Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either o ...

and geodesist who named 14 out of the 88 constellations. From 1750 to 1754, he studied the sky at the

Cape of Good Hope The Cape of Good Hope ( af, Kaap die Goeie Hoop ) ;''Kaap'' in isolation: pt, Cabo da Boa Esperança is a rocky headland on the Atlantic coast of the Cape Peninsula in South Africa. A common misconception is that the Cape of Good Hope is ...

in present-day

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring count ...

. Lacaille observed over 10,000 stars using just a half-inch

refracting telescope A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spyglasses and ...

Biography

Born at Rumigny in the

Ardennes The Ardennes (french: Ardenne ; nl, Ardennen ; german: Ardennen; wa, Årdene ; lb, Ardennen ), also known as the Ardennes Forest or Forest of Ardennes, is a region of extensive forests, rough terrain, rolling hills and ridges primarily in Be ...

in eastern France, he attended school in Mantes-sur-Seine (now Mantes-la-Jolie). Afterwards, he studied rhetoric and philosophy at the Collège de Lisieux and then theology at the

Collège de Navarre The College of Navarre (french: Collège de Navarre) was one of the colleges of the historic University of Paris, rivaling the Sorbonne and renowned for its library. History It was founded by Queen Joan I of Navarre in 1305, who provided for t ...

. He was left destitute in 1731 by the death of his father, who had held a post in the household of the duchess of Vendôme. However, he was supported in his studies by the Duc de Bourbon, his father's former patron. After he graduated, he did not accept ordination as a priest but took

deacon A deacon is a member of the diaconate, an office in Christian churches that is generally associated with service of some kind, but which varies among theological and denominational traditions. Major Christian churches, such as the Catholic Chur ...

's orders, becoming an

Abbé ''Abbé'' (from Latin ''abbas'', in turn from Greek , ''abbas'', from Aramaic ''abba'', a title of honour, literally meaning "the father, my father", emphatic state of ''abh'', "father") is the French word for an abbot. It is the title for lowe ...

. He concentrated thereafter on science, and, through the patronage of

Jacques Cassini Jacques Cassini (18 February 1677 – 16 April 1756) was a French astronomer, son of the famous Italian astronomer Giovanni Domenico Cassini. Cassini was born at the Paris Observatory. Admitted at the age of seventeen to membership of the Frenc ...

, obtained employment, first in

surveying Surveying or land surveying is the technique, profession, art, and science of determining the terrestrial two-dimensional or three-dimensional positions of points and the distances and angles between them. A land surveying professional is ...

the coast from

Nantes Nantes (, , ; Gallo: or ; ) is a city in Loire-Atlantique on the Loire, from the Atlantic coast. The city is the sixth largest in France, with a population of 314,138 in Nantes proper and a metropolitan area of nearly 1 million inhabit ...

Bayonne Bayonne (; eu, Baiona ; oc, label= Gascon, Baiona ; es, Bayona) is a city in Southwestern France near the Spanish border. It is a commune and one of two subprefectures in the Pyrénées-Atlantiques department, in the Nouvelle-Aquitaine ...

, then, in 1739, in remeasuring the French meridian arc, for which he is honoured with a pyramid at

Juvisy-sur-Orge Juvisy-sur-Orge (, literally ''Juvisy on Orge'') is a commune in the Essonne department in Île-de-France in northern France. It is located 18 km south-east of Paris, a few kilometres south of Orly Airport. The site of the town has been o ...

. The success of this difficult operation, which occupied two years, and achieved the correction of the anomalous result published by

in 1718, was mainly due to Lacaille's industry and skill. He was rewarded by admission to the Royal Academy of Sciences and appointment as Professor of mathematics in the

Mazarin college Mazarin may refer to: * Cardinal Mazarin, 17th-century minister to the French king *Rethel, formerly the Duchy of Mazarin, a commune in France *Mazarin River, a river in Canada * ''Mazarin'' (album), a 2003 pop music album See also *"The Adventure ...

of the

University of Paris The University of Paris (french: link=no, Université de Paris), Metonymy, metonymically known as the Sorbonne (), was the leading university in Paris, France, active from 1150 to 1970, with the exception between 1793 and 1806 under the French Revo ...

, where he constructed a small observatory fitted for his own use. He was the author of a number of influential textbooks and a firm advocate of Newtonian gravitational theory. His students included

Antoine Lavoisier Antoine-Laurent de Lavoisier ( , ; ; 26 August 17438 May 1794),
CNRS ( Jean Sylvain Bailly, both of whom were later guillotined during the

French Revolution The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in November 1799. Many of its ideas are conside ...

