in the Geological History of North America, 341 



must cause the bulging 'of others, If any large areas of the 

 crust were sinking more than the rest, this very subsidence would 

 necessarily push up the borders of these areas into angular ele- 

 vations or folds ; and it follows necessarily, — the larger these 

 areas the higher the border elevations. 



These are the simple principles. The oceanic basins are these 

 areas of greatest subsidence ; and hence would necessarily flow 

 the law, already established as a matter of fact — the larger the 

 ocean, the higher the mountains on its borders, the deeper the 

 fractures and displacements there, and the vaster the outflow of 

 internal heat and lavas. The size, therefore, of the oceans, that 

 is, their extent and depth, is relatively a measure of the force 

 exerted on their sides. 



The wrinkles or elevations on the globe seem large when man 

 measures them by comparison with his own stature. But a sec- 

 tion of the land, true to nature, corrects this misapprehension. 

 In a section of the North American continent, drawn to a scale 

 twelve feet long, one-ninth of an inch will stand for an altitude of 

 10,000 feet ; one-sixteenth of an inch for the White Mountains, 

 and about three-tenths for the Himalayas. 



After this review of principles, let us now turn our attention 

 to North America and seek out its plan of development. 



I. The triangular form of the continent has been noted and its 

 simple ocean boundary : and it should be observed that the con- 

 tinent is set quite to the west of South America, so as to possess 

 this simplicity of boundary and therefore of moulding forces in 

 its highest perfection.* The small Atlantic on one side, and the 

 great Pacific on the other, indicate approximately the relative 

 amounts of force from the two directions, the southeast and south- 

 west, during the progressive ages of the history; — that to the 

 eastward the power was comparatively moderate, gently folding 

 up the Appalachians, and to the westward it was strong and 

 mighty, even to the raising of the Eocky range and opening the 

 great volcanoes of Oregon. We thus learn, with a degree of 

 precision not to have been anticipated, the direction and effi- 

 ciency of the great organizing forces. 



Glance now at American geological history from this point of 

 view, and consider where was the first germinant spot of the 

 growing continent, and what was thence onward the course of 

 development under the influence of this agency. 

 >^The earliest spot or primal area will be that of the Azoic rocks, 

 the first in the geological series. Such an area (see Chart, AAA) 

 extends from Northern New York and Canada, north-west to 

 the Arctic Ocean, lying between the line of small lakes (Slave, 

 Winnipeg, &c.) and Hudson Bay. East and west, it dips under 



* The contrast with Europe in this respect is striking, and accounts, as I have 

 said, (Address, 4c, p. 311,) for the greater simplicity of North American Geology, 



