“What are climatic statistics good for? To this query one is tempted to retort: What are they _not_ good for? Let us set down a few typical cases in which such data are desired. “A merchant plans to undertake the sale of rubber coats in foreign markets. Hence he wishes to know all about the distribution of rainfall, both geographically and as to season. Which are the rainy regions of the globe? When do the heaviest occur in each of these regions? Where do the prevailing temperatures indicate the need of heavy coats, and where light? “An invalid contemplates visiting a certain health resort. What mean temperatures occur there at the season of the proposed visit? What ranges of temperature between day and night? How much does the temperature vary from day to day? How much sunshine may be expected? Is the atmosphere moist or dry? What of the winds? Such are some of the questions he is likely to ask. “A horticulturist proposes to introduce a foreign plant in this country. Where will he find the most favorable climate for it? In order to settle this question he first tries to secure certain information about the climate of the plant’s original habitat—the march of temperature through the season of growth, average dates of first and last frost, normal fluctuations of rainfall, humidity, sunshine, etc. If the desired information is obtained, the next step is to ascertain where (if anywhere) similar climatic conditions prevail in the United States, and this is generally an easy task. “An engineer is planning a sewer system. He needs data of excessive rainfall for the locality under consideration, so that he may estimate the maximum amount of storm-water the sewers will ever need to dispose of in a given time. Their capacity should not exceed this amount beyond a reasonable margin of safety: otherwise cost of construction would be unnecessarily great. “This list of examples might be extended almost indefinitely. It will suffice, however, to show how wide a range of climatic information is required to meet all possible demands. The different branches of industry are concerned with different sets of climatic data. One set helps determine the best location for a railroad: another the kind of goods that will be shipped over it and the way in which they will need to be packed and cared for during shipment. The climatic conditions that must be considered in planning a military campaign are quite unlike those that engage the attention of a hydrological engineer in laying out a system of irrigation. Climatic statistics of interest to aviators are not identical with those that bear upon the problems of ecology or forestry or sanitation. In short, climate means different things to different people.”