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Page:Popular Science Monthly Volume 19.djvu/244

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THE POPULAR SCIENCE MONTHLY.

stages of the continent's enlargement, and follow with the eye the stupendous changes which shaped it.

The first chart presents in its colored parts the primeval territory, which geologists regard as the first-made land of our continent, the archaic regions, around whose rocky framework were gathered the accretions of succeeding ages. It is the azoic terrain, that composite foundation of gneiss, granite, schists, crystalline limestones, sandstones, serpentine, and iron-ore masses, which defined the geological architecture of America. In its isolated ridges, cleared of the later and adjacent strata, we have before our eyes the principal portions of a continent upon which the ancient oceans played

". . . their priest-like task
"Of pure ablution round earth's lifeless shores."

Its sterile stretches unalleviated by a mantle of waving woods, unanimated by moving figures, reflected the harsh sunshine from rugged terraces or monotonous lowlands, a cheerless waste bathed by preadamite seas.

Starting from a point near Montgomery, in Alabama, the archæan country stretches northeasterly along the Appalachian axis and, rapidly widening, incloses large districts in Georgia, western South and North Carolina, of which latter State it defines the western boundary, and reaches eastward nearly to Raleigh. Passing on both sides of a lenticular area lying in North Carolina and Virginia, it narrows to a strip west of Richmond, where it is deeply bitten by a round gulf, and pressed to the seaboard, forms a thin isthmus west of Washington, then expands at Baltimore, and, lobed out into a pennant-shaped appendage, reaches down toward Newcastle, Delaware. From a little west of Burlington, nearly to Easton, a white patch shows an area where the archæan rock is no longer seen, but at the latter point a thin strip follows the Appalachian uplift and, including the highlands of West Point, appears as an attenuated finger or arm of a great area, which pushes south as far as Manhattan Island, whose gneissoid rocks compose it, and eastward over the western half of Connecticut. In Massachusetts the archæan rocks bifurcate; a finger reaches to the northern boundary of the State, where a thin connection exists with the great eastern region, and a shrunken area extends northward through the Berkshire Hills. The western limit of this latter strip lies some ten or fifteen miles from the eastern boundary of New York, and, entering Vermont at its southeastern border, widens out till, at Montpelier, almost half the State is covered. Slowly broadening thence, we follow its outlines into Canada, approach the St. Lawrence, and then, with an abrupt eastward deflection, trace it in a sinuous tongue until it touches the river at Mount Camille. The large eastern seaboard area of archæan rocks commences at Saybrook, on Long Island Sound, whence northward, limited by a sweeping curve, it covers the eastern part of