526 



Scientific Geology. 



ceived their principal elevation previous to the deposition of the for- 

 mer. There may have been more than one epoch of / elevation pre- 

 vious to that time : but we are thus assured of at least one ; and the 

 very considerable inclination of the sandstone demonstrates an epoch 

 of elevation subsequent to its deposition. The last elevation seems not 

 to have affected the primary strata on the east side of the Connecticut 

 valley, except perhaps to a limited extent : for the force that raised 

 the sandstone was so applied as to lift up the western edges of the 

 strata : and if there had been a similar force operating on the eastern 

 side of the valley, their eastern edges would also have been thrown 

 up, at least so as to keep them in a horizontal situation, if not to give 

 them a westerly dip. 



All the primary strata, therefore, in Massachusetts, west of the val- 

 ley of Worcester, whose direction is north and south, I regard as be- 

 longing to the oldest meridional system : and such is the general di- 

 rection of all the strata west of Worcester, with the exception per- 

 haps of the argillaceous slate, and associated strata in the north part 

 of Franklin County, whose situation will be more particularly no- 

 ticed farther on. The Worcester County range of strata may not, in- 

 deed, have been elevated at the same time as the Hoosac range: but I 

 know of no facts that will prove that they were not raised at the same 

 epoch ; and since the direction of the strata coincides, we must refer 

 them to the same epoch until counter evidence be produced. 



I think that an examination of the annexed sections will lead to 

 the impression that the elevating force, or rather the force of plica- 

 tion, which has formed the ridges and furrows of the system under 

 consideration, must have operated in such a manner as to raise up 

 the mountain ridges on the east and west sides of the Connecticut valley, 

 much higher originally than the valley : for amid all the irregularity 

 that is manifest in the dip of the gneiss range east of that valley, we 

 see that the predominant inclination, particularly towards the central 

 and southern parts of the State, is westerly ; while on the west side 

 of the valley, it is the reverse ; although nearly vertical. This 

 does not prove that the part now occupied by the valley suffered 

 a depression at the epoch under consideration. For even if we sup- 

 pose it to have been elevated, a valley would have been the result, 

 if the strata on the east and west sides underwent a still greater degree 

 of elevation. At any rate, I think that the actual dip of the strata on 

 the opposite sides of this valley, render it probable that it was original- 

 ly a vaJley of dislocation and not of excavation : although, as I have 



