COROMANDEL COAST

coromandel coast, a name formerly applied officially to the eastern seaboard of india approximately between cape calimere, in 10° 17' n., 79° 56' e., and the mouths of the kistna river. the shore, which is low, is without a single good natural harbour, and is at all times beaten by a heavy sea. communication with ships can be 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. thus, while halos have certain definite radii, viz. 22° and 46°, the radii of coronae vary very considerably; also, halos are coloured red on the _inside_, whereas coronae are coloured red on the _outside_ (see halo). it has now been firmly established, both experimentally and mathematically, that coronae are due to diffraction by the minute particles of moisture and dust suspended in the atmosphere, and the radii of the rings depend on the size of the diffracting particles. (see diffraction of light.) other meteorological phenomena caused by the diffraction of light include the _anthelia_, and the chromatic rings seen encircling shadows thrown on a bank of clouds, mist or fog. these appearances differ from halos and coronae inasmuch as their centres are at the anti-solar point; they thus resemble the rainbow. the anthelia (from the greek [greek: anti], opposite, and [greek: helios], the sun) are coloured red on the inside, the outside being generally colourless owing to the continued overlapping of many spectra. the diameter increases with the size of the globules making up the mist. the chromatic rings seen encircling the "spectre of the brocken" are similarly explained. the blue colour of the sky (q.v.), supernumerary rainbows, and the gorgeous sunsets observed after intense volcanic disturbances, when the atmosphere is charged with large quantities of extremely minute dust particles (e.g. krakatoa), are also explicable by the diffraction of light. (see dust.) see e. mascart, _traite d'optique_ (1899-1903); j. pernter, _meteorologische optik_ (1902-1905). in architecture, the term "corona" is used of that part of a cornice which projects over the bed mould and constitutes the chief protection to the wall from rain; it is always throated, and its soffit rises towards the wall. the term is also given to the apse or semicircular termination of the choir; as at canterbury in the part called "becket's crown." the large circular chandelier suspended in churches, of which the finest example is that given by barbarossa to aix-la-chapelle, is often called a corona. the term is also used in botany of the crown-like appendage at the top of compound flowers, the diminutive being _coronule_. coronach (a gaelic word, from _comh_, with, and _ranach_, wailing), the lamentation or dirge for the dead which accompanied funerals in the highlands of scotland and in ireland. the more usual term in ireland is "keen" or "keening."