254 STRATIGRAPHICAL GEOLOGY. 



in Gilead. We have, therefore, a problem of this nature: Given, a for- 

 mation about forty-five miles wide. One third of the width on the west- 

 ern side possesses a north-westerly dip, with at least two newer bands 

 disposed within it. The other two-thirds width on the eastern side pos- 

 ses a south-easterly dip, with supposed newer bands of unknown number. 

 The structure of the whole mass is certainly anticlinal in aspect ; but the 

 western part has not more than half the thickness of the eastern, and 

 there are evidences of synclinals in it. The proper explanation of these 

 phenomena would seem to be that inversion is the normal condition of 

 the whole area. A somewhat local pressure might produce a uniformly 

 inverted dip in the western area. Independently of this, other peculiarly 

 acting forces might invert the eastern area with its subordinate bands in 

 the other direction. I think it will be shown farther on, that this main 

 anticlinal line is the place for the subterranean development of the Lake 

 gneiss, or one of the other lower groups. This fact would indicate a ris- 

 ing of the underlying terrane, but not sufficient, perhaps, to bring it to 

 the surface in the elevatory period, while in the formative epoch the 

 older series existed as a shoal or island, upon both sides of which the 

 same kind of Montalban schists was being deposited. To the south-west, 

 the lower formation now crops out at the surface ; but from Tamworth, 

 across to Oxford county, Me., the upper schists covered it, perhaps be- 

 cause of its submergence. Granting this explanation, it is easy to under- 

 stand how, in the later elevatory periods, each side of an anticlinal line 

 should be inverted separately, and the forces exerted so that the inclina- 

 tion shall be in opposite directions. A similar example is afforded by the 

 Connecticut Valley and New Jersey Triassic areas. The former basin 

 invariably dips easterly, the latter westerly, while there is a broad area 

 of older rocks between. The question has been raised whether each of 

 these Triassic areas has not been inverted. If it is possible that each 

 one could be inverted, so that the apparent dip shall be in opposite direc- 

 tions, much more truthfully can the same supposition apply to the two 

 flanks of the Montalban anticlinal, where inversions are the rule rather 

 than the exception. 



By measuring the course of the waved strata upon the cast side of Mt. 

 Washington, we can determine the direction in which the force of eleva- 

 tion has been exerted. The course of the range is about N. N. E.; and 



