Page:The Journal of geology (IA journalofgeology21894univers).pdf/23

by the adherents to the so-called metamorphic school, like Dana, Logan, Rogers, Lesley and Winchell, who fail to find among the ancient foliated crystallines anything beside altered sediments, but perhaps even more by the influence of that most extreme of all Wernerians, Dr. T. Sterry Hunt. While antithetically opposed to the members of the metamorphic school in his notions of lithological character as an index of geological position, Dr. Hunt had in common with them the conviction that the ancient lavas and volcanic breccias, tuffs and ash-beds were normal aqueous deposits. The basic volcanics of eastern North America enter so argely into his "Huronian," and the acid types so largely into his "Arvonian," that his writings may still be used as suggestive of localities where ancient effusive rocks may be sought for.^[1]

But there have not been wanting those among the earlier American geologists who have clearly recognized the igneous members of the ancient crystalline formations, in spite of their disguised character. Prominent among them are E. Hitchcock, Emmons, Lieber, Foster and Whitney. Not only the igneous, but the volcanic (surface) character of the Lake Superior lavas has been maintained by Pumpelly,^[2] Wadsworth,^[3] Irving,^[4] Van Hise^[5] and the present writer.^[6] In Canada igneous rocks have always been regarded abundant in the oldest formations, while the volcanic character of some of them has been insisted on by Selwyn^[7] and mentioned by other members of the Canadian Geological Survey. A looseness of usage is, however, observable in some of these reports, where "volcanic" is made synonymous