2. _Rainfall (isohyetal) charts._ These show the distribution of rainfall (including snowfall, expressed in equivalent depth of water); especially for each month and for the year. Other charts may show the average number of rainy days; average snowfall (actual depth, not water equivalent); seasonal distribution of rainfall; etc. 3. _Wind charts._ These are drawn in various forms, to show the prevailing wind directions, the frequency of winds from different directions, the average force of the winds, etc. Charts of the winds at different levels above the earth’s surface will eventually be drawn for the use of aeronauts, but such charts are still in a tentative stage. [Illustration: A MODERN ISOTHERMAL CHART OF THE GLOBE. (_Hann, 1901_) The isotherms show the mean annual temperature in centigrade degrees.] As in the case of tabulated climatic data, the number of charts that might be drawn to bring out different features of climate is practically unlimited. Sunshine, cloudiness, humidity, barometric pressure, and the frequency of various special phenomena, such as thunderstorms, hail, tornadoes, droughts, etc., are all charted in some of the more extensive works on climate. Large atlases have been published to portray the climates of certain countries. The study of the actual distribution of climates over the earth, as distinguished from that of climate in general, is sometimes called _climatography_. Climates are variously classified, usually on the basis of one or more of the climatic elements, but sometimes with reference to their effects. The most familiar classifications refer to temperature. We speak of tropical, temperate, and polar climates; but in using these terms it should not be forgotten that other things besides latitude control the distribution of temperature. Location with respect to the ocean or other large bodies of water is almost equally important. A land surface grows warm by day and in summer, and grows cold by night and in winter, much more rapidly than a water surface, and the adjacent air varies in temperature accordingly. Hence we have a classification of climates as _marine_ and _continental_. The former, under the influence of oceanic winds, have a moderate range of temperature, while the latter are subject to extremes of heat and cold. With increase of altitude temperature is diminished, but rainfall is generally increased. The distribution of rainfall is also determined to a great extent by the paths of cyclonic storms. Such are a few of the many things that control the complex distribution of climates.