664 STRATIGRAPHICAL GEOLOGY. 



the porphyritic rocks seem to clip beneath them. If the relations between 

 these two sets of rocks are properly represented in this figure, the greater 

 antiquity of the porphyritic series is established. For want of better evi- 

 dence, we have accepted this as decisive, and must so regard it for the 

 present. The porphyritic gneiss of Winchester is partially encircled by 

 the Bethlehem group, a fact that confirms the conclusion obtained from 

 the Wing Road section. Our order, as now set forth, is the following: 

 After porphyritic gneiss, the Bethlehem, Lake, and Montalban series. It 

 may as well be said now as at any time, that nothing older than the por- 

 phyritic gneiss has yet been discovered. This formation constituted the 

 first dry land in the state, as has been set forth in the first volume. 



Another set of groups are the argillaceous, talcose or hydro-micaceous 

 and calcareous series. Along the Connecticut river are the Lisbon and 

 Lyman hydro-mica schists or greenstones, to use Mr. Hawes's proposed 

 terminology. The same occur more abundantly along central Vermont 

 east of the Green Mountains, characterized by the presence of serpen- 

 tine, soapstone, and dolomite, which are found likewise in the eastern 

 band. These two bands must be of the same age. Their dips are not 

 constant, so that their relations to each other must be determined by 

 the relations of the rocks between. Adjoining the greenstones, towards 

 each other, are narrow areas of clay slate. Between the two slates the 

 rock is mostly the Calciferous mica schist, with occasional bunches of 

 eruptive granite. A careful analysis of all the dips across this cal- 

 careous group shows the structure to be synclinal (p. 402). The very 

 large area of granite in the central part of this group is found showing 

 itself from Section VII to Section XI, ridging up the strata just as might 

 be expected from igneous action in connection with lateral pressure. 

 Now if the central group, twenty miles or more in width, extending more 

 than half through the state with this breadth, is a proper synclinal, and 

 the two groups adjacent on both sides are the same, we have the most 

 positive evidence in favor of the greater antiquity of the outer rock or 

 the two greenstone ranges. 



There is no portion of this report more carefully prepared than what 

 relates to these greenstones and associated rocks in the Ammonoosuc 

 field. Our observations may be generalized thus: There is a basin 

 about ten miles wide, with several subordinate flexures, having the Lisbon, 



