OCCLUSION OF IGNEOUS ROCK 437 



The same twin belt of acid and basic crystalline eruptives, 

 with their derivative schists, stretches from south to north along 

 our entire Atlantic seaboard, approximately parallel to the coast 

 but approaching tidewater only where it reaches Washington. 

 Upon the granites and gneisses of its eastern margin, where this 

 is crossed by the east-flowing rivers, a series of important cities 

 and state capitals find their location : in Alabama, Montgomery, 

 on the Alabama river ; in Georgia, Augusta, upon the Savannah ; 

 in South Carolina, Columbia, upon the Congaree ; in North 

 Carolina, Raleigh, upon the Neuse ; in Virginia, Richmond, 

 upon the James; in the District of Columbia, Washington, 

 upon the Potomac. 



Beyond that, directly upon the tract of eruptives, as else- 

 where explained, there follow : in Delaware, Wilmington, upon 

 Brandywine and Christiana creeks ; in Maryland, Baltimore, 

 upon the Patapsco ; in Pennsylvania, Philadelphia, upon the 

 Schuylkill ; in New Jersey, Jersey City and Hoboken, upon the 

 Hudson ; in New York, New York City and Peekskill, upon 

 the Hudson ; in Massachusetts, Boston, upon the Charles ; and 

 in Canada, Montreal, upon the St. Lawrence. Throughout 

 this great belt occur the same folding of beds and intense 

 alteration of old sedimentary deposits as on Manhattan Island, 

 and we find in all these sites of prominent American cities the 

 degraded stumps of vast mountain ranges of the same ancient 

 uplift. 



TJie Coastal CJiain of Volcanoes. — To the north of Washing- 

 ton, where this range stretched along the border of the inland 

 sea, it has left unmistakable evidence as to important charac- 

 teristics in structure and physiography not yet clearly set forth. 

 The facts stated concerning the abundant intrusions on and near 

 Manhattan Island mark this location as an ancient center of in- 

 tense igneous activity at a very early geological period. It was 

 probably contemporaneous with the one already recognized in 

 the Cortlandt series, near Peekskill, on the south side of the 

 Highlands of the Hudson. 



In his discussion of the distribution of ancient volcanic rocks, 

 as "■ disguised igneous masses in the oldest geological forma- 



