378 
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BULLETIN OF THE NATURAL HISTORY SOCIETY. 
silicates are hydrated, impure graphite ■ beds are changed to a black 
amorphous crumbling shale, and a depression or narrow valley is usu- 
ally found at the contact of the two terranes. These conditions 
appear to indicate that the pre-Cambrian complex had long been above 
the sea-level in these districts when the first Cambrian effusives were 
thrown out upon it. 
Another point worthy of note in this connection is the large 
amount of feldspathic material in the Etcheminian beds ; the very 
sands are often composed of feldspathic grains, and these largely of 
unkaolenized feldspar, as though they had not been exposed to sub- 
aerial decay. Feldspar in this condition is found in two kinds of 
deposits, those that are the result of glacial wear and those found 
around volcanic vents, where particles of rock have been torn from 
the walls and blown out upon the surface of the earth. These if 
dropped into the sea would soon be covered up by fine mud and pre- 
served in their original crystalline condition. The Etcheminian 
appears to represent the submarine condition of these effusive rocks. 
On the other hand the Coldbrook series, as has been intimated 
above, represents the preceding sub-aerial phase of the eruptives. 
It is true that we find in many places conglomerates at the contact 
of these two series of rocks, so diverse in appearance; but elsewhere 
there are no beds of rolled fragments at the contact, and the passage 
is direct from ash-beds or diabases, to the slates and sandstones. 
In reports of the Canadian Geological Survey of 1870-71, pp. 
57-59, etc , both these groups of rocks have been included in the 
Huronian System. They may be equivalent in age to the upper part 
of that series, but unfortunately the absence of fossils in the original 
Huronian leaves this matter in doubt. 
As we contemplate the physical conditions of the initial epochs of 
Cambrian time in the Maritime Provinces, we seem to see a region 
long elevated above the sea, now subjected to depression nearly to the 
sea level, the depression being accompanied with extrusion of lavas 
and volcanic mud and the ejection of stones and ashes. These at first 
were cast upon a land surface, but, as the crust of the earth continued 
to sink, into sounds and bays of a shallow sea, diversified with pre- 
Cambrian ridges and islands, of greater or less extent. 
For the above reasons as well as because the stratified rocks of 
the underlying complex are markedly unconformable to the Cam- 
