SECTION ACROSS THE FORMATIONS OF NEW-YORK, EXTENDING TO THE COAL FORMATION OF PENNSYLVANIA. 1. Potsdam sandstone. 2. Calciferous sandrock. EXPLANATION OF THE SECTION. A. Primary or Hypogene rocks, consisting of granite, gneiss, mica slate, &c. 10. Onondaga Salt Group. 11. Helderberg limestones, including grits and sandstones. 12 Hamilton Group, including Marcellus shale and Tully limestone. 13. Portage Group, including Genesee slate. 14. Chemung Group. 15. Old Red Sandstone. 16. Conglomerate of the coal formation. 17. Coal formation of Pennsylvania. cements, sandstone for glass, building and flagging, granites of various characters, and the white and variegated marbles. Every portion of country where good materials for construction can be found, is indicated; and the nature of the rock can be as well ascertained by this map and description, as by going to the spot and examining the same. If any public improvement is suggested, the facilities and resources can be calculated; the contractor upon any proposed canal need not be at a loss for the localities of stone for his locks, for he can perceive at once in what regions he is likely to meet with suitable materials. The sections appended to the map show the relative position of all these rocks of New-York, to the great coal-bearing series of the United States; and prove conclusively that that mineral can never be successfully sought in this State. This map should be in the possession of every individual who desires to possess such information, and it should be placed in every school-house throughout the State. In order that my readers may obtain a more correct idea of what has been said in relation to the position of the rocks of New-York, the accompanying illustration is introduced, showing the position of the rocks, as would be seen in passing from the northeast to the southwest part of the State. This shows that those rocks forming the high mountains and being of the greatest altitude, are, in fact, geologically the lowest rocks, and pass beneath all the others, as may be seen in numerous places, and in none, perhaps, better than at Little Falls, on the Mohawk. Resting upon these older rocks, we perceive subsequentlyformed strata rising up, one overlying another, in the manner before described; but with their edges, for the most part, worn down to a uniform slope. We follow the order of succession entirely across the State; and soon after entering Pennsylvania, we observe resting above all the rocks which we have passed over, the true coal formation. Here we perceive the relations of this important group of rocks to the whole series of strata in New-York; and when we are once satisfied on this point, there is no difficulty in making an application of the same principles elsewhere, and deciding whether we are or are not in the vicinity of coal-bearing rocks: In the present instance, the conclusion has been arrived at by long and persevering trials, in comparing, inch by inch almost, the successive strata, in searching for their immbedded organic remains, and in observing every circumstance, even the most minute, which might subserve future investigations. Similar results have been attained over large parts of the eastern continent, and the discoveries here correspond with those-corroborating, if need be, the opinions of the relative age and position of our rocks. Aside from all matters of economical interest, the survey of NewYork has done much for the advancement of science. The sequence of the rocky strata between those of primary origin and the great coalmeasures may be regarded as settled forever; and at the commencement of this survey the order of these strata had never been definitely known in this country, nor indeed in many parts of Europe. The luminous work of Mr. Murchison, on the British Silurian strata, shows a series of rocks below the coal, similar to those which exist in New-York, but wanting in that completeness and absence of disturbance which characterize ours. Long as Geology had been studied in England, this work was the first in which these strata had been reduced to anything like order, or a clear distinction drawn between the carboniferous rocks and those of older date. Looking as we have done to Europe as our guide in science, all previous investigations were directed to the identification of our strata with those described in Great Britain; and since the description of the Carboniferous strata of that country corresponded more nearly than any others to the condition of the rocks of New-York, and since there was nothing like this extensive series supposed to exist below those of that period, it was natural to infer that ours were of the same age. The existence of such a belief, however unfounded, has prevailed, and has been the source of a confidence, on the part of many, that coal did actually exist within the limits of New-York. This question,. however, is now settled; and, as in many others, since we have the information, we forget the toil and labor with which it has been obtained. In a sketch like the present, we can merely glance at the progress of the work before us. The subdivision of the State into districts has been attended with some disadvantages, and on the other hand it has many advantages. The readers of the Geological Reports may find some repetitions, from the fact of several persons observing similar phenomena, being engaged upon a continuation of the same strata; and perhaps a want of unity may be apparent, which could only have been obtained by having a single head. On the other hand, there is no doubt but the work has been done more thoroughly on the present plan. Localities have been searched which might, perhaps, have escaped attention; and the value of the collections for the State and. |