D I S 



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D D 



crust of the same geological age 

 range in lines parallel to one and 

 the same great circle of the sphere ; 

 those of different ages are parallel 

 to different circles. The geological 

 era, consequently, of the elevation 

 of mountains, may be ascertained 

 from the direction of their axes of 

 movement. 



DISPE'EMOUS. (from ts, and mrcpfia, 

 Gr.) Two-seeded ; an epithet for 

 fruit containing two seeds only; 

 stellate and umbellate plants are 

 thus termed. 



DISSE'PIMENT. (dissepimentum, Lat.) 

 In botany, the partition which 

 divides a capsule into cells. In 

 many plants the dissepiments do not 

 reach to the axis or centre, in some 

 plants the dissepiments are not 

 formed, or subsequently disappear, 

 and leave the placenta in the centre 

 of the ovarium, like a column, with 

 the seeds adhering to it. 



DI'STHENE. | Disthene is the 



DI'STHEN-SPATH. ) name given by 

 Haiiy, and Disthen-spath by Mohs, 

 to the mineral Kyanite or Cyanite, 

 which last, see. 



DISTICHOPOBA. A genus of fora- 

 minated polypifers, established by 

 Lamarck. Mr. Parkinson thus 

 describes it: "A stony, solid, fixed, 

 ramose, and rather compressed 

 polypifer. The pores unequal and 

 marginal, placed on the two oppo- 

 site edges, in longitudinal rows, 

 and in the form of sutures ; stelli- 

 form, wart-like, projections are 

 scattered on the surface of the 

 branches." 



DI'STICHOUS. (bla'Ti'xo's, Gr. distichum, 

 Lat.). Two -ranked ; applied to 

 leaves occupying two sides of a 

 branch, but not regularly opposite 

 at their insertion, as the fir, yew, 

 &c. ; applied also to branches when 

 they spread into two horizontal 

 directions ; and to flowers, placed 

 in two opposite ranks. 



DI'TEUPA PLA'NA. A species of ptero- 

 podous mollusk, formerly called 



Dentalium planum; found in the 

 lowest tertiary strata, especially 

 on the western coast of Sussex. 



DIVERGING. In botany, applied to 

 the position of leaves during sleep, 

 signifying that the leaflets approach 

 at their base, and are open at their 

 summits. 



DODE'CAGON. (from Su&eica and <yoWa, 

 Gr. dodecagone, Fr. dodecagono, It.) 

 A regular polygon having twelve 

 equal sides and angles. 



DODECAHE'DEON. (from SivSeKa, twelve, 

 and e8pa, base, Gr.) A geometrical 

 solid, comprehended under twelve 

 equal sides, each whereof is a 

 pentagon. It is one of the regular 

 or plutonic bodies. 



DODECAHE'DEAL. Having twelve equal 

 sides ; relating to a dodecahedron. 



DODECAHE'DEAL COEUNDUM. Called 

 also Spinel ; the Spinelle and Pleo- 

 naste of Haiiy. There are two 

 varieties, the Ceylanite and Spinel 

 Ruby. Colours red, blue, brown, 

 black, green, and white. It con- 

 sists of alumina 74, silica 1 6, mag- 

 nesia 8, oxide of iron one and a 

 half, and lime 075 per cent. 



DODECAHE'DEAL GAENET. A species of 

 garnet containing ten sub-species 

 or varieties ; these are the Grossul- 

 laire, or asparagus-green variety; 

 the Pyrenaite, or greyish-black 

 variety ; the Colophonite, or red 

 variety in granular concretions; 

 the Precious Garnet, or highly 

 crystallized and transparent red 

 variety ; the Topazolite, or yellow 

 variety; the Melanite, or velvet- 

 black opaque variety ; the Allo- 

 chroite, or brown, green, and grey 

 massive variety; the Pyrope, or 

 deep blood-red variety ; the Esso- 

 nite, or hyacinthine and orange- 

 yellow variety; the Common Garnet, 

 or brown and green variety, in gran- 

 ular concretions and translucent. 



DODECAHE'DEAL MEECUEY. Called 

 also native amalgam, the Mercure 

 Argental of Haiiy. A mixture of 

 mercury and silver in the propor- 



