DEC 



DEC 



DA'VITE. A fibrous sulphate of alu- 

 mina, found in a warm spring near Bo- 

 gota in Columbia. 



DAY. In common language, the in- 

 terval of time which elapses between the 

 rising and the setting of the sun ; this is 

 called an artificial day. 



1. The civil day begins at twelve 

 o'clock at midnight, and lasts till the 

 same hour of the following night. It is 

 counted in two portions of twelve hours 

 each, viz. from midnight to noon, and 

 from noon to the succeeding midnight. 



2. The astronomical or solar rfay begins 

 at noon, and is counted up to twenty-four 

 hours, terminating at the succeeding 

 noon. This mode of reckoning the day 

 is employed in the Nautical Almanac, 

 and may lead to mistakes with persons 

 not familiar with this mode of computa- 

 tion. Thus, January 10, fifteen hours, in 

 astronomical time, is January 11, three 

 in the morning, civil time. 



3. The sidereal day is the time which 

 elapses between that of a star being in 

 the meridian of a place to the moment 

 when it arrives at the meridian again. 

 This period is always the same, not being 

 affected by the motion of the earth in her 

 orbit, as the solar day is. The sidereal 

 day is about four minutes less than the 

 mean solar day. 



DEBA'CLE {debacler, to unbar, to 

 break up as a river after a long frost). 

 A great rush of waters which, breaking 

 down all opposing barriers, carries for- 

 ward the broken fragments of rocks, and 

 spreads them in its course. 



DE'CAGON (3eKa, ten, ^Mvm, an 

 angle). A geometrical figure, having ten 

 sides and consequently ten angles. If 

 the sides and angles are all equal, the 

 figure is a regular decagon, and may be 

 inscribed in a circle. 



DECAGY'NIA (deVa, ten, '^vvij, a wo- 

 man). The designation of those orders 

 of plants in the Linnaean system, which 

 are characterized by the presence of ten 

 pistils. 



DECA'NDRIA (5e/ca, ten, Uv\]p, a 

 man). The tenth class of plants in the 

 Linnaean system, characterized by the 

 presence of ten stamens. 



DECANTA'TION. The act of pour- 

 ing off clear fluid from sediment, or from 

 suspended impurities,— a method some- 

 times adopted to avoid the use of filters, 

 which might be destroyed by an acid or 

 alkaline solution. 



DECA'PODA (3e(<a, ten, ttoup, 7ro36f, a 

 foot). The highest order of the Crus- 

 101 



tacea, which have ten ambulatory feet, 

 the cephalic, thoracic, and pro-abdominal 

 segments united, and the branchiae con- 

 cealed under the sides of the carapace, as 

 seen in the astacus fluviatilis. 



DECA'RBONIZA'TION. The process 

 of depriving a body of its carbon ; as em- 

 ployed, artificially, for converting cast 

 iron into malleable iron ; and, in nature, 

 in removing the superfluous carbon of 

 the seed in the function of germination. 



DECI'DUOUS {decido, to fall off). 

 Falling off; a term applied to any thing 

 which falls off in a certain stage of 

 growth, as the terminal whorls of the 

 pupaform land-shells, the petals and se- 

 pals of certain flowers, &c. The term is 

 synonymous with caducous, and opposed 

 to persistent, which denotes permanence. 



DE'CIMAL {decimus, the tenth). A 

 fraction whose denominator is 10, or 

 some power of 10, as 100, 1000, &c. In- 

 stead, however, of writing the denomi- 

 nator under the numerator, as in vulgar 

 fractions, it is expressed by pointing off, 

 from the right of the numerator, as many 

 figures as there are cyphers in the deno- 

 minator ; thus, '2, "23, '127, signify 

 respectively fo' 1^. T^- 



DECLE'NSION {declino, to deflect). 

 In Grammar, the deriving of the cases 

 of nouns from one another ; the changes 

 of termination corresponding to the vari- 

 ous relations in which the subject is con- 

 ceived to stand. 



DE'CLINATE {declino, to bend down- 

 wards). Bent downwards ; as applied to 

 the stamens of plants when they all bend 

 to one side, as in amaryllis. 



DECLINATION {declino, to bend). 

 The distance from the equator of the 

 parallel described by a star ; it is counted 

 from up to 90 degrees, and is austral 

 or southern, boreal or northern, in refer- 

 ence to the equator. Declination on the 

 celestial globe corresponds with latitude 

 on the terrestrial; and the parallels of 

 declination are similar to the parallels of 

 latitude. 



1. Declination circZe* are small circles 

 of the sphere, parallel to the equator, in 

 which the stars perform their apparent 

 diurnal revolution. 



2. Declination of the magnetic needle 

 is the angle which the horizontal needle 

 makes with the geographical meridian of 

 any given place. 



DECO'LLATED (decollo, to behead). 

 A term applied to those univalve shells 

 in which the apex or head is worn off in 

 the progress of growth. 



