northerly as one stands at the base of the granite cone of Mount Ascutney. Such a sheet would stand at about 1,100 or 1,200 feet at Ascutney and rise gradually to Thistle Hill in Pomfret, 2,000 feet, sloping very materially to the Connecticut. From Thistle Hill its elevation would be much the same through Norwich, rising in Strafford and culminating in Colton Hill, Vershire, at the altitude of 2,412 feet. It may be conceived that the variable heights of the peaks in this section have been determined by their hardness or ability to resist erosion. Thus Thistle Hill may have been originally of the same altitude with Colton Hill, but the former is now lower because of its greater susceptibility to decay. And there are considerations leading to an understanding of an approximate limit to the early upper surface, based upon the geological history of such elevations as Mount Ascutney, Brocklebank Hill and the great granite area east of Montpelier. These eminences have a granite core known geologically as a batholith. When soft this material filled cavities below the surface and was prevented from escaping by walls of the rocks surrounding the igneous core. Were the heated mass like a modern volcano the lava would flow from the surface. In case such a flow ever existed over the batholiths all traces of the streams would have disappeared long ago, and the fact still remains that the igneous core was kept in place by the enveloping rock. Upon considering the altitude of this ancient plain it must have been higher than the top of the batholith; or in the present instance a few hundred feet higher than the top of Mount Ascutney, say 3,500 feet above the present sea level. The core resisted decay far more than the adjacent rocks, so that now the granite remains at 3,186 feet, while the highest points of the adjacent peneplain range from 1,200 to 2,000 feet. In other words the rock has been excavated over the Hanover quadrangle from 3,500 feet down to the present surface, or nearly 3,000 feet at the Connecticut at Windsor and 1,200 feet at Thistle Hill. And it is easy to show that the erosion over the whole of the surrounding country, or New England, has been as great-probably greater than over our quadrangle. Though of enormous proportions erosion has been much greater over the Cordilleras region on the west side of the continent. The rocks of the quadrangle have been extensively folded and faulted and are usually tilted more than forty-five degrees, being both stratified and unstratified. A few years ago the order of the formations seemed to have been well made out and they were correlated with both the Archean and the Paleozoic. With greater knowl edge the Archean has been excluded because the foliated schists so referred are found to contain fragments of the latest stratified rocks occurring in their neighborhood. These inclusions bear witness both to the igneous character of the rocks and to its late origin. There are no fossils in any of the later groups, so suggestions as to their age cannot be decisive. Under these circumstances, it is not possible to do more than to classify the groups according to mineral characters, with hints as to their probable age derived from the supposed continuations of the strata from Vermont into the adjacent regions of Canada and Massachusetts where they may have been satisfactorily made out. For convenience the rocks may be arranged as follows: 1. The hydro-mica, chloritic, and sericite schist groups. 2. Argillites. 3. Coös mica schists. 4. Calciferous mica schist [Conway]. 5. Coös quartzite. 6. Conglomerate group. 7. Amphibolites. 8. Granite. 9. Basic dykes. CHLORITIC GROUP. Petrographically this will indicate hydro-mica, chloritic and sericite schists, igneous protogenes, diorites, diabases, sandstones of various degrees of alteration, argillitic schists, hornstones, quartzites and limestones, constituting truthfully a complex. In the Vermont Reports it had the general name of Talcose schist; in the New Hampshire Reports it was known first as the altered Quebec group of Canada, afterwards as Huronian, and locally the Lisbon, Swiftwater and Lyman schists, all in the Connecticut Valley, in distinction from a similar broad area extending through Vermont from Canada to Massachusetts. The two ranges have been supposed to be of the same age connected as a synclinal fold beneath the various mica schists. Only the eastern range appears upon the Hanover quadrangle. As to age, provided the two ranges are indentical, it may be partly Cambrian and partly Ordovician; at least the geologists of Canada and Massachusetts give these references to the same rocks within their limits, the latter not using the term of Cambrian for them. As nothing new in respect to its age can be learned from our studies upon this quadrangle, it is not needful to insist upon its precise place in the geological column. Without fossils it is always difficult to recognize the age of any metamorphic group, based as it must be upon petrographic resemblances and stratigraphical relations. This chloritic band enters Norwich at Union village with a width of a mile and one fourth, and then very shortly reaches our quadrangle just west of the Poor Farm. It extends through Norwich and Hartford with a slightly broader area adjacent to the Connecticut and passes over into New Hampshire at the great bend in the river about North Hartland. It is continuous through Plainfield into Cornish. The planes supposed to be those of stratification are tilted at high angles, commonly near to vertical, and it will be well to mention all that have been observed in detail, beginning at the north end, in East Thetford, along the route of Section VII of the Dartmouth College Museum. The structure seems to be anticlinal. Along the south line of Thetford the chloritic rocks at the east border are massive, with no apparent strata. There are as many as twenty ledges of this sort in S. H. District No. 3. To the west is a chlorite schist, dipping 78° S. 45° E., followed by novaculite, argillitic schists, slaty layers much bent and dioritic schists on the hill overlooking Union village. On both sides of the Pompanoosuc River at Union village the strata are vertical with the strike N. 80° E. The western border dips very high to the N. W. In Norwich close by the hill overlooking Union village are chloritic and dioritic schists, dipping S. E. In the southeast corner of the Strafford sheet near the Norwich Poor Farm the sericite schists are very nearly in contact with the mica schists to the east, along a deep, narrow valley. The former are bent into small contortions, averaging 80° easterly dip, while the latter dip as low as 50° to the west. There is probably a fault here, rather than an unconformity. The strikes of the two rocks are different. A section from Bradley Hill to Blood Mountain, fig. 4, near the northeast corner of the quadrangle shows the relations of the several rocks to each other. On the west side of Bradley Hill are the argillites. On the hill itself are the chloritic schists, slightly argillaceous, with the dip N. 50° E. At the cross roads the schists are more sandy, vertical. Farther east they are much twisted, 70° N. 30° W. An anticlinal next, the sandy schists at J. O. Johnson's dipping 85° S. E. The same at O. Seaver, followed by a band of argillite, 80° Green Schists. N. 38° W., where measured, but probably a synclinal, as everything on the east side dips 70° N. 40° W., especially by the old S. H. No. 5, on the Thetford road. The schists are massive and chloritic here. There must be a fault on the east border of the green schists, as they come in contact with the Coös mica schists, a band of rock terminating beneath the modified drift west from Tilden pond. East of the slate band the chloritic rock is rather ill defined all the way from the great bend of the Connecticut near Loveland's down to the Ledyard bridge. Near the first island there are the quartz schists altered by contact with hornblendite and dolomitic appearing material minutely contorted with easterly dips. This is all to the east of a band of argillite. On the west side the dips are all northwesterly to the edge of the formation near schoolhouse No. 4 composed of the following varieties: Argillitic schist, bands of chlorite schist, green chlorite, the same becoming white when weathered, brownish layers more siliceous, granite bunches, large white quartz veins, massive and slaty chlorite, massive argillite schist, steatite and chlorite schists. The width directly across the formation, section 1, is a mile and a quarter, with the average dip of 70° at the steam sawinill and at the turn of the road to the village of Norwich there is a wide belt of schists altered to epidotic, serpentinous and brecciated masses, east of the same argillite noted above. To the west the schists are chloritic, sandy and argillitic back of the village, especially to the east and north, and the strata are nearly vertical. The following positions were noted here: 70° N. 57 W., 90° with strike N. 5° W., 78° N. 40 E., 90°, and 50° N. 60 W. The very western border |