DEI 



DUD 



DRIFT. " All those coarse and some- 

 times far transported materials, to 

 which some geologists apply the 

 word diluvium, I," says Sir R. 

 Murchison, " to avoid misconstruc- 

 tion, designate drift. Diluvium, 

 as used by M. Elie de Beaumont 

 and the modern foreign geologists, 

 means precisely what I term drift. 

 Geologists having now completely 

 ascertained that each region of the 

 earth has its own superficial diluvia, 

 produced by distinct and separate 

 action, the unambiguous word drift 

 is proposed, which when preceded 

 by the name of the tract whence 

 the materials were derived, ex- 

 presses at once the intended mean- 

 ing. Hence Silurian drift, Northern 

 drift, Scandinavian drift, &c., &c." 

 Sir R. Murchison. Silurian System. 



DRUPE, (drupce, Lat. /w7re7n)s, Gr.) 

 A pulpy pericarp, or seed-vessel, 

 containing a single hard and bony 

 nut, to which it is attached : the 

 epicarp and sarcocarp separable from 

 each other, and from the endocarp, 

 which is stony; the nectarine, 

 peach, apricot, &c., furnish us with 

 familiar examples. 



DRUPA'CEOUS. 



1 . Having the characters of a drupe, 

 as drupaceous fruit. 



2. Bearing drupes, as drupaceous 

 trees. 



DRUSE. A hollow space in veins of 

 ore, generally lined with crystals. 



DRUSY. This word says Phillips, 

 " has been adopted from the Ger- 

 man term drusen, for which we 

 have no English word. The sur- 

 face of a mineral is said to be 

 drusy when composed of small 

 prominent crystals, nearly equal in 

 size; it is often seen in iron 

 pyrites." 



DUCT, (ductusy Lat.) A tube, canal, 

 or passage through which anything 

 is conveyed. 



1. In anatomy the ducts are very 

 numerous ; thus we have the cystic 



duct, the hepatic duct, the nasal 

 duct, &c., &c. 



2. In botany, ducts are membra- 

 nous tubes, having their sides dotted 

 or barred; they are large enough 

 to be visible to the naked eye, and 

 are plainly seen when a cane, or 

 vine-branch, is cut across. 



DU'CTILE. (ductilis, Lat. ductile, Fr. 

 duttile, It.) That may be drawn 

 out into greater length without 

 breaking. The term is applied to 

 metals only, and is sometimes con- 

 founded with malleable, whereas 

 the two have very different signifi- 

 cations ; thus copper is both malle- 

 able and ductile, but lead is only 

 malleable and not ductile; some 

 metals are neither malleable nor 

 ductile, but brittle, as antimony, 

 manganese, tellurium, &c., &c. 



DUCTI'LITT. (ductilite, Fr. duttilitci, 

 It.) That property which metals 

 possess of being drawn out into 

 greater length with diminished 

 thickness, without separation of 

 parts. The French use the word 

 ductilite to express malleability; 

 but we do not. "La ductilite est 

 un synonyme de malleabilite." 

 Diet. De 1} Acad. Frangoise. 



DUDLEY ROCKS. Called also Wenlock 

 Rocks. A marine formation, com- 

 posing one of the divisions of 

 the Silurian system. The Dud- 

 ley rocks have been sub -divided 

 into Dudley limestone, a mass 

 of highly concretionary grey 

 and blue subcrystalline limestone ; 

 and Dudley shale, an argillaceous 

 shale, of a liver or dark grey 

 colour, rarely micaceous, with no- 

 dules of earthy limestones. Amongst 

 the organic remains contained in 

 the Dudley rocks may be enume- 

 rated corals and crinoidea, in great 

 abundance ; trilobites, &c., &c. 



DUDLEY FOSSIL. } Names given to 



DUDLEY TRILOBITE. ) that species of 

 Calymene named by M. Ad. Brong- 

 niart C. Blumenbachii. This spe- 

 cies has obtained the name of 



