Johan Maurits Mohr
Johan Maurits Mohr ( * ca August 18, 1716 in Epping, † October 25, 1775 in Jakarta ) was a German - Dutch clergyman and astronomer in Batavia.
Life
Mohr studied from August 1733 (free) theology at the University of Groningen, which he graduated with a public disputation on the role of visions in the Bible in 1736. He went in 1737 to the then Dutch Batavia, where he initially worked from October 1737 as vicar and 1739 as a preacher of the Portuguese community on behalf of the Dutch East India Company. In 1743 he became rector of the Theological Seminary in Batavia. He was passionate about astronomy and science ( meteorology, volcanology, Earth's magnetic field ) observations that he published in the Philosophical Transactions of the Royal Society and the Verhandelingen the Dutch Maatschappij the Wetenschappen.
As a theologian, he published a translation of the Bible into Portuguese and Malay.
Transit of Venus in 1761 and 1769
1761, he observed the transit of Venus in Batavia, but still with inadequate instruments. In 1765 he built at his own (very high ) cost of a private observatory (the center came from the inheritance of his wife), with whom he was one of the global observer of the transit of Venus on June 3, 1769 ( and also of the Mercury transit on November 10, ). The global observation of this phenomenon was one of the highlights of the astronomical beginning of the 18th century and served the measurement of the solar system. James Cook, who had observed the passage in Tahiti, put on on the way back to England in Batavia. Through his mediation Mohr's observations were also published in 1771 ( in Latin) in the Philosophical Transactions of the Royal Society. In addition, Mohr published them (in Dutch) in the negotiations of the Dutch Maatschappij the Wetenschappen 1770 in Haarlem. Cook lost during his stay in Batavia many members of his crew, including his astronomer Charles Green, from malaria - Batavia was for this disease at that time notorious among sailors - there was a lot of standing water in canals. In addition to Cook visited him Louis Antoine de Bougainville in 1768 on his trip around the world and reported on the Observatory of Mohr.
The observation of the transit of Venus in 1769 by Mohr failed almost since the passage of Venus started four hours before sunrise and the sun was covered in the first two hours of the day by clouds (observations were possible in the morning starts from 8 clock ). Mohr had carefully prepared and the geographical coordinates of Batavia determined in recent years exactly. He had much better tools than 1761: a Gregorian reflecting telescope of 3.5 inches focal length ( maker John Dollond ) and a Heliometer for solar observation, an astronomical clock by John Shelton ( with anchor escapement by George Graham ) and a quadrant of 2.5 feet (manufacturer John Bird, London) for the correction of the astronomical clock.
While Mohr's observations of 1761 (which he also in Dutch published ) were useless, were correct in 1769, but they did not appear for just enough so that they were not taken into account, for example, in the report by Johann Franz Encke on the transit of Venus. In particular, it did not consider its length determination of Batavia for accurate enough, although it has been praised by Cook.
The time after
Mohr continued his astronomical observations continued after 1769 and recorded daily observations of weather and Earth's magnetic field, but which he did not publish. His latest release from 1773 deals with the outbreak of the 3000 m high volcano Gunung Papadajan (165 km south-east of Batavia ) in August 1772.
After his death no successor for his observations took place in Batavia and his observatory fell apart. In 1780 it was severely damaged by an earthquake. 1782 died Mohr's widow Anna Elizabeth van't Hoff and the building was used to house employees of the East India Company and in 1809 as a barracks. It was demolished in the sequence (1844 only the foundations were already visible).
The later Admiral Francis Beaufort visited the age of 15, the observatory in August 1789, which made a very strange impression on him. There was only one observation room at the top of the building 100 feet in height. You stomped the rest of the house with his foot, it shook the instruments in the observatory.
An upswing scientific life in Batavia took place after the death of Mohr in 1778 by founding the Royal Batavian Society of Arts and Sciences. The foundation had been still initiated by Mohr, but first came into existence not through lack of support from official bodies. The members wanted to initially Mohr's observations continued and one of the most active members of society, the priest Johannes HOOIJMAN bought the instruments in 1776 by Mohr's widow. But it turned out that they had suffered much under the tropical climate - the efforts to astronomical observations proceeded soon in Batavia in the sand. Since there was no instrument maker in Batavia, the instruments were sent to Amsterdam for repair. There you forgot them some time, but they were partially re- use and the track of some instruments could be traced later in several Dutch museums.
Others
The minor planet 5084 Johan Mohr is named after him.