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CHAPTER II THE VARIABILITY OF CLIMATE THE variability of the earth's climate is almost as extraordinary as its uniformity. This variability is made up partly of a long, slow tendency in one direction and partly of innumerable cycles of every conceivable duration from days, or even hours, up to millions of years. Perhaps the easiest way to grasp the full complexity of the matter is to put the chief types of climatic sequence in the form of a table. TABLE 2 TYPES OF CLIMATIC SEQUENCE 1. Cosmic uniformity. 7. Bruckner periods. 2. Secular progression. 8. Sunspot cycles. 3. Geologic oscillations. 9. Seasonal alternations. 4. Glacial fluctuations. 10. Pleionian migrations. 5. Orbital precessions. 11. Cyclonic vacillations. 6. Historical pulsations. 12. Daily vibrations. In assigning names to the various types an attempt has been made to indicate something of the nature of the sequence so far as duration, periodicity, and general tendencies are concerned. Not even the rich English language of the twentieth century, however, furnishes words with enough shades of meaning to express all thatis desired. Moreover, except in degree, there is no sharp distinction between some of the related types, such as glacial fluctuations and historic pulsations. Yet, taken as a whole, the table brings out the great contrast between two absolutely diverse extremes. At the one end lies well- nigh eternal uniformity, or an extremely slow progress in one direction throughout countless ages; at the other, rapid and regular vibrations from day to day, or else irregular and seemingly unsystematic vacillations due to cyclonic storms, both of which types are repeated millions of times during even a single glacialfluctuation. The meaning of cosmic uniformity has been explained in the...