Johan Maurits Mohr – Wikipedia
Johan Maurits Mohr (* approx. August 18, 1716 in Eppingen, † October 25, 1775 in Jakarta) was a German-Dutch clergyman and astronomer in Batavia.
Mohr studied theology at the University of Groningen from August 1733 (free) [first] what he concluded with a public disputation about the role of visions in the Bible in 1736. He went to Batavia at the time in 1737, where from October 1737 he initially as a vicar and from 1739 as a preacher of the Portuguese community [2] worked on behalf of the Dutch-East Indian company. [3] In 1743 he became rector of the theological seminar in Batavia. His passion was astronomical and scientific (meteorology, volcanology, earth magnetic field) observations that he in the Philosophical Transactions the Royal Society and the Treatises of the Dutch Society of Sciences published.
As a theologian, he published a Bible translation into Portuguese and Malay.
In 1761 he observed the Venusanite in Batavia, but still with insufficient instruments. In 1765 he built his own observatory at his own (very high) costs (the funds came from the legacy of his wife), with which he was one of the worldwide observers of the Venus tan on June 3, 1769 (and also the Mercury round on November 10th ). The global observation of this phenomenon was one of the highlights in the astronomical life of the 18th century and served to measure the solar system. James Cook, who had observed the passage in Tahiti, started on the way back to England in Batavia. Due to his mediation, Mohr’s observations were also published in 1771 (in Latin) in the Philosophical Transactions of the Royal Society. [4] In addition, Mohr published her (in Dutch) in the negotiations of the Dutch society the Sciences 1770 in Haarlem. During his stay in Batavia, Cook lost many members of his ship crew, including his astronomer Charles Green, by malaria – Batavia was notorious for this plague under seafarers, there was a lot of standing water in channels. In addition to Cook, Louis Antoine de Bougainville also visited him on his world tour in 1768 and reported on the Mohr observatory.
The observation of the Venus passage in 1769 through Mohr almost failed because the Venus passage began four hours before sunrise and the sun was covered by clouds in the first two hours of the day (observations were only possible from 8 a.m.). Mohr had prepared himself carefully and has precisely determined the geographical coordinates of Batavia in recent years. He had much better instruments than in 1761: a Gregorian mirror telescope of 3.5 inch focal length (manufacturer John Dollond) and a heliometer for sun observation, an astronomical pendulum watch from John Shelton (with anchor to George Graham) and a square of 2.5 feet (Manufacturer John Bird, London) to correct the astronomical clock.
While Mohr’s observations from 1761 (which he also published in Dutch) were unusable, [5] were correct from 1769, but apparently they were held [6] Not for precisely enough, so that, for example, Johann Franz Encke’s report on the Venus passage were not taken into account. In particular, his length determination of Batavia was not considered precisely enough, although it was praised by Cook.
Mohr continued his astronomical observations after 1769 and recorded daily observations of weather and earth magnet field, which he did not publish. His last publication of 1773 deals with the outbreak of the 3000 m high volcano Gunung Papadajan (165 km southeast of Batavia) from August 1772.
After his death, no successor for his observations in Batavia and his observatory fell apart. In 1780 it was badly damaged by an earthquake. In 1782 Mohr’s widow Anna Elizabeth van T’Hoff died and the building served to accommodate employees of the East Indian company and from 1809 as a barracks. It was subsequently demolished (in 1844 only the foundations were visible).
The later Admiral Francis Beaufort visited the observatory in August 1789 as a 15-year-old, which made him a very strange impression on him. There was only one observation room on the top of the building at a height of 100 feet. If you stamped your foot in the rest of the house, this shook the instruments in the observatory.
A upswing in scientific life in Batavia only took place after the death of Mohr in 1778 by founding the Royal Batavian Society of Arts and Sciences. The foundation was still initiated by Mohr, but initially did not come about through the lack of support for official bodies. The members initially wanted to continue Mohr’s observations and one of the most active members of society, the clergyman Johannes Hooijman bought the instruments from Mohr’s widow in 1776. However, it turned out that they had suffered greatly from the tropical climate – the efforts to observe astronomical observations soon afterwards in Batavia in the sand. Since there were no instrument makers in Batavia, the instruments were sent to Amsterdam for repair. There they forgot for some time, but they were partially used again and the trail of some instruments was later tracked in various Dutch museums.
The Kleinplanet 5084 Johanmohr is named after him.
- H.J. Zuidervaart, R.H. van Gent: A Bare Outpost of Learned European Culture on the Edge of the Jungles of Java: Johan Maurits Mohr (1716–1775) and the Emergence of Instrumental and Institutional Science in Dutch Colonial Indonesia . In: Isis , Band 95, 2004, S. 1–33, PMID 15301065
- Robert H. van Gent: Observations of the 1761 and 1769 transits of Venus from Batavia (Dutch East Indies) . In: D. W. Kurtz: Transits of Venus , Proc. International Astronomical Union (IAU Colloquium 196), Cambridge University Press, 2005, S. 67
- J. van der Bilt: Venus against the sun disk 1761, 1769; A page from the history of Dutch astronomy . Wolters, Groningen 1940
- H. J. Zuidervaart: Of “Consters” and heavenly phenomena: Dutch astronomy in the eighteenth century . Erasmus Publishing, Rotterdam 1999
- ↑ University of Groningen: White student academy Groninganae . Wolters’ U. M., Groningen 1915, S. 182
- ↑ First he was to become a pastor in the Portuguese community in the Dutch branch in Galle on Ceylon; But that shifted because he initially wanted to learn Portuguese – after his marriage to Johanna Cornelia van der Sluys, he remained entirely in Batavia.
- ↑ K. van Berkel: In the footsteps of Stevin. History of natural science in the Netherlands 1580-1940 . Boom, Amsterdam 1985, S. 211 ff.
- ↑ Mohr: Transfer Friday and Wednesday in their going out of the Sunday 4to Juniiii and the 10to November 1769 observed . In: Phil. Trans. Roy. Soc. , Band 61, 1771, Gallica.bnf.fr
- ↑ So also the astronomer van der Bilt in his book in 1940
- ↑ Robert H. van Gent in Kurtz: Transits of Venus , Discussion, p. 73
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