PI liy is ^^y^^ ii ilffilii lie Hi^liiii^m^ lliiip 'JiiiPPi'^^^^^^ llilliiiiSgs: iMii|i|iiiilltiilli lllipiiiiii^iiiliii iilii Sill lii !ps^^ ill liw^ ■ii liiiiiiti ii ENGIN.kMATH. SCIENCES lib/ THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES GIFT ^xl' U. S. DEPARTMEI^T OF AGRICULTURE, WEATHER BUREAU. BUIiliETIN No. 11. I^EI^OI^T OF THE INTINATIOML MfflOROLOGICAL COIRESS, HELD AT CHICAGO, ILL, AUGUST 21-24, 1893, UNDER THE AUSPICES OF THE Congress Auxiliary of the World's Columbian Exposition. EDITED BY OLIVER li. FASSIG, SECRETARY. Pnbllshed by authority of the Secretary of Agrlculttire. WASHINGTON, D. C: WEATHER BUREAU. 1894. I Part II is in press. It will contain the papers of^ — Section IV. History and Bibliography. Section V. Agricultural Meteorology. Section YI. Atmospheric Electricity and Terrestrial Magnetism. LETTER OF TRANSMITTAL. U. S. Department op Agriculture, Weather Bureau, Washington, D. C, September- 9, 1893. Sir: I have the honor to transmit herewith a document entitled " Report of the International Meteorological Congress, held at Chicago, 111., August 21-24, 1893," and to recommend its publication as Weather Bureau Bulletin No. 11. Very respectfully, Hon. J. Sterling Morton, Secretary of Agriculture. Mark W. Harrington, Chief of Weather Bureau. MathsmatJcai Sciences Liorary INTRODUCTION. "^,'''' ^^ v.i The Congress Auxiliary of the World's Columbian Exposition was organized by authority and with the support of the Exposition Cor- poration for the purpose of bringing about a series of conventions of leaders of the various departments of human thought. The various congresses held their sessions in the Memorial Art Palace in the city of Chicago, from May until October, 1893 ; those in the Department of Science and Philosophy were assigned to the week commencing August 21. In this department provision was made for a congress on Meteorology, Climatology, and Terrestrial Magnetism. In November, 1892, the President of the Congress Aux- iliary, Mr. C. C. Bonney, invited the Chief of the Weather Bureau to organize such a congress. In accordance with this request, I called a conference of gentlemen to consult with me in the arrangement of a programme. The following persons responded to the call and met me at my office on December 21 : Professors Cleveland Abbe, F. H. Bigelow, Thomas Russell, C. A. Schott, Lieut. Commodore Richardson Clover, and Mr. 0. L. Fassig. As a final result of the conference the organization indicated on page iv was effected and the programme shown in the Table of Con- tents was arranged. The papers to be submitted were to be of a strictly scientific character. Authors of papers were to be requested to present in the best manner the present state of our knowledge of the particular branch of the science under consideration. It was the purpose of the officers of the Congress Auxiliary to print in the English language all papers read at the various conferences, together with an account of the daily proceedings. As this purpose could not be fulfilled by the Auxiliary, and as it was considered desirable to publish the papers of the meteorological congress as soon as practicable, other means of publication had to be sought. The matter was presented to the Secretary of Agriculture, the Hon, J. Sterling Morton, who approved the publication of the papers as a bulletin of the U. S. Weather Bureau. The failure of the Auxiliary to provide translators for the many papers written in foreign languages caused the labor of translation to devolve upon the chairmen of the sections ; to these gentlemen, as well as to Prof. Alexander Ziwet, of the University of Michigan, and to Mr. Robert Seyboth, of the Weather Bureau, I desire to express my obligation for their generous assistance. Mark W. Harrington, Chairman. ORGANIZATION. O-ENBRAL COMMITTEE. CHAIRMAN. Mark W. Harrington, Chief of U. S. Weather Bureau, Washington, D. C. VICE-CHAIRMAN. Dr. H. C Prankenfleld, Local Forecast OflBcial, Chicago, 111. SECRETARY. Oliver Li. Fasslg, Librarian, U. S. Weather Bureau, Washington D. C. MEMBERS OF THE COMMITTEE. Prof. Cleveland Abbe, Weather Bureau, Washington, D. C, Chairman of Sec- tion on Theoretical Meteorology. tileut. W. H. Beebler, U. S. Navy, Hydrographic Office, Washington, D. C, Chairman of Section on Marine Meteorology. Prof. F. H. Blgelow, Weather Bureau, Washington, D. C, Chairman of Section on Atmospheric Electricity and Terrestrial Magnetism. Prof. Chai'les Carpmael, Director Canadian Meteorological Service, Toronto; Mr. A. Lawrence Rotcb, Director of Blue Hill Observatory, Boston, Mass. ; Chairmen of Section on National Weather Services. Maj. H. H. C. Dunwoody, U. S. Army., Weather Bureau, Washington, D. C, Chairman of Section on Agricultural Meteorology. Mr. Oliver Ij. Fassig, Washington, D. C, Chairman of Section on History and Bibliography. Prof. F. B. Nipher, Washington University, St. Louis, Mo., Chairman of Sec- tion on Climatology. Prof. Thomas Russell, Office of U. S. Engineers, Sault Ste. Marie, Mich., Chairman of Section on Rivers and Floods. Prof. C. A. Scliott, Coast and Geodetic Survey, Washington, D. C. ; Mr. H. H. Clayton, Boston, Mass.; Chairmen of Section on Instruments and Methods. LOOAIi OOMMITTEB. (CHICAOO.) R. Grigsby Chandler. W. S. Jackman. Elias Colbert. William S. Seaverns. OsBiAN Guthrie. Charles B. Thwinq. MINUTES OF THE PROCEEDINGS. Memorial Art Institute, Chicago, III., Monday, August 21, 1893. Monday, August 21, at 10 a. m., the congresses of the Department of Science and Philosophy were formally opened at the Memorial Art Institute with an address of welcome by Mr. C. C. Bonney, Pres- ident of the Congress Auxiliary of the Columbian Exposition. At the close of this general session, which lasted about one hour, the special congresses met in rooms assigned to them for organization and the reading and discussion of papers. The Congress on Meteorology, Climatology, and Terrestrial Mag- netism met in room No. 31, in which the regular sessions were held daily, from August 21 to August 24. At 11 a. m.. Prof. F. H. Bigelow, in the unavoidable absence of the Chairman, Prof. Mark W. Harrington, opened the Congress, welcoming the members and briefly stating its objects. The Congress had no legislative authority. The main purpose was to collect a series of memoirs prepared by writers of recognized merit in their respective fields of labor, outlining the progress and summarizing the present state of knowledge of the subject treated. These reports are to be printed in full in the English language, and will form a record of great and permanent value in the science of meteorology. At the conclusion of Prof. Bigelow's remarks Capt. A. P. Pinheiro, Director of the Brazilian Meteorological Service, was called upon to read his paper upon " Storms in the South Atlantic." ' Owing to the great number of papers and the absence of authors, the papers were largely read in abstract or by title by the chairmen of the respective sections. Lieut. Beehler, chairman of the section devoted to marine meteor- ology, read in abstract the following papers : " The forecasting of ocean storms and the best method of making such forecasts available," by William Allingham, Loudon. "The secular change of variation of the mariner's compass," by G. W. Littlehales, Washington, D. C. " Ocean temperatures and ocean currents," by Lieut. A. Hautreux, Paris. * As all papers presented to the Congress are printed in full in the following pages, no abstracts are given in the account of the daily proceedings. Viii CHICAGO METEOROLOGICAL CONGRESS. " The creation of meteorological observatories on islands scattered over the ocean," by the Prince Sovereign of Monaco. "The barometer at sea," by T. S. O'Leary, Washington, D. C. Mr. Fassig, chairman of the section on history and bibliography, presented for reading two papers of his section : "The meteorological work of the Smithsonian Institution," by the Secretary of the Smithsonian Institution, read by Mr. H. H. Clayton. "The meteorological work of the office of the Surgeon General, U. S. Army," by Maj. Charles Smart, read by Mr. Fassig. Prof. Charles Carpmeal followed with the reading of abstracts of the following papers of the section devoted to national services and methods, of which he is one of the chairmen : ■'The publication of daily weather maps and bulletins," by Mr. R. H. Scott, of London. " Can we by automatic records at three selected stations determine the energy of a flash of lightning ? " by A. McAdie, of Washington, D. C. " The utilization of cloud observations in local and general weather predictions," by A. McAdie, of Washington, D. C. Adjourned, at 1.30 p. m., to meet Tuesday, at 10 a. m. Tuesday, Augibst 22, 1893. The meeting was opened at 10 a. m. by the Chairman, Prof. Mark W. Harrington. The first paper of the day was by Lieut. Beehler on " The meteorological work of the Hydrographic Office of the U. S. Navy." During the reading of this paper, which was devoted largely to the work of Commodore Maury, Lieut. Beehler had placed upon a pedestal, for inspection, a fine bust of the commodore by the sculptor Valentine, of Richmond, Va. Prof. Lemstrom, of Helsingfors, moved to hold a preliminary in- formal session at 10 a. m., Wednesday, to decide upon a programme for the day, the formal session to begin at 10.30 a. m. This was agreed to. Prof. Mascart, of Paris, then gave a resume of his paper on " Op- tical phenomena," referring particularly to the explanation of the white rainbow. He also gave a resume of M. Chauveau's paper on " Instruments for the observation of atmospheric electricity." Capt. Pinheiro was called to the chair while Prof. Harrington read his paper on " The history of the daily weather map." Two papers by Maj. Dun woody, of the U. S. Weather Bureau, were presented, " Functions of state weather services " and " State weather services of the United States." Upon motion of Mr. Fassig, the del- egates to the Convention of Directors of State Weather Services, who were in session in an adjoining room, were invited to be present at MINUTES OF THE PROCEEDINGS. IX the reading of these papers ; the invitation was accepted and the del- egates attended in a body. At the close of the readings, Dr. Duncan, of Chicago, made some remarks upon the possibility of predicting epidemics as a result of the development of State weather services. Adjourned at 2 p. m. Wednesday, August 23, 1893. The informal conference agreed upon on the preceding day was held at 10.15 a. m. It was decided to read first the papers whose authors were present ; then the chairman of sections were to present the papers of their respective sections of which abstracts had been previously prepared. At 10.30 the reading of papers was resumed. Prof. Harrington requested Lieut. Beehler to take the chair. Prof. Carpmael continued the reading of the papers of his section, as follows : " The prediction of droughts in India," by W. L. Dallas, of Calcutta. " Plan for the prediction of floods," by M. Babinet, of Paris. Dr. Veeder, of Lyons, N. Y., read a paper on "An international cipher code for correspondence relating to auroras and magnetic disturbances." Prof. Bigelow, chairman of the section on atmospheric electricity and terrestrial magnetism, presented the papers of his section, read- ing some by title, some in abstract. He read at length his paper on " The magnetic action of the sun upon the earth," and it was discussed by those present. Father Faura, of the Manila Observatory, presented a paper upon " Signs preceding typhoons in the Philippine Islands." Father Faura also laid before the members an elaborate printed report upon ter- restrial magnetism in the Philippine Islands, prepared by P. R. Cirera, S. J., Director of the magnetic section of Manila Observatory. Copies of this report were distributed at the close of the session. Prof. Lemstrom, of Helsingfors, offered a resolution proposing that the Congress be divided into four sections, in which there should be a discussion as to the most important questions pressing for solution, and that these sections place before the General Congress a recommen- dation as to the method of carrying on the necessary observations or investigations, the General Congress to discuss such recommendations and take action thereon. The proposition was not agreed to, as such action would be foreign to the purpose of the Congress. Adjourned at 1.45 p. m. X CHICAGO METEOROLOGICAL CONGRESS. Thursday, August 24, 1893. The meeting was opened as usual in room No. 31, at 10.20 a. m., Lieutenant Beehler in the chair. The first paper of the day was by Father Denza on "Alpine meteo- rology," read in abstract by Father Alque. Mr. Rotch, associate chairman of the section devoted to national services, read, in abstract, the following papers of his section : '• Meteorological stations and the publication of results of observa- tions," by Dr. J. Hann, of Vienna. " Present conditions of the weather service — propositions for its improvement," by Dr. W. J. van Bebber, of Berlin. "The best method of testing weather predictions," by Dr. W. Koppen, of Hamburg. Prof. Bigelow then took the chair. In connection with the reading of Dr. van Bebber's paper. Prof. Carpmael suggested that a statement describing the method employed by the U. S. Weather Bureau in forecasting the weather be prepared and sent to Dr. van Bebber to be added to his paper ; that he would likewise prepare a statement describing the method employed by the Canadian Service. This w^ould add greatly to the interest and value of Dr. van Bebber's paper when published. Prof. Lemstrom then read a paper by Prof. Lindelof , of Helsingf ors, upon " The influence of the rotation of the earth on movements at its surface, etc." This was followed by a paper of his own on " The cosmical relations manifested in the simultaneous disturbances of the sun, the aurora, and the terrestrial magnetic field." The following resolution, offered by Lieut. Beehler, was then read and agreed to : Recognizing that the members of this Congress do not possess leg- islative powers, be it resolved that the following statement be added to the official report of the proceedings : In view of the importance of a number of the papers read before the Congress and impressed with the desire of international consideration of certain questions, we request special attention to the following points : 1. International co-operation in observations of auroras. 2. Simultaneous observations at the instant of Greenwich Noon, by all observers on land and at sea independent of, and in addition to, all other observations. 3. Investigation of the earth's magnetic polar field, and exact de- termination of the period of solar rotation. Mr. Fassig, chairman of the section on history and bibliography, then read abstracts of the following papers of his section : "Contribution to the bibliography of meteorology in the fifteenth to the seventeenth centuries," by Dr. Hellmann, Berlin. MINUTES OF THE PROCEEDINGS. XI " English meteorological literature of the fifteenth to the seven- teenth centuries," by Mr. G. J. Symons, London. . " Early individual observers of the weather in the United States," by Mr. A. J. Henry, Washington, D. C. "Contributions to theoretical meteorology in the United States during the Espy-Kedfield period ( 1830-'55)," by Prof. Wm. M. Davis, Cambridge, Mass. "Contributions to theoretical meteorology in the United States during the Loomis-Ferrel period (1855-'91," by Prof. Frank Waldo, Princeton, N. J. " A first attempt toward a bibliography of American contributions to meteorology," by Mr. Oliver L. Fassig, Washington, D. C. The Congress was then declared adjourned, sine die, by the pre- siding officer, Prof. F. H. Bigelow. Papers presented to the Congress and not especially referred to in this report were read by title only. Oliver L. Fassig, Secretary. TABLE OF CONTENTS. Page. Section I. — "Weather services and methods. 1. Meteorological stations and the publication of results of observation. Prof. Dr. J. Hann, Director Austrian Meteorological Service, Vienna.. 1 2. The publication of weather maps and bulletins. Robert H. Scott, Sec- retary Royal Meteorological Council, London 6 3. Functions of State weather services. Maj. H. H. C. Dunwoody, U. S. Army, Assistant Chief U. S. Weather Bureau, Washington, D. C 9 4. The predictions of droughts in India. W. L. Dallas, Assistant Meteoro- logical Reporter to the Government of India, Calcutta 1.3 5. Can we, by automatic records, at three selected stations determine the energy of a flash of lightning? Alexander McAdie, M. A., U. S. Weather Bureau, Washington, D. C 18 6. The utilization of cloud observations in local and general weather pre- dictions. Alexander McAdie, M. A. Plate i 21 7. An international cipher code for correspondence respecting the aurora and related conditions. Dr. M. A. Veeder, Lyons, N. Y 26 8. The best method of testing weather predictions. Prof. Dr. W, Koppen, Marine Observatory, Hamburg 29 9. The present condition of the weather service — propositions for its improve- ment. Prof. Dr. W. J. van Bebber, Marine Observatory, Hamburg.. 34 Appendices: I. Canadian service 41 II. Danish service 46 III. Norwegian service 45 IV. Russian service 46 V. Austrian service 48 VI. Hungarian service 49 VII. Netherland service 61 VIII. British service 55 IX. Berlin service 58 X. Swiss service 60 XI. United States service 62 Section II.— Rivers and floods. 1. Floods of the Mississippi River, with reference to the inundation of the alluvial valley. William Starling, Chief Engineer, Mississippi Levee Commission, Greenville, Miss 68 2. Flood planes of the Mississippi River. J. A. Ockerson, U. S. Engineer, Mississippi River Commission, St. Louis, Mo. Plates ii-iv 81 3. River-stage predictions in the United States. Prof. Thomas Russell, Office of U. S. Engineers, Sault Ste. Marie, Mich 89 4. Methods in use in France in forecasting floods. M. Babinet, Assistant Secretary of the Commission for Forecasting Floods, Paris 94 5. The four great rivers of Siberia. Dr. Franz Otto Sperk, Smolensk, Russia 101 xiii Xiv TABLE OF CONTENTS. Section II.— Rivers and floods — Continued. 6. Regimen of the Rhine region: high water phenomena and their predic- tion. M. von Tein, Central Bureau for Meteorology and Hydrography of Baden, Karlsruhe 117 7. The Nile. Mr. W. Willcocks, M. I. C E., Director General of the Res- ervoirs of Egypt, Cairo. Plate v 121 8. The best means of finding rules for predicting floods in water courses. M. Babinet, Paris 142 Section HI.— Marine meteorology. 1. The forecasting of ocean storms and the best method of making such forecasts available to commerce. William AUingham, London 150 2. The creation of meteorological observatories on islands connected by cable with a continent. Albert, Prince of Monaco 168 3. The marine nephoscope and its usefulness to the navigator. Prof. Cleve- land Abbe, U. S. Weather Bureau, Washington, D. C. Plate vi 161 4. The barometer at sea. T. S. O'Leary, U. S. Hydrographic OflBce, Wash- ington, D. C 167 o. The secular change in the direction of the magnetic needle; its cause and period. G. W. Littlehales, U. S. Hydrographic Office, Washington, D. C 174 6. Relations between the barometric pressure and the direction and strength of ocean currents. Lieut. W. H. Beehler, U. S. Navy, Chief of Division of Meteorology, U. S. Hydrographic Office, Washington, D. C. Plate VII : 177 7. The periodic and non-periodic fluctuations in the latitude of storm tracks. Dr. M. A. Veeder, Lyons, N. Y 185 8. North Atlantic currents and surface temperatures. Lieut. A. Hautreux, French Navy. Plates vni-x 192 9. Storms in the South Atlantic. Capt. A. P. Pinheiro, Chief of the Meteor- ological Service of the Brazilian Navy, Rio de Janeiro 204 LIST OF PLATES. I^J^IST I. Plate I. Relation between temperature and cloudiness. McAdie. Plate II. Location of gauges on the Lower Mississipppi River. Ockerson. Plate III. Highest annual stages of the Mississippi River and dates of their occurrence, 1872-'93. Ockerson. Plate IV. Hydrographs of the Mississippi, the Missonri, and the Ohio rivers, 1872-'92. Ockerson. Plate V. The Nile. Willcocks. Plate VI. The marine nephoscope. Abbe. Plate VII. Barometric pressure at sea and ocean currents. Beehler. Plate VIIT. Currents of the Atlantic in 1892. Temperatures of the surface of the sea in the Bay of Biscay. Hautreux. Plate IX. Drifting bottles, June, 1893. Hautreux. Plate X. Temperatures of the sea from the Gironde to the La Plata River. Hautreax. PAPERS READ BEFORE THE chicaCtO meteorological congress. .iLTJO-TJST 21-24=, 1893. SECTION I. WEATHER SERVICES AND METHODS. 1.— METEOROLOGICAL STATIONS AND THE PUBLICATION OF RESULTS OP OBSERVATIONS. Prof. Dr. J. Hann. I. — WHAT ADDITIONAL STATIONS ARE DESIRED FOR METEOROLOGICAL AND FOR CLIMATOLOGICAL PURPOSES ? In many important fields of meteorology the progress of our knowledge depends upon the uniform distribution of the meteoro- logical stations over the earth's surface, so that large districts shall not remain without observing stations. I will only point out that the important question, whether the mean temperature of the entire earth's surface as well as the quan- tity of precipitation, etc., undergoes periodic or continual changes, can only be settled when no great part of it remains without stations. Only then shall we be certain that changes in the mean condition of the atmosphere observed at certain stations are not compensated for in a contrary sense on those parts of the earth which lack stations. The vast extent of the ocean will always be a great obstacle to the investigation of the mean condition and variation of the atmosphere over the whole earth. It is the more important that all oceanic islands should, if possible, have meteorological stations, and this is especially true of the islands of the Pacific. There should be at least uninterrupted records of temperature and rainfall. Much prog- ress latterly has been made in this respect but much remains to be done. The southern oceans, unfortunately, remain almost without stations. Still, by buried thermometers on the islands in the South Pacific, Atlantic, and Indian oceans some temperature determinations may be made, since the determination of the constant earth tem- perature at suitable points may be employed as a substitute for the estimation of the mean air temperature when there is no prospect of establishing permanent stations. In the first place, I would insist on the occupation of the oceanic islands by meteorological stations, since here appear the great gaps 2 CHICAGO METEOROLOGICAL CONGRESS. in our knowledge of the meteorological conditions of the whole earth's surface. Referring to certain portions of the globe, it is very important that a ring of meteorological stations surrounding the North Pole should be in constant operation. The Polar region north of Europe and Asia is tolerably well surrounded by the meteorological stations of Russia, Norway, and Denmark, but a permanent station on Nova Zembla is perhaps attainable ; a similar station in Spitsbergen re- mains perhaps only a hope, but it would be of great importance for the determination of the climatological variation of the European frozen ocean. We have to thank Denmark for the installation of meteorological stations on the coast of west Greenland up to very high latitudes. Thence, further west, there exists a deplorable gap for which, how- ever, the explanation and excuse are not far to seek. Nevertheless, when possible, efforts should be made to establish a permanent me- teorological station in Arctic North America between 60° and 165° west from Greenwich, near the seventieth parallel, the further west the better. Point Barrow would be a suitable point for such a per- manent station. Perhaps this desideratum for science is already a reality. One or two of the stations in northern Alaska should be in constant operation. In the Antarctic latitudes there can be no question of permanent stations. The most southerly stations in South America and in New Zealand are, therefore, very important as being those in the highest latitudes which it is possible to reach in the southern hemisphere. Much value consequently attaches to the permanency of these stations and to the regular publication of the results of the observations. In the temperate latitudes of both hemispheres, so far as they are not occupied by the oceans, a sufficient number of stations has gen- erally been provided, and the existing gaps will no doubt shortly be filled. Matters are not so favorable as regards the occupation of the tropical zone by meteorological stations. The greatest gaps we find in South America. In tropical South America meteorological stations are almost completely lacking, at least in the interior. Some stations in the great Amazon Valley would be of much importance. In Para, Manaos, Teffe (Ega), Taba- tinga, and Iquitos, the establishment of meteorological stations would present no impossibility. In the same way stations could be estab- lished at some of the capitals of the interior Brazilian states. It is to be regretted that neither in Quito, which possesses an astronomical observatory, nor in Bogota, nor in Lima, are there meteorological stations which publish their observations.^ In short, tropical South 'The new meteorological observatory "Unanue," in Lima, will probably fill thi^ want. —Editor. ADDITIOiN-AL STATIONS DESIRED. 6 America remains the terra incognita as regards climatological and meteorological data. Even in tropical Africa, there is improvement in this respect, notwithstanding the fact that tropical South America is occupied by- civilized states, which is only true to a limited extent of the interior of Africa. If the Egyptian equatorial province was not, by the shortsighted and foreign policy of a European power, given up to the Mahdists, we should now have continuous meteorological data from Lado and the countries on the banks of Lake Victoria. A good beginning had already been made when barbarity interfered. Stations in the interior of the Congo States would be very desirable, but we must still wait for them, as well as for stations in the British and German claims in equatorial East Africa. There is, however, every prospect that in German East Africa meteorological stations will be established. Australia is already partially provided with stations, and, to all appearances, the number will be increased. For the study of certain interesting questions as to the daily period of wind direction and the daily period of the barometer, stations would be valuable if situated in the midst of a large, even plain. They should be provided with self-recording barometers and anemometers, and the observations should be published in extenso; a series of five-year observations would only suffice to answer the proposed questions, viz., daily period of wind direction and ampli- tude of one diurnal oscillation of the barometer. Those meteoro- logical services possessing such stations are requested to make the fact known. Stations on tropical plateaux, or better, on high mountains in the tropics, could contribute with advantage to the question of the ex- istence of long periods in the mean air temperature. Long ago, in the " Zeitschrift fiir Meteorologie," I stated my opinion that a lofty barometric station in the equatorial regions would give the best explanation of the temperature variation of the stratum of air lying between the station and sea level. The observations of pressure would give a much better indication of this than the ther- mometer itself, which gives only the local temperature and is subject to many^ disturbing influences. The barometer on a mountain is, therefore, to be regarded as a good air thermometer, or at least a kind of differential thermometer when the true height of the barometer is not known. It indicates the tem- perature of the whole underlying air stratum, or at least the varia- tions. There must also be a base station whose horizontal distance from the high station is so small that no considerable pressure gradi- ent (in a horizontal direction) can be suspected l^etween the two sta- tions during a period of some length, such as a year's mean. 4 CHICAGO METEOROLOGICAL CONGRESS. If we designate by B the height of the barometer at the base station, by b that at the high station, by h the difference of height between them, by Tthe air temperature in absolute measures (that is, t -\- 273°), by R the known constant (for dry air 29.3), the equation — db = dB^^ + ~-^j,. clt dh-dB^^=dh' is the pressure change at the high station, with the pressure variation at the corresponding place on the earth eliminated, which is only de- pendent on the temperature and vapor capacity of the air. The true thermic pressure variation at the height h is accordingly, for a sta- tion like Quito (6 = 548 millimeters, /?, = about 2,850 meters, « = -J (27° + 13.5), T being therefore 293°, R 29.3), d h' = 0.62 dtov dt = 1.61 d h' If the mean air temperature of the stratum between sea level and Quito changes 1°, the barometric level in Quito alters 0.62 millimeters. Changes of two-tenths of a degree centigrade correspond, therefore, to a pressure change of something more than 0.1 millimeter, which allows of accurate determination in the means of the year. If, for example, a period corresponding to the sun-spot period ex- ists in the mean air temperature, it must also be equally well shown in the pressure variations of the high station to allow its magnitude to be calculated. While the thermometer only gives the local air temperature of Guayaquil and Quito, for example, which is much influenced by chance circumstances, clouds, precipitation, etc., the barometer furnishes the true air temperature of the whole 2,850 meters of air, as well as the effect produced in the same way by changes in the amount of vapor, that is to say, in a certain degree the " poten- tial " temperature. The mean barometric pressures, therefore, of the tropical high stations give much more precise indications of the varia- tion of the air temperature, and thereby of the solar radiation, than the thermometer itself. In order to derive the full advantages of this method of measuring the air temperature by the barometer, the lower station, where the higher pressure is observed, must not be so far re- moved from the upper stratum that the relation dh=-dB (b : B) holds. Quito, therefore, would not be a good station for this purpose. A per- manent station on the Dodabetta Peak, in South India, on the con- trary would be very suitable. If the Indian Government would erect a first class observatory on the Dodabetta Peak, in the Nilgiri Hills, science would be much benefited. Such a station would aid meteor- ology greatly in other directions. Still better would be a permanent station on the Kamerun Peak, in West Africa, but the erection would present much greater difficulties than that on the Dodabetta Peak, which could be easily carried out. (The high station of Nuwara Eliya, 1,902 meters, in Ceylon, if only the barometer correction is ADDITIONAL STATIONS DESIRED. O sufficiently constant, I would already place in this category.) Even if the exact altitude above sea level of such a tropical station is un- known, still, by the introduction of an approximate value for h in the above formula, the variation of the lower air stratum can be cal- culated even if the mean temperature of the whole air stratum cannot. The greatest importance is to be attributed to the constancy of the barometric correction or to the accurate determination of any change therein. Short, but entirely homogeneous, series of pressure means can be used to determine the variations of the mean air temperature. II. — SHOULD THE PUBLICATION OF CLIMATIC DATA BE FOR PLACES OR DISTRICTS AS REPRESENTED BY PLACES ? Each observing system should publish, for a certain number of chosen stations, whose number corresponds to the size of the country, thrice-daily observations in extenso, and besides these, at certain prin- cipal stations, hourly observations, as is in fact done by most of the great European systems. Besides these, for as many stations as possil)le, the monthly and annual means should be published according to the international scheme, as has been done in the last reports of the Signal Service. Only in this way can the records of the meteorological stations be made useful generally, and the progress of the science toward effi- ciency be promoted. It is to be very much regretted that the observations are not pub- lished for many stations, which, from their positions, fill important gaps in our climatological and meteorological knowledge, whereby all the labor which has been given to making the observations is ren- dered useless. In other cases the' publication is in an entirely unsuitable form, so that the results cannot be used scientifically, or they appear only in local papers which do not reach the specialists. The installation of stations and the best equipment of them with instruments, their care and reading, are useless, if the results of the observations are not sufficiently made public. Economy in money in the publication of observations must be characterized as the greatest prodigality, since all the outlay expended on the station and the care given to reading the instruments are thus rendered useless. It is to be remembered that the worth of the meteorological data may be increased in a notable way, since for data which only go into the archives, the zeal and care diminish. The observer who sees his observations, or important extracts thereof, printed and distributed, will always try to make them correctly. Criticism of the observa- tions, and its beneficial influence on their value, will be greatly in- creased by their publication. In the most liberal form of publication of observations in any 6 CHICAGO METEOROLOGICAL CONGRESS. ' '^ meteorological system, as for example, that of the Central Physical Observatory at St. Petersburg, the cost of printing forms only a small percentage of the cost of the whole observing system, even when the labor of the observer is not considered. The permanent value of the activity of a meteorological system lies in its annual reports, and on these the greatest efforts should be concentrated. The annual reports of the various observing systems of the world form the evidences which seem destined to be laid before future generations as proofs of the pres- ent condition of the atmosphere over the earth's surface and for the study and progress of science. Therefore, we owe it to our successors to hand over to them yearly as detailed reports as possible of the mete- orological occurrences over the entire globe, in order that with the lapse of time they may be able to answer the question as to the secular variation of the meteorological elements. It is thus always better to publish too much than too little, since what is missed cannot be recovered, and avenges itself by retarding the progress of the science. The publication of meteorological means for whole districts has no value scientifically. It can, perhaps, for purely practical purposes be used to advantage, but for all scientific work such combined means are wholly unserviceable. It is unnecessary to insist on this, for anyone who has employed meteorological means and data in general for scientific work will agree with me. Neither the stations of a country nor of a district, the instruments and their exposure, nor the local influences at the various stations remain constant long enough to make the means for whole districts appear even tolerably comparable. The means for districts from different series of years are not com- parable with one another and can not be employed to show the changes of the meteorological elements with time. In general such meteorological means and data for whole districts should he confined strictly within the limits to which they belong. They are only to be employed as rough approximations, which, occasionally, may be very useful practically, but are unserviceable from a scientific standpoint. 2.— THE PUBLICATION OF DAILY WEATHER MAPS AND BULLETINS. Robert H. Scott. The subject which has been placed before me is one which hardly admits of any very decided treatment, inasmuch as the scale and character of the maps to be published in each country must depend firstly on the amount of money which can be appropriated to the service of preparation and issue of these maps, and secondly on the extent of area which the maps are intended to cover. PUBLICATION OF MAPS AND BULLETINS. 7 It seems to me to be out of place and useless to prescribe for any gentleman, at the head of a meteorological service, what he ought to publish ; of that he is a far better judge than any other person, or collection of persons, such as a congress possibly can be. And, as moreover, no congress can possess any executive power to enforce its resolutions, I fail to see the utility of proposing such. To take a single example. One of the oldest meteorological bulle- tins in Europe is the "Bulletin Meteorologique du Nord.'' This contains the observations from Denmark, Norway, and Sweden, but no maps of any description. The congress can hardly go so far as to recommend the three gentlemen under whose direction this publica- tion appears, to change its character and adopt the system, say, of the Weather Bureau at Washington. Is there the slightest probability that their respective governments would increase their annual allow- ances so as to render such a scheme practicable? I say nothing of other offices whose bulletins are even less full than that which I have cited as an instance. I shall, therefore, confine myself to an account of what the expe- rience of thirty-two years in the preparation of weather reports and of twenty-four years in their issue to the public has shown this office as being well suited to the requirements of the population of the British Islands, some two hundred copies being issued daily to sub- scribers, in addition to the free issue, as described in our annual reports. The daily weather report. — This consists of a large she^t of royal quarto size, which appears daily, and is accompanied monthly by a sheet containing corrections of occasional errors, and also reports which from any cause have arrived too late for insertion in the daily issue. The bound volume of these reports for the last six months of 1891 contains also tables of mean values of the most important ele- ments of the reports for a period of years — in most cases twenty, but in the case of rainfall for twenty-five years. The information given in the report is that received by telegraph, and it is conveyed by the use of the International Code, recommended for introduction by the Permanent Committee of the Vienna Congress at its meeting at Utrecht in 1874, and finally adopted by the congress of Rome at its fifth meeting, April 22, 1879. This code provides for the transmission in the morning telegrams of information sufficient for the preparation of two maps, one for the morning of the day on which the telegram is dispatched and one for the previous evening. The information conveyed in the telegram relates to pressure, tem- perature, humidity, wind direction and force, weather at the epoch of observation, amount, if any, of rain, or of snow (measured as water), and condition of the sea surface. (It need not be said that the last entry is blank for inland and for sheltered stations.) 8 CHICAGO METEOROLOGICAL CONGRESS. From these observations there are two charts prepared for 8 a. m., one showing the barometer, wind, and sea disturbance, (the wind by- arrows and the sea disturbance by hatching), the other showing the temperature by isotherms at 10° apart, and the rain in figures, where it exceeds 0.5 inch. Changes in pressure or temperature are printed in words across the face of the respective maps. The chart for the previous evening is not published by the office except in its weekly weather report, which will be described presently, but a copy is supplied to " The Times " newspaper, and appears in its morning issue of the following day, and so secures a very extensive circulation. A copy of the 8 a. m. chart is also forwarded to " The Times," and incorj)orated in the second edition, but the circulation of that edition is not very extensive. Both of these copies are prepared expressly for " The Times," and at the sole cost of that journal, which for more than thirty years, ever since meteorological telegraphy was organized by Admiral Fitz Roy in 1860, has been conspicuous by the prominence it has given in its columns to meteorological information. In fact, for some years, the entire service for the preparation of these 6 p. m. charts was car- ried on at the sole cost of " The Times," a fact which affords strong evidence of the public interest in weather intelligence evinced in this country. The weekly iveather report. — This was commenced in 1878 at the suggestion of eminent agricultural authorities, in order to supply for the different agricultural districts statements of the temperature and amount of rain for the week, and of their differences from their respective averages. In 1884 this report was materially improved by the insertion of figures illustrating the weekly march of cumulative temperature, that is, of the number of "day degrees" of temperature above or below 42° F. (approximately 6° C), which, according to the late Alphonse de Candolle, is the degree of temperature at which active vegetable growth may be assumed to commence. A popular explanation of this cumulative temperature will be found in a paper read by me before the International Health Commission in 1874. An explanation of the scientific principles on which the calculation of the values published weekly is based will be found in a paper by Lieut. Gen. R. Strachey, which appeared in the "Quarterly Weather Report" for 1878. At the present date, 1893, this report contains on the first page, for each of twelve districts : For temperature. — The average and the absolute maximum and minimum. The mean for the week, and its difference from the aver- age for the week. For accumulated heat. — The number of day degrees above and be- STATE WEATHER SERVICES. 9 low 42° F. for the week, and their respective differences from the mean, with similar information for the interval elapsed from the beginning of the current year to the last day in the report. For rain. — The number of wet days. The total fall for the week, and its difference from the average, and similar information, as be- fore, for the interval from the beginning of the year. For sunshine. — The number of hours recorded during the week, its percentage of the possible duration, and its difference from the aver- age, with similar data for the interval since the commencement of the year, and general remarks on the weather for the week. Page 2 gives information for each of the stations, as regards tem- perature, rain, and sunshine, with differences from averages for the week. Then follow weather maps for the whole of Europe as far eastward as Odessa, Moscow, and Archangel, giving, respectively, pressure and wind for 8 a. m. and for 6 p. m., and temperature and weather for 8 a. m. only. Remarks are given for each day, and the report concludes with a table of sunshine values for additional stations in the United Kingdom. Appendices have, in successive years, appeared in connection with the "Weekly Weather Report," and inter alia these have contained figures giving, for each of the districts into which these islands have been divided, the weekly and progressive values of the different ele- ments for each year as far back as 1879. The daily and weekly weather reports are accompanied by monthly summaries, giving, for calendar months, a brief summary of the weather over the United Kingdom. This is a brief account of the amount and character of the informa- tion which the experience of this office has led it to issue daily, weekly, and monthly, for the use of the public. 3.— FUNCTIONS OF STATE "WEATHER SERVICES. Major H. H. C. Duxwoody, U. S. A. State Weather Services are organizations for the collection and dissemination of climatological and other information. They depend almost wholly upon the voluntary co-operation of intelligent and public-spirited citizens, whose individual reports collected at the sev- eral central stations form the basis of their publications. These pub- lications are reviews of the prevailing weather conditions published monthly, and bulletins issued weekly during the season of planting, cultivating, and harvesting of crops, giving the more important weather features and their effect upon growing crops from week to 10 CHICAGO METEOROLOGICAL CONGRESS. week. Through State weather service organizations, the daily weather forecasts and special warnings of the National Bureau are distributed to large numbers of stations throughout the country. There are three independent lines of work, each dependent upon its special class of contributors who serve in the capacity of (1) me- teorological observers, taking observations of temperature, rainfall and miscellaneous data; (2) crop correspondents, who, during the crop season, render weekly reports of farming operations, the growth, maturing, and harvesting of crops, and the effects of the prevailing weather conditions thereon ; (3) the forecast displaymen, who display flags or sound whistle signals representing the weather forecasts of the National Weather Service. It not infrequently happens that one person serves in more than one capacity and sometimes co-operates in all the three distinct lines of work. In the United States there are less than 175 meteorological stations conducted by the regular paid observers of the Weather Bureau, or about one station for each 22,000 square miles of territory. The utter inadequacy of the data supplied by these stations for pur- poses of detailed investigation of special localities is therefore plainly apparent, making the State weather service an absolute necessity for the prosecution of such work. Although the work of collecting voluntary meteorological observa- tions and publishing the results was begun in Iowa as early as 1875, and in Missouri in 1878, the organization of State weather services for the active prosecution of work on the lines previously referred to may be said to have begun in 1881 and 1882, since which time the number of meteorological stations has steadily increased, there being now about 3,000 stations taking and recording meteorological obser- vations daily. With this extensive system it is possible to determine the special climatic features of every section of the country to an ^ extent that would be entirely impossible were it not for the existence of local weather services. All State weather services issue monthly reviews of the prevailing weather conditions, and many of these publications are issued in elaborate and attractive form, rendering them valuable and interest- ing. In many of these monthly reviews, besides giving a general dis- cussion of the daily temperature and precipitation, observations are published in detail. While it would be difficult to correctly estimate the great value of this particular line of State weather service work, a more popular feature is the weather-crop service. From the begin- ning of the crop season until its close, weekly reports of the weather conditions and the effects of the same upon farming operations, the growth of crops, etc., are collected at the several State weather service centers. These weather-crop reports are mailed by the correspondents 80 as to reach the central station on Tuesday morning, and, as far as STATE WEATHER SERVICES. 11 possible, cover the Aveek ending with Monday. Upon receipt they are carefully summarized and a brief discussion of the general con- ditions prepared, which, with the detailed reports from the several correspondents, forms the State crop bulletin. The official in charge of each State service on Tuesday morning sends a telegraphic sum- mary of the more important features of the week to the National Weather Bureau in Washington. The entire territory of the country being covered by local services, complete information as to weather and crop conditions is had from every section of the United States. These telegraphic reports are published in full in the National Weather-Crop Bulletin, and, with the charts of temperature and precipitation de^jartures, form the basis of a general discussion of the weather and crop conditions for the whole country. The charts of temperature and precipitation departures are pre- pared from the data collected principally from U.S. Weather Bureau stations and serve in a general way to show how the temperature and rainfall of each week compares with the normal of the corresponding period. This weather-crop service is, with the exception of the general weather forecasts, the most valuable work being done by the National Bureau, and is the most popular feature of State weather service work, being of greatest interest to agriculturists, although the bulletins are eagerly looked for by those interested in other pursuits. To the intelligent farmer it affords a means of supplying accurate and impor- tant information as to the condition of crops, enabling him to form reliable estimates as to supply and demand. In some States the edi- tions of the local weather-crop bulletin have already grown to very large proportions, and the demand for the bulletin is constantly increasing. More than 11,000 coj)ies of the Ohio weather-crop bul- letin are printed and distributed weekly. As an illustration of the importance of this work, it may be stated that a material change in the condition of the cotton crop in the State of Texas influences the cotton markets of the world ; and it is the work of the State weather service that presents weekly impartial and reliable information as to the actual weather and crop conditions prevailing throughout each season. The publicity given the State and National weather-crop bulletins through the press of the country is so extensive that an accurate esti- mate of the combined bulletin and newspaper circulation would be difficult of computation! The full text of the National bulletin, including the special telegraphic reports from the various States, is telegraphed each week by the press associations and printed on Wednesday in the large dailies. The agricultural press make a specialty of the bulletin, and some reproduce in their columns the 12 CHICAGO METEOROLOGICAL CONGRESS. charts of precipitation and temperature. The patent-sheet papers also find the bulletin an attractive item, and they extensively print the bulletins of the States covered by their circulation. The Missouri bulletin is printed in nearly one hundred patent-sheet papers issued by the Kellogg and Western newspaper companies. The late Prof. George H. Cook, for several years Director of the New Jersey Weather Service, in the work of organizing the New Jer- sey service, summarized the importance of the State service as fol- lows : It will be the means of soon securing better predictions of weather changes and storms. It will bring the benefits of the National Weather Bureau of the United States into every county participating in the State local organization. It will soon prepare the State for a system of storm signals displayed from railroad trains that will be widely beneficial to agricultural interests. It will give to every county the Government standards for temperature, rainfall, wind velocity, humidity, etc., which are sources of useful public information. It will put within I'each of local agricultural societies means of accurate observations which, in the course of years, must be valuable to any locality in the study and adaptation of cereals. It will bring the science and methods of the National Weather Bureau within the reach of the high schools of the State, offering teachers and pupils alike excellent opportunity to study a wide range of the application of science to foster and protect agricultural industry. . It will lead to the collection of rainfall statistics to enable engineers to better estimate the supply of canals, also the sudden downpours to guard against in laying out sewers in cities. It will lead to a correct knowledge of rainfall over the different watersheds of the State, for the purpose of giving data for supplying the water works of cities, towns, and villages. It will lead to the forming of reliable meteorological records for use in legal cases. It will lead to publishing the temperature of summer resorts, drawing attention of out- side parties to their dasirability as summer residence. It will lead to a better practice of medicine, when physicians throughout the State can study disease with reliable and accurate meteorological facts by their side — and for sanitary purposes correct meteorological statistics are invaluable to the practitioner in applying preventive remedies for the public good. The growth and popularity of these services were such that in November, 1885, Gen. W. B. Hazen, Chief Signal Officer, invited the directors of all State weather services to assemble in Washington for the purpose of mutual conference and discussion. Arrangements were accordingly made for a convention of the directors, which met February 24 and 25, 1886. At this conference many important sub- jects bearing upon State services were discussed looking to improved methods of taking and recording observations, and a general inter- change of views regarding State service work was had. Much good resulted from this conference, and a report of its proceedings was published with the Annual Report of the Chief Signal Officer. A second and more largely attended convention met in Rochester in August, 1892, at which the " American Association of State Weather Services " was formed, the constitution of which provides DROUGHTS IN INDIA. 13 for annual meetings, and the convention of 1893 will be held in Chicago in August during the time of the meeting of the Meteoro- logical Congress, August 21-24. During the past year there have been prepared by many State weather services, for exhibit at the World's Fair, valuable and inter- esting charts illustrating graphically the special climatic features of the several States. Some of these exhibits have been prepared at much expense of labor and considerable pecuniary cost, and have been very favorably commented upon. 4.— THE PREDICTION OF DROUGHTS IN INDIA. W. L. Dallas. The following gives an account of the method employed in India for the preparation of the seasonal forecasts issued by the India Meteorological Department, the chief object of which is to give warning of the probable occurrence of severe drought in any large area in India. In northern India there are two distinct periods of rainfall of importance for agricultural operations. The first is the period of the southwest monsoon rains from June to October. They are heaviest in the coast districts and at the foot of the Himalayas, and are most intermittent and irregular in the more interior districts of northern India. The second period is that of the cold weather rains from December to March, when light to moderate showers are received during the passage of feeble cyclonic storms across northern India. The chief causes of failure of crops in northern India are : 1st. Deficiency of rainfall, more especially in the southwest mon- soon period. 2d. Early termination of the southwest moilsoon rains. Under these circumstances the great rice crop in the parts of north- eastern India affected withers away and is a more or less complete failure. In northwestern India it prevents the cold weather crops being sown, except in low-lying or irrigated districts. In southern India, the Deccan, and Burmah, the only period of regular rains of value for the crops is that of the southwest mon- soon from May to November or December. In the Deccan and southern India it is moderate in May and June, light from July to September, and moderate to very heavy in October, November, and December, In these districts the rains may fail more or less completely during a part or whole of the period. The most serious partial failure is when the rainfall of the second maximum (October to December) is light and irregular. 14 CHICAGO METEOROLOGICAL CONGRESS. Hence, in northern India the most serious droughts are due to the combination of a more or less complete failure of the southwest monsoon rains followed by a failure of the cold weather rains. In this case both crops, the kharif and rabi, fail. In southern India failure of the crops and consequent famine is due to a more or less serious and large failure of the rains of a com- plete southwest monsoon period. The intensity of the scarcity or famine consequent on the failure of the crops under either of these conditions depends largely upon the character of the previous seasons. If the preceding two or three seasons have been unsatis- factory, so that the accumulated food stocks have been depleted, the famine may be of the most intense character. The preceding remarks have shown that the most important factor in determining the character of the crops is the rainfall of the south- west monsoon, and hence long period forecasts in India have been chiefly confined to the prevision of the southwest monsoon distribu- tion of rainfall. These forecasts are usually issued in the first week of June, and attempt to give a rough estimate of the general character of the rain- fall of the next four months in the larger provinces of India, and more especially to indicate any area in which there is a strong proba- bility the rainfall will be seriously below the normal, or to point out when there is a probability of unusual delay in the commencement of the rains or of their abnormally early termination in northern or central India. Rainfall in Europe occurs chiefly during the passage of cyclonic storms, and hence is apparently fortuitous in its occurrence. In India at least four-fifths of the rainfall occurs as a normal feature of the southwest monsoon circulation. The lower air currents of that circulation advance into India from the adjacent sea areas, determined by the regular periodic pressure and temperature changes in India and central Asia. The circulation is mainly maintained and continued by its internal energy, or rather by that of the energy set free on the condensation of the aqueous vapor brought up in it over India. It varies to some slight degree in intensity from year to year, and its extension also varies in different years, dependent upon the antecedent meteorological conditions. It is this fact, that the rainfall of this period is due to the preva- lence of a massive and steady current, and not to local cyclonic dis- turbances in a region of irregular winds, that makes it probable long prevision can be successfully attempted and carried out in India. In order that the attempt to forecast the character and distribution of the monsoon rainfall from the meteorological conditions prevail- ing anterior to the advance of the rain giving southwest monsoon DROUGHTS IN INDIA. 16 currents, it is essential that there should be uniform and direct rela- tions between the former as results and the latter as conditions. It is immaterial for the purposes of forecasting, whether they are based upon experience or upon theory. It is most satisfactory, of course, that relations emperically obtained should be proved to be in strict accordance with a rational theory. The following gives a statement of some of the more important uniformities or relations utilized in preparing the long period fore- casts in India : A most important feature is that the general character of the dis- tribution of the rainfall during the southwest monsoon is fairly con- stant during the whole period, and hence that an area of largely defi- cient rainfall has usually deficient rainfall throughout the whole season. Similarly for excessive rainfall. The annual reports of the meteorology of India give numerous examples of the persistency of the seasonal characteristics throughout the whole monsoon period. It will suffice to give one example. The southwest monsoon of 1890 gave abundant rain to northern and central India and the north Deccan, and as usually happens when the humid currents are more largely determined to northern India than usual, the rainfall of the same season was in defect in Burmah and southern India. The fol- lowing gives data : Percentage variation of rainfall from normal. District. Areas of excessive rainfall: Orissa Assam and east Bengal Lower Bengal Bihar Northwestern Provinces and Oudh Punjab Central Provinces Hyderabad Konkan Areas of decreased rainfall: Mysore Carnatic Arakan Pegu Tenasserim Upper Burmah 1890. June. July. Aug. Sept. Total for period. + 33 4- 28 4- 22 + 66 -j-IIO + 33 + 43 -f- 20 — 19 — 15 — 19 — 16 — 6 — 41 tlolt + 10 + 65 + 45 4- 28 + 9 4- 10 I 4- 27 i — 12 — 2 4-24 + 10 — 9 — 39 + 31 — 8 4- 35 — 3 — I — 27 — 20 — 10 — 27 — 30 4- 16 — 35 — 10 4- 14 — 73 .. 24 1.5 — 37 — 4 — 49 — 24 — 21 — 17 4- II ¥ 4- 34 + 28 4- 15 nil. 6 X Hence, the steady tendency to increased rainfall in the former areas was as strongly marked as the large deficiency in the latter areas throughout the whole season. The above example is very interesting on one account, as it shows persistent opposite tendencies and variations in areas of which the meteorological relations to the monsoon currents are more or less opposed or inverse to each other. The persistent variations in the distribution of the monsoon rain- 16 CHICAGO METEOROLOGICAL CONGRESS. fall are related to persistent variations in the strength and extension and other characteristics of the great currents of the period. It will suffice to give one case. The monsoon rainfall was very largely in excess in Burmah in 1891. The following table gives the deflection of the mean winds at three representative stations in that area during each month of the season : Westerly deflection, 1891. station. June. July. Aug. Sept. Port Blair o + 25 -j- 25 4- 20 o + 15 + 8 + 28 + i8 + 3 + 12 + 25 + 29 + 36 The winds at these stations during the southwest monsoon are from directions between south and west, and increased westing ardently indicates a greater determination of the Bay monsoon cur- rent to Burmah and Tenasserim than usual. Again, the monsoon currents were both stronger than usual in 1892 during the period July to September. The following data will show that the increased strength was marked throughout the whole of the period, more especially in the case of the strongest current in that year, viz., the Bengal current : Percentage variation of strength. Name of current. Bengal . . Bombay . June. + 30 — 30 July. + 27 + 7 Aug. Sept. + 15 + 10 + 32 + 15 The relations of the variations of the strength and direction of the lower air currents during the southwest monsoon to the rainfall vari- ations require further investigation, but sufficient data have already been accumulated to establish that there are marked differences in the strength and extension of the monsoon currents and in the dis- tribution of the rainfall from year to year, and that these are directly related to each other. These relations might have been inferred from the fact that the monsoon rainfall is not due to the passage of cyclonic storms, but to the continued prevalence of a steady, strong current charged with vast supplies of aqueous vapor. Assuming that the character of the dis- tribution of the rainfall is fairly persistent throughout each season, and that the rainfall is due to the advance and prevalence of a strong sea current into the Indian land area, it is evident that the extension of this current will be to some degree deteiwnined by any abnormal meteorological conditions present before or during its advance. The following gives a brief statement of some of these determining conditions : DROUGHTS IN INDIA. 17 (1) Unusually heavy and prolonged snowfall in the Himalayan Mountain area has been shown by Mr. Blanford to exercise a very powerful influence. It modifies the pressure and temperature con- ditions in Qorthern India, and usually not only retards the com- mencement of the monsoon but modifies its intensity. The manner in which snowfall modifies the hot weather conditions and the sub- sequent rains has been investigated and is fairly well known. Ab- normally deficient snowfall and its usual correlative, more intense hot weather conditions than usual, on the other hand are found to precede almost invariably stronger and steadier monsoon than usual. (2) The abnormal pressure conditions established during the hot weather, more especially if they are marked, exercise a large influ- ence in modifying the set of the monsoon currents. The general rule in India is that the hot weather tends to exaggerate and develop local pecularities of pressure, and the rains to smooth them away. Thus, if the hot weather develop a local deficiency of pressure in any area it tends to become a sink to which the monsoon current is more largely directed than usual, and hence also affects the rainfall in neighboring districts. If, on the other hand, a local excess of pres- sure is formed, as occasionally happens in Guzerat, northwest Rajpu- tana, etc., it usually accompanies a considerable or large diminution of the rainfall in Rajputana or northwestern India. Much remains to be done to work out fully the influence exerted by high and low abnormal pressure areas in modifying the distribution of the mon- soon rainfall, but several useful relations have been established and are used in drawing up these long-period forecasts. Similarly, the consideration of the temperature conditions of India during the hot weather throws light on the causes of the general and local pressure conditions obtaining before the setting in of the mon- soon, and hence enables their probable importance to be estimated. An important point to be taken into consideration is the relative strength of the two currents, as upon this depends largely the posi- tion of the monsoon trough of low pressure, and hence also the mean tracks of the cyclonic storms of the rains and of the heavy rainfall that accompanies these storms. A strong Bombay monsoon tends to displace it northward and a strong Bengal monsoon southward. Another important point is based on the results of Mr. Blanford's investigations (given in the "Rainfall of India") of the relations between the rainfall variations in different parts of India. He has worked out very fully the areas in which the rainfall variations are usually similar or opposite in character, and the measure of the prob- ability of similar or opposite variations occurring for any given year. The previous gives a few of the more important principles and facts upon which the forecasts of the distribution of the monsoon rainfall are based, 2 18 CHICAGO METEOROLOGICAL CONGRESS. A consideration of the snowfall data of the cold weather, of the meteorological conditions prevailing during the hot weather, and more especially the character and persistency of the pressure varia- tions, usually enables a rough estimate of the general strength of the monsoon currents and the distribution of the rainfall to be made. This is first done and afterwards a comparison is made with previous years in which similar conditions are known to have obtained. By taking into consideration the actual conditions, the relations estab- lished by Mr. Blanford between the rainfall variations in different areas, and the rainfall distribution of previous years of similar me- teorological conditions, not only the probable character of the rain- fall can be estimated, but also the probability of the occurrence of deficiency or excess of rainfall in any area as dependent upon or resulting from these conditions. This is what is now attempted to be done in the forecasts issued annually in June by the department, and which have had a fair measure of success. For example, a full warning was given in June, 1891, of the drought in Rajputana dur- ing the monsoon rains of that year. It is hardly necessary to point out that the methods employed and sketched above are practically identical with those employed in giv- ing warning of the approach of storms, and I may again point out that these long-period forecasts in India are rendered possible by the peculiar features of the southwest monsoon air motion over India, and by the remarkable persistency of many of the abnormal condi- tions of the meteorology of that current. 