DEP 



DES 



term relating to the compactness of 

 bodies, and denoting the comparative 

 quantity of matter, in different bodies, 

 ■which is contained under a certain bulk. 

 As gravity is understood to act in propor- 

 tion to the relative quantity of the matter 

 of bodies, their specific gravities are pre- 

 sumed to be the measure of their densi- 

 ties. See Rarity. 



DENTIRO'STRES {dens, a tooth, 

 rostrum, a beak). A group of the In- 

 sessores, or Perching birds, in which the 

 horny covering of the upper mandible is 

 notched or toothed towards the point, as 

 in the shrikes, the thrushes, the warblers, 

 the chatterers, and the fly-catchers. 



DENUDATION {denudo, to make 

 bare). The carrying away, by the action 

 of running water, of a portion of the 

 solid materials of the land, by which in- 

 ferior rocks are laid bare. 



DEONTO'LOGY {6eov, what is due, 

 X670f, an account). The science of duty ; 

 a term applied by the followers of Ben- 

 tham to their system of ethics. 



DEOXIDA'TION. The separation of 

 oxygen from a body ; the reducing a body 

 from the state of an oxide. 



DEPA'RTURE. A nautical term, de- 

 noting the number of miles which a ship 

 has sailed east or west; but more spe- 

 cifically defined to be •' the sum of all the 

 successive elementary meridian distances, 

 when the nautical distance is assumed to 

 be divided into an indefinite number of 

 equal parts." See Nautical Distance. 



DEPHLEGMA'TION. The chemical 

 process of concentration, by depriving 

 a body of water. By phlegma is meant 

 a watery distilled liquor, as distinguished 

 from a spirituous liquor. 



DEPHLOGI'STICATED. That which 

 is deprived of its phlogiston; in modern 

 language, that which is oxidized. The 

 term is derived from the old theory of 

 combustion, in reference to which, oxy- 

 gen gas was called dephlogisticated air; 

 and chlorine, dephlogisticated marine 

 acid. See Phlogiston. 



DEPRESSION, ANGLE OF. The 

 angle by which a line drawn from the 

 eye to any object dips below the horizon. 



DEPRESSION, IN ALGEBRA. The 

 reduction of an equation to a lower de- 

 gree, by dividing both sides of it by a 

 common measure. 



DEPRESSION OF THE HORIZON. 

 Dip of the horizon. In Nautical Astro- 

 nomy, the depression or dipping of the 

 visible horizon below the true horizontal 

 plane, owing to the eye of the observer 

 104 



being placed above the level of the sur- 

 face of the sea. 



DERBYSHIRE SPAR. Fluor-spar, 

 technically called blue- John ; fluate of 

 lime, or a combination of calcareous earth 

 with fluoric acid, found abundantly in 

 Derbyshire. 



DEREB ADIGE. A star of the first 

 magnitude in the northern constellation 

 Cygnus. 



DERIVATION, LAW OF. In finding 

 the successive differential co-efficients 

 of a power of x, the law is, to get the 

 next differential co-efficient, multiply the 

 last by its exponent, and reduce the ex- 

 ponent by a unit. 



DERI'VATIVE WORDS. In Gram- 

 mar, these are words either compounded 

 of two significant words in the language, 

 or of one significant word and a termina- 

 tion which modifies its meaning, as 

 schoolmaster, scholar. They are distin- 

 guished from primitive words, which have 

 no derivation in the language, as school. 



DERMA'PTERA (depyua, skin, wre- 

 p6v, a wing). Ear-wigs; an order of 

 insects, having their anterior pair of 

 wings coriaceous, not employed in flight ; 

 the posterior membranous, only partially 

 covered by the elytra. 



DERME'STID^ {dermestes, from iep- 

 /ia, skin, haQibn, to eat). Skin-eaters ; a 

 family of Coleopterous insects, of the sec- 

 tion Necrophaga of Macleay, named from 

 the genus dermestes, which is well known 

 for its ravages on the preserved skins of 

 animals. 



DE'RMOBRANCHIATA (3ep/ua, 

 skin, /3pa7X'a> giUs)- A family of Gaste- 

 ropods, named from the genus dermato- 

 branchus, and comprising those mollusks, 

 which respire by means of external bran- 

 chiae or gills, having the form of mem- 

 branous plates, filaments, or tufts. 



DE'RMOSKE'LETON {depina, skin, 

 a-aeXerov, skeleton). The hard integu- 

 ment which covers most invertebrate, 

 and some vertebrate animals. 



DERO'SNE'S SALT. A crystalline 

 substance, obtained by treating opium 

 with ether, and also termed narcotine 

 and opiane. ^ 



DESCENDING NODE. That point 

 of a planet's orbit, where it cuts the eclip- 

 tic, proceeding southward, marked £5. 



DESCRIPTION. In Logic, an acci- 

 dental definition, or that which assigns 

 the circumstances belonging to the 

 essence, viz. properties and accidents. 

 See Definition. 



DESPUMA'TION {despumo, to scum). 



