72 THE CAMBRIAN. Ibull.81. 



we find the Crystalline group that was referred to the Cambrian in the 

 Geology of Northern New England in 1874, as follows: 



Crystalline group. 



Feet. 



Calciferous mica-schist and Coos group 12,000 



Kearsarge group 1, 300 



Rockiugham mica-schist 6,000 



Merrimack group 4, 300 



Beneath the Merrimack group the Huronian is placed, with a thick- 

 ness of 12,000 feet. 



In a tabulation of the geological formations of Maine, New Hamp- 

 shire, Vermont, Massachusetts, Rhode Island, and Connecticut, by 

 Prof. Hitchcock, 1 the calciferous mica-schist, staurolite slate and schists, 

 quartzite, andalusite schists, and Rockingham mica-schists are in- 

 cluded in the Cambrian. In a foot-note he says that the quartzite, 

 staurolite slate and schist, and the calciferous mica-schists may yet 

 prove to be Silurian. In his classification of the Paleozoic rocks of 

 New England he places under Cambrian the St. John or Braintree slate, 

 Taconic slate, and Roxbury conglomerate. 



In a table published in 1890 he includes only the Potsdam, Georgia, 

 Acadian, and the Taconic slate (in part) in the Cambriau. All of the 

 foliated crystalline rocks of New England are classified as pre-Cam- 

 briau. 2 



EASTERN MASSACHUSETTS. 



The references to the argillite and limestone in which the Cambrian 

 faunas have been found, in the Boston and Narragausett Basins, occur 

 in most of the publications relating to the geology of eastern Massa- 

 chusetts. In 1818 Messrs. J. F. and S. L. Dana stated that the argil- 

 lite was the oldest rock known in the region. 3 Its distribution is shown 

 in a general way upon the map accompanying the report. It is stated 

 to be subjacent to the syenite in Milton and Braintree, and to be 

 stratified. In the works of Prof. Amos Eaton 4 the rocks of eastern 

 Massachusetts are shown in sections, but nothing is added to the data 

 given by the Messrs. Dana. 



The next description of the geology of Boston and vicinity, by Dr. 

 ,1. W. Webster, 5 mentions that the light gray clay slate is the only rock 

 found on the Boston Peninsula in situ. He noticed the presence of the 

 slate in Quincy and also at Nahaut. 



1 Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut. (Geological for- 

 mations.) Macfatlane'8 Am. Geol. R. R. Guide, 1879, p. 56. 



2 Idem., second edition, 1890, p. 86. 



3 0mlines of the mineralogy and geology of Boston and its vicinity, with a geological map. Am. 

 Acad. Arts and Sciences, Memoirs, vol. 4, 1818, pp. 129-223. 



4 An Index to the Geology of the Northern States, with a transverse section from Catskill Mountain 

 to the Atlantic. Leicester, 1818, pp. 52. A Geological and Agricultural Survey of the District Ad- 

 joining the Erie Canal, Albany, 1824, pp. 163, plate. 



6 Remarks on the geology of Boston and its vicinity. Boston Jonr. Phil, and Arts, vol. 2, 1824, pp. 

 277-292. 