5.— CAN WE BY AUTOMATIC RECORDS AT THREE SELECTED STATIONS DETERMINE THE ENERGY OF A FLASH OF LIG-HT- NING? Alexander McAdie, M. A. I may begin this paper with an answer in the affirmative. It would be a good plan to have these observations made. The lightning flash has been regarded up to the present time as a thing accomplished, a discharge between the electrified cloud and the earth, over about as soon as seen. It must be a discharge of very high potential because of the length of the spark ; and the potential being great the capacity may be small, if, as we have some reason to suppose, the quantity of electricity in a flash is not great. CV=z Q. To-day we are beginning to look at a lightning flash from a differ- ent point of view. We study the strain in the dielectric, where pre- viously we thought only of the surface electrification ; and the char- acter of the discharge is now of great importance, and where before we talked of forked, zigzag, and sheet lightning, a classification some- what like Luke Howard's cloud classification, we talk now of "ini^ ENERGY OF A LIGHTNING FLASH. 19 pulsive rush" discharges, meandering flashes, etc. What we need, and we have in part, is a systematic classification of the electri- cal discharges in the atmosphere. At one end of the list we might place the impulsive rush discharge, a most intense flash, and at the other the gentle glow discharge which we find so frequently on Pikes Peak and Ben Nevis, and now definitely connect with certain meteorological conditions. Observe, too, that the conditions for the protection of life and property are very different for these different types of discharge. Points fail to be effective under the impulsive rush, while most effective with the glow. We want, then, to classify our flashes ; and to get more accurately at the character of the flash, perhaps we should attempt to get at the energy of each particular flash. Dr. Lodge, in his book on "Light- ning Rods," in Chapter xv, gives the suggestion of the editor of the " Electrician " that, where thunderstorms are frequent and violent, it might be possible to set up lightning conductors for experimental purposes, and thus accumulate experience concerning their behavior more rapidly than at present. On a preceding page it is also noted how much work could be done at meteorological stations and obser- vatories " in the matter of accurately observing and recording light- ning, photographic records, obtained by proper appliances for distin- guishing multiple from successive flashes, being, of course, superior to all others. An experimental lightning conductor on a flagstaff near every meteorological observatory would also be a most desirable addition. It need not be associated with danger. A system of fuses or cut-outs, or an east or west steel bar, might be used to record the passage of a flash, and the rod need not be examined until after the cessation of violent disturbances. By having the conductor of dif- ferent thickness at different parts one could learn what size is really likely to be melted. One could also arrange so as to gain informa- tion about side flashes." In the " Philosophical Magazine," August, 1888, Dr. Lodge applies the mathematical expressions for the real resistance and inductance of a conductor under an alternating cur- rent to the case of a lightning flash. "An air-condenser with plates of any size separated by a distance /) (height of cloud) and charged up to bursting strain (^ gramme weight per square centimeter; the less strength of rare air is hardly worth bothering about). Let a small portion of this condenser, of area -6^, now discharge itself, being separated from the rest after the trap-door and guard-ring manner. A volume of dielectric T^h'h is relieved of strain, and the 981 energy of the spark is Ez=-^ T^Vh ergs. The capacity discharged is 5= -j-^--, and the maximum potential can be put at 110 /i electrostatic units." He then calculates the 20 CHICAGO METEOROLOGICAL CONGRESS. inductance of the circuit L = h (fJ^u^-{- 1\), where u may be a number not very different from 4 or 5, and now knowing S and L proceeds to find the criterion for the discharge to be oscillatory and to deter- mine the rate of alternation. " The discharge will be oscillatory unless the resistance it meets with exceeds a certain critical value, viz. : P _ ITL ___ /4 h p. u" _ 4:hfj.u _4hu;jLV <=^'^=4 s ~\ Kb' ~h\n^ 1 . 30 where v=z , -, — ^^^ •=. the velocity of light =: — w{iJ.K) ^ ^ II 80 the critical resistance is ims. ^0=120^^/(2 log^-l)ohi Suppose /i to be a mile (1,609 meters), h 50 meters, and a a milli- meter; the critical resistance comes out about 15,000 ohms. When the resistance then falls below this the discharge will be oscillatory. The impedance to a condenser discharge comes out impedance = 60 , -i/( 2 log — 1 ) ohms. Or, it is half the critical resistance ; it depends almost entirely upon the amount of space magnetized round it ; and upon the capacity of the discharging condenser. Magnetic permeability, specific resist- ance, or even the thickness of the conductor, hardly matter. The length of the conductor does figure. Now, while we may not erect a conductor a mile high, it is feasible by kites, balloons, or aeroplanes to carry up a wire a millimeter thick some 200 meters. The critical resistance would come out something like 2,000 ohms and the impedance one-half of this, and the frequency constant, n L=. impedance, something like 3,000,000. Now, the total maximum energy " of a given area of cloud is easily estimated," says Lodge, " by remembering that as soon as the electric tension of the air reaches the limit of about one-half gramme weight per square centimeter disruption occurs ; and the energy of the dielec- 981 trie per cubic centimeter being —^ ergs, per cubic mile it would be 4.110 X 10" , 2 X 3 X 10'' tons, equal to 70,000.000 foot tons. The energy of any ordinary flash can be accounted for by the discharge of a very small portion of charged cloud, for an area of 10 yards square at a height of a mile would give a discharge of over 2,000 foot tons of energy." And for the case we have taken, some 200 meters, we should have from 200 to 300 foot tons, or very roughly in the neighborhood of 1,000 horse power. With three stations grouped then around a common center, pro- vided with cameras with some type of electrometer and with meteoro- CLOUDS AND WEATHER PREDICTION. 21 logical apparatus, we might get first the exact times of occurrence of all visible discharges ; and the exact appearance of the flashes, i. e., not as referred to one plane which a single camera would give, but the character and direction of the flash in space. Many flashes starting from a given point undoubtedly meander, turn and twist upon them- selves, and some of the seeming thickenings in single photographs are doubtless points simply of change of direction of flash. Next we would get from the potential fluctuations, as shown on the electrometer records, the exact times and something of the individual strains, and, as I have elsewhere shown, evidences of discharges not visible, and in this way could, from a composite of the records of our three stations, get at a very good approximation of the strains to which our dielectric, the air between the thundercloud and ground, had been subjected ; and like a piece of plate armor, when the firing is over, we could examine and locate the places and times of rupture. 6.— THE UTILIZATION OF CLOUD OBSERVATIONS IN LOCAL AND G-ENERAL WEATHER PREDICTIONS. Alexander McAdie, M. A. In our daily work of forecasting weather changes, we have reached the point where we feel the necessity of some knowledge of the con- ditions of the upper air strata. We map with great success the condi- tions of the bottom of the aerial ocean in which we live. By the aid of the telegraph we make invaluable synoptic charts. We have ex- cellent ground plans or horizontal sections, but we attempt nothing in the way of vertical sections of the atmosphere. The telegraph is not available ; some other agency must be sought for. We, in part, att'empt the exploration of the free air by balloons and by mountain observatories, and when aerial navigation is an accomplished fact we shall doubtless have systematic and extensive surveys of the atmos- phere. But until that happy time arrives, clouds must remain the best exponents of conditions prevailing at different levels in the atmosphere. They can be made to give us even now, with most crude methods, information concerning the currents at different heights, and indirectly, temperature and moisture conditions. Studied closely and in connection with the surface isobars, isotherms, and winds, the forecaster will find in cloud motions and formations portions of the storm mechanism otherwise hidden from him. For special as well as general forecasting cloud study is important, and I desire to em- phasize the need of cloud study at places along the coast. I think that if we had well equipped stations at Capes Fear, Lookout, and Hatteras, with cloud conditions a subject of special attention, we would receive timely warning of the occasional storms that slip in upon us from the seaboard. 22 CHICAGO METEOROLOGICAL CONGRESS. Cloud nomenclature and the various methods of cloud measure- ment do not fall strictly within the limits of this paper. Both topics require special papers. But for the purposes of general forecasting we need, first, a codification of what for want of a name I shall call "cloud laws", i. e., the results of studies of cloud formation and movement; and secondly, some cipher scheme at once flexible and definite that will convey to a distance the actual aspect of the sky. Hildebrandsson in his paper (read before the Royal Meteorological Society, London, February 16, 1887) divides the problem into two sections — how to best study the relation of formation to the physical processes at work ; and then the determination of the bearing of these on weather changes. In a footnote he instances the great value and interest a series of cloud observations would have if made hj a society of persons specially interested in cloud studies and observing systematically over a large area of country, "keeping strictly to the same detailed nomenclature, e. g., that of Clement Ley." There can be no question that forecasting would be more certain if we could connect certain types of cloud formation with certain conditions of atmospheric circulation. It being impossible to get the series of observations of the character referred to, I thought that a rough approximation might he made by carefully charting cloud observations made simultaneously by the observers of the Weather Bureau. The classification is that of Luke Howard, and I can only repeat here the remark made in the discussion of Captain Toynbee's paper on cloud names, by Clement Ley, viz. : " Before the dawn of synoptic meteorology, Luke Howard's system filled a need, though it did little to promote inquiry. Since that era it may safely be made the basis of a carefully discriminating and eclectic system of termi- nology. But any endeavor to restrict ourselves to its use cuts off the possibility of obtaining what becomes more and more necessary, viz., the power of either communicating from distant localities the actual aspect of the sky so that this may be represented graphically or of recording such an aspect, so as to call up in the mind a vivid idea of the observed phenomena ; I believe that ten thousand years of observations conducted on Luke Howard's system would give us an absolutely futile record." The language is a little strong, but there is some justification for it. However, it is not altogether an easy task to devise a classification so detailed as to definitely picture up any one of the numerous and often not easily definable sky aspects. Taking, then, the observations of the Weather Bureau observers, charts were made in the Forecast Room each morning and night, and prove first that it is entirely practicable to construct such cloud maps within the time allotted, and, second, that we can make use of the same in forecasting. The particular point which these bring out is that it is possible to fix with considerable accuracy the storm CLOUDS AND WEATHER PREDICTION. 23 center. We need, however, the velocities of cloud motion as well as the directions. And even in getting direction there is room for great improvement. It should be instrumental, and not, as now, a matter of eye observation. The surface wind is represented by an arrow flying with the wind below the station, the cloud directions by arrows above the station. The velocities could easily be indicated by barbs in the tail of the arrow. Where two or more types of clouds are reported, the uppermost arrow represents the uppermost cloud. I then employed the simple scheme of prolonging the arrow heads of all lower directions and the arrow tails of all upper directions, assum- ing that in this way we can get at not only the general center of gyratory motion, but if sufficient observations are at hand, the ten- dency to the formation of any secondary center of gyratory motion. For general forecasting, therefore, I give it as my opinion, from this practical test, that cloud observations can be used to great advantage. In special forecasting there can be no doubt that clouds should go hand in hand with pressure, temperature, and humidity studies. We should have self-recording nephoscopes, and the diur- nal curves directly considered in their relation to the barometer, thermometer, and h3'^groscope curves. To take the single case of temperature, every forecaster knows that any prediction as to tem- perature will depend somewhat upon the cloudiness. It is certainly marked in minimum and maximum temperatures. The amplitude of the daily temperature oscillation will be modified by the condition of cloudiness. Lamont,' E. Quetelet,^ Rykatschef,' Jesse, and Angot have shown for Munich, Brussels, Saint Petersburg, Hamburg, and Paris that the daily amplitude is much greater on clear days than on cloudy days. It seemed to me worth while to practically test this, so I have taken from my paper on " Temperature Corrections " the mean amplitudes, based on some twelve years' observations, and charted with them the mean daily cloudiness for a similar period. The tables show that in the United States the greatest amplitudes are found with the least cloudiness, as was to have been expected. For example, at Win- nemucca, El Paso, and Yuma, where, on a scale of 10, the mean annual cloudiness is 3 or less, the values of the amplitude approach 25° F. (13.9° C); and on the other hand, at Toledo, Cleveland, or Eastport the cloudiness is much greater, about 5, the mean ampli- tudes are much smaller, about 12° F. (6.7° C). ^Darstellung der Temp.-Verhaltnisse, etc. *Memoire sur la Temp., etc. ' La marche diurne de la Temp. 24 CHICAGO METEOROLOGICAL CONGRESS. Temperature amplitudes and mean cloudiness. Station. 19. Winnemucca, Nev.: OF OC Clouds I 4 Yuma, Ariz.: OF OC Clouds Washington, D.C.: OF OC Clouds Philadelphia, Pa.: OF OC Clouds Salt Lake City, Utah op ° c'.'.'.'.'.'.'.'.'.'.'.'.'.'.. Clouds Saint Louis, Mo.: op °c'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. Clouds New Orleans, La.: OF OC Clouds Memphis, Tenn.: °C. '.'.'.'.'.'.'.'.'.'.'.'.'.'. Clouds Santa Fe,N.Mex.: OF OC Clouds Buffalo, N.Y.: op ° c'.'.'.'.'.'.'.'.'.'.'.'.'..'. Clouds Montgomery, Ala.: OF OC Clouds San Diego, Cal.: op OC Clouds San Francisco, Cal.: ''F OC Clouds Denver, Colo.: OF OC Clouds Atlanta, Ga.: op OC Clouds El Paso, Tex.: op OC Clouds Milwaukee, Wis.: OF OC Clouds Cheyenne, Wyo.: op OC Clouds Savannah, Ga.: °F OC Clouds Chicago, 111.: op OC Clouds 3-8 17.8 9.9 4.6 21.6 II. 4 3.8 23.6 13-1 2.2 2.2 10.8 6.0 5-6 8.0 4.4 5-2 10. 1 5-6 5-4 9.8 5-4 5-3 9.6 5-3 5-0 10. o .S.6 5-7 17.0 9.4 3-7 4.8 2.7 6.6 12.7 7-1 5-5 II. 7 6.5 5-4 10. o 5-6 5-5 13-4 7-4 5-0 11.6 6.4 5-4 6.2 4.9 11.8 6.6 5-1 19.4 10.8 3-6 5-7 3-2 6.4 14.4 8.0 4-7 12.4 I II. I 6.9 I 6.2 4. 1 I 4.8 7.2 j 8.0 4.0 1 4.4 4.6 I 4.6 16.0 8.9 ; 9 16.8 3 3-5 ! 1 10.8 i 6.0 i 5-3 1 23-3 12.9 3-0 18.8 10.4 6 7.2 7 4.0 5-8 6 13-4 7-4 5 3-5 12. 1 I 6.7 4.8 8 7.8 8 4-3 7 5-5 12.6 7.0 4.6 24.6 13-7 2.7 7-4 4.1 6.0 l6.8 9-3 4.2 13-2 7-3 4-3 7-7 4-3 5-8 >. 0, < s * 21.0 23-4 II. 7 13.0 4.2 3-9 28.2 27.6 is.b 15-3 1.6 1.2 14.7 15-2 8.2 8.4 5-3 5-0 12.6 I.V6 7.0 7.6 5-3 4.8 14.0 I,V6 7.8 8.7 5-2 4-5 13-4 13-2 7-4 7-3 5-0 4.9 10.4 10.8 5-8 4.8 12.4 6.9 4-7 17.4 9-7 4-1 7-9 4.4 5-5 16.2 9.0 4.6 10.4 5-8 4.6 4.8 4.2 18.8 10.4 4.9 14-3 7-9 4-5 26.2 14-5 2-3 4.6 5-6 17.9 9.9 4.9 II. 9 6.6 7-5 4.2 5-2 6.0 4-8 14.2 7-9 4.6 25-8 14-3 3-2 28.3 15-7 0.8 14.7 8.2 4.9 13.0 7.2 4-7 17-7 9.8 3-2 13.0 7.2 50 8.4 4-7 4-5 12.6 7.0 4-5 19-5 10.8 3-8 22.0 12.2 3-3 20.0 II. I 4.8 9.0 5-0 5-2 8.1 4-5 4.8 8.2 4.6 3-6 15-4 8.6 4.4 14.7 8.2 5-1 14.4 8.0 4.9 9.8 5-4 5-4 9.4 5-2 5-1 9-5 5-3 4-7 9.4 5-2 4.0 9-5 5-3 4.0 10. 1 4.6 19.6 10.9 4.9 22.8 12.7 3-7 22.8 12.7 4.2 12.8 7-1 4.6 12. 1 6.7 5-2 12.2 6.8 4.6 26.6 14.8 2.4 27.6 15-3 2.8 25.0 13-9 3-7 7.6 4.2 5-0 7.8 4-3 5-0 9.6 5-3 4.4 20.7 "•5 5-1 23-8 13-2 3-9 24.2 13-4 3-9 II. 4 6-3 4.2 6-3 4.9 10.8 6.0 4.8 7.0 3-9 4-7 7.6 4.2 4.9 8.8 4.9 3-9 29.8 16.5 1-7 24.0 13-3 1-7 14.4 8.0 4.6 12.8 7-1 4.8 19.6 10.9 3-0 14. 1 7.8 4.2 9.0 5-0 4-8 13.6 7.6 4.2 33-8 3I' 18.8 17.3 1.4 I 1.9 24.2 j 24.8 13-4 ! 13-8 2.2 14.8 14. 8.2 8.2 4.9 4.7 12. 1 6.7 4-7 18.4 10.2 3-1 14.0 7.8 3-8 7.6 4.2 4.6 13-8 7-7 4.0 18.2 10. 1 4-7 12.0 6.7 4.6 18.4 14.8 9.2 5-1 4-5 14.2 7-9 4.0 18.7 10.4 3-0 10.3 9.9 5-7 I 5-5 4.4 5.0 14-9 8-3 4.9 15-7 8.7 4-,S 9.9 , 10.5 5-5 I 5-8 4.0 3.8 5-7 4-3 1U.7 5-9 3-4 22.1 12.3 4.2 24.2 13-4 3-0 12.7 7-1 5-0 13-4 7-4 4-3 23.8 13-2 3-5 24.1 13-4 2.9 9-7 5-4 4.6 10.9 6.1 4.9 23.6 3-8 24.4 13-5 3.2 9.8 5-4 5-0 6-3 4.8 9.0 10.2 5-0 3-9 5-7 4.3 27.2 22.8 15. I ! 12.7 2.6 j 3.6 24.6 13-7 15-1 8.4 4-7 6.2 4.6 14.0 7.8 3-7 13- 2 7-3 3-8 9.6 5-3 3-9 14.2 7-9 3-8 19.0 10.6 2.4 7-3 4.1 6.0 15-9 8.8 4.1 II. 2 6.2 11.9 6.6 3-9 3-5 10.2 8.0 5-7 3-2 4.4 3-8 20.6 18.4 11.4 10.2 3-5 3-3 13-6 7.6 4.2 12.4 6.9 4.6 25-6 14.2 2-5 23-8 13-2 3-1 8.4 4-7 5-5 6.7 3-7 6-3 19.2 10.7 3-7 15-6 8.7 3-6 12.0 6.7 12.2 6.8 4.0 4-5 8.8 4.9 5-0 7-3 4.1 5-8 CLOUDS AND WEATHER PREDICTION. 25 No paper upon cloud work would be complete without reference to the work of Ekholm, Hagstrom, and Hildebrandsson in putting before us the question of cloud measurements. And I must not omit ref- erence to the law of relative directions of lower and upper currents as announced by Ley — high currents coming from a direction to the right of the lower currents, and the higher up the more marked this twist. Or in Ferrel's words "The higher currents of the atmosphere while moving commonly Avith the highest pressures, in a general way on the right of their course, yet manifest a distinct centrifugal ten- dency over the areas of low pressure and a centripetal over those of high." It is also not out of place to mention briefly the more prom- inent of the proposed cloud systems, viz., Luke Howard's, the essay read before the Askesian Society, 1802-1803 ; Clement Ley's observa- tions ; Abercromby and Hildebrandsson's ; Wilson-Barker's ; Aber- cromby's ; Hildebrandsson and Neumayer's ; Dr. Carl Singer's ; Kop- pen and Neumayer's ; Dr. Vettin's table of average altitudes, and the work at Blue Hill in this country. As a matter of perhaps more literary than scientific value, I append a list of English cloud desig- nations. List of English cloud designations. Alto-cirrus, alto-cumulus. Ark o' the cluds. Auroral clouds. Balefrae — bale fire. Ball clouds, bally. Banner, banneret. Bise. Buddha's rays. Catstails. Cirrus, cirro-cumulus, cirro- filum, cirro-nebula, cirro- haze, cirro - stratus, cirro- stripes, cirro-velum. Cloud, cloud area, cloud bank, cloud ring, cloud ship, cloud wrack, cloud wreath, cloud wraith. Cormizant. Corposant. Coronfe. Cumulus, cumulo-cirrus, cu- mulo-nimbus, cumulo- stratus. Dapple sky. Dark segment (auroral). Diablaton. False cirrus. Festooned, festooned cumulo- cirrus, festooned cumulus, festooned stratus. Filly tails. Fireballs. Fog bow. Fracto - cumulus, fracto- nimbus. Funnel-shape. Globo-cumulus. Goats hair. Helm-bar. Henscat. Iridescent. Leeside. Luminous. Mackerel sky, mackerel scales, mackerel back. Mammato-cumulus. Mary's ship. Mare's tails. Merry dancers (auroral). Nacreous. Nightcap. Nimbus. Noah's ark. Nimbo - pallium, nimbo- stratus. Packet boys. Pallio-stratus. Pallium. Pocky cloud. Prophet cloud. Plague cloud. Polar bands. Rain balls, rain clouds, rainbow. Radiation fog. Rime cloud. Rocky. Roll cumulus. Salmon. Scud. Scotch mist. Saint GJara's fire. Saint Elmo's fire. Snow banners. Spindrift. Storm cloud. Snow cloud. Spectre of Brocken. Stratus, strato -cirrus, strato-cumulus. Tablecloth. Thunder heads, thunder- squall clouds. Turreted cumulus. Tornado. Unraveled. Watery sky. Weather lights. Woolly heads. Wulst cumulus. Wool bags. Wrack. Wraith. 26 CHICAGO METEOROLOGICAL CONGRESS. 7.— AN INTERNATIONAL CIPHER CODE FOR CORRESPOND- ENCE RESPECTING THE AURORA AND RELATED CON- DITIONS. Dr. M. AJ Veedeb. It is presumed that the assignment of this subject to the writer is intended to call for the results of the experience which he has had in attempting to secure concerted observations of the aurora. The adoption of a special plan of observation or code correspondence respecting such a phenomenon as the aurora presupposes the selection of the points thought to be most important in order that they may- be made the subject of special observation and record for purposes of interchange and comparison. The purpose in view in any such case determines the character of the record to be made. If the plan involves nothing more than the preservation of memoranda, such as may happen to be secured incidentally in the ordinary course of meteoro- logical observation, and without reference to the requirements of serious study, it is scarcely worth while to discuss the subject at any great length or offer many suggestions. All that can be expected, if nothing more than this is to be attempted, is the recording of dates and localities with perhaps some items of description more or less condensed, it may be, by the aid of the sys- tems of classification already in ordinary use which have reference to the presence or absence of arches, streamers, auroral waves, the corona, and the like. Still, the gathering into suitable records and making accessible information not more complete than this, has iieen the means of affording a knowledge of certain broad features. The rela- tive prevalence of the aurora in different years and its conformity to the records oFsun spots and magnetic storms has thus been shown, as has also the predominance of auroras near the equinoxes, and at intervals of about twenty-seven days, corresponding to the time of a synodic rotation of the sun. By such means also the distribution of the aurora in belts surrounding the magnetic poles has become known. If so much is to be learned by the aid of observations that have been for the most part little better than merely desultory, what might not be expected from the elevation of the subject into a special depart- ment of research to be undertaken formally and of set purpose? In the paper on the " Periodic and Non-periodic Fluctuations in Latitude of Storm Tracks," presented by the writer in the Section of Marine Meteorology of this Congress, it is shown that important relations to meteorology may be involved in the operation of the forces concerned in the production of the aurora. This being the case, its behavior is as worthy of careful record as is temperature, pressure, or any other meteorological element. The experience which the writer has had in this regard has had INTERNATIONAL CIPHER AND AURORAS. 27 reference more particularly to methods of recording observations, and not to any system of code correspondence based thereon. A specimen of the forms which he has employed for securing such records is appended to this paper. The points upon which the greatest possible stress is laid are the giving of the times of observa- tions and of all prominent features, and the noting specifically of verifications of the absence of the aurora as well as its presence, and the recording of frequent estimates of the extent of sky covered. By the aid of such data it becomes possible to attack the questions as to geographical distribution, altitude, coincidence with magnetic per- turbations, and the like, positively and directly, and not remotely and inferentially. Some of the results of this system of observation are indicated in the paper on Storm Tracks, to which reference has been made, and in other notes and articles of similar tenor, and do not need to be rehearsed in the present connection. Suffice it to say that the observations recorded in this precise way are proving to be extremely valuable. As regards the general descriptions to be given in connection with these observations, it is found that great freedom and fullness in giv- ing details are very desirable. Not unfrequently items of description that would be omitted in a code system of abbreviating and summar- izing prove to be of the very highest interest. Further experience is required before it can be fully known what points are of such imme- diate and practical interest as to justify or require the adoption of so elaborate an arrangement as an international cipher code for their communication. Still, there are indications that something in this line is worth attempting, and that the time is surely coming when a system of correspondence having reference to the whole range of phe- nomena of which the aurora is the visible expression will be well nigh indispensable for purposes of weather predictions as well as the advancement of general scientific research. It will not be advisable, perhaps, to be too urgent in attempting to bring about such an ar- rangement prematurely. Not until the facts and principles involved are fully appreciated and recognized by the scientific world generally will the demand for the adoption of an international code system become so emphatic that it can not be disregarded. The question now is as to the best means of arousing such lively interest most rapidly and effectually. It will contribute somewhat to this end, perhaps, and compel attention to the merits of the case, to describe briefly what would be an ideal system of inter-communi- cation at the present stage of progress of the research respecting the aurora and related conditions. If there could be brought together upon daily synoptic charts, along with other meteorological data which it is now customary to present in this way, information also in respect to all auroras seen over as 28 CHICAGO METEOROLOGICAL CONGRESS. wide an area as possible, and likewise some indication of the extent of prevalence of thunderstorms, together with notes from the mag- netic observatories as to the times and extent of any perturbations recorded, and information also as to the geographical distribution of any earth-currents that may have been felt on the telegraph lines, and in addition, some description of the coincident solar conditions on which this class of phenomena evidently depends, any characteris- tic relations to intensification of storms or changes in the distribu- tion of atmospheric pressure would soon become apparent. Such an arrangement would require simply an extension of the telegraphic code system now in ordinary use for the communication of meteorological data so as to comprise features not heretofore taken into the account. It is evident that even tentative efforts in this direction would arouse a lively interest, and would certainly stimulate criticism which, whether adverse or favorable, would tend to increase of knowledge, such as could never result from the utter stagnation and neglect to which this class of research has been subjected for extended periods. Such a plan would inevitably bring to a practical test the suggestions that have been made in various quarters recently as to the part which electro-magnetic forces of solar origin play in atmospheric control, and would tend to eliminate errors and crudities which are, to a cer- tain extent, unavoidable in the prosecution of a new line of research, and if there be a residuum of truth it would be shown bej^'ond a per- adventure, and its practical value demonstrated. These suggestions are the outgrowth of the practice which the writer has maintained for many years of journalizing phenomena of this class on a daily record. As the result, the conviction has grown that the principle of electro-magnetic induction of dynamic origin plays a far-reaching part in the economy of the solar system, and that it is concerned in atmospheric control in ways that are only just beginning to be understood. From his point of view, therefore, the scheme of communicating and recording observations above described is well worth trying. How it will impress other minds remains to be seen. [Copy of form used by the Peary Arctic Expedition in recording auroral phenomena.] Name and address of observer Date 189 Latitude and longitude of station Kind of time used Observations of the aurora in co-operation with Civil Engineer Peary, U. S. N., in Northern Greenland, are to be entered as follows : The absence of the aurora is to be indicated by entering in the proper space the figures showing the minutes of the hour during which such absence was verified by observation. Thus the entry "0-10" in the column headed 7 to 8 p. m. would be understood as showing that observations were made from 7.00 to 7.10 p. ra. and that there was no aurora at that instant. If observation is impossible from cloudiness or any cause it will be sufficient to leave the spaces entirely blank. The presence of the aurora is to be indicated by writing Aurora in the proper s{)ace and giving the exact times and other items under the head of Descriptions. No matter what else may be recorded, it is of the utmost importance to give as accurately as possible the times of any sudden increase or diminution in METHOD OF TESTING PREDICTIONS. 29 brightness of displays, together with estimates of the extent of sky covered and its posi- tion relative to the true north. Minute descriptions of the formation of arches, streamers, prismatic colors, and the like, accompanying such variations in the extent of displays, are of interest, but are far less important than that the times should be noted as accurately as possible. A pencil and paper carried in the pocket to note the times, etc., for the purpose of transference to the blanks will be found to be the most convenient plan, and will enable memoranda to be preserved that would otherwise be lost. Even scanty records when kept upon this precise plan may yield most valuable results, for it is impossible to tell in advance of comparison with others what particular entry, whether of the presence or absence of the aurora, may be found to be of the very highest interest. In the present instance the Arctic records will be continuous when- ever observation is possible, relays of observers connected with the expedition relieving each other. The records when complete may be returned to M. A. Veeder, Lyons, New York, U. S. A., who will supply blanks and all information desired. Date. 6 to 7 p. m. 7 to 8 p. m. 8 to 9 p. m. 9 to 10 p. m. 10 ton p.m. II to 12 p.m. i 12 to 6 a.m. DESCRIPTIONS. 8.— THE BEST METHOD OF TESTING WEATHER PREDICTIONS. Prof. Dr. W. Koppen. When weather predictions are issued, naturally there follows the wish of the authors to determine their trustworthiness. If one fol- lows this idea, it is necessary to decide between the various methods of verification. For this purpose the object must correspond with that which is followed in the verification of the predictions. If it is desired to facilitate a conclusive investigation of the rela- tion between predictions and the weather, both must be dealt with by the same method, as one would investigate the connection between two meteorological factors. It must be pointed out that predictions and the ensuing weather bear the relation to each other of two dependent functions and what conditions this relation implies. It should be shown how different kinds of weather follow different pre- dictions, as we show that different wind directions are followed by different temperatures, etc. The matter is simplest when one has to deal with predictions con- cerning which it is doubtful whether they really have a basis or whether they are to be regarded as pure chance predictions, as, for example, when both are based on the moon's phases. It is clear that even chance predictions must give a certain percentage of success. If, however, the real weather be put after the predictions under different headings, it becomes evident whether these figures are due only to 30 CHICAGO METEOROLOGICAL CONGRESS. chance or to the knowledge (even if it be occult) of certain laws, since, in the latter case, the weather, according to opposite predictions, would have been sensibly different, while in the first case it would remain the same. The supposition is always that a sufficiently large number of predictions has been included in the verification, since so long as the law of large numbers does not enter, the separation between chance and law is destroyed and no argument is possible, unless it be that the prognosticator is not infallible. For a better understanding of the above let us take an example from the summer of 1883. There were two kinds of predictions in- vestigated, which we will designate by classes A and B. The second columns give the contents of the predictions : The succeeding weather was- Class A ; Warm Cold .. Class B: Warm Warm, j Normal. Cold. Per cent. ] Per cent. 17 I 33 14 I 32 77 1 15 Cold I 0, 5 Per cvnt. 54 It is seen that, according to the prediction "A," the real weather remained the same whether the prediction read either warm or cold, but showed a marked contrast with respect to the prediction "B." Now the predictions "A" (made for a month in advance) are true chance predictions, although they excited great surprise and by many are regarded as satisfactory. "B" are synchronous daily predictions of a meteorological institute. In cases of this sort this method is entirely conclusive and sufficient. Concerning the " B " predictions, this table shows that between them and the following weather there exists an evident relation. In general there can be no question as to the predictions for only twenty-four hours ahead. Even with the most unskilful predictor there would be a general agreement for so short a time. It is to be asked, therefore, how close this connection is, and, indeed, if this relation can be expressed by a single numerical value. Detailed researches on the subject show that, unfortunately, a series of unknown values enters, and that an irreproachable derivation of such a simple number for the expression of the worth of a prediction is impossible — almost as impossible as to estimate the value of a person or a nation by a numerical expression. Such expressions have been proposed, for example, in America in 1884, by Messrs. G. K. Gilbert and C. S. Peirce, but the formulae given, although ingenious, are one sided, and have not a universal application. Still less, as a measure of the value of a prediction, can the usual METHOD OF TESTING PREDICTIONS. 31 percentage of success be used in which the influence of chance is neglected and the phenomena are treated without regard to their frequency. If one wishes to have an answer to the question, how often a certain prediction is followed by such and such weather, without regard to the reason, naturally such a calculation of per- centage is quite satisfactory, only in the first place we do not know what this can teach us, and secondly, as we shall see directly, from the method of calculation it is largely influenced by the personal in- terpretation of the verifier. It is, for example, very instructive to know that the 2,803 cases of tornado predictions are so divided that in 2,703 cases, when no tornado was predicted, in only 23 was one observed, in 2,680 cases not, and among the 100 cases where tornadoes were foretold they happened in 28 cases and did not occur in 72. No tornado predicted , Tornado predicted — Tornado occurred. No tornado. Per cent. Per cent. 1 99 28 72 From this statement it is seen that the predictor has in the last cases found the tendency to tornado formation. But what good 2708 is it when the fraction = 96.61 is given as the percentage of success of this prediction, a seemingly high number, but which is, nevertheless, inferior to that which would be had if, without trouble, a daily prediction of "no tornado" had been made, for then this 2752 number would be ^-— — = 98.18 per cent. The second cause which makes the value of the percentage of suc- cess, as usually calculated, seem very small, is the indefinite nature of the fundamental material, and therefore, the consequent impossi- bility of making the verification comparable. The determination of what follows a prediction has been generally sought on the basis of the verification of the general character of the day over a large territory, which is fixed by estimation. As to the sincere general wish to get at the truth by this estimation there can be no doubt. Only according to the interpretation of the words and the pessimistic or optimistic tendency of the verifier such esti- mates must difl^er greatly ; and even when in an institute, by precise instructions they are rendered independent of the person, it will never be possible to introduce such instructions and their interpre- tation in other institutes, or even to render them so invariable at the same institute that slight changes in their application will not afi:ect the results in an uncontrollable manner. For, in order to determine the influence of each of these rules or usages on the result, compre- hensive investigations would be needed, which have not yet been made and for which time would be required that could better be used in the 32 CHICAGO METEOROLOGICAL CONGRESS. extension of the basis of weather predictions. Besides, these per- centages of success, although as a rule they are understood to be the relation which the successful predictions bear to the whole number, yet they are generally to be considered as the means of the tests which the prediction would give if arranged in various gradations. Thus, most of the German institutes have arranged the predictions according to their results in three grades — the Bavarian Institute, since January, 1882, has used five grades — whose values are 100, 50, and 0, or 100, 75, 50, 25, and 0, as percentages of their entire accur- acy, but the arithmetical mean of these numbers has been taken as the percentage of success of the prediction. For the above reasons, at the Seewarte since 1886 the calculation of percentages of success has been abandoned, and in its place statis- tical summaries in the form already indicated, with as accurate a basis as possible, have been introduced. Also, in the Monthly Weather Review of the Washington Weather Bureau, since January, 1892, the heading " Verifications " has disappeared — a sign that at this great institute the value of these numbers is less considered than formerly.^ The method followed by the Seewarte carries out these principles : 1. In place of an approximate representation of the whole space and time covered, a precise determination is given for 8 a. m. and 2 p. m. at only three places in the German Empire. 2. For this verification the conditions, as shown by the meteoro- logical observations, are laid down in the following scheme : 8 a. m. 2 p. m. November 4 k u I e d n u m s h Novembers w z I w b n z m n r In which place 1 gives the deviation of the temperature from the normal : k =■ cold (negative deviation greater than 2°) ; w = normal (deviation to 2°) ; iv := warm (positive deviation greater than 2°). Place 2 gives temperature change in twenty-four hours : a = de- crease; ?t = stationary (change less than 1°); 2 = increase. Place 3 gives the wind force: I = light (0 to 2), m = moderate (3 to 4), etc. Place 4 gives the wind direction. Place 5 gives the precip- itation. 3. As far as the determination of the expression permits, the pre- dictions are also arranged in the same way in classes, and then the agreement of predictions and weather are worked up in comprehensive calculations and put in a tabular form. Further details will be found in the monthly reports of the Seewarte from 1886-1891, and especially in a supplement for 1886. Starting from similar ideas, the storm warnings of the Seewarte ' The calculation of the percentages of verifications has not been abandoned, but the results instead of being published monthly in the Weather Review are published annu- ally in the Annual Report of the Chief of the Weather Bureau. — Editor. METHODS OF TESTING PREDICTIONS. 33 since 1886 differ from those previously verified, and in this way — by a representation of the changes in the wind velocity according to the anemometer indications at the normal observing stations of the Seewarte in the six hours preceding and in the thirty-six hours fol- lowing each storm warning. The comprehensive tables which have been compiled and published by the Seewarte present much material for study which is well con- solidated and is thoroughly controllable and comparable. Herein is a precise answer to many questions whose clear comprehension and solution are of great importance for the use of the prediction service. For making up reports to the public, on the contrary, they are too complicated, and demand more knowledge of the difficult questions concerning calculation of probabilities than is often found. The ultimate question, which for practical purposes is preeminent, is, what is the value of weather predictions ? Still, this question must remain under all circumstances unsettled, no matter how many or how well founded are the figures cited concerning the measure of the success of the predictions. When, for example, an accuracy of 80 per cent is found for the prediction, one person may consider this per- centage as very good, another that the 20 per cent of failure is suffi- cient to invalidate it, a third may say that he does not find just what he needs in the prediction, the fourth may state that the prediction is worthless if it does not come to him sooner, the fifth may declare the most successful warnings to be useless because he might have predicted just as well the bad weather, and so on. A strict proof of the practical worth of weather predictions and storm warnings is im- possible, but the general impression of competent persons must be considered conclusive, and in this combined impression the fulfillment of the prophecy counts for only one, though perhaps the most im- portant, of many circumstances. If we ask ourselves whether the great working experience which has been gained in weather predictions during twenty years bears a proportionate relation to the results obtained, we must decidedly say no. Among the people there is a widespread belief that the predictor, by a strict and thorough verification of the prediction made by him, must make great progress in his judgment and experience. Were this so, then the verifications would be a duty and worthy of the attention of the meteorologists to whom the task of issuing predictions falls. Really, this task is, as anyone who has prosecuted it long will admit, on the whole a very thankless one, and the time which is expended on it can be much better employed upon meteorological investiga- tions in statistical meteorology upon which the predictions rest. If one will study critically the prediction service, the investigations should at least be as thorough and carried out according to as strict methods as at the Seeioarte, A report to the public should, in this 3 34 CHICAGO METEOKOLOGICAL CONGRESS. case, be as free as possible from numerical data, because figures on this subject are generally misunderstood and really carry only prac- tical convictions in certain directions and only to specialists. For such a report, a statement, as direct and as free from excuses as pos- sible, with concrete examples and the opinion of specialists, is the most convincing and suitable. 9.— PRESENT CONDITION OF THE WEATHER SERVICE- PROPOSITIONS FOR ITS IMPROVEMENT. Prof. Dr. W. J. van Bebber. In the states in which weather telegraphy has been used in connec- tion with weather forecasts, either for agriculture or navigation, the experience has been generally that the views on the value of forecasts have been partly overstated and partly understated, and that the hopes which the weather service first inspired have not been fulfilled. The reason for this lies in the fact that our knowledge of the causes of meteorological phenomena is so meager that the practical weather prediction is always accompanied by frequent and great failure, which jeopardize more or less its usefulness, that the progress of prac- tical meteorology is uncommonly slow, and scarcely noticeable, and, finally, that the knowledge of meteorology generally, and especially of the principles underlying prediction, is so slight that such influ- ences as the moon, have, even with learned people, equal or greater value than the prediction issued by scientific institutions. It is incontestably true, that the predictions of the institutes really have a basis which is capable of further development, and that already in the present state of our knowledge of atmospheric phe- nomena and their changes, they may be useful for practical vocations, provided that all available means shall be used in their issue and distribution, and that the public understand how to estimate their worth. On account of the great practical meaning of the forecasts which increases with their accuracy as well as with the extension of the interval of time covered, it appears our duty to strengthen and to spread the fundamental principles in order to accomplish what is possible and to meet the wants of the public in every way. It seems difficult to put together the success which has been attained in the several states in order to have an adequate survey of the utility of the weather service in these states. True, figures show- ing the percentage of success have been published by the various Institutes, but these have for the estimation of the real worth and utility of weather prediction but very little value, since in the veri- fication a series of circumstances must be considered which influence the final result greatly. Chief among these are the probability of THE WEATHER SERVICE. 36 the occurrence of a weather phenomenon, or chance, also the persist- ent tendency of the weather, and finally, the greater or less use which can be derived from the forecast. So long as all these points do not find recognition in the verification, the percentages of success, no matter how scientific and rigorous the verifications may be, are only of secondary importance, and can not, as may easily be shown, be regarded as proper criteria for the success or failure of the predic- tion. But, in the efforts to take account of all these circumstances we come to the difficulty, which appears the more insurmountable and the greater, that much must always be left to arbitrary decision. Upon these points a detailed report of Prof. Dr. Koppen is pre- sented to the Congress, so that further discussion is unnecessary.^ The best, and up to now, the only correct and definite scale for the utility of prediction is the judgment of the public and of that por- tion of the public which is most interested in the predictions, that is to say, the coast inhabitants and the agriculturists, who, from their vocations, are most dependent upon wind and weather. As regards the first class, opinions have been given in the United States, by the London Meteorological Office, and by the Deutsche Seewarte. According to these the coast dwellers regard the storm warnings, in spite of the frequent failures, as a desirable arrangement. As a fur- ther confirmation of the utility of the storm warnings I would add the fact that on the German coast the Provincial authorities and some private persons have erected and maintained signal stations at their own cost, where those of the Government were not sufficient. The judgment of the public on weather predictions for agricultural and industrial purposes differs generally so much that it appears impos- sible at present to draw valid conclusions as to the value of the same ; however, I have always had the experience, as is the case elsewhere, that those persons who have a direct interest in the predictions place a greater value upon them than those who regard the thing as more indifferent to their professions. On the whole, it can be affirmed that even in the present state of weather prediction great use can be derived for practical life, so that the practice of it by Institutions ought not to be given up or cur- tailed. Therefore it appears a pressing necessity to employ all suit- able means to advance weather prophecy, such as (relating to weather telegraphy) the speedy collection and distribution of the reports and (regarding prediction) the application of p,ccumulated experience which can add to the progress of the service, that is to say, the exten- sion of the predictions. ^ See Section I, p. 30. See, also, Van Bebber: "Die Ergebnisse der Wetterprog- nosen," MonatshericM der Deutschen Seewarte, 1886 +. "Ergebnisse der Sturm- warnungen," ib., 1889 +, and Das Wetter, 1889, p. 268. Monatliclie Uebersicht der Wittei-ung, Hapaburg, 188?. Monat&bericht der Seewarte, Hamburg, 1889. 36 CHICAGO METEOROLOGICAL CONGRESS. The greatest, and also the best organized, system of weather teleg- raphy is in the United States, so that we may take this as a model for the other countries. In Europe there must be radical reforms, the most pressing of which we will briefly, but emphatically, mention : Of the greatest importance is the acceleration of the telegraphic service, both for the incoming and outgoing telegrams, and upon an international basis. For this purpose the introduction of a circuit system (as is used in the United States and latterly for other purposes in Germany) appears necessary. It would suffice, if, immediately after the observation, the lines should be placed at the disposal of the Central Institutes for one-half to one hour, during which time they could be placed in possession of the united telegraphic material. This telegraphic matter, including the number of stations and the scope of the data, must of course be reduced as much as possible. With this the introduction of simultaneous (world) time is necessary. The advantages and disadvantages as regards local time would seem to counterbalance one another. It is greatly to be deplored that in Europe, although it is recog- nized as a necessity, uniform hours of observation can not be agreed upon. On this point the Institutes should come to a decision. As soon as the data are collated they should be sent to a number of secondary stations so that within a few hours after the working up of the observations the deduced synopsis and predictions can be given to the public. A suitable remuneration for the trouble of the observers is desirable. More frequent information, at least three times a day, as is now done at many Institutes, increases greatly the efficiency of the weather service, as well as more frequent issue of predictions when it suits the requirements of the public, for which a principal hour can be easily agreed upon by the Institutions. The idea first suggested by Buys- Ballot to connect the registering apparatus of the chief station con- tinually or occasionally, so that at any time the course of the distant weather elements may be known (tele-meteorology) was nothing more than a dream of the meteorologist which should operate for a short time over a small region. And yet this idea seems very useful for the purposes of weather forecasts, and especially for storm warnings, so that from its moderate cost it is to be recommended for introduc- tion over limited areas, as I have already shown. If the chief tele- graphic lines, which at certain hours, especially during the night, are not used, could be arranged for tele-meteorology, the changes of the weather elements at a serieS of distant stations might be registered continually or intermittently at the principal stations. The principles which in our region are used for the making of fore- casts,. I have given in my book on "Weather Predictions," and the opinion expressed is that the fundamental principles are the same THE WEATHER SERVICE. 37 everywhere. In the present state of the science it appears advisable to advance further in the beaten track and thereby to fix and extend the basis. In weather prediction the distribution of pressure and its manifold changes are of greatest importance, that is to say, the position, the progress, and especially the changes of the high and low pressure areas. The last show, indeed, characteristic weather conditions, but these are greatly modified by secondary formations. These seconda- ries, which have a much more regular course than is generally sup- posed, merit chiefly our attention, since their influence on wind and weather is of decided importance. These depressions often make the carefully prepared predictions, especially storm warnings, fail totally. Not infrequently they cause sudden increase of wind, a change in its direction, and consequently great temperature fluctuation and heavy precipitation, and in summer widespread squalls or tornadoes. On the south side of depressions they mostly move quickly over large extents of country; sometimes, moreover, they change their posi- tion but little and resolve themselves into an extensive region of low pressure, or fill up. This is the reason why forecasting is associated with so many difficulties which can be the more slowly overcome because the preceding occurrences in the upper air, which, without doubt, have the closest relation to those on the surface, are almost entirely unknown to us. To what meteorological elements shall the predictions refer ? Evidently such as will meet the demands of the public — that is to say (certain conditions excluded), for the coast people, first, wind direc- tion and velocity, then fog, and finally the other elements ; for the agriculturists, first, precipitation, next temperature, then cloudiness and wind. On account of the uncertainty of the predictions, details should be avoided (which are often given) and the doubtful should be more re- pressed, especially when the weather situation is uncertain, and then the most important elements for practical purposes should be dwelt on. If the weather situation is uncertain this should be stated in the prediction. The intensity of the precipitation is very difficult to predict and can be done only in certain cases. Denmark has to my knowledge the simplest predictions for agricultural purposes which only state whether the weather for the following day will be dry, changeable, or rainy. This method has much value, it seems to me, as at the same time temperature and other predictions are given when they seem necessary to the public and when the weather situa- tion warrants them. Long experience has shown that the predictions which have the greatest chance of success are those which have the closest relation to the pressure distribution, such as the direction and strength of the 38 CHICAGO METEOROLOGICAL CONGRESS. wind ; next, those which depend chiefly on the wind and air trans- portation, that is to say, the temperature phenomena and to some degree the hygrometric conditions of the air. According to this, the prediction of clouds, fog, and precipitation is always more difficult than those of wind and temperature, because here, besides the air movement, other factors occur, such as vertical air currents, topo- graphical conditions, etc. From what has been said it follows that the results of the storm warnings are more favorable than those of the agricultural predictions, although the percentage of success seems to prove the contrary. The reason is that with cloud, fog, precipita- tion and in less degree with temperature, not only chance but also the persistent tendency play an important role, while the probability of the occurrence of a storm and of its continuance is relatively ex- tremely small, so that even percentages of success which hardly reach 50 ought not to be regarded as unfavorable, though predictions of the severity of the storm and the timeliness of the warnings are of much importance. Evidently predictions which rest only on chance or on persistence are absurd ; for it is the changes of weather mainly which must be predicted. Snowdrifts occur most frequently in certain types of weather, and therefore, the communication of such warnings to the railroads ought to be valuable. Such an arrangement exists in Russia since 1891, and the results have not been unfavorable, seeing that most railroads regard the warnings as useful. That predictions of the changes of the height of rivers (floods) can well be made has been sufficiently proved by the experience in the United States, in Bohemia, and in other countries. The value of the predictions, aside from their trustworthiness, is also dependent upon the length of time which they cover. Up to now most of the Institutes issue forecasts only for the following twenty-four hours or for the ensuing civil day. The shortness of this time does not correspond to practical needs ; often the predic- tion only comes to the public on the day for which it applies. A prediction for two, three, or more days in advance, if the accuracy was not very much less than that for one issued one day ahead, would be of the greatest value. It is only a question whether in the present state of practical weather knowledge such a step is desirable. Everywhere experience has showii that in general over large regions the same weather condition lasts a considerable time and then, finally, either slowly or suddenly, is transformed into another more or less opposed ; so that, for example, periods of dull, rainy, and stormy weather are followed by clear, dry, and calm w^eather with which the temperature phenomena, chiefly dependent upon the air movement, on the season, and on the cloudiness, have to do. If a typical weather condition is formed, it appears that a long-range THE WEATHER SERVICE. 39 prediction can safely be made, and it only remains to announce an alteration in the character of the weather or a change of weather. In long-range predictions two cases occur, viz. : (1) To determine the degree of probability that the weather character will last a longer or shorter time, and (2) to predict this change. The last is by far the most difficult, and we ought not to forget that a critical point of weather prophecy lies here — an uncertainty which it must be the aim of practical meteorology to remove, but whose full accomplishment can not be expected at present. In weather forecasting, the position of the country relative to its system of stations and to the track of low pressure areas is important. The European countries lying to the westward, such as the Iberian Peninsula, France, Great Britain, and Norway, are hardly in a position to issue long-range predictions whose success would be comparable with those issued by the countries lying to the eastward. Towards the south of the globe the changes in general weather character become less, but, on the other hand, local phenomena are more marked. In northern Europe typical weather phenomena are the rule, but the propagation and the changes of the depressions (secondaries) show many changes in which the disturbances coming from northwest and west present the greatest anomalies. It would be of the greatest advantage for long-range forecasts if the weather service stretched westward into the ocean, both by weather telegrams from the Faroe Islands, Greenland, and the Azores and by telegraphic reports in the eastern regions of the North Atlantic Ocean, from the ports of the trans-Atlantic steamers, which often outstrip in speed the depressions. Thereby would the costly trans-Atlantic telegrams received from Washington, concerning the weather in the west of the North Atlantic, have more value. The situation of the eastern United States is favorable for weather predictions for some time ahead, although the movement of the maxima and minima is much quicker than in Europe, and conse- quently the changeableness of the weather is much greater than in Europe, and the more so, since the northern and southern air cur- rents present such extreme contrasts as occur nowhere else over so extensive a region. In spite of all these ideas, long-range weather predictions can only, according to my mind, be recommended when they are issued with the necessary prudence and when they are made with a strong proba- bility of success. In conjunction with these the customary forecast for the following day should be maintained, as is done.at the Weather Bureau at Washington. Recently, the Seewarte has given in its weather summary opinions of the probable course of the weather for an indeterminate time, as soon as the weather situation warranted it, and with good results. Latterly, also, in Switzerland long-range 40 CHICAGO METEOROLOGICAL CONGRESS. predictions have been made (but not published), and not without success. The efficiency of the weather prediction can be increased in a high degree by teaching the public the ruling principles and to connect the local observations, made with or without instruments, with the general atmospheric conditions, so that in certain cases it can judge why the actual course of the weather agrees or does not agree with the predicted, and, under certain conditions, how far the forecasts must be modified. Local observations in combination with the gen- eral weather situation give results which are not to be undervalued, since in most cases they take into account the changes which the weather conditions undergo in a certain place. In order to enable the public to follow the weather conditions day by day, the circula- tion of newspaper weather charts appears very desirable, and here I may cite the efforts of the Berlin Weather Bureau, which, increasing year by year, at present furnishes weather maps to seven of the great daily papers, besides those posted on the numerous Urania columns. On the other hand, it is to be desired that the chart issued by the Institute should be sold at a moderate price, or, if possible, distrib- uted gratis. The free distribution of the forecast telegram is also to be recommended. Unfortunately, we have to admit that such a desirable understand- ing of practical weather lore is unknown to the public, as well as to learned persons, and we must further admit that the blame rests partly upon the fact that most meteorologists consider it sufficient to pre- sent to the public the relatively few principal doctrines of practical meteorology, and do not exj)ose superstitious views or limit their belief. I have already stated the fact that the weather bulletins and charts issued by the meteorological institutes, and partly also the predictions, have only a small practical value if their comprehension be wanting. It is the duty of every meteorologist, so far as he can to strive in this direction, not only on the ground of utility but also for the advancement of science. Finally, the accuracy of weather forecasts can be greatly increased if the specific cases be compared with similar previous cases. Therefore it is very desirable to arrange the weather charts of the previous years according to general methods, such as storm tracks, in order that these comparisons may be at once instituted. Thereby our experience and also our skill in making predictions will be greatly advanced; and we are soon able, at the sight of any weather chart, to form a judg- ment as to the.probable sequence of the weather conditions. Such a procedure must be attended with good results, as my own experience has shown. It appears desirable that for vast regions, such as North America and Europe, with the neighboring oceans, a numerous col- lection of systematically arranged charts should be published which THE WEATHER SERVICE. 41 would permit the course of the elements to be traced from the pre- ceding to the following day. Such an atlas would be of great value, not alone for the Institute but also for the public, which is now often able to form an idea of the prevailing weather conditions from the newspaper weather charts. A special atlas for the agricultural fore- casts and one for the storm warnings appears in any case necessary. Since the Vienna Congress and the Utrecht Conference there has been little accomplished by the meteorological congresses and con- ferences ; therefore it is to be hoped that at the present Congress the most pressing needs will be satisfied. APPENDICES. [Extracts from letters received by Dr. Van Bebber from rei)resentatives of weather services in reply to questions relating to the present condition of the weather service in their respective countries.] I. — Meteorological Service, Canada. 