Abercromby and Hildebrandsson have renewed their recommendations for a re-classification of clouds in ten fundamental types, in which the first part of the compound name, such as cirro-stratus, cirro-cumulus, etc., is to be in a measure indicative of the height of a cloud.
Hildebrandsson has charted the differences of monthly means of air pressure for January, 1874 to 1884. In January, 1874, the values at nearly all the stations in the Northern Hemisphere, were plus, and those in the Southern, minus. It is to be hoped that such general discussions of this important meteorological element may be continued.
General A. Von Tillo has determined, by means of the planimeter, the distribution of temperature and pressure from Teisserenc de Bort's charts. The mean pressure over the Northern Hemisphere for January, he finds to be 29.99 inches (761.7 millimeters), and the temperature 46°.9 (8°.3 C.); in July, 29.806 (758.5 mm.) and 72°.7 (22°.6 C.). In Russia he finds an increase of one millimeter of pressure to correspond with a decrease of 1°.6 C. in temperature.
Doberck, after investigation of September typhoons at Hong Kong, attributes their appearance to the relatively low pressure then existing between Formosa and Lyon.
The valuable and elaborate investigation of American Storms, by Professor Elias Loomis has been completed. Loomis has thoroughly discussed barometric maxima and minima areas as presented by the maps of the Signal Service, from which it appears that these areas are in general elliptical, with the longest axis nearly twice that of the shortest in the high areas, while the difference is less in low areas. He has also investigated the winds relative to baric gradients, thus affording valuable data for proving various meteorological theories. Loomis' researches regarding the movement of maximum areas verify those which have been set forth from time to time in Signal Service publications; wherefrom it appears that high areas have a more southerly movement than low areas.
Van Bezold has put forth a memoir on thermodynamics, while Helmholtz, Oberbeck, and Diro-Kitso have contributed valuable memoirs on motions caused by gravitation and the varying density of the air. These furnish meteorologists with important results as to the laws of fluid or gaseous motions. It is gratifying to Americans to note that the valuable results obtained by Ferrel in his many memoirs are confirmed by these later investigations.
Undoubtedly the most important meteorological event within the past year was the discontinuance, on January 1, 1888, of the system of International Simultaneous Meteorological reports inaugurated in accordance with the agreement of the conference at Vienna in September, 1873. As the charts of storm tracks, based on these observations, have been published by the United States Signal Service one year behind the date of the observations, the completion of this work in printed form for the general public should occur about December 31, 1888.
A few remarks in connection with this unparalleled set of observations may not be out of place. The congress which agreed upon this work, met in accordance with invitations issued by the Austrian Government in September, 1873. The co-operation decided upon at this congress took practical shape January 1, 1874, at which date one daily simultaneous report was commenced from the Russian and Turkish Empires, the British Islands, and the United States: the energetic co-operation of these nations being assured through Professor H. Wild for Russia; Professor A. Coumbary for Turkey; Mr. Robert H. Scott for Great Britain; and Bvt. Brig. General A. J. Meyer, for the United States. Concurrent action followed shortly after on the part of Austria, through Professor Carl Jelinek; Belgium through Professor E. Quetelet; Denmark through Capt. Hoffmeyer; France through Monsieurs U. J. Leverrier, Marie Davy, and St. Claire Deville; Algiers by General Farre; Italy by Professor Giovanni Cantoni; the Netherlands by Professor Buys Ballot; Norway by Professor H. Mohn; Spain by Professor A. Aquilar; Portugal by Professor F. de Silveira; Switzerland by Professor E. Plantamour; and the dominion of Canada by Professor G. T. Kingston. Within a year the average number of daily simultaneous observations made outside the limits of the United States increased to 214. Later, the co-operation of the Governments of India, Mexico, Australia, Japan, Brazil, Cape Colony, Germany, and Greece, was obtained, and also of many private observatories at widely separated points throughout the Northern Hemisphere.
In the sixteen years during which simultaneous meteorological observations were continued, reports were received from nearly fifteen hundred different stations, about one-half being from land stations, and the others from vessels of the navies and the merchant marine of the various countries.
The total number of storm centers, counting one for each 5-degree square over which the centre has been traced from the International Simultaneous observations of 1878 to 1887, inclusive, aggregates over forty-two thousand, an annual average of over four thousand two hundred. Less than 1/25 of 1 per cent. of these storms occurred south of the parallel of 10°, and only ¼ of 1 per cent. south of the parallel of 15°. In marked contradistinction to this freedom of the equatorial regions from storms, there is to be noted the excessive prevalence of these phenomena between the parallels of 40° and 60°, north; in which regions substantially two-thirds of the storms of the Northern Hemisphere occurred; while between the parallels of 45° and 55°, north, 36 per cent. of the entire disturbances are recorded. The most remarkable belt of storm frequency on the Northern Hemisphere is that extending from the Gulf of Saint Lawrence westward to the extreme end of Lake Superior, as nearly 8 per cent. of all the storms of the Northern Hemisphere passed over this limited region; the maximum frequency (1.2 per centum) occurring over the 5-degree square northeastward of Lake Huron.