232 THE POPULAR SCIEXCE MONTHLY. 



stages of the continent's enlargement, and follow with the eye the 

 stupendous changes which shaped it. 



The lirst 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 ac- 

 cretions 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 archi- 

 tecture 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 iinalleviated by a mantle of waving woods, unani- 

 raated by moving figures, reflected the harsh sunshine from rugged 

 terraces or monotonous lowlands, a cheerless waste bathed by pre- 

 adamite seas. 



Starting from a point near Montgomery, in Alabama, the arch^ean 

 country stretches northeasterly along the Appalachian axis and, rap- 

 idly 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 w^est of 

 Burlington, nearly to Easton, a white patch shows an area where the 

 archean 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 com- 

 pose it, and eastward over the western half of Connecticut. In Mas- 

 sachusetts the archaean rocks bifurcate ; a finger reaches to the northern 

 boundary of the State, where a thin connection exists w4th 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, Avidens out till, at Montpelier, al- 

 most half the State is covered. Slowly broadening thence, we follaw 

 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 ar- 

 chaean rocks commences at Saybrook, on Long Island Sound, whence 

 northward, limited by a sweeping curve, it covers the eastern part of 