1. The degree of accuracy of our forecasts of temperature, rain, and wind for one, tioo, or three days in advance. 2. As to the principles on which the forecasts depend, and the character of the weather loe are able to predict. 3. As to the advisability of predicting rain, and the extent to which loe shoxdd predict temperature or other changes viewed from the stand- point of what it is possible to predict with a fair degree of suc- cess, and what it is the public cares to know ? 1. The ordinary forecasts of the Canadian Service are issued from the Central Office at Toronto at 11 p. m. daily, and are distributed by the various telegraph companies to nearly every telegraph office in the older provinces, and in Manitoba. The forecast is for the twenty-four hours from 8 a. m. of the morning after issue to 8 a. m. of the following day, i. e., practically a thirty-six-hour prediction ; a supplementary forecast is made at 10 a. m. each day, modifying, if necessary, that of the previous night, but is not very generally util- ized, as the Toronto and Montreal evening papers and the Toronto Board of Trade are the only means by which the public can obtain them, unless by direct inquiry from Toronto Observatory or the tele- graph offices at Toronto. In making the ordinary forecasts the predicting officer at Toronto endeavors to give the public as accurate an outline as possible of the weather during the prescribed period ; he is not bound by any hard and fast rule to predict for every suljject that may be included in the general word " weather," such as wind velocity and direction, temper- ature, rain, and weather in the more restricted meteorological sense, although in every instance he feels bound, even when grave diffi- culties are to be contended against, to forecast as to the probability 42 CHICAGO METEOROLOGICAL CONGRESS. of rain for at least that portion of the prescribed period which lies between 8 a. m. and 11 p. m. of the next day. As a rule, a prediction is made for wind velocity and direction, weather, temperature, and rainfall, both as regards time and amount for each of the various districts into which the Dominion has been divided. Each morning the forecasts of the previous day are com- pared with the actual weather, and each item entered in a table under the headings "number of predictions," "number fully verified," " number partly verified," " number not verified." At the end of the month, when more numerous reports have been received, these figures are checked, and if necessary changes made, and a percentage struck by taking half those " partly verified " as verified, and the other half as not verified. In every instance rain is counted as a prediction, absence of rain when predicted being counted a failure, as is also rain when no prediction of it has been made. The tables on pp. 43 and 44 show the degree of success with which we meet in forecasting rain, wind, and temperature, and that, roughly speaking, we are about as likely to fall into error by predicting it too often, as by not predict- ing it often enough. It sometimes happens, in the more settled weather, that the pre- dicting officer feels very sure of his ground and makes a two or three day prediction, but no separate percentage of verification of such predictions has been kept. Telegraphic and telephonic inquiries for extended predictions are being continually received at the observa- tory, and the fact that certain firms, of various descriptions, have for years made a practice of asking for extended forecasts, and by word of mouth and by letter, acknowledged their usefulness, proves that such forecasts are, to say the least, fairly successful. 2. The forecasts as issued from Toronto depend altogether on a knowledge obtained from practice and study of the movements of areas of high and low pressure on this continent, and the weather which, under various circumstances, accompanies these areas, taking fully into account in predicting for certain districts the influence that winds of different directions and increased or diminished mois- ture will have in the various cases. The predicting ofiicer has by experience learned much as to the influence that areas of high pres- sure and of low pressure will probably have on each other as regards development or dispersion and rate of movement, and makes his pre- dictions on the basis that the pressure changes will be as he antici- pates. It is not an uncommon thing for him, when an abnormal movement of a cyclone has occurred, to base a prediction on the assumption that such movement was either directly or indirectly caused by another cyclone beyond the region of observation, for instance at sea, and in this manner many storms on our seaboard have been foreseen, the existence of which would otherwise not have been suspected. THE WEATHER SERVICE. 43 Although, up to the present time, very little use has been made of the kind and direction of upper clouds, it is full well recognized that a greater knowledge of the relationship of the upper currents to cyclones and anti-cyclones may ultimately lead to more exact and extended forecasts. Even at present weather prognostics dependent on clouds are not by any means ignored, as in cases of doubt as to the hovering or change in direction of movement of a cyclone, such indi- cations are at times of decided value. 3. What is it the public cares to know? The mariner wants to know, just prior to sailing, the force and direction of wind he may expect during periods varying from a few hours to several days ; fish- ermen are ordinarily satisfied with twenty-four-hour forecasts; the agriculturist wants to know generally as to the likelihood of rain during harvest time, and, in the case of the Northwest farmer, the likelihood of early frosts ; the shipper of perishable goods wants to know the best time to ship in order to escape severe frost ; the gen- eral public wants to know the general character of the weather to be expected on any given day and the day following. Our ordinary forecast percentages show that we are able to predict direction and velocity of wind with tolerable accuracy for a period of thirty-six hours, and, at times, for a longer period, and we have a per- centage of verification of storm warnings of 84 per cent ; therefore, the meteorological service is of benefit to the mariner. Our percentages show a verification of 74 per cent for thirty-six- hour forecasts of rain. We know that the public generally, and the agriculturist in particular, consult the probabilities and believe in them ; therefore, it is obviously advisable to predict rain. Our percentages show a verification of 84 per cent for temperature for thirty-six-hour forecasts, and during winter the service is con- tinually consulted as to cold waves, etc. This shows that temperature predictions are possible, and are appreciated by that portion of the public more directly interested. — B. F. Stupart, Predicting Officer. Table showing percentage of verification of predictions of rain, temperature, and wind velocity. Predictions. >, £• 8 03 3 03 a L4 t>^ a >. 3 > S =8 IP s <; s s 1-^ S < Z 152 120 130 128 131 I2S ISS 131 137 136 122 142 108 92 »3 79 81 7» 108 94 103 82 69 104 32 12 20 17 25 18 20 16 15 25 27 17 133 n5 132 153 147 161 159 156 160 151 152 159 7« 73 79 qo 95 110 113 93 104 105 112 102 26 lb 30 30 20 26 24 32 14 20 17 28 I S3 148 164 I.S4 152 ISS 181 i.SS 155 155 155 166 86 q8 lO.S Iiq 98 96 128 94 100 98 92 110 47 31 26 24 33 30 30 24 23 28 32 32 Precipitation. 1890— Number Fully verified Partly verified 1891— Number Fully verified Partly verified 1892— Number Fully verified Partly verified 1,607 1,081 244 1.778 1. 154 283 1.893 1,224 360 44 CHICAGO METEOROLOGICAL CONGRESS. Table showing percentage of verification, etc. — Continued. Predictions. Peecipitation— Continued. Total for three years- Number 438 383 Fully verified ! 272 263 Partly verified 105 59 Total percentage for three years ■ Temperature. 1890 — Number Fully verified Partly verified 1891— Number Fully verified Partly verified 1892— Number Fully verified Partly verified Total for three years- Number Fully verified Partly verified Total percentage for three years Wind velocity. Number Fully verified . Partly verified. Number Fully verified .... Partly verified 1892— Number Fully verified Partly verified Total for three years- Number Fully verified ... . Partly verified.... Total percentage for three years 1781 166 III 120 37 1 18 426 435 430 267! 288| 274. 76 71 78 145 147 124' 108 14 80 242 229 158, 152 42 53 59 256 252 193' 195 46 38 493 442 349; 2S1 74 72 153 141 126; 120 lOIj 78, 17 277, 228 3i| 38 107 271 77 8 16 53I 80 29 46 i6 18 442 429; 467 285 273; 316 73 76 77 136 146 115 124 13 242 268 158! 189 38 50 5.278 3.459 887 73-9 1,450 1,186 133 1,702 1.354 216 1,737 1.347 222 4,889 3,887 571 83-7 945 682 154 957 698 142 819 533 157 2,721 1,913 453 78.6 Rain predictions for June. 188S 1889 1890 1891 1892 Number of predic- tions. Fully ver- ified. 43 Partly ver- ified. Not ver- ified. Percentage fully ver- ified. 81.8 58.3 64-3 60.0 69.2 66.2 Percentage fully and partly ver- ified. 91.0 83-3 85-7 80.0 92-3 86.2 Days of no rain predictions. Year. Number of days. Fully ver- ified. Partly ver- ified. Not ver- ified. Percentage fully ver- ified. Percentage fully and partly ver- ified. 1888 15 13 II H 13 12 6 8 9 6 2 3 2 I 3 I 4 I I 4 80.0 46.2 72-7 81.8 46.2 93-3 69.2 91.0 91.0 69.2 1880 1890 l8qi i8q2 63 41 II II 65.1 82.5 THE WEATHER SERVICE. 45 II. — Danish Meteorological Institute. COPENHAGEN. We issue only storm warnings. For nautical purposes, signals are displayed in Helsingor for the wind conditions in the Cattegat, which signals ca,n be seen by ships about to sail. The daily weather review is also posted in each port. Our daily weather map is based on the morning telegrams from three English, three Norwegian, seven German, four Swedish, two Russian, nine French, and eleven Danish stations. Every day a sum- mary of the weather situation is given, as well as the weather forecast. The forecast is only expressed in general terms, and we take no pains to name each element in our forecast. Hektographic copies are posted in various parts of the city as well as at the port. The review and forecast are telegraphed at 2 p. m. to all telegraphic stations and then publicly displayed. During the months of June to September an afternoon service is maintained. The review and forecast are based on meteorological dispatches from three English, one Norwe- gian, two German, one Swedish, and four Danish stations. The fore- cast relates mainly to precipitation, and the following terms are used: "clear weather;" "generally clear weather;" "changeable weather," and " rainy weather." The forecast is telegraphed at 5 p. m. to all the telegraph stations. At many places the forecast is transmitted from the nearest telegraph office to the neighborhood by optical signals. — Adam Paulsen, Director. III. — Norwegian Meteorological Institute. CHRISTIANIA. We receive telegrams from Norway, Sweden, Denmark, the British Islands, France, North Germany, and Russia. Besides synoptic charts of the preceding evening and the morning, we construct charts of change of pressure from evening to morning, change of tempera- ture in the last twenty-four hours (8 a. m.), deviation of the tem- perature at 8 a. m. from the normal, and temperature distribution at 8 a, m. Only the synoptic charts are posted. For the greater part of the year our predictions (extending from noon to noon) are only published in Christiania. In all months they apply only for Chris- tiania and neighborhood. The area is more limited in winter than in summer. In winter we predict, as far as we can, temperature, precipitation, and wind. In the summer months (June-September) the predictions, intended for farmers, give precipitation. These are telegraphed and telephoned southward to Skien, northward to Hamar^ westward to Randsfjord, eastward to the boundary of the kingdom. We have attained 90 to 92 per cent of success. Storm warnings are only occasionally sent to the coast when the 46 CHICAGO METEOROLOGICAL CONGRESS. weather signs in Scotland at 8 a. m. have begun to give warning. Storm warnings are not sent farther north than Bodo. The shore community is satisfied. We have received latterly pecuniary aid from the Storthing in order to undertake special weather studies with the intention of establishing local systems of weather warnings with local centers in Bergen, Throndheim, and at the great fisheries (Lofoten, for example) under the direction of local meteorologists as directors. The principles according to which we issue warnings are hard to analyze — scientific instruction, local experience, imagination. It is quite as much an art as a science which one practices. — Dr. H. Mohn, Director. IV. — Russia: Central Physical Obseevatory. SAINT PETERSBURG. I send you reports of the observatory for the years 1886-1891, as well as the report concerning the service of the forecasts of snow- drifts on the railroads. With the permission of the director. Dr. H. Wild, I add an extract from the report for 1892. The rules which we follow for weather predictions are about the same as stated in your (Dr. Van Bebber's) excellent book, which is used as a text book in the forecast department. Since July, 1892, after previous trials, the general weather predic- tions have been subjected to regular tests, as published in the bul- letin. The predictions for the districts of European Russia (compare map in supplement to Daily Bulletin) have been separated and veri- fied for the four elements of precipitation, cloudiness, temperature, and wind. For each of the elements three grades were distinguished, a hrgh, a mean, and a fair grade. The predictions were considered as successful when, at the majority of stations in the given district, the predicted phenomena were observed in the jjredicted degree. As partly successful were taken those predictions for which the phe- nomena did not show the indicated grade but the next one to it. As unsuccessful predictions were regarded those for which the opposite of the predictions was observed. Uxample. Prediction. Observation. Verification. r Thick clouds Successful. Thick clouds \ Cloudy Partly successful. [Fair In the final verification of the degree of success of the prediction the number of partly verified predictions is distributed, half to the successful and half to the unsuccessful prediction. THE WEATHER SERVICE. 47 The exact determination of the notation, the sub-division of the districts, and the choice of the grade for the characteristic weather demand, however, special meteorological researches; consequently, the verification adopted for 1892 is to be regarded as a first attempt to determine the proper criteria. The results of the verification are given in percentages in the fol- lowing table : Verification of the general weather predictions for six months (July-December) of 1892. Predictions. Successful. Unsuccessful. Per cent. 8o.6 77-2 82.5 80.8 Per cent 19.4. 22.8 17-5 19.2 85.6 79.0 80.9 14.4 21.0 19. 1 75-8 85.6 80.2 79-5 24.2 14.4 19.8 20.5 81.0 19.0 Districts: Northwestern Russia Western Russia Central Russia Northeastern Russia. Eastern Russia Southeastern Russia . Southwestern Russia. Elements: Precipitation Clouainess Temperature Wind Mean Besides the general weather predictions which are published daily in the bulletin, more than one hundred and fifty replies are given by the department to private inquiries (mostly from Perm and Nizh- nee-Novgorod ) concerning the expected weather. Besides this, dur- ing three months (in summer and autumn) daily weather predictions are made for Pawlowsk. From the preceding table it is evident that the percentages of the successful predictions for the different districts of European Russia are dissimilar, being larger in the east and smaller in the west. This difference is more marked in the comparison of the results of pre- dictions for single places. The number of successful predictions for those stations lying in the east (Perm, Nizhnee-Novgorod, Saratov, etc.) is 80 to 81 per cent, while in Pawlowsk it only reaches 63 to 64 per cent. In the supplement we reproduce three letters ^ from Mr. Panaew and one from Mr. Batjuschkow, in which the writers express their thanks for the predictions sent them. From these letters it appears that our predictions are practically useful ; this result is for us the more satis- factory since it is not based on single chance forecasts, but upon a whole systematic series of predictions, of which naturally a certain percentage may be bad. It should here be remarked that both the above-mentioned gentlemen were subscribers to the telegraphic ^ These letters were not received by me. — Editor. 48 CHICAGO METEOROLOGICAL CONGRESS. « weather predictions and in consequence paid for each one a tax of 50 kopecks besides the usual tax. In both letters the wish is expressed that further progress may be made. Storm learnings for the Baltic and for the Black and Azof Seas in 1892. [The general results, expressed in percentages, are for all districts.] Warnings. Verified Partly verified Late Not verified ... Baltic. 63 Black. 65 The percentage of storms which were not predicted, whose force exceeded that indicated by one ball, was, for the Baltic Sea, 10 per cent (1891, 13 per cent) ; for the Black Sea, 19 per cent (1891, 23 per cent). If we combine the verified and partly verified warnings the result of the successful warnings for 1892 is as follows : Baltic Sea, 85 per cent (1891, 76 per cent) ; Black Sea, 76 per cent (1891, 69 per cent). — Ch. Rykatchcw. V. — The Weather Service in Austria. VIENNA. In Austria the issue of a telegraphic weather report was begun January 1, 1877. This service is carried on by three ofiicials of the " Section for Weather Telegraphy," whose office since the year 1879 is in the center of the city in the building of the Imperial Academy of Science. The telegraphic material has increased notably since 1877. At present there are received daily weather reports from thirty-six Austro-Hungarian and from sixty-six foreign stations. These are dispatched in twelve combination telegrams to 158 domestic and foreign stations. The monthly subscription price for the weather report is 1 fl., 50 kr. The weather report goes to the printer not later than 3 o'clock, and is sent out regularly before 5 o'clock. At the present time there are ninety-nine subscribers to the weather report ; the number of free, exchange, and obligatory copies amounts to eighty. Besides the printed weather report, there have been sent since 1877 daily prediction telegrams which go chiefly to the landed proprietors, health resorts, and the larger provincial papers. Since the year 1884 the prediction telegrams have been in cipher, whereby the subscrip- tion price has been reduced 50 per cent to its present price of 5 fl. per month. The telegrams are issued generally between 1 and 1.30 p. m. The success of the predictions is, on the whole, satisfactory, aver- aging 85 per cent. The subscribers to the prediction telegrams have varied since 1878 from fifty to eighty-three. As regards the relation of the public and their interest in the weather to the predic- tion service, the journalists hold an important place. In Vienna all THE WEATHER SERVICE. ^ 49 the great newspapers are forced by their readers and correspondents, both in the morning and evening editions, to print the telegraphic weather reports with the predictions. When, from lack of space or other reasons, the weather report does not appear, complaints come at once to the publishers. The confidence in the weather predictions manifests itself most strongly in the fact that not only the Viennese, but also the great proprietors in the provinces take pains to procure the predictions. — Dr. J. Hann, Director Central Bureau for Meteorology and Terrestrial Magnetism. VI. — HuNGAEiAN Meteorological and Magnetic Bureau, Budapest. Weather predictions were issued in 1881 by direction of the Min- ister of Agriculture, at that time Baron Kemsny, by Dr. Szentgyorgyi Weisz, who, however, was independent of the Meteorological Insti- tute. The dissemination of the forecasts was accomplished through the newspapers ; the telegraphic dispatches were insufficient and after eight years' continuance this arrangement was given up. In the year 1888 the task of making weather predictions was en- trusted to the Meteorological Institute, but still, this service, in the too narrow limits to which it was confined by the previous organiza- tion, could get no firm hold. A noteworthy advance in this field can be recorded when I took the direction of the Central Bureau. On June 15, 1891, our first syn- optic charts appeared, whose issue was facilitated by a subvention from the Minister of Agriculture. The forecasts were publicly posted in Budapest and their circulation was confined to the daily newspapers. On account of the great importance of the predictions in an agricultural state like Hungary, a quicker and more general dissemination of the forecasts was desirable. The present Minister of Agriculture, Count Andreas Bethlen, manifests a lively interest in the matter and, acting on my suggestion, has succeeded in enlist- ing the Ministry of Commerce. The creation of such a method of forecast dissemination as exists in Hungary, according to my knowl- edge, has not come about in any other European country. There was inaugurated, primarily, a general official method of dis- tributing the predictions in the interest of the farming community. Accordingly, on August 1, 1892, the first forecast dispatch (in cipher) was issued as an appendix to the official "circular dispatch," which contains the quotations of the Budapest merchandise and grain ex- changes, and by way of experiment this forecast dispatch was sent to one hundred and thirty telegraph offices for official distribution to the public. Each of these telegraph operators received, also, a suit- able bulletin board on which the data and the announcements form- ing the forecasts were to be hung. There belong with each board 4 50 CHICAGO METEOROLOGICAL CONGRESS. twelve small tablets for the different mouths, thirty-one tablets (bearing the numbers 1-31) for the days, and thirty-one for the pre- dictions. On the last are, together with the cipher, also the an- nouncements belonging to each. The telegraph operator is thus re- lieved of all trouble of translation ; his task consists only in taking from a box that tablet which bears the cipher of the forecast dis- patch just received and in hanging it up. This method of spreading the information deserves to be mentioned because it is a free one and is solely for the benefit of the agricultural community. Much public interest is everywhere manifested, and the agricultural societies in many counties have applied to the Govern- ment for an increase in the number of telegraph operators who have been entrusted with the receipt and the puljlication of the forecast dispatches, so that at present one hundred and thirty officials have been appointed, and after May 1, 1893, two hundred and sixty tele- graph offices will serve to disseminate the predictions. Further, for remote places and for Puszten (inns in out-of-the-way localities) an optical method of signaling is projected, so that by displaying dif- ferent colored flags, baskets, and cones (made of osier) the forecasts will be made known. On my estate in O'Gyalla and on that of the Minister in Bethlen this scheme is already in operation. The forecasts relate, exclusively, to the conditions which are of interest to farmers, that is to say, especially to precipitation and temperature . and, incidentally, to cloudiness. Storm warnings are not issued. The forecasts apply for the following twenty-four hours, but in consequence of the importance which a forecast of the weather for two days ahead possesses for agriculture, in certain cases of weather stability one is undertaken for two days with the announce- ment, "weather conditions persistent (w)," as well as, when the weather condition admits, a change for the second day is indicated by "later precipitation (x)," or "later clearing (z)." The varia- bility of the climatic conditions requires that from the extent of Hungary, in special cases, the rain probability should only relate to certain regions, which is indicated by the announcements "precipi- tation in the west (1)," "precipitation in the south (j)," etc. The forecast dispatches are sent until 3 o'clock each afternoon from the Institute to the telegraphic centers. At present the Meteorological Institute is hoping for a reorgan- ization which will create a special section for " Weather Telegraphy and Forecasts." It will only then be possible to study the weather conditions in detail from the point of view of forecasts, and to pre- pare the needed statistical data. Regarding the success of the forecast dispatches, I can only now cite the computed results which relate to the quarter August-October, 1892. The figures are obtained by a comparison of the forecasts THE WEATHER SERVICE. 51 with the records, at the hours 7, 2, and 9, of twelve uniformly-dis- tributed meteorological observing stations. These forecasts were verified in the above-mentioned quarter, for precipitation, 84.7 ; tem- perature, 76.1 ; and cloudiness, 86.2 per cent. With the establish- ment of a special section it is the intention to develop further the whole forecasting service, of which I may speak more at length later. — Dr. N. von Konkoly, Director. VII. — The Weather Service in the Netherlands. UTRECHT. Installation. — At Utrecht, after the arrival of the dispatches from the Netherlands, about 10 to 11 a. m., the report is placarded and published in the morning edition of the local newspapers which appear about 1 p. m. Beneath the report is entered the greatest barometric deviation which is (graphically) represented on the aeroklinoskop (c/., Invoering en Verklaring, translated by Dr. Jelinek with the title The Aeroklinoskop). In the afternoon, about 3 p. m., the weather chart, manifolded by the hektograph process, is issued, beneath which is a summary of the greatest barometric deviation at 8 a. m. and 12.30 p. m., and a weather prediction for the twenty-four hours following the observation. The weather charts published at Utrecht are sent elsewhere on payment of postage. Results. — The results of the predictions are seldom expressed by figures. Results of the storm warnings, which are based on the dif- ferences of the barometric deviations, are published annually in the Niederldndischen Meteor ologischen Annalen. The results of the two last years are that 60 per cent of the storm warnings were not verified. Presentation to the public. — The organization of the weather service, which is essentially represented by the Telegraphisch Weerbericht ten dienste van den Landbouio and which dates from the close of 1882, was for several years unfavorably regarded by the public, just as the storm warnings were for the fifteen or twenty years preceding. There followed a period, which still continues, when the public, took little or no notice of the weather reports. Only about 1889 was there shown a greater interest by the public which manifested itself in the appearance of a daily weather chart in two newspapers, the first and up to now the only ones in the Netherlands to publish these charts. The degree of accuracy in predictions of temperature, snow, rain, or wind, tioo or three days in advance. What principles are adopted in such predictions? Utrecht issues a definite wind prediction, which is founded on the difference of the barometric deviation, and a more or less detailed weather prediction for the ensuing twenty-four hours. A temperature and wind prediction is seldom made for the second twenty-four hours, never for the third, and never, as regards rain, for the second period. These predictions, like those for the first twenty- 52 CHICAGO METEOROLOGICAL CONGRESS. four hours, are based on the determination of the current gradient (not barometric gradient) of the air in a vertical and horizontal direc- tion, on the modifications which they may undergo during the day, and on the physical changes which may result. It is desired chiefly to predict those weather elements which are most related to the duration of the prediction, such as temperature and rain, for example. Rain prediction is the most important for the public, and is also the most uncertain ; even the thunderstorm prediction, which has even more value and also is the surest, has often only a local verifi- cation. — Abridged translation by Mr. Engelenburg. AMSTEEDAM. The weather service in Amsterdam furnishes information about the weather not only to the public in Amsterdam, but also to the Staats- anzeiger and the Harlemmer Zeitung. These papers receive as full a summary as those in Amsterdam. The report is telegraphed to the Staatsanzeiger each noon, while the Harlemmer Zeitung sends for it. The latter paper wishes no tabular data, but only a summary. Be- sides, there is sent to other places in the Netherlands a weather sum- ■ mary, with a wind prediction added to the Telegraphisch Weerbericht ten dienste van den Landbouw. These reports are published by harbor- masters, provincial newspapers, etc. Finally, in many places in Am- sterdam, and also in Harlem and at the office of the Harlemmer Zei- tung, hektographic weather reports are posted. I believe the value of the Telegraphisch Weerbericht ten dienste van den Landbouio to be very small. A mere statement that " a depres- sion lies northwest and far off" or "a high pressure area northeast and in the neighborhood" is incomprehensible and of no value to the public. The abstracted tables containing data for some domestic and for- eign stations may, however, be useful, but, in general, I do not think that the ordinary newspaper readers care much for the report. It is otherwise with seaports, where great differences in the barometric devi- ations may serve as warnings to seamen. This branch of the service should, according to my ideas, be better supported. The aerokli- noskop, which is set up in some places, does not fulfill the want. To the ports (especially Delfzyl, Nieuwe-Diep, Ymuiden, Zandvoort, Scheveningen, Maassluis, Vlaardingen, Hellevoetsluis, Brouwershaven, Vlissingen) storm signals, analogous to those of the Deutsche Seewarte or those long employed on the English coast, should be supplied. The aeroklinoskop can only be read at a little distance, and demands too much imagination on the part of the simple fishermen and sea- men. The reports which the Amsterdamer Zeitung, the Harlemmer Zeitung, THE WEATHER SERVICE. 53 and the Staatsanzeiger receive are fully appreciated by a portion of the public, really more than the editors of the papers realize. The Harlemmer Zeitung shows that the public does not know exactly for how long the prediction applies, since a great part of its readers believes that the whole of the next day is included in the prediction. In Amsterdam the prediction never extends more than twenty-four hours, and since the report is made up between 12 and 2 (including the last observation at 12.30 p. m., from the interior) the prediction ex- tends from noon of one day to noon of the next. According to my ideas, it is too uncertain to make predictions for two or three times twenty-four hours, for in such cases the disappointment is greater and the confidence is decreased. For inland places where the papers, un- like the Staatsanzeiger^ do not receive a full report, and give it only in the evening to their readers (until the Telegraphisch Weerhericht ten dienste van den Landbouiv makes way for a better arrangement), the weather reports, consequently, can be of little use. The predictions, as they are now carried on in Amsterdam, indi- cate : Wind direction, and in the case of great barometric differ- ences, wind force ; also the general weather, designated as follows, "good weather," "tolerably good weather," "little change," "change- able weather," "squally weather," "boisterous weather," etc. When the condition of the depression is accompanied by a strong tendency to rain there is added to the prediction " much probability of rain," "rain or snow," etc. Finally, there is sometimes hazarded, as regards temperature, something in the nature of a conjecture — "warm weather," "cold weather," "higher temperature," "lower tempera- ture." Since the rain and temperature predictions can be made with much less certainty than those for wind and general weather, they are not usually given and only when -their fulfillment is tolerably certain. Agriculture should derive the greatest advantage from these rain and temperature predictions, and therefore it is my opinion that agri- culture receives no material advantage from the weather service. Navigation, on the contrary, which is chiefly concerned with wind and general weather, can derive much benefit from the weather service, especially when storm signals can be given the ports. I would men- tion that in Ymuiden there are often sent to war and sometimes to merchant vessels, ready to leave, a complete dispatch containing a re- review and a forecast. Further, according to my idea, by the em- ployment of a private telephone line the harbor and fishing port of Ymuiden could receive much better information than it does now. Probably Maassluis, opposite Rotterdam, is in the same situation. The wind and weather predictions, as drawn up in Amsterdam, are based on the general situation in Europe at 8 a. m., and on the probable changes and their sequences, for which the Handbuch der aus- 54 CHICAGO METEOROLOGICAL CONGRESS. itbenden WitteruiKj.^kunde of Dr. W. J. Van Bebber, and more recently the Wettervorhersage of the same author, are used as guides. If one considers that in the Netherlands only once in twenty-four » hours a review of the situation over Europe can be had, and in Ger- many, for example, this is made three times a day, it appears to me that the result of the predictions in Amsterdam is not wholly unfavorable. It is very much to be desired, that (for example at 1 p. m.) some dispatches should be received directly from England, France, and Germany (for example six or eight) and immediately charted. If that could be done, the value of the prediction would thereby be greatly increased. Nevertheless, I repeat,^ no dispatch should be more than one hour late. In brief, my opinion is, that apart from some progress which may still be made in meteorology as a science, it is very desirable, as may now be done, by an acceleration of the dispatches and a proper means of distributing and publishing the reports, that the public should derive greater advantage from the reports than is at present the case. — Abridged translation by L. Boosenburg. ROTTERDAM. The weather service in Rotterdam is confined to the communication of weather reports to the papers published in Rotterdam and the dis- tribution of this report within the parish. This is accomplished by mere mechanical working up of the dispatches received ; it seems to me, therefore, that a central bureau can hardly be spoken of. Predic- tions are not made here, unless the paragraph which follows the barometric deviations from the normal be regarded as such, for ex- ample, the paragraph "indicates a . . . . wind," or in the hektographic weather reports " according to. the Buys-Ballot law, there should be a . . . . wind." I have left these expressions because it is difficult to give a full explanation each day, but I do not consider them as forecasts. It is only the statement of two phenomena between which there exists a certain relation without our being able to say in general that one is the cause and the other the consequence. The value of weather predictions published for the public appears to me doubtful, especially because to the forecasts which are unsuc- cessful much more attention is paid than to the others. From*'private telegrams, especially in commercial circles, it has often been shown to me that much interest attaches to weather reports which make known the true situation, and that it is to be regretted that our reports do not cover a larger portion of Europe. The method of procedure here is as follows : At noon, the Scheep- voort newspaper sends for a list of the reports already received. This list is posted outside a Avindow of the newspaper office in the neighbor- THE WEATHER SERVICE. 55 hood of the Exchange. At certain seasons, dependent on the sugar crop, a copy of this is posted in the Exchange. Between 2 and 3 o'clock a complete weather chart is hektographed, and the Scheep- voort distributes sixteen copies throughout the city, which are acces- sible to the public at large, and are also posted in localities where many interested persons assemble, as for example, exchanges, com- mercial clubs, societies, etc., for the benefit of navigation, navigation schools, trades unions, etc. Further, about 6 p. m., there appears in the Scheepvoort a small map, printed by the Rung system, and about 5 o'clock a full list with a general review is published in the Neue Rotterdamcr Zeitung. This paper, also, has received for some time past a graphic representation, in a form devised by the editors, of the highest and lowest barometer and the temperature during the five preceding days. The great expense which the Scheepvoort incurs, as well as the large space which the Neue Rotterdamer Zeitung, from interested motives, devotes to this matter, and the questions which occasionally reach me through the editors of these papers, impress me with the fact that they count among their readers many who are interested in this sub- ject. — Abridged translation by Arkenbout Schokker. VIII. — London Meteorological Office. Dr. Van Bobber's letter asks various questions: (1) As to the degree of accuracy in our forecasts of temperature, rainfall, wind, etc., for one, two, or three days in advance. (2) As to the principles on which the forecasts depend, and the character of the weather we are able to predict. (3) As to the advisability of predicting rain, and the extent to which we should predict temperature or other changes viewed from the standpoint of " what it is possible to predict with a fair degree of success and what it is that the public cares to know." The following replies are drawn up, not exactly in the order in which the queries are put, but in such an order as enables me to re- ply more clearly and briefly than I could otherwise do. " Forecasts " or " predictions " are issued by this office, as follows : The first are prepared at 10.30 a. m., and issued at 11 a. m. (Sun- days, Good Fridays, and Christmas days excepted), and are mainly dependent on the observations taken at 8 a. m. daily (see copy of the Daily Weather Report) and relate to the weather to be expected dur- ing the twenty-four hours ending at noon on the following day. They are intended chiefly for publication in the Daily Weather Report, in the afternoon newspapers, and for exhibition at certain positions in the city and west end of London, including most of the clubs. The second are prepared at 3.30 p. m. (Sundays, Good Fridays, and Christmas days excepted) from 2 p. m. observations, and made at a limited number of stations, as supplementary to the 8 a. m. ob- 66 CHICAGO METEOROLOGICAL CONGRESS. servations. They relate to the weather of the ensuing civil day. They are always posted at the door of the office for inspection by the ""public and during the hay and wheat harvests are telegraphed gra- tuitously to a selected number (about twenty-eight) of agriculturists who make their contents known as widely as possible, and keep a careful check on their accuracy. The third are prepared at 7.30 p. m., daily, and are issued at 8.30 p. m. These also relate to the weather of the ensuing day, and are dependent on observations made at 6 p. m., as supplementary to those made at 8 a. m. and 2 p. m. They are intended mainly for publica- tion in the morning newspapers of the following day. They are, therefore, all of them, for a period of rather more than twenty-four hours in advance of the time of issue, and are utilized in answering inquiries by the public as to coming weather. Special "warnings" as to the advance of storms are sent by telegraph to the coasts threatened, whenever the indications are believed to be of a stormy character. These may be sent at any hour between 9.30 a. m. and 8 p. m., and are made known by the hoisting of a cone (point up for northerly, point down for southerly gales) at the ports to which they are sent. In the forecasts the wind (direction and force) and the weather are predicted separately, in a somewhat general lyanner, as the dis- tricts for which they are prepared cover a considerable area. In the weather portion any kind of weather is included, if it is likely to be a prominent feature, but at present hardly any attempt has been made to estimate the intensity of coming rain — the local variations in the character of the country and the variations in intensity of thundershowers being too abrupt to make minute detail desirable. Such expressions, however, as "rain at times — heavy locally" are employed when deemed necessary. With regard to changes of temperature, two distinct classes are kept in view, (1) those of a general and (relatively) of a permanent character affecting the mean temperature of the approaching period, and referred to in such expressions as "colder," "much colder," "warmer," "much warmer," etc., and (2) those of a diurnal char- acter which, in such periods as that recently experienced over our islands, are very large, and are referred to in sentences such as " cold at night, warm during day." No attempt has been made hitherto to check the accuracy of such forecasts, except as forming part of the weather portion of the predictions, but it is believed that they are as good as those for any of the other features included in the forecasts. With regard to the success which has attended the issue of the forecasts, reference may be made to many distinct sources : ( 1 ) to the official checking of the 8.30 p. m. issue, carried on in this office from the information received daily by wire. The results of this THE WEATHER SERVICE. 57 checking will be found on pp. 11 and 63 of the Rej)ort of the Meteor- ological Council for year ending March, 1892, and are very fairly satisfactory. (2) To a similar checking of the 3.30 p. m. forecasts, based on information supplied by the recipients of the forecasts (see same report pp. 12-13) and the favorable opinion expressed by them in their letters to the council ; also, to the fact that the same gentlemen are glad, year after year, to receive the forecasts, to make them known, and to keep the record necessary to check them. (3) That among those who make inquiry privately, the same names appear regularly in successive years, whenever the informa- tion is required, although a fee is levied for it, and the costs of trans- mission by wire (when necessary) are paid by the applicant. (4) To the facts that (a) the National Lifeboat Institution applied recently to have the forecasts telegraphed daily to the officers in charge at their various stations, as a guide to them in their duties (a request which was reluctantly declined only because the cost of nearly £1,000 per annum was more than the Meteorological Council were able to meet), and (b) that the Agricultural Department is even now endeavoring to make arrangements for telegraphing the 3.30 p. m. forecasts daily to all agricultural districts during harvest time. (5) That the authorities at Her Majesty's Dockyard, Devonport, now have the 11 a. m. forecast telegraphed to them every day for guidance in sending the smaller vessels to sea ; and that Her Majesty never puts to sea without having the latest forecast transmitted to her by wire. (6) That the newspapers in all parts of the kingdom have not only published the forecasts regularly for many years, but in most cases pay a considerable sum for cost of telegraphy, when the offices are too far distant for them to be delivered by hand, and that The Times paid £500 per annum for the exclusive use of the 6 p. m. forecasts, and subsequently the three leading London papers paid £900 per annum between them for the use of the same forecast until the Government made a grant to defray the cost and make the infor- mation free for all papers. With regard to what the public wish to know — they would un- doubtedly like (a) to have the forecasts issued for a longer j)eriod in advance, probably for seasons, and (h) that more minute detail should be observed in localizing the regions likely to be affected by rain, and the intensity of the coming fall. At present, however, it has not been found possible to gratify these wishes. This brings us to the consideration of the principles adopted in pre- paring the forecast, and the line of work or study which promises to increase their accuracy. With regard to the principles adopted. — They depend mainly upon a recognition of the well-known characteristics of cyclonic and anti- cyclonic systems, primary, secondary, or V-shaped, and upon the 58 CHICAGO METEOROLOGICAL CONGRESS. indications afforded by the three daily observations as to their move- ments and the questions of their tendency to increase or decrease in area or intensity. The general distribution of pressure (also whether favorable for a continuous prevalence of cold or warm, of dry or wet, currents of air), the effects of such currents when coming from off the sea, or vice versa, the relatively rapid motion of air on coasts when compared with that over land, and the variations produced by the seasons on such phenomena are all carefully thought out before preparing the forecasts or issuing warnings, besides the question whether the disturbances are of a " thunderstorm " or other character, Willi regard to the line of work or study most likely to increase the accuracy of the predictions. — It appears probable that some rearrange- ment of the districts for which they are prepared, the separation of coast from inland parts of the countries and of the west from the east portions of the Irish districts, is desirable. It is probable, also, that a better knowledge of the upper currents of the air, as shown by high clouds, is necessary, and that a more careful study of the distribution of rainfall under varying types of pressure distribution and at different seasons of the year (distinguishing between the various classes of rains) may improve the forecasts materially. That every effort to bring about such an improvement is desirable must be patent to all — sailors, agriculturalists, and dwellers in towns being all interested in the results. At present it has loeen found impossible to institute seasonal fore- casts with any reasonable hope of success. — Frederic Gaster, Chief of Forecast Division. IX. — Berlin Weather Bureau.^ The telegraphic reports are received from the Deutsche Seewarte in Hamburg, and during the past year another telegram has been received from the Royal Bavarian Central Bureau, containing the reports from the four stations, Ziirich, Genoa, Lugano, and Bozen, which have proved very useful. We use the telegraphic material for the purpose of weather fore- casting in the construction of isobars and isotherms, and for about a year I have worked with an assistant (formerly Dr. Siihring, now Mr. Basilius) iii plotting lines of equal pressure and temperature varia- tion in twenty-four hours. The method of verification of 'our fore- casts has undergone a great change since its commencement in the spring of 1884. Together with the systematic verification of the fore- cast, resolved into the elements, I have verified also, as a whole, each forecast according to the Seewarte method (I, entirely successful, up to ' This is a private business enterprise with its headquarters at the Agricultural High School. — Editor. THE WEATHER SERVICE. 59 V, entirely wrong), in which I have endeavored to take account of the views of the local public as much as possible, and, therefore, to give proportionately more weight to the predictions concerning rain and temperature than to those relating to cloudiness and wind conditions. From these rules the following percentages of success were obtained for the years 1885-'92 : I. II. III. IV. V. Success. Winter (Dec. -Feb.)... 18.2 48.1 29.6 4.1 0.0 81.1 Spring 21.6 47.6 26.4 4.4 0.0 82.4 Summer 15.3 49.1 29.7 -5.7 0.2 79.2 Autumn 18.2 44.9 32.6 4.3 0.0 79.4 Year 18.3 47.4 29.6 4.7 0.0 80.5 The most favorable month was April, with 83.2 per cent ; the most unfavorable, October, with 76.2 ; and next, July, with 78.9. I would here remark that the forecasts are issued between 2.30 and 2.45 p. m., and apply for the whole of the following calendar day. In single years an increase in the figures denoting success is not evident, and indeed the first years show the greatest success, viz., 1885, 86.7 per cent, and 1886, 84.6 per cent. This arises, however, from the fact that we now attempt to give to the forecasts a more definite meaning, especially to emphasize the expected weather changes, and perhaps, also, our own judgment about the mistakes has become harsher. The continually growing interest of the public is perhaps best shown by the results outside of the Bureau, and I quote below the number of newspapers to which, at the commencement of each year, we were furnishing weather charts and forecasts : January 1. 1885. 1886. 1887. 1888. 1889. 1890. 1891. 1892. 1893. Forecasts 4 6 6 7 7 16 17 16 17 Weather cliarts .. ..2444 6 67 7 The great increase from 1889 to 1890 is partially explained by the fact that Mr. 0. Jesse, who up to that time had made forecasts for four local papers, gave this up in 1889. For the representation of weather charts an attempt was made by us in 1885 to stamp them on type metal, and in the following year the scheme had been so far perfected that it was applicable to stereotyped papers, among which the Berliner Tageblatt, which had already for many years printed weather charts by an etching process, adopted ours ; this underwent a further improvement in 1889 by the substitution of black for white figures and symbols. Besides this newspaper block, which is ready at 2.30 p. m., we have delivered since May, 1892, daily, except Sun- day, at 4.15 o'clock, hektographic weather charts for the local "Urania columns." I will now, after this long and detailed account of the working of our weather bureau, state briefly the experience we have obtained in our efforts to improve the forecast methods. It appears to me that the efforts toward longer forecasts, even if they are more general, promise 60 CHICAGO METEOROLOGICAL CONGRESS. better success than the more exact ones for the next day. In addition to the thorough researches of Van Bebber, upon the typical tracks of minima, it appears to me that a more detailed investigation of Teisserenc de Bort's weather types would be very profitable, and I believe that, to the knowledge of their frequency, duration, change, sequence, etc., my weather charts might contribute somewhat. As to the wish of the public respecting the forecasts for the ensuing day, it has been my experience that no little importance is attached to the explicitness of the forecast. So, for example, it will not suf- fice to give the announcement " changeable weather." Here, as every- where, the greatest attention must be given to the precipitation fore- cast, and it should be the aim gradually to separate more and more the local from the general rains, and in summer the simple " tendency to thunderstorms " might be replaced by a greater or less " probability of a thunderstorm." Perhaps, a systematic investigation of the vari- ation of the absolute humidity, for which I have for several years been collecting data, might contribute something to this question, although, naturally there are other more important researches. I believe that a more exact knowledge of the recent precipitation dis- tribution is very necessary, for which reason I would urge that in our telegraphic dispatches the tenths of degrees of temperature be replaced in summer by the amount of precipitation, and in winter by the depth of snow. But the subject is too large a one to be exhausted in one letter, so that I fear I have already entered too much into details. — Dr. E. Less, Director. X. — The Forecast Service in Switzerland. The creation of a daily weather forecast, based upon synoptic meteorological data, was first undertaken in Switzerland by the undersigned, in the summer of 1878, in a private way. In the year following it was done officially by direction of the Swiss Govern- ment ; and the issue of a daily weather bulletin was made one of the duties of the Swiss Central Meteorological Institute, established in May, 1881. As Switzerland is divided into several (3-4) districts whose cli- matic conditions are essentially different from one another, it was originally planned that the forecasts should be made at several points, based upon a synoptic summary telegraphed to each from the central office. But the observatory at Berne has been the only one to undertake the issue of special forecasts for the surrounding terri- tory ; so that, as a matter of fact, the forecasts of the central institute at Ziirich have continued to be the only generally distributed prog- nostications. But in view of the peculiar geographical position of southwestern Switzerland (on account of the influence of the lower THE WEATHER SERVICE. 61 snow-valley), the Central Institute has for several years past issued special forecasts for that district. The necessity for a forecast service for that jDart of Switzerland which lies beyond the Alps (Tessin, Engadin) has up to the present been less urgent, mainly because the weather of that district is much more constant than on this side of the Alps. For this reason no special forecast for southern Switzerland is as yet issued, although it would be less difficult than for the northern portion of the country. The distribution of the forecasts from the central office is made partly through the newspapers and partly to private persons by tele- graph, for which latter purpose the telegraph authorities have granted a considerable reduction in rates. The forecasts are usually given out shortly after 2 p. m., and have been made only for the day fol- lowing. Recently, however, a beginning has been made to forecast for longer periods than twenty-four hours, and not without success ; but these forecasts are not yet published. The forecasts embrace temperature, precipitation, and character of weather. Direction and force of wind are considered only when steep gradients exist, since, with slight gradients, the topographical features ol our country govern the local wind movements, which depend almost entirely upon the course of the valleys and character of the ground (lakes, woods, etc.), and their prediction for each little district would hardly be possible, and would be useless. The forecasts of the central office are verified both at the office itself and by the observers at the meteorological stations at Aarau, Lucerne, and Neufchatel. In consequence of the topographical peculiarities already referred to, the verification is not applied to each separate meteorological element, but is made according to three classes, wholly verified, partly verified, and not verified, according as to whether the forecast was correct or incorrect with reference to all or only a part of the meteorological elements considered in it. The average found at the four stations is 72 per cent wholly verified, 24 per cent partly verified, and 4 per cent not verified. The attitude of the public with reference to these forecasts is, gen- erally speaking, a sympathetic one. That the institution meets with confidence is shown by the very numerous special inquiries which reach the central office by telegraph from far and near. It must be stated, though, that in cases of total failure and especially when, in place of the expected fine weather bad weather occurs, the criticism of the public at large or of individuals is a pretty severe one, espe- cially in comparison with that which is in some cases extended to the so-called popular weather prophets. Nor can it be denied that crit- icism is occasionally colored by a malicious joy at the failure of the so-called scientific prophecy. The needs of the public, with reference to the forecasts, are not so 62 CHICAGO METEOROLOGICAL CONGRESS. much to know whether there will be a slight rise or fall in tempera- ture (leaving out entirely, as above indicated, wind direction and light wind), as to be informed of the general character of the weather. The absolute state of the temperature is only in a few cases (in spring) of special interest, and the same may be said as regards the amount of rainfall (when there is danger of floods). In most cases only the general character of the weather is under consideration, and consequently the greatest importance is attached to its correct determination. Sudden changes, especially, demand the most attentive consideration. The so-called local influences pecu- liar to our mountain country are important factors in this connec- tion. Of very great importance is the distribution of the atmos- pheric pressure on both sides of the Alps. It depends upon this dis- tribution whether or not the influence of a depression moving from north to south will extend to the foot of the mountains. There need be no well-defined wind movement (Fohn) in this case, at least not in the lower regions. The so-called Fohn-effects (otherwise dam- ming up at the mountains and favoring precipitation) make them- selves felt even with a comparatively small barometric gradient, and may delay for two or three days, or even entirely prevent, the forma- tion of clouds and precipitation, while at no great distance from our frontier the weather undergoes a radical change. The study of the influence exercised by the Alpine mountain chain as a climatic factor (which may, perhaps, be also felt in dynamic meteorology) is of the utmost importance for the improvement of the forecasts in our country, and this study requires the most careful fostering of the meteorology of the upper regions through the estab- lishment of good observations at mountain stations. — R. Billwiller, Director. XL — The United States Weather Bureau. The forecasts and warnings of the United States Weather Bureau are based upon a study of reports of observations taken daily at 8 a. m. and 8 p. m., seventy-fifth meridian time, at one hundred and twenty-four regular reporting stations in the United States and nine- teen points in Canada. These reports are promptly telegraphed in cipher to the Central Office at Washington and to the more important Weather Bureau stations, and also transmitted by telegraph to the Canadian Central Office at Toronto. During the West India cyclone season ])rovision is made for timely reports by telegraph of disturb- ances noted in that region. Instructions covering tlie making of observations and filing of re- ports at the telegrapli offices allow of no deviation from prescribed methods nor departure from fixed rules. A reference to these methods and rules, and a brief statement of the processes involved from the THE WEATHER SERVICE. 63 making of the observations at the several stations to the issue of the forecasts and warnings at the Central Office, will probably best illus- trate the system of the Bureau. Promptly to the hour and minute the work of observation is begun at each station, and simultaneously the small army of observers per- forms the several operations pertaining thereto. Within a specified period the enciphered reports are filed at the telegraph offices and placed upon circuits devoted exclusively to their transmission. At 8.45 a. m. and 8.45 p. m., daily, the work of deciphering the reports and charting the data is begun by a force of trained experts at Washington. The average time required for this work is about one hour. Upon the completion of the charts the Forecast Official dictates a statement of the general and special meteorological features pre- sented by the reports, prepares the forecasts for the various districts, and issues such signal orders as the conditions may require. The dictation covering the synopses, forecasts, and warnings is set in type and also telegraphed as it progresses, and at the expiration of the thirty to forty-five minutes required for the performance of this work the utterances of the Forecast Official have been filed for transmis- sion to all points in the United States reached by electric telegraph. The press associations furnish the daily press with the regular forecasts and warnings, and also transmit special statements or bul- letins issued in anticipation of unusual or alarming meteorological conditions. In addition to dispatches transmitted by the news asso- ciations, weather and temperature, cold wave, and frost messages are telegraphed at Government expense to specially apj)ointed display- men and selected points, exclusive of regular observers and stations of the Weather Bureau, as follows : Displaymen of weather and temperature signals 1, 613 Displaymen of cold-wave signals 174 Displaymen of frost signals 458 Total paid messages 2, 245 In addition to the above, messages for public display are tele- graphed to 2,129 railroad stations; messages are telegraj)hed or tele- phoned to 620 places ; forecasts are sent by mail to 3,065 points ; and are delivered by cooperating railroad train services to 1,264 stations. The total number of places to which the forecasts or warnings are sent is 9,323. As before stated, this number represents only regularly authorized display stations, and does not include thousands of per- sons and places furnished by the various local Weather Bureau offices throughout the country. In addition to the above, and exclusive of regular stations of the Weather Bureau, signals giving warning of dangerous gales are displayed at 121 points on the sea coasts and the Great Lakes. 64 CHICAGO METEOROLOGICAL CONGRESS. While the comparative degree of accuracy of the forecasts for dp- fined periods is shown by the percentage of verification, the best proof of their value to the public is the increasing demand for the predictions. Their distribution is now limited by, and coextensive with, the scope of the electric telegraph and telephone. The regular forecasts of the Weather Bureau are issued from the Central Office at Washington by or before 11 a. m. and 11 p. m., seventy-fifth meridian time, daily. The morning forecast is made for a period of thirty-six hours, and the night forecast for a period of twenty-four hours. In the discretion of the Forecast Official fore- casts are made for periods of forty-eight hours. The regular, and what are termed twenty-four and thirty-six hour forecasts, specify the character of the weather, such as general or local and heavy or light rain or snow, fair or clear weather, higher or lower tempera- ture, including terms indicating the amount of the anticipated rise or fall in temperature, and the force, direction, and shifts of the wind for each State or part of State east of the Rocky Mountains. The remaining States and Territories, with the exception of New Mexico and Wyoming, are covered by forecasts issued at San Fran- cisco, Cal., and Portland, Oreg. The morning forecasts are of special value to outlying or country districts, as the messages giving forecasts for the following day can be sent to displaymen and points referred to, and the signals and bulletins displayed without delay. These forecasts also appear in all of the evening papers of the coun- try. When the morning reports indicate unusual or dangerous me- teorological conditions, special telegraphic rejjorts are called for and supplementary warnings are telegraphed to threatened districts at the discretion of the Forecast Official. The night, or twenty-four hour, forecasts are of value chiefly in cities and towns where the pre- dictions are disseminated through the medium of the morning news- papers. The early closing of telegraph and telephone offices in the smaller towns and villages prevents a prompt transmission of the night forecasts to outlying districts. The verification of forecasts for thirty-six hours shown by the tables is determined by the conditions presented by the morning and evening reports of the day succeeding that for which the forecast is made, and the verification of the night, or twenty-four hour, forecasts is based upon the data which are shown on the night charts of the following day. Cold-wave signals are verified if the required fall in temperature occurs within thirty-six hours after the signal is ordered, although the order must specify the period within which the fall is anticipated. A forecast of rain for a State requires for a full verifi- cation that seven-tenths of the State shall be embraced within the rain area. When a smaller portion of the State is covered by the rain area the percentage of verification is proportional to the area of THE WEATHER SERVICE. 65 rain. When no rain falls the percentage of verification is zero. Sim- ilarly the percentage of verification of forecasts of temperature is proportional to the area of the district included by the temperature changes. Rainfall is considered for the twelve-hour periods ending at 8 a. m. and 8 p. m., and verification of temperature forecasts is determined by the twenty-four hour temperature changes. The following tables show the percentage of verification of rain and temperature forecasts for twenty-four and forty-eight hours, and also the percentage of verification of cold wave and wind signals during the last two years : Percentage of verification of rain forecasts. Year and month. Total Average . 24 hours. 48 hours. 418 353 456 334 440 669 512 480 332 198 238 414 4,844 65-9 74-9 74-3 58-9 72.4 69-3 74-9 73-8 70.4 71.9 83-4 67.2 71.2 202 53-9 92 65-5 14 47.1 7 78.6 44 21.4 25 63.2 10 70.0 10 74.0 40 36.2 Year and month. 1893. January February . , March , April May , June July August September , October November , December., Total . . . Average . 34 hours. 48 hours. 346 649 704 557 234 493 554 .638 339 364 472 5.350 67.2 82.1 80.2 76.0 77.6 74-7 72.4 56.8 73-6 77.6 71. 