It is olitlicult to describe or exhibit the cli matic peculiarities of any region without the use of charts. Elaborate publications of this kind. for United States weather, have issued from the Weather Bureau at Washington; the Climatic ('harts for the Trues 1870-99 show the normal precipitation for each quarter of the year, the normal percentage of sunshine, the normal baro metric pressure, reduced to sea-level, the normal temperature of the air at the surface of the earth, the mean maximum and mean minimum temperatures, the highest and lowest recorded temperatures. In addition to these. charts of first and last frost and of prevailing winds have also been published. The ordinary popular text books on meteorology are very largely occupied with climatology. properly so called. Of these, that by Prof. Frank Waldo (New York. 1896) is probably the most complete for America; the treati*es of Argot, Truitt' at" mentaire de nuct6 roloqic (Paris, 1899) and Harm's Handbuch der Miami°logic (Stuttgart, 1893) are the most complete for European data. But in almost all respects, the most careful work of the kind ever published is entitled .1 la s of _II eteorology, col. iii. of Bartholomew's Physical Atlas (London, IS99 u this we have a general text on climatology ac companied by about four hundred maps ing the climate and the weather of all parts of the globe for each month and for the whole year, and also an admirable bibliographical list of more important modern publications on this sub ject. A table of about forty columns of numerical data would seem to be necessary in order to pro sent-the complete idea of climate as imagined by Hann. in his great text-book on Climatology: but most of these are included in the plates and diagrams collected in Bartholomew's Physical Atlas.
Perhaps the most important feature control ling plant-life is the relative distribution of timperature and rain from month to month dur ing the year. Climatic types have been elabo rated by Harrington. Henry. and others, based upon this distribution of rain. Thus, in one region we have the prevailing slimmer rains; in another, the prevailing winter rains; in still other places, the rains are divided into two seasons with dry weather between. Professor Hinrichs introduced the idea of a climatic dis tinction based upon the law governing the num ber of light and heavy rains that had fallen within a given space in a year's time As the largest falls occurred least frequently, and so also the smallest falls, there is some intermediate rainfall that is most likely to happen. By count ing up these different quantities, one obtains a series of numbers that may be represented by the equation of probabilities, and the constant term in this equation becomes the so-called 'Hin richs Climatic Factor.' The influence of climate on crops is a matter of continued investigation in the various agri cultural experiment stations throughout the civ ilized globe, and the reader may refer to the Experiment Station Record, published regularly by the United States Department of Agriculture, for the latest information on the subject. A summary of this work has led some authorities to the conclusion that cereal crops are raised successfully only by means of careful special cul tivation, so that the resulting crop is not so much an evidence of the influence of climate as of the influence of human skill and husbandry in modifying and assisting, climate. In the interior of continents. the clear, dry air facilitates great ranges of temperature, both diurnal and annual: the soil is dry, evaporation rapid, and delicate plants do not survive the rigors of cold and drought. On the other hand, an oceanic or insu lar climate is more uniform as to temperature. moisture, and cloudiness. and more favorable to the development of animals and plants. The in fluence of climate in disease is principally second ary in that climatic conditions affect the growth of germs. fungi, and noxious animal], through which man suffers.
There is no well-authenticated case of an ap preciable change of climate within the past two thousand years. The researches of Eginitis on
the climate of Greece seem to establish this prin ciple beyond doubt. Neither is it possible that any change on the surface of the earth due to man—such as deforestation, reforestation, agri culture, canals, railroads, or telegraph lines— can have had anything more than the slightest local effe•, if any, on climatic phenomena that depend upon the action of the whole atmosphere. On the other hand, it is probable that appreciable changes have taken place in the course of the very long intervals known as geological periods or a•uns. The phenomena of the flora, the fauna, the erosion. and the geological all agree in showing that there have been tinies when the Lake Region and the Saint Lawrelice Valley, the Middle States and New England. were cov ered with ico and glaciers; a similar condition has prevailed over northwestern Europe. Such changes may have been produced by changes in the elevation of the land and distribution of the ocean, by periodic changes in latitude, by changes in the composition of the eart103 atmosphere, or by changes in solar radiation. All of these are plausible causes; but at present there is no agreement of authorities as to the real cause of the changes in so-called geological climate. To these changes in the continents and the climates, we may plausibly attribute the development of a great variety of flora and fauna, the migratory habits of birds, the traditions of the early his tory of the human race, and the extinct plants and animals of paleontology. See EVOLUTION.
One of the most evident causes of the differ ences of climate is the relation of the wind to the land and ocean. When the prevailing wind is from the ocean, the land experiences moist and usually cloudy or rainy weather. This is due essentially not so much to the temperature of the water as to the mere fact that water of any temperature will evaporate largely into the air, and fill it with moisture. Thus, it is an error to say that the climate of Great Britain and west ern Europe is affected by the Gulf Stream. or that the climate of California and British Colum bia is controlled by the Japan Current : in both these cases it is the moist ocean wind that brings cloud and rain, and the amount of this latter is not influenced in the slightest degree by the Gulf Stream or the Kuro Siwo. Another important consideration in climatology is the relation of the wind to the mountain ranges. Thus, on the wind ward side of a range, there is ascending air which causes damp weather with cloud or rain; where as, on the leeward side of a mountain range there is descending air, whi•h is alwa3s dry and clear, and frequently quite warm.
The relation of climate to physiography has been essentially- a relation of cause and effect. The surface features of the land, as we now know them, present to ns hills and valleys which we may easily recognise as the result of erosion by wind and water, continued for many ages, and assisted by frost and the varying hardness of the different kinds of rock and soil. These features. as we now see them. are usually all that remain after a depth of many thousauds of feet of soil and rock has been broken clown and carried into the sea. Geology tells us what strata and masses must, at one time, have ex isted ; but physiography shows how 'all this material has been carried away by the action of the frost, wind, and rain, which constitute prom inent features of the climate.
Among the works that treat of meteorological climate. the first place must be given to Bar tholomew. _I bvs, vol. iii. Meteorology (London, 1899). For the United States specifically, con sult the various publications of the Weather Bureau, and Waldo, Elementary Mcfrorology iNew York, 1890). For the world in general.
consult: lann, Handbuch tier Klimatologie (Stuttgart, 18971 Woeikof, l)ic Klimate dcr Erdc (Jena, 16S7) ; and Ilann, Lehrbuch der Me teorologic (Stuttgart, 1901).