CLASSIFICATION OF THE NEW HAMPSHIRE FORMATIONS. 663 



the first-named rock capped the others. To make that view consistent, 

 the Montalban rocks should always dip beneath the Lake series, in local- 

 ities free from suspicion of inversion. Such are in Gilsum (Section III), 

 the Salisbury gneisses notching into the Montalban (p. 532); the well 

 marked anticlinal of Milan and Berlin, where the latter rock does not 

 press closely upon the gneiss ; and other cases. Hence the porphyritic 

 gneiss cannot be the superior rock. Next we have the relations of 

 the porphyritic gneiss to the Montalban, as in the great synclinal in 

 Fig. 95, between Alexandria and New Hampton, the latter being up- 

 permost, and likewise between Ellsworth and Sandwich, where the same 

 truth is apparent. Near Thorndike pond in Jaffrey the porphyritic gneiss 

 is distinctly synclinal beneath the Montalban. Consider, also, the mutual 

 relations of these groups in other particulars. In Warner and Bradford 

 isolated basins of Lake gneiss repose upon the porphyritic gneiss (Fig. 

 85), which is inconsistent with the notion that the former is underneath 

 the latter. Between the Center Harbor and Ashland ranges (Section 

 VI) the Lake gneisses are forced to conform to the porphyritic series, 

 though at the very western edge of the Lake series is a local anticlinal. 

 This agrees with the curvature of the porphyritic band from Ashland 

 through New Hampton and Meredith. The numerous examples of iso- 

 lated porphyritic areas can be explained best by their inferior position to 

 the adjacent schists. Some of them are arranged in lines, as from Web- 

 ster through Hopkinton and Weare to Greenfield. 



From these facts it is inferred that the porphyritic gneiss is older than 

 either the Lake or the Montalban gneisses, the last being the newest 

 Accepting this as a starting-point, we can understand the origin of the 

 usual fan-shaped structure, arising from enormous pressure and subse- 

 quent denudation. (Further remarks to the point occur upon p. 529.) 

 Numerous other cases of inversion and complicated structure make them- 

 selves clear after accepting these conclusions, which have been stated in 

 the body of the report. 



The place of the Bethlehem gneiss areas is not perfectly clear, though 

 probable. They occupy the Connecticut valley to the west of the por- 

 phyritic gneisses. In only one place can we find the two ancient gneisses 

 in contact, and that has been represented in Fig. 7, Plate VI. Between 

 Franconia and the Wing road are monoclinal Bethlehem gneisses, while 



