REPORT OF THE COMMITTEE ON THE PROVISIONAL PROGRAMME FOR THE CONGRESS.

(The following is the appendix referred to in the report of the Committee on the Provisional Programme for the Congress. See page pp. 14 and 26 ante.)

APPENDIX IV.

ELECTRIC NOTATION, ABBREVIATIONS AND SYMBOLS.

The following is an abstract of a paper read by Mr. E. Hospitalier at the International Congress in Frankfort, 1891, giving the system which the Committee of the AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS suggested using as a basis for an International system to be adopted at the next Congress.

The object of this system is to introduce a uniform international system of symbols, abbreviations, etc., for terms used in the electrical science, which shall be as universally adopted and understood as the various signs used in algebra and trigonometry, for instance. In such a system, he states, that it is indispensable to establish a clear and precise distinction between a physical quantity, its magnitude or value, and the unit for measuring such a quantity. A physical formula shows the relation between physical quantities each of which is represented by a special symbol. The magnitude or value of physical quantities are represented by the ratios of the physical quantity and one of the same nature taken as a unit; the magnitudes or values of physical quantities are therefore simply abstract numbers. A unit is a physical quantity of a special magnitude which serves as a measure of quantities of the same nature; these units are designated by special names, and may be represented by abbreviations for the sake of simplification. Symbols representing physical quantities enter into physical formulæ, but units never do. In the c. G. s. system, for instance, the three basic physical quantities are length, mass and time, which are represented by the respective symbols L, M and T'; the corresponding units are the centimetre, the mass of one gram, and the second; their abbreviations are cm, g, and s. For derived quantities, definitions are established by equations which show the relation between the fundamental quantities. The physical quantity, surface, for instance would be represented by the symbol S and defined by the equation SLX L = L and the unit for measuring it is the square centimetre represented by the expression cm; the

physical quantity, velocity, represented by v is the quotient of the length by a time and is defined by the equation = L÷T= L T and the unit is a centimetre per second. This would establish the important and essential distinction between the symbols representing physical quantities, and the units for measuring their magnitude. He suggests using italics, Greek and script letters exclusively for symbols, while for the units and their abbreviations he suggests using Roman letters.

He suggests furthermore using the same letters for physical quantities of the same nature whose dimensions are different, or for different physical quantities whose dimensions are the same; he proposes, for instance, to use the symbol W for the physical quantity"energy," be it mechanical, thermic, chemical affinity or electric; also, to represent the moment of a force or of a couple, as it is, like work, the product of a force and a length. A length and a coefficient of self-induction have the same dimensions and are to be represented by the same symbol L to which in certain cases an index may be added to avoid confusion. He furthermore suggests adopting the system already in use of representing kilometres by km, millimetres by mm, milligrams by mg, etc. Of the six different ways of representing quotients: centimetre per second;

centimetre, cm

second

; cm:s; cm.s-1; cm/s;

he recommends using cm s as the simplest. His suggestions for a complete system of such units and quantities as are used by electricians, is given in the following table which he claims to have modified to conform with the decisions adopted by the Congress of 1891, which have been given in Appendix I. [See next page.]

In addition he also suggests the advisability of a uniform system of reference to articles in technical periodicals; this should state the volume, the page, the date and in every case the year. He also recommends that in adopting new names, very great care should be taken: the word "drehstrom" for instance, (which literally means a rotary current) does not correspond to any physical reality; the proper expression would be "polyphase alternating currents."

[The undersigned calls attention to the fact that the symbols do not all conform strictly to the adoptions of the Congress of 1891, which decided that Greek letters should be used only for physical constants and angles; Mr. Hospitalier furthermore uses "small caps" for the symbols representing the units, in place of large capitals, a modification which is to be commended, as it avoids confusing A (ampere) with A (acceleration). The chief objection which English speaking people will have to this system is, the changing of the E E classical expression for Ohm's law from C= and writing Io R for R'

to I

R

CR. This might be overcome by writing C for current, K for capacity, and I

for moment of inertia.]

CARL HERING,
Chairman.

HOSPITALIER'S PROPOSED SYSTEM OF NOTATION.

(Reprinted from "L'Industrie Électrique," by the American Institute of Electrical Engineers.)

1 The International Bureau of Weights and Measures has established an important distinction in the notation of time, according as it refers to the epoch (date of time of day) or the duration of a phenomenon. In the former the reference letters are used as indices and in the latter they are on the same line with the numbers, for instance SD experiment began at 2h 15m 46 lasted 2 b 15 m 46, and ended at 431 3 This method is to be recommended.

