WITH THE PRIMARY SYSTEM. 
59 
worn down, leaving the range of knobs as we now find. Thus Bald mountain and Mount 
Toby, with several others in the neighborhood, stand in insulated high points, capped with 
the Calciferous sandstone; while at their bases the Taconic slate appears in an outcrop, 
varying in thickness from fifty to two hundred feet. But the Calciferous sandstone is not 
confined to the line in the immediate borders of the valley of the Hudson: it is found in 
patches twenty miles east, reposing as at the west upon the slates; probably, however, 
upon the magnesian slates. 
From these few remarks upon this rock, its position and relations will be understood. It 
is the lowest member of the New-York system, as well as the most easterly; and occupy¬ 
ing an exceedingly long range, it is not surprising that its lithological character should be 
found diverse and continually changing. 
I have now exhibited the actual relations of one of the Taconic rocks to the New-York 
system; that member which on all hands has been considered as the nearest related to the 
Hudson river shales and sandstones, or the one which approaches the nearest in litho¬ 
logical structure and condition to these rocks. 
Having demonstrated the relations of the most westerly mass, and having shown that it 
is not only unconformable to the New-York rocks, but inferior to them, I proceed to speak 
of the relations of the most easterly members of the Taconic with the Primary system, for 
the purpose of showing that the Taconic system is the newer of the two, or that it holds an 
intermediate position between the Primary schists and the New-York system. 
At several localities which I have often examined in Vermont and Massachusetts, the 
most easterly rock is the Brown sandstone, or Granular quartz. A fine exposure exists at 
Sunderland (Vermont), nearly east of Salem in Washington county (New-York); or 
rather of Miller’s falls, on the Hudson river. The quartz succeeds a magnesian slate, 
with which it is conformable; and on being traced to the primary schists, is found to 
repose upon them unconformably, the former ranging N. 20° E. and dipping at an angle 
not exceeding 10°, while the primary schists have a much steeper dip to the east. The 
precise line or plane of junction is concealed by drift, but I was able to observe it within 
a few yards. Near the junction, the slaty quartz is charged with crystals of schorl and 
octahedral iron. There are also beds of what may be termed porphyritic quartz , since they 
contain crystals of felspar. A portion of the lowest mass, however, is a breccia, as in many 
other important localities, of which I shall have occasion to speak hereafter. The quartz, 
as is frequently the case, is interlaminated with a siliceous slate, by which its stratification 
is very clearly shown, giving us the means of distinguishing the planes of deposition from 
the very strong natural joints and those of cleavage. 
8 * 
