REPSOLD, JOHANN GEORG

(b. Wremen, near Bremerhaven, Germany, 19 September 1770; d. Hamburg, 14 January 1830)

instrument making.

The family name derives from that of a manor house, Hrepesholt, in Friesland, which is first recorded in connection with the establishment of a monastery in 983. In Johann Georg, Adolf, and Johann Adolf Repsold, the family produced three generations of outstanding designers and builders of astronomical instruments.

The first of these. Johann Georg Repsold, was the third child and eldest son of a minister, and was himself intended for a career in theology. He was more interested in technology, however, and, after attending the Latin school at Stade, in 1788 went to Cuxhaven to study mathematics and technical drawing with Reinhard Woltmann, a pilot on the Elbe River who later became director of the Hamburg waterworks. Repsold succeeded Woltmann as river pilot in 1795; in 1799 he married Eleonore Scharff, the daughter of a captain (Spritzenmeister) of the Hamburg fire department, which post he himself assumed in the same year.

At about the same time, Johann Georg Repsold met the Swiss physicist and astronomer Johann Kaspar Horner, who was engaged in measuring the estuaries of the Weser, Elbe, and Eider rivers, and discovered a mutual interest in the design of astronomical instruments. By 1800 Repsold had set up his own machine shop, and in 1803 he constructed for Horner a portable transit instrument, which the latter took with him on a world cruise with Adam Krusenstern. During this period he also made a meridian circle that Gauss purehased in 1815 for the Göttingen observatory; Resold installed the instruments in it. These alterations, together with some later ones and with some new techniques for smelting optical glass, resulted in part from the technical correspondence that Repsold maintained with Gauss between 1807 and 1821. Gauss also suggested that European surveying methods might be improved through the use of trigonometric signals obtained from reflected sunlight, and for this purpose he built a heliotrope; in 1821 Repsold constructed one of these instruments, according to his own design, and it was subsequently used with considerable success by Heinrich Christian Schumacher.

Concomitant with his scientific work, Johann Georg Repsold continued to serve in the Hamburg fire department, having been appointed Oberspritzen-meister in 1808. On 14 January 1830, while directing his men in putting out a major fire, he was struck by a falling beam and fatally injured. He had, during his life, received a number of German and foreign honors. and following his death the Patriotic Society of Hamburg placed a bronze bust of him near the new Hamburg state astronomical observatory, which had itself been established in large part through Repsold’s efforts.

Johann Georg Repsold was succeeded as fire captain by his third son, Adolf Repsold, who had served an apprenticeship in his father’s workshop and, with his brother Georg, assumed direction of the family instrument business, renamed A. and G. Repsold. Adolf Repsold’s first commissions were for a small transit instrument for Bessel and for a similar nine-foot (2.74-meter) instrument for the Edinburgh observatory, which was installed in 1831, the same year in which Repsold also designed a lamp system for the lighthouse on Wangerooge Island. In 1833 and 1834 he received orders for meridian circles for the Hamburg and Pulkovo observatories that obliged him to complete the large circular dividing machine that his father had begun. In 1838 he completed a transit instrument for use in the first vertical circle at Pulkovo; it was made to an innovative design whereby a system of levers was employed to compensate for axial deflection.

In 1836 Karl August von Steinheil came to Hamburg from Munich to assist Adolf Repsold in the manufacture of several standard measuring devices, including a rock-crystal kilogram weight and a glass meterstick, that had been ordered by the Bavarian state government. Steinheil contributed directly to one of the two great innovations that Repsold made during the 1840V-the cylindrical manipulation of the split objective and the apparatus by which scales could be read directly from the objective. It was Steinheil’s suggestion that the scales, in the latter instance, be illuminated by means of electrically activated glowing platinum wires, a proposal that resulted in the practical application of the platinum-coil vacuum incandescent lamp that W. R. Grove had invented in 1840. Repsold may have also made use of a technique, patented by Frederick de Moleyns in 1841, to increase the brightness of the platinum coil by the injection of powdered charcoal.

Adolf Repsold also received constant help and encouragement from Bessel, who visited him in 1839 and ordered a meridian circle for the Kdnigsberg observatory, which was installed in 1841, the same year in which Repsold completed an equatorial instrument with a clockwork mechanism for the Christiania (now Oslo) observatory. The latter instrument was novel not only in that it compensated for deviations in the axis of declination by a system of weights, but also in that it incorporated a fine adjustment, which was entirely independent of the clockwork, for the right ascension and a microscopic circular reading dial.

In 1842 Adolf Repsoid was engaged in designing a heliometer for Oxford, a project in which he was particularly interested, when his work was interrupted by the great Hamburg fire of that year. He was stimulated to improve the design of the pump used in firefighting operations, and developed a vibrationless vane model that reduced the danger of breaking through the ice of the harbor during the winter months. Although Repsold’s vane pump had only a single cog for each wheel, it was more powerful than the rotating reciprocating engine employed until that time. In 1849 he completed the Oxford heliometer.