1 73-5 68.1 83-9 70.0 62.6 Percentage of verification of temperature forecasts. 1891. 1892. 1S93. 24 hours. 48 hours. 24 hours. 48 hours. 24 hours. 48 hours. Month. 1 E 3 6 f u u Or c s 5 4J c 1 e z s a § .0 S a Z a S 3 o39 989 937 885 830 784 754 707 667 £22 582 518 461 412 372 307 272 238 218 186 168 "5 107 33 Gauge zero above mean GulfleveL Feet. •265. 88 254-54 229. 36 207.29 182.71 160. 22 140.72 125.82 107.47 95.18 86.74 68.36 44.78 31.48 15-63 2-59 2.69 — 1.20 — 0.20 —2.12 — 0.02 —0-35 —1.98 Gauge readings. Lowest. Highest Feet. 14 — 0.2 —0.4 1.6 —0.9 — 2.2 —0.2 2.1 0.0 0-3 1.8 -3-8 —3-9 —4.0 0.0 0.0 —2.1 0.9 0.2 1-7 0.0 —1.6 0-5 Feet. 45-8 41-5 37-8 36-7 35-6 40.2 48.1 42.9 50-4 50.2 44-3 41.9 49-0 45-1 48.6 48.9 42.2 38-4 33-8 30.6 26.0 17.4 17.9 6.9 Bank-full stage. 41 34 36 35 31 32 42 36 44 42 40 36 44 40 46 42 38 33 28 The distances from the Gulf of Mexico, given in the above table, are channel distances above Saint Louis and mid-bank distances below that point to the Gulf. The elevations of gauge zeros are derived from duplicate lines of precise levels extending from tide water of the Gulf along the river to Saint Paul. The lowest and highest readings given are the lowest and highest stages, respectively, that have been recorded from the time the gauge was established until July 1, 1893. Bank-full stage means that stage of water which reaches the top of the average banks in the vicinity of the gauge. From the above table the slopes at high and low stages between successive gauges may be deduced. Gauges have also been established on all the principal rivers of the United States, and the river-stage bulletin of 1892, issued by the Weather Bureau, comprises daily readings at 160 stations. The credit of developing this department of the Weather Bureau belongs to Prof. Thomas Russell, and the last bulletin bears strong evidence of his energy and good judgment. Carefully kept and accurate continuous records of this kind will become invaluable to the future engineer who takes up the study of decrease in flow of streams. Careless records are misleading and worse than none, and it is to be hoped that the Secretary of Agri- culture will see the necessity of keeping this department in the hands of a man who fully appreciates its importance, and has the skill and judgment necessary to secure and digest the desired results. The flood planes of the river become more and more marked as we PlaUK OcJCerJOTx. J^c hLLo MO KY. rAducah JacksoTtport^ ARK. TENN MempAis ^ \^ , _. r-' , .— g:.— — » I I ^ MISS. I MAP «Jtow]n5 ^ ^ LA ^}/aichez VRecUUrerl/and^ . \ • \ Location of gauges, \ \ \ \ ^^^^^X^^^^i a u Lt r of M £X r FLOOD PLANES OF THE MISSISSIPPI. 83 approach the mouth of the Ohio River, and the floods grow more and more destructive as the accumulated waters of the tributaries roll down the vast alluvial plain toward the Gulf. Hence the principal data here considered is that of the Mississippi River below the mouth of the Missouri. The table on p. 86 gives the highest stages reached at numerous points during the period 1872 to 1893. It embraces one station (Hermann) on the Missouri River and one (Paducah) on the Ohio River. The duration of the floods above bank-full stage is also given for many of the stations. The locations of these gauges are shown on Plate ii. An inspection of these locations shows plainly that the maximum stage at Saint Louis will be reached by a concurrence of high stages in the Missouri and Mississippi. The drainage basin above Saint Louis measures about 699,000 square miles, and the total annual discharge averages 236,000 cubic feet per second, the lowest being about 45,000 cubic feet per second, and the highest, that of the flood of 1892, 1,146,000 cubic feet per second. Plate III gives a graphical representation of the highest annual stages and the dates of their occurrence from J872 to 1893. The maximum stage of each year at the different stations is shown by a heavy vertical line. The length of this line shows the stage reached, the horizontal spaces representing two feet on gauge. The position of the line shows the date when the maximum stage occurred. The numbers indicate the year. It is evident from an inspection of this plate that in that period there has been no such coincidence of floods in the Missouri and Mis- sissippi rivers. As a rule, the floods of the Missouri come consid- erably later than those of the Upper Mississippi. The greatest floods at Saint Louis, during the period under consideration, occurred in 1883 and 1892. Both of these came from the Missouri. These stages were exceeded in 1844, 1851, and 1858. That of 1844 was 5 feet higher than any other well-authenticated flood. It is said that both the Upper Mississippi and the Missouri rivers were extraordinarily high at the same time. This may be considered, then, the maximum pos- sible stage at this point. Since that time the conditions have been very materially changed in many ways, so that the stage at the present time, which would be equivalent to the discharge at the maximum of the flood of 1844, would be difficult to estimate. The flow at the present time is re- stricted to a narrow channel, while in 1844 it covered the bottom from bluff to bluff a distance of several miles. At the same time the capacity of the channel proper at high water is very largely increased by the use of present artificial embankments 84 CHICAGO METEOROLOGICAL CONGRESS. that concentrate the waters and increase their scouring capacity. As this effect varies with the magnitude and duration of the flood, it is very difficult to measure. The maximum amount is reached when the scour reaches bed rock, which it did at the Merchants Bridge during the flood of 1892. This scour was more than 20 feet deep) in some places, and the channel capacity was nearly or quite doubled. This, the greatest known flood near the junction of the Upper Mis- sissippi and Missouri rivers, does not seem to have caused excessively high water in the Lower Mississippi. The maximum stage of that year at Vicksburg was several feet lower than other years, and oc- curred several days prior to the maximum stage at Saint Louis ; hence, could not have been materially influenced by it. Referring again to Plate ii, we see that Cairo is situated at the junc- tion of the Ohio and Mississippi rivers. The drainage basin of the Ohio and its tributaries is 207,100 square miles. The Mississippi and Missouri basins above Cairo comprise 707,300 square miles, or a total above Cairo of 914,400 square miles. During the years 1882, 1883, and 1884 the average discharge amounted to 650,000 cubic feet per second. The river has an extreme range of 53 feet between high and low water. An inspection of Plate iii shows beyond question where the floods of the Lower Mississippi come from. The great floods on the Ohio begin in February and have passed on down long before the floods of the Missouri and the Upper Mississippi reach the mouth of the Ohio. The only exception was in 1875, when a flood from the Mis- souri on August 1 was joined at Cairo by a moderate flood from the Ohio River. This caused an overflow down as far as Lake Provi- dence. The maximum stage at the latter point occurred, however, some three months prior to the arrival of the Missouri wave. The floods of the Missouri and Upper Mississippi rivers have never been of such volume as to become a serious menace by themselves to the Lower Mississippi Valley, and as they never come in conjunction with one another, or with the great floods of the Ohio and its chief tribu- taries, they have but little, if any, influence on the flood planes of the Lower Mississippi River. Thus, the startling statement that an acre reclaimed from the arid deserts of Montana by means of reservoirs will reclaim another acre from the floods in Louisiana is seen to be wholly lacking in the essential elements of fact. After passing the Ohio the volume of the Mississippi River at flood stages is often increased by floods from the tributaries. The White in 1892 added 181,000 cubic feet per second, the Arkansas 400,000 cubic feet per second, and the Red River 183,000 cubic feet per second. A coincidence of floods in all of these streams may occur, and the I Stat OB«l' Bl8i ZS8 68SI SiW seer t68 9BBI ♦ear £89 9wr- 989 9' h n rs9i 2691- effli- 9881" 9^91- ZiSI 888J- 0801*- 188* <-« '♦ p9Br S88I- 6©8(- SZBI- ?88L 2681- ■ SlBi • 9881 S 9/81- 09flf il88l~ saer Z88I- 8/:9(' o$ei — 1^81 ~ 681 T^ 6881 6/8r t 0^ sgsi' '5f SigbeBt AriTiu ¥ Q/ffSsOiJr//?/V. \- j/armrig/ f/liss/esippi fiiY [ Sk touis o/ftiS/asipp/ ffi'/. i,t I ,SL,i||gil fiitiiinii ^ e a 1 w. §'-§! I si £r i § e s 40 Pac/ucah f/e/erta LaXe Pro/' 60 S fli K Cairo. (Middle Mississippi River. 46 Helena. (Lower Mississippi River.) Apr. 19. Feb. 26. Apr. 26 Aug. 8 . Apr. 6.. (B g © .Q > 60 S cS ai 41 47 45 ; 46 Apr. 15 4a Apr. 29 Dec. 31 Mar. 22 Apr. 20 Feb. 26 Feb. 27 Feb. 22-24. Jan. 26.... Apr. 19.... Mar. 9-10 . Apr. 4 .... June 24... Mar. 12 ... Mar. 4-6 . . Apr. 28 ... May 9 Feet. 39-2 1 4 I 4 5 45 4 35 4 48 8 46 2 48 3 49 3 45 I Apr. 26 Mar. 6 May II Apr. 12-14... Apr. 18-19... Apr. 30 to May I. May 3-4 . , . , Jan. 31 Mar. 31 May 14 Mar. 9 Mar. 8-9 Mar. 6 Jan. 30 Apr. 30 Mar. 21-22 .. Apr. 14-15- •■ June 28 Mar. 28-30 . . Mar. 26-28 . . May 11-12 .. May 25 O Feet. 39-0 40.0 45-8 42.4 44.8 41.8 38-7 37-2 43-7 43-7 47.2 46.9 47.0 40.7 48.1 46.4 42.8 34-1 47-7 44-7 45-7 48.0 43-5 O es « ® 4, .0 ^ at sSs 9 03 CO 25 FLOOD PLANES OF THE MISSISSIPPI. Table of highest annual stages, etc. — Continued. 87 Year. Lake Providence. (Lower Mississippi Kiver. ) Red River Landing. (Lower Mississippi River.) O C8\S v. c O C5 .a JO » 5, all S oi m 60 O © 2 ® S 2 03 3 c8 OJ Z Carrollton, La. (Lower Mississippi River.) O 2 2 * S c3 n 1872 1873 • 1874 1875 • 1876, 1877 1878, 1879 1880. 18S1 1882 1883 1884 . 1S85, 1886, 1890 . 1891 1892 1893 May I .... May 28 . . . Mar. 21-23 Apr. 19-20. Apr. 12-14. May 6-7 . . Mar. 22-24 Feb. 14-16. Apr. 3 . . . . Mar. II ... Miir. 20 ... Mar. 11-14 Mar. 23-24 May 10- 1 1 May 7 . Mar. 26 Apr. 24-25 July I , Mar. 15 Mar. 31 to- Apr. 4. June 2 May 16-17 •• Feet. 35-1 36. 1 37-4 37-3 37-9 35-8 35-8 36.0 38.0 36.2 38-3 36-5 38-4 35-5 37-9 38-0 38-1 29.4 41.0 41.0 11.9 41.8 37-4 15 o 102 70 83 May 6 . . June 12. Apr. 16 . May 3 .. May 15 . .., June 1-3... Mar — Feb. 19-20.. Apr. 22-24., Apr. 6-9 Mar. 27 :\Pr-9 Mar. 29-31 . Feb. 5-6. . . . May 31 Apr. 8 Ai)r. 30 . . . , Mar. 13-15 . Apr. 23 Feet. 39-4 39.0 47.0 40.4 45-4 40-5 Apr. 26 to May 4. June 27 June 24 35-9 44.0 40. 1 48.5 45-2 47-3 42.0 41.9 43-0 41.7 33-9 48.6 45-5 48.9 47-7 75 101 70 92 May 6 June 3-4... Apr. 16 May 3-5, 14, 16-18. May II June 4-8... Mar. 21 Feb. 20-22.. Apr. 23-24 . Abr. 12 Mar. 27 . . . . Apr. 7....'.. Mar. iS Jan. 22-23 • May 31 Apr. 6-9 . . . Apr. 26 Mar. 13-14 . Mar. 14, 15, 16, 17-22 Mar. 16 June 10 June 23-25. Feet. 12.3 12.9 15-7 "•3 12.7 II. I "•3 10.8 14.2 12.5 14.9 15-4 15-6 13-5 13-8 14-5 14-3 "•5 16.0 i5. o 17-3 17-1 80 i9§ 147 119 59 74 56 37 o 136 88 CHICAGO METEOROLOGICAL CONGRESS. O ^ b 1 Uhr, « 1 B t*-" n V 7 ON CO »J lO fOOO O I> »0 CO O lO vO o t^io voce in "T* .Sr:. S'S Sa ^ iS)!5 !?. 00 00 t^ 00 4) « O **- 1 4, « ■W^co S'S'O t- $ c 0-° 08 „• 5 ^ row f^-^ »-' i/^-o s ^ ^ c^ 00 p 00 # o 00 ^ GO ; CO ^" 0^ to d CO «" CO oc ' 00 •^ -^"!' S .<8; ^ A^» ^ 00 00 CO' a GO u 00 -^#"^K t^oo 00 r^ #-^ 00 c Jx ^'k^^si ^ sA- /= 00 00/^ CJN s -f(^rC^i?(St^ •/) .OQ0^C IT; fO"^ lO 00 o jr^r ~ oD .'^r' r^.<~» oc r^t^r^ t^ oooo_t^ r» > o m% S 'oS 00 t^ ol CO f^ f i CO ~ t^ CO t^ ^ t^r _ ~ «^ 1^. I-, r^ r ^ r^r^jr^ .«^ 00 r* r^ t^ IS 2? fi-^S&^t^S f ^ « ~ »r <^ ~ ,A ~ o^ .A 1 ^ t^ t^ t^ t^. r-. t^ 1^» t^ 1 >* CO 0000 0000 ot CO 0000 00 00 00 CO CO « T3 O >. ^ !« 5 -8 o o o o o c o o c o coo o s d 3 a z I.' . p, V- N N M Cv N O o M O rf C4 c3 0\ 00 Ot OOOO OC 00 a\ o^ o> Q\ O'CO CO <0 00 0000 0000 oc oocooc 00 OOOOOO 00 to >i V « tn . -- £ CS ^ O O -^ (^ Tj-vD N ■^ •d- ^ N o •w ION vO t^ C r^o c o VO O ON a d z „^ •^S^r ^ o !■ tj- r- ■) rl-^ «5 ^ r)--«- CO s » OQ ■C n Wji^ . ■^ 00 CO ™ -^ ■* oc i^r^ CO o CjNTi-r^ "Ir" a O •* M pooo a « >o cs 1^ ONCOTJ- r^ — Dm* s,^ l/>t^ rh-^ (N COvD t^ CO C^ CON CO >-■ N •*■«• f ^ r»- -^ CO -^ T(-T»-CO S" ON 00 N •& m '^ (X> o cc 00 rr ■^ vo 2. N ON ° 00 o> o» - _ ^M 00 00 00 0000 00 00 7 ^ 00 00 oc >o 1 n c ^ J s as fefa s<^ -^g;:^ < ^ a> a> d 2 3 >-» so 00 o lor^ c o o o lO O t».lO m 5 »' '^ lOO N - VC " -"S-O- o NOOO ■<* CO a ^ "^ M vo t5- ^ 1 cc 6 •-' c> 00 CO 00 fs. ; ? *, N N rO lOlO t^ ■) •<* m -T -^ •a--* lo o _; VO I^ vO ^ "TO ^\0 f> t^lrt'Jj- 00 NO >0 N CO a) o — .» « 00 00 t^ 6\ c 6 r^oo ^ ION M d wxo«*- ! C5 > > . © . :o3§ * a) S : M : : c : c d o • S «; o g m J5 •.t^TS :1- 3 :•=> w. c 1 c c e; s a; 1 c 5 o J E a a 3 'o a E i OS (U 0! Z«a3 c o N 00 60 60 S E O o 2 £ 5 I M) 60 5 13 o o S CO 5 r LP] ■,.' '-^ • .'389. }\MA/^^., JV, xAAK\ TV Ay f' '/ i e /V^V^"*'-V.^/^'\__ >v^\ /-xT-l -BAh'K-rUtL-STAGt - ^|;yV.,VA„^Ar^A_^ vv ^ V V . IVAiX V^'A/^''Va>v'-'^- VI ■yvjv '\y \ " ^^ ^-^-^ ^ ^ i8l5. 1844. 1850. 1851. 1858. 1859. 1862. 1867. 1868. 1869. 1870. 187 1. RIVER STAGE PREDICTIONS. Table of high water prior to 1872. 89 Year. Saint Louis. Cairo. Date, j Stage. Date. Stage June 28 June June .\pr. May May July Apr. Mar. Feet. 36-4 41.4 36-7 37-1 31-4 28.2 24.2 29-3 26.2 21.8 Apr. June 21 May 7 May 2 Mar. 21 May 19 F^t. 51.6 47.6 49.6 46.5 50-8 51-0 45-6 Memphis. Date. July — May 14 Mar. II June 23 May 12 Stage. Feet. 32-7 33-0 33-4 33-0 34-0 33-9 Mar. 26 33-9 Helena. Date. May Stage. Feet. July 2 Mar. 22 43-1 42.2 42.8 39-8 44.6 43-6 46.4 45-8 Vicksburg. Natchez. Year. Date. Stage. Date. Baton Rouge. Stage. Date. Carrollton. Stage. Date. Stage. 1809. 1811. 1813. 1815. 1823. 1824. 1828. 1844. 1850. 185:. 1858. 1859. 1862. 1867. 1868. 1869. 1870. 1871. Feet. June 26 June 4 June 26 Apr. 21 Apr. 27 46-3 46.1 47-0 46.9 48.2 51- 1 49.0 May June June June May May Mar. July Apr. June May Feet. 46.9 47.0 48.2 49.2 48.3 47-8 48.8 47-9 47-3 47-1 47-8 49.0 49-9 47-9 43-9 46. 1 44-3 43-8 Mar. 15 Apr. I May 6 Feet. 34-7 33-9 34-5 34-5 34-5 35-0 36.1 Feet. Apr. Jan. 21 Mar. 27 May 10 May 4 15-2 14-5 13-8 15-4 15- 1 15-6 15-9 34-5 34-5 15-4 3.— RIVER STAGE PREDICTIONS IN THE UNITED STATES. Thomas Russell. The river service of the United States Weather Bureau has 191 river gauges, mostly at large cities on the principal rivers throughout the country. A record is kept of the daily stages of ihe water in the interest of low water navigation and for flood warnings. Besides the Weather Bureau gauges others are maintained along the Mississippi and Missouri rivers by the Mississippi and Missouri River Com- missions in the interest of river improvements that are being made. A river gauge consists of a plank about a foot wide and of sufficient length to include the range of water from low to high water, and is marked to feet and tenths of a foot. It is fastened to a bridge pier, where one is available, or it may consist of a narrow strip of a stone pier dressed down to a smooth surface to receive the marking and numbering. Where there is no bridge pier available, a gauge is made 90 CHICAGO METEOROLOGICAL CONGRESS. of heavy timbers, 6 by 12 inches, laid along the incline of a river bank, with a strip of iron fastened along the top for the marking. A gauge is placed with the zero of graduation at the level of the lowest water as near as possible. The marks indicate vertical heights of the water surface above low water. The gauge readings are called stages. The stages read daily at 8 a. m. are telegraphed to various places interested in information as to the stages of rivers. At a number of the larger cities throughout the country a river bulletin, in connection with the weather maps, is issued daily from the Weather Bureau offices. At high water when there is danger of a river overflowing its banks the observations of stages are of interest to districts liable to be flooded. To places where definite information of the extent of a coming high water can be given warnings are sent by telegraph. The highest water in a freshest, or the crest stage, occurs first toward the head waters of a river. After a flood wave forms there is a progressive motion of the crest down stream at the rate of three or four miles per hour. This renders it possible to form some idea of what the highest stages of water will be along the lower course of a river from the stages along the upper course. Better predictions of high stages can be made the greater the length of record on which to base a rule for prediction. Accurate predictions of river stages at low water are not possible. Where the discharges of a river for low stages are known, that is, the quantity of water passing through the river for different stages near low water, estimates can be made ahead of stages below which the river will not fall ; but the least fall of rain after the prediction is made makes the river rise at low stages very rapidly. At high water predictions of stages are made in various ways, depending on the nature of the rivers. In the case of two places on the same stream, the gauge readings are more or less closely dependent, according as the distance between them is less or greater. The gauge readings follow each other more closely in a rise the less the quantity of w^ater coming into the river from the drainage area between them. Predictions of the lower stage from the upper one can be made more accurately the less the propor- tion of the drainage area between the two places bears to the whole drainage area above the lower place. The character of a river varies greatly along its water course as to slope and width. Though two places on the same stream, a hundred miles or so apart, may have nearly the same quantity of water pass- ing them, the stage at one of them may be twice as high as at the other, the difference being made up by the greater width of the river or the greater velocity of the water at the one as compared with that of the other. At Louisville, for instance, on the Ohio River, 132 RIVER STAGE PREDICTIONS. 91 miles below Cincinnati, the drainage area above it is 84,600 square miles. The drainage area above Cincinnati is 71,300 square miles. The record of stages shows that the highest water at Louisville occurs about one day after the highest water at Cincinnati. By taking the means of groups of crest stages at Cincinnati for stages about five feet apart, and the means of subsequently occurring crest stages at Louisville, the following corresponding stages, in feet, for the two places are obtained : Cincinnati... 40 45 50 55 60 65 70 Louisville 17 20 26 32 38 43 46 This table is used for predicting the stage crest at Louisville when the highest water at Cincinnati is known, or when it can be estimated closely from previously occurring high stages at points above it. For a place where a rise in the river is the result of rises in com- paratively large tributary rivers, the best method of deriving a rule for stage prediction is by the comparison of the rises at the place with the preceding rises at places on the streams above it. The prin- ciple on which a rule for prediction is derived in such a case is as follows, in the case of Cairo. 111., for example: At Cairo, 111., near the mouth of the Ohio River, a rise may be the result of a rise at any or all of the following places: at Saint Louis, on the Mississippi River, 168 miles above the mouth of the Ohio River ; at Mount Car- mel. 111., on the Wabash River, 178 miles above Cairo; at Evansville, Ind,, on the Ohio River, 183 miles above Cairo ; at Nashville, Tenn., on the Cumberland River, 215 miles above Cairo ; at Johnsonville, Tenn., on the Tennessee River, 140 miles above Cairo. The drainage area above Saint Louis is 699,000 square miles. Th3 quantity of water passing in the river at the lowest stage is 48,000 cubic feet a second; at the highest stage, which is 36 feet, 1,146,000 cubic feet a second. Above Mount Carmel the drainage area is 26,000 square miles, the discharge at the lowest stage 14,000 cubic feet a second, and at the highest, 28 feet, 220,000 cubic feet. Above Evans- ville the drainage area is 99,700 square miles, the low water discharge is 60,000 cubic feet a second, and at the highest stage, 49 feet, about 660,000 cubic feet a second. The drainage area above Nashville is 11,600 square miles, the low water discharge is 7,000 cubic feet a second, and at the highest stage, 58 feet, 160,000 cubic feet per second. Above Johnsonville the drainage area is 36,700 square miles, the low water discharge is 33,000 cubic feet a second, and at the highest, 48 feet, about 450,000 cubic feet. At Belmont, Mo., on the Mississippi River, 20 miles below Cairo, the low water discharge is 176,000 cubic feet a second, and the high water discharge, corresponding to a 52-foot stage at Cairo, is about 1,603,000 cubic feet. 92 CHICAGO METEOROLOGICAL CONGRESS. A rise at one of the up-river stations has more effect in producing a subsequent rise at Cairo the greater the length of time the higher stage lasts at the up-river station. The continuation of the higher stage beyond three days has no effect in increasing the rise at Cairo For a less continuation than three days, the rise at Cairo is a pro- portional part of the greatest rise that takes place for a three-day continuation of the high stage. From a consideration of the slopes of the river-surfaces between Cairo and the up-river stations for different stages at the various places from low to high water, and the varying cross-sections and depths for the different stages at the various places, the ratio of a one-foot rise at the various places to the corresponding rises at Cairo is derived theoretically, as far as the data will permit, taking into account the extent of cross-section and the velocity of water as af- fected by different depths and slopes. A comparison of the theoretical rises thus obtained with the rises actually observed in cases for which there are records, gives a factor for each place for certain stages. Only a few of the possible cases that can occur have ever been observed. The record of stages at Cairo and the up-river stations is too short, as yet, to furnish cases of all the possible variety of combination of freshet wave crests from the various rivers which produce a high water at Cairo. For the possible cases which may occur in the future, but of which there are no observations as yet, the theoretical value of the rise found as described is multiplied by a factor derived for the stages at which there have been actual observations of rise. In this way tables are prepared which show the relation of a one-foot rise at the various places to the subsequent rise in three or four days at Cairo, that being the crest-wave time between Cairo and the various places. The rise at Cairo is taken as the sum of the various com- puted rises at the five places. In case of a fall at any of the places instead of a rise, it enters the sum with a minus sign. The stage that will prevail at Cairo can be estimated six to seven days ahead from the stages at Cincinnati, Chattanooga, and Saint Louis, with allowance for the water coming out ©f the Cumberland and Wabash. But as the cross-sections at Cincinnati and Chatta- nooga are not known, the rule for prediction of stages has to be based on the comparison of actually observed rises. In cases where the discharges and cross-sections of rivers at places are not known, some idea can still be formed of the relative impor- tance of different tributaries in causing a rise at a point on a main stream, provided there is a long record of stages with rises at the lower point due to rises sometimes in one of the tributaries and RIVER STAGE PREDICTIONS. 93 sometimes in another. This permits of estimating the effect of each separately. A rise at a high stage of a river has more effect than an equal rise at a low stage in producing a rise at a point lower down the river. On the other hand, the higher the stage at the lower point the less the effect of a rise at an up-river point in producing a rise below. The products of the rises by the mean stages during the rises are taken as comparable throughout the range of stages at the place. For very high stages this does not hold good. Where a river over- flows its banks and becomes miles in width, very great rises at up- river stations have very little effect in producing a further rise below, and it is impossible to estimate effects in such cases. In some cases the extent of the drainage areas above up-river gauge stations is taken into account in devising a rule for predicting a high-water stage at a lower point. In a case of this kind at Pitts- burg, the prediction is based on the stages at the following places above it : Sq. miles. Oil City 4,526 Brookville 400 Confluence 782 Rowlesburg 886 Weston 140 Johnstown '. 711 The effect of a rise at a place in producing a rise at Pittsburg is taken as proportional to the square root of the area above it. The whole area above Pittsburg is 17,000 square miles. The areas above the six places comprise 7,445 square miles of the area above Pitts- burg. The rise at Pittsburg multiplied by the mean stage during the rise, and by an unknown factor for a number of selected cases of great rise, are placed equal to the sums of the rises at the six places above, weighted according to the square root of the drainage areas above them, the unit of area being taken as 1,000 square miles. From these the value of the unknown factor is derived. With the factor a table is prepared which gives the highest stage at Pittsburg when the rises at the upper gauge are known. Gauge readings at a place made on successive days, or at intervals a few hours apart, during a rise are of some service as indicating how high the water may be expected to go. The characteristic of a rise for most places is that the rate of rise, small at first, gradually increases as the rise continues, until a maximum rate is attained, and then diminishes until it becomes zero at the crest stage. The characteristic variations in rate of rise vary greatly in different places, depending largely on the slopes of the ground over the drain- age area and on the customary distribution of rainfall. As a rule, the characteristics of a rise are more permanent or more nearly alike in 94 CHICAGO METEOROLOGICAL CONGRESS. different rises the greater the drainage area above a place. At Cin- cinnati, for example, on the Ohio River, the rate of rise begins to diminish on the average about three days before the crest stage is reached. This is, therefore, a useful criterion in judging how long the river will continue to rise. The observed rate of rise can be used to estimate a stage for some time ahead. This is, however, mostly an uncertain method, and only to be used where other methods are not available. In some cases, where there is only a single gauge on a river and the drainage area above it is small, the reliance in making predic- tions must be wholly on observations of the depth of rainfall over the area. Definite stage predictions are out of the question in such cases, and the most that can be said is that a very high stage will prevail when the rainfall over the area is seen to exceed a certain amount for the average of a number of stations. As an example of this it requires, at the least, a rainfall of 3 inches in less than three days over the 15,000 square miles of drainage area of the Potomac River to raise the stage at Harpers Ferry to 34 feet, which corresponds to 12 feet at Washington, D. C, twelve hours later. Over the Savannah River drainage area of 7,500 square miles it requires a rainfall of 5 inches in three days to cause the river to rise at Augusta, Ga., to the highest stage known, which is 38.7 feet. 4.— METHODS IN USE IN PRANCE IN FORECASTING FLOODS. M. Bauinet. Historical. — In requesting M.Georges Lq jnoine, In genieur en chef des Pouts et Chaussees, Paris, to present a paper on the methods in use in France in forecasting floods, for the International Congress of Meteorology to meet at Chicago in August, 1893, the Honorable Chair- man of the Section devoted to Rivers and Floods kindly remarks that the idea of predicting the level of rivers originated in France, and that questions of this nature have been treated there with more care than elsewhere. It was in 1854 that the illustrious Belgrand organized a network of permanent hydrometric observations in the basin of the Seine. He derived, a short time after, a preliminary rule for the forecasting of floods at Paris ; about the same time similar investigations yielded appreciable results on other French rivers better naturally disposed, without doubt, to facilitate the forecasts. M. Camoy tried to predict the floods of the Loire at Orleans and Tours from observations made at points above and below as far as the confluence of the Allier, below which the Loire receives no important affluent throughout 300 kilo- meters of its length. M. Poincar^ did the same for the Meuse, the FORECASTING FLOODS. 96 situation of which is similar, from the place where it leaves the De- partment of the Vosges to its entrance into the Ardennes. The relation of cause and effect which attaches to the swelling of certain rivers in the principal stream of which they are tributaries must have previously attracted the attention of some bright minds. It was known that heavy rains, especially in mountainous regions, could, by their accumulation and the simultaneousness of their pro- gressive flow through the plains, produce inundations at points lower down. But the possibility of analyzing in every case these complex phe- nomena and extracting from them information of practical value had not been demonstrated before the investigations of Belgrand. His fundamental work (La Seine, regime cle la pluie, des sources, des eaux courantes, Paris, chez Dunod, 1873) laid the foundation of a new sci- ence, hydrology, of which the forecasting of floods is but an interest- ing application. The affluents of the Seine coming from permeable soil (oolite, chalk, limestone), rise more slowly than the others. Their slopes are almost always more feeble ; except in certain exceptional circumstances, the absorption of water by the ground is greater ; the superficial flow at the start is a matter of very great importance. These considerations, in connection with very complete geological investigations, have, in predicting the maximum of a flood at Paris, permitted of neglecting the movement of the upper part of the river above the confluence of the Yonne, in spite of the extent of the basin, and that of the Aube in the Jurassic and Cretaceous formations. The Yonne, the Marne, and their principal affluents, are all that it is necessary to take into account. The time of propagation of the wave crest. — The rapidity of the flow of water on the surface of impermeable ground does not permit of making forecasts in time to be of use unless the observations that serve as a basis are made at a great distance above. Even as far below as Paris, where the Seine, full formed, is far from having a torrential regime, the interval of a wave crest at two stations, with no important lateral valley intervening, corresponds frequently to a velocity of four kilometers an hour, if not more. In 1854 telegraphic communication was not so perfected as to-day. A whole day could easily be lost before advices could be received from the most interesting stations. This was the reason why the principal points of observation were chosen by Belgrand toward the limits of the higher upper imper- meable lands, as indicated in the Manual Hydrologique du Bassin de la Seine (Imprimerie Nationale, 1884, p. 50). Prediction of floods by rises. — It happens frequently that several oscillations close together in a water course in the upper part of the 96 CHICAGO METEOROLOGICAL CONGRESS. region in question correspond to a single continuous great rise of the Seine in the vicinity of Paris ; it is a multiple wave of which the maximum does not depend alone on the highest stages prevailing at the points above. The successive waves unite below, where their velocity slackens, and where there is thus a very great accumulation of water. From this has arisen the practice, for the basin of the Seine, of considering the relation of rises "of which the name alone is scarcely a definition. Even in the case of simple waves, produced by a single group of rains, the rise (or the difference between the level of the water at the beginning of the rise and when the highest point is reached) has the advantage of being independent of the stage whence it starts, if it is not artificially influenced by a movable dam which is finally lowered. Certain rises may, moreover, be taken as representative signs or evidences of the hydrological phenomena of which a neighboring region is the theater. It is in this way that in the rule for announc- ing floods in the Seine at Paris Belgrand was able to make use of the Aisne at Ste. Menehould and the Aire at Vraincourt, even though the waters of these two rivers run into the Oise and have not, conse- quently, any actual influence on the stage as read from the gauge on the Austerlitz bridge. For a similar reason, in order to take into account the great superficial extent of the basin of the Marne, in place of double the rise taken at a single point of the river conven- iently chosen, the formula for prediction at Paris contains the rise of the Marne at Chaumont and St. Dizier, one of which precedes the other except for the changes due to the intermediate tributaries. Whatever may be thought of the principle of this method, it is in any case justifiable by the excellence of the results; for the three great floods at Paris have been predicted one or two days in advance within a few centimeters of the correct stage, notably those of March, 1876, and February, 1889. The same processes have been* employed elsewhere by M. G. Lemoine in predicting the floods of the principal tributaries of the Seine, as may be seen in the Manual Hydrologique mentioned above (pp. 51-55). The prediction of floods by rise is moreover well adapted for tak- ing into account certain necessary corrections due to accessory influ- ences ; it is susceptible of improvement. As, for instance, when at a station for which predictions are made a flood occurs when the stage is falling, that is to say, for a sufficient length of time before the river has returned to the normal level of the season, the rise calculated by the ordinary formula ought generally to be reduced in a certain proportion ; a part of the water is used in a manner to overcome the tendency toward lowering, or is absorbed by the drawing effect of the preceding movement. The rise to be predicted at a lower station may moreover be a dis- FORECASTING FLOODS. 97 continuous function of those at points above ; it is therefore highly probable that when the river rises above the level at which in a number of places the wetted perimeter of a cross-section increases sharply for a slight increase of height (flood levels) these anomalies are less appreciable than at principal stations, where the phenomena occurring in a great basin proceed more regularly ; for reasons of the same nature they are less to be feared than more important floods. If the announcement of slight changes is of any interest on second- class rivers, floods may be classified by families according to the ini- tial stages or the magnitudes of the rises and a special formula may be used for each kind. This has been tried recently for some stations in the basin of the Oise. Announcement of floods by absolute, stages. — The study of stages, very extensive in the basin of the Seine, of which the hydrologic compli- cation is sufficiently great, is not so generally in use on the other French rivers where the situation is different. On the Seine itself where, on the tributaries, without giving up t^e method of predicting by rises which generally permit of making predictions a sufficient length of time ahead, it has been possible in the last fifteen or twenty years, especially, to utilize the exten- sion of the telegraph for obtaining in time information as to the stages occurring successively at upper stations so as to make them of use for predictions at places lower down, as Paris or Mantes, and to draw from them conclusions useful for points along the lower course of the river. Inspector General Allard, former President of the Commission on the Forecasting of Floods in the Ministry of Public Works, has given, in a special work, a certain number of second- ary rules determined in this manner (Annales des Fonts et Chaussees, 1889, ler sem., vol. xvii, pp. 689 and following). When a sufficiently great distance separates two stations between which the course of the water considered does not receive any im- portant tributary, or if the velocity of propagation of floods between these two points is small, the prediction can be made by the aid of a graphical process in which (1) the abscissas are the maximum stages occurring at the upper station in a certain number of previous floods, (2) the ordinates are the maxima corresponding to the lower station. The extremities of the ordinates give generally a regular curve which permits of finding the highest stage to be predicted from the corres- ponding abscissa, the stage at the upper station. An analogous graphic method was proposed in 1882 by M. Lavoinne, in a more complicated case, to study the relations between the maxima of the Seine at Rouen, that of the Seine at Mantes, and the level of the sea at Havre about thirty-six hours in advance. The stage at Havre was taken as abscissa and that at Mantes as ordinate, and along- side of the point thus located was written the stage that resulted at 7 98 CHICAGO METEOROLOGICAL CONGRESS. Rouen. If there was a constant relation between these three variables, all the points of equal stage ought to be on a regular curve, the pro- jection of a line of level on a surface conceived to give in space the relation in question. This proceeding, devised anew by M. Mazoyer for the prediction of floods of the Loire in the vicinity of Nevers (Annales des Fonts and Chaussees, 1890, 2d sem., vol. xx, pp. 451 to 511), is modified somewhat: one of the variables is not always the height of water actually observed on a gauge at an upper station, but the mean of the maximum stages indicated by the observations of a certain number of tributaries whose relative influence can be taken into account by the aid of proper coefficients. In the two cases in question, the graphical processes can be replaced by tables of single or double entry, as has been done by M. Jollois for the upper Loire. (Annales des Fonts et Chaussees, 1881, ler sem., vol. I, pp. 273 to 322.) It seems useless to dwell here on the investigation of formulas and unknown coefiicients (by trial or by the method of least squares), in fine, on the graphic representation of the relation found in num- bers by means of the processes indicated in the Nomographie of M. d'Ocagne (Gauthier Villars, 1892, pp. 65 to 81). This latter method in particular, is not yet completely studied, and its practical appli- cation in hydrometry can not be pronounced upon immediately. In these investigations the important point is to be satisfied as to the conditions indicated for great floods ; it is rarely that the others have an equal interest for dwellers along rivers. j| Prediction of floods from rains. — At the present time it is possible to speak affirmatively as to the possibility of effectively using observa- tions of rainfall for predicting the level of the water in the rivers of certain regions ; they have served as the basis for hydrological studies but do not appear to be easily usable. ( Manual Hydrologique du Bassin de la Seine, p. 50.) ■ In very impermeable basins with small extent of surface and high slopes the details of observations of rainfall permit of appreciating more readily than elsewhere the probable circumstances of water flow. It is precisely in regions of this kind that it is especiall}'- diffi- cult to procure in time observations of the heights of small rivers along the upper courses, which permit of eliminating the influence of the nature and configuration of the ground, its dryness, its temper- ature, or other perturbing action. In studying the floods of a very little river in the north of France (the Liane) which empties in the straits of Calais at Boulogne-sur- Mer, M. Voisin has shown that, in certain cases at least, having re- gard to these influences, one can, without passing through the inter- mediary of river gauges at upper stations, give approximate estimates of stages in time to be of use. {Annales des Fonts et Chaussees, 1888, FORECASTING FLOODS. 99 ler sem., vol. xv, pp. 464 to 510.) He has obtained since that time certain satisfactory results. Some analogous propositions which have not as yet, however, been sanctioned by any practical results, have been made by M. Tinbeaux for the Durance. (Annales des Fonts et Chaussees, 1892, ler sem., vol. iii, pp. 166 to 196.) Divers studies of the same kind appear to have been pursued by the hydrometric services recently organized in conformity with the advice of the Com- mission on the Prediction of Floods, at the instance of M. G. Lemoine for the Ardeche, the Herault, and other rivers which descend rapidly from the Cevennes to the Rhone or Mediterranean. It is beyond doubt very difficult to make numerical forecasts in the greater num- ber of cases, but it is nevertheless a good deal to be able to announce in such regions a few hours in advance the approach of an important or dangerous flood. Only two points so far seem to be established for the small drainage area of the Liane : ( 1 ) the possibility of estimat- ing the degree of saturation of the soil in a certain zone from the height of water on a gauge at a greater or less distance from a down- river station, notably at the very place from which the predictions are issued; (2) the influence of the hourly rate of rainfall. It is not immaterial from the point of view of the flow of water that a certain depth of rain had been caught in the rain gauges in a very short time or in a great many hours ; in this latter case it has a much greater chance of being absorbed by the ground or being in great part evaporated. Registering apparatus. — All the information necessary can be ob- tained by visual observations distributed at intervals sufficient for the purpose for which they are desired. The rapidity of the phenomena, however, is at times so great, especially in mountainous regions, that it is sometimes well to have, in addition to river gauges and the ordi- inary rain gauges, apparatus adapted (1) to signal, by electricity, the instant of time when the quantities to be observed reach certain im- portant values, (2) to register the details of their variations. Different French makers of instruments of precision (notably Messrs. Richard, Parenthon, and Chateau) make self-registering river and rain gauges of which the indications are of great value. The use of this kind of apparatus is gradually becoming greater; they would be used to a much greater extent were it not for the obstacles of the very high price and the cost of their maintenance. For a stream as torrential as the Durance it is almost indispensable to have self-registering apparatus at one station at least at the head waters. Prediction of floods by discharges. — In order to satisfy the desire ex- pressed by the Chairman of the Section devoted to Rivers and Floods of the Meteorological Congress, a few words must be said regarding the use of discharge observations in predicting the level of rivers. This method is not in current use in France where the gaugings of 100 CHICAGO METEOROLOGICAL CONGRESS. I water courses have only been made at a small number of places and have no relation to each other and are, in general, only slightly com- ; parable. To extract anything from data of this kind, one is especially ■ embarrassed by the manoeuvering of movable dams on the numerous ; rivers where navigation has been improved by artificial means. Finally, there does not exist on any French water course anything that can be compared to the great work done for the Elbe and its tributaries in Bohemia under the direction of Prof. Harlacher of the Polytechnic- Institute at Prague. It was only after eighteen years of patient in- vestigation that he succeeded, in 1881, in perfecting his method of prediction by discharges, published over his signature and that of Prof. Richter in the month of December, 1886 (Zeitsch rift far Bauwesen, 1887). There is often difficulty in choosing two or three stations along head waters, such that the sum of their discharges, increased in a certain proportion to take into account the additions from second- ary streams below, produce with sufficient exactness the discharge in a determinate time at the station for which the predictions are to be made. If this correspondence is attained, might not one find an approximate relation by a simpler application of the abso- lute stages or the rises, without passing through the intermediary of the gaugings? To obtain the greatest chances of success, the dis- charges ought to be well determined in connection with the observa- tion of levels at upper points ; there ought to be a great variation of height without any notable change of volume in the water passing per second; this supposes that the valleys are embanked. At the same time an appreciable error in the discharge ought not to involve at the lower station any great uncertainty in the corresponding height of water ; this case is presented only in a flat valley with a large, broad bed. These conditions are not found together in France, where the water courses have for the most part a regimen too variable to permit of the method in question being applied advantageously. GENERAL ORGANIZATION FOR THE PREDICTION OF FLOODS IN FRANCE. Conclusion. — In what precedes there has been no question as to the dissemination of warnings, for transmission is not directly bound up with the technical work of prediction. Scientific progress cannot be obtained by decree, admitting that in many other cases it is possibly realizable. The important results obtained by Belgrand for the basin of the Seine preceded all corresponding administrative organization. Yet the investigations to which local services ought to devote their ener- gies in order to make useful predictions are often long and difficult. The persons charged with them give them special attention when they expect to find a way to derive satisfactory rules through skillful com- binations, and when the labor and ingenuity bestowed in such studies RIVERS OF SIBERIA. 101 do not risk passing unnoticed. The Ot)mmi8sion on Prediction of Floods, instituted in 1875 under the Ministry of Public Works at Paris, has certainly played from this point of view a very important role. It has organized in a permanent, definite manner the service of observation, the preparation of warnings, and their distribution throughout almost the whole of France. The results obtained in France up to the present time have been attained without very great expense, and without the powerful means which have recently per- mitted the Central Bureau fur Meteorologie unci Hydrographie of the Grand Duchy of Baden to produce the recent magnificent publica- tion on the Rhine and its affluents. With more modest resources, the hydrometric services of the different French basins have probably not yet said the last word. 5— THE FOUR GREAT RIVERS OP SIBERIA. Franz Otto Sperk. The whole northern portion of Asia that bears the name of Siberia, extending from the Ural Mountains in the west to the waters of the Pacific Ocean in the east, i. e., approximately from the fiftieth to the one hundred and fortieth meridians east of Greenwich, covers (according to the computation of Mr. Strelbitsky) an area of 231,637* square miles, or 12,757,864 square kilometers, not including the islands. This vast territory is intersected by four enormous river basins. Three of these rivers, the Obi, the Yenisei, and the Lena, receive their waters from the Altai and Saian mountains and their numerous spurs, and empty into the Arctic Ocean ; while the fourth, the great Amoor River, discharges its waters into the Gulf of Tartary of the Pacific Ocean. I shall not speak of the rivers of the extreme north of Siberia, such as the Piasina, Khatanga, Olenek, Yana, Indighirka, Kolyma, Anadeer, and others, although some of these are very large. The dimensions of the four principal river systems of Siberia are as follows: (1) The river Obi has a length of 701.5 miles, or 5,206 kilometers; its basin comprises an area of 54,118 square miles, or 2,980,646 square kilometers. (2) The river Yenisei, with the Angara, Lake Baikal, and the Upper Angara River, has a length of 540.5 miles, or 4,011 kilometers; the basin extends over an area of 37,257 square miles, or 2,051,996 square kilometers. If, how- ever, the Selenga River is taken as the beginning of the Angara, both the length and the area of the basin would be considerably increased. (3) The Lena has a length of 619.7 miles, or 4,599 kilo- meters; the area of its basin is 42,743 square miles, or 2,354,203 * The Prussian mile seems to be used throughout this paper. The English equiva- lent is 4.66 statute miles. The temperatures given are in centigrade degrees. — Editor. ) 102 CHICAGO METEOROLOGICAL CONGRESS. square kilometers. Finally,'*- (4) the Amoor River is 603 miles, or 4,478 kilometers, long ; and the portion of its basin belonging to the Russian Empire covers an area of 18,300 square miles, or 1,007,901 square kilometers. There can be no doubt as to the great importance of these rivers for the climate of the country. Thus the annual covering of these rivers with ice and their delivery from the ice must exert a powerful influ- ence on the temperature of the locality, for the formation of the ice absorbs a large amount of heat, and the cover of ice over the rivers changes the conditions of evaporation and radiation ; again, the thaw- ing of the ice appreciably lowers the air temperature of the spring months. Thus, while the rivers are, so to speak, a product of the climate of the country, they may themselves serve, apart from direct meteorological observations, as an indication of the greater or less amount of precipitation, and their changes of level may allow infer- ences as to the annual distribution of the precipitation. The exist- ence of the mighty rivers of Siberia, with their numerous powerful and extensive tributaries, shows clearly that Siberia is not deficient in precipitation ; and the considerable changes of level taking place in these innumerable rivers at different times indicate that this rather large amount of precipitation is not uniformly distributed over the various parts of Siberia and through the seasons. In general, pre- cipitation is greater in the west in summer, in the east in winter. Unfortunately, the questions that meteorology might raise concerning the Siberian rivers have, as yet, hardly lieen seriously considered. Besides the work of Dr. Rykatschew " On the Opening and Freezing of Rivers," and that of Dr. Stt^Hing "On the Discharge of Water of the Angara," some scanty material, not yet scientificall}^ elaborated, is to be found in various works concerning thg discharge of rivers and allied problems. The present brief sketch is based on all the material I have been able to collect, and on my personal observations and recollections from an eighteen years' residence in Siberia. I shall begin with the freezing and opening of the rivers, these phenomena accompanying the transition from summer to winter, and again from the cold to the warm season. While the times of the freezing and opening of the rivers vary within rather wide limits, these limits are more narrow in Siberia than in European Russia. I give below a table derived from the results of Dr. Rykatschew, and exhibiting the mean and maximum deviations from the general means for the separate periods : RIVERS OF SIBERIA. Table sJiowing mean and maximum deviations. 103 For a 20-year period. Opening. Freezing. Free from ice. Mean. JVIaximum. Mean. Maximum. Mean. Maximum. o ± i-i ± i.c — 3 ±2.1 ± 1.6 ±2.3 ±4 ±3 6 ±2.1 ± 2.6 ±3-3 ± 4 River Yenisei at Yeniseisk 8 For a 30-year period. Opening. Freezing. Free from ice. Mean. Maximum. Mean. Maximum. Mean. Maximum. ± 0.8 ±0.5 ±1-4 2 ± I ±3 ±1-7 + 4 ±2.1 (1) ± 1-5 + 4 River Yenisei at Yeniseisk River Angara at Irkutsk 5 1 No information. Investigation has shown generally that in the more central, and consequently more continental, portions of a country the times of freezing and opening of the rivers are subject to smaller annual variations. I give on p. 116 a table, taken from the work of Dr. Rykatschew, which shows the times at which the princii)al Siberian rivers begin and cease to be covered with ice. In this connection it must be observed that the following more extended series of observa- tions are available : A series of one hundred years only for the river Angara ; a series of eighty years for the Obi at Barnaul, and for the opening of the Yenisei at Yeniseisk. The observations for most of the other rivers extend over small periods of time. As the phenomena of the freezing and opening of the rivers are closely connected with the time of first occurrence, as well as with the duration of air tem- peratures below zero in the fall and of temperatures above the freez- ing point in the spring, I have also given in the table the following mean results : ( 1 ) The time of the first occurrence of a mean temper- ature of zero (for twenty-four hours) ; (2) the interval from the first day of zero temperature to the day of opening and freezing, respec- tively ; (3) the number of days between the mean zero temperature of the spring and the fall. It would also be of interest to have data concerning the sum of temperatures below zero required for the freez- ing of the rivers, but we have such data only for the Angara, for which Dr. Woeikof derives the figure 99.8°, while for the Neva only 42° are required. It appears from Mr. Rykatschew's maps, illustrating the simulta- neous opening and freezing of the rivers, that the earliest opening of 104 CHICAGO METEOROLOGICAL CONGRESS. Siberian rivers begins about the 2l8t of April in the southern portion of west Siberia, between the cities of Semipalatinsk and Barnaul, From there it moves to the upper part of the Yenisei, beginning later toward the east, or, if simultaneous, farther south. About the Ist of May the opening of the rivers already extends to the middle of the course of the Amoor. On the 21st of May the opening, beginning in the west near Berezov, extends eastward, bends at Yakutsk somewhat to the south, and turns on the shores of the Okhotsk Sea abruptly south- west towards Nikolaifsk on the Amoor. The Yenisei, in the lower part of its course, between Toorookhansk and the mouth of the river, throws off its covering of ice only at the beginning of June ; the same is true of the rivers Yana and Kolyma in their lower course. Toward the end of June the mouth of the Lena becomes open, and partly that of the Yenisei. But even in the month of July some smaller rivers can be found covered with ice on the Taimyr Peninsula. According to the means deduced from the ol^servations, the opening of the more important Siberian rivers takes place sixteen days after the occurrence of a mean temperature of the air of zero ; for the smaller rivers the interval is twelve days. The gradual onward motion ,of the boundary of the ice covering from the south to the north goes on more rapidly in the east. In eastern Siberia, in N. 50°, it takes place in a month, the motion northward being at the rate of 10° in nineteen days, but on one and the same parallel the opening is considerably retarded toward the east in the more southern parts of the country in comparison with the northern parts, and it is evidently connected with the direction of the isothermal lines and depends on local topographical conditions. The covering of the rivers with ice, /. e., the process of the forma- tion of the ice on the rivers, is very interesting in Siberia, but, unfortunately, it has been investigated very little. It is known from the investigations of Messrs. Shchukin and Schwarz that the forma- tion of ice in the Angara, and also in some other rivers, for instance in the Olokma, takes place not only on the surface but at the bottom as well. Special mention should here be made of the Angara, as this river is distinguished from other Siberian rivers by several peculiarities. Forcing its way through the rocky shores of Lake Baikal, the Angara carries its waters, cold and clear as crystal, in rapid flow from the lake to the city of Irkutsk ; and on this distance of only about 70 kilometers its bed has a fall of 80 meters, in other words, it has an average grade of 0.43 meters per kilometer. Along this whole dis- tance the Angara does not receive a single important tributary, and represents a pure type of a lake river. From this it might be ex- pected that its level would vary but slightly. It appears, however, as we shall see later, that the height of its water level is subject to RIVERS OF SIBERIA. 106 very considerable and abrupt variations. Another peculiarity of the Angara is its late freezing, which takes place about eighty days after the beginning of frosts, at a time when the cold reaches not less than — 25° ; it occurs more than a month and a half later than in other Siberian rivers situated in the same latitude. A third peculiarity of the Angara lies in the fact that its overflow takes place not in spring, summer, or fall, as is the case with other rivers, but in winter, at a time of the severests frosts, when the river is freezing. Dr. Stelling believes that the overflow of the Angara at the time of its freezing is due partly to the diminution of the velocity of the current arising from the friction of the water on the ice crust, and partly to the nar- rowing of its bed through the ice. The latter cause is probably the principal one. It is to be regretted that no exact data are available as to the distance over which the Angara below Irkutsk is covered with ice at an earlier period than at this city. The obstruction by ice in these portions of river, which freeze at an earlier time, are the main cause of the overflows. I shall now give a brief extract from Dr. Schwarz's observations on the freezing of the Angara at Irkutsk in the ^vinter of 1856-1857 : On December 14 ice began forming along the banks; on the 18th, when the temperature of the air fell to — 30.7°, while that of the water was -|-0.03, the whole river began to be covered with ice floes, and the ice on the banks extended to a considerable distance into the river. At the bottom of the river could be noticed numerous ice crystals which would, from time to time, break loose from the bottom and rise to the surface. On December 19, the temperature of the air being — 35°, the ice crystals at the bottom disappeared, and the river continued to carry ice floes. Beginning with January 15, 1857, the water began to rise in the river, the temperature of the air being — 11.7°. On the 18th the river overflowed all the low bank near the city ; on the 19th the water rose to a height of 3 meters, and on the same day, the temperature being — 24.1°, the main channel of the Angara became completely covered with an ice sheet. Nevertheless, the overflow of the river continued to increase up to January 24, and only on the 25th the water began to fall. It must also be noticed that the fall of the water, after the overflow has reached its greatest height, takes place very gradually, the water continuing to fall for a month. Thus it appears from the observations on the freezing of the Angara that ice crystals form at the bottom, that this goes on, with interruptions, in spite of the increasing cold, and that these crystals rise to the surface in the form of laminas which freeze on to the ice forming on the surface. I add the following details as to the time of freezing of the Angara : In the year 1739 the river became completely covered with ice on January 9, simultaneously with Lake Baikal. This is a rare occur- 106 CHICAGO METEOROLOGICAL CONGRESS. rence, as the Baikal usually freezes earlier. In 1751 there was a very heavy inundation at the time of freezing, January 8. In the winter of the year 1755 the river began being covered with ice only on Feb- ruary 2 ; the ice, however, was carried away seven times, and there was hardly any period of complete covering with ice. In the year 1870, when the river became covered with ice on January 15, a large part of the city of Irkutsk and many settlements along the Angara were inundated. The same thing occurred in 1887, when the river froze on January 18 ajid 19, and the overflowing waters carried large masses of ice with them. It is also worthy of notice that, from the very beginning of frost, i. e., from the month of October, a heavy fog was constantly hovering over the Angara River. This fog disappeared only when the river became covered with ice. Returning again to the results obtained by Dr. Rykatschew, we find that the covering of the rivers with ice is subject to greater variations than the opening, and that it proceeds in the opposite order, i. e., from the northeast to the southwest. First of all become covered with ice the small rivers of the Taimyr Peninsula, as early as in September. Next, about two weekf later, such rather considerable rivers as the Piasina, Indighirka, Yana, emptying into the Arctic Ocean, begin to freeze almost simultaneously, and the boundary of the ice covering advances pretty rapidly, forming two bends toward the south and southwest, one in eastern Siberia along the Amoor the other in west Siberia toward the upper course of the rivers Tom and Omi ; an up- ward bend occurs along the valley of the Yenisei. The formation of these bends in the progress of the ice sheet on the rivers depends both on the distribution of the air temperatures and on the slow cooling of the large mass of water in the rivers. To the same cause is due the late freezing of the northern parts of the other large rivers, viz., the Obi and the Lena, In its progress from east to west the covering of the rivers with ice is retarded about ten days for every 24° of longitude, while the southward march of the boundar}- of the ice sheet, from the polar circle to the fiftieth parallel, is ac- complished, on an average, in thirty-one days. As regards the duration of the ice covering, it varies between very wide limits. Thus, at the mouth of the Piasina the ice stays three hundred days, while in southern Siberia the duration is not over one hundred and sixty days. An exception is made by the Angara, which, after leaving the Baikal, for a distance of 7 kilometers, never freezes at all, owing to the rapidity of its current, and this in spite of tem- peratures of — 40°, and of the fact that for a period of one hundred and seventy days the temperature always remains below zero. The same phenomenon occurs in the course of the Yenisei, in the narrow rocky passes of the Saian Mountains, and in a large number of small moun- tain rivers, which in some parts do not freeze at all, owing either to RIVERS OF SIBERIA. 107 the velocity of the current or to springs of warmer water emptying into their beds. In the large rivers the ice stays, on an average, nine days longer than the duration of the normal temperature of zero ; in the small rivers, only five days longer. The freezing of the large rivers takes place twenty-four days after the occurrence of a mean temperature of the air of zero ; the freezing of the small rivers occurs seventeen days after this temperature. The extremes of temperature between which the freezing times oscillate are greater than those for the open- ing of the rivers, but far more constatit. Thus the intervals between the earliest and latest openings and freezings are : For the— Openings. Freezings. Obi at Barnaul Yenisei at Yeniseislc Angara at Irltutsk Lena at Kirensk Lena at Yakutsk From the information gathered by the Polar Expedition of 1882- 1884 it may be assumed that the opening of the mouth of the Lena, in N. 70° 23', E. 126° 35', occurs on May 25, and the covering of the river with ice on October 2, so that the river is only ninety-nine days free from ice. The mean value of the interval between the times of extreme openings is a little over a month for the rivers of Siberia, and the mean interval between the extreme freezings does not exceed thirty-five days, while for the rivers of Russia the latter interval amounts to fifty-two days. The constancy of the openings and freez- ings is particularly remarkable in the case of the Lena, as this river flows through a region having an extremely continental climate. Thus, the mean duration of the ice covering of the Lena, near Kirensk, is two hundred and three days ; and in the course of the forty-two years for which there are observations, it happened only twice that the ice stayed fourteen days less, and only once that it stayed thirteen days longer than the normal duration. As regards the thickness of the ice covering the rivers, the informa- tion is exceedingly scanty. We happen to know that in the lower course of the Yenisei the thickness of the ice in severe winters will reach 2.5 meters ; and that on the Angara, at Irkutsk, on March 9, 1887, the greatest thickness was 1.14 meters, on the Baikal from 1.2 to 1.8 meters. Concerning the variations of level in the rivers, we have the scien- tifically conducted observations of Dr. Stelling for the Angara, but only for 1886-1887. It appears from these observations that the water level of the Angara is subject to considerable variations in the course of the year, and that the annual curve differs decidedly from 108 CHICAGO METEOROLOGICAL CONGRESS. those for the rivers of European Russia and of west Siberia. Thus, in 1887, the mean level of the Angara at Irkutsk (in meters) was as follows : January, 4.35; February, 3.78; March, 4.57; April, 6.19; May, 6.08; June, 5.84; July, 5.35; August, 5.14; September, 4.92 ; October, 5.06 ; November, 5.44 ; December, 5.82. These figures indicate by how many meters the water level of the Angara was below the mark established at the entrance to the Museum ; they are daily means from three-hour observations taken 7 a. m., 1 p. m., and 7 p. m. * The daily observations showed that, beginning with the principal maximum which occurs toward the end of January, the water level of the river falls pretty uniformly to the second half of March ; then, at the opening of the river, which takes place very rapidly and without overflow, a still greater fall occurs ; but from the beginning of April to the beginning of June the water rises slowly. In July the rise becomes more pronounced, and in September the level reaches a second smaller maximum, arising from the great amount of precipitation in the Baikal region. At the expiration of the rainy period the water level of the Angara begins to fall slightly, continuing to do so with slight oscillations until the period of freezing. It thus appears that in spring, /. ?., at the time of the greatest overflows of the rivers of Russia and west Siberia, the height of the water in the Angara is usually least. This is largely due to the small amount of snow in the Trans-Baikal and on the mountains near Lake Baikal, which supply the affluents of this lake with water; also to the sloiv thaiving of the snow during the cold and dry spring, and to the heavy icinds which produce intensified evaporation accompanied by dryness of the air. On the other hand, during the latter part of the summer and the beginning of fall, when in Russia everybjdy complains of a lack of water, the Trans-Baikal country is visited by frequent rains. This abundance of precipitation is due to the monsoon which, in some years, extends into a portion of the Province (Gubernia) of Irkutsk. All the rivers then begin to rise, not excepting even the Selenga, if we may judge from the scanty information obtainable for this river. Even the level of Lake Baikal, in spite of the enormous extent of its surface will, in some years, rise appreciably. Of the changes of level of other Siberian rivers, and of the times of greatest height of the water, we can judge only from the available data as to overflows and inundations caused by such overflows. Thus, beginning in west Siberia, in the basin of the Obi, the overflows of the rivers are usually observed in the spring. What contributes most to the intensity of the overflow is the early opening of the rivers, the great amount of the snowfall in winter, in particular if the snow falls on a previously frozen soil, the rapid approach of warm weather, or, RIVERS OF SIBERIA. 