DlRT-BED 



165 



DIVING 



section, which serves to determine the curve 

 of the figure. 



Dirt-bed. A thin bed of vegetable soil, con- 

 taining roots of trees, &c., in Lower Purbeck 

 strata. 



Disaster, (dis-as'ter). [Gk. dis, twice; aster, 

 star.] A sea-urchin found fossil in Lower 

 Oolite rocks. 



Disc, (disk). [L. discus, quoit.] Used gener- 

 ally for any small, flat, circular surface. D. 

 and roller: a small roller revolving on an 

 axis upon the surface of a disc; used to com- 

 nmnicate motion from one to the other. 



Discharge. D. of electricity, from an elec- 

 trified surface: may be converted into light, 

 motion, magnetism, or chemical action, the 

 electrified surface being restored to a neutral 

 condition. 



Discharger. An apparatus for restoring any 

 electrified surface to its neutral condition. 



Disciform, (dis'si-form). [Disc and form.]= 

 Discoid, q.v. 



Discina, (dis'si-na). A genus of Brachiopoda; 

 a mollusc found in the oldest geological 

 strata, and still extant. 



DiscinidsB, (dis-sin'i-de). [Discina. q.v.} A 

 division of Brachiopoda, the type of which is 

 the disci na. 



Discoboli, (dis-kob'o-li). A family of fishes. 



Discoid, (dis'koid). [Disc, q.v.; Gk. eidos, 

 form.]=Disc-like: having nearly the form of 

 a disc. 



Discoidal, (dis-koid'al). [Discoid, q.v.] D. 

 placenta: found in man, apes, bats, &c. D. 

 shells: univalve shells coiled in one plane. 



Discomycetes, (dis-ko-ml-se"tez). [Disc, q.v.', 

 Gk. my kes, mushroom.] Morells, <fec.; fungi, 

 forming a division of Ascouiycetes, either 

 pileate or cup-shaped, of fleshy substance. 



Discontinuous gemmation, v. Gemmation. 



Discophora, (dis-kof'o-ra). [Gk. diskos, disc; 

 phero, I carry.] 1. = Acalaphae, g.v.=:Me- 

 dusae: a primary division of Hydrozoa. 2. 

 Suctoria= Leeches, q.v. : a division of Anne- 

 lida, having sucking discs. 3. Hirudiuea, 

 q.v. 



Discophorse, (dis-kofo-re). [Discophora, q.v.] 

 A sub-division of Tetracyclse. 



Discord, (dis'kord). [Discordia, the Latin 

 word. ]=Dissonance, q.v. 



Disinfection, (dis-in-fek'shun). [L. dis, from; 

 infection, q.v.] The removal of putrefying 

 matter. 



Disintegration, (dis-in-te-gra'shun). [L. dis, 

 from ; integer, whole.] To break up into 

 component particles; especially used of the 

 wearing away of rocks by the action of water, 

 air, &c. 



Disodic, (di-so'dik). [Di and Sodic, q.v.] v. 

 Sodic. 



Dispersion, (dis-pe/shun). [L. dispergo, I 

 scatter.] D, of light Decomposition of light: 

 the separation and dispersion, so as to form 

 a spectrum, of the various coloured rays of 

 which white light is said to be composed. 



Displacement, (dis-plas'ment). 1. Quantity 

 of water displaced by a ship. 2. A gas is 

 collected by displacement when it is passed 

 into a vessel containing only air; if heavier 



than air it is passed down, if lighter than air 

 it is passed up, into the vessel, when the air 

 is displaced by the gas. 



Dissepiments, (dis-sep'i-ments). [L. dissepio, 

 I separate.]=Partition plates dividing the 

 cells of a compound ovary. 



Dissociation, (dis-so-si-a'shun). [L. dissocio, 

 I separate.] Partial decomposition of chemi- 

 cal compounds by means of heat; as of car- 

 bonic anhydride into carbonic oxide and 

 oxygen. 



Dissonance, (dis'so-nans). [L. dissonus, dis- 

 cordant.]=Discord: caused when the differ- 

 ence of vibrations in two musical sounds 

 is greater than 0, but less than 132 per 

 second, at a maximum when this equals 33 

 per second. 



Distal, (dis'tal). The term used for the more 

 quickly growing end of a hydrosoma; the end 

 which usually has the mouth. 



Distance, (dis'tans). [L. distantia, distance.] 

 Angular D.: the distance round the circum- 

 ference of a circle that any object has moved 

 or appeared to move. 



Disthene, (dis'then)=Cyanite=Al 2 O 3 SiO2 : a 

 crystalline form of silicate of alumina. 



Distichous, (dis'ti-kus). [Distichos, the Greek 

 word.] Two-rowed. 



Distillation, (dis-til-lii'shun). [L. destillo, I 

 distil. ] The vaporization of a liquid by heat, 

 and its recondensation by cold, usually for 

 the purposes of purification. 



Distoma, (dis'to-ma). A tunicated mollusc 

 belonging to Botryllidae, which has young 

 by internal gemmation = King's yellow 

 worm. 



Disulphate, v. Sulphate. 



Disulphide, v. Sulphide. 



Ditartaric acid, (dl-tar-tar'ik). [Di and Tar- 

 taric, q.v.]=C$H.iQOu; obtained by heating 

 tartaric acid. 



Ditetryl, (di-tet'ril). [Di and Tetryl, q.v.]= 

 Butyl=Vatyl=(C 4 H 9 )2: a hydrocarbon pro- 

 duced in the distillation of coal. 



Ditrityl, (dl-tri'til). [Di and Trityl.]=(C 3 H 7 ) 2 

 =Propyl=Dipropyl, q.v. 



Diureides, (dl-u're-Idz). [Di and Ureides.j 

 Obtained from some organic acids by the 

 action of urea; two equivalents of urea unit- 

 ing with one of the acid. 



Diurnal, (di-er'nal). [L. dies, day.] Daily. 

 J). flowers: open in daytime. 



Divers, (di'verz). [A.-S. dyfan, to dive.]= 

 Colymbidse : aquatic 

 birds with small wings. 

 Cartesian D., v. Carte- 

 sian. 



Divi-divi, '(di-vi-di'vi).= 

 Fruit of Cfesalpinia co- 

 riaria, used in dyeing 

 and tanning. 



Divalent, ( di'val-ent ). j 

 [Gk. dis, twice; L. va- 

 lens, strong. ] = Bi- 

 equivalent, q.v. 



Diving,(di'ving). [Diver, 

 D. bell . a hollow 

 vessel, xisually bell- Diver. 



shaped, used for working under water. D. 



