WAi-ooTT.] NEW HAMPSHIRE. 71 



section between the Huronian and tlte Helderberg period. On the map 

 facing page 536 the formations referred to the mica-schist period are 

 clearly outined. In a subsequent paper Prof. Hitchcock 1 presented a 

 table or scheme representing the stratigraphical column of New Hamp- 

 shire. The Cambrian includes at the summit the Rockingham schists, 

 and below, in order, the calciferous mica-schist, the Coos group, clay 

 slates, and Mount Mote conglomerate. The description of the various 

 formations is given on page 13 and on the map the geographic distribu- 

 tion is delineated. This paper appears to have been prepared and pub- 

 lished prior to the issue of the second volume of the Geology of New 

 Hampshire 2 and it does not refer to the volume. On page 674 of the 

 latter work the formations in New Hampshire are tabulated as follows: 



Feet. 



' Upper Helderberg (Vermont) 200; Lower Helderberg, 500 700 



Calciferous inica schist 4, 800 



„, . ! i Staurolite slate 3,000 



Coos group. <? Mica schist, often stauroliferous 3,300 



( Quartzite 1,000 



'^Cambrian slates (Connecticut Valley) 3,000 



Total Paleozoic 15,800 



f Kearsarge andalusite group , 1, 300 



I Rockingham mica-schist G, 000 



Paleozoic? ^ Merrimack group 4,300 



I Ferruginous slates, with steatite (probably repetition of preced- 

 l ing) 



Total Paleozoic ? 11, COO 



Under the head of Cambrian, in the Geology of Northern New 

 England, Prof. Hitchcock says : 3 



The discussions about the value of the Cambrian series are leading geologists to 

 assign to this place in the column a thick mass of sediment, usually without fossils 

 and largely argillaceous in character. We may for the present place here the follow- 

 ing groups: (1) Mica-schists of southern New Hampshire. (2) Merrimack group, 

 including argillo-quartzites in Coos County. (3) Coos group. (4) Clay slates. (5) 

 Mount Mote conglomerates. 



' In one of his later papers, Prof. Hitchcock, 4 in speaking of the various 

 formations that make up the mica-schist group, says they may be called 

 Silurian, Cambrian, or pre-Cambrian, according as each author is in- 

 clined to regard New England as very ancient or on the verge of the 

 Paleozoic. In a table giving the thickness of the formations 5 the 

 Cambrian slate series has a thickness of 4,000 feet; and beneath it 



1 Geological map of New Hampshire and Vermont, with notos on topography and geology. In Geol- 

 ogy of Northern New England, 1874, p. 9. 



2 Hitchcock, C. H. Geology of New Hampshire, Concord, 1877, vol. 2. 



3 Geological map of New Hampshire and Vermont, with notes on topography and geology. In Ge- 

 ology of Northern New England, 1874, p. 13. 



4 Geological sections across Vermont and New Hampshire. Am. Mus. Nat. Hist., Bull., vol. 1, 1884, 

 p. 168. 



6 0p.cit.,pp.l78,179. 



