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THE DISTRIBUTION OF ANCIENT VOLCANIC ROCKS.
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subjects of investigation. From the first, their essential identity with modern volcanic products has been clearly recognized and repeatedly insisted upon—something which we may attribute to the doctrines of Hutton and to the uniformitarian principles of Lyell. Such geologists as Scrope, de la Beche, Sedgwick, Murchison, Jukes, Lyell and Ramsay, speak continually of lava-flows, tuffs, breccias and ash-beds in a way that implies no doubt in their minds as to the existence of volcanoes like those now active, in Paleozoic and pre-Paleozoic times. And more recently the delicate methods of modern petrography have in the same country been first made to establish the identity between ancient volcanic rocks and those of the present. The world is now but beginning to follow in this respect the lead set by Allport, J. A. Phillips, Judd, Bonney, Rutley, Harker, Cole and others in Great Britain. A few Englishmen, like Mallet or Hicks, have considered the oldest volcanic rocks either as originally different from those now produced, or as characteristic of some definite geological horizon, but, on the whole, the British school of geology, more than any other, recognizes a practical uniformity in the nature of volcanic action and products from the Archean to the present.[1]

In Germany and France volcanic rocks (Ergussgesteine) are recognized as abundant in certain of the earlier geological formations. Nevertheless there is in these countries a prevailing tendency to separate Tertiary from pre-Tertiary rocks of this class as things originally and genetically distinct.[2] It is noticeable that the earlier schemes of rock-classification, like those of Brongniart, Haüy, Cordier and K. C. von Leonhard, are quite purely mineralogical. The division of older and younger, or paleo- and neo-volcanic rocks is to be in part accounted for by the concentration of these masses in central Europe within the Permo-Carboniferous and Tertiary periods and their comparative

  1. ↑ See "The History of Volcanic Action in the Area of the British Isles," Presidential Addres by Sir Archibald Geikie, F.R.S., etc.Quart. Jour. Geol. Soc., Vols. 47 and 48, 1891-2.
  2. ↑ Roth: Sitzber. Berl. Ak. 1869, p. 72, et seq.Zirkel: Lehrbuch der Petrographie, 2d. ed., Vol. I., p. 838, 1893.
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