109 what is called, a "kind spring," which causes the simultaneous open- ing of many rivers. In the east, on the other hand, owing to the long and uninterrupted prevalence of the anticyclone in winter time, the winters are marked by an exceedingly small amount of snowfall, while in summer, during the reign of the summer monsoon which carries moisture from the Pacific Ocean, there is abundant rainfall, causing heavy overflows of the rivers, especially in the Amoor country. It is, however, not yet decided how far the rains caused by winds from the Pacific extend into the interior of eastern Siberia. But the heavy inundations occurring sometimes in the Province of Irkutsk in summer would seem to indicate that the influence of the monsoon occasionally reaches this territory. To characterize the distribution of the precipitation over Siberia, I give the following results derived by Dr. Woeikof for the mean precipitation as percentage of the total annual amount : Place. >> >i c s .a 0! S a OS a X> .a 03 u p. < c a "-5 a < fa 0. n 32 2 s > 5 3, ?■ 6 7 13 17 g 12 II 3 2 3 4 II 14 17 18 9 « 4 4 3 5 6 14 17 13 12 8 I O.q o.q 0-5 5 23 29 25 9 2 1.8 0-5 0.4 l-.S 3 6 16 26 28 12 3 1.8 3 3 4 6 8 10 10 18 21 8 Semipalatinsk Barnaul Irkutsk Kiakhta Nerchinsk Nicolaifsk on the Amoor It appears from these data that the amount of precipitation is dis- tributed over the year more uniformly in western Siberia than in eastern Siberia. The lack of uniformity is particularly striking in the Trans-Baikal country. For the Province of Irkutsk we have observations for a considera- ble period at the city of Irkutsk ; these give for the annual distribu- tion of the precipitation (in millimeters) the following figures: Jan- uary, 19.2; February, 13.2; March, 10.0; April, 14.1; May, 26.5; June, 62.1; July, 72.1; August, 63.6; September, 41.6; October, 19.3; November, 15.8 ; December, 22.5. But from year to year the monthly amount of moisture varies very much. Thus, in June the greatest mean precipitation was 161.6 mm. (in 1877); in July, 131.5 mm. (in 1878); in August, 107.8 mm. (in 1884), while in winter the maximum precipitation reached only 48.3 mm. in January, 1882. But there are years in which the precipita- tion for January and February is equal to zero. The mean amount of precipitation at Irkutsk is as follows : Winter, 54.9 mm.; spring, 50.6 mm.; summer, 197.8 mm.; autumn, 88.1 mm.; in the driest summer there was 78.4 mm. (1888), and in the wettest 304.6 mm. (1883). Besides, the amount*of precipitation in any given year is distributed very differently over the territory of no CHICAGO METEOROLOGICAL CONGRESS. the Province of Irkutsk, as will appear from the following table for 1887 : Place. ter. Spring. Summer. 26.1 32-2 42.2 68.2 89.2 119-7 41.0 18.6 42.6 30-7 81.8 282.0 25.0 15-1 62.8 52-4 163.7 252.1 6-3 25-7 225.9 Autumn. North— Bashchikovo ., Usti-Kuta West— Birinsa Cheremkhovo . East- Irkutsk Shimki , Southeast — Tunka (1889) .. 141-4 109.3 96.6 76.0 54.7 40.7 66.3 In the Amoor territory the want of uniformity in the distribution of the precipitation in the course of the year is still greater. Thus in 1878 the amount in millimeters was as follows : Place. Nerchinsk Mining Works Blagovechensk Khabarovka Nikolaifsk Vladivostok Uga Harbor ( 18&0) Winter. Spring. Summer. 4-7 24.0 233-4 0.0 83.1 204.6 3-9 71.9 220.0 67-5 77-3 177.1 7-6 46.1 100.7 29-3 198.5 270.4 Autumn. 103.4 48.2 74.2 155- 1 90-3 348.8 To illustrate the non-uniformity of the distribution of precipitation during the summer months in different years, I give the following two years : Place. Nerchinsk Blagovechensk Khabarovka... 1878. June. 49-3 36.6 31.9 August. 98.7 71-7 49-4 1880. June. 149. 1 56.0 II4-5 August. 159.8 119.5 184.0 The abundance of moisture in the Amoor territory, accompanied at the same time by cloudy weather, low temperature, and reduced evapo- ration, is the cause of heavy inundations in summer. Although the ratio of the amount of precipitation in the wettest to that in the dri- est summer month is considerably less at Irkutsk than in the Trans- Baikal, yet it is much greater than at Yeniseisk and other localities situated farther west and agreeing more closely in this respect with Russia. I now proceed to give a brief account of the data concerning inun- dations available for Siberia. I begin in the west. An unusually large inundation took place in the spring of the year of 1857 along the western affluents of the Obi. It began on the river Vagal and its tributaries. In' the same spring an unusual increase of water was also noticed in the rivers Irtish, Tobol, Toora, Omi, and others. Thus, RIVERS OF SIBERIA. Ill on May 20, the river Irtish overflowed its banks near Tobolsk ; on June 1 the water had there risen to a height of 6 meters above its mean level, flooding four hundred houses. The waters began falling on June 10. The highest rise of the water in the Irtish, near the city of Omsk, was only 2 meters above the mean level. In the river Toora the water often rises to a considerable height at the time of the spring floods, which wull continue from thirty to seventy-five days. At the greatest of these floods, in 1854, 1857, and 1870, the waters of the Toora rose from 6.5 to 9 meters above its ordinary level near the cities of Toorinsk and Tioomen. The greatest inundation of the river Tom, near Tomsk, is said to have taken place in the year 1804, when the ice in the river began to move on May 11, and on the 12th the overflow had reached such dimensions as to inundate five districts in the lower portion of the town. On May 13 and 14 the water rose still 0.75 meters higher, carrying ice. Altogether, the water rose 5 meters above the ordinary level. Beginning with May 15, the water fell rapidly. Next to this the heaviest inundation of the Tom occurred in 1843, from April 20 to 26, and in 1887, from April 25 to 27. When the ice opens on the Yenisei River the city of Krasnoyarsk generally suffers less from the floods than the city of Yeniseisk, which is situated farther down on the river. At Yeniseisk the overflows are particularly heavy when the ice opens at the same time in the Yenisei and in the Upper Toongooska (Angara) and Tasieieva. Usually, how- over, the ice opens six days later on the former and twelve days later on the latter than on the Yenisei. In the course of the last sixty years there were in all eleven inundations, of which those in the years 1800 and 1857 were the most destructive. The Yenisei overflows twice a year. One overflow usually occurs in spring, in the latter part of May, and is called the " snow water." In some years the water, at the time of the spring overflow, will reach a height of 14 meters above the mean level. The other overflow, which is less important and is called "root water," occurs generally toward the end of June; it is due to the snow melting in the mountains. In 1870 a heavy summer inundation occurred in the Nizhnee-Oodinsk district of the Provinc.e of Irkutsk, in the basin of the rivers Ooda and Ya, which are affluents of the Angara. The former overflowed its banks on July 5 and inundated almost the whole valley through which it flows, the water rising particularly in narrow places hemmed in by rocks. The city of Nizhnee-Oodinsk was the principal sufferer ; in the various villages situated along the valley of the Ooda, ninety- nine houses, two mills, and a sentinel's box were destroyed and carried away ; two men and a great number of cattle were killed. In the river Ya and in its right-hand tributary, Aza, the water began rising on July 4, and on the 9th the waters rushed over the banks with such 112 CHICAGO METEOROLOGICAL CONGRESS. rapidity and such incredible power that an "oboz" (row of wagons for transportation) laden with tea, standing near the bank, did not have time to escape and was carried away by the flood. On July 8 a heavy overflow began also in the valley of the Biriusa, an affluent of the Ooda. The Angara, as mentioned above, has its overflow near Irkutsk in winter. This winter high water is an annual phenomenon, though varying in intensity more or less from year to j^ear. There are no exact data as to how far down the river this winter overflow extends. It is known, however, that at the village Bratsky-Ostrog, situated on the Angara, 310 kilometers below Irkutsk, the river overflows at the time of the breaking up of its ice in the spring, and inundates the settlements situated on its banks. The difference between the summer and winter water level of Lake Baikal does not generally exceed 1 meter, though sometimes it amounts to as much as 3 meters. During the very rainy sum- mer of the year 1869 the waters of Lake Baikal rose 4.5 meters above the usual level. Considering the great dimensions of this lake (about 34,180 square kilometers), this enormous increase of water gives an indication of the immense quantities of water which the Baikal must receive from the rivers emptying into it. According to the Ir- kutsk records, there were in that summer twenty-four cloudy days in July and twenty-one in August. Now, on an average, there cor- responds to every rainy day the following amount of precipitation : In June, 2.83 millimeters (maximum, 17.4); in July, 5.87 (maxi- mum, 27.6) ; in August, 6.49 (maximum, 64.6) ; and in September, 0.84 (maximum, 7.4). It follows that the rise of the water level of the Baikal was directly dependent upon the great amount of precipi- tation received in the surrounding country at the time of the sum- mer monsoon ; this precipitation being carried into the Baikal by the numerous rivers emptying into it, of which there are as many as three hundred and thirty-six. Among these affluents there are three of considerable size, viz., the Selenga, the Upper Angara, and the Bar- goozeen. The only outflow for the waters of the Baikal is furnished by the Angara. The area from which the affluents of Lake Baikal collect their waters has been computed as 320,500 square kilometers. The river Lena, in its upper course, does not overflow when the ice breaks ; a small increase of its water level occurs in the second half of May, when the snow melts in the mountains. The time of great- est increase of water is usually in the middle of July ; it is due to the heavy rains occurring at this time. Destructive inundations are, however, rarely caused by this high water ; those best known are the inundations of 1816 and 1864. In the latter year the water of the Lena, near the city of Verkholensk began to rise rapidly on July 11: on the 13th it overflowed the banks and inundated the mea- RIVERS OF SIBERIA. 113 dows, islands, and the lower end of the city ; on the 17th the river was again confined to its banks. The whole month of July of the year 1864 was rather cold for summer weather ; the same is true of the month of August, which had a mean temperature of only 8.4° ; on September 3, at 5 a. m., the thermometer stood at — 3.8°. There were twenty-two rainy days in July ; in August it rained twelve times and snowed twice, the water in the Lena increasing again rapidly from August 8 to 14. In the middle course of the Lena, in the Kirensk district, we find, besides the summer high water, overflows at the time of the opening of the ice. Thus in 1870 the ice on the Lena near the city of Kir- ensk began moving on April 30 ; the river overflowed its banks and inundated part of the city ; and when, on May 1, the ice began also to move on the right-hand affluent, Kirenga, which empties into the Lena near the city, the water rose still higher, doing a great deal of damage in the city. The overflow was especially great in the villages of the Vitimsk district, situated along the Lena, below the city of Kirensk. The farther we go eastward into Siberia the less frequent and destructive are the spring inundations, owing to the small amount of snow that falls during the winter months in the Trans-Baikal and the Amoor territory. In the latter country deep snow is found only in the lower course of the Amoor. But, at the time of the summer monsoon, the abundant precipitation causes heavy summer inunda- tions. During the years 1855 to 1882 eight great inundations were observed in the basin of the Amoor ; the most destructive of these was the one in 1872, which came from the upper course of the Amoor. At Stretensk the water level reached its greatest height on July 9, at Blagovechensk on the 15th and 16th. At the latter place the water rose 10 meters above the ordinary level, in spite of the fact that the river valley is there rather open and the banks of the Amoor, in par- ticular the left-hand bank below the city, are lowlands. But, in the Maly-Khingan mountains the water in the Amoor rose 16 meters above its mean level. On July 19 the water began to fall near Blagovechensk. Out of twenty-seven settlements (stanitsa), situated on the left bank of the upper Amoor, ten were carried away by the flood. A second, and very considerable, rise of the waters of the Amoor occurred in the month of August of the same year, coming from the rivers Argoon and Zeia. Thus on August 9 and 10 the water of the Amoor rose 17.5 meter8( !) above the ordinary level at the Pokrovsky settlement ; at the city of Blagovechensk the greatest height of the water occurred on August 15 and 16, but the height reached was less than in July. Heavy floods were also observed in the river Zeia in 1861, when the water of this river rose three times in the course of the same sum- 114 CHICAGO METEOROLOGICAL CONGRESS. mer — from June 10 to 13, from July 20 to August 2, and from August 31 to September 10. In the southern portion of Ussurysk territory the heaviest inunda- tions occurred in the years 1861, 1863, 1868, and 1873. The overflows of the Amoor begin usually after more or less prolonged rains. But as the amount of precipitation is not uniformly distributed, the in- undations are most heavy sometimes in one, sometimes in another part of the Amoor and Ussurysk territory. As regards the current velocity and the discharge of th« Siberian rivers, we have, besides the scientific determination of these quanti- ties made by Dr. Stelling for the Angara, some observations on smaller rivers, viz., the Tobol and the Toora. These observations were made with a view to decide the question as to the sufficiency of the supply of water in these rivers for navigation purposes. Observatfons were also made on some other small rivers, viz., the Oziornaia, Lomovataia, Jazevaia, Maly Kas, and Bolshoi Kas, in connection with the investi- gations for the purpose of connecting the Obi with the Yenisei. The observations of Dr. Stelling at Irkutsk showed that the mean water level of the Angara at this point has an elevation of 453.3 meters. He also found the results tabulated as follows : c ^ '^ i: e! O c 2 = «.= O- u 43 Velocity O. . of current, in B ■a I- S" meters per second. *3 « «J ^ (T* J5 CD P o E 3 £ sD **) ^ *-» vO O 0»CO '-^^^ OsN^ O^t^a^^ -^vO ONIN a> VO « 00 t^ l~. ■* Tf •'l^^ "5 OS 3 fe i-^ it; M * 0)*" 0.3 0) — 5® s -»3 ta cC n cS ^ o ©■o 2 OS s C iv b o ^*<2* b J 3 r^vO O »Ot^rOvO o-^^^ 1 HH fo^ « fOoo — n N N N s N ^o N o ro « r^ r^^ rH 1 a 1 1 1 1 1 1 1 1 1 1 ■ ' s a 1 1 1 1 1 1 1 T^ 1 T © N-a « « 3 i •3 ® „« t- z Jl. A tie -■^Si 03 t .5 o^ O 3 « t- J. '5 ■^N OOOVO >-• <->00 0\0 He..£^3 N'-^-^OW-^or^Ot^f* a m •* ro ■* « -^-^O IM « « a 1 1 1 1 1 -1 1 1 1 1 ■4 ■ i s- ©■a ^ 1 1 1 1 1 MM ^ a Ul oS o-« — ' >-s 3 2 a |S 3 ' \o • • ' • * r^ • • a o 3 3 -.J o.-" -^' *5 -» -J o.-t>" *5 « •O 1 OdiUOOOOmOOO m "^ a ■< 0»0OOOCwOO0 2" (0 CD 0? rt >>i6>(jj£^>>> ■!! 3 ©■« OS S" h:; 00©0-io--^*-tr^ .5 azQZQs^ozzz .s "5 6 ^ ^ >■ ^l Mean umbe f day ree o ice. h OOOOZQOOZO c o'*22 c« >,% >>>>>■>>>»>.>>>. t ,5 til a ^a esScSKcScSoScioicJ ^C>^- j.-^^- > f" > a o. u Oc? Oo^OOOOO w i-N««Cl_«u-)"i-c c a a "u U>^UtZu^fc^>*C>> <8*OOvi;^MO jjOO Jj 1 — c ® O tS C- WX2 ® — 1 e! oc 1 © J5 TJt« u 5°-? 9 c h o o ® £ t^\0 »- r» N -(J-OO OnvO t>. C O 00\OO\ONO\OOP<"M'<; 1 J C5 a) o.- 2i;S o :i i o ' 1 « "S 73 a « <» O O a c CO o 1 ._ « c a) t. m ^.a > « E cS z c 3 T o 2 E ._ a £.''a a «o^H--< *>< oZ iH M ro ^ 11 PI ro ■<»■ •w *^ ' THE RHINE. 117 6— REGIMEN OF THE RHINE REGION: HIGH- WATER PHE- NOMENA AND THEIR PREDICTION. M. VON Tein. The regimen of a river, as well as the appearance and progress of high-water phenomena, it is known, bear a close relation to the physi- cal characteristics of the region, particularly the relief of the ground, the extent of the drainage area and the climatic elements dependent on the former, especially the distribution of the rainfall. A con- sideration of the hydrological phenomena of a region requires, there- fore, at first a glance at its general physical characteristics. The Rhine, although it drains scarcely an area of 160,000 square kilometers with its tributaries, extends diagonally through the prin- cipal jjarts of middle Europe, the Alps, the mountain region of central Germany, and the Netherland lowlands. Its drainage area has there- fore an uncommonly great variety of relief. From the chain of the central Alps, towering to a height of 4,000 meters, forming the south- ern boundary, the region falls toward the Swiss and upper Swabian highland, of which the average elevation is 500 meters, and rises again to over 1,000 meters in the Jura, the Black Forest, and the Vosges, the most considerable elevations of which bound it on the west and north. Sunk between the Black Forest and the Vosges lies the upper Rhine lowlands traversed by the Rhine, while on the verge of the mountain range roundabout spreads extensive terrace and the fiat valleys, forming the region of the entrance of the great central moun- tain rivers — the Neckar, Main, and Moselle. On the north the mountains of the lower Rhine, traversed by the Rhine in a deeply eroded valley, shut off the central mountains toward the north German highland to which the lowest parts of the drainage area belong. The Rhine flows here in its upper course through high mountains, a high tableland, and the central mountain range ; in its middle course through a low plain and then, for the first time, after breaking through the great chain of the central mountain range, begins its lower course with its entrance into the north German lowlands. The grouping of these surfaces forms a many-branching river system among the streams of the Alps, of the central mountain region, and the lowlands, a distinction which, for the regimen of the drainage area, is of the greatest significance. The Rhine assembles the streams of the Alpine country and the borders where it leaves the Swiss highland ; here the Alpine part of the tributary region ends, which, with considerable rainfall, has also great capacity for retaining water. The precipitation in the Alps for the greater part of the year being 118 CHICAGO METEOROLOGICAL CONGRESS. in a solid form, is stored up in the winter and in the warm season is given up as melted snow more or less freely, and the run-off is modi- fied by a considerable number of lakes around the border of the Alps. The region of the central mountain rivers begins with the breaking of the Rhine through the Jura or with its entrance into the uppe Rhine lowlands at Basel. At first the river receives only small streams, for, on both sides parallel to it and only a short distance from it, the Black Forest range and the Vosges turn their steep flanks toward it, while on the other side they drain off toward the Neckar and the Moselle. The Rhine in this, the second principal part of its course, traverses a distance of more than 300 kilometers before the great central mountain river, the Neckar, empties into it, and then, in relatively rapid succession in a distance of about 150 kilometers by the river, there come into it the Main, the Nahe, the Lahn, and the Moselle. In the region of these central mountain range rivers, the Black Forest range, and the Vosges, the rainfall is still very con- siderable. The snow covering in the course of the winter, from repeated thaws and according to its height and density and the accompanying circumstances of its melting, occasionally produces great floods in the streams in a short time. Persistent rain and thunderstorms often carry the wet period into midsummer, and in autumn in the high central mountain region the precipitation reaches its maximum ; the feeding out of water to streams diminishes very considerably in consequence of the great loss of water by evaporation and absorption by plants. The third division of the Rhine drainage area, comprising the streams of the lowland from about the mouth of the river up to the lower Rhine Mountains, is relatively small and not of much importance as regards the water which flows from it into the Rhine. The region is under the moderating influence of the ocean climate, so that sudden changes of weather and their conse- quences are scarcely perceptible in the rivers. The changes in river stage along the Rhine occur as follows : along the upper course and down to the Neckar the flow from the Black Forest range and the Vosges is, as a rule, not considerable enough to make any appreciable change ; it is completely controlled by the water from the high mountain region ; very little water comes in during the winter ; there is considerable addition of water in the spring with the disappearance of the snow on the lower mountains ; there is an increased flow at the beginning of summer as the melting advances up the high mountains ; and finally, again a diminishing supply of water, until toward spring, in spite of the continuing addi- tions of glacier water. There is, therefore, a tolerably steady increase from winter, not, however, without this regular course being varied and broken into at times by heavy floods due to great rainfall such as often accompanies the Fohn wind. In the section of the Rhine THE RHINE. 119 between the Neckar and the Moselle, under the influence of the great central mountain range rivers, a change occurs in the order of river- stage variation which begins to be first apparent at the entrance of the Neckar, and still more so at Mainz after the entrance of the Main. Below the mouth of the Moselle there is a complete reversal of con- ditions. The diminished supply of water toward the end of winter becomes apparent at Mainz as a secondary maximum ; below the mouth of the Moselle it reaches the summit of the annual curve ; at this point, on the contrary, the summer high water of the upper Rhine, which is seldom strongly reinforced from the central moun- tain range region, sinks to a moderate rise, while on the other hand in February and March, among the poorest months in the year in water above the entrance of the Neckar at the mouth of the Moselle, the highest stages occur. In the lower Rhine the stages of water thus produced by the Neckar, Main, and Moselle no longer change, but are rather intensified by the tributaries. A like great difference in the behavior of the various parts of the Rhine appears, especially during the prevalence of high water. It is in a measure a rule, that considerable flood waves in the upper part of the drainage area appear along the middle and lower courses as inconsiderable rises, and that again, flood phenomena appear in which the upper courses of the river have no part. The absolute high waters observed so far in the various divisions of the river have oc- curred in entirely different periods of high water. Excessive arid disastrous high waters affecting the river in all its parts scarcely ever occur ; at least they are exceedingly rare. The high water is always caused by extraordinarily great rainfalls, which, as experience shows, occur over only very restricted areas and in isolated cases, when, with great downpour, melting of snow occurs simultaneously over a great part of the drainage area ; under these circumstances the tributary basins cause various combinations of high-water waves. It frequently happens that the highest stage of a rise in the middle Rhine occurs when at the same time the upper Rhine is still rising and the apex of the rise comes down as far as the entrance of the Neckar, and by that time the high water in the middle and lower Rhine is long past. The behavior of the tributaries has a very important bearing on the course of high water in the main stream, especially if the flood waves from the last two great tributaries, the Main and Moselle, both of which in length of course, extent, and nature of drainage area show great similarity, succeed each other in such a way that the wave from the Main comes in on the crest of the wave from the Moselle at Coblentz. The subsequent flood wave from the upper Rhine causes in the middle and lower Rhine, and in fact from the Neckar down, only a delay in the recession of the water. It is a fact well known from experience, and it finds explanation in 120 CHICAGO METEOROLOGICAL CONGRESS. the preceding remarks, that the Rhine region, as compared with the neighboring regions, is naturally protected in a higher degree against the frequent occurrence of disastrous high waters, because many oppo- site conditions must act together to produce such a high water .^ Never- theless, the occurrence of such an event in such a closely cultivated region as this is, means, in every case, a great damage to agricultural interests. Ten years ago, after the memorable high water in the winter of 1882-83, the German Imperial Government established a commission to investigate the Rhine and consider the best methods of artificial protection against floods. This commission reported in 1891 to the Chancellor of the Empire the results of its eight years' activity. In the report the fact is emphasized that, in view of the dense population and minutely cultivated parts, it is out of the ques- tion to try combating the might of high waters by measures calculated to restrain the waters on a large scale, aside from the fact of the enor- mous expense of such a proceeding — out of all proportion to the ad- vantages to be derived — and other vested interests of the population of the region would be thereby greatly damaged. High water protec- tion, in addition to measures of protection by a suitable treatment of the course of the river, and by the leveeing of frontages threatened by floods, must remain limited to deriving a correct knowledge as to what must be withstood from the beginning and throughout the course of dangerous rises. This knowledge consists, up to the present time, in a carefully organized service for the dissemination of infor- mation regarding high water, by telegraph principally. What still remains in this domain worth gaining, and which the commission in investigating the Rhine proposes to attain, is the numerical determi- nation of water heights to be reached during rises along the middle and lower courses of the Rhine, and along the upper course and its larger tributaries, and also the establishment of a system of high water predictions. This, for the population interested, would doubtless be more valuable than simply information as to the stages of water at places on the river above. Considering the extraordinary difficulties in the way of forecasting, in view of the changing regimen of the river just described and the complex phenomenon of a high water, and the lack of previous hydrological investigation (which heightens the diffi- culty), high water predictions have not yet been attempted. In the year 1886, on the suggestion of the Imperial Commission before men- tioned, the Central Bureau fur Meteorologie und Hydrologie of Baden, ^ The regimen of the Rhine region and the behavior of the river during high water is treated of very full}' in the work J)er Eheinstrom und seine wichtigsten Nebenfliisse, Berlin, 1889, issued from the Central Bureau fur Meteorologie und Hydrographie in the Grand Duchy of Baden. The high waters occurring in this century are treated of very fully in the first volume of Ergehnisse der Untersuchung der Hochwasserver- haltnisse im Deutscheti Rheingebiet, Berlin, 1891. THE NILE. 121 at Carlsruhe, was designated as the proper institution to be entrusted with the investigation of hydrological phenomena during the incep- tion and progress of great rises in the Rhine and its tributaries, so as to lay a firm, scientific foundation, on which, perhaps, satisfactory high-water predictions may in the future be based. 7— THE NILE. W. WiLLCOCKS, M. I. C. E. The recent explorations of Lugard and Baumann have completed the work originated by Burton and carried on by Speke, Grant, Baker, Stanley, Gordon, Junker, and Schweinfurth, and we can now follow the course of the Nile from its springs far south of the equator to its termination north of the thirtieth parallel of latitude. A river so regular and gentle in its movements as the Egyptian Nile can only be understood after a study of its sources of supply, and the early part of this paper must, therefore, be devoted to the hydrology of the Nile Valley. On the accompanying plan and longitudinal section are detailed the observed times and heights of high and low supply, and the times and proportions of rainfall. From the sea to Wady Haifa the Egyptian Irrigation Service has supplied the figures ; from Wady Haifa to Khartoum Sir John Fowler's surveys and levels have been used, with a correction of 13 meters to suit the figures of the irrigation department at Wady Haifa; while to the south of Khartoum the distances and heights have been taken from the obser- vations of Gordon Pasha's staff when he was governor of the Soudan. To Lake Victoria a mean level has been applied. I take this oppor- tunity of acknowledging my thanks to Bonola Bey, the Secretary of the Khedivial Geographical Society of Cairo, for the assistance I have received from him. I am at the present moment engaged in making a stud}" of the Nile for the Egyptian Government. This study will not be completed before the end of December, but on the invitation of your committee, with the consent of Mr., Garstin, Under Secretary of State for Public Works in Egypt, I have collected all the information which is at my disposal to-day and have embodied it in this paper. The Nile drains nearly the whole of northeastern Africa, an -area comprising 3,110,000 square kilometers. Its main tributary, the White Nile, has its source to the south of Lake Victoria and has trav- ersed over 3,500 kilometers before it is joined by the Blue Nile at Khartoum. From the junction onward the river is known as the Nile, and after a farther course of 3,000 kilometers flows into the Mediterranean Sea by the Rosetta and Damietta mouths. Lake Victoria, covering an area of 70,000 square kilometers is the 122 CHICAGO METEOROLOGICAL CONGRESS. first reservoir of the Nile. The equator passes through this lake, which lies in the region of almost perpetual rains and receives an excessive supply of water from its western tributaries, from subsoil springs, and heavy rainfall. Stanley considered the discharge of the White Nile as it left Lake Victoria as one-third greater than that of the Tangourie, the principal affluent of the lake. Judging from re- corded observations farther down the river, the mean discharge of the lake is probably 750 cubic meters per second. Shortly after leaving Lake Victoria, the White Nile descends the Ripon Falls on a width of 400 meters and a drop of 4 meters. Lake Victoria lies about 1,130 meters above sea level and is 500 meters higher than Lake Albert. Between these lakes, on a distance of 480 kilometers the White Nile (known here as the Somerset) traverses at first the succession of swamps known as the Ibrahimia Lake, and then taking the character of a mountain torrent precipitates itself into the southeast corner of Lake Albert. The survey of Lake Albert, which has an area of 4,500 square kilometers, was made in 1877 by Mason Bey, and he recorded the fact that the lake was 1.20 meters below its high-water level. The rainfall of that year was deficient in the whole of the Nile Val- ley, and the summer supply of the Nile was the lowest of which there is any record. In July, 1892, Capt. Lugard noticed that Lake Vic- toria was 2 meters above its normal level after the heavy rains of that year, and the summer supply of the Nile in 1893 is so high that it has only once been exceeded, according to our records. Lake Edward, with an area of 5,000 square kilometers and a height above sea level of 880 meters, is a feeder of Lake Albert. After leaving Lake Albert the White Nile flows for 200 kilometers in a deep, broad arm with scarcely any slope and scarcely any velocity as far as Duffle, and then after a short, troubled course tosses over the Fola rapids on a width of 90 meters, and continues as a torrent for another 200 kilometers to a short distance south of Gondokoro. At Gondokoro the river is 2 meters deep at low water, and only 4.50 meters deep in flood, the dis- charge ranging between 500 and 1,600 cubic meters per second. The regulating effect of the great lakes is well felt here. We are indebted to Emin Pasha for this information. It is one of the keys for under- standing the flow of the Nile, and will be dwelt on later in this paper. At Gondokoro the river is at the lowest in winter, it begins to rise about April 15, and reaches its maximum between August 15 and 30. From Gondokoro to Bor, a distance of about 120 kilometers, the river keeps in one channel and has a rapid fall, while from Bor to the mouth of the Gazelle River, on a farther reach of 380 kilometers, the river divides into numerous channels and has a very feeble slope. The main channel is known as the Bahr el Gebel (the mountain stream), and is the one always used for navigation. In this reach are the " sadds " or dams of living vegetation which, at times, are THE JflLE. 123 capable of barring the surface and completely blocking navigation. The Gazelle River joins the White Nile on its left bank and has a feeble discharge in summer, but exceeds the Bahr el Gebel in flood. At the junction of the Gazelle River and the White Nile is a lake of an area of some 150 square kilometers in summer. During this latter period, in years of scanty rainfall, all this part of the river acts as an evaporating basin and a source of loss to the Nile. The waters of the river likewise become polluted here with decaying vege- table matter which, at certain times of the year, imparts a green color to the Nile as far north as Cairo. One hundred kilometers below the Gazelle River the White Nile is joined by the Saubat River on its right bank. During flood this river has a discharge nearly equal to that of the White Nile above the junction, while in summer it has a feeble discharge and is occasionally quite dry. From the junction of the Saubat to Khartoum, on a length of 900 kilometers, the White Nile has a mean width of 1,700 meters, a depth varying from 5 meters in low supply to 7.5 meters in flood, and a sluggish stream. The action of the current is always on the right bank owing to the pre- vailing northwest Avinds, and this action is continued during the whole of the remaining course of the river as far as the sea. The soil from the Saubat River to Khartoum is light and friable, and the White Nile, in spite of its moderate velocity, has a width 160 limes its depth in flood. At a point 3,009 kilometers from the sea, and 390 meters above it, is the town of Khartoum, where the Blue Nile from Abyssinia joins the White Nile. The Blue Nile has its sources in the mountains of Abyssinia, where Lake Tsana — with an area of 3,000 square kilometers and height above sea level of 1,780 meters — is another reservoir of the Nile. The Blue Nile has a length of 1,350 kilometers. This river is comparatively clear in summer, but during flood, i. g., from the begin- ning of June to the end of October, it is of a reddish-brown color, highly charged with alluvium. The Khartoum Nile gauge, which was read from 1869 to 1883, used to stand on the Blue Nile about 5 kilo- meters above its junction with the White Nile, and its recorded read- ing are not exact records of the Nile. In flood the discharges of the two rivers are equal, but in summer the White Nile is the main source of supply. The Nile here has a mean range of 6.50 meters between high and low supply, with a maximum of 7.80 meters and a minimum of 5.30 meters. From comparisons with the Assuan gauge, and' ob- served discharges referred to the Khartoum gauge, I calculate that the high supply varies between 12,900 and 5,200 cubic meters per second, with a mean discharge of 8,000 cubic meters per second, while the low supply varies between 1,500 and 320 cubic meters per second, with a mean discharge of 550 cubic meters per second. April is the lowest month and September the highest. 124 CHICAGO METEOROLOGICAL CONGRESS. At a distance of 90 kilometers down stream of Khartoum is the sixth cataract. Here the Nile descends 6 meters on a length of 18,000 meters. At a distance of 320 kilometers from Khartoum the Nile is joined by the Atbara River. This latter is another stream fed by the Abyssinian torrents, and though dry in summer is a considerable river in flood. Heavily charged with volcanic detritus it provides the greater part of the rich, fertilizing mud which the Nile carries in flood. The Atbara has a range of 8 meters, and from calculations and comparisons I estimate that its floods range between 4,900 and 1,600 cubic meters per second, with a mean high flood of 3,400 cubic meters per second. It is in flood from July to October, with its ordi- nary maximum in August. Below the Atbara junction the Nile has no tributary, and flows throughout its 2,700 kilometers to the sea a solitary stream. Traversing one of the greatest deserts on the globe, it is the sole source of life and vigor to whatever exists on its banks. Twenty-four kilometers downstream of the Atbara junction is Ber- ber, and 45 kilometers downstream of Berber is the beginning of the fifth cataract, which has a length of 160 kilometers and drop of 66 meters, with three principal rapids, the Solimania, Baggara, and Mograt. The village of Abu Hamed is situated at the foot of this cataract. Between Abu Hamed and Dongola is the fourth cataract, which begins at a point 100 kilometers downstream of Abu Hamed, and has a length of 110 kilometers, with a drop of 49 meters. In this series of rapids are the Um Der^s and Guerendid. Between the fourth and third cataracts is a reach of 310 kilometers on a slope of 1 : 12,000. On this reach is the town of Dongola. The third cata- ract has a length of 70 kilometers and drop of 11 meters with the Hannek and Kaibar rapids, surveyed and leveled by De Gottberg in 1857. Upstream of the Hannek rapid on the left bank of the Nile is the termination of the long depression in the deserts, which goes by the name of Wady el Kab, and is considered by many as lower than the Nile valley. Between the third and second cataracts is an ordinary reach of 130 kilometers. West of this part of the Nile are the Selima Wells, and, according to some travellers, an old abandoned course of the Nile slightly above the present high level of the river. This waterless river terminates in the Oasis of Berys, which is separ- ated from the Khargeh Oasis by a limestone ridge. The second cataract, known as the "Batn el Haggar," has a length of 200 kilometers and drop of 66 meters with the rapids of Amara, Dfil, Semna, and Abka. At Semna are the rocks where Lepsius dis- covered the Nile gauges cut by one of the Pharoahs some 4,000 years ago. The Nile flood then was 8 meters higher at this spot than what it is to-day. The erosion which has taken place here is very excessive compared with that between the second and first cataracts and at the first cataract. At Wady Haifa, near the foot of the second cataract, THE NILE. 125 a masonry gauge, divided into meters, has been erected and read since 1877. Between the first and second cataracts the Nile has a length of 350 kilometers and slope of 1 : 12,500. The mean width of the river is 500 meters, and the mean depths in flood and summer are 9 and 2 meters. The velocity in summer falls to 50 centimeters per second and rises to 2 meters per second in flood. The river in this reach is generally within sandstone, and the greater part is provided with gigantic spurs on both banks. These spurs perform the double work of collecting soil on the sides in flood and training the river in summer. They were probably put up by the great Rameses 3,000 years ago, as some of the most massive of them have evidently been constructed to turn the river on a curve out of its natural channel on to the opposite side in order to secure deep water in front of the temple of Jerf Husain ("Jerf" means steep, scoured bank). The spurs have been constructed with care, and, as the courses of roughly dressed stone can be examined at fairly low water (I have never seen them at absolutely low water), it is evident that there has been no great degradation of the })ed during the last 2,000 or 3,000 years. The first, or AssuAn, cataract has a drop of 5 meters on a length of 5 kilometers. From Khartoum to Assuan, on a total length of 1,809 kilometers, there are 563 kilometers of so-called cataracts with a total drop of 203 meters, and 1,246 kilometers of ordinary channel with a total drop of 83 meters At the foot of the first cataract, opposite the town of Assuan, on the island of Elephantine, has stood a Nile gauge from very ancient times. An officer belonging to the Roman garrison in the time of the Emperor Severus, marked an extraordinary high flood on the gauge. The maximum flood mark at the time of the visit of Napo- leon's French savants was, however, 2.11 meters higher than the above As the middle of Severus reign was A. D. 200, and the visit of the French savants A. D. 1800, they concluded that the bed and banks of the Nile had risen 2.11 meters in 1,600 years, or 0.132 meters per 100 years. The new gauge, divided into cubits and twenty-fourths, was erected in 1869 and has been recorded daily since then (a cubit = 54 centimeters). From Assuan to the Barrage the length of the river is 970 kilome- ters, and the slope 1 : 12,900, while the mean fall of the valley is 1 : 10,800 ; from the Barrages, at the head of the Delta proper, the dis- tance to the sea down either branch is 236 kilometers, with the same slope as before. The mean width of the main Nile is 820 meters, and the mean depth in flood 8.5 meters. On the Rosetta branch the mean width is 500 meters and depth 8 meters, while the Damietta branch has a mean width of 350 meters and mean depth of 7.5 meters. The mean velocity in flood is between 1.50 and 1.1 meters per second. As 126 CHICAGO METEOROLOGICAL CONGRESS. the Nile in these reaches is in soil, it is evident that a mean flood velocity of 1.50 meters per second scours out a channel whose width is ninety times its depth, while a velocity of over one mieter per second has a width some fifty times its depth. The natural canals, which take off the river and never silt, have a mean velocity of some 70 centimeters per second while the proportion of width to depth is about 12 to 1. Artificial canals of this section do not silt if their velocities are 70 centimeters per second, while silting takes place as readily when the velocity is greater as when it is less than the above. In muddy streams, like the Nile in flood, certain velocities demand certain proportions of width to depth, and if these are not given to it they will make it for themselves by eating away the sides if they can, or by silting up and raising the bed if they can not eat away the sides. On Rhoda Island opposite Cairo has stood a gauge from very ancient times. It has been frequently reconstructed. The present gauge was erected in A. D. 861. It is in cubits and half cubits on some very arbitrary scale. When the gauge was constructed a read- ing of 16 cubits on the gauge meant the lowest level at which flood irrigation could be insured everywhere. In 1887 the Egyptian Gov- ernment called upon all the Inspectors of Irrigation to report on the minimum gauge for perfect flood irrigation, and they reported 20.5 cubits on the gauge. The difference between 16 and 20.5 cubits on the Rhoda Island gauge is 1.22 meters, and as 1,026 years had elapsed since the construction of the gauge, it meant a rise of 0.119 meters per one hundred years. This is slightly undeif the rise calculated at Assu4n, but then the river is muddier at Assu^n than at Cairo. The Rhoda Island gauge has been read since A. D. 641, with interrup- tions, and the following table gives the mean readings per century of maximum flood and minimum low supply : Year A. D. Flood. Low supply. No. of years recorded. 641- 700 700- 800 800- 900 900-1000 lOOO-IIOO II00-I2C0 1200-1300 1300-1400 1400-1500 1500-1600 1600-1700 1700- t 800 1800-1892 Meters. R. L., 17.45 17.44 17.68 17.46 17.62 17-74 17.69 18.17 18.00 18.44 18.81 19. 12 20.31 Meters. . L 11.48 10-78 11.52 11.30 II. 61 12. 17 11-43 11.09 11,81 11-93 II. 14 11.77 12.71 62 100 100 100 100 100 100 100 52 52 28 94 The low-level gauges have been vitiated during the last few years by regulation at the Barrages. As the flood and low-level gauges in the above list have no accord Avith one another they are probably incorrect, like all other ancient records in this country. Even in the \ THE NILE. 127 last twenty years the flood gauge has been twice incorrectly recorded. Napoleon's savants relate how it was incorrectly recorded in 1801. At Assu^n the Nile has a mean range of 7.90 meters between high and low supply, with a maximum of 9.80 meters and a minimum of 6.40 meters. The high supply varies between 15,000 and 6,600 cubic meters per second, with a mean of 10,300 cubic meters per second, while the low supply varies between 250 and 1,500 cubic meters per second, with a mean of 470 cubic meters per second. September is generally the highest month and May the lowest. At Cairo the Nile has a mean range of 6.70 meters, with a maximum of 9.2 meters and a minimum of 4.90 meters. The high supply varies between 12,500 and 4,900 cubic meters per second, with a mean of 7,700 cubic meters per second, while the low supply varies between 1,300 and 170 cubic meters per second. October is the highest month and June the lowest. The approximate areas of the catchment basins of the Nile and its tributaries are as follows : Square kilo- meters. 1. The White Nile at the Ripon Falls 260,000 2. The White Nile between the Ripon and Fola Falls 130,000 S. The White Nile between the Fola Falls and Gondokoro 60,000 4. The White Nile between Gondokoro and the Saubat Junction... 190,000 5. The Gazelle River 220,000 6. The Arab River 340,000 7. The Saubat River..... 130,000 8. The White Nile between the Saubat junction and Khartoum 320,000 9. The Blue Nile 310,000 10. The Atbara and Gaash 240,000 11. Desert north of Khartoum 910,000 The Nile 3,110,000 If we examine the plan and note the length of the different rivers and their slope, it will be evident that the Gazelle, Saubat, the Blue Nile, and the Atbara are the ruling factors in flood, while the White Nile is the ruling factor during the remainder of the year. The rainfall about Lakes Victoria and Albert, and about Gondokoro and the upper halves of the Saubat, Blue Nile, and Atbara, may be taken as 2 meters per annum. In the eastern half of the Gazelle River, the lower half of the Saubat, and middle third of the Atbara, 1 meter per annum may be taken as the rainfall. The western half of the Gazelle River has probably 50 centimeters per annum, while the Arab River and tail portions of the White and Blue Nile, and the Atbara, can not have more than 25 centimeters per annum. From Berber northward there is a very scanty rainfall indeed, and the country is considered rainless. Applying these rainfalls to the catch- ment basins we obtain the total mean annual rainfall in the Nile Valley, as follows : 128 CHICAGO METEOROLOGICAL CONGEESS. Mean annual rainfall in the Nile Valley. Square kil- ometers. Meters. Cubic meters. 1. 260, 000 X 1..5 ■=. 390, 000, 000, 000 2. 130,000 X 2.0 rr 260, 000, 000, 000 3. 60, 000 X 2.0 = 120, 000, 000, 000 4. 190,000 X 1.5 z= 285, 000, 000, 000 5. 220, 000 X 0.75 zr 165,000,000,000 6. 340, 000 X 0.25 zz 85, 000, 000, 000 7. 130, 000 X 2.00 = 260, 000, 000, 000 8. 320, 000 X 0. 30 = 96, 000, 000, 000 9. 810, 000 X 1.70 ZZl 527, 000, 000, 000 10. 240, 000 X 1.40 — 336, 000, 000, 000 11. 910,000 X 0.12 = 109, 000, 000, 000 3,110, 000 0. 84 2, 633, 000, 000, 000 We have next to consider the times of rainfall. In the great lake regions the rainy season lasts from March to December, with a max- imum in August. At Gondokoro the rains continue from April to November, with a maximum in August. In the valley of the Saubat tlie rainy season is from June to Novemljer, with a maximum in August. It rains from April to September in the valley of the Ga- zelle River. From July to September is the rainy season at Khar- toum, and from July to August in Kordofan and Darfiir, In Abys- sinia there are light rains in January and February and heavy rains from the middle of April to September, with a maximum in August. August is the center of heavy rainfall everywhere. The time it takes the water to travel down the different lengths of the river may be found from discharge, velocit}^, and slope calcula- tions, and from comparisons between the fluctuations of the Gon- dokoro, Khartoum, Assuan, and Cairo gauges. I calculate that it takes the water eight days to travel from Lake Victoria to Lake Albert and five days from Lake Albert to Gondokoro. There is not much difference between high and low supply in these reaches. It takes the water thirty-six days to traverse the distance between Gon- dokoro and Khartoum in low supply and twenty days in flood. Be- tween Khartoum and Assuan the times are twenty-six days in low supply and ten days in flood. Between Assuan and Cairo we have twelve days in low supply and six days in flood, while between Cairo and the sea we have three days and two days, respectively. It takes eighty-four days for the water in low supply to reach the sea from Lake Victoria, while in flood it takes fifty-one days. The Blue Nile traverses the distance between its sources and Khar- toum in some seventeen days in low supply and seven days in flood. The Atbara takes five days in flood, and the Saubat can not take a much longer time. Referring to the map and keeping all the above facts in mind, an average year in the Nile Basin may be thus described : The heavy THE NILE. 129 rains near Gondokoro begin in April and force down the green water of the swamp regions. About April 15 the White Nile at Gondokoro begins to rise, and by September 1 has reached its maximum. In this interval the discharge has risen from 550 cubic meters per second to 1,650 cubic meters per second. This rise is felt at Khartoum about May 20, and at Assudn about June 10. The green water announcing this rise is seen at Cairo about June 22. In an average year on May 20, the White Nile discharge of 300 cubic meters per second at Khar- toum begins to increase, and goes on gradually increasing to Septem- ber 15 or 20, when the maximum floods of the White Nile and Saubat reach Khartoum and attain a discharge of 5,000 cubic meters per second. The low-water discharge of the Blue Nile is 160 cubic meters per second, and about June 5 it begins to rise fairly quickly and reaches its ordinary maximum of 5,000 cubic meters per second by about August 25. Owing to the two floods rarely being contemporary the ordinary maximum flood of 8,000 cubic meters per second is gen- erally on September 5. The red, muddy water of the Blue Nile reaches Assuan about July 15, and Cairo about July 25. Once the red water begins to appear the rise is rapid, for the Atbara is in flood shortly after the Blue Nile, and its flood waters rise with great rapidity. The Atbara would come down much earlier than it does were it not that a whole month is expended in saturating the desert and its own dry sandy bed. The Atbara flood begins in the early part of July and is at its highest about August 20, reaching an ordinary maximum of 3,400 cubic meters per second, and occasionally an extraordinary maximum of 4,900 cubic meters per second. It is owing to the earliness of the Atbara high flood and the lateness of the White Nile high flood that the ordinary maximum discharge of. the Nile at Assuan is only 10,300 cubic meters per second. This is generally on September 5. When the White Nile is weak the max- imum at Assuan is reached before or on September 5 ; when the White Nile is strong the maximum is reached about September 20. An early maximum at Assuan is always followed by a low summer supply, while a late maximum is nearly always followed by a high summer supply. Only once has this rule been broken and that was in 1891, when there were two maximums, one on September 4 and another on the 27th. In this year there must have been an extra- ordinary fall of rain in Abyssinia in September, for the flood of Sep- tember 27 was very muddy, while as a rule the river at Assuan is very muddy in August, less so in September, and very much less so in October, when the White Nile is the ruling factor in the supply of the river. Appendix I contains discharge tables of the Khartoum, A88uS.n, and Cairo gauges. The zero is everywhere mean low-water level. Appendix II gives five daily gauges and discharges of the Nile at 9 130 CHICAGO METEOROLOGICAL CONGEESS. Khartoum during flood. Appendix III gives five daily gauges and discharges of the Nile at Assu^n throughout the year. Appendix IV gives five daily gauges and discharges of the Nile at Cairo. If the White Nile happens to be in very heavy flood late in Sep- tember, and the September rains in Abyssinia are also very heavy, an extraordinary flood passes Assu^n at the end of September and is disastrous for Egypt. This happened in 1878. Appendices III and IV contain details of this flood, of the minimum flood-year, 1877, and the mean of the twenty years from 1873 to 1892. At Assu^n the Nile enters Egypt, and it now remains to consider it in its last 1,200 kilometers. The ordinary minimum discharge at AssuAn is 170 cubic meters per second, and is reached about the end of May. The river rises slowly till about July 20, and then rapidly through August, reaching its maximum about September 5, and then falling very slowly through October and November. The tables in Appendix III give every detail of a maximum, minimum, and mean year. The deep perennial irrigation canals take water all the year round, but the flood irrigation canals are closed with earthern banks till August 15, and are then all opened. These flood canals, of which there are some forty-five, are capable of discharging 2,000 cubic meters per second in an ordinary year, and have an immediate effect on the dis- charge of the Nile. The channel of the Nile itself and its numerous branches and arms consume a considerable quantity of water ; the perennial canals take 200 cubic meters per second, the direct irriga- tion from the Nile between Assu^n and Cairo takes 100 cubic meters per second, and 100 cubic meters per second are lost by evaporation off the Nile. Owing to all these different causes there is the net result that from August 15 to October 1 the Nile is discharging 2,800 cubic meters per second less at Cairo than at Assu^n. During Octo- ber and November the flood canals are closed, and the basins which have been filled in August and September discharge back into the Nile, and from October 5 to November 15 the Nile at Cairo is dis- charging 1,000 cubic meters per second in excess of the discharge at Assu^n. An examination of Appendices III and IV will show this very clearly. The ordinary minimum discharge at Cairo is 370 cubic meters per second, and is attained on June 10 ; the river rises slowly through July, and fairly quickly in August, and reaches its ordinary maximum on October 1, when there is no irrigation in the basins and the dis- charge from the basins is just beginning. The ordinary maximum discharge at Cairo is about 7,700 cubic meters per second. Through October the Nile at Cairo is practically stationary, and falls rapidly in November. North of Cairo are the heads of the perennial canals which irrigate the Delta proper. These canals, with their feeders lower down, dis- THE NILE. 131 charge 1,200 cubic meters per* second, and the ordinary maximum flood at Cairo of 7,700 cubic meters per second is reduced by this amount between Cairo and the sea. Of the 6,500 cubic meters per second which remain, 4,200 cubic meters per second find their way to the sea down the Rosetta branch and 2,300 cubic meters per second down the Damietta branch. During extraordinary floods the Dami- etta branch has discharged 4,300 cubic meters per second and the Rosetta branch 7,000 cubic meters per second. We have so far considered the Nile in flood, it now remains to quickly dispose of the low supply. After reaching its maximum, the Atbara, which is a torrential river, falls more rapidly than the others, and by the end of October has practically disappeared. After the middle of September the Blue Nile falls quickly, while the White Nile, with its large basin, gentle flow, and numerous reservoirs, falls very deliberately. The mean discharge of the White Nile at Gon- dokoro, in an ordinary year, at the time of low supply, is 550 cubic meters per second. By the time it reaches Khartoum it is reduced by evaporation to some 350 cubic meters per second. The ordinary low supply of the Blue Nile is 190 cubic meters per second, giving an ordinary low supply to the Nile at Khartoum of 540 cubic meters per second. The Atbara supplies nothing. Between Khartoum and Assu^n there is a further loss from evaporation and irrigation of 70 cubic meters per second, and the ordinary low supply delivered at Assu^n is 470 cubic meters per second. In very bad years the dis- charge at Assu4n has fallen to 240 cubic meters per second, which would mean 310 cubic meters per second at Khartoum, probably; and, adopting Linant Pasha's proportion, the White Nile would be discharging 200 cubic meters per second and the Blue Nile 110 cubic meters per second. As the White Nile at Gondokoro never discharges much under 500 cubic meters per second, the loss on that river, under the most unfavorable conditions, is about 300 cubic meters per second, while the loss on the Blue Nile cannot be more than 50 cubic meters per second. Summing up, therefore, we may state that in a very bad summer the Nile sources supply 660 cubic meters per second, the dis- charge at Khartoum has dwindled to 310 cubic meters per second and at As8u4n to 240 cubic meters per second. The moment the daily fall of the river becomes less than the daily loss by evaporation all the small ponds and pools cease to aid the stream, and if they are very extensive, as they are south of Fashoda, they diminish the dis- charge considerably by their large evaporating areas. The six cata- racts of the Nile, with their numerous raised sills, moderate the floods and lengthen them out, but when the two months of real low dis- charge have come the great reservoirs of the Nile are the sole sources of supply. As Egypt possesses no barometric, thermometric, or rain-gauge 132 CHICAGO METEOROLOGICAL CONGRESS. stations in the valley of the Nile, we are always ignorant of the com- ing flood, though famine years in India are generally years of low flood in Egypt. If, however, the summer supply of the Nile has been exceedingly low and exceedingly late, we anticipate a high flood fol- lowing it, as the drought in the valley of the White Nile must create a powerful draught on to the Indian Ocean. Again, as to the summer supply, we generally anticipate a poor volume in the river at that season if the Nile flood at Assu&n is an early one, and a good sup- ply if the Nile flood at Assu^n is a late one. Appendix V, which contains numerous statistics of times and proportions of flood and low supply for the twenty years from 1873 to 1892, fully bears out this statement. Between Assudn and Cairo, previous to 1890, we had little control over the flood, as the canals and escapes in upper Egypt had no masonry-regulating works, and the Nile in high flood did very much what it liked. Since 1890, however, the Public Works Depart- ment has constructed ninety important regulating works, and by proper manipulation we can now fairly control a high flood by using the canals and escapes so as not to let the Nile at Cairo rise above 8 meters, which is the maximum gauge the banks on the Rosetta and Damietta branches can support with any degree of security. It was mainly owing to this power of control that the excessive flood of 1892 passed through Egypt without causing any real damage. The Egyp- tian Government to-day is very seriously considering the question of flood control and increase of summer supply, and we hope to find a solution for the former by escaping excess flood water into some of the depressions which border the Nile Valley, and a solution for the latter by the creation of reservoirs either in the deserts and the chan- nel of the Nile itself north of Wady Haifa, or by regulating works at the sources of the rivers themselves, or perhaps by a combination of both. When we consider the energy and the self-denying labors of the men who achieved the great discoveries of the sources of the Nile, it seems but a poor compensation to them to know that these sources can now be depicted on the plans. It would be a triumph indeed, and a real compensation, if the resources of modern science could be em- ployed to utilize these great lakes, and by the construction of suitable works to insure a constant and plentiful supply of water to the Nile Valley during the summer months when water is scarce and as valu- able as gold. Both the Victoria and the Albert lakes lend themselves to be utilized as reservoirs as they have rocky sills at their outlets, while the Albert and Tsana lakes, by their convenient size, are emi- nently suited for regulating basins. The day these works are carried out at the sources of the Nile the lakes will take their proper place in the economy of the water supply, and we shall be able to say of them in their entirety, as we can say of them to-day in their degree, K >lf - s ^ f^: JJ T. ATs T OF TTT"*^ NHjE, ftoin JujstuB Pertbe's .AS^ico.. Berlizi, l&Oa. I I THE NILE. 133 that what the snows of the Alps are to the Po, lakes Victoria, Nyanza, and Tsana are to the Nile, and what the Italian lakes are to the plains of Lombardy, Lake Albert is to the land of Egypt. APPENDICES. I. — Discharge Tables for the Khartoum, Assuan, and Cairo Gauges. The discharges opposite the gauges are mean discharges. On a rising Nile the discharges are in excess of those in the table, and on a falling Nile they are under them. This will be noticed in Appen- dices III and IV. The site chosen for taking the discharges of a river throughout the year should be such that the bed of the river at the site would be dry if the discharge fell to zero. Deep, scoured-out sections of a river may give fairly accurate discharges in high flood, but they give very inaccurate discharges in low supply, as the action which causes the scour exists only in flood. The following discharges have been calculated from observed sur- face velocities on Harlacher's method (using 0.85 as the reducing constant), and from Manning's formula and surface slope observa- tions (using 33 as the constant) : Approximate discharge table for the Khartoum gauge. [The zero of the gauge is mean low-water level or R. L. 384.00, or 6.30 meters on the gauge which used to stand in front of old Government house at Khartoum. Gauges in meters ; discharges in cubic meters per second.] Gauge. 1 Discharge. Gau ge. Discharge. Gau ge. Discharge. Gau ge. Discharge. I.S 1, 460 3 1 2,700 4 7 4,000 1 6 3 7,420 6 1.530 2 2,750 8 4,180 4 7.690 7 1,600 ^ 2,800 9 4.360 5 7,960 8 1,690 4 2, 850 5 4.540 6 8,230 P 1,780 , 5 2,900 I 4,720 7 8,500 2 1,870 6 2,950 2 4,900 8 8,900 1 1,960 7 3,000 3 5.080 9 9.300 2 2,050 8 3,100 4 5.260 7 9,700 w 3 2,140 9 3.200 5 5.440 I 10, 100 M- 4 2, 230 4 3.300 6 5,620 2 10,500 W' S 2,320 I 3.400 7 5,800 3 10,900 6 2,410 2 3.500 8 6,070 4 11,300 7 2,500 3 3,600 9 6,340 5 11,700 g 2i550 4 3,700 6 6,610 6 12,100 9 2,600 3,800 I 6,880 7 12,500 3 2,650 "" 3.900 a 7.150 8 12,900 Discharge table for the Assuan gauge. [Zero on the gauge is mean low-water level or R. L. 85.00. Gauges in meters; discharges in cubic meters per second.] Gauge. Discharge. Gauge. Discharge. Gauge. Discharge. Gauge. Discharge. — 2.00 —1.20 no — .40 330 0.40 • 650 —1.90 5 —1. 10 130 - .30 360 •50 700 —I. So 10 — 1. 00 '50 — .20 400 .60 750 —1.70 20 — .90 180 — . 