Popular Science Monthly/Volume 39/May 1891/Sketch of Niels H. C. Hoffmeyer
|SKETCH OF NIELS H. C. HOFFMEYER.|
TO Captain Niels Hoffmeyer meteorology owes some of its most important developments, and particularly the organization of what may be called the first ocean weather service.
Niels Henrik Cordulus Hoffmeyer was born in Copenhagen, Denmark, June 3, 1836, the son of Colonel A. B. Hoffmeyer, and died in Copenhagen, February 16, 1884. It was at first intended that he should pursue a professional career, and his studies were begun with a view to that end; but the plan of his education was changed and he was sent to the military academy. He became an officer when eighteen years old, and was given an appointment in the artillery service when his course had been completed. His military effectiveness was impaired by a disposition to rheumatic fever, from which he had suffered in early youth, so that after having been engaged in the Schleswig-Holstein War he was prostrated again in February, 1861; and when the army was reduced at the close of that year he was placed on the retired list. Having spent a few months after his recovery in recruiting at the baths, in 1865 he visited France and spent a year in studying the methods and operations of the iron-foundries at Paris and Nantes. Returning to Denmark, he busied himself in furthering the establishment of similar works at Christiansholm, and while thus engaged was appointed to a post in the War Department and to be a captain of militia in Copenhagen.
His sojourn in France was contemporaneous with, Leverrier's activity in meteorological research and experiments, under the impulse of which the principles that distinguish the modern methods in that science were largely developed. The publication of this student's daily weather map of all Europe in the Bulletin International had been begun only two years before. Hoffmeyer's attention was directed to the subject, and he entered into the study of it with an ardor that greatly redounded to the gain of science. He carried his newly aroused enthusiasm in this work into his war office, where he continued his studies; and when the Meteorological Institute was established in 1872 he was made its director. "There could scarcely be a more fortunate appointment," says Nature, to whose various articles we are chiefly indebted for the materials of this sketch, "for Hoffmeyer was gifted not only with unusual energy, but also with a very pleasant manner, so that he made friends for the new office and for its work wherever he went."
"It was from a singularly clear and firm apprehension of the characteristics of modern meteorology," Nature says in another article, "and an unflinching application of them to the facts of observation, that Captain Hoffmeyer has left his mark on the science—these principles being the relations of winds, temperature, and rainfall to the distribution of atmospheric pressure. In working out the weather problem of Europe, no country occupies a more splendid position for the observation of the required data than does Denmark with its dependencies of Faroe, Iceland, and Greenland. Denmark was slow to occupy the field, nothing having been done by the Danish Government prior to Hoffmeyer s appointment as Director of the Meteorological Institute. In a short time these important regions were represented by ' stations in Greenland, Iceland, and Faroe. The meteorology of Denmark proper was pushed forward with great vigor."
Of this work Mr. E. Ersley said, in an address to the Danish Geographical Society on the occasion of Hoffmeyer's death: "Hoffmeyer saw very early and clearly that our little country was of great importance in meteorology; for it lies between two seas, the North Sea and the Baltic, and exhibits a peculiar division of land and water, while storms sometimes originate in its precincts. For that reason we ought to endeavor to establish as many observing stations as possible. His efforts to accomplish this were embarrassed by the scantiness of the means allowed the Institute. But his practical sense came to his help, and he engaged a large number of private persons to erect stations where daily observations might be taken—at most of them without pay, and also at many without instruments except such as were privately furnished. In this way our country has been planted with not less than two hundred minor meteorological stations. He also saw that our further possessions, which were as good as unknown meteorologically, might be made members of extreme importance in the series of weather observations. He therefore secured meteorological stations in them—six in the Faroes, twenty-three in Iceland, and fourteen in Greenland, besides using his persuasive conversational powers to induce many ship-captains to take instruments on their voyages, especially on those to Iceland and Greenland."
Hoffmeyer labored at the Institute twelve years uninterruptedly for the advancement of meteorology, and, although suffering much in his later years from the effects of his rheumatic fever on his heart, with irrepressible energy.
