Sky and Telescope - October 2017 - 37

ity and seriousness of purpose, and he continued to provide
him with support.
Lacaille expected to become a priest. But he was smitten
with mathematics and astronomy, which he began to study
privately. He ﬁnished his theology degree but had no taste for
further religious study. Instead, as a self-taught astronomer,
in 1737 he obtained a recommendation for a position at the
Paris Observatory, which was then under the directorship of
Jacques Cassini, son of Jean-Dominique Cassini (the discoverer of the Cassini Division in Saturn's rings).
Here Lacaille honed his skills and applied them to the
science of geodesy. He helped map the French coast from
Nantes to Bayonne and took a leading role in remeasuring the great meridian of France: the line of longitude from
the North Pole through Paris to the equator. The precision
surveying for this project veriﬁed earlier work showing that
Earth is an oblate spheroid - slightly wider across the equator than from pole to pole - rather than a prolate spheroid
as some had argued.
Lacaille's work gained him election to the Royal Academy
of Sciences in Paris and a post at the Collège Mazarin. There
he established a small observatory, made systematic observations of star positions and parallaxes, and wrote widely read
texts on mathematics, astronomy, and optics. By the late
1730s he had established a solid reputation and a comfortable
future as an academic.
But he sought new challenge, and he found it in the
southern heavens. He proposed to the Academy that he
make an expedition to the Cape of Good Hope to catalog the
southern sky and to make geographical measurements of the
region. On November 21, 1750, Lacaille embarked on the
ship Glorieux, heading ﬁrst to Rio de Janeiro, then tacking
east to South Africa.
On April 19, 1751, Lacaille landed at Cape Town, then a
small way station of the Dutch East India Company. Carrying a letter of introduction from the Dutch Prince of
Orange, he was received warmly by the Dutch governor and
obtained lodging at the home of Jan Bestbier on what is now
Strand Street.
The Dutch found the French astronomer somewhat
reserved but amiable, and they gave him what help and materials they could. In the backyard of Bestbier's home, Lacaille
oversaw the construction of a 12-foot-square observatory for
his instruments and telescopes, which included a 14-footlong refractor for timing the phenomena of Jupiter's moons:
their eclipses and their entries and exits across the planet's
face. The local times of these events, carefully determined,
could be compared against the local times predicted for the
events at the longitude of Paris or London, yielding a means
to determine one's longitude anywhere in the world - ingenious, though fairly crude in practice.
t REPORTING BACK The Starry Southern Sky was Lacaille's initial
report to the astronomical world after he returned to a hero's welcome in
France. It included measures of only the brightest southern stars.

FORNAX

Lacaille's Constellations
◗ Born into the Age of Reason, the industrious and serious-minded Lacaille mostly shunned fanciful names for
his new constellations. Instead, he filled his sky with tools
of the arts and sciences. Most of the bright southern stars
had already been assigned to constellations by Petrus
Plancius and Johann Bayer in the late 16th and early 17th
centuries, so Lacaille's 14 new constellations are quite
dim. They were the final ones created that are still in use.
Here they are with their current, often shortened,
names, and their meanings and the original French
names on Lacaille's first edition of his southern sky map.
Antlia, the Air Pump (la Machine Pneumatique)
Caelum, the Engraver's Tools (les Burins)
Circinus, the Geometer's Compass (le Compas)
Fornax, the Chemist's Furnace (le Fourneau)
Horologium, the Pendulum Clock (l'Horloge)
Mensa, Table Mountain (Montagne de la Table)
Microscopium, the Microscope (le Microscope)
Norma, the Carpenter's Square (l'Équerre et la Règle)
Octans, the Octant (l'Octans de Réﬂexion)
Sculptor, the Sculptor's Workshop (l'Atelier du Sculpteur)
Pictor, the Painter's Easel (le Chevalet et la Palette)
Pyxis, the Mariner's Compass (la Boussole)
Reticulum, the Eyepiece Reticle (le Réticule Rhomboïde)
Telescopium, the Telescope (le Télescope)

In addition, Lacaille divided huge Argo Navis, a survival
from classical times, into three:
Puppis, the Stern
Carina, the Keel
Vela, the Sails
It's no wonder that astronomer Heber Curtis of Lick
Observatory remarked that, when he first saw a map of
the far-southern sky, "It looked like somebody's attic."

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