Voyage to the Cape of Good Hope

His desire to determine the distances of the planets trigonometrically, using the longest possible baseline, led him to propose, in 1750, an expedition to the

. This was officially sanctioned by Roland-Michel Barrin de La Galissonière. There, he constructed an observatory on the shore of

Table Bay Table Bay (Afrikaans: ''Tafelbaai'') is a natural bay on the Atlantic Ocean overlooked by Cape Town (founded 1652 by Van Riebeeck) and is at the northern end of the Cape Peninsula, which stretches south to the Cape of Good Hope. It was named b ...

with the support of the Dutch Governor Ryk Tulbagh. The primary result of his two-year stay were the observations of nearly 10,000 southern stars, the production of which required observing every night for over a year. In the course of his survey he took note of 42 nebulous objects. He also achieved his aim of determining the lunar and solar

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby object ...

es (

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmos ...

serving as an intermediary). This work required near-simultaneous observations from Europe which were carried out by

Jérôme Lalande Joseph Jérôme Lefrançois de Lalande (; 11 July 1732 – 4 April 1807) was a French astronomer, freemason and writer. Biography Lalande was born at Bourg-en-Bresse (now in the département of Ain) to Pierre Lefrançois and Marie‐Anne‐ ...

. His southern catalogue, called ''Coelum Australe Stelliferum'', was published posthumously in 1763. He found it necessary to introduce 14 new constellations which have since become standard. One of these was Mons Mensae, the only constellation named after a terrestrial feature (the Table Mountain). While at the

Cape A cape is a clothing accessory or a sleeveless outer garment which drapes the wearer's back, arms, and chest, and connects at the neck. History Capes were common in medieval Europe, especially when combined with a hood in the chaperon. T ...

, Lacaille performed an

arc measurement Arc measurement, sometimes degree measurement (german: Gradmessung), is the astrogeodetic technique of determining of the radius of Earth – more specifically, the local Earth radius of curvature of the figure of the Earth – by relating the l ...

to determine the radius of the earth in the southern hemisphere. He set out a baseline in the Swartland plain north of present-day

Darling Darling is a term of endearment of Old English origin. Darling or Darlin' or Darlings may also refer to: People * Darling (surname) * Darling Jimenez (born 1980), American boxer * Darling Légitimus (1907–1999), French actress Places Austral ...

. Using

triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle ...

he then measured a 137 km arc of meridian between

Cape Town Cape Town ( af, Kaapstad; , xh, iKapa) is one of South Africa's three capital cities, serving as the seat of the Parliament of South Africa. It is the legislative capital of the country, the oldest city in the country, and the second larges ...

and

Aurora An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...

, determining the

astronomical latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...

s of the end points by means of astronomical-geodetic observations. There is a memorial to his work at a location near Aurora, pictured here. His result suggested that the earth was more flattened towards the south pole than towards the north.

George Everest Colonel Sir George Everest CB FRS FRAS FRGS (; 4 July 1790 – 1 December 1866) was a British surveyor and geographer who served as Surveyor General of India from 1830 to 1843. After receiving a military education in Marlow, Everest joined ...

, of the Indian Survey, while recuperating from an illness at the Cape nearly seventy years later, suggested that Lacaille's latitude observations had been affected by the deflection of the vertical, caused by gravitational attraction of Table Mountain at the southern end and by the Piketberg Mountain at the northern. In 1838, Thomas Maclear, who was Astronomer Royal at the Cape, repeated the measurements over a longer baseline (

Maclear's arc measurement Sir Thomas Maclear (17 March 1794 – 14 July 1879) was an Irish-born South African astronomer who became Her Majesty's astronomer at the Cape of Good Hope. Life He was born in Newtownstewart, County Tyrone, Ireland, the eldest son of Rev Jam ...

) and ultimately confirmed Everest's conjecture. Maclear's Beacon was erected on the Table Mountain in

to help with the verification.

Computing

During his voyage to the southern hemisphere as a passenger on the vessel ''Le Glorieux'', captained by the noted hydrographer Jean-Baptiste d'Après de Mannevillette, Lacaille became conscious of the difficulties in determining positions at sea. On his return to Paris he prepared the first set of tables of the Moon's position that was accurate enough to use for determining time and longitude by the method of 'Lunars' ( Lunar distances) using the orbital theory of Clairaut. Lacaille was in fact an indefatigable calculator. Apart from constructing astronomical ephemerides and mathematical tables, he calculated a table of

eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ce ...

s for 1800 years. Lalande said of him that, during a comparatively short life, he had made more observations and calculations than all the astronomers of his time put together. The quality of his work rivalled its quantity, while the disinterestedness and rectitude of his moral character earned him universal respect.

