Systems of Strata in Massachusetts. 



525 



stance, as in the case of the limestone of Berkshire county, I have not 

 seen the actual junction of different rocks, I have left a blank space 

 between them. Notwithstanding these precautions, I am afraid that 

 these sections will convey some erroneous impressions. 



The principal object of these sections is to exhibit the actual dip of 

 the strata : and this I have endeavored to give without reference to 

 the distortions of the surface. 



Systems of Strata and Mountains of Contempora?ieous Elevation in 



Massachusetts. 



A careful examination of the map and sections that have just been 

 described, will satisfy any one, that although the rocks of Massachu- 

 setts belong to several distinct systems of elevation, yet the central 

 ridge, or anticlinal line of not one of these systems perhaps, passes 

 through the State. We may, therefore, hope that correspondent parts 

 of these systems may be discovered beyond the limits of the State. 

 But I shall first endeavor to point out, as well as I am able, in chro- 

 nological order, the different systems that appear within the State. 



A peculiar difficulty, however, meets us in attempting to ascertainthe 

 relative epochs of elevation of our strata : for most of the newer strata 

 are wanting in New England; or rather their number is much less 

 than in some other parts of the world. In the western part of this State, 

 for instance, we have only the new red sandstone and a single tertiary 

 formation, not yet identified with any in other parts of the world, to 

 guide our enquiries in respect to the epochs of elevation. And in the 

 eastern parts of the state, graywacke alone affords us any assistance in 

 this matter ; since the plastic clay and every other tertiary formation 

 are so insulated from the older rocks, as to form no grounds for any 

 other than hypothetical conclusions. For these reasons I find it impos- 

 sible to ascertain the exact place in respect to time, which all the sys- 

 tems of elevation, that I think I discover in the State, ought to occupy. 

 Most of these systems appear to be of great antiquity; corresponding 

 perhaps with the oldest that have been described in Europe. 



1 Oldest Meridional System. The meeting of the new red sand- 

 stone of the Connecticut valley with the primary strataof Hoosac moun- 

 tain range in an unconformable manner, enables us to infer with cer- 

 tainty, that the latter have suffered at least two elevations at different 

 epochs. For the sandstone has a medium easterly dip of 15 Q or 20°: 

 while the mica slate, talcose slate, and gneiss of the Hoosac range, 

 approach to vertically in their dip. Hence the latter must have re- 



