Early Steps in the Classification of Climates

is little to add to Thornthwaite's account of the development of Koppen's ideas, except perhaps to note the world map of types of seasonal occurrence of precipitation that Koppen drew for Julius Hann's Atlas der Meteorologie (1887), which served as the basis for mapping his subtypes of climate defined by the occurrence of dry and rainy seasons. I wish to go back beyond the period—essentially the time embraced by Koppen's long adult career—with which Thorn thwaite concerned himself. Arnold Court has called our atten