THE DISTRIBUTION OF ANCIENT VOLCANIC ROCKS. 5 



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 orig- 

 inally 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.^ 



In Germany and France volcanic rocks (^Ergussgesteine) are 

 recognized as abundant in certain of the earlier geological form- 

 ations. Nevertheless there is in these countries a prevailing ten- 

 dency to separate Tertiary from pre-Tertiary rocks of this class 

 as things originally and genetically distinct.'' It is noticeable 

 that the earlier schemes of rock-classification, like those of 

 Brongniart, Haiiy, 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 



^ See "The History of Volcanic Action in the Area of the British Isles," Presiden- 

 tial Address by Sir Archibald Geikie, F.R.S., etc. Quart. Jour. Geol. Soc, Vols. 47 

 and 48, 1891-2. 



-RoTH: Sitzber. Berl. Ak. 1869, p. 72, ei seq. ZiRKEL : Lehrbuch der Petro- 

 graphie, 2d. ed., Vol. I., p. 838, 1893. 



