The exact origin of the carbon dioxide theory has been stated so variously that it seems worth while to give the exact facts. Prompted by the suggestion, of Tyndall that glaciation might be due to depletion of atmospheric carbon dioxide, Chamberlin worked up the essentials of his early views before he saw any publication from Arrhenius, to whom the idea has often been attributed. In 1895 or earlier Chamberlin began to give the carbon dioxide hypothesis to his students and to discuss it before local scientific bodies. In 1897 he prepared a paper on "A Group of Hypotheses Bearing on Climatic Changes," Jour. Geol., Vol. V (1897), to be read at the meeting of the British Association at Toronto, basing his conclusions on Tyndall's determination of the competency of carbon dioxide as an absorber of heat radiated from the earth. He had essentially completed this when a paper by Arrhenius, "On the influence of carbonic acid in the air upon the temperature of the ground," Phil. Mag., 1896, pp. 237-276, first came to his attention. Chamberlin then changed his conservative, tentative statement of the functions of carbon dioxide to a more sweeping one based on Arrhenius' very definite quantitative deductions from Langley's experiments. Both Langley and Arrhenius were then in the ascendancy of their reputations and seemingly higher authorities could scarcely have been chosen, nor a finer combination than experiment and physico-mathematical development. Arrhenius' deductions were later proved to have been overstrained, while Langley's interpretation and even his observations were challenged. Chamberlin's latest views are more like his earlier and more conservative statement.] [Footnote 12: C. G. Abbot and F. E. Fowle: Volcanoes and Climate; Smiths. Misc. Coll., Vol. 60, 1913, 24 pp. W. J. Humphreys: Volcanic dust and other factors in the production of climatic and their possible relation to ice ages; Bull. Mount Weather Observatory, Vol. 6, Part 1, 1913, 26 pp. Also, Physics of the Air, 1920.] [Footnote 13: H. Arctowski: The Pleonian Cycle of Climatic Fluctuations; Am. Jour. Sci., Vol. 42, 1916, pp. 27-33. See also Annals of the New York Academy of Sciences, Vol. 24, 1914.] [Footnote 14: W. Koeppen: Ueber mehrjaehrige Perioden der Witterung ins besondere uezer die II-jaehrige Periode der Temperatur. Also, Lufttemperaturen Sonnenflecke und Vulcanausbrueche; Meteorologische Zeitschrift, Vol. 7, 1914, pp. 305-328.] CHAPTER IV THE SOLAR CYCLONIC HYPOTHESIS