DERMATOPHYTES. 148 DERRICK. inlinl>iting the cuticle or epidermis, and giving ri»f tti .'■iiiiie forms of skin disease?, as laviis, jiilNiiasi^. iiii;: ini 1 1|"|.. i . i*li-. DEBMESTID BEETLES (fJk. ^^p^ul, der- ma, skin + i<T0l(iv, cslliii III. to eat. literally 'skin-eater'). A family ( Derniestida? ) of small or moderately sized and very destructive beetles. Both the adults and the larv;p feed on a variety of animal and ve-retable substances, niakin" them museum and household pests, preserved meals, woolens, furs, feathers, silk, and even <lru;;s beinj; exposed to their depredations. The adults, which are oval or elongate and vari- colored, feign death when disturbed, falling to the ground, ventral surface upward, and lying stilT with folded legs. The adults inaj- fre- quently be found outdoors on Mowers, and on the windows of infested houses. The lar:c, which are short and woolly or fuzzy, do far more damage than the adults. There are .3(10 to 400 species in the family. The most common of them in the Lnited States are the larder or bacon beetle (see B.cox-liEETUCl . the carpet-beetle (q.v.). the museum pest, and the raspberry-worm tmi-v.). One form lives on cobwebs, feeding perhaps on the remains of insects caught there, and possibly on the web itself. Species of the genus Attagenus are responsible for a curious and beautiful kind of felting, resembling mole- skin, of pillows and bed-ticks, which often puzzles housekeepers. The fumes of carbon bisulphide, applied in a tight indosure, arc fatal both to the beetle and the larvip. Carbon bisulphide, how- ever, is very explosive, and its fumes are harm- ful to man, and hence it should be used with caution. Benzine and naphtha are helpful in keeping these pests from entering stored goods. DERNA. dcr'na. or DERN. A town of Barca, Northern .frica. situated at the mouth of a ravine, one mile from the Mediterranean (Map: Africa. Tripoli, G 1). In ISO.i it was captured by a force of natives and Americans, led by Gen- eral Eaton. Population, estimated at 3500. DERNBTJRG, dcrnliriTTrK, Hki.nricii (1820—). A (Mriiiaii legal scholar, born in .Mainz. lie was educated at the universities of Heidelberg and Giessen, was appointed a professor at Zurich in 1852, and at Halle in 1802. In 187;i he became professor of Koman law and Prussian common law at Berlin. He represented the I'niversity of Halle in the Prussian I'pjxM- House from 18(i0. and the University of Berlin from 187.1. His publications include: Die Instilutioiicn drs flajiis < ISIill). and a l.chrbuch dcs prfuxsischeii Privat- rrrhls C! vols.. 1871-80; 5th ed. 1893 ct scq.), his most important work. DE ROSNY, dc rA'ny, Ltox. See RosNV, DEROULEDE, d.lroo'lftd'. Pail (184C— ). An cnlhusiastlc but narrowly chauvinistic lrcnch poc't and political agitator, born in Paris. He is the author of the very popular Chants du noldnt (1872(: yoiixeaiix rhniils du soldat (1875); Hrfrains mililaires (1888); Chants du jtnil-ian (18!)4): and /WviVs niilitnirrs (1800). Pi'roulMe has al~o written a patriotic cantata, 1'irc In Frnnrr (1880): a religious dranui. l.a Miinliilr (18801 ; and a patriotic play, l.'llrlman (1S77). Kccent patriotic historii'al works are Mrxsirr du (liirsrUn (1S<15) and I.n mort dc llnrhr (1807). ^)^'•ronl^dc or^'anizeil a I^eapue of Patriots, and as its presiilent was so indis- creet as almost to involve France in war with Germany. He was thrice elected to the Chamber ol Deputies, and was conspicuous in agitation against the Kepublic and the .lews, overstepping the bounds both of i)ropriety and of law. For re- jx-ated insults to the President, he was coni- demui.-d to sutler imprisonment, and at last a sentence of banishment for ten years was pro- nounced against him. DERRfiCAGAIX, dOrrftki'gft'. Victor Beb- >AKI) I IS.'i;! — ). A French soldier, born in liayoune. He studied at the College of Saint Cyr, served in the Crimea in 1854 as lieutenant of infantry, and rose to be lieutenant-colonel in 1880. In 1883 he was appointed |)rofessor at the Kcole de (juerre. and in J88S became chief of the geogra]>hical senice of the army. He was pro- moted in 1880 to lie a general of brigailc. He is known for his topographical surveys of France, and for his works on military affairs — Etude sur lis flutsniajois dvs arinvis ftrangircs (1800); Uisluirv dr In ijuirre dr ISIO (1871) ; La guerre tiiiiiliiiir (1885); and others. DERRICK (from Dmith; a Tyburn hang- man). A device for hoisting heavy loads and eonvej'ing them short distances. In ordinary nomenclature the distinction between derricks anil cranes is considerably confused. The most common form of derrick consists of a vertical mast pivoted at its bottom into a fixed bedplate and maintained in an upright position by guy- cables or other forms of stays, which radiate from a loose collar or spider encircling a pin in the top of the nuist : of a boom hinged to this vertical mast near the bottom so that it may be made to assume various inclinations relative to the mast, and of the tackle and motors neces- sary to imjmrt motion to the boom and mast and to the load which they carry. The load is suspended from the end of the boom by ropes which pass through a bliH'k and thence to the motor at the foot of the mast. The end of the boom is sustained by a cable passing through a bUx-k at the top of the mast and thence to the motor at its foot. The mast is revolved on its bottonr pivot by means of a horizontal wheel around which a rope passes or by some other simple mechanism. The motions permitted by such a derrick are the vertical hoisting of the load, a swinging motion through tlic rotation of the shaft on its pivot, and a radial motion due to the change in inclination of the boom. Per- haps the most salient distimtion between a derrick and a crane is that the boom of the der- rick is hinged at its connection with the mast, while the jib of a crane is always rigidly con- nected with the upright mcmlH-r. If this dis- tinction is maintained in classifying these two sorts of hoisting and conveying devices, how- ever, it throws many devices now called derricks into the chiss of eranes. IVrricks of the type described are extensively employeil in quarrying, masonry work, excavating, and building erection. One of the largest derricks in the world is lo- cated at the .vonilale Marble Qmirries at Chea- ter. Pa., and will hoist a load of 100 tons. The general dimensions of this derrick arc as follows: Length of ma^t. 105>.j feet ; length of boom. 00>4 fe«'t : the mast is .■?] inches sqimre at the base and 20 inches in ilianietcr at the top: and the boom is 25 indies and 21 inches in diameter at the two ends. The main hoisting-rope is 1 ' .■ inches in diameter and is made of crucible-stt^
