OR many years the most important name in climatology has been that of Wladimir Koppen. His first paper was published in i868, and at the time of his death, in I940, he had unfinished work in progress. In the seventy-two years of his professional career he touched every aspect of meteorology and climatology. He gave much thought to the problem of climatic classification, and in I900 his first paper on the subject appeared.' American geographers were given a brief summary of Koppen's classification six years later by Ward in a general article on the problems of climatic classification. In I9I8 Koppen published a revision of his classification and a new climatic map.2 Then, in a book that appeared in I923, Koppen3 described his system in great detail and used it for a survey of the climates of the whole earth. The system served as a basis for a wall map of the climates of the earth published in I928.4 A second edition of the book, with slight revisions, was published in I93 I.' Plans for the monumental "Handbuch der Klimatologie" had been made sometime earlier, and the first sections were published in I930. Kdppen's6 contribution to the "Handbuch" relating to the geographical system of climate appeared in I936. It was his last significant work on climatic classification. The best review of the K6ppen system in English is that by Leighly,7 which is especially valuable because it reduces the definitions to graphical forms that are readily apprehensible.