HISTORY OF GEOLOGICAL SURVEY. I I 



that the White Mountain series were older than those in the Ammo- 

 noosuc and Connecticut valleys. In the year following, 1870, Dr. T. 

 Sterry Hunt published a letter suggesting whether he had not been at 

 fault heretofore in calling the White Mountain rocks Paleozoic. In 1871 

 he proposed to call them pre-Cambrian.* 



Dr. Jackson's section is wrong in such details as these. The granite 

 does not constitute the central axis of the White Mountains ; the strata 

 are not regular in their dips upon both sides of the axis, there being 

 overturns as well as repetitions of older formations. The Green Moun- 

 tains are not made up in the mass, nor in any part, of quartz rock in the 

 position indicated, and the term Cambrian is misapplied. 



Territorially, Dr. Jackson's oldest division is made to occupy the prin- 

 cipal part of the state. The most northern locality specified is at Berlin. 

 It occupies the greater portion of the breadth of the state in the latitude 

 of Bristol. South of this line there are only isolated granitic patches 

 west of the Merrimack river, while a broad band of it extends nearly as 

 far as Concord on the east side. 



The mica slate formation occupies most of the territory south of the 

 latitude of Franklin, passes up to Jackson on the east and to Columbia on 

 the west side of the first and fundamental group. There is also a little 

 represented as lying upon Mt. Washington. 



The third division — "hornblende rock" — is very limited, appearing 

 only in Hanover, Wakefield, and Acworth. The fourth — " clay slate " — 

 appears along Connecticut river, in Hinsdale, Chesterfield, Dalton, and 

 Lancaster ; on the east side of Mt. Washington ; along Salmon river, 

 in Rochester, Somersworth, Newington, Portsmouth, and also Rye. 



" Drift " is shown along the Merrimack river, in Hudson, Litchfield, 

 Pembroke, Northfield, Holderness, and Woodstock. It seems to include 

 some extensive sandy plains properly belonging to the next division. 

 "Alluvium" appears in the same valley in Concord, and New Hampton, 

 in the bend opposite Bristol village ; also on the Connecticut, in Hins- 

 dale, Westmoreland, Piermont, Haverhill, and Lancaster. The localities 

 of minerals and ores need not be enumerated. 



*Amer, Jour. Sci. II, Vol. L, p. 83, Presidential Address before American Association for the Advance- 

 ment of Science, at Indianapolis, 1871. 



