Igneous Ejections, Volcanoes. 118 
the fissures and trap-ejections of the Atlantic slope from Nova 
Scotia to North Carolina was extremely slow, and probably 
nowhere exceeded 5000 feet; and it caused in the end only 
Further, over the Pacific slope of the Rocky Mountains, the 
vast ejections in the Tertiary era appear to have had, as I hav 
said, a natural source in an undercrust fire-sea, and the same 
t was essential to all the previous oscillations of the crust; and 
which, therefore, like that beneath the eastern border of the 
“eae must have been continued on from the period of general 
urdity. 
Moreover, these Pacific-border eruptions took place in con- 
incapable, it would seem, of generating the heat required for so 
vast an amount of subterranean fusion as the ejections indicate. 
Again, both on the Atlantic and Pacific borders of North 
America, wherever the plications have been greatest, and the 
conditions, therefore, favorable for producing the largest amount 
of heat, there we find evidences of the profoundest meta- 
morphism, and of the least amount of fissure eruptions ; and, 
conversely, the regions of gentler plications and feebler meta- 
are an example of the former; and the Triassico-Jurassic areas 
on the Atlantic border, or the Tertiary and Quaternary outflows 
on the Pacific slope, of the latter. The reverse should be true 
certainly requires a much higher temperature than metamor- 
phism. The evidence appears to be decisive against the mak- 
* This volume, page 7, and beyond. 
Am. Jour, aise: Series, Vor, VI, No. 32.—Aveust, 1878, 
