Born atRumigny in theArdennes in eastern France, he attended school in Mantes-sur-Seine (nowMantes-la-Jolie). Afterwards, he studied rhetoric and philosophy at theCollège de Lisieux and then theology at theCollège de Navarre. 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 theDuc de Bourbon, his father's former patron.[5]
After he graduated, he did not accept ordination as a priest but tookdeacon's orders, becoming anAbbé. He concentrated thereafter on science, and, through the patronage ofJacques Cassini, obtained employment, first insurveying the coast fromNantes toBayonne, then, in 1739, in remeasuring theFrench meridian arc, for which he is honoured with a pyramid atJuvisy-sur-Orge. The success of this difficult operation, which occupied two years, and achieved the correction of the anomalous result published byJacques Cassini in 1718, was mainly due to Lacaille's industry and skill. He was rewarded by admission to theRoyal Academy of Sciences and appointment as Professor of mathematics in theMazarin college of theUniversity of Paris, 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 includedAntoine Lavoisier andJean Sylvain Bailly, both of whom were later guillotined during theFrench Revolution.
A memorial to the Abbé de Lacaille andThomas Maclear, at Aurora in the Western Cape of South Africa. The English portion of the inscription reads: "This is the site of the Maclear Beacon positioned in 1838 near the original North Terminal of the Arc of Meridian positioned by Abbé de Lacaille, the first surveyor to introduce Geodetic Surveying into South Africa." Open the image to see the Afrikaans portion.
His desire to determine the distances of the planets trigonometrically, using the longest possible baseline, led him to propose, in 1750, an expedition to theCape of Good Hope. This was officially sanctioned byRoland-Michel Barrin de La Galissonière. There, he constructed an observatory on the shore ofTable Bay with the support of the Dutch GovernorRyk Tulbagh. The primary result of his two-year stay was 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 solarparallaxes (Mars serving as an intermediary). This work required near-simultaneous observations from Europe which were carried out byJérôme Lalande.
His southern catalogue, calledCoelum Australe Stelliferum, was published posthumously in 1763. He found it necessary to introduce 14 newconstellations which have since become standard.[6] One of these wasMons Mensae, the only constellation named after a terrestrial feature (theTable Mountain). An 1890 study of this catalogue byB. A. Gould found a considerable number of errors.[7]
During his voyage to the southern hemisphere as a passenger on the vesselLe 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 ofClairaut. Lacaille was in fact an indefatigable calculator. Apart from constructing astronomicalephemerides and mathematical tables, he calculated a table ofeclipses 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.
On his return to Paris in 1754, following a diversion toMauritius, Lacaille was distressed to find himself an object of public attention. He resumed his work at the Mazarin College.
In 1757 he published hisAstronomiae Fundamenta Novissimus, containing a list of about 400 bright stars with positions corrected foraberration andnutation. He carried out calculations on comet orbits and was responsible for givingHalley's Comet 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 theInstitut de France in Paris.
Leçons elementaires d'astronomie, géométrique et physique, 1755 editionMessier 55 is a globular cluster discovered in 16 June 1752.[14]
Leçons élémentaires de Mathématiques (1741), frequently reprinted
dittode Mécanique (1743), &c.
dittod'Astronomie (1746); 4th edition augmented by Lalande (1779)
Leçons élémentaires d'optique (in French). Paris: Hippolyte Louis Guérin & Louis François Delatour. 1764. 2nd edition
Calculations by him of eclipses for eighteen hundred years were inserted inL'Art de vérifier les dates byBenedictine historianCharles Clémencet (1750)
He communicated to the Academy in 1755 a classed catalogue of forty two southern nebulae,[15] and gave in t. ii. of hisEphémérides (1755) practical rules for the employment of the lunar method of longitudes, proposing in his additions toPierre Bouguer'sTraité de Navigation (1760) the model of a nautical almanac.
"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.
"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 adCaput 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 byJ. 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 byF. Baily
"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)
"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)
^The traditional birth date of 15 March 1713 has been questioned due to many infants of the Catholic Church being baptised on the day of their birth in the 17th and 18th centuries.[1] His baptism date is 15 December 1713; babies were normally baptised on the day that they were born.[2]
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, 1976ISBN0-86961-068-6
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 byAbbé Carlier, who attached a discourse on La Caille's life.
.JPG)