2. The distinction between the different units for angles (radians degrees, minutes, seconds, etc) and their notation is a matter which ought to come before a Geodetic Congress. No propositions are made here.

3. Nis the number of windings, L the length of the solenoid generating the magnetizing force.

4. Abbreviations to be desired.

COMPILATION OF DISCUSSIONS, SUGGESTIONS AND CRITICISMS, APPEARING IN THE TECHNICAL AND SCIENTIFIC PRESS UPON THE REPORT AND PROVISIONAL CONGRESS PROGRAMME OF THE SUB-COMMITTEE APPOINTED BY THE AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS.

I. The London Electrician, vol. xxx, No. 768, p. 377, Feb. 3rd, 1893, comments favorably upon the programme in general. Criticises the definition offered for impressed E. M. F. on the grounds of inaccuracy.1

Questions the need of a unit of reluctivity.

Acquiesces in the suggestion of the term "voltage" in preference to "P. D." "tension" or "pressure," adding, however, that a single term is likely to prove inadequate.

Acquiesces in the suggestion of using the term "transformer" in place of "converter," " dynamotor dynamotor" in place of "continuous current-transformer," and continuous current" in place of "direct current."

"

Objects to the substitution of the "kilowatt" for the "horsepower." No reason is, however, given for the preference of the latter, but it appears to be implied that British engineers are wedded to the term "horse-power."

Approves of the "henry," "gauss" and "weber,” among the suggested units.

Objects to the name for a unit of illumination being made "candle-foot" or "bougie-metre," on the grounds that such compound names imply a product of the components. Does not suggest an alternative.

Suggests that the term "installation" be discarded.

II. The editors of the monthly bulletin of the Société Internationale des Électriciens, in the February number (No. 95), in

1. This criticism was challenged by one of the members of the sub-committee in a letter addressed to the Editors of The Electrician, and published in their issue of March 17th, vol. xxx, No. 774, p. 579. The definition was then admitted to be accurate, conditional upon a proposition that has probably never been disputed.

clude the greater part of the sub-committee's report, with comments of the following purport :

Acquiescence is given to the suggestion that the practical electrical units already adopted and confirmed by Congresses should not be altered.

In regard to the proposed magnetic units, doubt is expressed as to whether the advantage of suppressing the coefficient 1/4π would not be sufficient to make the practical magnetic unit of M. M. F. the ampere-turn simply.

Acquiescence is expressed towards the exchange of the term "henry" in place of the term "quadrant."

It is agreed that the "kilowatt-hour" and "ampere-hour" are units in themselves sufficiently brief and explicit to be retained.

The term "Board-of-Trade-Unit" is condemned as being uninternational. It is pointed out that according to the report of the British Board of Trade Committee on Electrical Standards, which report is recommended by the sub-committee of the A. I. E. E., the deposit of silver serving to determine the strength of a current is referred to a weight, whereas it should for greater accuracy of expression have been referred to a mass.2

The Board of Trade proposition of the standard ohm, i. e., a mercury column of length 106.3 cms. and 14 4521 grammes mass at 0°C. is favored, provided that this value should be considered as definitely fixed, and not left for future Congresses to amend.

Approval is expressed of the recommendation that no universal wire-gauge should be attempted other than an international designation of wire diameters in millimetres.

In regard to the suggested international system of notation and symbols, the difficulty of determining initial letters suited to all languages is adverted to.

The suggestion is made that the definition: The impressed electromotive force is the ratio of the total activity in an electrically conducting circuit to its instantaneous current strength." should for greater clearness be amended to:-"The impressed electromotive force at a given moment is the ratio of the activity to the instantaneous current strength at that moment."

The suggestion is made that since the terms "inductivity and "permeability are set forward as synonymous, the former

needs not to be introduced.3

2 This criticism appears to have been withdrawn at the next meeting of the Society, q. v.

3. The object of the proposal to adopt the term inductivity" was to complete the system of nomenclature introduced by Mr. Oliver Heaviside, see The Electrician p. 271, Feb. 12th, 1886, where the term inductivity" is proposed as a substitute for permeability," aiso Electrical Papers," by Oliver Heaviside, vol. ii, p. 28. Mr. Heaviside has, however, since taken the position that "inductivity" is not synonymous with "permeability" (see The Electrician for Mar. 24th, 1893, vol. xxx, No. 775, p. 593), so that the exclusion of the term inductivity,” in the sense suggested by the report, is perhaps advisable.