Mathematicians on board: introducing lunar distances to life at sea

Nevil Maskelyne, the Cambridge-trained mathematician and later Astronomer Royal, was appointed by the Royal Society to observe the 1761 transit of Venus from the Atlantic island of St Helena, assisted by the mathematical practitioner Robert Waddington. Both had experience of measurement and computation within astronomy and they decided to put their outward and return voyages to a further use by trying out the method of finding longitude at sea by lunar distances. The manuscript and printed records they generated in this activity are complemented by the traditional logs and journals kept by the ships’ officers. Together these records show how the mathematicians came to engage with the navigational practices that were already part of shipboard routine and how their experience affected the development of the methods that Maskelyne and Waddington would separately promote on their return. The expedition to St Helena, in particular the part played by Maskelyne, has long been regarded as pivotal to the introduction of the lunar method to British seamen and to the establishment of the Nautical Almanac. This study enriches our understanding of the episode by pointing to the significant role played by the established navigational competence among officers of the East India Company.

Manuel Johnson's tide record at St. Helena

The astronomer Manuel Johnson, a future President of the Royal Astronomical Society, recorded the ocean tides with his own instrument at St. Helena in 1826–1827, while waiting for an observatory to be built. It is an important record in the history of tidal science, as the only previous measurements at St. Helena had been those made by Nevil Maskelyne in 1761, and there were to be no other systematic measurements until the late 20th century. Johnson's tide gauge, of a curious but unique design, recorded efficiently the height of every tidal high and low water for at least 13 months, in spite of requiring frequent re-setting. These heights compare very reasonably with a modern tidal synthesis based on present-day tide gauge measurements from the same site. Johnson's method of timing is unknown, but his calculations of lunar phases suggest that his tidal measurements were recorded in Local Apparent Time. Unfortunately, the recorded times are found to be seriously and variably lagged by many minutes. Johnson's data have never been fully published, but his manuscripts have been safely archived and are available for inspection at Cambridge University. His data have been converted to computer files as part of this study for the benefit of future researchers.

Dawes Point

The promontory at the western end of Circular Quay was known to the Aboriginal people as Tar-Ra. It was chosen as the site for an observatory by Lieutenant William Dawes, who arrived with the first Europeans. Dawes came with a recommendation from the Astronomer Royal, Dr Nevil Maskelyne, and some instruments from the Board of Longitude, with which to study the heavens. The point was initially named Maskelyne Point, but as Dawes lived there while he was in the colony from 1788 until 1791, the area became known as Dawes Point.Dawes kept the colony's first meteorological records here, and it was also here that Dawes pinned the town's first clock to a rock face. He encouraged friendship with local Aboriginal people, including a young girl Pategarang, from whom he learned some of the language of the Cadigal people. Dawes's notebooks, held in the School of Oriental and African Studies at the University of London, remain one of the most precious records of the local language.

“To demonstrate the exactness of the instrument”: Mountainside Trials of Precision in Scotland, 1774

ArgumentThe British Astronomer Royal, Nevil Maskelyne, spent four months on a Scottish mountainside in 1774, making observations of zenith stars and coordinating a detailed survey of the size and shape of the mountain Schiehallion, in order to demonstrate and quantify what was known as “the attraction of mountains.” His endeavors were celebrated in London, where it was stated that he had given proof of the universality of Newtonian gravitation and allowed for a calculation of the relative densities of the earth as a whole and the earth near its surface. This paper argues that the “Schiehallion Experiment” was as much a trial of the precision of Maskelyne's instruments and their expert management as it was a trial of Newtonian theory. By tracing the biography of the key instrument used by Maskelyne, his zenith sector, we see how much personal credibility was a stake for him in Scotland. By considering the mountainside as a place to test and reveal the precision of astronomical instruments we see a link between the Scottish endeavors and Maskelyne's ambitions for the Greenwich Observatory.

Astronomical labourers: Maskelyne's assistants at the Royal Observatory, Greenwich, 1765-1811

Nevil Maskelyne FRS held the post of British Astronomer Royal from 1765 to 1811. As Astronomer Royal, Maskelyne's main task was to ensure that the positions of the Sun, Moon, planets and stars were regularly observed and that those observations were published in an accessible form. To do this, and simultaneously to maintain his role within London's scientific society, Maskelyne hired an assistant to undertake the routine work of the Observatory. This paper considers Maskelyne's assistants at the Royal Observatory, Greenwich, identifies who the assistants were, and describes their working conditions.