Francis Baily

Francis Baily
Royal Astronomical Society portrait
Born	28 April 1774(1774-04-28) Newbury in Berkshire
Died	30 August 1844 (aged 70) London
Nationality	British
Fields	Astronomy
Known for	Baily's beads

Francis Baily (28 April 1774 – 30 August 1844) was an British astronomer, most famous for his observations of 'Baily's beads' during an eclipse of the Sun.

Life

Baily was born at Newbury in Berkshire in 1774. After a tour in the unsettled parts of North America in 1796–1797, his journal of which was edited by Augustus de Morgan in 1856, Baily entered the London Stock Exchange in 1799. The successive publication of Tables for the Purchasing and Renewing of Leases (1802), of The Doctrine of Interest and Annuities (1808), and The Doctrine of Life-Annuities and Assurances (1810), earned him a high reputation as a writer on life-contingencies; he amassed a fortune through diligence and integrity and retired from business in 1825, to devote himself wholly to astronomy.

Astronomical work

By 1820, Baily had already taken a leading part in the foundation of the Royal Astronomical Society, and its Gold Medal was awarded him, in 1827, for his preparation of the Society's Catalogue of 2881 stars (Memoirs R. Astr. Soc. ii.). Later, in 1843, he would win the Gold Medal again.

The reform of the Nautical Almanac in 1829 was set on foot by his protests. He recommended to the British Association in 1837, and in great part executed, the reduction of Joseph de Lalande's and Nicolas de Lacaille's catalogues containing about 57,000 stars; he superintended the compilation of the British Association's Catalogue of 8377 stars (published 1845); and revised the catalogues of Tobias Mayer, Ptolemy, Ulugh Beg, Tycho Brahe, Edmund Halley and Hevelius (Memoirs R. Astr. Soc. iv,, xiii.).

His observations of "Baily's Beads," during an annular eclipse of the sun on 15 May 1836, at Inch Bonney in Roxburghshire, started the modern series of eclipse expeditions. The phenomenon, which depends upon the irregular shape of the moon's limb, was so vividly described by him as to attract an unprecedented amount of attention to the total eclipse of 8 July 1842, observed by Baily himself at Pavia.

Baily's beads

In other work, he completed and discussed H. Foster's pendulum experiments, deducing from them an ellipticity for the earth of 1/289.48 (Memoirs R. Astr. Soc. vii.). This value was corrected for the length of the seconds-pendulum by introducing a neglected element of reduction, and was used, in 1843, in the reconstruction of the standards of length. His laborious operations for determining the mean density of the earth, carried out by Henry Cavendish's method (1838–1842), yielded the authoritative value of 5.66.

Baily died in London on 30 August 1844 and was buried in the family vault in Thatcham parish church. His Account of the Rev. John Flamsteed (1835) is of fundamental importance to the scientific history of that time. It included a republication of the British Catalogue.

The lunar crater Baily was named in his honour.

Further reading

• Herschel, John (1844). "Memoir of the late Francis Baily". Monthly Notices of the Royal Astronomical Society 6: 89 – 121. http://adsabs.harvard.edu//full/seri/MNRAS/0006//0000089.000.html. 
• Dieke, Sally H. (1970). "Baily, Francis". Dictionary of Scientific Biography. 1. New York: Charles Scribner's Sons. pp. 402–403. ISBN 0684101149. 
• Higgitt, Rebekah (Mar 2004). "Astronomers against Newton.". Endeavour 28 (1): pp. 20–4. 2004 Mar. doi:10.1016/j.endeavour.2004.01.012. PMID 15036924. 

External links

Wikisource has original works written by or about: Francis Baily

• Map of Etoiles fixes
• Royal Berkshire History: Francis Baily (1774-1844)
• Awarding of RAS gold medal, 1827: MNRAS 1 (1827) 14
• Awarding of RAS gold medal, 1843: MNRAS 5 (1843) 248
• Archival material relating to Francis Baily listed at the UK National Register of Archives
• "BAILY, FRANCIS". Dictionary of national biography, 2: pages 427-432. 1885. http://books.google.com/books?id=RysJAAAAIAAJ&pg=PA427. 

 "Baily, Francis". Encyclopædia Britannica (11th ed.). 1911.  This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.