GEOLOGY. 313 



5. DC Vcrneuil rightly divides the New York groups into two great 

 classes, the " constant " and the " local." Among the former are Potsdam 

 Sandstone, Trenton Limestone, and Niagara. Among the latter are the 

 four lower Hulderbergs, and perhaps Oneida conglomerate, etc. This is a 

 useful division. 



6. That it is both convenient and natural to divide the Silurian and Devo- 

 nian systems of this state each into three stages, the division being based 

 on change of sediment and their fossil contents. 



7. The Middle Silurian stage is a period of especial transition from the 

 coarseness of some of its sediments, from their innumerable and minute 

 alterations, and from the organic poverty prevailing. 



8. That the presence of Oneida conglomerate in Xew York does not 

 necessitate a change of name for all the strata below it (of "Cambrian" 

 for instance), because a conglomerate does not always indicate systematic 

 change, not even if there be volcanic intercalation, provided there is 

 conformableness, and some community of fossils. 



The Oneida conglomerate seems to be local, is supernumerary, and only 

 found at present on the east of middle North America. 



9. The hardening and crystallizing effect of metamorphism is seen only 

 in the neighborhood of hypogcne rocks. 



10. The Xew York basin exhibits few uplifts, and those of limited magni- 

 tude; no uplifts dividing it into a scries of deep basins contained in hypogene 

 beds, as in Bohemia, Wales, etc. Neither has it sheets of alternating vol- 

 canic grit (conformable), save in the Potsdam rock on Lake Superior. 



This basin has a "lay,"' or position of its own, as a number of undulating 

 sheets of sediment, dipping slightly to the southwest, here and there pierced 

 by a peak of crystalline rock, and in certain regions raised into three broad, 

 low domes, of great length. 



11. The sedimentary rocks of this basin have submitted to two kinds of 

 plutonic disturbance, independent of each other, and acting at distant inter- 

 vals: 1st, that of secular or slow oscillation during deposition; 2nd, that of 

 disturbance arising from paroxysmal uplifts long after their completion. 



12. The whole Silurian and Devonian series of strata having, during 

 deposition, sunk to the depth of 13,300 feet, it is submitted as a query 

 whether it does not seem necessary to suppose that they were elevated into 

 their present position by the post-carboniferous uplift, such agency being 

 sufficient to produce all the observed phenomena, and the effects diminishing 

 westwards from the central line of disturbance. No other agency is known 

 to me, although hinted at by [some] American geologists. 



13. It is a remarkable fact that brine-springs exist in considerable quantity 

 in the middle stage of the Silurian system, a group or two below the Oiion- 

 daga salt-springs of the upper stage, and three palaeozoic systems belcw any 

 salt deposits in Europe. 



14. That the form and direction of the five great Canadian lakes are not 

 due originally and mainly to the passage of loaded waters over their site, 

 but that they follow the outcrops of their containing sedimentary rocks; 

 changes in shape and size having, nevertheless, occurred since. 



151 The contours of the valley of the St. Lawrence generally (to which 

 much of New York belongs), and its increasing elevation south-westwards, 

 inland from Montreal, are due to the successive altitudes assumed west- 

 ward, in slopes and plateux, by the Silurian and Devonian strata the lowest 



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