474 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



In the Cabotian mountains, among the oldest on the globe, and 

 extending across the northern part of this continent, the traces 

 of ancient volcanos are found throughout. They occur especi- 

 ally upon the northeastern coast of Lake Superior, and upon the 

 Gulf of St. Lawrence. These mountains were formed in the 

 azoic age of the world. 



In the latter part of the azoic age, there was another system 

 of ancient volcanos in the neighborhood of Boston, the outflow 

 of which is still found in the shape of porphyry, green stone and 

 certain forms of granite. Coming up a step further into the 

 lower Silurian formtions, when shell-fish began to abound, we 

 have another system of volcanos in the north of New Hamp- 

 shire, Vermont, Canada, and occasionally in the Blue mountains 

 of Tennessee, and in the Blue Ridge of Virginia, leaving granite, 

 porphyry, and green stone to mark their positions. There was, 

 also, in the Silurian age, a very long system of eruptions on the 

 shore of Lake Superior, occurring usually in the form of three 

 parallel ridges, elevated six hundred feet above the immediate 

 neighborhood. lie Royale appears to have been elevated from 

 the bottom of Lake Superior at this time, coming up with 

 almost perpendicular sides. Still later, in the Carboniferous and 

 Devonian age of the world, there were volcanos among the 

 mountains of Nova Scotia and New Brunswick. In ihe Permian 

 age, which immediately succeeds the Carboniferous, we begin to 

 find the Triassic rocks, or red sandstones, of New Jersey and 

 the Connecticut river, and of North Carolina and Virginia. 

 When those rocks were deposited, and in the act of hardening, 

 trap, and greenstone, and basalt, and other igneous rocks, were 

 formed ; we have the traces of igneous action, beginning beneath 

 the bosom of the Atlantic, extending from the Vermont line 

 across the States of Massachusetts and Connecticut, and termi- 

 nating at New Haven, commencing again at the Palisades, and 

 extending across the States of New Jersey, Pennsylvania, Mary- 

 land, Virginia, North Carolinia, South Carolina, and terminating 

 in Georgia, usually in three great systems. We find igneous 

 rocks also in Missouri, indicating volcanic action there in the 

 same age. After this age there has been no volcanic action upon 

 the eastern slope of the United States. 



In the succeeding age, the Cretaceous, there were volcanos 

 lying east of the Bocky mountains, four isolated mountains lying 

 near the Canadian fork of the Arkansas river, others extending 



