January 14, 191 5] 



NATURE 



545 



four nations were represented, the final recommenda- 

 tions were ratified as given in the report here re- 

 printed. An article on the proceedings of that meet- 

 ing appeared in Natl'RE of September 25, 1913 

 (vol xcii., p. 109). 



Introductory Remarks on the Standardisation of 

 Symbols. 



In so far as electrotechnics alone are concerned, it 

 would seem possible to standardise symbols, and the 

 following principles have served as the basis of the 

 work of the special committee in the attainment of 

 this object : — 



The symbols must be clearly distinguishable one 

 from another when writing with a pen on paper, with 

 chalk on a blackboard, or with a typewriter. In the 

 printed text, it is advisable to use a different type for 

 the symbols from that of the text. It is desirable 

 also that in ordinary handwriting, one should not be 

 obliged to add distinctive signs to symbols to specify 

 the type to be employed. It should be possible to 

 spell out the symbols when writing them on the black- 

 board. Finally, preference should be given to those 

 symbols already in common use. From this it will be 

 seen that it is impossible to make a distinction, in 

 ordinary handwriting, between Roman letters and 

 italics, and that small roundhand letters, being too 

 difficult to differentiate from the above, cannot be 

 used. It is generally agreed to abandon Gothic type, 

 as requiring too long a time in writing. Finally, 

 many of the Greek capitals are identical with Roman 

 capitals. Taking the above points into account, there 

 remain about one hundred symbols available in 

 Roman, Script, and Greek type, of which several are 

 already used for mathematical symbols and which are 

 necessary for the purposes of the electrician. A list of 

 symbols most frequently needed in electrotechnics is 

 appended herewith. Taking into account certain sym- 

 bols which are occasionally made use of, it is obvious 

 that there will be none left for purely physical or 

 mechanical quantities. Thus, in the same formula, 

 electrotechnical symbols may occur in conjunction with 

 other symbols used in mechanics and physics gener- 

 ally; this is especially the case in equations containing 

 mass, moment of inertia, speed, density, temperature, 

 quantity of heat, etc. The I. E.G. recommends, there- 

 fore, that in such cases, for physical and mechanical 

 quantities, the symbol habitually used by physicists 

 ;md mechanical engineers should be employed, if this 

 >ymbol does not already exist in the formula as an 

 electrotechnical symbol. If, on the contrary, it already 

 exists in the formula, it is desirable that it be accom- 

 panied by a distinctive sign or that the notation be 

 changed. 



Rules for Quantities. 



(a) Instantaneous values of electrical quantities 

 which vary with the time to be represented by smaH 

 letters. In case of ambiguity, they may be followed 

 by the subscript "t." 



(b) Virtual or constant values of electrical quantities 

 to be represented by capital letters. 



(c) Maximum values of periodic electrical and mag- 

 netic quantities to be represented by capital letters fol- 

 lowed by the subscript "m." 



(d) In cases where it is desirable to distinguish 

 between magnetic and electric quantities, constant or 

 variable, magnetic quantities to be represented by 

 capital letters of either script, hea\"y-faced, or any 

 special type. Script letters to be only employed for 

 magnetic quantities. 



(e) Angles to be represented by small Greek letters. 

 (/) Dimensionless and specific quantities to be repre- 

 sented, wherever possible, by small Greek letters. 



NO. 2359, VOL. 94] 



Tables of Symbols Adopted. 

 I. — Quantities. 



* A symbol for ihe .second column is to be supplied by the Austrian snd 

 German Committees jointly and inserted without further discussion bv the 

 I.E.C. ' 



t This symbol will be omitted if the Austrian and German Committees 

 agree to do so. 



I A symbol for the_ second column is to le supplied by the .Auiitrian and 

 German Coiimittees jointly and inserted without further discussion bv the 

 LE.C. ' 



The German delegate made a reser\ation in regard 

 to the symbols 13, 14, 20, 23, 25, 27 to 31, which are 