In 1873 Hoffmeyer began the publication of the monthly Meteorological Bulletin of the North, and shortly afterward the issue of a daily meteorological chart for his own country, Norway, Sweden, and northwest Russia. To this chart was added an explanation for the use of subscribers. The work was found valuable by English meteorologists, because it supplemented their own daily weather charts and those of the Bulletin International, for a district extending from 63° east to 60° west longitude, and from 30° to 75° north latitude, whence accurate information was seldom obtainable by telegraph in western Europe. Although these charts did not at first repay the outlay made upon them, they were so well received by the meteorologists of Europe as to encourage their continuance. Their scope was enlarged in 1875, in accordance with the advice of the directors of various central institutions, so as to embrace a more considerable part of the globe, and give some idea of the distribution of temperature. Mercator's projection was discarded, in order to avoid the exaggerations of dimensions in northern regions; and other improvements in detail were made. These synoptical charts, giving observations made three times a day in Denmark, Faroe, Iceland, and Greenland, were continued for more than three years, or till November, 1876, at Captain Hoffmeyer's personal expense. Arrangements had been made in the summer of 1883 to resume the publication, in conjunction with Neumayer, and the first sheets of the new series were printed on the day after that of Hoffmeyer's death.
Captain Hoffmeyer was a worker in meteorology rather than a writer of papers and books on the subject. The service that he did is best seen in the organization of a system of stations at intervals across the ocean wherever his country had jurisdiction; in the conception of his synoptical charts; in the regular publication of the Meteorological Bulletin of Denmark, described in Nature as in several respects among the best that reached it; and in his co-operation in the formation and movement of the International Meteorological Congress. He was one of the secretaries of the meeting at Rome in 1876; and was a member, appointed by the Vienna Congress of 1873, and a secretary of the Conference for Maritime Meteorology that met in London in 1874. He also made some valuable literary contributions to the science. Among these are his papers on the Greenland Foehn, 1877, and on the distribution of atmospheric pressure in winter over the North Atlantic, and its influence on the climate of Europe, 1878. The former of the papers related to the sudden changes of temperature which mark the winter climate of Greenland, under which the mean temperatures of that season sometimes vary almost as much as 23° C. in different years, and Upernavik is sometimes as warm during the darkness of the polar night as the south of France. Sudden and sharp changes often occur several times in the course of the same month; and the rises always stand in connection with a veering of the wind to southeast and east. The phenomenon of a warm wind blowing from an interior which is covered with snow and ice has then to be accounted for. The older authors, to explain the paradox, resorted to imaginary volcanoes in action, or to the hypothesis of a comparatively mild climate in the interior—which it would be impossible to sustain on meteorological grounds; for the interior of every continent must necessarily be colder, by the effect of radiation, than the coast, where the sea is an ameliorating factor. Another attempted explanation depended on the Gulf Stream, whence the southeast winds were supposed to blow warm; but this, though reasonable, was insufficient.
When Hoffmeyer's attention was directed to these facts, his thoughts turned to other regions of the earth, and finally to the Foehn of the northern slopes of the Alps, where "a stormy southerly wind sometimes begins to blow very suddenly, which, from the snow-covered summits, hurls itself with irresistible force through the valleys which lead toward the north, and throws the Alpine lakes into frightful commotion. This wind, which is named Foehn, has, although it comes from a snowy region, an unusual warmth and dryness." At the same time that the southerly wind is found as an unusually warm and dry Foehn on the northern side of the Alps, a humid sirocco, generally accompanied by an enormous fall of snow, is blowing on the southern slopes of the mountains. This phenomenon had been accounted for by Dr. Hann, of Vienna, as the effect of the condensation, coming down from the tops of the mountains, of the air which had been cooled and deprived of its moisture by precipitation, in ascending the opposite slopes. Dr. Hann's calculations showed that the temperature of a south wind, lowered half a degree for every hundred metres of ascent, was raised one degree for every hundred metres of descent. These phenomena repeat themselves in Greenland. The author sketched in detail a Foehn period which lasted from eighteen to twenty days in the end of November and beginning of December, 1875, when Jakobshavn was for eight days warmer than north Italy. Unfortunately, direct observations from the uninhabited east coast of Greenland and the nearest parts of the Atlantic were wanting; but it was possible to show that during the same period a strong southeast wind blew from the sea over the land; for, according to the Buys Ballot law, the wind always blows so that it has the greater pressure of the atmosphere on its right, and, the more unequally the pressure is distributed, the greater is the velocity of the wind. Just during the eight days of heat at Jakobshavn, the barometer was much higher in Iceland than at Davis Strait. Over the tract lying between these places there had thus prevailed a strong southeast wind.
