Cal·ci·um n.  Chem. An elementary substance; a metal which combined with oxygen forms lime. It is of a pale yellow color, tenacious, and malleable. It is a member of the alkaline earth group of elements. Atomic weight 40. Symbol Ca.
 Note: ☞ Calcium is widely and abundantly disseminated, as in its compounds calcium carbonate or limestone, calcium sulphate or gypsum, calcium fluoride or fluor spar, calcium phosphate or apatite.
 Calcium light, an intense light produced by the incandescence of a stick or ball of lime in the flame of a combination of oxygen and hydrogen gases, or of oxygen and coal gas; -- called also Drummond light and lime light.
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 Drum·mond light  A very intense light, produced by turning two streams of gas, one oxygen and the other hydrogen, or coal gas, in a state of ignition, upon a ball of lime; or a stream of oxygen gas through a flame of alcohol upon a ball or disk of lime; -- called also oxycalcium light, or lime light.
 Note: ☞ The name is also applied sometimes to a heliostat, invented by Drummond, for rendering visible a distant point, as in geodetic surveying, by reflecting upon it a beam of light from the sun.
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