This leads us to another difficulty. The icy coating just mentioned has, for some years, been called “glazed frost” by the British Meteorological Office, and the United States Weather Bureau now calls it “glaze.” It has likewise been called, even in scientific books, “silver thaw”; and an instance of its occurrence on a large scale is termed, both popularly and scientifically, an “ice storm.” To pursue this lamentable record of cross-purposes just a little further, it may be added that the expression “silver thaw,” besides being one of the aliases of glaze, or glazed frost, has been applied in various official British publications, until recently, to a very different rough or feathery deposit of ice from fog, now called by both the Meteorological Office and the Weather Bureau “rime.” Needless to say, when the scientific authorities are unable to agree about these terms, our dictionaries are sadly at sea in regard to them; so, altogether, the task of writing a chapter on precipitation is beset with verbal difficulties that would not be encountered in writing on many far more recondite subjects. Fortunately the name of the most important kind of precipitation--rain--is reasonably free from ambiguity. To be sure, opinions may differ as to whether a “Scotch mist” is a rain or a wet fog--and if one happened to have insured a lawn fête against rain at Lloyds’ the uncertainty on this point might lead to litigation--but, generally speaking, “it rains or it does not rain,” as we are told in the books on logic. “Rain,” says Dr. Hellmann, “is the most widespread, most frequent, and most copious form in which the aqueous vapor of the atmosphere condenses. The area of its distribution embraces the whole surface of the earth, with the exception of the interior of Antarctica and probably of northern Greenland. The English and the Norwegian expeditions found no rain even at the edge of Antarctica. As the land rises inland to an altitude of about 2,800 meters about the South Pole, it may safely be assumed that only snow and no rain falls in the heart of Antarctica. At the North Pole, which lies in the midst of the sea, it probably rains at times; while on the high plateau of northern Greenland probably snow alone falls. As to its frequency, there are arid regions in which the average annual number of days with rain is less than one, while this number probably rises to 280 in some tropical districts. With the exceptions of the polar regions already mentioned, there are probably no regions where it never rains.”