Later life

On his return to Paris in 1754, following a diversion to

Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label=Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It incl ...

, Lacaille was distressed to find himself an object of public attention. He resumed his work at the Mazarin College. In 1757 he published his ''Astronomiae Fundamenta Novissimus'', containing a list of about 400 bright stars with positions corrected for aberration and

nutation Nutation () is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behaviour of a mechanism. In an appropriate reference fra ...

. He carried out calculations on comet orbits and was responsible for giving

Halley's Comet Halley's Comet or Comet Halley, officially designated 1P/Halley, is a List of periodic comets, short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye fr ...

its name. His last public lecture, given on 14 September 1761 at the Royal Academy of Sciences, summarised the improvements to astronomy that had occurred during his lifetime, to which he had made no small contribution. His death, probably caused in part by over-work, occurred in 1762. He was buried in the vaults of the Mazarin College, now the

Institut de France The (; ) is a French learned society, grouping five , including the Académie Française. It was established in 1795 at the direction of the National Convention. Located on the Quai de Conti in the 6th arrondissement of Paris, the institute ...

in Paris.

Honours

In 1754, he was elected a foreign member of the Royal Swedish Academy of Sciences. He was also an honorary member of the academies of Saint Petersburg and Berlin, the

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, r ...

of London and the

Royal Society of Göttingen Royal may refer to: People * Royal (name), a list of people with either the surname or given name * A member of a royal family Places United States * Royal, Arkansas, an unincorporated community * Royal, Illinois, a village * Royal, Iowa, a cit ...

, and the Institute of Bologna. Lacaille has the honor of naming 14 different constellations: * Antlia * Caelum * Circinus *

Fornax Fornax () is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 mod ...

* Horologium *

Mensa Mensa may refer to: * Mensa International, an organization for people with a high intelligence quotient (IQ) * Mensa (name), a name and list of people with the given name or surname * Mensa (constellation), a constellation in the southern sky * Men ...

* Microscopium * Norma * Octans * Pictor * Pyxis * Reticulum *

Sculptor Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable ...

* Telescopium The crater " La Caille" on the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...

is named after him.

Asteroid An asteroid is a minor planet of the Solar System#Inner solar system, inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic o ...

9135 Lacaille (AKA 7609 P-L and 1994 EK6), discovered on 17 October 1960 by Cornelis Johannes van Houten, Ingrid van Houten-Groeneveld and

Tom Gehrels Anton M.J. "Tom" Gehrels (February 21, 1925 – July 11, 2011) was a Dutch–American astronomer, Professor of Planetary Sciences, and Astronomer at the University of Arizona, Tucson. Biography Youth and education Gehrels was born at Haa ...

at Palomar Observatory, was also named after him. In honor of his contribution to the study of the southern hemisphere sky, a 60-cm telescope at Reunion Island will be named the Lacaille Telescope.(French)

Main works

La Caille - Leçons elementaires d'astronomie géométrique et physique, 1755 - 1437831

*''Leçons élémentaires de Mathématiques'' (1741), frequently reprinted *ditto ''de Mécanique'' (1743), &c. *ditto ''d'Astronomie'' (1746); 4th edition augmented by Lalande (1779) * 2nd edition *Calculations by him of eclipses for eighteen hundred years were inserted in ''L'Art de vérifier les dates'' by

Benedictine , image = Medalla San Benito.PNG , caption = Design on the obverse side of the Saint Benedict Medal , abbreviation = OSB , formation = , motto = (English: 'Pray and Work') , found ...

historian

Charles Clémencet Charles Clémencet (17035 August 1778) was a French Benedictine historian. He was born in Painblanc, in present-day Côte-d'Or, and was one of the authors who helped complete the great chronological work (the usual short form of a long title). H ...

