8 THE JOURNAL OF GEOLOGY. 



In Scandinavia, if we judge from the most recent publica- 

 tions, 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.^ 



In Sweden Hogbom describes the general distribution of 

 post-Archean (Algonkian) eruptive rocks, many of which bear 

 unmistakable evidence of volcanic character.^ Otto Norden- 

 skjold assigns the beautiful flow-porphyries and amygdaloids of 

 the Elfdalen region to the same horizon, while he concludes that 

 most of the Halleflintas of southeastern Sweden (Smaland) 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. Hoist. ^ 



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 agglom- 

 erates, breccias and tuffs. ^ 



In America the recognition of the true character and relation- 

 ships of ancient volcanic rocks has been greatly retarded both 



^ Bommeloen og Karmoen, pp. 109, 122, and 403, 1888. 

 ^'Geologiska Foren. i Stock. Forh., Vol. 15, p. 209, 1893. 

 3 Bull. geol. Soc. Upsala, Vol. i, Nos. i and 2, 1893. 

 * Afhandl. Sverig. geol. Undersok. Ser. C, No. no, 1890. 



sAllgemeine geologische Karte von Russland, Bl. 139, Central Urals. Text 4" 

 pp. 323 and 333, 1889. 



