The great irregularities in individual storm paths may be appreciated by studying the ac companying chart (Fig. 2) showing the tracks of all the centres of low pressure which passed over the United States during January. 1901. The storms in that month were unusually severe over the North Atlantic Ocean. Of the thirteen tracks that are here charted four moved with a velocity of over one thousand miles daily; one of them at a velocity of less than five hundred miles daily; and one was stationary for one day. Fur ther details in regard to these storms are given in the text of the Monthly Weather Review for the month in question. More than one-half of the cyclonic storms that pass over the United States have been developed somewhere in the Pacific Ocean. Perhaps one-quarter originated within the United States. The others are first perceived off the coasts of the West Indies or on the Gulf of Mexico. The most severe storms are the hurricanes that begin in the tropical portion of the Atlantic, move westward and northward into the South Atlantic or Gulf States, then turn toward the northeast and disappear while still moving toward Europe. The paths pursued by
general cyclonic storms are apparently deter mined by the so-called general circulation of the atmosphere, but are modified considerably by the formation of cloud and rain or snow attending the storm.
The most extensive condensed collection of data relative to American storms is found in the "Contributions to Meteorology," by Professor Loomis, as revised and published in the Memoirs of the Arational Academy of Sciences, vols. iii., iv., and v. (Washington, 1885, 1887, and 1889). The details of current storm phenomena are pub lished regularly by the Weather Bureau in the Monthly Weather Review. The physical-mathe matical theories founded by Espy and Ferrel have been further developed in numerous me moirs, some of which will be found in a collec tion of translations published by the Smithsonian Institution in 1891. The current literature is contained in the successive volumes of the Me teorologisehe Zeitschrift (Berlin). A general sum mary of our knowledge of the mechanics of storms is given by Prof. F. H. Bigelow in his Report on International Cloud Work (Washington, 1900).