Certain parts of the world are often loosely described as “rainless,” but, as we have stated elsewhere, there is actually no spot on earth at which rain (or snow, in the polar regions) has never been known to fall. In the driest part of the Sahara--the Libyan Desert, between Dakhel and Kufra--the explorer Rohlfs experienced a drenching rainstorm of three days’ duration in 1874. Neither is the Sahara, in spite of its proverbial heat, exempt from touches of real winter. Snow is a common occurrence in many parts of this desert, even at moderate altitudes. On the higher Saharan peaks snow lies on the ground all winter, and is sometimes found, in sheltered spots, in summer. Occasional falls of snow occur in all parts of Algeria, and several falls have been recorded in Lower Egypt. When all is said and done, the whole fabric of what now constitutes the science of climatology leaves much to be desired. Climate is of practical interest, first of all, on account of its effects on human life and health, and secondly because of its influence upon the crops that are the mainstay of man’s material prosperity. Under both these heads climatic data, as now commonly presented, ignore certain atmospheric activities of the utmost importance. For biological purposes no description of a climate can be regarded as even approximately complete that does not furnish, for the region under discussion, a detailed account of the different kinds of radiation received from the sun, their intensities and fluctuations; and there are few places in the world at which even a beginning has been made in the collection of such data. Again, the phenomena of atmospheric electricity, including radioactivity, are probably of real climatic significance, but we are still in the stage of speculation with regard to this subject. Possibly there are still other elements of climate, now wholly neglected, that will figure prominently in the climatology of the future. CHAPTER XIII ORGANIZED METEOROLOGY No other branch of science is so dependent upon the constant systematic cooperation of a multitude of workers as meteorology. There are, to be sure, some kinds of atmospheric phenomena that can be studied advantageously by the individual meteorologist, with no further aid from his scientific confrères than the same sort of interchange of ideas that prevails in all departments of knowledge; but the widespread processes that constitute weather and climate require for their observation--whether the purpose in view be weather forecasting, or the collection of climatic statistics, or the assembling of data from which to deduce the laws of atmospheric movements--a veritable army of colaborers, equipped with standardized instruments and keeping their records according to a uniform plan.