SC)1 RC.l. ABBRl \ I A 1 lONs lOR Rl 1 1 Rl \t;i:s 



have till* Kjinu' pliysioal iliinoiisioiis, nititts aro 

 tunipio iiuiitlH>n<, niui mi on. 



T\\v purv' foriuula.s uiul oquiitiuns may tlierffort' 

 Ih» l'mploy^^^ witli any systoni of inwusuriMnont or 

 with any i-onthinations of unit.s in a particular 

 sysloni. Brii'f oxaniplos of thosi- applications arc 

 as follows: 



(a) EfToctive power =■ rt'sistaniv times sjMvd, or 

 /•« - RV 



(h) Fatness mtio = voliuno dividinl by (a con- 

 stant times IcngllO' = »-' (O.IO/,)' 

 (c) SihhhI of a shallow-water wave = ((accelera- 

 tion of gravity) times (water depth))" *, or 

 c - \ gh. To indicate that this example is 

 dimeiisionally ctinsistent 



c = veliH'ity = L t = "Vgh = ((acceleration) 



times (distance))" * = ((L//')L)" * = L.t. 



The elimination of mixeti quantities in power 

 formulas represents somewhat of a ilepartm-e fron> 

 standanl practice. The rate at which work could 

 Ih' done by a horse served conveniently as a 

 point of r»'ferenco a contviry ago; it lias practically 

 no nuxlern application. It necessitates the use of 

 arbitrary figures such as I^^.IXH) and 550, the use 

 of the term horse as a puir unit, and strict con- 

 formity of numerical vniits with tho.se lijiuivs. A 

 vastly simpler and nnich handier unit, for the 

 F^nglish system at least, would bo KHH) pouiul- 



fool-.>i«'coiul units, similar in its decimal .simplicity 

 to the well-known kilowatt and equivalent to 

 I. SIS horses. .\ change of this kind may conu' in 

 the futunv 



In the meantime, much ambiguity could iw 

 siveil by the u.se of a standard lar^e weight unit. 

 The long ton o{ 2,JI() pounds and the metric ton 

 of ■J,'Jt)5 pounds are of the sjxme order of maKiiiludo 

 but are not equal. The short ton of 2,(KH) (Hiuniis 

 is appearing with incn^ising freiiuoiu-y in naval 

 architecture and shipbuilding on inland lakes and 

 waterways. A simple solution is to use the large 

 weight unit of structural mechanics, the kip, or 

 kilopound, equal to 1,(K)0 pounds. It is O.o of a 

 short ton, O.lUVl of a long ton of 2,211) pounds, 

 and 0. 15I>5 of a metric ton. 



Finally, throughout both volumes the author 

 has introduced some historical highlights where 

 they seemed to be appropriate, and has mentioned 

 the names of pioneers in various hues of endeavor. 

 Witli many developments now tiiken for granted, 

 (he people responsible for originating them are 

 often forgotten. In the words of an unknown 

 eiiitorial writer of some three decades ago, when 

 discussing an article about the originator of the 

 set of Simpson's rules: 



'AVo wi.sh tliiit our futuri' :ulv;inci'<l I n\il !.•;«•.■< on iiiival 

 iireliiUvtun' would follow llu- tlictuf of Or. Wolch's 

 !uliln>.ss .'iiul oiilighti'ii us, with ilui- |in>portion, on nu'u 

 ;i.i well iux on tliii\>'.'<" (SUSli, l.'i Nov I'.C'a, pp. O00-4i01|. 



SOURCE .\BRREVI.VriONS lOR REFERENCES 



The soun^e abbreviations employe*.! through- 

 out the text and listed here are formetl by com- 

 bining the first letters of the principal wonis 

 composing the titles of books, periiniicals, and 

 the like, or of the names of organizations and 

 groups wliich have publishetl tniiisiictii>ns, pri>- 

 ceodings, and reports of one kiiui or another. 



The re.sulting abbreviations an> set down in 

 alphabetic orvler, ttigether with suHicient informa- 

 tion, AS of 19511, to permit the reader to look up 

 the references citetl or to get in touch with the 

 organizations concerneti. 



AD "Aerotlynamic Drag," by S. F. Iloer- 



ner, 11)51 ; publi.sheil by the author, 

 lis Uusteiil, Midlan.i Park. X. J. 



AKW .\dminilty KxiH'riment Works, IIsus- 



lar, (IiKsport, Ham|islure, England 



.Ml.\ ".\pplitxl Hydro- and .\eromwhaii- 



ics," by L. Prandtl and O. G. 

 Tietjens, translatetl by J. P. Den 

 Ilartog (substantially an English 

 translation of II.\M). Enginwring 

 Societies Monographs, Mctlraw- 

 Ilill. New York. 1934 



.\M (.\mericaii) Motorship, Diesel I\il)- 



lications. Inc., 192 Ix'xington Ave- 

 nue, New York 16, N. Y. 



ARC .\eronautical Research Committee, 



threat Hritain 



.\SCE .Vmerican Siniety of Civil Engineers, 



X\ West ;59th Stn>et, New York 

 IS, N. Y. 



.V.sJME .\merican Sm-iety of Mechanical 



Engintvrs, Xi \\\M ;t9tli Stre»<t, 

 New York IS, N. Y. 



