeast towards the 

 southwest, and examining first the southeastern belts of the forma- 



