104 GREEN MOUNTAINS IN MASSACHUSETTS. 



Lastly, there is the limestone which on Greylock underlies and is inter- 

 stratified with the schists; we find this in Hoosic valley close to the gneiss 

 and quartzites, but no sign of it on the mountain proper. Reviewing the 

 evidence bearing on the position of the limestone, we have on Hoosac moun- 

 tain a conformable scries — granitoid gneiss, overlain by a white-gneiss-con- 

 glomerate-quartzite formation, and this by schist. We trace along the strike 

 the quartzite of Hoosic valley into this white gneiss-conglomerate-quartzite 

 series underlying the schists; and we also trace the same Cambrian quartzite 

 of Clarksburg mountain into white gneisses. This quartzite of Hoosic val- 

 ley we find in several localities passing upward into the limestone; it is Prof. 

 Dana's quartz rock which underlies the limestone. This quartzite we trace 

 also laterally into the Hoosac mountain white gneisses, and Ave find the schist 

 which borders the limestone of Hoosic valley in several conformable con- 

 tacts with the mountain quartzites and white gneisses with no intervening 

 limestone. We find near the contact of schist and limestone perfect trans- 

 itional feldspathic micaceous limestones (not all in place) and near North 

 Adams very close proximity of the schist belonging to Hoosac mountain with 

 limestone. There seeenis to be conformity between all the rocks, and vet 

 the limestone is wanting in the mountain section. The only solution would 

 seem to be that the limestone is replaced by the schist on the other side of 

 the line or plane mentioned above, whether it be an original shore line, or 

 some bounding line or plane of certain conditions of metamorphism peculiar 

 to the axis of the Green mountains. To bring in a fault or thrust plane at 

 tin- base of the Hoosac mountain, cutting off the crystalline rocks of the 

 Green mountains from the fossiliferous rocks west, is an easy solution of a 

 difficult problem, but not the correct one if the facts are correctly inter- 

 preted. 1 



There remain to summarize the facts bearing on the stratigraphy of 

 Hoosac mountain. The reasons for the conclusions as to the general struc- 

 ture of Hoosac mountain need not be recapitulated here; it is an anticlinal 

 fold, the axis of which lies nearly in the meridian. This axis is not horizontal, 

 but inclines or "pitches" (to borrow a term used for similar folds in the New 



'The reader is referred to Part I for a further discussion of the condition of the Hoosac and Grey- 

 lock columns. 



