DIG 



DICE 



DIFFUSION VOLUME. A term 

 adopted to express the different dispo- 

 sition of gases to interchange particles ; 

 the diffusion-volume of air being 1, that 

 of hydrogen gas is 3-83. 



Diffusion Tube. An instrument for 

 determining the rate of diffusion for dif- 

 ferent gases. It is simply a graduated 

 tube, closed at one end by plaster of 

 Paris, a substance, when moderately dry, 

 possessed of the requisite porosity. The 

 diffusion of gases, as thus conducted, 

 closely corresponds with the endosmosis 

 of liquids, which occurs under similar 

 circumstances. 



DIGA'MMA. Double gamma. In some 

 parts of Greece, the old Greek 7 was a 

 kind of aspirate, called, from the way 

 of writing it (/), digamma. This aspi- 

 rate was carried by the Pelasgian race 

 into Italy, and remained in Latin as a 

 real consonant V, vau. It supplies the 

 data for resolving those cases of metrical 

 difficulty, where the lengthening of a 

 short syllable uniformly takes place be- 

 fore particular words. 



DIGE'STER. A strong vessel of cop- 

 per or iron, with an air-tight lid, for 

 preventing the loss of heat by evapo- 

 ration. 



DIGE'STION {digero, from diversim 

 gero, to carry into different parts). In 

 Physiology, the change of the food into 

 chyme, and the absorption and distribu- 

 tion of the more nutritious parts, or the 

 chyle, through the system. In Chemistry, 

 the continued action of a solvent upon 

 any substance. 



DIGESTIVE SALT. A salt discovered 

 by Sylvius, since named muriate of 

 potash, and now chloride of potassium. 



DI'GIT {digitus, a finger). An old 

 measure of a finger's breadth. In Astro- 

 nomy, it denotes the twelfth part of the 

 diameter of the sun or moon, and is used 

 to express the quantity of an eclipse: 

 thus the moon is said to be six digits 

 eclipsed, when half of her face is covered 

 by the earth's shadow. In Arithmetic, 

 a digit is any symbol of number from 

 0to9. 



DI'GITATE {digitus, a finger), A term 

 applied to that kind of expansion, in 

 which the parts are spread out into 

 finger-shaped processes, as in the outer 

 lip of the scorpion strombi. 



DIGITI'GRADA {digitus, a toe, gra- 

 dior, to walk). A division of the terres- 

 trial Carnivorous animals, which walk 

 upon their toes, and bound along with 

 considerable elasticity and swiftness, as 



the weasel, the civet, the hyena, and the 

 cat tribes. See Plantigrada. 



DIGY'NIA (dif, twice, '^wt], a woman). 

 The name of those orders of plants 

 in the system of Linnaeus, which are 

 characterized by the presence of two 

 pistils. 



DILE'MMA {hiXnixna, a double pro- 

 position ; from di?, twice, and Xa/x- 

 ySdi/o), to take). In Logic, a complex kind 

 of conditional syllogism, having more 

 than one antecedent in the major pre- 

 miss, and a disjunctive minor. In other 

 words, it is a complex conditional reasont 

 ing, in which either one of the antece- 

 dents must be admitted, or one of the 

 consequents must be denied. 



The expression, horns of a dilemma, 

 relates to the taking hold of both ways : 

 if a person is not caught by the one 

 antecedent or consequent, he must be 

 caught by the other. 



DILU'VIUM {diluo, to wash away). 

 Accumulations of gravel and loose mate- 

 rials, which are said to have been pro- 

 duced by the action of a diluvian wave 

 or deluge sweeping over the surface of 

 the earth. 



DIME'NSION. In Algebra, a term 

 synonymous with degree ; thus x'^y is of 

 three dimensions, or of the third degree. 

 In Geometry, length is of one dimension, 

 surface of two, solidity of three; hence, 

 geometry of three dimensions is another 

 term for solid geometry. 



DI'MERA (6if, twice, /uepo?, apart). 

 A section of Homopterous insects, in 

 which the tarsi are two-jointed, as in the 

 Aphidae. 



DIMO'RPHOUS (3ir, twice, noptprj, 

 form). A term applied to some natural 

 and to some artificial productions, which 

 occur in two distinct forms. For ex- 

 ample : arragonite and carbonate of lime 

 are chemically the same, though belong- 

 ing to different primary forms ; and the 

 crystals of sulphate of nickel, if de- 

 posited from an acid solution, are square 

 prisms ; but if from a neutral solution, 

 they are right rhombic prisms. This 

 property of assuming two incompatible 

 forms, is called dimorphism. 



DIMYA'RIA (aJf, twice, }xv^, a mus- 

 cle). A general name for those bivalves 

 whose shells are closed by two ad- 

 ductor muscles distinct and widely re- 

 moved from each other, as in the mussel. 

 See Monomyaria. 



DICE'CIA (6t?, twice, ot/cor, a house). 

 The twenty-second class of plants in 

 Linnseus's system, in which the stamens 



