Popular Science Monthly/Volume 32/December 1887/John Jacob Baeyer

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WHEN Frederick the Great, June 22, 1740, wrote, "In this country every man must get to heaven his own way," there were many sturdy Germans who were glad to embrace the opportunity to turn aside from the route to which the beliefs of their ancestors restricted them. But they did not wish to be alone upon the unknown sea into which their independence had launched them; every one felt the need of that encouragement which comes from the association of those whose aims and methods are the same. To secure this, the gracious sovereign allowed colonies to be formed of those of like faith and order. One of these colonies was Müggelsheim, about fourteen miles southeast of Berlin. Among the founders of this village there was a "faithful follower" who came from Odernheim seeking that religious sympathy which was here vouchsafed. This pilgrim sat as magistrate in the new settlement, while another coming from Mainz was the school-teacher; these two became connected by the former's son marrying the latter's daughter. On the 5th of November, 1794, this couple rejoiced over the birth of a son—Johan Jacob Baeyer. The first few years of the lad were uneventful; he watched the geese, herded the cattle, and laid, in healthful exercise, the foundation for a vigorous, active life. He was sent to the village school until he was thirteen years old. Here the pupil's talents were proudly observed and duly fostered by the teacher, his grandfather, who noticed especially the wonderful memory of the youth.

This capability seems to have been the moving cause that prompted the parents to give Baeyer the advantages of a better course of instruction. They sought to find this in the person of Gronau, the pastor in the neighboring town, Köpenick. Here he remained three years, going thence to the gymnasium in Joachimsthal, where he entered the fourth class.

Before completing the course here, the breaking out of the War of 1813 fired him with a thirst for military experience, which he obtained as a volunteer in the Third East Prussian Infantry, serving until the declaration of peace in 1814, He then returned to his gymnasium studies, to be again interrupted by the outbreak in 1815. The repeated inclinations to be a soldier were gratified by again enlisting in the army, this time as an officer in the Fourth Rhine militia. This life had a charm for him; so, at the close of the war, he attended the military school at Coblenz, and in 1821, through the intervention of General von Müffling, who had become acquainted with Baeyer's predilection for geodetic work, he was detailed to the general staff.

It was at this time that Von Müffling was engaged upon the arc of longitude extending from Dunkirk, the extremity of the French arc of latitude, to Seeberg. In this work Baeyer assisted, especially in the computations, receiving in return his chief's ardent thanks in the preliminary report published in the "Astronomische Nachrichten," 1822, No. 27.

The year 1822 was perhaps a pivotal year to Baeyer. Just while comparing the life of a soldier with that of a scientist, at a time when be had obtained a place of honor in the military service, and had also been publicly thanked by a distinguished man for scientific work, he met Alexander von Humboldt and Bessel. The former was planning a second trip around the world for the purpose of collecting items of interest, and thought that he had found in this clever, energetic officer, now in his twenty-seventh year, the person to place in charge. The proposition was formally made, and so seriously considered that by way of preparation Baeyer attended the lectures of Weiss on mineralogy and geognosy during the two following years. For certain reasons the plan fell short of consummation, but Humboldt's friendship and example were always great incentives to his youthful friend. Bessel also followed the career of Baeyer with interest, and saw in later years that his talents and skill were of such character as to bring them together as co-workers, assisting one another. He was promoted to first lieutenant in 1823, and in the following year he was one of a party that made a survey of the Suwarrow route over the Alps, during which he ascertained, by means of a barometer, the altitudes of more than a hundred stations. Poggendorff paid him the compliment of discussing one of these determinations in "Annalen der Physic und Chemie," vol. ii, 1825, pp. 109-112.

In 1825 he was appointed a member of the faculty of the military school at Berlin, at first teaching pure and afterward applied mathematics; and from 1832 to 1857 he had charge of the department of geodesy, lecturing on the theory during the winter and working at it practically during the summer months. It was at the very beginning of his course in geodesy that Bessel secured his assistance in that monumental work, the degree-measurement in East Prussia, the results of which were published in 1838 under their joint authorship. While Bessel is known as the leading spirit in this undertaking, Baeyer's skill in handling instruments, his interest in base-measuring, and his efficiency in recognizance, contributed no little to its success. The accuracy, watchfulness, and painstaking detail of the enthusiastic officer stimulated Bessel to do his best; and this best so impressed itself upon Baeyer that posterity has become his debtor for having handed down and improved the methods of his honored master.

Before completing this work he received another call, this time through the intercession of Humboldt. The gravity experiments made by Bessel at the Berlin Observatory could not be of any especial value, owing to the uncertainty of the altitude of Berlin above sea level, which at that time was known only from barometric observations. Trigonometric leveling was now coming into great favor, especially when the precaution was taken to make reciprocal zenith-distance observations. So, when it was ordered by the general staff in 1835 that the altitude of Berlin above the mean sea-level at Swinemünde should be determined, the execution of the order fell upon Baeyer, who, with the assistance of Bartram, finished it during the same summer. The result obtained differs only by a few decimetres from that recently found by a line of geodesic levels. At Swinemünde a permanent mark was established, and annually for several years the height of this above mean tide was measured; these records many years later disproved the theory that the Baltic Sea had been subjected to a great change during the first half of this century in height.

