127 



conformable order, and passing insensibly into the mica slate." 

 These mica slates, especially on the east, are unquestionably 

 Montalban, and are so regarded by Dr. Hunt ; ^ and it is probable 

 that the gneiss succeeding the mica slate on the west and forming 

 the Hoosac Mountains, although apparently referred by Dr. Hunt 

 to the Huronian system,^ really belongs in this newer formation. 

 This gneiss is indistinguishable from that composing a large 

 part of the Montalban series in Massachusetts, and appears, 

 as is the habit of the gneisses in this part of New England 

 generally, to underlie conformably the mica slates. It is 

 true it holds beds of serpentine and talc, — minerals which 

 are usually regarded as characteristic of Huronian strata ; 

 yet a glance at the geological map of this State suffices to 

 assure us that neither of these mineral species can be regarded 

 as foreign to the Montalban series. In no respect germane to 

 this question does the Hoosac gneiss resemble the undoubted 

 Huronian rocks of eastern Massachusetts, and in its petro- 

 logical relations it exhibits not a tithe of the disturbance 

 characterizing these truly ancient deposits. In short, I regard 

 as probable the view that the Hoosac gneiss passes under the 

 hydro-micaceous slate and enclosing mica slate to the eastward, 

 reaches the surface in an anticlinal axis at Shelburne Falls on 

 the Deerfield River, dips beneath the crystalline schists and 

 Mesozoic sandstones of the Connecticut Valley, and, save where 

 broken by faults, is stratigraphically continuous with the 

 gneisses east of the Connecticut ; and, since on either side of 

 the Connecticut the rocks lie for the most part in parallel north- 

 south bands, continuous with similar bands in New Hampshire 

 and Vermont, I am obliged to consider the Green Mountain 

 gneiss as also probably Montalban ; whence it follows, with a 

 like degree of probability, that the Green Mountains themselves 

 are of the same age as the White Mountains. 



In Rhode Island we find another set of doubtful beds. These 

 occupy an irregular area in the towns of Cumberland, Smith- 



1 Chemical and Geological Essays, p. 248. 



2 Ibid. 



