The metric standards of length and mass are kept at the International Bureau of Weights and Measures in the Pavilion de Breteuil, Sevres, near Paris. The Bureau is jointly maintained by the principal civilized governments as members of the Metric Convention. The use of metric weights and measures was legalized in the United Kingdom in 1897. LENGTH Unitthe centimetre, 1/100 of the international metre, which is the distance, at the melting-point of ice, between the centres of two lines engraved upon the polished " neutral web " surface of a platinum-iridium bar of a nearly X-shaped section, called the International Prototype Metre. DERIVED C.G.S. UNITS Velocity :-Unit-\ cm. per second. Angular Velocity :-Units-I radian (57°-2C;6) per sec. ; I revolution per sec. Acceleration :-Time rate of alteration of velocity. Unit-(i cm. per sec.) per sec. Angular Acceleration :-Units-I radian per sec. 2 ; i revolution per sec. 2 Momentum :-Mass multiplied by velocity. Uniti gm. cm. sec.-1. Moment of Momentum :-Momentum multiplied by distance from axis of reference. Unit-I cm. 2 gm. sec.-1. Moment of Inertia :-~s ,md?,where m is the mass of any particle of a body, and d its distance from the axis of reference. Unit-i cm. 2 gm. (see p. 16). Angular Momentum :-Moment of inertia multiplied by angular velocity round axis of reference. Unit-I cm. 2 gm. sec.-1. Porce :-Measured by-the acceleration it produces in unit mass. Unitthe dyne = cm. gm./sec. 2 Gravitational unitthe weight of I gram = g dynes. Couple, Torque, Turning Moment :-Force multiplied by distance from point of reference. Uniti dyne cm. Work :-Force multiplied by distance through which point of application of force moves in direction of force. Unitthe erg = I dyne cm.; I joule = lo 7 ergs. [i calorie = 4-18 joules]. Gravitational unitweight of I gm. x i cm. =^dyne cms. = g ergs. Energy :-Measured by the work a body can do by reason of either (i) its motion-Kinetic Energy (= mv 2 /2) or (2) its position-Potential Energy. Unit-the erg. (See "Work.") 1 Board of Trade Unit = 1 kilowatt hour = 3'6 x io 8 watt-sees. Power :-Work per unit time. Unit-1 erg per sec. 1 watt = io T ergs per sec. = 1 joule per sec. = 1 volt-ampere. 1 kilowatt = 1*34 horsepower. Pressure, Stress :-Force per unit area. Unit-1 dyne per cm. 2 1 megabar = io 6 dynes per cm. 2 =; 750 * mm. mercury at 0°C, lat. 45 , and sea-level (g = 980-6). 1 atmosphere = 760 mm. mercury at 0°C, lat. 45°, and sea-level = 759/4 mm. mercury at o°C. in London = J/0132 x io 6 dynes per cm. 2 = 147 lbs. per inch 2 = o-94 ton per foot 2. »^,. t. ... 7T tr • • Correct to I part in 5000. Elasticity :-Ratio of stress to resulting strain. Unit-1 dyne per cm. 2 , since the dimensions of a strain are zero. HEAT UNITS Temperature :-The melting-point of pure ice under 1 atmosphere is defined as o°C, and the boiling-point of water under 1 atmosphere as ioo°C. This fundamental interval is divided into 100 parts by use of the constant-volume hydrogen thermometer (see p. 44) ; each part is a degree Centigrade. Dimensions of temperature ...

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Ternporntiire. ' F. Exlinustar Tar fog Inlet Outlet Inlet speed, grnins/100 cu. esliniistcr eslinuster LivEseys r.p.m. ft a 101 GI 3.2.;0 "3.5 104 ti; 3.12'8 27.7 111 ;9 3,000 110.0 2 97The increnserl nmount of tnr fog in the gns wns very efficiently reinovcd by the Livesey wnshers, probably becnuse of the incrensed size of the drops due to condcnsntioii of wnter niid tnr rapours. Tnr fq Outlet Licesey icnshersTcnipernttirc, F. l'nr fog hilet Oritlet Inlet Oiitlct gr./lOo CII. c*rhnuster edinustcr Lireseys 1,ivrwys Ile\-e.,'min. ft. 97 10; ;st 01 3,040 1 . ; S7 1031 o q U34 3.150 2.0It persisted in the pus though the aninionin wnsliers n s fnr ns the inlet to purifiers, aherc. the concentrntion wns nlso 1 to 2 prnins per 100 CII. ft.The sninll ninount of tar fog collected wns dry. FIG. 5 600 JJIJJI. rlio. junirhccl large c o d gas rrlitcusler 450,000 en. jl. hr., two slogc nrachine I t v;ns shown in n con1 gas strenin from continuous rerticnl retorts that \vet tnr fog could bc removed by nicniis of IL P nnd A Tar Estrnctor following n high-speed exhnuster and sccondnry condensers with nn efficiency of nbout 97%. Tnr fog Tcml~rnture, F. grnins/IOO cu. ft. Inlet Outlet Inlet Inlet Outlet Efficicnry esliniistcr eslinoster 1' & A l

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