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THE JOURNAL OF GEOLOGY.

In Scandinavia, if we judge from the most recent publications, there is, in spite of the general adherence to German nomenclature, a fuller recognition of the similarity between ancient and modern volcanic rocks than is to be found in any other part of Europe except England.

On the western coast of Norway, Reusch describes old lava flows of quartz-porphyry and more basic diabase amygdaloids which show spheroidal parting on a large scale due to cooling. These rocks are accompanied by tuffs and breccias which, in spite of subsequent dynamic action, still show their original characters. In one case, on the island of Gjeitung, occurs a deposit of pumice bombs cemented by what is now a chlorite schist.[1]

In Sweden Högbom describes the general distribution of post-Archean (Algonkian) eruptive rocks, many of which bear unmistakable evidence of volcanic character.[2] Otto Nordenskjold assigns the beautiful flow-porphyries and amygdaloids of the Elfdalen region to the same horizon, while the concludes that most of the Hälleflintas of southeastern Sweden (Småland) are surface lavas. He finds in them such well-developed fluidal, eutaxitic, rhyolitic and perlitic structures that they may be regarded as old rhyolites or devitrified obsidians.[3] The probably much younger and still glassy rhyolites of the gneiss area of Lake Mien are described by N. O. Holst.[4]

In Russia Tschernyschew describes from the central Urals many types of eruptive rocks, and among them both acid and basic volcanics of great antiquity, accompanied by their agglomerates, breccias and tuffs.[5]

In America the recognition of the true character and relationships of ancient volcanic rocks has been greatly retarded both

  1. ↑ Bömmelöen og Karmöen, pp. 109, 122, and 403, 1888.
  2. ↑ Geologiska Fören. i Stock. Förh., Vol. 15, p. 209, 1893.
  3. ↑ Bull. geol. Soc. Upsala, Vol. 1, Nos 1 and 2, 1893.
  4. ↑ Afhandl. Sverig. geol. Undersök. Ser. C, No. 110, 1890.
  5. ↑ Allgemeine geologische Karte von Russland, Bl. 139, Central Urals.Text 4° pp. 323 and 333, 1889.
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