Nevertheless it is not yet possible to determine how warm the oceans were at the actual time of the Permian glaciation. Some faunas formerly reported as Permian are now known to be considerably older. Moreover, others of undoubted Permian age are probably not strictly contemporaneous with the glaciation. So far back in the geological record it is very doubtful whether we can date fossils within the limits of say 100,000 years. Yet a difference of 100,000 years would be more than enough to allow the fossils to have lived either before or after the glaciation, or in an inter-glacial epoch. One such epoch is known to have occurred and nine others are suggested by the inter-stratification of glacial till and marine sediments in eastern Australia. The warm currents which would flow poleward in inter-glacial epochs must have favored a prompt reintroduction of marine faunas driven out during times of glaciation. Taken all and all, the Permian glaciation seems to be accounted for by the cyclonic hypothesis quite as well as does the Pleistocene. In both these cases, as well as in the various pulsations of historic times, it seems to be necessary merely to magnify what is happening today in order to reproduce the conditions which prevailed in the past. If the conditions which now prevail at times of sunspot minima were magnified, they would give the mild conditions of inter-glacial epochs and similar periods. If the conditions which now prevail at times of sunspot maxima are magnified a little they seem to produce periods of climatic stress such as those of the fourteenth century. If they are magnified still more the result is apparently glacial epochs like those of the Pleistocene, and if they are magnified to a still greater extent, the result is Permian or Proterozoic glaciation. Other factors must indeed be favorable, for climatic changes are highly complex and are unquestionably due to a combination of circumstances. The point which is chiefly emphasized in this book is that among those several circumstances, changes in cyclonic storms due apparently to activity of the sun's atmosphere must always be reckoned. FOOTNOTES: [Footnote 46: W. H. Hobbs: Characteristics of Existing Glaciers, 1911. The Role of the Glacial Anticyclones in the Air Circulation of the Globe; Proc. Am. Phil. Soc., Vol. 54, 1915, pp. 185-225.] [Footnote 47: R. D. Salisbury: Physiography, 1919.] [Footnote 48: Griffith Taylor: Australian Meteorology, 1920, p. 283.] [Footnote 49: J. D. Whitney: Climatic Changes of the Later Geological Times, 1882.] [Footnote 50: E. E. Free: U. S. Dept. of Agriculture, Bull. 54, 1914. Mr. Free has prepared a summary of this Bulletin which appears in The Solar Hypothesis, Bull. Geol. Sec. of Am., Vol. 25, pp. 559-562.] [Footnote 51: G. K. Gilbert: Lake Bonneville; Monograph 1, U. S. Geol. Surv.] [Footnote 52: C. E. P. Brooks: Quart. Jour. Royal Meteorol. Soc., 1914, pp. 63-66.]