10 440 •70 800 —1.60 30 — .80 210 0.00 470 .80 850 —1.50 50 — .70 240 .10 510 0.90 900 —1.40 70 — .60 270 .20 550 950 —1.30. 90 - -50 300 .30 600 . 10 1,010 134 CHICAGO METEOROLOGICAL CONGRESS. Discharge table for the Assudn gauge — Continued. Gauge. Discharge. Gauge. Discharge. Gauge. Discharge. Gauge. Discharge. 1.20 1,070 3-30 2,610 5-40 4.860 7-50 9,000 •3° 1,130 .40 2,700 •50 5.000 • 60 9.320 .40 1,190 •50 2.790 .60 5.140 .70 9,640 •50 1.250 .60 2,880 .70 5,280 .80 9,960 .60 1.310 .70 2,970 .80 5.420 .90 10,280 .70 1.370 .80 3,060 .90 5.560 8.00 10, 600 .80 1.430 .90 3.150 6.00 5,800 .10 11,020 .90 1,490 4.00 3.240 . 10 6,000 .20 11,440 2.00 1.550 .10 3.356 .20 6, 200 1 -30 11,860 .10 1,610 .20 3.472 •30 6,400 .40 12, 280 .20 1,670 •30 3.588 .40 6,600 •50 12,700 •30 1.750 .40 3.704 •50 6,800 .60 13, 120 .40 1,830 • 50 3.820 .60 7,000 .70 13.540 •50 1,910 .60 3.936 •70 7,200 .80 13.960 .60 1,990 .70 4.052 .80 7.400 .90 14, 380 .70 2,070 .80 4,168 .90 7,600 9.00 14,800 .80 2, 160 .90 4.284 7.00 7,800 .10 15, 22c .90 2,250 5-00 4,400 .10 8,040 ■ 20 15.640 3.00 2,340 .10 4.540 .20 8,280 . 10 2,430 .20 4,680 •30 8, 520 .20 2,520 •30 4,720 .40 8, 760 Discharge table for the Cairo gauge. [Gauges in meters. Discharge in cubic meters per second. Zero on the gauge is mean low- water level or R. L. 12.70. Regulation at the Barrages vitiates the discharges below 1.60 at the present time.] Gauge. Discharge. Gauge. Discharge. Ga age. Discharge. Gauge. Discharge. — 1.20 1.30 1,300 3 80 3.750 6.30 6,800 —1. 10 15 .40 1,290 90 3,860 .40 7.050 — 1. 00 30 •50 1. 380 : 4 00 3.970 •50 7.300 — .90 60 .60 1.470 n 10 4,080 .60 7.550 - .80 90 •70 1.560 20 4,190 •70 7,800 — .70 120 .80 1,650 1 ,•^0 4.300 .80 8,050 - .60 150 .90 1,740 '1 40 4,410 .90 8,300 — .50 180 2. 00 1.830 :; .■io 4.520 7.00 8,550 — .40 220 • 10 1.920 ii 60 4,630 .10 8,800 — .30 260 .20 2,010 1' 70 4,740 .20 9.050 — .20 300 •30 2, 100 11 80 4,850 •30 9.300 — .10 340 .40 2,210 1 90 4,960 .40 9.570 0.00 380 •50 2, 320 5 00 5.070 •50 9,840 . 10 420 .60 2,430 10 5,180 .60 10, no .20 460 .70 2,540 20 5.290 •70 10, 380 •30 500 .80 2,650 30 5.400 .80 10,650 .40 570 .90 2,760 ,1 40 5.540 .90 10, 920 .50 640 3.00 2, 870 50 5,680 8.00 II, 190 .60 710 .10 2.9S0 1 60 5.820 . 10 11,460 •70 780 ■ 20 3.090 ! 70 5,960 .20 11,730 .80 850 •30 3.200 j 80 6, 100 •30 12,000 .90 920 .40 3. 310 1 90 6,240 .40 12,270 1. 00 990 •50 3, 420 ; 6 00 6,380 ..so 12,540 .10 1,060 .60 3.530 ID 6, 520 .60 12,8X0 .20 1.130 .70 3.640 1 20 j 6,660 1 II. — Khaetoum. Five daily gauges and discharges for the maximum, minimum, and mean years, from 1873 to 1882, during flood. Zero on the gauge is mean low-water level, R. L. 384.00 meters, or 6.80 meters on the old gauge at Khartoum, on the Blue Nile. THE NILE. 136 Gauges in meters and discharges in cubic meters per second of the Nile at Khartoum for the maximum, minimum, and mean years between 1873 and 1882. [Zero on the gauge is mean low-water level.] Date. Maximum, 1878. Gauge. Discharge. Minimum, 1877. Gauge. Discharge. Mean of 10 years. Gauge. Discharge. June 15 20 25 July I 5 10 15 20 25 Aug. 1 5 10 15 20 25 Sept. I 5 10 15 20 25 Oct. I 5 10 15 June 15 to July 15 July 15 to August 15 August 15 to September 15 . September 15 to October 15. 2. 00 2.00 2-45 2.80 2.80 3.20 3-70 4-3° 4-40 4.60 5.60 6.05 6.40 6.20 6. 10 6.80 7.10 7-3° 7 ..so 7.80 7.60 7.40 7-05 6-75 6.40 2.70 5.00 6-75 7-25 1,870 1,870 2,320 2.550 2,550 2.750 3.000 3,600 3.700 3.900 5,620 6,880 7,690 7.150 6,880 8,900 10, 100 10, 900 11,700 12,900 12, 100 11,300 9.700 8,500 7,690 2,410 4,840 8,940 10, 700 1.90 2. 10 2-45 3-00 2.90 3-55 3- 80 4-30 4-30 4-95 4.60 5.20 5-15 5. 10 5. 35 5.20 5-10 5-20 5-30 5-20 4-95 4-50 4.40 4.20 4.10 2.80 4-65 5.20 4-65 1,780 1,960 2,320 2,650 2,600 2.950 3,100 3,600 3,600 4.360 3,900 4,900 4,800 4,720 5,150 4,900 4,720 4,900 5,080 4,900 4,360 3,800 3.700 3.500 3.400 2,490 4,050 4,890 4,080 1.70 1.85 2.25 2.6s 2.85 3-30 3- 60 4. 10 4.60 5-25 5- 60 5-95 6.15 6.15 6.35 6.50 6.45 6.S& 6.50 6.50 6.30 5-90 5-70 5-50 5-15 2.60 5.10 6.40 5-90 1,600 1,780 2, 140 2,500 2,600 2,800 2,950 3.400 3.900 5,080 5,620 6,610 7,000 7,150 7,600 7,960 7,800 8, 100 7,960 7,960 7,420 6,340 5,800 5.440 4,720 2,350 4.930 7,680 6,550 III. — ASSUAN. Five daily gauges and discharges for the maximum, minimum, and mean years from 1873 to 1892. Mean monthly and yearly discharges for the maximum, minimum, and mean years from 1873 to 1892. Zero on the gauge is mean low-water level, i. e., R. L. 85.00 meters above sea level. Gauges in meters and discharges in cubic meters per second for the maximum, mini- mtim, and mean years between 1873 and 1892. [Zero on the gauge is mean low-water level.] Date. June I 5 10 15 20 25 July I 5 10 15 20 ^5 Aug. I 5 Maximum, i878-'79. Gauge. Discharge. - .68 - .66 - -59 - -32 .67 •94 1.05 1.44 2.47 3.82 5-39 5-62 6.25 240 .19 240 .28 240 .46 240 .91 270 1.09 360 1.07 800 1.30 950 1. 81 1,010 2.13 1,250 3-23 1,910 3-23 3,150 3-70 4,860 4.72 5.280 4.78 6,400 5-35 Minimum, i877-'78. Gauge. Discharge. Mean of 20 years. Gauge. Discharge. 550 .06 480 600 . 10 510 700 . 10 510 900 •36 650 1,010 •49 700 1,000 •72 850 1,130 1. 12 1,010 1,490 1^39 1, 190 1.670 1.82 1,450 2,610 2.25 1,700 2,610 2.87 2,250 2,970 3^71 3,060 4,170 5-16 4,680 4,170 5-71 5,420 4,860 6.59 7,000 136 CHICAGO METEOROLOGICAL CONGRESS. Gauges in meters and discharges in cubic meters per second, etc. — Continued. Date. Maximum, i878-'79. Minimum, 1877- '78 Gauge. Discharge. { Gauge. Discharge. Mean of 20 years. Gauge. Discharge. Aug. Sept. 25- 25- Nov. Dec. I. Jan. Feb. I . April May Month. June July August September October.... November. December . January . . . February . . March April May Mean of the year 7.17 7.48 8.07 7.60 8.14 8.52 8.90 8.86 9.00 9.15 8.92 8.47 7.91 7.60 7.42 6.72 6-34 5-86 5-50 5-17 4.92 4.67 4-54 4-38 4.20 4.09 3-93 3-7° 3-59 3-52 3-41 3-28 3.20 3.12 3-05 2.96 2.89 2-83 2.78 2.74 2.71 2.67 2.60 2.58 2.51 2.44 2.38 2.31 2.22 2.17 2.26 2.24 2.20 2.02 1-95 1.90 2.00 2-17 - -49 2.12 6.85 8.63 8.04 5-58 4-22 3-40 2.91 2.61 2. 28 2.04 4.02 8,280 9,000 11,020 9>320 11,440 13, 120 14, 380 131960 14, 800 15, 220 14, 380 12,280 10, 280 9>320 8,760 7,200 6,400 5. 420 Siooo 4.540 4,280 3.940 3.820 3.590 3.470 3.360 3.150 2.970 2,880 2,790 2,700 2,520 2,520 2.430 2,340 2,250 2, 160 2, 160 2,070 2,070 2,070 1,990 1,990 1,910 1,910 1,830 1, 800 1.750 1,670 1,650 1,700 1,700 1,670 1. 550 1,490 1,490 1.550 1,670 320 1,850 7.840 13. 330 11,040 5.120 3. 470, 2,680 2,200 1,970 1,720 1,580 4.430 •76 2.85 5-64 6.J2 4.98 3-36 2.25 1.62 .80 .16 - .24 - -51 2.32 5.420 7 04 6,600 7 34 6,000 7 62 6,200 ? 8S 6,300 9S 5,800 7 92 5,800 7 87 5.560 7 72 6,400 7 62 5,800 7 30 5.140 7 00 4,680 6 65 4,280 6 32 3.940 ,S 98 3,820 5 65 3,060 5 II 2,970 4 83 2,880 4 51 2,700 4 23 2,520 4 00 2,250 3 76 1,990 3 51 1,910 3 .38 1,830 .S 24 1,670 3 08 1,610 2 96 1,490 2 85 1,490 2 64 1,490 2 55 1,370 2 45 1,310 2 33 1, 190 2 22 1. 130 2 II 1,070 95 950 86 900 74 850 61 800 48 700 39 650 28 600 ■ 19 550 08 520 98 500 87 47P 76 440 61 400 .53 400 44 360 37 360 31 330 26 330 18 300 15 300 09 300 08 270 04 270 00 260 ■05 840 •39 1,670 2-53 5,370 6.80 5.940 7-77 4,420 6.30 2,640 4-37 1,710 3.10 1,280 2-33 840 1.62 530 •97 380 •39 290 08 2, 160 3-05 THE NILE. 137 IV. — Cairo. Five daily gauges and discharges for the maximum, minimum, and mean years between 1873 and 1892. Mean monthly and yearly discharges for the maximum, minimum, and mean years from 1873 to 1892. Zero on the gauge is mean low-water level, i. e., R. L, 12.70 meters above sea level. Gauges in meters and discharges in cubic meters per second for the maximum, mini- mum, and mean years betiveen 1873 and 1892. [Zero on the gauge is mean low-water level.] Date. Maximum, 1878- '79. Gauge. Discbarge. | Gauge. ' Discharge. Minimum, i877-'78. Mean of 20 years. Gauge. Discharge. 15 20 25 July I 5 ID 15 20 25 Aug. I 5 10 15 20 25 Sept. I 5 10 15 20 ^3 Oct. I 5 10 15 20 25 Nov. 1 5 10 15 20 ^5 Dec. I 5 10 15 20 Jan. I 5 10 15 20 25 Feb. I 5 10 15 20 25 Mar. I 10 15 20 25 - .42 180 28 - .48 180 17 - -55 180 15 - -57 170 17 - .62 170 21 - .6g 170 48 - .64 170 73 - .60 170 70 - .10 300 75 •33 500 90 •52 600 I 12 •97 950 I 91 2-54 2,430 2 .S8 3-66 3,640 3 19 4.40 4,410 3 75 4.90 4,960 4 08 5-73 6, 100 4 15 V8S 6,240 i it 6.16 6,660 4 81 6.08 6,380 4 78 6.38 7.050 4 «3 6.72 8,050 4 75 7-23 9,100 4 74 7-52 10,000 4 63 7-98 II, 190 4 80 8.07 11,460 4 74 8-54 12,540 4 59 8.2,S 11.730 4 40 8.11 11,460 4 II 7.80 10, 650 3 91 7-33 9.300 3 68 7.10 8,800 3 43 6.96 8,300 3 15 6.45 7.050 3 2b 5-7° 5.960 3 21 5.06 5.070 3 02 4-63 4.630 2 04 4-45 4,410 2 48 4.24 4,190 2 26 4.04 3.970 2 15 3-91 3.860 2 03 3-79 3.700 91 3-5° 3.420 82 3-35 3,200 75 3-19 3,000 69 2.96 2,890 60 2.91 2,760 40 2.S1 2,650 33 2.68 2.450 20 2.64 2.450 12 2.S6 2,400 01 2.46 2,210 88 2.40 2,210 75 2.34 2, 100 66 2. -52 2,100 59 2.28 2,010 52 2.21 2,010 44 2.17 1,920 46 2.13 1.920 50 2.09 i>8so 39 450 430 430 430 440 600 700 700 800 900 1,010 1.830 2,210 3.090 3.760 4,080 4,190 4,900 4.850 4.740 4.850 4,800 4,800 4.630 4.850 4.740 4.520 4.410 4,000 3.860 3.530 3.310 2,980 3.090 3.090 2,870 2.430 2,210 2,010 1,920 1,830 1,740 1,650 1,560 1,470 1.470 1,290 1,200 1.130 1,060 990 850 780 710 640 640 570 500 470 420 380 370 370 370 420 420 500 550 700 900 1,200 1,700 2.430 3.640 4.520 5.400 5.680 5.960 6,038 6,520 6,800 7.050 7.300 7.550 7.650 7.300 7, 100 7.050 6,800 6,660 5.820 5,200 4.630 4,190 3.750 3.420 3,200 3,000 2,800 2,650 2.540 2,400 2,210 2,150 2,050 1.950 1,880 1,780 1.550 1. 510 1.390 1.390 1,270 1,200 1, 100 1,050 980 960 900 800 138 CHICAGO METEOROLOGICAL CONGRESS. Gauges in meters and discharges in cubic meters per second, etc. — Continued. Date. Maximum, i878-'79. ' Minimum, A^^-'■}9,. I Mean of 20 years. i Gauge. Apr. I ' 2.05 5 ' 2.01 10 1. 98 15 1-96 20 1. 91 „ 25 1-87 May 1 1.84 5 1-73 10 1-73 15 I-7I 20 1.64 25 1.60 31 1-55 Month. June — .57 July .51 August 4.82 September ■ 6. 83 October t 8. 07 November | 6. 29 December 4.0S January 3. 05 February 1 2. 48 March 1 2.18 April 1.94 May 1.69 Mean of the year i 3.45 Discharge. Gauge. ■ Discharge 1 Gauge. Discbarge. 1,850 28 i 400 1.05 750 1,830 19 1 380 1. 00 720 1,740 '? 360 •93 650 1,740 06 330 •87 600 1,740 01 330 .80 570 1, 550 — 06 290 .76 540 1, 650 — 15 290 .70 500 1,560 — '7 i 270 ; .68 480 1, 560 — 21 1 270 1 .66 470 1, 560 — 26 240 i .61 460 1, 470 — 30 240 .61 430 1,470 , — 35 200 ■56 400 1,380 — 42 1 80 •50 380 175 28 ! 480 •47 400 640 i I 16 1, 120 1-23 1,090 5,150 3.94 1 3.930 4.80 4,930 8, 250 4 70 1 4.780 6.32 7,040 '.350 4-33 ! 4,290 6.35 6,940 7. 020 3 20 3.050 4-30 4.300 4, 030 2 18 1,960 2.86 2,700 2, 890 ] I .■Sb 1,400 2.14 1.950 2,270 89 880 1.64 1.350 1,950 j 4b 520 1-30 940 1,740 ! 07 340 .87 620 1.520 1 — 30 240 .62 440 3, 920 1 I 88 1,910 2.74 2,730 V. — Tables and Statistics. Miscellaneous tables of times and heights of high flood and low water level, disposal of the water of the Nile between Assu^n and Cairo, proportion of rainfall discharged into the sea, and approximate quantity of solids discharged into the sea and deposited on the soil of Egypt in an average year at the present time : Table giving dates and heights of the real minimum at Assudn. [Zero of the gauue means "mean low-water level."] Meters. 1 i873,June5 —0.37 1874, May 30 — o. 64 1875, May 23 —0.17 I 1876, June 15 +0.13 1 1877, May 27 4-0.10 1878, June 23 —0.71'' 1879, May 23 + I. SS*" 1880, J une 9 + o. 82 1881, May 14 4- o. 00 J 1882, June 23 — o. 55 I » Worst low supply. Meters i883,June22 -f- 0.04 1884, May 27 -j- 0.37 i885,June2 — 0.44 1886, June 3 — 0.06 1887, May 8 — 0.03 1888, Junes — 0.08 1889, June 24 — 0.60 1890, June 8 — 0.60 1891, May 19 — 0.21 1892, June 18 — o. 64 •"Best low supply. The river was below the mean low-water level thirteen years, and above seven years. The mean of the minimum is — 0.08 meters. In order to find the date of real minimum at Cairo add twelve days to the above dates. The Cairo gauge at this stage of the river is valueless as the regulation at the Barrages affects it. Very high floods scour out the deepest parts of the river's bed, and a gauge of —0.60 meters in 1878 and 1889, after the poor floods of 1877 THE NILE. 139 and 1888, gave a discharge 25 per cent less than a gauge of — 0.60 meters iu 1892 after the good and late flood of 1891. Table giving dates and heights of the maximum flood levels at Assudn. [Zero on the gauge means " mean low-water level."] Meters. \\ 1873, Sept. 1 7 1874, Sept. 6 8 1875, Sep. II 8 1876, Sept. 7 8 1877, Aug. 20 6 1878, Get. I 9 1879, Sept. 13 8 1880, Sept. 4 7 1881, Sept. 4 8 1882, Aug. 28 8 »The poorest flood. ^The highest flood 883, Sept. 17 . 884, Sept. I . 885, Aug. 23 . 886, Sept. 22 887, Sept. I . . 888, Aug. 24 . 889, Sept. 2.. 890, Sept. 2 . 891, Sept. 4. . 8q2, Sept. 20 , Meters. « Sept. 22, 7.60. ii Sept. 10, 8.00. 'Sept. 27, 7.1 The late and very high flood of 1892 is being followed by a sum- mer supply in the Nile nearly as high as that of 1879 after the very high and late flood of 1878. A mean high flood is 7.90 meters ; the mean of the maximum is 8.17 meters. Table giving the dates and heights of the maximum flood levels at Cairo. [Zero on the gauge means "mean low-water level."] Meters. 1873, Sept. 14 5. 86 1874, Oct. 6 8. 70" 1875, Oct. 18 7.44 1876, Sept. 27 7. 69 1877, Aug. 27 4-95 1878, Oct. II 8. 56" 1879, Oct. I 7.60 1880, Oct. 26 6.08 1881, Oct 13 7.38 1882, Oct. 28 6. 02 » Should be 8.25. Meters- 1883, Oct. II 7.38 1884, Oct. 25 6.52 1885, Oct. 18 6. 67 1886, Oct. 4 6.42 1887, Sep. 25 7.93 1888, Sept. 15 5.34 1889, Oct. 16 6. 74 1890, Oct. 25 7.12 1891, Oct. 25 6.72 1892, Oct. 7 7.93 '•Should be 8.15. In 1'874 and 1878 the gauges were incorrectly recorded at Cairo. Corrections have been applied by calculations from the Barrage gauges. The most serious flood of the century was that of 1878, but what its height might have been at Cairo will never be known as the Nile banks were swept away on October 11, while the Nile was rising. The mean of the maximum is 6.95 ; a mean high flood is 6.70. Table giving approximate dates on which maximum and real minimum guages were reached at Assudn. Number of times minimum. May 10. 15. 20. 25. June 1.. 5.. 10 15 20 25 1 1 1 4 1 2 3 1 2 4 20 Number of times maximum. Aug. 20. 25. Sept. 1 , 10 15 20 25 1. Oct. 1 2 6 4 1 2 2 1 1 20 140 CHICAGO METEOROLOGICAL CONGRESS. Table giving approximate dates on which maximum and real minimum gauges were reached at Cairo. Number of times minimum. May 20 1 25 1 June 1 1 5 5 10 3 15 2 20 3 25 1 July 1 1 5 2 Number of times maximum, Aug. 25 1 Sept. 15 2 25 2 Oct. 1 1 6 3 10 2 15 3 20 1 26 5 20 20 The date on which the real minimum is reached is the last day of low supply before the final rise begins ; occasionally the actual mini- mum, a few centimeters below the real minimum, precedes the latter by many days. Calculation explainivg the consumption of water in an average year between Assudn and Cairo. [An Egyptian acre equals 4,200 square meters.] Evaporation off the basins — Cubic meters. 1,500,000 acres X 4.200 X .008 daily X 45 days equals 2,268,000,000 Evaporation off the Nile itself — 950,000 meters X 700 meters X 2.00 meters equals 1,330,000,000 Irrigation of 060,000 acres of land perennially irrigated — 660,000 X 4,200 X 2.00 meters equals 5,544,000,000 Escapes directly into the Rosetta branch 500,000,000 Total expenditure 9,642,000,000 Cm. per sec. Mean discharge per day at Assuan, from Appendix III 3, 150 Mean discharge per day at Cairo, from Appendix IV 2,730 Balance spent 420 Total quantity of water expended between Assuan and Cairo in one year equals 365 X 420 X 86,400, amounting to 13,245,000,000 Therefore the quantity of water absorbed into the soil per annum equals 13,245,000,000 — 9.642,000,000 = 3,603,000,000 cubic meters, and as this is absorbed over an area of 2,210,000 acres, the depth of water absorbed equals ,3,603^000,000 ^ 3^3 ^ ^^ meters. ^ 2,210,000 X 4,200 ^9,282 Table showing the amount of water which reaches the sea in an average year. From Appendix IV, the mean discharge at Cairo =: 2,730 cubic meters per second. From this deduct the water withdrawn from the Nile by the Delta canals north of Cairo, viz.: Cm. per sec. Cm. per sec. January 300 August 1,000 Februarv 300 September 1,200 March..; 300 October 1,200 April 300 November 500 May 350 December 300 June 400 July 500 Mean for the year 654 THE NILE. 141 Therefore the discharge into the sea =: 2,730 — 554 = 2,176 cubic meters per second, or 68,600,000,000 cubic meters per annum. As the average rainfall in the Nile Basin has been found to be 2,633,000,000,000 cubic meters per annum, the water which reaches the sea := — or say — of the rainfall. 39 -^ 40 Table giving the quantity of solid matter carried to the sea by the Nile in an average year. [See proceedings of the Institute of Civil Engineers, Vol. LX, i87g-'8o.) Month. Discharge of the Nile at Cairo in cubic meters per second. Discharge of the Delta canals. Discharge en- tering the June July August September October ... November December. January... February . March .... April May 400 1,090 4.930 7,040 6,940 4.300 2,700 1.950 1.350 940 620 440 400 500 1,000 1,200 1,200 500 300 300 300 300 300 350 590 3.930 5.840 5.740 3.800 2,400 1,650 1,050 640 320 90 6.9- -100,000 = 0.0 17.8-: -100,000= .105 149.2- -100,000 = 5.864 54.3- -100,000 = 3.171 37.8- -100,000 = 2.170 34.4- -100,000 = 1.307 28.9- 1-100,000= .694 16.7- -100,000= .276 12.6- h 100,000= .132 5.3- -100,000= .034 6.6- -100,000= .021 4.8- -100,000= .004 Solids carried in suspension in cubic meters per second. June OX July 590 X August 3,930 X September 5,840 X October 5,740 X November 3,800 X December 2,400 X January 1,650 X February 1,050 X March 640 X April 320 X May 90 X Mean 1.1465 Total quantity of solids carried to the sea in an average year equals 365 X 1.1465 X 86,400 = 36,156,000 cubic meters or tons. Table giving the approximate quantity of solid matter carried by the Nile at Assv^n in an average year. [From Table III. Solids carried in .luspension in cubic meters per second.] June 660 X July 2.080 X August 7,850 X September 9,810 X October 6.400 X November 3,550 X December 2,380 X Janwary 1,750 X Februarv 1,280 X March .' 920 X April 630 X May 500 X Mean 1-907 6.9- -100,000 = .045 17.8- - 100.000 = .370 149.2- -100,000 = 11.712 54.3- -100.000 = 5.327 43 - -100.000 = 2.752 40 - -100,000 = 1.420 28.9- -100,000 = .690 16.7- - 100.000 = .292 12.6- -100,000 = .161 5.8- -100,000 = .049 6.6- - 100.000 = .042 4.8- - 100,000 = .024 142 CHICAGO METEOKO LOGICAL CONGRESS. Total quantity of solids carried past Assuan in an average year equals 365 X 1.907 X 86,400 = 60,160,000 cubic meters. Quantity of solids deposited on the soil of Egypt equals 60,150,000 — 36,156,000 = 23,994,000, or 24,000,000 cubic meters per annum. As the area over which this is deposited is 4,950,000 acres, the depth deposited per 100 years equals 24,000,000 _ 4,950,000 X 4,200 —-^^^ meter.s. Before basin irrigation was changed into perinnial irrigation over two-thirds the area of Egypt the mean deposit must have been considerably greater. 8.— THE BEST MEANS OF FINDING RXTLBS FOR PREDICTING FLOODS IN WATER COURSES. M. Babixkt. It does not appear to me possible to exhaust in a few pages the subject proposed to M. Lemoine, Inginieur en Chef des Fonts et Chaiissees at Paris, in charge of the Central Hydrometric Service in the Basin of the Seine, by the Honorable President of Section II of the International Congress of Meteorology, held at Chicago in the month of August, 1893. Very happily, the task to be fulfilled is well defined by a very clear programme, to which we reply with our best effort, but of which the last two questions apparently ought to be interchanged for clearness of exposition. QUESTION I. What ought loe to propose to ourselves in the matter of flood predictions; ought prediction to be general or specific as regards the stations and the levels which we are to expect there f It is not very difficult to predict that a flood river is going to rise when one has knowledge of abundant rains fallen over its basin ; the consequences are particularly grave in the higher portions of the country when the impermeability of the soil is there very marked ; the slopes of the land there facilitate in every instance the superficial draining or deter evaporation or absorption by the soil. So, then, one may rely on a few rain gauges judiciously distributed and connected with a central station as sufficiently adequate to organize a system of flood predictions. Date of maximum. — This first result which, moreover, must not be considered as altogether negligible, may be improved if we strive to forewarn the inhabitants of a determined locality, in place of simply predicting a rising of the level of the water in a whole region.. We shall soon be led to state precisely the epoch when the level will RULES FOR PREDICTING FLOODS. 143 attain its greatest height at the place considered, from similar phe- nomena observed up the stream and signaled by the telegraph. The importance of the principle of the time of propagation of the maximum is thus made evident. Importance of the flood. — We can not admit that a flood has been thoroughly announced if we content ourselves with indicating merely the time of its passage at such and such a point without troubling ourselves with the level it is to attain. Even when the insufficiency of previous investigation and verification does not allow of detailed predictions, if the service is content with simple warnings, there can generally be added to the word flood a qualifying word, such as feeble, mean, or strong. This is a first approximation ordinarily realizable everywhere from the recollections of the people of the country, or from the mean of a small number of observations. Numerical 'predictions. — To go further and hazard the indication of a stage of determined height on an invariable river gauge, it is certainly preferable to be able to make numerous comparisons be- tween a large number of occurrences of high water. However, the illustrious Belgrand, founder of the Hydrometric Service in the Basin of the Seine in 1854, whose researches are appreciated to-day in the entire world, did not take more than two years to establish a formula for predicting three days in advance the total rise of the Seine at Paris from those of the upper tributaries, as shown by eight well- chosen stations toward the limit of the most distant impermeable lands drained. In spite of the apparent complication of the basin of the Seine, where the water courses of equivalent importance are numerous with their superficial drainage converging on the outskirts of Paris, the same principles applied with perseverance by M. G. Lemoine, pupil of Belgrand, and by his co-workers, have allowed of predicting for the past twenty years the probable levels of the impor- tant floods on the Seine and principal tributaries to within 30 or 40 centimeters, or better. Similar studies inspired or not by the same principles have succeeded as well elsewhere. They have been instituted in France (1st) on the Loire at Orleans, (2d) the basin of the Meuse almost exactly at the time when Belgrand drew from the first results a new science of hydrology of which the announcement of floods is only an application, (3d) on the Saone, the Garonne, the upper and lower Loire, and more recently in several parts of the basin of the Rhone. They did as much in Italy for the basins of the Arno and the Tiber about 1866, a little later on the Elbe in Bohemia, and finally on the Ohio and Mississippi in the United States since 1884. Without con- sidering the most convenient processes for each basin, according to its configuration and the lands that compose it, we can affirm the possibility of predicting floods almost everywhere outside of the 144 CHICAGO METEOROLOGICAL CONGRESS. mountainous regions where they are formed, and where their ravages are less to be dreaded than in the fertile plains menaced by the over- flow of water. QUESTION II. What arrangement of hydrometric stations on the principal rivers and on their tributaries is the most advantageous for predicting levels ? The choice of means to be employed for announcing floods, and particularly numerical predictions of heights on certain gauges, de- pends essentially on the time available for concentrating the infor- mation as to the stages at points along the upper courses and the time required for giving information of their results to points lower down. The number of hours depends materially on the rapidity of propaga- tion of the wave, but the facility of transmission of the warnings principally by telegraph plays also an important role and at times preponderates in the question. A. Long-time forecasts by means of upper tributaries. — However per- fect may be the communication from one point to another along a w^ater course, it is always advantageous to note the indications as far up the river as possible. In this method we are only limited by the multiplicity of nearly equal influences of which it is then neces- sary to take account. Thirty or forty years ago the French telegraph system was yet little developed. Warnings were mostly sent by post. In order to have time to receive data for the problem Belgrand had taken typical stations in the circumference of the Seine basin at a convenient dis- tance from the water-parting, approximately on the arc of a circle of which Paris is almost the center. He remarked, moreover, that in these regions, as everywhere else, the water courses from impermeable land carry off almost all the rain that falls over their drainage areas, consequently, they determine the beginning and maximum of floods. In the basin of the Seine the permeable lands cause the level to be sustained for a period of greater or less length, according to the duration of the rain, after the complete saturation of the soil ; their levels rise and fall slowly, and their influence is more often negligible or very secondary. B. Short-time forecasts by means of several upper observation stations. — The observation stations used for the announcement of floods at Paris, so reduced to eight, are yet sufficiently numerous for their influence on the result to vary a little from one flood to another, according as the rise is earlier or later at one point or the other. Thanks to the actual rapidity of the telegraphic transmission, the indications that one receives thus from the most distant observers serve to establish three days in advance at least a first approximation, subject to correction by subsequent warnings from nearer stations. RULES FOR PREDICTING FLOODS. 145 For these corrections, as well as for announcements destined for certain stations less distant from the water-parting, we can utilize the relations which generally connect the maximum level prob- able at one given point with the corresponding levels observed by- two gauges situated up the stream on the two most important water courses of which the union forms the one which passes by the place considered. In order that a relation between three heights of water thus chosen may be utilized, it is sufficient that the first two stages be known long enough before the realization of the third which results from it. It is thus that the levels observed on the Seine at Paris, and on the Oise at Compiegne, allow of announcing the maximum of the Seine at Mantes the next day. The floods of the Marne at Epernay, and of the Yonne at Sens, among others, are generally predicted in their details by the same process. On many rivers whose basins have not the same configuration as that of the Seine, and where the propagation of floods is much more rapid, it may happen that this arrangement of observations gives by itself good results in practice. If there are more than three water courses of equal importance, the corresponding heights of water of the affluents may be combined, forming a mean, which may be treated as the actual stage at a second upper station, as in the case cited above. It is in this way the announcements of floods on the Loire are made at Nevers. C. Use of a single station at a point above. — The problem is much simplified if the principal water course receives no important affluent for a distance sufficient for the announcement of floods to precede their occurrence. It is this that happens first for the Loire between the points where it receives successively the Allier below Nevers and the Cher at Tours, second for the Saone up the river to Lyons from the confluence of the Doubs. In this case the maximum to be pre- dicted for the lower gauge is a function of a single variable which represents the level attained on the upper gauge. If we develop this function in series according to the increasing powers of the variable, we can at times neglect the second and higher powers when the series is converging ; the result is the same as if we admitted a priori the proportionality between the two stages. To facilitate the announcements, the length of river unprovided with affluents ought to be greater in proportion as the slope is more rapid and gives to the water course in consequence a character more torrential. It is impossible to establish very precise general regula- tions on this subject, for in France, at least, the speed of propagation of the maximum varies much from one river to another and on the same river in different parts of its course; it does not exceed 4 kilometers an hour on the Saone or on the Seine below Paris, while it attains 6 kilometers on the Garonne, 8 to 10 kilometers, and some- times more, on the Rhone or the Durance. We must have at least 10 146 CHICAGO METEOROLOGICAl CONGRESS. twelve hours interval before us after the maximum occurs up the river in order to give warnings to points below ; this is even insuffi- cient if the rise is rapid and occurs in a night. D. Importance of the determination of the maximum. — Self -recording apparatus. — Whatever may be the arrangement of the observing sta- tions, according to circumstances, we can not insist too strongly on the necessity of knowing exactly the maximum, its height, and the exact moment it occurs at each gauge in order to make precise com- parisons. The natural law, according to which a variable quantity changes slowly in value in the neighborhood of a maximum or a minimum, and more rapidly in every other case during the intervals between them prevents making any verj" great errors in this matter in tranquil rivers whose regimen is permanent. The difl&culties are much greater on certain torrential affluents where the observations at fixed hours, however close together they may be in times of flood, allow the most interesting heights to be missed and also the moment of their occurrence. In order to guard against this incon- venience, self-registering apparatus of various kinds is beginning to be be employed in France, not only in Paris and its outskirts, but particu- larly in the basin of the Durance, the principal affluent of the Rhone, where the slope of the water courses and the rapidity of their floods are quite exceptional. This means of investigation can not be passed over in silence to-day, and will probably permit of pursuing investi- gations, which otherwise would not give any important result. QUESTION III. What are the best methods for finding rides for announcing floods f According to the difficulties considered in the above paragraphs. A, B, C, and D, two general processes are recommended for forecasting the levels of rivers at stations : ( 1 ) by utilizing the risings of the principal water course and its affluents, that is to say, the differences between the minimum, where the rise of water begins (initial stage) and the maximum, where it ceases. (2) By comparing the highest absolute stages that the water reaches successively at different points during the considered flood. 1. Announcement of floods by rises. — The first process is alone applica- ble to the long-time predictions of paragraph A ; this is what Belgrand employed for announcing the floods on the Seine at Paris in 1856. It eliminates an important source of error by taking count of the ine- qualities of the initial stage on the gauge for which the predictions are made. To this stage (variable according to the circumstances which have preceded the flood considered ) we add a probable rise calculated by the aid of the actual rises at the stations of observation above ; it will generally be a function of the first degree if the development of the series which corresponds to the influence of each gauge up the river allows of considering them as converging rapidly enough. RULES FOR PREDICTING FLOODS. 147 The study of the rises is particularly indispensable if one considers a multiple flood ; that is to say, if a continued great elevation of water on the gauge is produced by many distinct oscillations of the water up stream. The case is presented frequently at Paris, and in the outskirts, where the waters supplied to the upper affluents unite from successive falls of rain. The case in point is due to the per- meable lands from which the waters arrive late after those of the im- permeable lands and sustain their floods. The highest stages attained by the affluents do not then permit of foreseeing directly the maxi- mum down the river as one would hope if there was only a single rise at each station up stream. We try, often with success, to take for the probable rise at the sta- tion a simple mean of observed rises on the upper secondary basins by taking count of the inequality of the surfaces and of the partic- ular degree of impermeability of each one of them by appropriate coefficients, or by the choice of many stations in the same basin, as Belgrand has done by taking at the same time the rises of the Marne at Chaumont and at St. Dozier for announcement at Paris. If the hypothetical relation between the rises up and down stream does not appear to be sufficiently simple, the proceedings indicated in the outline sketch by Mr. D. Deague (Gauthier Villars, 1892, pp. 65-81), will permit of giving to it a graphic representation; if necessary, one can state the equations of relation by means of un- known coefficients, and determine those coefficients by the method of least squares, so as to satisfy in the best way a certain number of observed cases ; but this method, very laborious, has the inconve- nience of not well taking account of the natural circumstances by which the floods are distinguished. Some rapid " trials," without direct solution, led to the same re- sults, as has been demonstrated by Inspector General Allard (Annales des Fonts et Chaussees, 1889, ler sem., Le Seine, Tome i, p. 631). Nothing proves, moreover, that the relation above mentioned should be a continuous function of the variables it represents, and there are even some chances that it may be otherwise when the real rises sur- pass certain critical points, at some stations, such as certain levels of submersion beyond which the wetted perimeter of the bed of the river changes quickly. One is thus led to form categories of similar floods for a given sta- tion and to modify the formula of prevision according to the catego- ries. A trial of this kind has been made quite recently for many gauges in the basin of the Oise, but in such cases there is great dan- ger of multiplying too much the particular cases so that they are not readily recognizable. By taking as abscissae a conveniently chosen function of the rises at certain of the upper stations and as ordinates a similar function 148 CHICAGO METEOROLOGICAL CONGRESS. of all the others, and writing by the side of the point thus deter- mined the actual corresponding rise observed at the station for which the prediction is to be made, the locus of the points of equal stage may be considered as the projection of a curve of levels of a surface which will give some idea of how the rises in question are related. 2. Predictions by absolute stages. — This representation of a law estab- lished between many variable quantities is utilized by M. Mazoyer for the announcement of the floods of the Loire at Nevers (Annales des Fonts et Chnuss^es, 1890, 2d sem., Tome xx, pp. 441-511) ; but in place of rises the highest levels attained at each point are considered. A similar graphical process had been in use since 1882 for studying the relation between the maximum of the Seine at Rouen, that of the Seine at Mantes, and the level of the open sea at Havre, about thirty- six hours after this latter. If we consider the simple floods in which the elevation of the water observed at a station arises from a single similar movement observed at a distant station up stream without any intermediate affluent, the comparison of rises is no longer essential. The highest levels attained at both places are then generally in direct relation ; in taking the first as abscissa?, the second as ordinates, we o.ften find that the ex- tremities of the latter depart but little from a regular curve which is useful in making predictions. The Hydrometric Service of the Basin of the Seine has established many graphics of this kind which it uses to great advantage. It goes without saying that the above curves may be replaced by tables of single or double entry ; this latter process has been in pref- erence employed by M. Jollois for the floods of the upper Loire {An7iales des Fonts et Chaussees, 1881, ler sem., Tome i, pp. 273-322). CONCLUSION. The rules just considered for predicting floods are quite simple enough ; for finding them or making application of them, it suffices to observe exactly the heights of the water, either by the eye directly or by self -registering apparatus well maintained. It seems certain that we may obtain thus in most cases satisfactory predictions, par- ticularly by carefully studying the conditions supplied by the greatest known floods. Predictions by means of discharges. — A method rather more com- plicated, of which the principle is due to M. Harlacher, Professor at the Higher Technical School at Prague, gives, it appears, good results on the Elbe in Bohemia. It might be recommended in analogous circumstances, though it can not be made use of very easily in many other cases such as described above. It presupposes essentially that the progression of the floods at a station depends exclusively on the heights observed at several stations up the stream sufficiently distant RULES FOR PREDICTING FLOODS. 149 from the point to permit of sending warnings in time to be useful without the rains or affluents of the intermediate region playing any- important part. It is necessary, moreover, to have determined for each gauge an exact relation between the height of water and the dis- charge per second, which presupposes long and minute investigations carried on by the same persons in order to make them comparable. If the stations of observation are so situated that the water passing them reaches the lower station at the same time there can be deduced from the heights observed at the points above the corresponding dis- charges, and, by a simple addition, the discharge down stream, which determines the height to be there expected. This metljod ought to give the best results when, at the stations above, the discharge is strictly defined by the height of the water (which pre-supposes in- closed valleys, on which a great variation of level can be observed for a small change of discharge), and that at the same time down stream an appreciable error in discharge does not involve a great uncertainty in the height of water (which will happen only in a flat valley with a large broad bed). These conditions do not always happen to be united. The Central Hydrometric Service of the Basin of the Seine has tried to apply the method of M. Harlacher for pre- dicting one day in advance the probable maximum at Paris from those of the Seine at Melun, and of the Marne at Chalifert (near Meaux), l")ut without success. The curves of relation between the heights of water and the discharges were perhaps not exact enough ; those of M. Harlacher are the result of eighteen years' continued research without change of supervision or control. Predictions based on observations of rainfall. — Finally, in the im- permeable basins of certain torrential rivers with heavy slopes, the time available for making predictions from heights of water ascer- tained up stream, even near the watershed, would be quite insufficient ; a case is presented in France, notably in the water courses which flow from the Cevennes toward the Rhone and toward the Mediterranean. As the floods are at times exceptionally disastrous in that region, M. G. Lemoine has quite recently proposed to determine precisely the relations between their height and that of the rain falling some days before. The commission for predicting floods, instituted since 1875 under the Minister of Public Works, has had established provisional flood-warning services predicting on this principle. The relations sought for will probably be indicated most precisely by means of self- registering rain gauges. Investigations of this sort seem to be the order of the day ; one may get an idea of them by consulting the Annales des Fonts et Chaussees, 1888, ler sem., Tome xv, pp. 464-510; and 1892, ler sem., Tome iii, pp. 166-196. But they are still theoretical rather than practical, and it remains for the future to perfect them. SECTION III. MARINE METEOROLOGY. 1.— THE FORECASTING- OF OCEAN STORMS AND THE BEST METHODS OF MAKING SUCH FORECASTS AVAILABLE TO COMMERCE. William Allingham. Every seafarer will very readily admit that the forecasting of such dread meteors as ocean storms is a far easier matter in theory to the few than in practice to the many. Hence, I approach a considera- tion of this intensely interesting and highly important subject with a feeling of diffidence verging on despair. The interval allotted for reading the paper is necessarily limited, the field for discussion so vast and fertile, that for mortal to command success in his venture is impossible, however much he may strive to deserve it. Nautical men there are, under every sky in the wide world's navies, whether of peace or of war, thoroughly competent to treat the vexed question of ocean storms from a higher plane than I. The arduous duties of our noble but neglected profession, however, too often preclude close application to clerkly work of this nature, and mankind is thereby a decided loser. I have, therefore, accepted the invitation which you have done me the honor to give, as an earnest that, in the words of the illustrious Maury, a seaman is fit for other things than tacking ship or washing down decks ; and in the sincere desire to arouse sea- farer's of every nation not only to assist in weather work by recording observations at sea and in unfrequented ports, but also by taking a far more active part in conferences at which nautical matters are brought forward for detailed discussion. The forecasting of ocean storms is of great utility, both to those that go down to the sea in ships and to those who prefer to gaze upon the mighty ocean from dry land. I have, consequently, deemed it necessary to deal wdth the subject chosen for me from both points of view. A navigator, remote from the land and the electric tele- graph, is perforce his own forecaster of ocean storms ; and the gravest responsibility attaches to his decision, inasmuch as a misinterpreta- tion of the scanty data at hand may tend to the total loss of his 160 I FORECASTING OF OCEAN STORMS. 151 devoted bark and all her crew. He will rely upon such signs as sky and sea afford to men whose lives are spent in continual conflict with the elements ; while, at the same time, not unmindful of instrumental indications and the published deductions from the experience of navigators who, in some instances, will long since have passed away down the dim corridors of time. An overwhelming torrent of litera- ture relating to the law of storms has flooded the market since it was first formulated, and the ebb is not yet. It would, however, be utterly unsafe to assume that increased certainty has been borne on- ward by the turbulent, frothy stream of words, either as to the law itself or the deductions therefrom embodied in so-called rules for handling a ship that she may altogether avoid, or partially utilize, the winds of a cyclonic storm. Despite the immense amount of labor bestowed upon tracking these meteors by the aid of syn- chronous charts, I am reluctantly compelled to confess, without reserve, that navigators have not been supplied with much informa- tion of really practical value with respect to ocean storms subsequent to the discovery that they are, generally speaking, circular whirls of varying size and energy ; moving onward, now fast, now slow, over the waste of waters. The sailor is unable to depend implicitly on the curiously contradictory conclusions of modern professional and amateur weather workers. He not infrequently finds that his own watchfulness and faculty for generalization are much more essential to safety than all the drawing-room storm maneuvers in existence. Forecasting of storms at sea involves a rapid approximation to the values of several variable quantities ; and, having regard to the indisputable fact that weather workers on shore, although assisted as far as possible by electric communication with outlying districts, occasionally forecast a storm which fails to put in an appearance, or let one slip in on them unwittingly, there is matter for congratula- tion that navigators come out of the ordeal by wind and wave so well. To insure an exact result to any given prediction of an ocean storm the anxious but self-reliant mariner must know the bearing of its center, its distance from the ship, the direction whither it is traveling, and its rate of motion onward. Need I say that the modern book compiler, in a hurry, has only helped to make confusion worse confounded as regards our knowledge of these points. I most heartily agree with a statement referring to ocean storms made by a well-known navigator, Capt. S. T. S. Lecky, R. N. R., that "we can not but feel that to a great extent their origin, shape, and move- ments are, as yet, purely matters of speculation. So much that is contradictory is daily appearing, and such various plausible theories are being propounded, that it is most difficult to arrive at any safe and practical conclusion." Probably no great discovery has ever flashed upon the world unless, 152 CHICAGO METEOROLOGICAL CONGRESS. and until, a path had been cleared through a dense growth of rank weedB of empiricism, and doubtless many a one came within almost measurable distance of the law of storms prior to the advent of Red- field. The first hurricane on record is perhaps that which Christopher Columbus and his hardy toilers on an unknown, awe-inspiring sea endured for three days and nights of leaden-footed hours in their tiny craft near the Azores in February, 1493. It is, therefore, peculiarly appropriate for prominent mention in this paper when all the world and his wife have set their faces toward the Columbian Exposition at Chicago. Even five centuries ago seafarers noticed that the storm- wind did not blow unceasingly from one direction only, but from several points of the compass in succession. The Philosophical Trans- actions of 1698 contain a clearly-drawn word picture of West Indian hurricanes by a Capt. Langford, who was evidently intimately ac- quainted with some of these undesirable visitors. This old-time navi- gator pointed out that a West Indian hurricane is a whirlwind, in which the gale commences from the northward, gradually changing through west to south and southeast, which point being attained its fury forthwith abates ; or, as the modern mariner, even of the most slender experience, would say, cyclone centers travel westward to the northward of the West India Islands. One page of nature's entranc- ing book lay wide spread before the observant eyes of that merchant shipmaster, yet he failed to decipher its crabbed characters by the imperfect light which then prevailed in the world of science, even though he quaintly relates that storm warnings sent to more western islands from Dominica and St. Vincent, ten days in advance, were generally correct. He used to get under way and run out before the northerly gale in order to obtain the necessary and sufficient searoom to keep clear of the land when the wind should shift to southwest. Three centuries ago, then, seamen were well aware that West Indian hurricanes are whirlwinds of comparatively insignificant diameter but awful energy, and that they might be fallen in with most often from July to September. Little if anything, however, was known as to their direction and rate of travel. The full, change, and quarters of the moon were considered critical periods, especially if the sun were exceptionally red, the stars with halos, the hills unusually free from cloud and mist, the northwest sky black and foul, or the sea smelling more strongly than its want. Franklin, in a letter dated at. Philadelphia, July 16, 1747, wrote that " the air is in violent motion in Virginia before it moves in Connecticut, and in Connecticut before it moves at Cape Sable," thus foreshadowing the result arrived at by Redfield, a naval architect of New York, to whom the world is deeply indebted for the very first reliable enunciation of the law of storms. He gathered together ships' log books, laid down the data thus obtained in their respective geographical positions on simple synoptic charts, FORECASTING OF OCEAN STORMS. 153 and after several years of patient inquiry promulgated his views about 1831. After the lapse of more than three score years this dauntless worker in the thorny path of unendowed scientific weather research still stands head and shoulders above all comers, save Maury, who has never been equaled as a passage shortener for sailing ships. Neither the masterly deductions of Redfield nor his well-devised methods of discussion have been improved upon, except in unimportant details. He demonstrated that North Atlantic cyclones have their birth place eastward of the West Indies ; that their diameters measure 90 miles and upward ; that the wind force increases as the center is ap- proached ; that the rate of travel is from 10 to 30 miles an hour along a parabolic trajectory having its vertex, or point of recurva- ture, near the American coast in about N. 30°; that the changes in wind directions experienced by ships as a cyclone passes over vary according to their positions with respect to its center; and suggested that a cyclone whirled round a cylindrical axis which might be ver- tical or inclined, and, perchance, staggering on its course afflicted with a kind of nutation, thus causing the violent gusts and interven- ing lulls met with in the vicinity of the center. There is nothing new in the much-vaunted indraft theory of later writers, inasmuch as Redfield explicitly stated that he merely adopted the circular form of diagram for convenience sake. He deemed the circle good enough to show the fallacy of the straight-line theory of his fime, but was not able to conceive that a storm whirl was purely circular, and had not any doubt whatever that in different quadrants of the same storm might be experienced any wind from rotatory to rectilinear. I shall later on try to indicate that this is precisely the position to-day. Redfield happily conjectured that storms of south latitude rotated in an exactly opposite direction to those north of the equator. In the old sailing-ship days, when passages were reckoned by months, not by minutes, British army officers had much sea experience, and sailo*rs should be thankful that some of them observed and discussed the phenomena of ocean storms. Lieut. Col. Reid, R. E., confirmed Red- field's views in every particular ; Dr. Thom, of the Eighty-sixth Reg- iment, came to a like conclusion ; and Piddington, of Calcutta, put the finishing touches to the law of storms by the publication of his seaman-like work, which is bad to beat even now. Over fifty years ago it was shown that a single storm may split up into two or more, and conversely; that theVinds in a cyclone may be somewhat in- curved; that ships under the influence of one should choose the coming-up tack; and the storm tracks in the several seas were well indicated. Rules for storm sailing were made public which still obtain, with slight modifications. In 1849 Capt. Andrews, com- mander of a British royal mail steamship, impressed upon Col. Reid 154 CHICAGO METEOROLOGICAL CONGRESS. that a ship would sail away from the center by keeping the wind on the starboard quarter in the northern hemisphere and on the port quarter in the southern hemisphere ; provided, she would steer satis- factorily, and not broach to, a fact only knoAvn to those conversant with her sailing qualities. In 1872 Capt. Wales, harbor master at Mauritius, appears to have arrived independently at a similar rule, and this maneuver is now given in the text books. It is to Pidding- ton that we owe the term cyclone, as applied to revolving storms, which he derived from xux/*/? ; not as some assert as afl&rming a true circle, ])ut merely a closed curve, for in the Greek that word represents among other things the coil of a snake. There is a serious difficulty in the way of understanding exactly what Piddington and his con- temporaries meant by " incurving spirals " and " cycloidal " wind systems. Modern weather workers have introduced so many tantalizing ex- ceptions to the law of storms that a seaman aware of them would be bewildered. A ship at sea, in a cyclone, is not a fixed observatory. Hence, if this fact be ignored, it follows that arithmetical exercises relative to the angle of indraft will prove exasperatingly misleading. For practical purposes the circular theory is not more uncertain than any other. Blanford asserted that a cyclone center may be from 1 to 5 points before the port beam when running with the wind right aft in the Bay of Bengal ; F. Chambers concludes that the indraft varies from point to point around the whirl, increasing from zero to 35° as the observer recedes from the storm center ; Capt. Toynbee found that the indraft increases as the center is approached and is more marked in front of the storm; Capt. Whall is firmly convinced that with a good offing the wind blows directly for the storm center in the rear ; Ferrel proved mathematically that indraft varies not only with the distance from the center, but also with the latitude. Many other ex- amples might easily be given of conflicting estimates for finding the bearing of a storm center ; but enough has said to show that the problem is. so far, an indeterminate one in a great measure. Even the term center has not been satisfactorily defined. Granted that on synchronous charts the shape of a cyclonic disturbance is ellip- tical, with the major axis in the direction of travel, then is the so-called center a physical point or an area at one or other of the foci, or at the intersection of the axes? Occasionally a cyclone ex- tends right across the North Atlantic from America to Europe, and the question arises as to the bearing of ttie center of such a system at positions along the closed curve. Abercromby does not help me to form any definite conclusion when he says that the center of a cyclone is displaced toward one side of the oval and may move from one side to the other ! Yet the center is the first requisite in fore- casting a storm. Comment is superfluous from a nautical point of view. FORECASTING OF OCEAN STORMS. 165 The average tracks of storms have been approximately known for many years, but even a cursory glance at the 1892 North Atlantic Pilot Charts, published by the U. S. Hydrographic Office, shows that complicated and unexpected divergences from the usual routes occur at times. Similar instances are also noticeable in the erratic be- havior of storms over other oceans which would upset the best laid plans of experienced storm forecasters. The storm tracks of 1883, determined by the U. S. Signal Service, clearly indicate that the route most affected by Atlantic cyclones runs from a position south of Newfoundland to the north of Scotland. They drift eastward directly along the track of the Gulf Stream. Some, how^ever, which start well, either die out altogether or proceed due north in mid Atlantic. Others form closed curves and defy prediction. In March one apparently broke up into two distinct cyclones, one of which made the Bay of Biscay, and the other Valentia, on the west coast of Ireland. In April one which had reached N. 50°, W 25°, broke off to southeast, east, and northeast, eventually passing over Brest instead of Aberdeen, as a well-regulated cyclone would have done. Another in mid-ocean traveled east, north, southwest, south, and northeast. In November a cyclone moved eastward to the southward of the Azores for three days ; and another in December moving southeast in N. 50°, W. 37°, turned east and northeast to N. 50°, W. 32°, thence north, west, south, and southeast to N. 48°, W. 32°, where it apparently joined forces with another, which, three days later had followed it over Halifax, N. S. The rate of travel is also very variable. One of the above- mentioned storms moved over 20° of longitude during each of two consecutive days, but only 10° during the following forty-eight hours. Occasionally a rapidly-moving storm comes to a halt for a few days and then takes up the running again like a giant refreshed. Mr. R. H. Scott, and others, have referred to this fact at various times. Hence, there is little cause for surprise that the public - spirited attempt of the New York Herald to forecast storms bound across the North Atlantic was not so successful as it deserved to be. The average direction and rate of travel . for cyclones over a given ocean avail but little when tracks are not infrequently looped and the onward motion anything up to 70 miles an hour. The electric telegraph has done much to make easier the lot of a storm forecaster on shore, working in a snug room far distant from an approaching disturbance. Redfield, in 1847, seems to have sug- gested that this means of conveying storm intelligence between one place and another would be useful. The late Admiral Fitzroy may, ho\vever, be regarded as the pioneer of storm forecasting based upon actual observations transmitted by ware from remote stations to a central weather office, to be dealt with there and warnings issued to the seaports when necessary. His predictions were not always in 156 CHICAGO METEOROLOGICAL CONGRESS. agreement with the results, but it must not be forgotten that they were tentative, and even now certainty is denied. The idea of warning the coasts of Europe by telegram from ships anchored in the ocean to westward has frequently been mooted, and warnings from North America are, and have been in favor. The Anglo-American Telegraph Company sent messages without charge from Heart's Content, New- foundland, to England, but the place of observation was unsuital^le for the purpose and they were discontinued in 1871. James Gordon Bennett obtained better results in a similar way at his own expense, and France has not lost all faith in this method, as she still receives information from Washington of storms encountered by steamships bound westward. The U. S. Hydrographic Office is in possession of many records of the weather experienced by the Atlantic " grey- hounds," and an examination of these passages would perchance de- termine whether, and how often, a Campania or a Paris might give reliable storm warnings at either end of the journey, provided every effort were made to obtain such information immediately upon arrival at Queenstown, Southampton, and New York. Her Majesty's ship Brisk anchored for six weeks at the entrance to the English Channel as a stationary storm-warning vessel, but she proved a failure. It may be that those responsible did not have their hearts in the work ; for Capt. ^Vharton, R. N., Hydrographer to the British Admiralty, has said that anchoring at sea is not such a. physical impossibility as some shore folk believe. Morse thought that simple automatic regis- tering buoys might be dotted over the ocean, and Capt. W. Parker Snow has been bold enough to indicate a cordon of ships at intervals of 500 miles anchored between North America and Europe, in elec- trical communication with each other and with the land. If storm warning be worth doing at all it is worth doing well, and money should no more be begrudged in promoting the safety of life than it is to the invention of means for the more expeditious destruc- tion thereof. There should be educated observers, nautical men by preference, familiar with weather indications at their several stations, at Martinique, St. Thomas, Habana, Nantucket, Cape Sable, Cape Race, Valentia, Iceland, Bermuda, Madeira, and Flores, all in com- munication by submarine cable with the United States and Europe. Science is catholic, and each maritime nation might be required to support this international system of storm warning. If this be im- possible, then I would suggest that synchronous charts for the whole globe be undertaken, on which would be carefully laid down the requisite information, but free from an undue striving after artistic elfect which adds nothing to their utility though much to their cost. They should be international in every way, and, after the weather workers of each nation have drawn isobars, etc., on precisely the same data, a critical comparison should be carried out by a truly repre- FORECASTING OF OCEAN STORMS. 157 eentative conference ; the best sets chosen, not as specimens of geo- metrical drawing, but as representations of fact, and deductions for storm warnings made therefrom. An accurate acquaintance svith the conditions that prevail twenty-four hours, or more, previous to the passage of an awful cyclone over an exposed roadstead or coast line may be of infinitely greater value to navigators and shore forecasters than the most detailed climatological treatise based upon insufficient data. Similarly, points of vantage in other oceans should be coupled up with the central forecasting establishments in the vicinity and provided with competent observers. A storm warning to be of use to the shipping Community, whom it principally concerns, must fulfill several conditions. It must be of such a nature as to be easily understood by navigators in ships of all nations; it must really be a notification that a gale will blow from a specified direction and proceed along a clearly-defined track, and not merely a record of present weather, or a false alarm ; and it should be sufficiently reliable and explanatory to assist seafarers in arriving at a proper appreciation of weather to seaward. In fact, off Ushant and Finisterre, for example, a ship might be informed not only as to the storm expected at either place, but also farther north or south, as necessary. The storm signals should be clear enough to do away with any necessity for reference to telegrams on view in the vicinity. It is not sufficient that a navigator be only informed whether the north- ern or southern portion of a cyclone is expected to pass over the sta- tion displaying the signals. The question as to the best form in which warnings should be made is a strictly nautical one, and might be decided by a committee of representative officers of war ships and merchantmen. The international code of signals might be utilized, notwithstanding the disadvantage of flags in a calm, or blown out directly to or from an observer. They are, however, probably prefer- able to shapes, such as cones or rectangles ; and semaphores find many admirers. Light-ships in connection with the shore by submarine cable, signal stations, life-saving stations, and lighthouses should all be pressed into the service of warning for ocean storms both by day and by night. I have, doubtless, tried your patience considerably, yet the magni- tude and importance of forecasting ocean storms would demand for a due appreciation thereof a far more extended scope. If this paper will but awaken navigators of the world's war ships and mercantile marine to the desirability of making their voices heard more fre- quently with no uncertain sound on points connected with their v.-ell being, I shall not have encroached upon your time and attention in vain. I can not do better than close this necessarily imperfect sketch by quoting the words of Capt. D. Wilson Barker, R. N. R., who has devoted himself to marine weather work, especially in the direction 168 CHICAGO METEOROLOGICAL CONGRESS. of cloud observations : " Probably no prognostic is so valuable to a sailor as that afforded by clouds, particularly those of the cirrus formation ; and while their value as prognostics has been recognized from the most ancient times, it is only rarely cultivated, and yet I have no hesitation in saying that there is no weather warning for an isolated observer that can in any way compare with them." My old master, Capt. Henry Toynbee, whose name is a household word among officers of the British mercantile marine, Ensign Everett Hayden, U. S. Navy, and other observers have also mentioned the same fact for the benefit of navigators. Capt. A. G. Froud, R. N. R., has just sent me an interesting letter of Vice -Consul Ramsden, at Santiago de Cuba, explaining the method of Padre Vines at Habana, a well-known authority on West Indian hurricanes, and stating that in Cuba cirrus gives the first indication of the position of a hurricane, and that the clouds "enable one to say whether the low barometer is due to a cir- cular storm or not." Nevertheless, it must not be forgotten that cloud observation requires careful training, and schools for teaching the elements of weather work are conspicuous by their absence on this side of the North Atlantic. Manj^ leagues aAvay, I can not but await your reception of my paper with some trepidation, mindful, however, of the fact that the man of science " loveth truth more than his theory," and that the subject is of itself far more important than the manner of explanation. 2.