METEORS, ETC. 115 



Auro'ra Austra'lis. — A phenomenon, corresponding to the 

 aurora borcalis, seen in the Soutlieru hemisphere, tlie 

 streams of lijiht ascending in the same manner from near 

 the southern horizon. 



Aurora Borea'lis. — A nocturnal luminous meteor, supposed 

 to be electrical. It consists of white or variously colored 

 mellow light, and exhibits various and changing forms and 

 appearances, which sometimes cover the whole heavens. 



Clouds. — For names of clouds, see Clouds. 



Coro'na.^A circle, usually colored, around a luminous body, 

 as the sun or moon. 



Corposant. — A name given by seamen to a luminous appear- 

 ance, supposed to be electrical, often beheld, in dark, tem- 

 pestuous nights, about the decks and rigging of a ship, 

 but particularly at the mast-heads and yard-arms. 



Fa'ta Morga'na. — A meteoric phenomenon, nearly allied to the 

 mirage, witnessed in the Straits of Messina, between the 

 coasts of Calabria and Sicil}^ and occasionally, but rarely, 

 on other coasts, and consisting in the appearance in the air 

 over the surface of the sea of multiplied images of objects 

 on the surrounding coasts. 



Fog. — A dense vapor near the surfoce of land or water. 



Hail. — Moisture precipitated from the atmosphere in the form 

 of ice. The concretions of ice are usually more or less 

 spherical, constituting hail-stones, but sometimes consist of 

 plates or laminae, or of agglomerated masses. 



Hoar-Frost. — The white particles formed by the congelation 

 of dew. 



Hydrome'teors (Gr. hndOr, water, and metron, measure). — 

 Meteors or atmospheric phenomena dependent upon the 

 vapor of water ; a general term for the whole aqueous 

 phenomena of the atmosphere, as rain, snow, hail, etc. 



Ig'ms-Fat'uus. — A meteor or light that appears in the night 

 over marshy grounds, supposed to be occasioned by the 

 decomposition of animal or vegetable substances, or by 

 some inflammable gas ; vulgarly called Will-ivith-the-ivisp^ 

 and Jack-icitli-a-lautern. 



Lightning. — A sudden flash of light in the atmosphere, and 

 commonly disappearing in the same instant ; sometimes 

 attended with clouds and thunder. 



Mirage'. — An optical illusion arising from an unequal refrac- 

 tion in the lower strata of the atmosphere, and causing 



