126 



Worcester is on or near the line of strike of the Chelmsford 

 and Bolton gneiss ; and I have been informed by Mr. Benj. E. 

 Brewster that a large boulder of steatitic gneiss, apparently not 

 far travelled, occurs in Milford. The steatite in Groton is 

 well known. It occurs as a bed ten or twelve feet thick, 

 enclosed in mica slate, which is lithologically and stratigraphi- 

 cally identical with the mica slate that, farther south-east, is 

 so intimately associated with the gneiss in question. It will 

 have been observed, also, that talc is included in the list of 

 minerals occurring in these so-called Laurentian limestones ; 

 and this mineral is abundant in the Montalban limestone of 

 Smithfield, R.I. 



West of the Connecticut we find the belt of so-called talcoid 

 slate lying between this river and the Hoosac Mountains, and 

 stretching from Vermont southerly nearly across the State, pre- 

 senting decided Huronian characters ; yet, on the other hand, 

 there are good reasons for believing that it is Montalban. This 

 belt appears in fact to combine the characters of both the Huro- 

 nian and Montalban ; resembling the former in consisting largely 

 of hydro-micaceous and chloritic slates enclosing beds of serpen- 

 tine and talc, and containing chromic iron and emery ; and yet in- 

 cluding extensive beds of hornblende slate and stratified horn- 

 blende rock which hold garnet and other minerals, and appear 

 to represent the basic silicates of the Montalban series. The sec- 

 tion from Greenfield to Williamstown, which appears in the 

 report of Prof. Hitchcock on the geology of Vermont, shows 

 that this belt probably marks the axis of a synclinal ; for these 

 hydro-micaceous rocks usually exhibit, on the line of this sec- 

 tion, and elsewhere, approximately vertical dips, while the mica 

 slate and gneiss on either side dip toward the belt in question, 

 appearing to pass under it. Prof. Hitchcock evidently regarded 

 the talcoid slate as newer than the mica slate, as his section 

 shows, and yet as essentially a part of it ; for he says, in his 

 " Final Report on the Geology of Massachusetts " (p. 597) : 

 " Near the central part of the Hoosac Mountain range of mica 

 slate occurs a range of talcose (talcoid) and chlorite slates, in 