Adolf Repsold built a new workshop in 1855, in which he manufactured an eight-foot (2.44-meter) refracting telescope for the observatory at Lisbon and an equatorial instrument for the Gotha observatory. From 1859 he was assisted by his eldest son, Johann Adolf Repsoid, who had served an apprenticeship in the family laboratory, then worked for a year with C. A. F. Peters at the Altona observatory. In 1862 Johann Adolf Repsoid became a partner in the family business; in 1867 another of Adolf Repsold’s sons, Oskar, also joined the firm, and its name was changed again, to A. Repsoid and Sons. Adolf Repsoid simultaneously continued to work in the fire department, and in 1856 was promoted to Oberspritzenmeisfer. the post formerly held by his father. In 1858 he was made head of the central office of the Hamburg fire department, and worked toward increasing its effectiveness until his death from a heart attack in 1871.

Johann Adolf Repsold’s own designs contributed significantly to the progress of contemporary astronomy. In 1879 he invented a spring pendulum for regulating timing mechanisms in parallactic mountings, and in 1890 he devised a micrometer that eliminated subjective bias. He also wrote important biographical and technical works on the history of astronomy. He was appointed a member of the board of trustees of the Physikalisch-Technischen Reichsanstalt in Berlin-Charlottenburg in IS87; he was elected to both the Leopoldina and the St. Petersburg Academy of Sciences. He received an honorary doctorate from Göttingen in 1911. and in 1918, shortly before his death, the senate of the city of Hamburg granted him the title of professor, and he was made an honorary member of the Hamburg Geographical Society.

BIBLIOGRAPHY

J. G. Repsold’s writings are listed in Poggendorff, II, 607. Secondary literature includes R. Beneke, in Allgemeine deutsche Biographie, XXVIII (1889), 233–235; Friedrich Glitza, Errnnerungen an J. G. Repsold’s Leben (Hamburg, 1870); J. A. Repsold, Vermehrte Nachrichten ûber die Familie Repsold, nsbesondere uber Joh. Georg Repsold (Hamburg, 1896; 2nd ed., amended, 1915); and P. Riebesell, “Briefwechsel zwischen C. F. Gauss und J. G. Repsold,” in Mitteilungen der Mathematischen Gesellschaft in Hamburg, 6 , no. 8 (1928), 398–431.

A. Repsold’s writings are listed in Poggendorff, II, 608, and III, 1108. Secondary literature is J. A. Repsold, Nachrichten uber Adolf Repsold, fur die Familie zusammen—gestellt (Hamburg, 1900); and F. Reuleaux, Theoretische Kinematik. Grundzuge einer Theorie des Maschinenwesens (Brunswick, 1875), 401–403, and table 8, fig. 9.

J. A. Repsold’s writings are listed in Poggendorff, IV, 1232, and V, 1040. They include Erinnerungen an Hermann Kaufmann’s Jugendjahre. Zu seinem 100. Geburtstag (Munich, 1908); Zur Gesehichte der astronomischen Messwerkzeuge von Purbach bis Reichenbach, 2 vols. (Leipzig, 1908–1914); Nachtrage zu Geschichte der astro—nomisehen Messwerkzeuge, 2 vols. (Leipzig, 1908 1914); Ludwig Friedrichsen. Ein Bild seines Lebens (Hamburg, 1916); “Heron’s Dioptra,rdquo; in Astronomische Nachrichten, 206 , no. 4931 (1918), 93–98; “Alte arabische instrumente ibid., no. 4935, 125–135; “Uber Schattenquadrate,” ibid., 135–138; “H. C Suchmacher” ibid208, no. 4970–4971 (1918), 17–34; “Landgraf Wilhelm IV von Hessen und seine astronomischen Mitarbeiter,” ibid209 , no. 5005–5006 (1919), 193–210; “Uber vorgriechische Messwerkzeuge,” ibid,no. 5012, 305–307;“Friedrich Wilhelm Bessel,”ibid,210 , no. 5027–5028 (1919), 161–214; and “Uber Instrumente aus der Repsold’schen Werkstatt”ibid, 211, no. 5062 (1920), 405–414. An obituary is P. Harzer, “Nachruf auf Johann A. Repsold,” in Astronomische Nachrichten, 209 , no. 5007 (1919). 223–228.

More general information on the family is in L. Ambronn, Handbuch der astronomischen Instrumentkunde, 2 vols. (Berlin, 1899): J. G. Repsold, I, 286, 422; It, 513, 968; Adolf Repsold, I, 90; II. 562, 820; J. A. Repsold, 11, 958; the family firm, 1, 42, 74, 75, 303, 383, 398; II, 512, 553, 556, 560, 573, 582, 631, 653, 671, 677, 767, 865, 912. 930, 990; O. Heckmann, “Die Hamburger Sternwarte,”in Sterne und Weltraum2 , no. 1 (1963), 4–6; and L. Loewenherz, “Die Repsold’sche Werkstatt in Hamburg,” in Zeitschrift fur Instrumentenkunde, 7 (1887), 208–215.

Documents, family correspondence, shares of stock in the family firm, and diagrams and design sketches are in the Hamburg Staatsarchiv.

Paul A. Kirchvogel