24 Messrs. Foster and Whitney on the 
In the eastern portions of the United States, there can be no 
doubt of the existence of this system 
We are satisfied from ee observation that it flanks the 
Adirondack range in New York, where it is associated with hy- 
persthene rocks “and ay masses of sub-magnetic oxyd of iron, 
below the Potsdam sandstone. 
The Messieurs Rogers describe a series of obscurely stratified 
rocks in Pennsylvania and Virginia, occupying the same relative 
osition known as the gneissoid series. ‘They undoubtedly 
flank the Appalachian chain on the east, throughout their entire 
range, and vlc Sepmael be found well ‘developed in Tennessee 
and North Car 
In Europe thie existense of this series has been established 
beyond controversy. It has been shown by eminent geologists, 
— by Murchison and de Verneuil,* that the lowest beds 
n Scandinavia, containing the least traces of organic life, are 
edie exact equivalents of the Lower Silurian strata of the British 
Isles, and that these have been distinctly formed out of, and rest 
upon, slaty and other rocks which had undergone crystallization 
before their particles were ground up and cemented together 
again to compose the earliest beds in which organic life is trace- 
able. ‘To this most ancient system of rocks in Scandinavia, they 
have given the name of azoic. By this term, they do not mean 
dogmatically to assert that nothing organic could have been in 
existence during the earliest times, when those rocks were in the 
process of formation, but simply to express the great fact, that, as 
far as our present state of knowledge goes, we look in vain ‘for 
any traces of organic life, and it seems probable that they were 
formed under such physical conditions that nothing living could 
have flourished during that period. 
The great mass of rock in Scandinavia is made up of a crys- 
talline, granitic gneiss, presenting an almost infinite succession of 
feldspathic, quartzose, micaceous and hornblendic lamine, which 
are often highly contorted, though a general strike or direction 
may be traced over a large tract of country. These rocks are 
no means to be confounded with the metamorphic Silurian — 
occurring under a similar and analogous form in the 
country. These azoic rocks are often disturbed and cut chong 
by dykes of greenstone and traversed by ia ape veins of 
granite. 
So is evident from the direct comparison of the more ancient 
with newer metamorphic Silurian, that, from lithological 
shniaeints alone, no distinction could be drawn between them, 
and it is only where the most conclusive evidence is afforde 
y superposition of the latter unconformably upon the former, 
* Russia and the Ural Mountains, vol. i, p. 10. 
eae 
Tec RMON EERE SI 
