150 ARCHAEAN TIME. 



The principal of the areas is The great northern, nucleal to the con- 

 tinent, B B C C on the map, lying mostly in British America, and hav- 

 ing the shape of the letter V, one arm reaching northeastward to 

 Labrador, and the other northwestward from Lake Superior to the 

 Arctic. The region appears to have been, for che most part, out of 

 water, ever since the Archaean era. To this area properly belong the 

 Adirondack area, covering the larger part of northern New York, and 

 a Michigan area south of Lake Superior, each of which was probably 

 an island in the continental sea before the Silurian age began. 



Besides this nucleal area, there are border-mountain lines of Ar- 

 chasan rocks : a long Appalachian line, including the Highland Ridge of 

 Dutchess County, N. Y., and New Jersey, and the Blue Ridge of Penn- 

 sylvania and Virginia ; a long Rocky Mountain series, embracing the 

 Wind River mountains, the Laramie range, and other summit ridges 

 of the Rocky Mountains. In addition, in the Eastern Border region, 

 there is an Atlantic Coast range, consisting of areas in Newfoundland, 

 Nova Scotia, and eastern New England ; in the Western Border region, 

 a Pacific Coast range in Mexico ; and several more or less isolated 

 areas in the Mississippi basin, west of the Mississippi, as in Missouri, 

 Arkansas, Texas, and the Black Hills of Dakota. 



The Adirondack area in Northern New York covers for the most part Essex, Clinton, 

 Franklin, St. Lawrence, Hamilton, and Warren counties, and parts of Saratoga, Fulton, 

 Herkimer, Lewis, and Jefferson counties. 



In the Eastern Border region, Archaean rocks occur in Nova Scotia (near Arisaig); 

 in New Brunswick (near Portland); probably in part of Maine, on the Island of Mount 

 Desert (according to Verrill) ; and along a range of country running northeastward to 

 New Brunswick ; in northeastern Massachusetts, about Newburyport, Chelmsford, and 

 Bolton ; and in northeastern Rhode Island. 



In central and western New England, there are areas in the White Mountain region, 

 New Hampshire (tirst announced by C. H. Hitchcock) as at Waterville; and west of 

 the Connecticut, about Winchester, Connecticut (Hall), and the emery region of Ches- 

 ter, Massachusetts, — the titanic iron vein of Winchester and the emery and iron vein 

 of Chester lying nearly in the same line. 



The Appalachian ureas commence in Dutchess County, New York, west of Connecti- 

 cut, and extend south/westward to West Point, and thence along the Highlands of New 

 Jersey, the Durham Hills of eastern Pennsylvania and their continuation in South 

 Mountain, and beyond in the Blue Ridge, through western Virginia and North Carolina, 

 into South Carolina, Tennessee, and Georgia. 



The map of New York and Canada, in the chapter on the Silurian, shows more pre- 

 cisely the form of the New York Archaean and that north of the St. Lawrence. It 

 represents also the Silurian and Devonian strata of the State, as they become succes- 

 sively the surface-rocks, on going from the Archaean southward. Adjoining the Archaean 

 (numbered 1), is the earliest Silurian. No. 2, which outcrops where it is represented, but 

 is supposed to underlie the strata numbered 3, 4, 5, etc. So No. 3 is the next formation 

 which outcrops, while it probably underlies all the beds 4. 5, etc. The Archaean is thus 

 the lowest ; and eacli successive stratum was a new deposit over it, in the seas that 

 bordered at the time the Archaean dry land. 



In the Rocky Mountain rer/ion., there are Ions; narrow ranges whose limits are not well 

 determined. On the Mexican area, see Am. Jour. Sci., II. xxxix. 309, 1865. 



