254 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



10. 1877. C. H. Hitclicock. Note upon the Conuecticut Valley Helderberg. Ibid., 

 Vol. XIII, p. ;U3. 



17. 1877. C. II. Hitchcock. The Geology of New Hampshire. Vol. II, p. 428, with 



map and sections. 



18. 1877. J. D. Dana. Note on the Helderberg formation of Bernardston, Massa- 



chusetts, and Vernon, Vermont. Am. Jour. Sci., 3d series, Vol. XIV, p. 379. 

 li), 1883. R. P. Whitfield. Observations on the fossils of the metamorphic rocks of 



Bernardston, Massachusetts. Ibid., Vol. XXV, p. 368. 

 20. 1890. Ben K. Emerson, A description of the Bernardston series of metamorphic 



Upper Devonian rocks. Ibid., Vol. XL, pp. 263, 362. 



HISTORY. 



1819. "Ar<iillite sometimes alternating with mica-slate, sliiceous slate," 

 "undoubtedly primitive." Almost perpendicular, inclining a few degrees 

 to the west. (1,' j). 10.'').) The hornblende-schist of this series is associated 

 with the Triassic "greenstone." (1, p. 109.) 



1823. Extends from Leyden, north to Rockingham, Vermont; occurs 

 again at Woodbridge, Connecticut; often tortuous and slightly undulating, 

 especially when passing- by imperceptible changes into mica-slate. It 

 embraces numerous beds and "tuberculous masses" of white quartz. 

 It also alternates with mica-slate, and a pecitliar coarse limestone forms 

 beds in the argillite. The map separates the argillite from the mica-slate 

 on the west by a continuous band of limestone and extends it eastwardly to 

 include all the mica-schists which have been associated with the Bernards- 

 ton limestone in later time, while the mica-schists on the eastern side of 

 the river are associated with the mica-slate west of the argillite. (2, p. 36.) 



The hornblende rock is sei)arated as primitive greenstone in the noith 

 of Gill and south of West Northfield. (2, p. 31.) 



1S32. The limestone and magnetite beds which had been worked forty 

 or fifty years before, but had produced poor iron, are described briefly in 

 their economic aspect but without geological data. (4, p. 27.) It was 

 supposed to form a bed in the argillite. Compares it in value with a gold 

 or silver mine. 



1833. Fossils discovered in the limestone and figured (6, atlas, pi. 14, 

 p. 47); and the limestone, though not seen hi contact, supposed to lie uncou- 

 formably upon the argillite. The quartz rock lying above the limestone, 



' The numbers 1, 2, 3, etc., refer to the numbers above under the head of Literature. 



