effected only by
catamarans and flat-bottomed surf-boats. The north-east monsoon, which
lasts from October till April, is exceedingly violent for three months
after its commencement. From April till October hot southerly winds blow
by day; at night the heat is tempered by sea-breezes. The principal
places frequented by shipping are Pulicat, Madras, Sadras, Pondicherry,
Cuddalore, Tranquebar, Nagore, and Negapatam. The name Coromandel is
said to be derived from _Cholamandal_, the mandal or region of the
ancient dynasty of the Chola. Its official use has lapsed.

CORONA (Lat. for "crown"), in astronomy, the exterior envelope of the
sun, being beyond the photosphere and chromosphere, invisible in the
telescope and unrecognized by the spectroscope, except during a total
eclipse (see SUN; ECLIPSE).

_Corona Borealis_, also known as the _Corona septentrionalis_, and the
Northern Crown or Garland, is a constellation of the Northern
hemisphere, mentioned by Eudoxus (4th cent. B.C.) and Aratus (3rd cent.
B.C.). In the catalogues of Ptolemy, Tycho Brahe, and Hevelius, eight
stars are mentioned; but recent uranographic surveys have greatly
increased this number. The most interesting members are: [sigma]
_Coronae_, a binary consisting of a yellow star of the 6th magnitude,
and a bluish star of the 7th magnitude; _R Coronae_, an irregular
variable star; and _T Coronae_ or _Nova Coronae_, a temporary or new
star, first observed in 1866. _Corona Australis_, also known as _Corona
meridionalis_, or the Southern Crown, is a constellation of the Southern
hemisphere, mentioned by Eudoxus and Aratus. In Ptolemy's catalogue
thirteen stars are described.

In physical science, coronae (or "glories") are the coloured rings
frequently seen closely encircling the sun or moon. Formerly classified
by the ancient Greeks with halos, rainbows, &c., under the general group
of "meteors," they came to receive considerable attention at the hands
of Descartes, Christiaan Huygens, and Sir Isaac Newton; but the correct
explanation of coronae was reserved until the beginning of the 19th
century, when Thomas Young applied the theories of the diffraction and
interference of light to this phenomenon. Prior to Young, halos and
coronae had not been clearly differentiated; they were both regarded as
caused by the refraction of light by atmospheric moisture and ice,
although observation had shown that important distinctions existed
between these phenomena.