No. 104.] 171 



ning at the Connecticut lino east-north-east of Amenia, the western 

 boundary lino crosses the Kent Plains and Amenia road one and a half 

 miles east of South Amenia. Thence it runs in a south-south-west 

 course along the base of the Peaked Hill ridge ; intersecting the road 

 to Macedonia, three-fourths of a mile soutli of South Ameuia ; then 

 striking the East mountaiu it follows the course of the mountain, first 

 in a south-south-west, then in a south course, and lastly in a south- 

 easterly direction, to the southern termination of tlie range, near 

 Webotuck. East of Dover Plains it has an average elevation of 550 

 feet above the plains level. On Peaked hill and on Dover mountain 

 quartzite borders the gneissic outcrop. See Jlafher^s Geology of the 

 First District Natural History of New York, pp. 444 and 446. Also 

 Percival's Geology of Connecticut, pp. 118, 119; Prof. J. D. Dana's 

 " Taconic Rocks and Stratigraphy,'" Am. Jour. Science (3), XXIX, p. 

 209. And these two formations were observed in close proximity to 

 one another at several points on this side of the mountain. Contact 

 phenomena were noted at a place near the road leading from the 

 mountain district school-house to Dover Plains. The gneissic strata 

 were found in all but one locality, dipping to the east-south-east and at 

 angles varying from 60'' to vertical. One locality showed a dip of SO** 

 westerly. On Peaked hill the quartzite beds dip to the east-south-east 

 at an angle of 40° ; the.gneiss east of the quartzite has the same direc- 

 tion in dip, but the amount is 50°. Along the west side of the East 

 mountain the dip of the quartzite strata is 50° to T0° and toward the 

 north-west. Around the southern end, near Ellis lake and near the 

 State line, north of Mitchell's Mills, the quartzite beds have an east- 

 south-east dip and the angle is from 40 to 60°. The same direction 

 and like angles were observed on the eastern side of the mountain, 

 and at the west border of Kent Plains, in Connecticut. The bound- 

 ary between the gneisses and the quartzite at the south is near Ellis 

 lake, to the north-east of it — crossing the road, which runs north to 

 the Patchin-Kennedy neighborhood, one-eighth of a mile north of the 

 Dixon-IIaviland corner and intersecting the State line about one mile 

 north of Mitchell's Mills. The eastern boundary follows the border 

 of the Kent Plains. 



Tliere is a want of conformability between the quartzite and gneiss 

 when they are seen close to one another. And the prevailing dips of 

 the quartzite are away from the mountain — an anticlinal uplift 

 due to the elevation and folding of the gneiss. The position of the 

 strata of gneissic rocks in the East or Dover mountain, as shown by the 

 dips observed along the borders and on two cross sections, indicates 

 the possible existence of a closely folded anticlinal on the western part 

 of the range, combined, probably, with synclinals to the east of it. 

 The strata on the Avest slope have in general a steep dip to the cast- 

 south-east, with a few westerly dips ; whereas on the western part of 

 the top the angles of dip are from 45 to 80° and to the south-east. 

 The absence of observed dips on the east slope leave much doubt as to 

 the probable structure of this mountain range. 



The rocks composing the strata of the East (or Dover) mountain 

 range are gneiss, granite, granulyte, ((uartz-syenite, syenite-gneiss 

 and mica-schist chiefly ; and otlier crystalline rock varieties of much 

 less common occurrence and of very limited outcrop. The variation. 