— THE CREATION OF METEOROLOGICAL OBSERVATORIES ON ISLANDS CONNECTED BY CABLE WITH A CONTINENT. Al-BKKT, PlUNCE OF MoNACMI. During the long periods of time spent on the North Atlantic, on board of my schooner, VHirondclle. devoted to investigations touching oceanography, and after a careful study of the important labors of American oceanographers and meteorologists, I remain convinced of the utility attached to the creation, upon the scattered islands be- tween Europe and America, of posts of observation daily reporting the state of the atmosphere to a central bureau, as soon as they shall be in direct communication by means of telegraphic cables with either of these two continents. By means of the meteorological observatories now on the continent we are permitted to forecast, in a general manner, the approach of certain tempests. But what results would be obtained if those per- turbations were studied upon the very spot where formed, inasmuch as the surface of the waters gives origin to most of the phenomena which break the equilibrium of the atmosphere. Meteorological observatories on the ocean, allowing us to trace in a OBSERVATORIES ON ISLANDS. 169 regular manner the mutation of minima and maxima, the variations of the temperature and winds, would afford the means of distinguish- ing the principal whirlwinds and the secondary depressions, and enable us to trace the zone of influence of each of them. The following is my scheme comprehending, in its broad lines, the organization of North Atlantic observatories : The expenditures for the creation and keeping up of these estab- lishments should be supported in common by the governments of Europe and that of the United States. Individual donations, besides, should be accepted. The points which I consider as most important for the meteoro- logical observatories of the North Atlantic are the Cape Verde Islands, the Azores, and the Bermudas. The Cape Verde Islands are situated iif a region in which, accord- ing to the Pilot Chart, many storms originate, thence going to ravage the West Indies and the coasts of the United States. Those islands are, at the same time, situated along the outer border of the circular movement of the North Atlantic waters, of which my researches upon the currents have shown the existence and the course. The Azores are situated near the center of this circulation, on which account they deserve special attention, forasmuch as an inter- esting coalescence occurs between that center and the center of the area of high oceanic pressures when the maximum is bearing west- wardly to coincide with that of the Bermudas. The Bermudas are situated near the western border of the circula- tion of the waters, not far from the Gulf of Mexico, which plays an important part in oceanic meteorology ; moreover, they are under the influence of the Gulf Stream. With these three points at our command an efficient supervision could be exercised over the North Atlantic. So much the more as at the Cape Verde Islands and at the Azores the height of the moun- tains (2,974 m. and 2,321 m.) would permit complete observations to be made by means of neighboring posts for the observation of the upper regions of the atmosphere. But such supplementary observa- tions would, for the present, be of secondary importance in the pre- vision of weather, inasmuch as the inquiry thus far made into the materials collected at the observatory of Ben Nevis shows that ob- servation of the inferior layers is the most advantageous to such a prevision. It will oftentimes happen that the observatories, if placed at St. Vincent for the Cape Verde Islands, and at San Miguel for the Azores, and on the principal island for the Bermudas, will be in a position, by ships putting into port, to add to the local observations, observa- tions made at sea one or two days previously. Thus, we should pos- 160 CHICAGO METEOROLOGICAL CONGRESS. Bess, at a given time, a small network of observations covering a sur^ face of several degrees. For a long time I have been meditating upon the programme of which the broad lines are indicated above. But ere entering into its execution I must wait until the center of observations, the most interesting for Europe, the group of Azores, shall be connected with the continent by a cable. Judging from the actual agitation about that undertaking, it is allowed to hope that the laying of the cable is a mere question of time ; the moment seems, therefore, opportune to prepare the desired scheme. I thought it useful to bring before the intellectual assembly which meets this day in America (scientific representatives of the whole world bestowing a new impetus upon the activity of human intellect) this question of oceanic observatories which, by the manifold services they should return, would soon be multiplied on the surface of the globe. This question was brought by me last year before the Academy of Sciences of Paris, and before the British Association at its session in Edinburgh ; on both occasions the meteorologists and oceanographers of Europe agreed completely upon the desirability of establishing the aforesaid observatories. I am convinced that the American savants, always practical and stout hearted concerning enterprises of great scope, will likewise join their efforts to mine in hastening the execu- tion of my plans. Is North America not interested in the same de- gree as Europe in the possession of advanced information of atmos- pheric perturbations originating upon the ocean, and which exercise so considerable an influence upon the meteorology of both continents? Unquestionably it is a great progress wanting realization for the ad- vance of modern civilization. Again, what will be, for powerful nations, the pecuniary sacrifices involved in the aforesaid scheme compared to the ruinous prepara- tions for war \yhich seem rather contemplated to thrust back the human race into barbarism. At least when these edifices shall arise in the midst of the seas, far from the turmoil of politics and war, will it not be a legitimate com- pensation to wise men, thoughtful of labor, progress, and peace, and justly alarmed in viewing people armed for destruction? Most cer- tainly so, and the good parole of science announcing new discoveries shall attenuate the voice of cannons. I come with so much the more joy to lay before you my projects, as I am certain to find with you a similar thought, for you are the descendants of the sturdj'- men who fought of yore for life and knowl- edge ; you are already the men of the future, contemptuous of the vain glory of conquests. THE MARINE NEPHOSCOPE. 161 3.— THE MARINE NEPHOSOOPE AND ITS USEFULNESS TO THE NAVIGATOR. Prof. Cleveland Abbe. The object of the marine nephoscope is to enable the navigator to observe the motions of the clouds, either upper or lower, as easily as he observes the winds. He may not only deduce therefrom the loca- tion of a storm center at any moment, which knowledge he needs for his own safety, but may also put on record the data by means of which other students can determine the actual heights and motions of the clouds which will be needed in the further advance that me- teorology is sure to make. I would not assert that we have as yet all the data needed by which the navigator can quickly determine the distance and direction of the storm center at any moment ; but we have here the long-needed in- strument and I wiW indicate the method of using it, and the further general process of reasoning, in hopes that this may attract the at- tention of the navigator to the practical value of the marine nepho- scope. The instrument and its use are so simple, and the interest that attaches to the subject is so great, that it is important that navigators in both naval and merchant marine should learn its use and record the motions of the clouds as regularly as they do other meteorological items. In the gradual development of our knowledge of storms we have historically passed through many stages, e.g., (1) the study of the winds; (2) the study of individual, local, or isolated barometric de- pressions, namely, the simple rising and falling of an individual barometer; (3) the study of the differences or departures of observed barometers from the normal or average readings of the same instru- ments at the same altitude above sea level ; (4) the study of the rel- ative pressures at many stations all reduced to sea level, and of late years also reduced to standard gravity ; ( 5 ) the study of the de- partures of the individual readings, reduced to sea level, from the average pressure proper to the small circle of latitude round the whole globe. Incited by the investigations of Guldberg and Mohn, of Ferrel and other leaders, meteorologists have of late years paid special atten- tion to the angle between the wind and the isobar, but isobars can not be drawn or used by the mariner at sea, neither should the isobar be considered to the exclusion of the effects of temperature and mois- ture in altering the density of the air ; therefore, both for practical and theoretical reasons, the navigator must confine his attention to the angle between the direction toward which the wind is moving at the observer's station and the direction in which the storm center lies with reference to his station. By storm center we shall in this paper mean the central point 11 162 CHICAGO METEOROLOGICAL CONGRESS. about which rotates a system of whirling winds. We must distin- guish between this center of winds and the barometric storm center,! which latter is defined as the center of the smallest isobaric circle or] ellipse. This latter is the storm center of modern dynamic meteor- ology ; the former is the storm center of the mariner and of the older] cyclonologists. These centers are often identical, but not necessarily always so. Mechanical principles have of late years required us! to study the relations of the winds to isobars and isabnormals, but having done this we must now return to the older problem and for the use of the mariner, must apply our increased knowledge to the study of the simple geometrical problem that he has to do with, namely, the relation between the movement of the wind and the bear- ing and distance of the storm center. As the direction of the wind is so minutely observed by navigators! who understand how to determine its true direction, notwithstanding the motion of the vessel on which they are sailing* it should be easily] possible by the accumulation of weather maps to determine the di- rection and incurvature of the wind on all sides of the storm centers] at sea. Therefore, up to the present time the navigator has relied | upon the wind and its changes to indicate to him the location and movement of the storm center that he wishes to avoid. The progress of our knowledge of the motions of the upper and lower currents of air in the neighborhood of a well-defined hurricane center has made it apparent that we may improve upon the old rule of the earlier cyclonologists who assumed that the wind blew in a circle around a hurricane center and who, therefore, stated that if in the northern hemisphere the navigator stand with his back to the wind he will have the center on his left. hand. This rule was always recognized as rather crude, yet for a long time nothing better was offered for the use of mariners, notwithstanding the fact that the charts of Redfield, Espy, Loomis, Lloyd, and Lever- rier all showed that the rule is not a law of nature. The fact that the winds are inclined inward, as compared with the path required with the truly circular theory, was stated very emphatically by Red- field in 1846, and he adds that in his charts of storms the engraver had sometimes drawn the winds in accordance with the old theory, contrary to Redfield's better judgment. He states that the average inclination of the wind to the circular tangent rarely exceeds two points of the compass, and is never so much as was often claimed by Espy ; but it seems to me that the fact should not be lost sight of that the land storms studied by Espy and the ocean hurricanes studied by Redfield are two modes of motion in the atmosphere that are often essentially different from each other. The rules for locating the center of a hurricane and for determining the direction of its motion, hitherto used by navigators, have been THE MARINE NEPHOSCOPE. 163 based largely upon the study of the direction of the wind, but this is subject to considerable local irregularities if the mariner is in the neighborhood of any land ; moreover, the inclination of the wind to the radius from the storm center varies largely with the latitude and the position with regard to that center. Numerous studies, especially those of Broun, Ley, Hildebrandsson, Ekholm, and Clayton, have shown that the movement of the wind is subject to considerable irregu- larity and if the navigator can avail himself of the direction of mo- tion of the clouds he may locate the storm center with much greater accuracy. The most extensive series of observations of upper and lower clouds is that published by Broun in the annual volumes of his observations at Makerstoun, Scotland, for 1843-46, which form a part of the Transactions of the Royal Society of Edinburg. As the result of about 3,000 observations Broun found that the lower cumulus scud is inclined outward to the winds by 14.5° ; the next layer above, or cirro-stratus, inclines outward 22.8° ; the highest layer of clouds, or true cirri, is inclined outward 29.6°. These observations were for many years overlooked until, in 1871-72, both Clement Ley and my- self, by the study of English and American observations, respectively, independently announced the general rule, almost in the words that Broun had used twenty-five years before, that as we ascend in the at- mosphere the angle by which the movement of a given layer differs from the movement of the lowest wind deviates more and more to the right. As a result of the work that has hitherto been done on this subject I think we may for the present adopt the general rule that between the winds that blow spirally inward and the upper clouds that .blow spirally outward there is an intermediate layer of the so-called lower clouds whose motion is very nearly along a circular arc and that the mariner may more safely locate his storm center as being in a line perpendicular to the motion of the lower clouds rather than to rely entirely upon the surface winds. If he observe the angle be- tween the movements of the wind and the lower clouds and again between the lower and the upper clouds, he has a further means of determining even the distance of the storm, although the definite rules for so doing need not now be given. Assuming, therefore, that the storm center bears at right angles to the direction of movement of lower clouds and is on one's right hand when he faces the direction from which these clouds are coming, it remains only to show how to use the nephoscope in order to obtain the direction of cloud movement. The accompanying diagrams (Plate vi) present both a horizontal projection and a vertical section of Ritchie's Patent Liquid Compass, as used on American naval vessels, as also a similar projection and vertical section of my marine nephoscope. The compass proper may be described as a heavy bowl mounted on gimbals and so adjusted as 164 CHICAGO METEOROLOGICAL CONGRESS. to its axis of gyration that its time of vibration is rather long, namely, about one-half second. The lower half of the bowl is ballasted, and its upper half constitutes a closed receptacle full of liquid, bounded by the circular plate of glass. Within the liquid floats the compass card and needles ; the compass card shows not only the thirty-two quarter points, but also every degree of azimuth. The observer look- ing down upon the plate-glass top sees the compass card, which is just below it, and also the lubber line, FA, as marked on the brass rim. As the vessel rolls or pitches the compass card preserves its horizontal position fairly well up to a limiting roll of about thirty degrees. In the standard compass of the U. S. Navy the upper edge or flange of the compass bowl, EE, is neatly turned to an exact circle concentric with the pivot and about 9^ inches in diameter. This is for the purpose of setting thereon, at any moment, the alidade and sights for observing the sun and stars, or otherwise determining the true azimuth and the magnetic variations and deviations at any time. Ordinarily, this apparatus is not in place on the compass, and, there- fore, without disturbing the regular work of the ship, we may set the nephoscope on the compass in place of the astronomical apparatus. The thin circular vertical flange of the nephoscope is shown in sec- tion RR, and it fits snugly over EE. The nephoscope consists essen- tially of this circular flange RR, whose upper horizontal surface is the ring on which appear the graduations for every five degrees, num- bered from around to 360 in the direction in which azimuths are ordinarily measured. In order to revolve this ring horizontally, two small handles, PQ, are provided. Within the graduated ring the cir- cular area is covered by a single plate of thin mirror glass of excel- lent quality, silvered on the lower side. But as it is necessary to look through at the compass card below, the silvering has been removed in a broad circular band ; there is also a smaller circle of half its size, as shown by the heavy black line ; the outer and inner bounda- ries of these circles are made quite exactly smooth and concentric with the center of the small black spot, C, which is immediately over the compass pivot. When this silvered mirror is in place upon the compass it repre- sents a horizontal plane, and it preserves its horizontality with remarkable persistence, notwithstanding the ordinary rolling and pitching of the vessel. In the absence of any convenient method of exact measurement, I have been able only to estimate that, in the case of the compass used by me on board of the U. S. S. Pensacola, the inclination of the mirror plane to the horizon was rarely more than two degrees, and to this extent, therefore, an uncertainty is introduced into all our measurements ; but, as the inclination is per- petually oscillating from positive to negative, we have, therefore, only to take the average of a few observations in order to obtain results EPHOSCOPE, Abbe. Horizo ntal Projection of Co mpass. MARINE NEPHOSCOPE, Section on line ab. Horizontal Projection of Nephoscope. Horiznnl.i! Pmiectiun of Compass i THE MARINE NEPHOSCOPE. 165 that are appreciably free from this source of error. The observer must, however, be careful to keep the compass in such adjustment that the bowl shall not have any constant error in this respect; of course this same adjustment is also ifecessary in connection with the observation of the the sun or stars. In so far as the mirror is horizontal, therefore, a line drawn per- pendicular to it at its center is an approximate realization of a standard vertical line on shipboard, and our object now is to deter- mine the motion of the clouds with reference to the zenith and hori- zon of this mirror. When the observer looks into the mirror he sees reflected therein not only the masts, and rigging, and pennants, but the clouds, and even the sun, moon, and stars. The apparatus is a simple, crude, but convenient altitude and azimuth instrument, and with it we can perform all the operations of determining altitudes, latitude, time, longitude, and azimuth with a very surprising degree of accuracy. I have many times had occasion to set up this nepho- scope on shore, and, besides observing the clouds, have determined the altitude and azimuth of the sun ; the probable error of a single measured altitude of the sui»or moon is about one-quarter of a de- gree, and could be made still smaller by appropriate changes in the construction. In order to measure the apparent altitude and azi- muth of clouds by a method suifficiently expeditious, simple, and accurate for use at sea I devised the hollow tube SS, and the sliding rod which fits within it with friction, and which carries at its end the small knob, K. The tube has a motion in a vertical plane about the hinge, S, and when elevated to any altitude is held there by the friction of this joint. The vertical plane through the tube, the knob, the central spot, C, and the hinge, S, corresponds with the zero of the graduation of the horizontal rim. The numbering of the degrees is from to 360. The knob and the central spot, C, have the same diameter so that in whatever position the knob may be placed (by elevating the tube and sliding the rod in or out) the observer can bring his eye to such a position that he will see the knob reflected in the mirror and exactly covering the spot. Let us suppose that the observer has done this and that he also sees reflected, at C, a small bit of cloud or a point in a large cloud, then if he continues to hold his eye in such a position that K always falls upon C the cloud will seem to move away from the center of the mirror. But he may, if he choose, so move his eye that the image of the knob shall continually cover the selected point of cloud, and if he does this, then both cloud and knob will appear to move together away from the center of the mirror. This latter is the method of observation that is always to be recommended, and if one could keep the cloud and knob together until tteir reflections simultaneously reach the edge of the graduated rim, he could then read on the rim an angle that represents the 166 CHICAGO METEOROLOGICAL CONGRESS. azimuthal direction of their motion relative to the zero of that circle. The position of this zero with reference to the lubber line, FA, of the vessel is given by taking from the same circle the reading correspond- ing to the forward end of the line, F; the relation of F to the magnetic meridian is given by taking from the compass card, as seen through the unsilvered glass, the angle corresponding to the same forward end of the line, AF; the relation of the magnetic to the true meridian is known from the tables of deviations and variations. These four angular readings, when added together, give the true azimuth of the apparent motion of the cloud. Inasmuch as we do not often care to wait as long as is necessary for the image of the cloud and knob to move from the center to the edge of the mirror, and especially since it continually happens that the cloud disappears or becomes unrecognizable in the midst of an observation, it is necessary to provide for that class of observations which really occurs most frequently, namely, where the cloud is fol- lowed only out to the first small circle whose radius in the present apparatus is exactly one inch ; I have, therefore, provided a black copper wire or silk thread that stretches entirely across the circular mirror and is attached to a rather heavy wire forming a circle adjacent to the inner edge of the rim. As this circle with its wire must be easily turned in azimuth, there are provided two small handles, h and h ; by taking hold of these the observer easily brings the thread into such a position that both cloud and knob traverse it together as they move across the mirror, and no matter how short their path may be, the azimuth of their motion is easily read at the end of the thread. We thus provide all that is necessary in order to obtain either the true or the magnetic bearing of the movement of the cloud. It is easy to see how one may utilize the same thread to determine the azi- muthal trend of the trail of smoke which a steamer leaves in its wake, or the trend of the streamers and pennants seen reflected in the mirror, and, as all these depend upon the combined motion of the wind and vessel, they have been subjects of regular observation by myself on the U. S. S. Pensacola. Moreover, when one wishes to ob- serve the trend of the troughs and ridges of waves, or of the foam that flecks the water with white streaks during high winds, he has here an apparatus more convenient and accurate than the estimates of any but the most skilful navigators, as I can testify from consid- erable personal experience. Not only the motions of the clouds, but general trend, or the vanishing points of special formations in the cirrus clouds, the boundaries of cloud rolls, the location of the zodiacal light, and the dimensions of halos and rainbows, are easily determined. By determining the apparent angular altitude and the apparent velocity per second of the cloud under observation, when a vessel is THE BAROMETER AT SEA. 167 going at different speeds and in different directions, we may compute the actual velocity and height of the cloud. But I will not here enter upon a complete account of the many problems that can be solved with the help of this simple apparatus ; they are mostly questions that interest the meteorologist rather than the navigator. The latter needs the nephoscope mostly in order to determine the true direction of motion of the clouds, and for this purpose, if his vessel is a steamer, he first observes the apparent direction of motion as seen in the nephoscope when going ahead at his ordinary speed; he then slows up a little for five minutes and takes another observation and, if he can, slows up for another five minutes and after getting a third observation resumes his full speed and takes a final observation. The difference between the results obtained at high speed and low speed enables him to easily find what the true direction of the cloud motion is or as it would 'be observed if the vessel were stationary. If the navigator is on a sailing vessel it is easier for him to observe on two different tacks and the comparisons of the results thus obtained will give him the true motion of the clouds. When the wind has a strength above force 6 on the Beaufort scale, the movements of the lower clouds are apt to be so much more rapid than those of any sailing vessel that the cloud movement is given with sufficient ap- proximation by single observations without the necessity of combining those made on different tacks. Convenient numerical tables will be published in a " Manual of the Nephoscope." 4.— THE BAROMETER AT SEA. T. S. O'Leary. Ever since Torricelli, that brilliant pupil of Gallileo, made his famous experiments in 1643, the barometer has been both a familiar and valuable instrument to all civilized nations. It is now absolutely necessary in conducting all scientific experiments where the pressure of the atmosphere is a factor. But so much has been written on its construction, care, uses, and reliability, it would be a waste of time to attempt to cover ground that has already been so carefully gone over. As the subject is a large one it is much beyond the scope of this paper to treat it, though briefly, in all its phases in the time allowed. I shall confine myself, therefore, to a few general remarks. Although the U. S. Hydrographic Office has been collecting ocean data ever since the time of INIaury, it has been within the past few years that special efforts have been made to systematize the collection of these data and use of the same. A great step forward was made when the meteorological log journal, which required observations to be made at twelve different times during every twenty-four hours, 168 CHICAGO METEOROLOGICAL CONGRESS. was superseded by the meteorological log book, which requires but one regular observation to be made daily. The hour fixed is noon, Greenwich mean time, so that no matter in what part of the ocean the observations are being made the observers are acting simultane- ously. This simplified log was found to be much more desirable than the journal, as observers were induced to continue the w^ork, who, after filling one journal, were apt to decline keeping another on ac- count of the labor involved. The result has been that the number of observers has increased nearly eight fold, so that the oceans are now- dotted with many interested workers. Another valuable feature is the indenture of the leaves of the new log book, which enables the observers to remove the pages as fast as they are filled up and forward them to the Hydrographic Office, there to be utilized in current work. The master of a vessel, or the observer, wants to see the results of his observations w^hile the facts are still fresh in his memory and while he is yet interested in what has re- cently taken place. The Pilot Chart of the North Atlantic attempts to satisfy this want by placing before the mariner in a graphic form such matters as are deemed of interest or importance to him. For his time and trouble the observer wants a ready return if possible. The accumulation of several years' data in the home meteorological offices, there to he compiled at leisure, then to appear in a volume too bulky for reading and too scientific for the ordinary navigator, with too much attention paid to minor details, is a danger which should be carefully guarded against. The past has shown that the above cause has driven from the field many good observers who were once interested, and kept out of the field many more whose co-operation would have been of the greatest value. The loss of their services is a direct loss to the science of marine meteorology, but, let us hope, it is not too late to again stim- ulate them to further efforts. It goes without saying that mercurial barometers are the best and most reliable, but, unfortunately, a good mercurial instrument is an expensive one. For this reason many sea-going vessels are supplied with aneroids only. Some are supplied with both, but generally the mercurial, the reliable one, is placed in the captain's cabin, where he alone has access to it. On other vessels it is often placed too high, where the light is not good, or more with regard to its safety than its accessibility, so that on a dark night, during heavy weather, the observer experiences no little difficulty in getting even an approxi- mate reading. Generally speaking, the placing of many barometers, especially in merchant ships, is in the interest of the vessel and its owners and not in the interest of science. We must accept the situa- tion as we find it, and deduce from the data furnished the best results we can. THE BAROMETER AT SEA. 169 First of , all, the most important thing in considering a set of barom- eter readings is to determine the reliability of the instrument and observer. To do this frequent comparisons with a standard barometer are necessary of readings recorded hy the observer himself. A simple plan for obtaining these comparisons has been in use by the U. S. hydrographic offices for the past three years, and the results obtained have been most satisfactory. The credit of the plan is due to the force employed in the Meteorological Division of the Hydro- graphic Office at Washington, which plan was arrived at after the mistakes and difficulties of former methods in use had been clearly demonstrated. I can not do better than give an account of the plan now in use. Although simple in the extreme, it answers all practical purposes. On the arrival of a vessel in port the meteorological reports are forwarded immediately to the nearest branch hj^drographic office. Accompanying the acknowledgement of the receipt of these reports are two or more franked postal barometer cards, on the back of which are brief instructions showing how the columns should be filled. When in ports of the United States or Canada, observers are requested to record the readings of the barometer used for observations at sea at 8 a. m. or 8 p. m., seventy-fifth meridian time, as at those hours the U. S. Weather Bureau observers record their observations. If the vessels are in those ports where branch hydrographic offices are located, readings at other times will answer, as a record is kept of the hourly readings of the standard in each office. When the cards have been properly filled out they are mailed by the observer to the branch hydrographic office, where each reading is compared with that of the standard instrument for the corresponding time. A cop}'^ of these comparisons is immediately furnished the observer. The original cards are forwarded to the Hydrographic Office at Washington, where the comparisons are examined and copied, after which they are re- turned to the branch offices whence they came, there to be filed away, so that any master or observer can readily find out how his barometer has been acting from month to month or from year to year. In making these comparisons it has been found best to take the absolute difference between the reading of an aneroid and the corrected read- ing of the standard as the total correction to be applied to all the readings of the aneroid for that pressure. With mercurial barome- ters the reading is first corrected for temperature; the difference, then, between that result and the corrected reading of the standard is the correction to be applied to the reading of the mercurial. It is evident that these total corrections are but the algebraic sum of the instrumental error, correction for altitude, and personal error of the observer. This last error is of no little consequence, for if the ob- server is not faithful in recording the observations at the proper time, 170 CHICAGO METEOROLOGICAL CONGRESS. his work is no more reliable than that of a faithful observer with an inferior instrument. It might be contended that the corrections obtained from compar- isons made in port when the vessel is light would not answer when she was at sea deep laden. Supposing this difference in heights of the barometer to be 15 or 20 feet the difference of correction would be only one or two hundredths, an unnecessary refinement when it is remembered that in the height of the storm, or when the mercury is "pumping" considerably, an approximate reading is all that can be obtained. Another method of obtaining comparisons, which has proved quite satisfactory, is by making use of the isobars on the U. S. Weather Maps and the readings at the stations along the coast. As the morn- ing readings are taken at 8 o'clock, seventy-fifth meridian time (or 1 p. m., Greenwich mean time), there is only an hour's difference between the shore readings and the readings at sea. Under normal conditions this is not of much consequence, especially when the pres- sure changes only a few hundredths in as many hours. Use is made, also, of the 2 p. m. readings of the British Daily Weather Report. It will be seen that " checks " obtained from the readings of a vessel's barometer while in the vicinity of Key West, Jupiter, Hatteras, Block Island, or Nantucket on this side, and again near the outer stations, such as Moville, Valentia, Bishop's Rock, or Dungeness on the other, would determine pretty well whether or not the readings for the voy- age should be rejected. These comparisons are often the only ones obtainable, as the many duties of the officers while in port leaves them little or no time for filling out blanks. Hence, the importance of these shore readings when vessels are adjacent to the stations. It might be mentioned in this connection that the readings recorded on the vessels at the time are obtained under the same conditions, most likely, as those recorded for the previous or subsequent part of the voyage, which fact lends value to the comparisons. This second method of obtaining comparisons is confined at present to vessels approaching or leaving the east coast of the United States or the coasts of Europe. It is to be hoped, however, that in the near future reliable readings from standard instruments for noon, Green- wich time, will be promptly furnished from the Azores, Canaries, Cape Verde, and West Indies, so that corrections for vessels' barom- eters can be obtained in much the same manner that a navigator determines his chronometer error when in the vicinity of a place, the latitude and longitude of which have been accurately determined. Without a good idea of the approximate correction to be applied to the readings furnished, the investigator will find it quite difficult to harmonize ocean barometric data. THE BAROMETER AT SEA. 171 It is to be regretted that the morning observations for the U. S Weather Service are not made an hour earlier, and the 2 p. m. obser- vations of the British Weather Service two hours earlier. If such were the case, the observers, both on land and at sea, would be work- ing in conjunction with each other, and the simultaneous observa- tions would extend over Europe, the United States, and all the oceans. In the northern hemisphere particularly could the meteorological conditions be studied to better advantage, with observations taken at the same time over an area extending from Russia on the east to the east coast of Asia on the west, or over two hundred and fifty degrees of longitude. The importance of the change suggested and the ben- efit resulting therefrom are worthy of serious consideration. The records of the Hydrographic Office for the past three years show that on 5,425 voyages or parts of voyages made by 1,600 vessels the readings of the mercurial barometers were deemed reliable in 4,321 cases, while in the remaining 1,104 cases they were discarded or considered doubtful. With the aneroids, out of a total of 8,898 voy- ages or parts of voyages, in 4,160 cases the readings were considered re- liable, and in 4,738 cases unreliable. In other words, 80 per cent of the mercurial readings could be fairly depended upon and only 46 per cent of the aneroids. These represent about 250,000 barometer readings for the North Atlantic, of which about 130,000 were plotted and 120,000 discarded. The large per cent of unreliable readings can be attributed to many causes, some of which are inferior instruments, carelessness in reading, wrong time for observing, and wrong position given for time of observation. Many of these mistakes have been corrected as the observers have grown more familiar with the work. This is evidenced by the decided improvement to be noticed in the consistency of the readings plotted in the successive volumes of the daily synoptic maps of the North Atlantic. It is fair to presume that in a short time 80 or 85 per cent of all the barometric readings received will be plotted instead of 63 per cent, as previously shown. The large difference in per cent between the reliable mercurial ba- rometers and reliable aneroids will not escape notice, and while the superiority of the former instruments is undoubtedly established I would hesitate long before casting aside the readings of all aneroids simply because they were aneroids. In many instances, especially in those parts of the ocean the least frequented, readings from aneroids are the only ones obtainable. With a fair correction these readings assist to establish the origin of a " low," perhaps, or prolong a storm track beyond the well-defined paths of commerce. Although mer- curial readings are to be preferred the prejudice against aneroids should not be too strong. While some are bad all the time, not all are bad all the time. The lowest reading plotted on any of the daily synoptic maps is that of an aneroid, which was considered tolerably 172 CHICAGO METEOROLOGICAL CONGRESS. reliable. At 10 a. m., Greenwich mean time, February 1, 1892, the British steamship Bellini, in N. 59° 38', W. 7° 02', had a barometer (aneroid) reading of 27.47 inches. Appljnng the correction, -j-0-15, for this instrument, the corrected reading would be 27.62 inches. As the reading recorded by the observer of the British Weather Service at Sumburgh Head at 6 p. m. of that day was 28.02 inches, with steep gradients to the westward, and as the storm center passed to the north- west of the Shetland Islands, it is not unlikely that the corrected reading of the BelUni\s barometer, 180 miles west of Sumburgh, and near the storm center, was not far from a correct pressure. The cor- rection applied in this instance, -j-0.15, was obtained from comparisons on this, the preceding, and the subsequent voyage. The next lowest reading plotted is that of the Dutch steamship Wei'kendam. in the cyclone of December 22-23, 1892. At 2 a. m., Greenwich mean time, December 23, in N. 49° 41', W. 30° 41', the corrected reading of this instrument (mercurial) was 704 mm., or 27.72 inches. The highest reading so far plotted is 790 mm., or 31.10 inches, the corrected reading of the German steamship Fulda\s mercurial barom- eter, at noon, Greenwich mean time, January 14, 1891, in N. 49° 57', W. 14° 50'. These readings would indicate that at sea the greatest range of the barometric column occurs in the high latitudes during the winter months, the same as on land, and is about 84 mm., or 3.5 inches. The importance of frequent comparisons can not be overestimated. To illustrate, the mecurial barometer of a well-known trans-Atlantic liner after being quite regular for two years suddenly changed so that a correction of -}-0.78 of aa inch was necessary. The observer being notified of the fact began using an aneroid. The latter instru- ment was found to be 0.50 of an inch too high. Here, then, were two barometers on the same vessel with a difference of 1.38 inch in their readings. This is, perhaps, an exceptional c*ase, but it shows that each and every barometer should be carefully " checked " before the readings are plotted as final. Out of the 1,600 vessels previously mentioned the author has taken 70 that had good barometer records. The records show that of these barometers 60 were mercurial and 10 aneroid, and that the average variation of the 70 barometers over a period of twenty-five months was only 0.04 of an inch. Only those records were taken where the variation in the correction applied was less than 0.10 of an inch, and where the barometer had been in use more than a year. The superiority of the mercurial barometers is here again shown by a ratio of 6 to 1. Of the 60 mercurial barom- eters it was necessary to apply a plus correction with 50 and a minus correction with the remaining 10, which fact might indicate that even with the good observers the tendency is in reading mercurial barometers to move the vernier too far down and thus read too low. THE BAROMETER AT SEA. 173 An intelligent interpretation of the prevailing conditions as indi- cated by the barometer, direction and force of wind, state of sea, and atmosphere, with a view to not only the present, but the future action of his vessel, should be the object of every mariner. At the approach of a cyclone, or even when the storm is on, the action of the barom- eter together with the shifts of wind will determine the all important point of which tack to lay the vessel on. This done, and the storm passed, the next thing is to take advantage of the future shifts by so laying the course, when first able to proceed, that the different shifts will be provided for beforehand and the vesssl allowed to continue on her way without the probability of being headed off. Good judg- ment in this direction, based upon the knowledge we already have of the general laws of atmospheric movements, will often serve to shorten the passage and bring the vessel into port without much working. It is not only in bad weather, but in good weather also that the master should be on the alert. The approach of a " high," with successive shifts of wind due to that circulation, should be as well understood and maneuvered for as the approach and shifts of a " low," and for the same reasons as given above. This important subject is worthy of the fullest investigation and should be thoroughly mastered by every navigator. In conclusion, I would beg to submit for your consideration the following suggestions : That the members of this Congress impress upon their respective governments the desirability and importance of a least one set of simultaneous observations taken daily ; that the hour be noon, Green- wich time, for reasons previously mentioned ; that all barometer read- ings be "checked " by frequent comparisons before being used; that a uniform and simple system of recording observations by mariners be adopted ; that the recording of observations be encouraged among shipmasters and officers, and also the study of ocean meteorology by putting before them from time to time, and in as graphic a manner as possible, the explanation of the general laws of atmospheric move- ments and such other matters as would be beneficial to them ; and finally, that all the data collected be used in an exhaustive manner to the end that from a thorough investigation of the results obtained our knowledge of the subjecf of ocean meteorology may be consider- ably increased. 174 CHICAGO METEOROLOGICAL CONGRESS. 6.— THE SECULAR CHANGE IN THE DIRECTION OF THE MAG- NETIC NEEDLE; ITS CAUSE AND PERIOD. G. W. LiTTLEHALES. A freely suspended magnetic needle is observed to be in a state of continuous tremulous motion of an involved character which may be resolved into irregular and periodic. The irregular motions comprise those sudden and rapid fluctuations in the direction of the needle which can not be predicted. The periodic motions are the solar vari- ations which include the solar-diurnal variation depending upon the hour of the day, the annual variation depending upon the day of the vear. and the solar-synodic variation depending upon the synodic revolution of the sun, the lunar variations depending upon the moon's hour-angle and her other elements of position, and partaking of the character of the tides, and the decennial variations which may depend upon the frequency and magnitude of the solar spots. Both the irregular and periodic motions referred to are of such small am- plitude in all except the polar regions of the earth that they do not effect any of the practical uses of the magnetic needle on the sea, but besides these there is another motion, having an amplitude reach- ing thirt}'" or forty degrees in some parts of the world, which is also supposed to be of periodic character, and Avhich, although not per- haps so intimately connected with the meteorologic problems of the day as the variations of smaller amplitude and period, is doubtless of radical importance in meteorologic science. At a particular instant of time the lines of magnetic force at any place, to which a freely suspended magnetic needle will set itself tan- gent, will have a certain direction and strength. The angle between the plane of the astronomical meridian and the vertical plane passing through the needle, or the line of force, is the magnetic declination, or the variation of the compass ; the angle between the horizon and the direction of the needle, measured in the vertical plane passing through it, is the dip, or inclination ; and the force with which the needle is held in the direction of the lines of force is called the mag- netic intensity. The declination and inclination, or the directional elements, which alone are concerned in a discussion of the motion of the magnetic needle, have always been treated separately in investi- gating the secular change of the magnetic needle. From 1634, when the fact of the secular variation of the declination was established, and from 1676, when the inclination or dip was discovered, reliable observations of these respective elements are recorded for the great populous centers of Europe, and soon observations of the declination or variation of the compass, a knowledge of which is necessary to mariners in the navigation of their ships, had been made by navi- SECULAR CHANGE OF MAGNETIC NEEDLE. 175 gators in most of the known parts of the world. Although the older observations, having been made without the means of precise meas- urement, are subject to a probable error of as much as 1°, they can be accepted as serviceable in the discussion of long series and serve to reveal satisfactorily the secular change of the declination. Through the results of the observations of the navigators of successive periods, series of observations of the declination extending over two or three centuries are available for most of the important maritime stations of the world. On plotting the observations at a given station with reference to rectangular co-ordinates, using values of the declination as ordinates and intervals of time as abscissa?, sinuous curves are developed which suggest the periodic character of the secular varia- tion, and it is now customary to adapt to the series of observations for their discussion a periodic function of the form . . D • 360 , „ 360 V=:A-{-B. sin. ( 4- B„ cos. t, in which V represents the variation, m the period of the cycle, t the time in years and fractions of a year reckoned from some assumed epoch, and A, B^, and B^ constants to be determined from the obser- vations. In this manner the rate of movement of the compass needle is found for any epoch within the range of observation, the times when the needle is stationary are computed, and values of the declination are predicted for current use for ten or fifteen years beyond the limits of observation within an assigned measure of precision. An examina- tion of the curves resulting from plotting the observed and computed values of the declination at a few stations, where the series extend over the greatest duration and are the most complete, will show upon what evidence rests the widespread belief that the secular variation of the magnetic declination is a periodic phenomenon. There are also available for discussion series of observations of the dip or magnetic inclination ranging from one hundred to three hun- dred years in duration, but the stations are not so numerous nor the observations so complete as in the case of the declination, except in the long-settled regions of European civilization. This is accounted for by the fact that the dip was rarely observed by navigators, except when employed in expeditions of scientific research, while the decli- nation was found as a necessary performance in the navigation of their ships. The investigation of the longer series has led to the be- lief that the secular variation of the inclination is also a periodic phenomenon ; but the data which have been observed up to the pres- ent are manifestly insufficient to warrant a conclusion that after a certain period has elapsed the declination at any given station will be the same as it is now and will then repeat its changes and again assume the same value after the lapse of the same interval of time, or 176 CHICAGO METEOROLOGICAL CONGRESS. that the inclination at that place will be found to pass through a cycle of changes and return to the same value at regular intervals of time. While the separate investigation of series of observations of declination and inclination is of great practical usefulness in gaining a knowledge of the rate of secular change of these elements and pre- dicting values beyond the range of the observations, in seeking to dis- cover the causes of the secular change in the direction of the magnetic needle and to establish or disprove its periodic character the declina- tion and inclination should be viewed as component effects of the forces that are acting. Such a view brings us to the investigation of the successive directions in space assumed at successive epochs by a freely suspended magnetic needle or the consideration of the ob- served values of the declination and inclination conjointly, instead of the separate consideration of values of the direction of the com- pass needle and of the dipping needle. As a freely suspended mag- netic needle assumes its successive directions for different times, it describes a conical surface whose vertex is the center of gravity of the needle. If a sphere of any convenient radius be described, with its center coinciding with the center of gravity of the needle, and the conical surface be extended through the surface of the sphere, the line of in- tersection will be a serpentine curve whose geometrical nature should be full}^ investigated, since it represents the actual secular motion of the needle. Preliminary analytical and graphical attempts have been made by Quetelet, of Brussels, Schaper, of Lubeck, and the mathe- maticians of the Coast and Geodetic Survey. The scantiness of data has prevented any safe deductions as to the future course of the needle. At the present time we know, with moderate accuracy, the values of the three magnetic elements for the inhabited portions of the world, and also, with a lesser accuracy, the rates of secular change in the elements, but we have rjo knowledge as to whether the needle, when it points in a certain direction at a given place, will ever return to the same position again, or whether it will at the end of a certain period assume the same direction again, and again sweep over the same path in the same period. Nor do we know that the secular- variation period, if there shall hereafter be found to be one, will be the same in all parts of the world. To promote the study of the secular change it is proposed that this Congress shall take steps to secure the co-operation of observers at the following-named places to make yearly observations of the dip and declination at selected stations and to arrange and transmit them to the U. S. Hydrographic Office at Washington where their discussion will be undertaken : BAROMETRIC PRES^RE AND OCEAN CURRENTS. 177 Christianshaab T. . .Greenland. Saint Johns Newfoundland. Acapulco Mexico. Mazatlan do. Mexico do. VeraCruz do. San Juan del Sur Nicaragua. Callao Peru. Conception Chile. Valparaiso do. Belize British Honduras. Cartagena U. S. of Colombia. Colon do. Panama do. La Guayra Venezuela. Kingston Jamaica. Port Castries West Indies. Saint Thomas do. Bahia Brazil Para do. Pernambuco do. Rio de Janeiro do. Montevideo Uruguay. Buenos Ayres Argentine Republic. Sandy Point (Punta Arenas) Patagonia. The Azores The Canaries Cape Verde Bermuda Cape of Good Hope. ..Africa. Congo River do. Delagoa Bay do. Libreville do. Loanda do. Port Natal do. Quilimane River do. Zanzibar do. Port Louis Mauritius. Hellville Madagascar. Aden Arabia. Singapore Malay Peninsula. Saigon Siam. Pekin China. Hakodate Japan. Nagasaki do. Vladivostok Siberia. Petropaulovsk Kamchatka. Sitka Alaska. Unalaska . do. Honolulu Hawaiian Islands. Tahiti Society Islands. Levuka Fiji Islands. Apia Samoan Islands. Melbourne Australia. Port Darwin do. Sydney do. Auckland New Zealand. Wellington do. 6.— RELATIONS BET^W^EEN THE BAROMETRIC PRESSURE AND THE STRENGTH AND DIRECTION OP OCEAN CTJRRENTS. Lieut. W. H. Bekhler, U. S. Navy. The student of ocean meteorology can hardly fail to notice a striking similarity between the average annual curves of isobars and the general circulation of the main currents in the five great oceans. The general circulation of the winds around the almost permanent centers of high pressure in the North and South Atlantic, the North and South Pacific, and Indian oceans, deduced from observations of wind directions extending over many years, has been demonstrated by their coincidence with the curves of isobars to be in accordance with the first principles of meteorology. There is a most intimate relation between the barometric pressure and the wind force and direction. The character of the gradients of barometric pressure is the best evidence of the force of the wind, and the great practical value of the barometer to mariners consists in the feature that the changes in the barometer readings are the most reliable of all the indications of change in the weather. 12 178 CHICAGO METEOROLOGICAL CONGRESS. The North Atlantic Pilot Chart for June, 1893, has* three charts of the North Atlantic, the main chart and two small subcharts, one of which is a chart of the curves of isobars and isotherms which obser- vations of many years indicate to be the normal condition for the month of June, and the other is a chart showing the average annual set of the surface currents of the North Atlantic. Unfortunately there are no monthly charts of the currents, but the comparison of these three charts suffices to invite scientific investi- gation of this coincidence to determine if there be any law governing the relation and the manner and effect of its operations. I submit the remarks on the Pilot Chart in relation to this analogy between the movements of the air and the curves of equal barometric pressure : The strength of the surface currents is indicated by the proportional quantity of the arrows on the chart. The greatest number of arrows are drawn where the currents are strongest. There is doubt about the direction and strength of these currents in certain parts of the North Atlantic, and our voluntary co-operating observers among mariners of all nations are requested to continue their observations to ascertain the exact set and strength of surface currents. In the Bay of Biscay recent investigations indicate that the Rennell current, as shown on the main chart, setting along the north coast of Spain east to the coast of France, and thence north and north-northwest athwart the current setting up the English and Irish channels, does not exist, at least during the summer months; but. on the contrary, it is claimed that currents set in a south-southeasterly direction into the Bay of Biscay, and thence westward along the north coast of Spain. No doubt there is a large volume of water from the Gulf Stream which enters the Bay of Biscay and must escape and cause surface currents to set out, some around Brest into the English Channel, and some around Cape Finisterre down along the coast of Portugal, the set depending largely upon the direction of the prevailing wind. By comparing the blue wind arrows on main chart with the small barometer chart and the small current chart, a striking similarity appears between the curves, showing equal barometer pressure, directions of the winds, and the general directions of the ocean currents. Among the causes which operate to produce and influence the winds and currents, this comparison suggests that the varying barometer pressure may be one of the original causes as well as a final influence on the direction of the currents, directly by its varying pressure, as well as indirectly through its relations to the winds. To what extent the barometric pressure is a factor in influencing ocean currents invites careful observations. The strength of the currents depends largely on the contour of the coast, as, in the northwest part of the Caribbean Sea, where the w^ater is raised by the westerly current, and flows through the Strait of Yucatan into the Gulf of Mexico, a reservoir which discharges through the Strait of Florida and gives abnormal strength to that part of the current system of the North Atlantic known as the Gulf Stream. In the practical presentation of meteorological conditions the Pilot Charts meet the purpose for which they are published, and Lieut. Commander Richardson Clover, ex-Hydrographer, merely intended to invite scientific investigation of this relationship of currents to wind and barometric pressure with the hope that it may lead to ascertain truths of practical application. The late Prof. Wm. Ferrel published a number of letters and BAROMETRIC PRESSURE AND OCEAN CURRENTS. 179 articles in relation to ocean currents and sea level in Science in 1886, and he concluded that the wind has little or no effect in pro- ducing ocean currents. These articles excited considerable attention, and were criticised because his theories on the ocean currents were based upon statements in regard to a difference of one meter between the sea level of the Gulf of Mexico and that of the Atlantic Ocean near New York. It is not possible in the limit of this paper to enter into all the details of the discussion of the causes which produce ocean currents. Prof. Ferrel advocated the difference in specific gravity between cold Arctic and warm tropical water as the chief factor, and that the wind was only a temporary disturbing or a locally contributing agent, while Prof. Newberry admitted the gravitation theory as a cause but a less effective one than the friction of the wind. In Croll's Climate and Time there are chapters discussing the grav- itation theory and wind theory in a manner which might be supposed to be conclusive, but the necessity of further investigation is still apparent, because the effect of differences in atmospheric pressure was overlooked. Naturally mariners have been practically investigating the subject of ocean currents more than scientists who do not go to sea, and while the former may not make such elaborate, painstaking researches and calculations, their actual experience of the ocean surface cur- rents must have weight as well as statements of the existence of cur- rents deduced from theory alone. The statement that the wind has little or no effect in producing surface currents can not stand in the face of the almost universal ex- perience that currents are generally found setting to leeward during and after a gale, excepting when in a well-known, strongly-defined current like the Gulf Stream, a wind blowing against that current may not entirely counteract it, but will, on the surface, retard its surface velocity and cause a high, rough sea. Capt. Hoffman, of the German Navy, in a pamphlet (Zur Mechanik der Meerestromungen an der Oherjldche des Oceans, Berlin, 1884) brings out the value of the wind as the chief motive force, and shows the inefficiency of gravity due to difference of temperature to produce ocean currents. The part played by deflective forces due to the earth's rotation is also well stated, but as long as waters are brushed along by the wind in any direction the tendency to depart from that direc- tion due to the deflective force of the earth's rotation is overcome, but where there is a belt of calms they begin to describe an "inertia curve," a line whose radius of curvature decreases with the sine of the latitude. In latitude 5° this radius of curvature for a velocity of one meter per second is only 42| miles, hence, when the South Atlantic Current runs into regions north of the equator, its waters turn to the 180 CHICAGO METEOROLOGICAL CONGRESS. right and form the Guinea Current, and, during the northern sum- mer, the Equatorial Counter Current. The author concludes that the winds are first, then configuration of coasts, then the rotation of the earth, and, finally, the force of gravity in their relative influence to produce currents. The wind blows horizontally parallel with the surface of the sea, or inclined at an angle either upward or downward. In the first case the parallel motion would have some effect by its friction, and much less if the wind be upward, but where inclined downward the downward pressure causes a depression and forms a ridge of water in front of this depression which offers resistance and is carried along with maximum effect. Where waves are formed the crests are im- pelled along by the wind and a considerable volume of surface water is necessarily transported by the wind. To what extent the wind carries the surface water to leeward depends upon its force and con- tinuance. In cases where a storm wave meets the sudden resistance of coast line the shores have been indundated to a depth of from 20 to 40 feet, as is reported in the account of the six typical Bay of Ben- gal cyclonic storms in the " Hand Book of the Cyclonic Storms in the Bay of Bengal," published by the Meteorological Department of the Government of India. These facts appear to me to indicate that the direction of ocean currents is most frequently to leeward. On Berghaus' Physical Atlas No. 21, Seestrdiiiu7igen, the ocean currents in connection with the areas of the permanent high air pressure in the different oceans are indi- cated. The wind circulations and curves of isobars are here also shown to coincide. The analogy between the curves of isobars and the directions of winds and currents is therefore evident. It only remains to demon- strate the nature of this relation and, if possible, reconcile all the theories of scientists with the experience of mariners. The most effective manner in which the wind can act upon the surface waters to produce a current is where it is inclined downward, and where the friction of the moving air is enhanced by its pressure down upon the water. Those areas of high pressure, more or less permanent in latitude 28° north and south, must necessarily exert by their weight of air a greater pressure upon the water upon which they rest than lesser weights of air in areas of lower pressure exert upon the water in other parts of the ocean. The differences in temperature, differences of level, «,nd rotation of the earth must combine to give a complicated, unstable resultant effect of this atmospheric pressure upon the sea. The first three con- ditions may be in operation, but the varying operation of the atmos- BAROMETRIC PRESSURE AND OCEAN CURRENTS. 