quadrants Observational instruments consisting of a
quarter circle, the curved edge of which is graduated from
0 °to 90°, and which is fitted with a movable sight and
plumb line. It was first proposed by Ptolemy who recog-
nized that an arc was easier to graduate than a full circle.
Quadrants reappeared in Western astronomy in the 16th
century when astronomers, such as Tycho BRAHE, first
began to appreciate the serious inaccuracies in the avail-
able planetary tables. Accordingly in 1568 he designed a
19-foot oak quadrant divided into 5400 minutes. When he
moved to Uraniborg some years later he designed for his
own use a seven-foot mural quadrant. As the fixed posi-
tion of such an instrument could be unduly restrictive
Brahe also built a rotatable quadrant mounted on a pillar.
Such large instruments, however, tended to warp if made
of wood or suffer from thermal expansion if made of
metal. Small quadrants, on the other hand, proved diffi-
cult to graduate accurately. Suitably modified, the basic
quadrant also found use among surveyors, navigators, en-
gineers, and gunners. A specialized form, Gunter’s quad-
rant, was described by Edmund Gunter (1581–1626) in
his De sectore et radio (1623). Also known as the astrolabe
quadrant, it allowed, in the manner of ASTROLABES, the
time to be determined.
Quarton, Enguerrand (Enguerrand Charton, En-
guerrand Charonton) (c. 1410–c. 1461) French painter
Virtually nothing is definitely known of Quarton’s life ex-
cept that he came from the area of Laôn in northern
France and was active in Avignon in the period 1447–61.
Like his contemporary Nicolas FROMENT, he shows the in-
fluence of both Italian and Flemish art in the two works
definitely attributable to him: the deeply moving Avignon
Pietà (1452; Musée Condé, Chantilly) with SS. John and
Mary Magdalene and donor, and the magnificently cosmic
Coronation of the Virgin altarpiece (1453–54; Villeneuve-
les-Avignon), the details of which were specified in the ex-
traordinarily minute commission from the donor.
Quattrocento (Italian, “four hundred”) The period of
artistic and cultural development in Italy during the 15th
century. Beginning with the competition to design the
baptistery doors in Florence in 1401 and ending with the
election of Pope Julius II in 1503, this period saw the re-
vival of classical ideals in Italian culture and a flowering of
scholarship and the visual arts. Leading figures of the
time, who prospered in such artistic centers as Florence,
Rome, Naples, Ferrara, Venice, and Padua, included
BOIARDOin literature, BRUNELLESCHI, ALBERTI, the elder
SANGALLO brothers, and FILARETE in architecture, DO-
NATELLO, GHIBERTI, and DELLA ROBBIAin sculpture, and
MASACCIO, UCCELLO, Fra ANGELICO, BOTTICELLI, the
BELLINIfamily, PIERO DELLA FRANCESCA, and MANTEGNAin
painting.
Quercia, Jacopo della (c. 1374–1438) Italian sculptor
Born in Siena, Quercia was an unsuccessful candidate for
the first set of doors for the baptistery in Florence (1401),
later executed by GHIBERTI. His earliest surviving work is
the marble tomb of Ilaria del Carretto (c. 1406) in the
cathedral of Lucca, in which elements of both classical
and Gothic styles are combined. Subsequent works in-
clude the statue of the Virgin and Child in Ferrara (1408;
Museo dell’ Opera del Duomo), marble reliefs in the
Trenta chapel at San Frediano in Lucca (c. 1413–22) and
the Fonte Gaia for the Piazza del Campo in Siena
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