COL 



COM 



base ; adjective, when they require a base 

 for that purpose. 



COLPE'NCHYMA (koXttov, a loose 

 fold, e'YxwMci. infusion). A term applied 

 by Morren to the sinuous form of the 

 parenchyma of plants. 



COLUBE'RIDiE [coluber, a snake). 

 A family of Ophidian reptiles, including 

 the Boa Constrictors of the New World 

 and the Pythons of the Old, and other 

 non-venomous snakes not belonging to 

 the other families of the order. 



COLU'MB A NO'ACHI. Noah's Dove ; 

 a modern southern constellation, consist- 

 ing of ten stars, close to the hinder feet 

 of Canis Major. 



COLUMBE'LLlNiE. Dove-shells; a 

 sub-family of the Slrombidce, or Wing- 

 shells, named from the typical genus 

 columbella ; these are small shells, with 

 sharp-pointed spires ; the outer lip is 

 thick, turned inwards, more or less 

 toothed on its edge, and gibbous above ; 

 there are also tuberculated teeth at the 

 base of the inner lip, but no regular 

 plaits. 



COLU'MBID^ {columba, a dove or 

 pigeon). The Pigeon tribe; a group 

 of the RasoreSf or Scratching birds, 

 chajacterized by the double dilatation 

 of the crop, and their habit of feeding 

 their young with food disgorged from 

 this receptacle. Macgillivray considers 

 that the Pigeons belong neither to the 

 Rasores nor to the Insessores, but appear 

 to form an order separated by well- 

 defined limits. See Gemitrices. 



COLUMBIUM. Another name for the 

 metal tantalum, from its having been 

 brought, as it is said, from Massachusetts 

 in North America. By fusion of its ore, 

 or columbite, an acid is obtained, called 

 columbic acid. 



COLUME'LLA (dim. of columna, a 

 pillar). A little pillar ; the internal sup- 

 port of most spiral shells, round which 

 the whorls are convoluted. In botany, 

 it denotes the axis from which the valves 

 of a fruit separate, on dehiscence ; the 

 axis which occupies the centre of the 

 sporangium of mosses, &c. 



COLU'MNA. A column ; a term ap- 

 plied, in botany, to the solid body formed 

 by a combination of the filaments, as in 

 stapelia, rafflesia, &c. 



COLURES (KoAoi/pop, a truncated tail). 

 An old term employed in Astronomy to 

 designate two great circles of the sphere, 

 which pass, the equinoctial colure through 

 the equinoctial points and the poles of 

 the equator, the solstitial colure through 

 85 



the solstitial points and the poles of the 

 ecliptic and of the equator. 



COLY'MBID^ {colymbus, a diver). 

 The Divers ; a small family of the Nata- 

 tores, or Swimming birds, characterized 

 by remarkably short wings, and a length- 

 ened, strong, straight bill. 



CO'MA. Literally, hair ; and hence 

 applied to the assemblage of branches 

 which forms the head of a forest tree. 

 Cyma is sometimes employed, though 

 erroneously, to express the same thing. 



COMA BERENI'CES. Berenice's 

 Hair ; a modern northern constellation, 

 consisting of forty-three stars, and named 

 after the wife of Ptolemy Euergetes. 



COMBINATIONS. In Algebra, the 

 combinations of any number of quan- 

 tities are the different sets which can be 

 made of them, taking a certain number 

 together, without regard to the order in 

 which they are placed. Thus, the com- 

 binations of a, b, c, d, taken 3 together, 

 are abc, abd, acd, bed. 



COMBINATION, CHEMICAL. The 

 union of the particles of different sub- 

 stances, by chemical attraction, in form- 

 ing new compounds. See Atomic Weights. 



COMBINING QUANTITY. Various 

 terras have been proposed for expressing 

 the combining quantities of elementary 

 and compound substances, and all ob- 

 jectionable. Atom is not only hypotheti- 

 cal, but often inapplicable, as when half 

 atoms occur. Equivalent is only expres- 

 sive when comparison with a correlative 

 equivalent is directly implied. Proportion 

 means similitude of ratios. Proportional 

 is one of the terms of a proportion. 

 Combining quantity or weight is some- 

 times expressive ; but, besides being 

 unwieldy, it is not always applicable. 

 Dr. Donovan adds, the word dose is 

 universally employed to designate a de- 

 terminate or definite quantity of a thing 

 given; it has the quality of involving 

 nothing beyond a fact, and can often be 

 used with advantage. 



COMBU'STIBLE. A body which, in 

 rapid union with other bodies, disengages 

 heat and light. Simple combustibles are 

 hydrogen, carbon, boron, sulphur, phos- 

 phorus, nitrogen, and the metals ; com- 

 pound combustibles are the hydrurets, 

 carburets, sulphurets, phosphorets, me- 

 tallic alloys, and organic products. 



COMBU'STION {comburo, to burn to- 

 gether). The act of burning ; a pheno- 

 menon produced by the chemical combi- 

 nation of two substances, attended by the 

 development of heat and light ; it usually 



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