204 . GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



where the boundary can be studied. At the base of the argillite one finds 

 minute spangles of mica; a few feet below comes limestone, and then the 

 rock quickly grows coarser, mica-spangled, and garnetiferous. This is well 

 seen toward the south end of the boundary line, in the southeast corner of 

 Coleraine, near the house of D. Nelson. 



In the Whately area the transition is almost exactly the same, but a 

 heavj" band of white quartz marks for a long distance the exact boundary, 

 and there is probably a fault there. I have found nothing along this bound- 

 ary which would suggest the existence of unconformity between the two 

 beds. 



ARGILLITE IN THE WESTERN BORDER OF THE "GRAPHITIC MICA-SCHIST" 



(goshen schist). 



An inspection of the map of the Vermont survey of 1861 shows a broad 

 band of argillite, bordered on the west by Devonian limestone, extending 

 south from Lake Memphremagog, and thinning south and disappearing 

 midway the State. 



Along the west border of the Goshen schists, where they enter Massa- 

 chusetts, in Heath, is a band of thin, black slate that looks exactly like the 

 metamorphosed Carboniferous slate from Worcester, and which seems to be 

 the continuation of the Memphremagog slate. Farther south it is indistin- 

 guishable from the ordinary Goshen schists, except across Worthington, 

 where a band, 50 rods wide at the base of the schists, is a fine-grained, 

 barren, flat-fissile schist, unlike the garnetiferous schist above and the horn- 

 blende-schist below. These beds are described in some detail in following 

 down the western border of the Goshen schist (see page 179). I have 

 treated them as the base of the Goshen schists, and think tliis the most 

 probable view. There is no satisfactory reason for identifying the two 

 argillites. The western seems inconstant, and does not appear in the Goshen 

 anticline. 



relative age of THE CONWAY SCHIST AND THE LEYDEN ARGILLITE. 



An examination of the comparative sections on page 258 will show 

 that the first discrepancy of importance there indicated is in regard to the 

 relative positions of these two series, the argillite being regarded as the 

 lower and assigned to the Huronian b)^ Professor Hitchcock. 



