GEOLOGY OF THE WHITE MOUNTAIN DISTRICT. 263 



occurrence of moment in this district. Its paste bears some resemblance 

 to the Albany granite. Inasmuch as fragments of porphyry occur in it, 

 the ejection of the paste must have been subsequent to the pouring out 

 of the compact feldspars over the Mts. Twin, Lafayette, Tom, Carrigain, 

 and other areas. 



Last Period of Elevation. 



We have already described a very important period of elevation at the 

 close of the Montalban period. There have been two later ones in Pal- 

 eozoic times of considerable importance, of which little is known. The 

 first is the disturbance which performed most of the elevatory work upon 

 the andalusite slates of Mt. Washington. It was probably coeval with the 

 eruption of the Pemigewasset granites. Such an enormous amount of 

 melted matter came forth at this time, that the convulsions attendant 

 upon it must have equalled those occurring at the close of the Montal- 

 ban period. Upon examining the strata in western New England, we 

 find evidence of upheaval at about the close of the Lorraine period. This 

 may have been the same with the one in question. It is the most prob- 

 able one of all that are known to have elevated our formations. 



The latest epoch of elevation in these comparatively early times must 

 have occurred in the Devonian era, and it was one of great importance. 

 All New England and the middle Atlantic section was deeply submerged 

 before the deposition of the Helderberg limestones. The widespread 

 coralline limestones throughout this section indicate this, and we can 

 find no evidence of a greater submergence after Eozoic times. This 

 section must have been vigorously crowded after the deposition of the 

 Helderberg rocks, since they have all been elevated at a considerable 

 angle. They stand vertical in Littleton, and as high as seventy-five de- 

 grees in many parts of northern Maine. In that state we find resting 

 upon them, at small angles, the middle or upper Devonian sandstones. I 

 find I have remarked concerning those that are developed near Eastport, 

 in my first report upon the geology of Maine, that "they seem to have 

 been spread over the Silurian [Helderberg] rocks, just as alluvium is 

 spread over the solid ledges." There is positively less inclination to 

 many of these sandstones than to the Connecticut Valley sandstones of 

 a much later age. 



Now, as the Helderberg rocks occur at a considerable distance from 



