DYING GAUL. 563 DYNAMO-ELECTRIC MACHINERY. warrior supporting,' himself on his shield and dviug from a wound in his breast. DYKE. See Dike. DYKES, .rAMiss Oswald (18.35—). A Scot- tish I'reslnterian chTgyman anil eduiiitor, born at Port-Glasgow. He studied at the universities of Edinburjrh, Heidelberg, and Erlangen, was or- dained to the Presbyterian ministry in 1859, and in 18G1 became co-pastor with Dr. Camllish of Free Saint (ieorge's Church, Edinburgh. In 18G9 he was a])pointed pastor of the Regent .Square Church, London, and in 1888 principal of the Theological College of the Presbyterian Church of England. His publications include: From Jcrtisalrm to Antioch (1875); The Laic of the Ten Words (1884); The Oospcl According to Saitit Paul (1888) ; and Plain Words on Great Themes (1802). DYKES, John Bacchcs (1S23-7G). An Eng- lish musician and clergj-man, born at Hull. He graduated at Cambridge University in 1847, and two years later was appointed minor canon and precentor of Durham Cathedral. From 1862 he was vicar of Saint Oswald's. Durham. He pub- lished a number of sermons and tracts, but is best known for his universally popular hymn- tniics. DY'MOND, .Jo..THAN (1796-1828). An English writer. He was a member of the So- ciety of Friends, and w-as prominent as an ex- positor of the principles of his sect. In 1823 he published an Inrjuiri/ Into the Accordance of War tcith the Principles of Christianili/, which attracted wide attention. His chief work is his Essays on the Principles of Moralitii (1831), which is devoted to the application of moral principles, and attacks war and dueling. DYNAM'ETER (contracted from dynamom- eter, from Gk. Siva/iis, di/namis, power -f- fiirpov, metron, measure). An instrument for meas- uring the magnifying power of a telescope. The power of a telescope is found by dividing the focal length of the object-glass by the focal length of the e.vepieee; which quotient equals that obtained by dividing the diameter of the object-glass by the diameter of its range formed at the focus, and seen through the eyepiece. The object of the d.'nametcr is to measure the diameter of this image. Practically the mag- nifying power may be measured as follows: The telescope is directed to the daylight skv. A small, round, bright spot is then seen on look- ing at the end of the eyepiece. Tliis spot is an image of the object-glass. The diameter of the spot is measured with a d>Tiameter. or any mi- crometrie instrument capable of measuring small objects accurately. The object-glass being then also measured, a simple division of the object- glass diameter in inches by the diameter of the spot, also in inches, gives the magnifying power. DYNAMICS (Gk. SvmfUK6i, dynamikoi. pow- erfiil, from Svm.iut. dyn<imis. power, from Sifav- Oat, dynasthai, to be able). That branch of mechanics (q.v. ) which treats of the motion of matter. It embraces the discussion of the condi- tions under which the motion of matter is changed and the mathematical properties of this motion. D^Tiamics is sometimes divided into the two great subjects statics and Icinefics. statics being the disevission of conditions under which there is no change in the motion: kinetics, those under which tlicrc is change. Dynamics of a ■particle' treats the motion of a geometrical point endowed w ith mass. 'Rigid' dynamics treats the motion of large, rigid bodies; that is, those made uj) of particles so connected that Ihcy have no rcl.itivc million. DYNAMIC UNITS. See Mechamcal Units. DYNAMITE (from Gk. dlmjus, dynumis, power). .u explosive substance consisting of nitriiglyccrin and an absorbent such as infu- sorial earth (Kieselguhr) or diatomaceous silica, tripoli, rotten stone, wood, fibre, etc. It was in- vented in 1866 by Alfred Nobel. The original d.vnamites varied from 75 per cent, of nitro- glycerin and 25 i)er cent, of absorbent, down to 30 per cent, of nitroglycerin and 70 per cent, of absorbent, but 40 per cent, of nitroglycerin may be given as the average amount. " In the United States the absorbent often is of an ex- plosive nature and consists of a mi.xture of wood- pulp and sodium nitrate, with small quantities of calcium or sodium carbonate to neutralize any acid which may be present in the mixture. The product when thus formed is knowTi as a 'straight dynamite,' but gunpowder or some resinous substance may be used for the ab- sorbing material. Perhaps the most powerful form of dynamite is the explosive or blasting gelatin also invented by Nobel, in 1875, where pyroxylin or soluble cellulose nitrate is dis- solved in nitrogl.vcerin and a jelly-like mass produced. When this material is mixed with wood-meal or wood-pulp, the resulting product is toown as gelatin dvnamite. For commercial use the compound is made up in sticks or cartridges 8 inches in length and 1^/2 inches in diameter, which are usually packed in sawdust in boxes containing fifty pounds each. In the twelfth United States census the follow- ing table is given, showing the production of dynamite by decades in the United States: s si Product ■r S 5 S T. s ^d c fefeS 5 3 & H s 5 < Ch > 1880 2 S622.671 1890 32 $.3,929,503 731 30.626,7.-)a 4,2.'i3.032 1900 31 7,551,121 1,758 85,846,456 8,247.223 Dynamites have various names, according to the absorbent used, as '.tlas powder,' 'giant powder,' 'Hercules powder,' 'Neptune powder,' 'rendrock powder,' 'Titan powder,' etc. See Ex- plosives ; NiTItOGI.YCKniX. DYNAMITE CRUISER. See Okdnance, Classes of Caniion. DYNAMITE GUN. See Air Grx: Oitn- NANCI:. DYNAMO - ELECTRIC MACHINERY. Machinery in which mechanical energy is con- verted into electrical energy, or vice versa, by means of magnetic induction. -According to this definition, every dynamo-electric machine is capa- ble of serving either as a generator or as a motor, according to whether it is supplied with