181 pheric pressure must cause the final resulting effect upon the surface water. The curves of isobars around the " high " on opposite sides of the equator would leave the equatorial regions with less weight of atmos- phere than where the areas of high pressure exist. The " World's Chart of Isobars " shows that there is a normal atmos- pheric pressure on both sides of the equator from about N. 10° to S. 10°. This pressure is 760 mm., or 29.92 inches. The area of normal high barometer, 30.16 inches, southwest of the Azores, is about 700,000 square miles, and the weight of that mountain of air is 227,000,000,000 tons greater than the weight of air over an equatorial belt of equal area south of N. 10°, where the barometer is normal, or 29.92 inches, one-quarter of an inch lower than the " high." The researches of the Challenger expedition claim to have estab- lished that the general surface of the North Atlantic, in order to produce an equilibrium must stand at a higher level than at the equator. I claim that a difference of level must be the difference of effect of atmospheric pressure. The pressures under the areas of high barometer would make those areas of lower level than the equatorial regions, but the section of the Atlantic examined by the Challenger on W. 40°, and between N. 38° and S. 38°, puts the higher level near the extremities. B}' computing the effect of heat, Dr. Croll states that the surface level at N. 38° is 3| feet higher than at the equator. But the Challenger researches did not consider barometric pressure as a cause to lower the sea level. Only a small part of the ocean was examined, and it is probable that further research will demonstrate that the lowest level of the ocean is under the area of the highest barometric pressure. The isobars at about N. 40° show that the pressure there is the same as on the equatorial belt. The gradients north of 40° are steeper, and the difference of level should be greater. In the North Atlantic the area of low pressure is near Iceland, and the effect of the barometric pressure should make that the highest level. ^ In the sketch the downward pressure of the atmosphere in the *' high " and its upward pressure in the "low" are illustrated. Manifestly the enormous difference of pressure must have the eft'ect upon the incom- pressible water to push it away from the region of the " high " to that of the " low." This causes variation in the sea level and surface currents. The true final direction of the currents must be in the direction of the resultant of the force of atmospheric pressure, the wind, and the rota- tion of the earth. Generally, as the angle which these first two forces make with each other is small, the resultant will be nearly to leeward. Its strength will depend upon these forces, together with the specific gravity of the water, the time the forces were acting, the acquired 182 CHICAGO METEOROLOGICAL CONGRESS. momentum, the pre-existing condition of surface whither the currents flow, and the limiting slope of the raised sea level. The gradients of high barometric pressure are constantly varying and unequally dis- tributed, the pressure acts on the water with a downward, outward, spiral motion as on the air, and currents flow with the wind or at an angle with it, depending upon conditions of surface just mentioned. The investigations of the Prince of Monaco in the yacht V Hirondelle, during the summers of 1885 to 1888, on ocean currents show a much closer analogy between the curves of isobars and surface-water circu- lation, especially in the elliptical movement in and around the Sara- gossa Sea. The Azores are shown to be on one of the curves, and the drifts of the U Hirondelle floats describe ellipses varying in diameter from 200 miles to the coast lines on both sides of the Atlantic. The drifts of derelicts and thousands of ocean current reports by bottle papers of the U. S. Hydrographic Office indicate the same conformity of surface drift with the curves of isobars. The configuration of the coast line has an effect upon the circula- tion, and the explanation quoted from the June Pilot Chart fully explains the abnormal Gulf Stream Current. The effect of the barometric pressure on the Gulf Stream has been well established, and in Lieut. Pillsbury's report on "Gulf Stream Investigations and Results," there is one chapter devoted to the cause of the Gulf Stream and of Atlantic currents. After a very thorough examination of the gravity and wind theories, he advocates the wind theory as the principal cause, but in the closing pages of the chapter he explains abnormal currents by the effect of barometric pressure. He states that a difference of one inch in the barometric column, or about half a pound in atmospheric pressure, will give over one foot difference in the elevation of the surface of the sea. The chart of isobars for the year shows that there is a region in the North Atlantic between about N. 10^ and N. 40° of about 9,600,000 square miles where the barometric pressure is above the normal, 29.92 inches, 760 mm. North of this zone there is an area of ocean surface of about 2,300,000 square miJes where the pressure is below the normal. The maximum high is about 30.16 inches and the minimum low is 29.69 inches, or a difference of about 0.47 of an inch. If one inch in the height of the barometer represents about half a pound in the atmos- pheric pressure per square inch, the total difference of the weight of atmosphere upon these regions reaches an enormous figure, sufficient to cause a very decided difference between the levels of the sea at the areas of the maximum high and minimum low. (This difference, I believe, amounts to about 20 meters.) The surface water will be forced up an incline in the region of the "low." The lack of pressure, or rather the diminished air pressure in the low region taken in con- Plate ^Vll* Beehler. BAROMETRIC PRESSURE AND OCEAN CURRENTS. 183 nection with the lesser area, will still farther enhance the accumula- tion of the water in the region of the " low." The atmospheric pressure in the Atlantic causes the accumulation in the western part of the Caribbean Sea, and the sea level there and in the Gulf of Mexico is one meter higher than that off Sandy Hook, N. Y. The Gulf Stream, thus formed, unites with the waters of the At- lantic circulating around the " high " and flowing up along the Bahamas and following the United States coast line to Hatteras. The waters continue on, but after passing the Grand Banks they meet with no further coast resistance and are pushed out by the barometric pressure, which is constantly diminishing, into the Arctic until the upward slope is so great that the diminishing pressure can no longer force the water there. A large volume of water flows down between the Azores and the coasts of Portugal and Africa, where the pressure is less than the maximum, and then continues circulating around as before. The water thvis continually pressed away by the high pressure from the mid North Atlantic must be replaced, and. consequently there are undercurrents of cold water from the Arctic and northern part of the North Atlantic to restore the equilibrium. These cold currents will, on account of their specific gravities, fall below the warmer surface currents, and while this barometric pressure is acting, these cold cur- rents flowing south cannot appear on the surface, for if they did appear they would, under normal conditions, be necessarily brushed back again toward the Arctic. Where the configuration of the coasts has deflected this circulation of water away from the shores, the cooler currents may there appear on the surface, and, consequently, we find a cold current from the Arctic along the coast of Labrador, sneaking in around Newfound- land and close along the United States coast to Hatteras and Florida. In the report for 1891, Appendix No. 10, of the U. S. Coast and Geodetic Survey, Prof. E. E. Haskell publishes an account of obser- vations of currents in the Straits of Florida and Gulf of Mexico, and on page 347 he states : Over a water surface unequal atmospheric pressure and wind both become causes, acting generally at an angle with each other to produce a current. The former is the equivalent of a head to be spent as a gravity force in the direction of the trend of the barometric gradient, while the latter acts by friction on the surface to produce a current in its direction. There is little or no information extant as to the current that any known velocity of wind and barometric gradient will produce, nor is there a definite enough relation between direction of wind and trend of barometric gradient to permit of making more than the general statement that the current should be in the direction of the resultant of the two forces. I quote this by permission, and this pamphlet contains tables con- necting the observations of currents with meteorologic data. I also 184 CHICAGO METEOROLOGICAL CONGRESS. have in a letter from Prof. Haskell the further statement that, " If I had at my command daily observations of the direction and force of the wind and the reading of the barometer from stations so located as to surround the Gulf, I could predict the currents much as our weather is predicted." In investigating the ocean currents it must be remembered that the mountain of air in the region of the almost permanent " high " is not constant in extent or in exact locality. I have taken the average annual location and direction of the areas of the " high " in the North Atlantic. This varies, and the Pilot Chart for each month shows these variations graphically. Again, near the belt of normal atmos- pheric pressure the air circulation around the " high " is accompanied by other circulations, both cyclonic and anticyclonic, and these storms will temporarily disturb the normal condition and cause variations in the current both in strength and direction. To follow the movement of a cyclonic circulation across the Atlantic toward Europe and the Arctic the waters under the center must be relieved of pressure by the extent of the abnormal difference of air pressure. The winds also in the cyclonic circulation flow in, around, and upward, and these causes must contribute, not only to raise the level of the surface water, but also to make this increase of level to take place in a comparatively small circular space ; hence, the remarkable high, almost vertical, seas which are raised and fall with such destructive effect all around in a confused mass in the center of a cyclone. The storm waves quoted from the Bay of Bengal typical cyclones are explained on this theory, and further examples might be quoted to show that the currents of all oceans and at all times are chiefly due to the atmospheric pressure. Our knowledge of the ocean currents is far from exact, and the object of this paper is to invite investigation of the subject of ocean currents in connection with the barometric pressure. It is extremely difficult to ascertain the direction and strength of ocean currents. As a rule the reports of currents experienced are really the difference between an estimated run of a ship in twenty- four hours by dead reckoning and the more exact run as determined by astronomical observations. All the errors of the estimated course and distance made good for twenty-four hours are added and ascribed to currents which, for half the time, may have been in one direction at one rate and at other times in other directions at different rates. With the sextant it is rare that a captain can determine his posi- tion more than once in twenty-four hours, and until he has means of finding his position accurately at sea more frequently, the reports of currents experienced will be unreliable. I have recently invented a nautical instrument, the solarometer, FLUCTUATIONS OF STORM TRACKS. 186 by which a vessel's exact position can be determined at sea at any time of day or night that any heavenly body is visible in the sky, independent of the visibilit}^ of the sea horizon and without any elaborate calculations. The speed of the ship through the water being measured every hour by the patent log, and the exact geographical position being deter- mined by the solarometer every hour, the difference between the speed through the water and that made good over the ground will be the amount of current experienced. It is difficult to estimate the importance of a full and complete in- vestigation of this relationship of the barometer to the ocean cur- rents. If the investigations demonstrate the exact character of the relations it may be possible for a mariner to see from one or more observations of the currents and the readings of the barometer the meteorologic conditions of a wide range over the ocean. Or, having barometer readings and meteorologic conditions, he may predict currents. There is, of course, a certain amount of momentum to be overcome to cause a current, and an element of time would have to be consid- ered, but investigation of the subject will doubtless reveal much of the mystery with which it is now connected. To the science of meteorology the subject is one of the most im- portant. The influence of the Gulf Stream and of the tropical waters which circulate with the Gulf Stream around the region of the almost permanent " high," upon the climate of Europe, and similar influences of like circulations on all five oceans all over the world, upon the climate of these regions are secondary to no other meteoro- logic phenomenon. Exact knowledge of the direction and strength of the ocean currents so determined will be of incalculable benefit to commerce and mankind. 7.— PERIODIC AND NON-PERIODIO FLUCTUATIONS IN THE LAT- ITUDE OF STORM TRACKS, Dr. M. A. Veeder. There are certain rearrangements in the distribution of atmos- pheric pressure of world-wide extent which, at times, continue throughout entire seasons, or even for series of years, and which, likewise at times, appear irregularly and sporadically at individual dates, which evidently must depend upon some cause capable of affecting the entire earth. The most prominent feature in such rearrangement is a displacement in latitude of the belts of anti- cyclones on each side of the equator with consequent deflection northward or southward, as the case may be, of the courses taken by 186 CHICAGO METEOROLOGICAL CONGRESS. storms prevailing at such times. A very notable instance of one species of such displacement occurred in 1877-'78, when anticyclonic weather conditions were very persistent in low latitudes, as evidenced by the extraordinary extent and severity of the droughts which belted the entire earth in the equatorial regions. Coincidently, the diver- sion of storm tracks into higher latitudes was shown, especially by the phenomenal mildness of the winter seasons. Ten years later, in 1888-'89, there was a repetition of these same characteristic features dependent upon atmospheric distribution. In this instance the mildness of the winter season, particularly that of 1889-'90, seems to have extended even into the Arctic regions, causing floating ice to appear off the coast of Labrador and Newfoundland in great quanti- ties throughout months in which it is rarely seen at all in that loca- tion. At the same time on the North American continent there was a marked deficiency in the severity and extent of cold waves, and storm tracks had their centers far north for extended periods. The same mildness appeared, likewise, in the northern parts of the eastern hemisphere, while in India, on the other hand, anticyclonic conditions predominated, there being " a general rise of abnormal barometric pressure for a considerable period * * * and scanty rainfall throughout the year." {Nature^ June 5, 1890, p. 134.) It is not within the province of a brief summary, such as the pres- ent, to do more than indicate leading features. Suffice it to say that the extraordinary persistence and extent of the distribution of the types of weather described in the years named is not only in strong contrast to average conditions, but is in still greater contrast to those prevailing in years when the divergence from the normal is in an opposite direction, anticyclones with greater dryness and stronger cold waves prevailing in higher latitudes, with corresponding dis- placement of cyclonic weather conditions into different and, for the most part, lower latitudes. The present year affords an example of this variety of divergence from the normal, both in this country and Europe, the winters in northern latitudes being distinguished by a severity in strong contrast to their mildness during the years pre- viously named, and the areas distinguished by phenomenal droughts during the summer likewise being transferred to higher latitudes with coincident strengthening of the storms and hurricanes of low latitudes. In this connection it is worthy of note that what is thought to have been the lowest reading of the barometer ever re- corded on the Atlantic was met with during a storm far south last December. So, too, the West Indian hurricane season now approach- ing promises to be severe. Coincidently, complaints of droughts are heard from the interior of the North American continent and from the north of Europe, Great Britain, especially, suffering severely. In order to bring out completely these contrasts in weather conditions FLUCTUATIONS OF STORM TRACKS. 187 it would be necessary to consider in detail the effect of rearrange- ments in the distribution of atmospheric pressure upon rainfall, cloudiness, temperature, the direction and force of the winds, and the like, not only at different seasons of the year, but also in partic- ular localities, which, manifestly, is a task of considerable magnitude. But without entering thus into detail it is sufficiently evident for the purposes of the present discussion that the distribution of cyclonic and anticyclonic weather conditions throughout the globe varies in different years in the manner which has been described. The broad features of these types of weather are readily distinguishable, both on land and sea and in summer and winter, under all the modifications which they thus undergo, so that their transference from one latitude to another can be traced with a good degree of confidence. Indeed such transference and localization of weather types through more or less extended periods is one of the most striking and familiar facts of meteorological observations. In like manner, for brief intervals, there may intervene strongly marked but relatively transient divergences from the more persistent types of weather prevailing in the manner which has been described. Thus, upon some particular date, anticyclones may suddenly appear in higher latitudes than that which they had been accustomed to fre- quent for weeks or mouths preceding, and begin to move eastward with more activity and become stronger, the storms prevailing along their peripheries being modified likewise in respect to the courses which they pursue and the energy which they display. In such cases an impulse of some sort appears to have been imparted suddenly to the atmosphere, as a whole, the increased rapidity of eastward move- ment and intensification of storm action being apparent in the case of all cyclones and anticyclones prevailing at the time. Thus, in- stances have been noted in which storms in America and Europe, and off the coast of Japan, have acquired phenomenal intensity on the same day, constituting a well-defined period during which the energy of atmospheric movements was largely increased, anticyclones as well as cyclones being everywhere strengthened. In such cases as these there does not appear to be any delay, such as would be required if the increased activity displayed were dependent upon any slow pro- cess of warming up continents or seas. On the contrary the re- arrangement in the distribution of atmospheric pressure (and inci- dental storm action) begins promptly and in such manner as to in- dicate that its origin is not dependent upon local terrestrial condi- tions, the part performed by such conditions being, apparently, to modify rather than originate the activities in question. Thus, there are in general rearrangements in weather conditions so well defined, and upon such a large scale, that it is difficult to resist the conclusion that the atmosphere, as a whole, is under the control 188 CHICAGO METEOROLOGICAL CONGRESS. of forces which have a common origin and which undergo variations at their very seat of origin. It would seem that it ought to be possi- ble to determine to the best advantage the nature and mode of opera- tion of such forces by a careful study of the instances in which the divergences from the normal are greatest. For several years the writer has been collecting information bearing upon this point, the outcome being the conclusion that the divergences in question must depend ultimately upon some form of solar variability, it being con- ceded on all hands that the sun is the great source of atmospheric control. As to the essential nature of this variability there is, how- ever, a question. From current views respecting atmospheric con- trol, we should naturally expect it to consist in variation in the sun's power of emitting heat. It is true that the weather conditions to which attention has been called present anomalies in respect to tem- perature, but these have reference to distribution rather than total amount. Thus, investigators using data from different parts of the earth have reached precisely opposite conclusions as to whether the sun is hotter or colder, and that, too, in the very years in which the departures from the normal of the kind indicated have been largest. In like manner, if averages are taken from a sufficiently large part of the earth, the variation of temperature from year to year is insig- nificant. So, too, the exposure of properly guarded thermometers to the direct rays of the sun in localities best adapted for such experi- ments, and under the most suitable conditions, has thus far given no evidence of variations in the sun's power of heat emission adequate to explain the facts to which reference has been made. It is a ques- tion, indeed, whether variation in the amount of heat falling upon the earth, as a whole, could produce the diversified local effects appar- ent and maintain them in the manner which actually appears. As a matter of fact, however, it is not yet known whether the sun is hotter or colder when freest from spots. The observations thus far made agree, however, in showing that the interposition of the atmosphere and its contents, and especially of the aqueous vapor which it con- tains, modifies the transmission and radiation of heat to such an ex- tent that this and not solar variability may be the source of the changes in temperature distribution to which reference has been made. This being the case, these temperature anomalies are to be regarded as a mere incident in the rearrangement of atmospheric dis- tribution rather than its cause. Thus it becomes necessary to look elsewhere than to variations in the heat-giving power of the sun for the source of atmospheric control. At this point and in this connec- tion a relation of the weather conditions described to the distribution in latitude of the spots on the sun becomes of very great interest. It is found that the fluctuation in latitude of the belts of anticyclones on the earth and consequent diversion of storm tracks to which refer- FLUCTUATIONS OF STORM TRACKS. ^ 189 ence has been -made follows, and is in direct proportion to a like change in latitude of the belts in which spots are most frequent on the sun ; that is to say, in years in which spots appear in high lati- tudes, anticyclones do likewise, and vice versa. The transient and irregular deviations from this order constitute a case by themselves, and are to be studied in connection with the evidences of spasmodic outbreaks of solar activity on the one hand, or the fitful intervals of solar quiet on the other, which may interrupt the regular order of events in progress in any particular year or series of years. The purpose of the present discussion is not to enter very much into the details of the evidence, which would be impossible within the limits assigned, but rather to indicate in a general way the nature of the problems involved as an incitement to further research. In the judgment of the writer, based upon such study as he has been able to make, there is ground for the belief that there are special forms of solar activity, not as yet perhaps fully identified, and cer- tainly not as yet fully understood, which exercise powerful terrestrial effects independently of any perceptible attendant variation in the amount of solar heat falling upon the earth as a whole. In brief, these special solar activities appear to be of the nature of electro- magnetic induction, which may be attended by incidental heating effects, it is true, but these effects have a different distribution and depend upon conditions altogether unlike those which exist in the case of simple radiation from a source of combustion. Temperature distribution in the case of electro-magnetic induction depends upon the direction assumed by lines of force in a magnetic field, thus con- stituting a special form of radiant energy having characteristics essentially different from those manifest in the case of heat or light. From this point of view the manner of recurrence of auroras and magnetic storms and their relation to disturbances upon particular parts of the sun become an important subject of research, as afford- ing the means of acquiring a knowledge of the limitations under which electro-magnetic inductive effects are conveyed from sun to earth. Especially important is the evidence that these effects are propagated at a definite angle, originating a periodicity of magnetic phenomena corresponding to the time of a synodic rotation of the sun, thus differing again from heat radiation which proceeds from the sun indifferently in every direction, and not at a certain angle exclu- sively. The determination of the solar meridian, or in other w^ords, the angle at which the inductive effect is exercised is of the utmost importance. The tables constructed by the writer for the purpose of such deter- mination are very voluminous, covering nearly all lists of auroras in existence and very extensive records of magnetic storms and sun spots. The practical outcome is that the inductive effect proceeds 190 CHICAGO METEOROLOGICAL CONGRESS. chiefly, if not exclusively from disturbed portions of the sun when at the eastern limb, and that such effect may at times originate thun- derstorms instead of auroras, the substitution of one or the other of these two classes of phenomena depending apparently upon the location of the originating solar disturbance relative to the plane of the earth's orbit when at the eastern limb. There is evidence also of a terrestrial localization of these phenomena, dependent in part, ap- parently, upon the physical conditions existing at the time in various parts of the earth, and in part upon a concentration of effect at certain hour angles from the sun. Thus, there are diurnal maxima and secondary maxima both of thunderstorms and auroras, and the regions frequented by them have a belt-like distribution in magnetic latitude. From this it appears that the lines of force along which the inductive effect proceeds have a very definite arrangement, and that there are modifications of effect in particular portions of the field which these lines occupy, giving rise to thunderstorms instead of auroras, or vice versa, as the case may be. It would seem that the origin of the whole process is through electrification of particular por- tions of the sun's immediate surroundings through the agency of the turmoil of chemical and other activities due to the special violence of the eruptive forces there in operation, as compared with the rest of the sun, and that the inductive effect is propagated outward into space from these sections of the sun dynamically, or, in other words, in virtue of the motion of rotation. The dynamic origination of electrical currents has been greatly familiarized of late by the commercial applications of the principle now in ordinary use for many purposes. Such origination depends upon a very different set of conditions from those involved in thermo- electric action to which these forms of solar activity have generally been referred heretofore. There is no evidence whatever that a mag- netic storm is allied to or dependent upon heat radiations in any sense or to any extent whatever. Its method of origination and propagation is quite different in every respect, and any heating effects that may attend are incidental and remote. Thus there is a form of solar activity having its own distinguishing characteristics and exist- ing as an entity by itself which deserves most careful study. The earth certainly is comprehended within the range of its operation, and it is altogether likely that the inductive effects thus experienced extend throughout the entire solar system, reaching every particle of meteoric dust and debris, and the vapors, if such there be, in inter- planetary space, as well as the planets themselves. All these masses of matter charged up by induction exhibit permanent, subpermanent, and temporary effects, in accordance with which they act and react upon each other and likewise upon the sun itself, in conformity with the laws governing induction. FLUCTUATIONS OF STORM TRACKS. 191 In the judgment of the writer it is the reactionary effect upon the 6un itself of these inductive forces, causing rearrangements in the distribution of the vapors in its vicinity, as seen during eclipses, that determines the formation of spots and their varying location in lati- tude in a manner altogether similar to that seen in connection with the coincident changes in latitude of the belts of anticyclones on the earth. In any event, the fact that these rearrangements of the vaporous surroundings of sun and earth undergo similar variations in respect to location in corresponding years points to community of origin of these effects, and their evident relation to magnetic phe- nomena of the sort which has been described is such that it would seem not unwise to shift, if necessary, the point of view for the con- sideration of the entire subject, and to attack the problems at issue along the lines indicated in this discussion. This involves nothing less than a reconsideration of every fact and conclusion in respect to meteorological science from a standpoint altogether different from an assumed variability of solar heat. It may be necessary to go so far as even to discard provisionally and tentatively the convection theory of the origin of storms, as ordinarily held, in order to determine fairly and completely the part which electro-magnetic induction of solar origin plays independently of heating effects. The distribution of temperatures, both in a hori- zontal and in a vertical direction in cyclones and anticyclones, and the velocity and extent of the associated wind movements, likewise in a horizontal and vertical direction, are not easy of explanation in conformity with the convection theory of the origin of storms. Thus, in tropical hurricanes, where the violence of the wind move- ment is extreme, the temperature gradient is small. Again, in the case of a severe storm remaining stationary like the New York bliz- zard, it would seem that the gravitational inflow of such enormous masses of air ought to involve a filling up process. Certainly, current views respecting the forces concerned in storm action do not give the slightest intimation as to where all the air goes in such a case as this. In view of such facts as these, and without multiplying further illustrations, it would seem to be not only reasonable but necessary to institute an inquiry as to whether forces other than those hereto- fore taken into the account are not concerned. To this end especially important is the identification of the solar and other conditions on which auroras and magnetic storms depend, growing out of which there comes an apparent relation to thunderstorms. By the aid of the clue thus obtained it becomes possible to study the behavior of the atmosphere on critical dates, and during critical periods, whose identification is secured through a knowledge of these solar and asso- ciated conditions. As has been intimated throughout the course of the discussion the fluctuation in latitude of anticjxlonic belts and 192 CHICAGO METEOROLOGICAL CONGRESS. storm tracks both on the grandest possible scale, as affecting climate through series of years, and in individual instances on single dates, is most likely to afford an insight into the meteorological relations of electro-magnetic forces of solar origin. These forces certainly play a part in the economy of the solar system, and there are indica- tions that this part is far more important than has heretofore been supposed. 8. — NORTH ATLANTIC CXJBRENTS AND SURFACE TEMPERA- TURES. Lieut. A. Hautrkux, French Navy. It is impossible to speak of meteorology or the physical geography of the sea without the spirit of the immortal name of Lieut. Maury. He it was who systematized the best manner of making observations and enunciated the principles and general laws of the circulation of the atmosphere and the oceans to the scientific world. In his school this science has been studied, and especially in the United States, where it has been most developed on land and sea. It is in that vast country, washed by two oceans, possessing both tropical and polar climates, the highest mountains and most exten- sive plains, rainless deserts and the most fertile regions, with coasts washed by the greatest oceanic river in the world and annually re- ceiving glacial tributes from Greenland — it is there where the ele- ments of heat and cold, dryness and moisture, rage and produce with greatest force the phenomena caused by the conflict. There the science of meteorology, based upon actual observations, has made the greatest progress. There, also, the public is most promptly noti- fied and warned of meteorological disturbances, and measures taken to prepare for them. The grand laws of meteorology, which Maury so admirably reduced to harmony from phenomena often of the most fleeting character and complicated by local anomalies, have by experience been demon- strated in detail to be of great service for the security of navigation. Some of these points, especially those relating to the currents and surface temperatures of the North Atlantic, we will proceed to inves- tigate in this paper. The scientific expeditions so wiselj' directed by the governments of the United States, England, Germany, and France for the physical examination of the ocean, in connection with the deep-sea sound- ings for the trans- Atlantic submarine cables, have covered the sea so thoroughly with a net of observations that scarcely any important feature has escaped their investigations. They have established that no part of the ocean is at rest, but that the entire mass of the ocean from the surface to the profoundest depths is constantly in motion NORTH ATLANTIC CURRENTS. 193 to re-establish the equilibrium destroyed by the action of tides, the pressure of winds, and the changes of temperature and density. The waters of the ocean are subjected to a double circulatory move- ment, vertical and horizontal. The vertical motion is determined by the study of the submarine isotherms. The cold polar waters sink below the waters of temperate zones, and ascend toward the surface in tropical zones, where they cause great evaporation. The horizontal circulation on the surface was known to ancient navigators who utilized or defied it. This is found in all oceans more or less permanent or intermittent and its most energetic actions are produced near the coasts by the tidal action and at sea by the effect of the wind. The action of the wind upon the surface water is most effective ; it produces the waves and carries the molecules of water to leeward, and often in a cul de sac raises the surface many meters high, and under continuous action often stops the tides. Especially in the Atlantic the continuous action of the northeast and southeast trades forces the inter-tropical waters westward, where the configuration of the coast at the mouth of the Amazon River deflects the waters to the Windward Islands, through the numerous passages between these islands into the Caribbean Sea. The barrier formed by the large islands of Puerto Rico, Haiti, and Cuba, compels the accumulating waters to enter the Gulf of Mexico, whose surface level is thereby raised, and then finds its only exit between Cuba and Florida. Thence these waters meet the coral banks of the Bahamas and form an enormous river with a rapid, current which follows the coast of the United States to Cape Hatteras, where it is known as the Gulf Stream. Thence deflected to pass south of Newfoundland and the Grand Banks, it opens out like a fan and spreads over the sur- face of the North Atlantic, with a loss of its speed and much of its distinctive character. The name of Lieut. Pillsbury is forever associated with other enter- prising scientists of the United States Government who have so com- pletely investigated this remarkable current. After the waters of the Gulf Stream spread out over the sur- face the axial direction follows that of a great circle which passes north of the Azores and reaches the coast of Portugal. Here two causes operate to influence the current. During the summer the north winds in prolongation of the northeast trades along the Portugal coast brush these waters to the southward, where they come under the influence of the northeast trades and the region of the Equatorial Current; during the winter the southwest winds push these waters from the mid North Atlantic to the northeast to the shores of Ireland and Norway. 13 194 CHICAGO METEOROLOGICAL CONGRESS. There are besides the Gulf Stream other currents which are recog- nized as permanent and have certain general features, such as the Labrador Current, caused by the melted snow and ice of polar regions, and the Counter Equatorial Current, produced by the southwest winds of the coast of Africa. These currents have been found by observations of navigators and from the drift of floating objects, such as ice, wood, bottles, and hulls of vessels. The observations conducted for the Pilot Charts, published by the Hydrographic Office of the U. S. Navy, at Washington, D. C, have been of great importance. These show the precise resultant of the complicated causes to which a floating vessel is subjected. If the hull of a derelict vessel, immersed 6 to 8 meters in the water without exposing to the wind more than a portion of its dismantled hull, should for several days in a month drift in a certain direction it is evident that the mass of water in which it floats must have moved in the same direction. There are other surface movements of the sea which are designated as permanent currents, but which facts show are subject to important and unforeseen variations. An examination of the Pilot Charts will show several examples. We beg the reader carefully to examine these charts, and especially certain supplements which have been published by the Washington Hydrographic Office, viz : " The Drift of Bottle Papers," July, 1891 ; " The Derelict Schooner White," February, 1889. We will proceed to investigate the following : The Norwegian Cur- rent, the Rennell Current, the currents of the coast of Portugal and the west coast of Africa, the currents of the Sargasso Sea, and the temperatures of the sea from Bordeaux to the La Plata River, from Bordeaux to New York, and in the Bay of Biscay. THE NORWEGIAN CURRENT. In summer the Atlantic, north of the Azores, does not appear to be so much under the influence of the Gulf Stream, and yet in that season the stream has its greatest extension toward the north, a fact which is demonstrated by the tracks of the derelicts Twenty-one Friends, in July, August, and September, the White, in June, July, August, and September, the E. Davis, in August and September, and the Hunt, in July. In the season when the southwest and west winds prevail the waters are pushed northeast and east. The fact is shown by the drift of numerous derelicts published on the Pilot Charts, and of the drift of bottle papers in the special supplement of the Pilot Charts, 1891-'92. Nevertheless, even in this season, the condition of the barometric pressure on the Atlantic prevents the westerly winds from allowing these waters to reach the shores of Europe. The surface waters do Plate Vin. Currents of the North Atlantic in 1892. Path? of 'drifting wrecks. Eauireux. 20 30 20 Temperature of water in the Bay of Biscay. 1 Jjongfitades West of Osreenrrich. 70 9 __ 3 y <^ ^ Octoher JVoyem.be7 MeceTttbef NORTH ATLANTIC CURRENTS. 195 not always follow their usual course, as is shown by the tracks of the derelicts Countess Dufferin, Vestalinden, and Daphne, which drifted toward the south and south-southeast. (See Plate viii.) For dur- ing these months anticyclones covered the North Atlantic, and rare depressions traversed the European coasts, traveling from north- northwest to south-southeast. These facts appear to prove to us that the wind predominates in giving direction to the surface waters of this part of the Atlantic. Fine weather and light winds prevailed during the summer, and the drifting derelicts show that then the surface waters are most fre- quently transported with continuous regularity. During the season when strong winds blow from the south and west the waters are forced to the north and east, but whatever may be the cause, those strong west winds fail to make the derelicts always follow the im- pulse they receive. Drifting bottles launched northwest of the Azores by the yacht L'Hirondelle, which were recovered in the Azores Islands, clearly prove that this current has not the degree of permanence which has been ascribed to it as a branch of the Gulf Stream. This current is absolutely dependent upon the surface winds which in summer force the waters of the mid-Atlantic toward the European coasts with a temperature always above 10° C. CURRENTS IN THE BAY OF BISCAY. The so-called Rennell Current is represented as a derivative of the Gulf Stream which meets the coast at Cape Finisterre and then divides into two branches, one of which flows south along the coast of Pprtugal, the other enters the Bay of Biscay, following the north coast of Spain, thence flows north and northwest along the French coast and is lost in the general currents of the channel. The drifting derelicts are again quoted to present facts not in accord with this theory, viz: Tiventy-one Friends, in 1886; Stormy Petrel, in 1887 ; Emilie and Petty, in 1888 ; Atlas, Carrier Dove, and Herman, in 1890; schooners Ryerson and Helios, in 1891. (See Plate VIII.) Besides, in the drift of bottle papers, Nos. 12, 17, 29. and 30 have also followed anomalous directions. (See Plate ix.) The Prince of Monaco, after his admirable experiments in the yacht UHirondeUe, concludes that the currents in the Bay of Biscay are contrary to the Rennell Current. He estimates that the waters from the Gulf Stream divide at Ushant; one branch goes up the channel and the other enters the Bay of Biscay, flowing southeast, then south along the coast of France, and finds outlet westward along the north coast of Spain. If these two theories are correct, we have thought that there might be a point on the French coast in the vi- cinity of Arcachon where currents would be found regularly setting 196 CHICAGO METEOROLOGICAL CONGRESS. north and south. This must appear logical on account of the uniform regularity of the coast line there, so that this important sheet of water is not influenced by eddies such as would be found upon an indented shore. There is, fortunately, at Arcachon a fishing industry having five steamers, under the direction of Mr. H. Johnson, who readily con- sented to assist our investigations and ordered bottle papers to be launched for this purpose. The captains of these vessels made the following reports, which have been forwarded to the Hydrographic Office at Washington, D. C. Extract from the report of Capt. Pateau : The currents are not regular. They are caused by the wind; with north winds the currents set south, and with south winds they set north. At times there is no current with the wind east offshore. In winter the currents are stronger than in summer. Extract from the report of Capt. Durand : I have always noticed that when the wind is south or southwest the currents set north along the coast of France, but with the wind northeast or northwest they set south to- ward the bottom of the bay, and thence flow west along the coast of Spain, with a velocity proportional to the strength of the wind and its continuance. Extract from the report of M. Silhouette, of Biarritz : Formerly many small trading vessels frequented Bayonne and were often lost. The vessels were carried perpendicularly to shore, head on. Subsequently their sterns were carried south by the current from the north. All these reports agree that the currents in the Bay of Biscay are absolutely dependent upon the prevailing winds. In order to confirm these reports we have, during June and July of this year, thrown overboard a number of bottles, three-fourths full of water, attached to floats by a line two fathoms long. The length of the line being such that the bottles might be readily recovered on the coast at low tide. These bottles were thrown overboard 12 to 30 miles from the coast in depths of 40 to 60 fathoms. The results of these experiments were collected and sent to the Hydrographic Office at Washington, D. C, which office is hereby re- quested to communicate them to the Congress. The experiments were commenced on May 25 and continued at the rate of three or four every week. The last one, recovered on July 3, had been thrown overboard on June 21, by the steamer Oceanique. Out of the eigh- teen or nineteen bottles thrown overboard, thirteen were recovered — a large proportion. (See table on page 198 and Plate ix.) The currents observed on board the vessels where the bottles were thrown overboard were weak and the general set was south-southwest. The bottles were adrift in the water for an average period of fourteen days, and the resultant direction of their drift was to the south-south- east. Not one bottle was found north of the place whence it was set adrift. This is contrary to the theory of the Rennell Current. Drifting bottles, June, 1 893. Plate IX. Haxdreux. NORTH ATLANTIC CURRENTS. 197 North of the region observed the prevailing wind during the period from May 25 to June 22 was toward the southwest, while south of that region, near Biarritz, the mean direction was toward the east- southeast. The resultant direction of the drift of the bottles was south-southeast, which direction is the mean resultant of a drift first to the southwest and then east-southeast. The velocity of the drift, derived by dividing the distance drifted by the number of days afloat, was for twenty-four hours a maximum of 4.2 miles, a minimum of 1.4, and a mean of 2.5. Upon examining the sketch it will be seen that the bottles may be classed in two groups — A, B, H, L, and N, which drifted east-south- east, and C, D, E, F, G, I, K, and M, which drifted toward the south and south-southeast. There are two charts of the currents of the Bay of Biscay, one by G. Simart, Lieutenant, French Navy, published in 1889, and one by the Prince of Monaco, 1892. In the Simart charts the currents of the Bay of Biscay are laid down as setting south at the rate of 4 to 5 miles in twenty-four hours. In the chart of the Prince of Monaco, the currents are laid down as setting east at the rate of 6.6 miles for twenty-four hours. The two directions are at right angles to each other. Our experiments do not reconcile the difference. The tracks of shortest periods are those of the Prince of Monaco, the longer tracks are those on the chart of Lieut. Simart. But there is one fact to be remarked that on the chart of the Prince of Monaco the shortest drift tracks, considered as best indicating the direction and set, were made during September, October, November, and December, 1886. In this year the autumn was characterized by excessive rains in the Bay of Biscay. The records of the observatory at Bordeaux show a rainfall for September of 102 mm. and October, 205 mm. This is double the mean rainfall. This excessive rainfall is certain proof of the frequency and violence of the west winds in the fall of 1886. It is probable, therefore, that the effects of the wind transporting the water caused the current to set east at the rate of 6.6 miles per twenty-four hours, a rate three times as fast as was experienced in our experiments during June of this year. Our results were obtained during a period in which fine weather prevailed, and they show that floating bodies drift to the east and south of the point of departure during the month of June, and that they are pushed with a sl(5w and irregular velocity. A set of 2.5 miles in twenty-four hours can scarcely be called a current. These facts demonstrate that the Rennell Current has neither the permanence nor the velocity with which it is credited, and that at least during the summer, along the French coast, the current sets more frequently south than north. It is also seen that it sets toward^ the beach, a feature most dangerous to vessels. This explains the 198 CHICAGO METEOROLOGICAL CONGRESS. dangerous character which has always been accredited to the Bay of Biscay. No sailing vessel can beat off the coast while the winds and currents both set her on. These facts show that the wind is the preponderating factor in causing the currents whose direction and set are often modified by the configuration of the coast. They prove also that near the coast there is a surface movement which is dangerous to navigation and should be studied carefully. Table of drifting bottles near Arcachon. Thrown into the sea. Recovered. Drift. Designating letter. A B C D E F G H 1 . K L M N Lati- tude. 44 12 44 II 44 12 44 40 44 4° 44 3° 44 24 44 07 44 36 44 30 44 13 44 30 45 32 Distance off- sliore. Miles. 34 Current. Lati- tude. SW. SSE. 8W. NW. NW. NNE. NNE. SSW. NNE. SW. SW. SW. SW. Longi- tude, Green- wich. 44 08 44 07 43 44 44 00 43 44 43 43 43 57 44 02 43 26 i 43 56 43 55 I 43 22 I 45 20 I 20 I 20 I 24 I 21 I 24 I 24 I 28 I 21 I 33 I 28 I 28 I 54 I 12 Distance. Direction. MUes. S. 70 E. S. 78 E. S. 18 E. S. 10 E. S. 5 E. 8. 15 E. S. 20 E. S. 70 E. S. 3 E. S. 25 E. 8. 34 E. S. 4W. S. 70 E. Days. Rate of drift. MUes. 2.9 2.8 1-7 1.4 4.2 2-5 2.4 3-8 CURRENTS OF PORTUGAL AND WEST COAST OF AFRICA. For this the observations of the steamers of the Messageries Mari- times, taken from time to time for six years with about four each month, are considered in detail. These steamers ply along the coast of Portugal and Africa as far as the Cape Verde Islands. The cur- rents have not the permanence to which they are credited, but in each season there are certain features. Winter. — Along the coast of Portugal the current sets north and north-northwest ; from Madeira to the Canary Islands the current sets north-northeast, and from the Canary Islands to Dakar the cur- rent sets west-southwest. The Counter Equatorial Current sets southeast. Summer. — Along the coast of Portugal the current sets south to south-southeast. From Madeira tQ the Canaries the current sets south-southwest. From the Canaries to Dakar the current sets south- southwest. The Counter Equatorial Current sets east. A velocity of about one mile per hour has been foun'd between the Canaries and Dakar and between the equator and Pernambuco. The difference in direction in summer and winter corresponds with the changes in the direction of the prevailing winds in these regions in these seasons. During the winter southwest winds are frequent be- tween Madeira and Cape Finisterre, and they force the water to lee- ward to the north. In summer northerly winds prevail and force NORTH ATLANTIC CURRENTS. 199 the water south. Near Dakar, in the period of the southwest mon- soons of the coast of Africa, the Counter Equatorial Current carries warm water ashore near the Arquin Bank, Cape Blanco. It is to be noticed that in the trade-wind regions the westerly com- ponent of the current is always greater than that of the wind. THE SARGASSO SEA. Southwest of the Azores the waters of the Atlantic form a large whirlpool analogous and corresponding to the general circulation of the surface winds. The movement is demonstrated by the drifts of the derelicts Telemach, Drury, Wyer G. Sargent, and Fannie E. Wolston. The diameter of the curves of these tracks is from 350 to 400 miles. These drifts are evidently the resultant effects of the surface winds. For in this sea the drifts to the westward took place from July to November during the period when the trades extended farthest north, and to the north and east during the winter months, when the jsre- dominant winds in that region were south and west. The agreement in the directions of the winds and the oceanic surface drift is there- fore complete. CURRENTS BETWEEN BERMUDA AND THE WEST INDIES. All charts show in this region a prolongation of the equatorial drift toward the north, and a large mass of water passing north of the West Indies and joining the right side of the Gulf Stream. Notwithstanding this the Pilot Charts show that the derelicts Vin- cenzo Perrota, Ida Francis, Mary Douglass, and Rita were for several months in that vicinity without being drifted by that current. In the chart, "Drift of Bottle Papers" (No. ix), bottles Nos. 5, 88, 106, and 129, also show that if such a current exists at times it has not the permanence attributed to it by the charts. It can be said that the drifts of the floats are directly contrary to the current indicated on the charts. From all these observations we may conclude that the wind is the great cause for most of the surface movement of the sea. Its action causes the deviations from the displacement due to the tides and glacial discharges. TEMPERATURE OF THE SEA BETWEEN BORDEAUX AND LA PLATA. The study of the submarine temperatures has revealed the laws of the vertical circulation of waters. In examining the submarine isotherms along a meridian one is at once struck by the marked in- clination of these isotherms near shoals, the horizontality of the lines in temperate zones, and their rise toward the surface in warmer regions. It is difficult to explain why the isotherm of 7° to 10° C, after descending to a depth of 1,500 to 2,000 meters near the Canaries, 200 CHICAGO METEOROLOGICAL CONGRESS. should rise to nearly 200 or 300 meters below the surface, contrary to all the laws of gravity and to the movement of the waters by the surface winds. It must surely be due to the tropical evaporation and the necessity of replacing the equatorial waters that the vertical movement acts like a vast pump. If there is one place where this movement is specially emphasized, we believe such a place exists in the vicinity of Cape Blanco, Africa, near Arquin Bank. The observations of temperature of the mail steamers of the Mes- sageries Maritimes on their voyages between Bordeaux and the La Plata (see table below) show that the temperature between Lisbon and the Canaries increases regularly by 4° to 6° C, and that this increase augments most rapidly in November and least in March. Temperature of the sea between Bordeaux and the La Plata. Longitude h £• % % u ^ S west of Latitude. C3 a A • 3> >> s tp 0. 2 >• § 05 03 P. eS s "a 3 4> 4> "^ i. s < s l-» "-5 < m Zi Q , • 4 00 N. 45 00 12.0 II. 12.0 12.0 14-5 16.5 17.0 19.0 19.0 17.0 14-5 13-0 9 30 N. 42 30 13.0 12-3 12.5 12.2 13-4 15-6 16.4 17.9 17-4 14.0 13-4 13-0 9 30 N. 40 00 14-8 14.6 13-7 14. 1 14.6 16.5 16.9 18. 1 18.6 17-5 '§•7 14.0 10 00 N. 37 30 16.0 15-3 15.0 15.0 15-5 18.0 17.6 20.2 20.0 20.2 18.3 16.0 II 00 N. 35 00 18.0 16.3 16.0 16.0 17-5 18.7 19.8 21.7 21.2 21-3 19-5 18.0 12 30 N. 32 30 18.0 17.0 17-5 17.0 18.0 19-5 20.4 22.1 21.7 21.0 20.6 18.6 14 00 N. 30 00 18.5 17-5 17.7 17.6 19.0 20.0 20.7 22.2 22.7 22.0 21. 1 19.4 15 00 N. 27 30 18.6 17-5 18.5 18.5 19.8 20.5 21.0 22.8 24.0 22.5 22.1 20.0 i6 30 N. 25 00 18.5 18.0 19.0 19.6 19.8 20. 1 20.6 22.2 21-3 22.0 22.6 20.0 17 30 N. 22 30 17.9 17-5 18.0 19.0 19.2 18.9 .19-9 21-5 20.4 21.3 23.1 20.0 l8 00 N. 20 00 17-3 18.5 20.0 17.4 17-7 17-5 22.4 24-5 25.0 20.8 21.0 22.0 i8 00 N. 17 30 19.8 19.0 21-3 19.2 20.4 22.2 25.8 25-6 27.0 26.8 22.7 24.4 l8 00 N. 15 00 22.6 22. 1 20.5 20.5 23.2 25-4 27.0 27.4 27.2 29-5 26.4 25-1 19 00 N. 12 30 25-3 23-7 23.0 24.0 25- 1 27.8 26.3 27.1 28.0 28.2 26.9 25-8 21 00 N. 10 00 26.1 25-0 25.0 25-4 26.1 27.8 26.4 27.0 27.0 28.0 27-3 27.1 23 00 N. 7 30 26.9 27.0 26.0 27-5 27.1 27-3 26.3 27.4 27.0 26.6 27.0 27.4 24 30 N. 5 00 26.6 27.0 27.0 28.5 27-5 27.8 26.0 27.0 26.6 27.4 26.7 27-5 26 30 N. 2 30 26.4 27.0 27.8 26.7 28.0 28.5 26.0 25.0 25-4 26.7 26.2 26.7 28 00 00 25-9 26.7 27.0 26.1 27.7 28.0 25-4 25.0 25-4 25-9 26.0 26.1 29 30 S. 2 30 26.0 26.7 27-5 27-3 27.1 27.0 25-4 25.0 25-5 25-5 25-9 26.1 31 30 s. 5 00 26.4 26.5 27.9 27.4 27.8 26.5 25-7 25-9 25-6 25-2 25-7 26.4 33 00 8. 7 30 26.7 27.0 27.9 27.0 27-5 26.0 25-8 25-7 25-8 25-5 25-7 26.8 34 30 s. 10 00 26.9 27.0 27.6 27.0 27.1 25-8 25-3 25-3 25-3 25-4 25-5 26.7 36 00 s. 12 30 25.7 27.0 27-3 27.1 26.3 25-8 24.7 24.9 24-5 25-4 25-5 26.3 37 00 s. 15 00 26.4 26.6 27-3 26.7 25-7 25-5 24-5 24-5 24.0 23-5 25-4 26.3 38 00 s. 17 30 25-6 25.5 27.1 26.6 25-7 25.0 24.2 24.2 24-1 23-5 24. 8 25-9 39 00 s. 20 00 25-6 26.5 26.5 26.2 25-3 24-5 23.1 23-5 23-3 23-4 21.9 25-4 40 00 s. 22 30 23-3 21.0 24-5 23.0 21.8 20.0 20.0 20.5 20.2 19-3 20.4 21.8 45 00 s. 25 00 25-5 25-3 26.5 24-5 24.0 23-5 21.2 21. 1 21.0 21.2 22.9 23.6 47 00 s. 27 30 24-5 25-5 27.0 24.0 24.0 18.3 20.6 20. 1 20.3 21.0 22.2 22.8 49 00 s. 30 00 24.0 25-0 25.0 22.3 22.0 16.5 18.6 18. 1 18.9 18.7 21. 1 21.0 51 30 8. 32 30 22.4 23-5 23.0 20.8 20.0 13-5 14.2 15- 1 16. I 17.4 19.4 20.5 54 00 S. 35 00 19-5 20.5 19-5 18.8 17-5 12.0 II. 6 II. 13-4 15- 16.4 19.4 From the Canaries to the Arquin Bank the temperature falls from 2° to 2^° C. from April to November. The fall is less marked but is found also during the winter months. The center of the thermal depression oscillates between N. 20° and N. 22°, it runs near the coast on the level of the peninsula of Cape Verde, and it is deflected at the time the currents change direction. From the Arquin Bank to Dakar there is a sudden thermal rise of 8° to 9° C. in September and October; the rise is less in March and April. The sharp bend in the isotherms has also been established by Plate X, in the shears 1879 and 1880. Sauirewx. y/cTttk 3outh Latitudes. ^j: IS W S S 70 rS 20 25 30 35 1 ^ 1 ZS — ~ I..I 1 II 1 1 1 y' 1 r 1 ^ ~s sU- J 1 1 1 1 1 1 ^... , 1 1 1 1 II ll 1 \ K is' — '^ 1 1 -l ll 1 1 1 1 1 1 1 ^ I 1 .— 1 1 1 1 1 1 1 JS 1 1 1 1 1 1 1 1 1 25° 1 — -1 - "^ -rr.^ 1 1 J....I i 1 1 II 1 1 1 1 1 1 ■*sl \- •••I |i i 1 I r- \ 1 1 1 II 1 1 1 ■"■•^ 22° SO' is' r ^ "N: 1 I 1 hT 1 H^ A. 1 4. l| 1 1 T| ll 1 \., 1 1 1 1 1 1 |i 1 1 is' — v 1 i s •■■'^ -.^^ U- 1 1 1 1 / iT 1 X 'k- rl jl 1 \\ ll 1 1 \ li 1 II 1 1 1 ll ! 1 76" :; ^ \\ 1 t 1 In il 1 1 1 1 1 1! 1 1 L 1 1 1 1 i i , , , , , ,, i The trace iesuU» of ob-iervatio Temperature of the sea from the Gironde to the La Plata River. Monthly means dcducod from observatioQS. 1 the years 1&79 and iSSc. Plate X Sauireux. 3 JTorth Latitudes Suufi Latitudes. 4^ 40 3S JO &r :o IS w so s K ts zo zs 30 3S «;»« 0. J^orth Latitudes jSouthLatUudes \ ■fS 40 3i X ZS 20 71 to s S 10 rS 20 2S so ss II is' 1 1 1 1 ^ -«s, .•^ 1 L^ ^ ^ is' 10' !S° I 1 1 / — . ■^-^ II- ■ 1- II 1 .y 1 1 1 v V 1 1 1 1 1 ll ■-H \ 1 1 1 ^ fe i / ir "T itl- .1 j K ^ ! ^ / ll 1 !i 1 J:: ^ 1 1 1 1! 1 1 111 r^ V k^ 1 1 1 1 1 1 1 h 1 1 1 1 I 1 1 ll 1 -ti- ll 1 N 1 2/ 20' ! 1 1 1 1 1 II ^■ 1 2S' 1 1 1 1 "^ 1 1 .14 r 1 ll 1 /■■■ ■i "~^ /" 1 1 ■ 1 1 1 ^- 1 1 1 1 \ 1 ^ 1 ]^ ■^ J< 1 1 1 ■^ nI- ■ 1 1 ^ J^ ■"^ r^- 1 1 1 \ 1 r 1 1 1 1 1 1 1 1 1 1^ s -K 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ■\ ■id' 1 1 1 i 4^ 1 is' 10' 1 1 1 1 1 1 -y- — .^ 1 i 1 1 II 1 -i^ ■^^ 1 1 i 1 1 / i! 1 1 1 \. 1 1... .^ i^ X 1 1 1 1 "n ^kll 1 1 ^ ¥ M 1 1 1 1 ll 1 1 s^ 1 1 1 1 ll 1 1 h \ ^ ■y 1 1 ■1 1 1 1 1 !! ' 1 1 1 1 1 1 1 1 1 1 1 1 1 1 -N a" 1 1 ^ ^ ^ ^4- ■*^ ^il 1 1 zs° zo' is' 1 1 1 1 ■f ^ <^ %. li 1 1 1 1 1 / |! 1 1 ^ 1- N 1 ■\ ^ T -vi 1 ■ it 1 i 1 1 ^ ■^ s l/ 1 1 1 ■s V > 1 1 1 il 1 111!" \-., jJ \ 1 l| 1 1 r 1 1 1 1 1 1 11 1 is' 1 1 1 1 ^ 1 ^ 1 5i 2i' 20° 1 1 1 1 ^ -^ 14 1 1 1 1 ■■ 1 ..;/ -::'■■. 1 1 1 Fl ^ 1 1 •r 4 / 1 1 yT N 4 tH^. 1 ■^ ■^ '/ 1 1 II 1 s I..- '/■ 1 1 1 jl 1 1 \ ^ 1 1 1 1 1 1 1 1! 1 y 1 1 1 II 1 II 1 us' zr' ze' is' 1 r 1 1 /^ >^ 1 1 g ll 1 1 1 NO 1 zs' zo' rs' i j 1 1 1 .■^ ^ ^ _^ ti- 1 h 1 1 1 .\- 1 / 1 1 i w, Ki- I 1 1 i r T m. -f- ^ -^ 1 ■ 1 f 1 1 1 K 1 '/ <- 1 ■ 1 ll 1 ll 1 ■^ 1 1 1 1 1 1 1 ll II 1 N ir-^ I ■ 1 1 1 1 1 1 1 1 1 1 1 ^ i ! i i ii i §! 1 I II 1 U M. li ll M 1 i i 1 8 1 §' i L § 1^ S ^ !^ ,§'1 -a #-^1 1 s NORTH ATLANTIC CURRENTS. 201 the exploring expedition of the Talisiiian. On this vessel it was ob- served that the density of the surface waters was only 1,024.8 or 3.0 less than that of neighboring waters, and also that this diminution in the saltness exists in deep layers when the temperature is as low as 7° C. This low density accompanied by low temperature in this warm region proves decidedly the polar source of these waters and their rise to the surface. The color of this water is also different, being green while the neighboring trade-wind water is blue. The depths reach 2,200 meters. The observations on the mail steamers show another point of thermal depression and rise to the surface. This is near Cape Frio. In the warm season when the rainfall is most marked the thermal depression is about 3° or 4° C. FROM BORDEAUX TO NEW YORK. The Bordelaise mail steamers plying between Bordeaux and New York have willingly given me the results of their observations for several years, 1882 to 1887. The route of these steamers crosses the fortieth meridian in N. 47° 30' and passes the southern extremity of the Banks of Newfoundland. In the curve of these isotherms one is at once struck by their ir- regularities between the fortieth meridian and New York, and by their absolute uniformity between that and the mouth of the Gironde. Temperature of the sea from Bordeaux to New York. £ u 2 u z ■3 V S s a 03 OS s ■§ 1 0. < a) a a >-> 1-5 3 3 < J3 E «> 0. C .2 £ ' ' 46 00 8 00 12-5 11-5 II-5 13.0 13-5 16.0 17-5 18.0 18.0 16.0 14.0 13-0 46 00 13 00 12.5 12.0 12.0 13.0 13-5 16.0 17-5 18.0 18.0 16.0 14.0 13- 47 00 18 00 12-5 12.0 12.5 13-0 13-5 i6.o 17-5 18.0 18.0 16.0 14.0 13-0 47 00 23 00 13.0 12-5 12.5 13-5 14.0 16.0 17-5 iS.o 18.5 16. 1 14-5 13-5 47 00 28 00 13-5 12-5 13.0 13-5 14.0 15-5 18.0 19.0 19.0 16.5 13-5 13-5 47 00 33 00 14.0 12-5 13.0 14.0 14.0 i5.o 18.0 20.0 20.0 17.0 14.0 14.0 46 00 38 00 14.0 12-5 13-0 15.0 14.0 18.0 18.0 20.0 20.0 18.0 14.0 14.0 45 0° 43 00 14.0 14.0 14.0 15.0 14.0 20.0 21.0 23.0 23.0 20.0 16.0 16.0 44 00 48 00 10. 14-5 15.0 8.0 8.0 15.0 16.0 18.0 15-0 11. II.O 10. Grand Bank 50 00 — I.O 0.0 0.0 1.0 6.0 8.0 11. 14.0 II. 8.0 6.0 4.0 43 00 53 00 5-0 5-0 10. 13.0 16.0 21.0 19.0 21.0 17.0 16.0 10. 9.0 42 00 58 00 10. 15.0 15.0 17.0 17.0 21.0 22.0 24.0 21.0 21. 17.0 17.0 41 00 63 00 8.0 II. 13.0 15-0 15-0 20.0 22.0 24.0 22.0 25.0 17.0 16.0 41 00 68 00 6.0 7.0 6.0 5-0 9.0 14.0 18.0 21.0 19.0 18.0 II. 10. 40 00 73 00 4.0 4.0 4.0 5-0 7.0 II. 19.0 19.0 18.0 16.0 13-0 II. The curve . 12.0 II. II. 13-0 14.0 17.0 19.0 20.0 19.0 17.0 15-0 13-0 Therefore, these thermal differences near the American coast prove the sources of the waters to be different, while the main currents that reach the European shores are more stationary and are pushed and mixed by the winds. 202 CHICAGO METEOROLOGICAL CONGRESS. BAY OF BISCAY. In a region so contracted there can not be great thermal diflferences. Such small differences as exist are evidences of the movement of the waters in that great bay. We have the observations of the mail steamers, from time to time, for a distance of about 50 miles from the mouth of the Gironde to Cape Ortegal. A study of the lines of isotherms, month by month, shows that in the months of June, July, and August there is, along the fourth meridian west of Greenwich, a mass of water about 100 miles wide, whose temperature is about 2° or 3° C. higher than that of the French coast waters, and that from this point to Cape Ortegal the temperature gradually falls in the summer months until it is 2° C. lower than that of the coast waters. (See tables and plate.) This state of things indicates that the Rennell Current does not exist during the summer months as stated on the chart. To supply this mass of warm water along the fourth meridian, one can only find an oceanic source, and to furnish the cold waters of Cape Orte- gal it can only be ascribed to the melting ice of the mountains on the north coast of Spain. These flow along the coast from east to west until they meet the oceanic waters at Cape Finisterre. During the months of November and December the temperature of the water is higher at Cape Ortegal than near the mouth of the Gironde. These are the months of the west winds on the coast of Portugal. These winds at the same time blow from the northwest on the French coast and suffice to explain the thermal difference. These observations of the temperature of the sea clearly show that the waters of the Bay of Biscay are differently affected in summer and winter. During the fine season, in a period of comparative calms, in the Bay the surface Avaters are rather stationary, and are heated more than the coast waters by the influence of the winds and tides. The experiments with drifting bottles show that in the summer months that the coast waters are subject to a slight movement. The Rennell Current has not the permanence nor the dimensions with which it is credited. In the Bay of Biscay there are variable coast currents depending upon the force and direction of the winds. The conclusion that may be drawn from this study is that all the ocean currents marked on the charts are more or less deflected by the winds, and that even the most constant currents such as the Equa- torial Currents, the Gulf Stream, and the Labrador Current are sub- ject to their influence. The branch currents which wash the shores of western Europe and Africa are even more sensitive to the winds. The currents on charts should be accepted as the general condition, but it must always be Ijorne in mind that the wind dominates and is the grand factor in surface movements. NORTH ATLANTIC CURRENTS, 203 The changes in the temperature and saltness of the sea are also a principal cause of the movements of the waters, especially at certain depth. The effects of melting ice and fluvial discharges may be seen when the weather is calm, but numerous facts have shown that under these conditions the intermingling of the waters is slow without the agency of the wind. It must also be admitted that there has been too much generalizing with conditions which in reality are only more or less frequent in certain seasons and not permanent. In making averages of observa- tions one may get impressions which are not correct. Thus, in charts of mean barometer pressure and in isotherms in inter-tropical re- gions there is a fact which approaches the truth, since in these regions the extreme variations are only a few millimeters, but north of N. 40° what signification can be given to a barometer normal when it is known that in a few hours there may be changes of 75 mm., and that during an anticyclone the barometer remains at 785 for a week in a region where the normal is in fact 750 mm. The same in regard to the isotherms. The normal mean applies very well to inter-tropical regions and in the Atlantic east of the fortieth meridian, but in the neighborhood of the Banks of Newfoundland what will represent the conditions normally when the ice fields and icebergs appear and cover one-fourth of the Atlantic and then for another season fail to appear at all. What more exact information can be obtained than is given on the Pilot Charts? There we see the tracks of depressions, the frequency of storms, the direction of currents, the direction of winds and per- centage of calms which prevail in the Atlantic for the current month. If it were possible to add to the text of the Pilot Charts the disposi- tion of the anticyclones and their interdependence in regard to the high pressure on the Sargasso Sea, one would see at a glance of the eye the actual state of affairs from the barometric indication. Temperature of the water in the Bay of Biscay from the mouth of the Gironde to Cape Finisterre {degrees Centigrade). Longitude. as S a * ■-5 s 03 'u 0. < - a s >-5 3 1 < s