. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. THE EVOLUTION OF I'ETROLOOICAL IDEAS. 299 fact, and side by side with these sire placed Ho-ures of iiiicropei^'inatitic and spherulitic sti'uctures copied from l^ Iddines's inenutir on tlie rocks of Obsidian CliH'. (Fi_os. 1-4.) In the case of the aUoys th(> sph<n'ulitic stnutiiics are characteiistic of I'apid cooling and the niicropeomatitic structure's of slow cooling'. The mode of occurrence of the same sti'uctures in roc
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. THE EVOLUTION OF I'ETROLOOICAL IDEAS. 299 fact, and side by side with these sire placed Ho-ures of iiiicropei^'inatitic and spherulitic sti'uctures copied from l^ Iddines's inenutir on tlie rocks of Obsidian CliH'. (Fi_os. 1-4.) In the case of the aUoys th(> sph<n'ulitic stnutiiics are characteiistic of I'apid cooling and the niicropeomatitic structure's of slow cooling'. The mode of occurrence of the same sti'uctures in rocks is strictly in accordance with this vieW. A t-omparison of the structures in the two cases makes it almost inipossi])le to Ixdieve that the resend)lances ^,,,'-rf'^''^^f^^'frf!'nr~^. X ^^'^''^iiiiiiM^^. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Smithsonian Institution. Board of Regents; United States National Museum. Report of the U. S. National Museum; Smithsonian Institution. Report of the Secretary. Washington : Smithsonian Institution
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Keywords: ., bookauthorsmithsonianinstitutio, bookcentury1800, bookdecade1840
