62 
ORDER OF SUCCESSION 
from this difficulty, we may suppose the masses to have succeeded each other as in the 
annexed diagram, and the taconic slate, with its subordinate beds, to have been deposited 
during a slow upward movement of the primary schists and older taconic rocks, which of 
course would change the bed of the ocean in which these deposits were going on or accu¬ 
mulating ; or, we may suppose that early denudations have removed extensive portions of 
the upper beds. 
Fig. 6. 
A. Gneiss. 1. Granular quartz, or Brown sandstone. 2. Stockbridge limestone. 3. Magnesian slate. 4. Sparry 
limestone. 5. Roofing slate. 6. Coarse brecciated bed. 7. Taconic slate. 8. Black slate. 
As far as I am informed, there is no objection to the view here presented of these rocks, 
namely, that of regarding them to have been originally in this position ; the oldest mem¬ 
ber, the brown sandstone, reposing upon the primary rocks A, and each mass to have 
succeeded as in the diagram, and terminating with a black slate (No. 8), which may 
never have extended far east. I present this view as probable, and have been led to adopt 
it from the consideration that the Taconic and Black slates are newer rocks than the 
Magnesian slate and Stockbridge limestone : they contain fossils, which are Avanting in 
the other members of the series ; and though it may be urged that these rocks are so far 
changed by a variety of causes as to have produced the obliteration of their fossils if any 
ever existed in them, still when we recollect that fossils are found in many crystalline 
rocks, and that many layers of considerable thickness are but little changed, I am disposed 
to assume that the rocks in question never contained fossils. The Grey sandstone, the 
oldest member, so far as metamorphism is concerned, may as Avell retain and exhibit casts 
or marks of organic bodies, as the equally hard siliceous rock, the Potsdam sandstone, at 
the base of the NeAV-York system. To assist us in maintaining these vieAvs, Ave may 
suppose the superior members to have been removed by abrasion, and thus limited in an 
easterly direction; and besides this, as the Taconic system is comparatively narrow, Ave 
have reason for assuming the ground that the deposition Avas but scantily extended east and 
west, and that the Avhole system Avas formed in a deep trough. 
If now Ave suppose these beds subjected to upheaving forces which Ave knoAv have existed 
m all geological periods, they may be forced into an inclined position, and this position 
may be that general inclination which at present prevails. This position may have been 
produced by successive uplifts, by which the strata Avere broken, or their continuity de¬ 
stroyed, and their fractured surfaces raised to an inclination more or less steep according to 
the amount and duration of the force applied. 
Those avIio wish to pursue the subject of physical change in the belt of country through 
which the taconic rocks pass, Avill do well to study the article upon this subject by Profs. 
W. H. and H. D. Rogers, in the Transactions of the Association of Geologists and JYatu- 
