THE WILBEAHAM AND MONSON STNOLINES. 249 



no boundary could be drawn below to separate it t'roin the Monson g'neiss 

 proper. 



The hornblende-schist (Chester amphibolite) is a jet-black rock, satiny 

 on the surface from the effect of the great number of fine needles of horn- 

 blende which make iip nearly its whole mass. The whetstone-schist (the 

 equivalent of the Savoy schist) is a gray, granular, friable quartzite, vary- 

 ing from thin-iissile to massive, often a shining muscovite-quartzite, or 

 abounding in distant flakes of chlorite. It is covered on the western flank 

 of the syncline until the range crosses into Connecticut, when it appears on 

 the west flank of Perkins IMountain. 



The Conway mica-schist is a coarse, light-gray muscovite-schist, gen- 

 erally barren, but caiTying- at times a few garnets. Along its western base 

 it is much crumpled and silicilied, as if from the influence of the fault. 



On passing into Connecticut the regularity of the syncline is interrupted. 

 The amphibolite band which forms the ridge of Pine Mountain, Rattlesnake 

 Hill, and Perkins Mountain, in Soiriers, is suddenly cut ofl" in the south 

 shoulder of Perkins Mountain by the gneiss. The latter rock, which uj) to 

 this point has dipped a little north of west, here swings around shar[)h-, dip- 

 ping steeply north and northeast, so as to cut off the whole series uj) to the 

 mica-schist, and, reversing its direction, it runs south again, dipping normally 

 beneath the Conway schist, of course with a fault boundary. 



THE MONSON SYXCIilNE. 



The west Monson syncline is a perfectly symmetrical closed fold of the 

 scliistose series in the gneiss, and its character will be understood by com- 

 paring the detailed section below with the cross-sections on PI. XXXII. The 

 section given below commences with the older rock — the Monson gneis.s — 

 on the east, at a point 1,830 feet east of the sharp turn in the road at the 

 house of A. Bliss, jr., a mile northwest of Peaked Mountain, and runs west : 



a.' Mouson gneiss. 



b. Eowe schist. Gneissoid quartzite, with very little feldspar, muscovite, aud a 

 green mica or chlorite, with beds of gray biotite-quartzite, chloriteschist, aud horn 

 blende-schist appearing a little farther north, opposite the house of J. Burley ; 361 feet. 



d. Chester amphibolite. Epidotic qnartz-hornblende-schist, thin-bedded above 

 and changing into chlorite-schist; 459 feet. 



e. Savoy schist. Chloritic mica-schist, with subordinate beds of muscovite- 

 gneiss, changing above into arenaceous mica-schist (whetstone-schist) and still higher 



' These italic letters refer to sections described on pages 213-214. 