In the other paper, which is declared to be "an original and highly important contribution to science, whether regard be had to the method of investigation or to the results" Hoffmeyer showed that Greenland and Iceland exert a powerful influence on the distribution of atmospheric pressure not hitherto properlyrecognized, resulting in the mean minimum of pressure being localized distinctly in the south of Iceland—a minimum accompanied by two subordinate minima, one in Davis Strait and the other in the Arctic Ocean, midway between Jan Mayen and the Lofoden Islands. It was made plain, from typical charts giving the mean of four winter months, that one or the other of these minima plays the chief part, the other two being, for the time, subordinate; and that, according as one or the other of the minima predominates, so is the character determined, as regards mildness or severity, of the weather of the winter of the regions surrounding the north Atlantic.
An illustration of his method of working is afforded by the explanation he published of the causes of the cold weather that prevailed over Europe in May, 1874. He showed that a maximum of pressure had prevailed over northwestern and western Europe, "stretching like a great screen" between the Atlantic and central Europe, from Spitzbergen almost to Algiers, while the minimum came partly from the arctic seas, and partly from the western Mediterranean, with gradients steep toward the north and west, Such a distribution of pressure must give rise to a cold polar stream flowing over the greater part of Europe. In Vienna the cold was greatest between the 16th and the 18th, and then the high pressure began to travel eastward, with the production of a great change, so that soon the pressure was lowest in the very district where a few days before the maximum had existed; and the temperature rose. A similar cycle of phenomena occurred in the next month. The author observed in this paper that areas of high pressure are much more quiet and longer lasting than minima, which travel rapidly, change their shapes, and throw off secondary disturbances.
The Meteorological Bulletin had become by the time of Hoffmeyer's death a very important and complete publication. In January, 1884, the number contained pressure results for thirteen stations, temperature for one hundred and nine stations, and rainfalls and other forms of precipitation for one hundred and fiftynine stations; and these results were graphically shown on four maps, accompanied with a full descriptive letterpress—one map giving the isobars for the month, another the isothermals, and on the same map the mean temperature of each of the one hundred and nine stations; a third map, the miminum temperature at each of the stations; while the fourth map gave isohyetal lines, showing the rainfall, with the amount at each of the one hundred and fifty-nine stations entered in plain figures.
The most important results deduced by Hoffmeyer from his maps were contained in his pamphlet, Étude sur les Tempétes de l'Atlantique Septentrional et project d'un Service Télégraphique International relatif à cet Océan, Copenhagen, 1880 (Study of the Storms of the Northern Atlantic, and Project for an International Telegraphic Service relative to that Ocean); "and up to the very last" says Nature, "he never ceased to use his utmost efforts for the establishment of a meteorological telegraphic service with America, via the Faroes and Iceland"
Besides enjoying the honors and positions already named, Hoffmeyer was Secretary of the International Polar Commission; an honorary member of the Royal Meteorological Society of London; and Danish Commissioner to the Fisheries Exhibition, in London, in the summer of 1883. While performing the duties of the last position, he complained of great weakness of the heart. He had suffered from occasional attacks of rheumatic fever; was ill for some time in December of the same year; and was finally attacked in January, 1884. He continued to work at the duties of his position, whenever he was able, till the last. His biographer, in Nature, says that, "to all who knew him, the memory of his eager readiness to assist fellow-workers, the urbanity of his manner, his joyous nature, and the unusual warmth of his friendship, can not but awaken the keenest feelings of regret for his early death."