No. 104.] 175 



As thus described in detail, the line represents the boundary of 

 gneisses and quartzitic rocks across Beekman township ; in East Fish- 

 kill there are separate outcrops of the latter at the border of the gneisses, 

 near the Baptist church ; south of Stormville and near the Hopkins 

 place ; near the Shenandoah iron mine ; at Shenandoah Corners ; in the 

 Wickapee hollow ; in Fishkill Hook south of Johnsville, and near the 

 town line south-south-west of the same village. In Fishkill township 

 the border is drift and alluvial beds (in part), escepting the limestone 

 in the Clove valley and the limestone, quartzite and slaty rocks in 

 Matteawan, but the latter are isolated outcrops and separated from 

 gneiss of Fishkill mountain on the south by much drift. Hence, 

 the relative position of these sedimentary strata is not determined 

 by any contacts or any closely out-cropping beds in this town. 



The relation of the Poughquag-Fishkill quartzite to the under- 

 lying crystalline rocks of the Highlands is shown by several good sec- 

 tions, one of which has been referred to on page 173. Another and 

 more interesting locality is in the town of East Fishkill, nearly two 

 miles south-south-west of Johnsville, or three miles south of Brincker- 

 hofE station. The mountain road leading southerly and passing West 

 Hook district school and the Adams place, ascends, first, over the 

 quartzite and then up the projecting tongue of gneiss. On the east, 

 and west side of this gneiss the grey- white quartzite strata crop out, ■ 

 dipping on the west side 35° to the west-north-west and rising up in 

 a nearly vertical cliff 100 feet high above the gneissicbase or substratum. 

 The dip of the same rock, as seen on the east and north-east of the 

 gneiss, is 20"^ north and 35° east. And the rock is in some beds a fine | 

 slialy sandstone. Overlying the latter, near the foot of the hill, a \ 

 blue, magnesian limestone appears, having the same dip to north-west. | 

 Another interesting locality where the quartzite is in close proximity 

 to the underlying granitic rock is on the McCarthy place, one and a 

 half miles south of Johnsville. At this locality the rock is marked by 

 the presence of a scolithus, which suggests the horizon of Potsdam 

 sandstone. The beds dip north 55° east, 40° ; and are within 200 feet 

 to south of a granitic ledge. 



Perhaps the best section showing the quartzite reposing unconform- 

 ably upon the gneisses of the Highlands is south-east of the deep 

 Poughquag cut of the N. Y. & X. E. R. E., and one mile north-west 

 of the West Pawling E. R. station. In the deep cut the quartzite 

 beds dip easterly at angles from 15° to 20°. To the south-east 

 in the next (low) cut, the same rock has its strata dipping to the 

 north-west at an angle of 20°, and the gneiss within 300 feet of the 

 former, but lower on the slope dips at an almost vertical angle to the 

 south-east. The same rock forms the base of this Poughquag spur on 

 the north.* 



A narrow and isolated outcrop of granitic rock north of the Fish- 

 kill creek may be described in this place, since it belongs appar- 

 ently to the Highlands belt of crystalline rocks. It is traceable Irom 

 the large carpet mill and the creek at Groveville through G-lenham, 

 north of Fishkill village to Yly mountain where it disappears under 



* On the Poughquag- Fishkill quartzite, and its relations to the Archtean rocks, and 

 the overlying limestones, see articles by Prof. J. D. Dana in Am. Jour, of Science {S), 

 III, pp. 250-256; (3) XVII, pp. 385, 386, and (3) XXIX, pp. 209, 221. 