(1750) *He communicated to the Academy in 1755 a classed catalogue of forty two southern nebulae, and gave in t. ii. of his ''Ephémérides'' (1755) practical rules for the employment of the lunar method of longitudes, proposing in his additions to Pierre Bouguer's ''Traité de Navigation'' (1760) the model of a nautical almanac. *''Tabulae Solares'' (1758)

Star catalogue

*"Remarques sur le Catalogue suivant des principales Étoiles du Ciel",
Éphémérides des mouvemens célestes
pour dix années, depuis 1755 jusqu'en 1765, et pour le meridien de la ville de Paris'' (1755), pp. xlix-lxiii. *"Table des Ascensions Droites et des Declinaisons Apparentes des Etoiles australes renfermées dans le tropique du Capricorne..."
''Memoires Academie Royale des Sciences'' pour 1752
(1756), pp. 539–592. (describing fourteen new constellations) *"Stellarum ascensiones rectae verae & declinationes verae ad Epocham anni ineuntis 1750",
Astronomiae fundamenta
novissimis solis et stellarum observationibus stabilita, Lutetiae in Collegio mazarineo et in Africa ad Caput Bonae-Spei'' (1757), pp. 233–237. (containing a standard catalogue of 398 stars) *"Stellarum longitudines & latitudines verae ad annum ineuntum 1750, Earum praecipue quae Zodiacales sunt", ''Astronomiae fundamenta'' (1757), pp. 238–239. *"Stellarum Australium Catalogus
''Coelum australe stelliferum''
''seu, Observationes ad Construendum Stellarum Australium Catalogum Institutae: in Africa ad Caput Bonae-Spei'' (1763), (edited by J. D. Maraldi), pp. 139–158. *"Catalogue suivant des principales Étoiles du Ciel, pour le commencement de l'Anee 1750",
Éphémérides des mouvemens célestes
pour dix annees, depuis 1765 jusqu'en 1775, et pour le meridien de la ville de Paris'' (1763), pp. lvii-lxiv. *"Observations sur 515 étoiles du Zodiaque", ''Éphémérides des mouvemens célestes, pour dix annees, depuis 1765 jusqu'en 1775'', (1763) pp. lxv-lxxvii.
''A catalogue of 9766 stars in the southern hemisphere,''
'for the beginning of the year 1750: from the observations of the Abbé de Lacaille, made at the cap of Good Hope in the years 1751 and 1752; with a preface by Sir J. F. W. Herschel'' (1847), giving zone observations of about 10,000 stars, re-edited by F. Baily

Star map

* "Planisphere contenant les Constellations Celestes comprises entre le Pole Austral et le Tropique du Capricorne", ''Mem. de l'Ac. R. des Sc.'' 1752 (1756), p. 590, plate 20. (French) *
Coelum Australe
, ''Coelum australe stelliferum'' (1763). (Latin) * "Planisphere des Etoiles les Australes dressé par M. i'Abbé de la Caille", ''Atlas Celeste de Flamsteed'' (1776), 2nd ed., plate 29. (French)* "Planisphere des Etoiles les Australes dressé par M. i'Abbé de la Caille", ''Recueil de Planches de l'Encyclopédie par ordre de matieres'' (1789), vol. 7, plate 3. (French) * "Planisphere des Etoiles les Australes dressé par M. i'Abbé de la Caille", ''Atlas Celeste de Flamsteed'' (1795), 3rd ed., plate 29. (French)

Notes

References

*Jean-Baptiste Joseph Delambre, Histoire de l'astronomie au Dix-Huitième siècle, Paris, Bachelier, 1827. *

David S. Evans David Sparks Evans (born 1954) is an American economist specializing in antitrust and two-sided markets. He is the chairman of Global Economics, Inc., and founding editor of Competition Policy International. He teaches at the University College ...

: ''Lacaille: astronomer, traveller; with a new translation of his journal''. Tucson: Pachart, 1992 * I.S. Glass: ''Nicolas-Louis de La Caille, Astronomer and Geodesist''. Oxford: Oxford University Press, 2013 *N.L. de La Caille: ''Travels at the Cape, 1751–53: an annotated translation of Journal historique du voyage fait au Cap de Bonne-Espérance ...''; transl. and ed. by R. Raven-Hart. Cape Town: A.A. Balkema for the Friends of the South African Library, 1976 *Journal historique du voyage fait au Cap de Bonne-Espérance par feu M. l'abbé de La Caille..., Paris, Guillyn, 1763. This work was edited by Abbé Carlier, who attached a discourse on La Caille's life. *
Virtual exhibition on Paris Observatory digital library
{{DEFAULTSORT:Lacaille, Nicolas Louis De 1713 births 1762 deaths People from Ardennes (department) University of Paris faculty 18th-century French astronomers Members of the French Academy of Sciences Members of the Royal Swedish Academy of Sciences Fellows of the Royal Society Honorary members of the Saint Petersburg Academy of Sciences Catholic clergy scientists French geodesists