DEB 



[127] 



DEC 



scribed by Monticelli and Covelli 

 in their Podromo della Mineralogia 

 Yesuviana, and by them named 

 after Sir H. Davy. It is of a 

 white, or yellowish colour ; trans- 

 parent; translucent, or opaque. 

 Specific gravity 2-4 ; hardness 5 to 

 5-5. 



DEBA'CLE. (Debacle, Fr. Amas de 

 glagons qui arrivent avec impttuosite, 

 dans un dfyel sulit, apr&s qu'une 

 riviere a eU prise long-temps.} A 

 violent torrent or rush of waters, 

 which, overcoming all opposing 

 barriers, carries with it stones, 

 rocks, and other fragments, spread- 

 ing them in all directions. 



DEBOT/CHE. (debouche^ Fr. L'ex- 

 tr6mit& (Fun defile, d'un col de 

 montagnes.) The outlet of a narrow 

 pass. 



DEBE'IS. (debris, "Fi.) The fragments 

 of rocks ; the ruins of strata ; the 

 rubbish, sand, grit, &c., brought 

 down by torrents. 



DECAHE'DRAL. (from Seica, and epa, 

 Gr.) Having ten sides. 



DECAHE'DBON-. A figure which hath 

 ten sides. 



DECA'NDEIA. (from e/ca, and avrjp, 

 Gr. ) A class of plants characterized 

 by having ten stamens ; it includes 

 cassia, ruta, saxifraga, &c. 



DECA'NDEIAN. Belonging to the class 

 Decandria ; having ten stamens. 



DECAPHYLLOUS. (from SeW, and 

 0vXXoi/, Gr.) A calyx which hath 

 ten leaves. 



DECA'PODA. (from &'*, ten, and n-ovs, 

 foot.) The first order of Crustacea. 

 Having the antenniferous region of 

 head confluent with the thorax. 

 This order includes lobster, crab, 

 craw-fish, shrimp, &c. 



DECA'POPAL. Belonging to the order 

 Decapoda; having ten feet. Sy- 

 nonymous with decempedal. 



DECE'MFID. (from decetn and fasus, 

 Lat.) Ten-cleft; in botany, a 

 term for a calyx cleft, or divided, 

 into ten parts. 



DECEMLO'CVLAB. (from decem and 



loculus, Lat.) Ten-celled; in bota- 

 ny, an epithet for a pericarp 

 divided into ten loculi or cells. 

 DECI'DUOTTS. (deciduus, Lat.) 



1. In botany, falling off; plants 

 which lose their leaves in autumn 

 are called deciduous ; applied also 

 to stipules falling in the autumn ; 

 to calcyces falling soon after the 

 expansion of the corolla; and to 

 the corolla when falling with the 

 stamens. 



2. In conchology, to shells having 

 a tendency in the apex of the spire 

 to fall off; to crustaceans, annually 

 casting their shells. 



DECOMPOSE, (decomposer, Fr. Reduire 

 un corps d ses principes, ou stparer 

 les parties dont il est compost.) To 

 resolve a body into its constituent 

 elements ; to overcome the power 

 of affinity, and thereby to separate 

 elementary particles. 



DE'COMPOUND. Doubly compound. 

 Leaves are so called when the 

 petioles, instead of bearing leaflets, 

 branch out into other petioles to 

 which the leaflets are attached. 



DE'CREMENT. (decrementum, Lat.) 

 Gradual waste, or wearing away, 

 as of rocks by the action of water ; 

 gradual diminution. In mineral- 

 ogy, decrement is considered as of 

 two kinds, single and compound. 

 When in crystals the planes de- 

 crease equally to a point, they are 

 said to arise from simple decrement ; 

 but when, as in the pentagonal 

 dodecahedron, the planes do not 

 decrease equally on all sides, the 

 decrement is termed compound. 



DECEE'SCENT. (decrescens, Lat.) Gra- 

 dually becoming less. 



DECU'BEENT. (from decurro, Lat.) 

 Running downwards. Applied to 

 sessile leaves when the base runs 

 down the stem and forms a border 

 or wing; applied also to stipules 

 when extending downwards along 

 the stem. In some plants, as in 

 some of the thistles, the margins of 

 sessile leaves run down on each 



