62 



ORDER OF SUCCESSION 



from iliis difticulty, we may suppose tlie masses to have succeeded each other as in the 

 annexed diagram, and tlio laconic slate, with its subordinate beds, to have been deposited 

 during a slow upward movement of the primary schists and older laconic 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. 



rig. 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 arc newer rocks than the 

 Magnesian slate and Stockbridge limestone : they contain fossils, which are wanting 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 ol)literation 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 tlie rocks in question never contained fossils. The Grey sandstone, the 

 oldest member, so far as metamorphism is concerned, may as well retain and exhibit casts 

 or marks of organic bodies, as the equally hard siliceous rock, the Potsdam sandstone, at 

 the base of the New-York system. To assist us in maintaining these views, we 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, we 

 have reason for assuming the ground that the deposition was but scantily extended east and 

 west, and that the whole system was formed in a deep trough. 



If now we suppose these beds subjected to upheaving forces which we know have existed 

 in 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 were broken, or their continuity de- 

 stroyed, aiul their fractured surfaces raised to an inclination more or less steep according to 

 the amount and duration of the force applied. 



Those who wish to pursue the subject of physical change in the belt of country through 

 which the taconic rocks pass, will do well to study the article upon this subject by Profs. 

 W. H. and H. D. Rogeiis, in the Transactions of the Association of Geologists and Jfatu- 