He was placed in charge of the survey of the coast of the Baltic Sea in 1837, the triangulation for which he joined to that of the degree-measurement chain. This was carried up to annexation with the Danish work. In 1843 he was made chief of the trigonometric branch of the general staff, when he continued his great coast-survey, bringing the triangulation from Stettin to Berlin, and also connecting with Müffling's chain. These nets, together with Tranchot's and others, executed earlier for the purpose, formed the basis for the land survey of the Prussian states. Baeyer thought that work done at different times and by various persons should be brought into harmony by all resting upon the same basis; to which end he measured two bases, one at Berlin in 1846 and the other at Bonn in 1847. The results of the former were announced in 1849, but the necessity for reobserving some of the adjacent angles delayed the publication regarding the latter until 1876.

The coast-triangulation was so well executed that it was deemed advisable to utilize it in degree determinations by connecting it with the Russian system. This was done by Baeyer and General von Tenner from 1850 to 1851, with every precaution then known, including remeasurement of bases and a careful comparison of the standards. The difference in the total length of sixteen sides they bad in common was only 0·505 metre.

His work occasionally overstepped the boundary-lines, establishing stations in other countries; these served as germs of larger growth, in many cases afterward nurtured by Baeyer's own hands. His advice was so frequently solicited, and when followed the results were so praised, as to induce him to prepare and submit to the Prussian Minister of War a memoir giving in detail a method for making a good map of Prussia. The principal improvement suggested, and afterward adopted, was in the more extensive use of triangulation, fixing in this way every point of importance, leaving but little intermediate ground to be located graphically.

His tastes for geodetic work were soon to be more fully gratified. Having passed rapidly through the lower grades, he was in 1858 made a lieutenant-general, and retired. It seems as though this eventual freedom to follow his own inclinations had in early life impressed itself upon him, for we find that in his work when he came to a station that at some future time might be of geodetic importance, he bestowed upon it especial care, supplementing the usual series of observations with those that would obviate the necessity of reoccupying it. Before indecision as to what should next receive his attention had become wearisome, Struve secured his co-operation in extending the Russian arc of longitude along the fiftieth parallel into Prussia. This he had in hand during 1858, making only astronomic observations, as it was his purpose to use the triangulation previously made. After several interruptions, owing to the withdrawal of the officers detailed to assist, he decided to make Rauenberg his central point, and to determine the direction of the chain by the azimuth of the line from this station to the Marien-Dom in Berlin—a line which now orients the entire Prussian survey.

The association with Müffling, Bessel, and Struve gave to Baeyer the incentive to connect and unify the excellent geodetic work of middle Europe; geographically, his native land occupied a favored place, and his government fostered the scheme. In 1861 the plan for a middle European degree-measurement, drawn up by Baeyer and sanctioned by the Minister of War, was approved by the emperor. At once the co-operation of the states that were to participate was requested, and to show the importance of such an undertaking, he published a pamphlet on the "Size and Figure of the Earth," giving an account of the geodetic work up to that time, and outlining what remained to be done under the auspices of the proposed commission. The permanent commission held its first session in Berlin in 1864, with Baeyer as president—a young organization with a leader aged seventy. The Prussian Geodetic Institute, established in 1809, was also placed under the direction of Baeyer. In both institutions he took an active part, not only in the official routine, but in making astronomic observations and comparing standards until 1874.

Under his instructions, the observations of Bessel at Königsberg in 1826, and Schumacher at Guldenstein in 1829, with the pendulum, were repeated, to see if the length of the seconds pendulum had retained the same relation to the toise. No change was found, showing that no alteration had taken place in the toise from molecular action, as had been feared.

As a careful observer, his attention was always directed toward possible sources of error in his work, especially toward atmospheric refraction, and, as connected with it, the physics of the atmosphere. He utilized all data obtainable from leveling for deducing a formula in which the coefficient of refraction could be given as a function of time or meteorologic conditions. The elaborated formula was published in 1840, and with revisions in 1860. He also conceived the application of the converse principle, from which observations for refraction would reveal the condition of the atmosphere. In addition to his purely practical discussions he wrote several articles upon winds, and the solutions of spheroidal triangles. He was an active or honorary member of the leading scientific societies at home and abroad; many decorations were conferred upon him by various crowned heads. On the 8th of January, 1883, he celebrated the seventieth anniversary of his connection with scientific work. And on the 6th of November of the following year, in honor of his ninetieth birthday, the Academy of Sciences of Berlin sent a deputation to carry their congratulations and good wishes; the Geodetic Institute presented him with a bust of himself, and the emperor and crown prince sent their compliments.

He brought his interest in scientific work down to his death-bed, on which, two days before his end, he was listening to the report of operations that he had shortly before planned and started. On September 10, 1885, the inflammation of the lungs, from which he had suffered only a few days, proved fatal.

Note.—While preparing this, I received from Dr. Helmert, Baeyer's successor as President of the Prussian Geodetic Institute, his sketch of the scientific labors of Baeyer, an excerpt from "Vierteljahrsschrift der Astronomische Gesellschaft," Band 2, Heft 1, to which I am indebted for many facts of interest. A list of Baeyer's writings can be found in "Literatur der praktischen und theoretischcn Gradmessungs-Arbeiten," an appendix to the report of the Permanent Commission for 1881. A revised edition of this valuable publication will appear in connection with the report for 1886.