REPORT OF THE SUB-COMMITTEE ON PROVISIONAL PROGRAMME FOR THE INTERNATIONAL

ELECTRICAL CONGRESS OF 1893.

To the General Congress Committee of the American Institute of Electrical Engineers:

GENTLEMEN:- The Sub-Committee on Provisional Programme respectfully submits to you the following report:

DUTIES.

The Sub-Committee understands its duties to be as follows: To suggest what work it is desirable to have done at the coming International Electrical Congress to be held in Chicago in 1893. To suggest a programme for carrying out this work in the most satisfactory manner to all parties, and with the least loss of time.

RECOMMENDATIONS.

Regarding the work to be done, your Committee's recom mendations are as follows:

RATIFICATIONS.

(1.) Ratification of the adoption of units, terms, symbols and

definitions by previous International Electrical Congresses. This is a mere matter of form and an act of courtesy to the preceding Congresses. Your Committee understands that this was done at both the Paris Congress of 1889 and the Frankfort Congress of 1891. (For the work done at previous Congresses see Appendix I.)

NEW UNITS.

(2.) Defining and adopting practical units for measuring and designating the measurements of the following quantities: Magneto-motive force; magnetic flux; mugnetic intensity; magnetic reluctance; electric conductivity; illumination. It will be noticed that this refers only to the question of what the magnitude of the units shall be, or, in other words, what multiples or sub-multiples of the absolute units they are to be.

Your Committee is aware that objections are raised by some, to the establishment of units not already in universal use. Past experience, however, has shown that the proper time to establish units is before their need is universally felt, in order to avoid the introduction by different persons or nations, of units of different values, a contingency which will be very likely to arise if not anticipated by concerted action.

Your Committee recommends the following:

The value of the practical unit of magneto-motive force to be 1 one-tenth of the absolute unit, that is, equal to ampere turn. Απ

The value of the practical unit of magnetic flux to be 108 absolute units or lines.

The value of the practical unit of magnetic intensity to be 108 absolute units, that is, 10 lines per square centimetre.

The value of the practical unit of reluctance to be 10-9 absolute units. (For further explanation of these magnetic units see Appendix II.)

The value of the practical unit of electrical conductivity to be 10-9 absolute units, that is, to the reciprocal of the ohm. This makes it equal to the unit proposed some time ago and known to some extent by the name of "mho." It should be given this value in order that it correspond with the already adopted units.

The value of the practical unit of illumination to be a bougiedecimale at the distance of one metre. The bougie-decimale is the unit of light or candle power already established and is practically equal to one English standard candle; by making the distance a metre, the practical unit will be approximately equal to one-tenth of a carcel-metre, one-tenth of a foot-candle (or "lux") or to one metre-candle or metre-kerze, all three of which units are already in use to some extent.

It has been announced that a proposition will be made at this Congress to change the values of some of the practical units.

which have been adopted by previous Congresses and are already in universal use. Among these are the ampere and the farad. It is urgently recommended by your Committee that such changes should not be favored, since they would necessarily be followed by great confusion and would of necessity have to be accompanied by some change in these well established names. in order to distinguish these new units from those now existing.

NAMES FOR UNITS.

(3.) Adopting names for the following practical units: Magneto-motive force; magnetic flur; magnetic intensity ; magnetic reluctance; inductance; electrical conductivity; iilumination.

The following names are suggested for these units:

For the practical unit of magneto-motive force, the name "gilbert."

For the practical unit for magnetic flux, the name "weber." This term was formerly applied to a unit of current, but its use in this sense was so limited, and it has been abandoned for so long a time that no confusion would be likely to arise; the context alone would always be sufficient to prevent any possibility of misunderstanding. The name "weber" is preferred on account of the intimate relation between this unit and that of magnetic intensity for which the name "gauss" is suggested.

For the practical unit of magnetic intensity, the name "gauss." This name has already come into use to such an extent that objections to it will not be likely to arise.

For the practical unit of magnetic reluctance, the name "oersted."

For the practical unit of inductance, the name "henry." This name has already come into use quite extensively and it would therefore be very undesirable to change it. The value of this unit has already been fixed as equal to 10° absolute units or nearly to the length of an earth's quadrant. The definition "quadrant" is sometimes employed as the name itself, but its use as a name is evidently objectionable, as it already has several other meanings, which might readily lead to confusion.

For the practical unit of electrical conductivity, equal to the reciprocal of the ohm, the name "mho." This name has been in

use for some time and is already well known. It is thought better to recommend it than to select and introduce a new

name.

For the practical unit of illumination defined above, the name "bougie-metre."

It has been suggested to name the units "kilowatt-hour" and "ampere-hour." Your committee, however, recommends that inasmuch as these terms explain themselves, and are not longer than some others in use, to give them special names would burden a system of nomenclature unnecessarily. The principal objections to the term "Board of Trade Unit," which is in use in England for the former, are, that it could never become international, that it is longer by one syllable than the term "kilowatt-hour," and that there are now, or may soon be, units of other denominations adopted by the same Board of Trade, from which this one will have to be distinguished by an additional affix or prefix.

CONCRETE STANDARDS.

4. Defining and adopting modes of embodying the following principal units of measurement in concrete standards capable of being readily reproduced, and adopting names for them or for the theoretical units, by which they can be distinguished from each other :— Ampere, ohm, volt, watt, standard candle.

The following definitions of these units are recommended: An ampere shall be that unvarying current, which, when passed through a solution of nitrate of silver in water, in accordance with the specifications recommended in the recent report to the British Board of Trade (See Appendix III), deposits silver at the rate of 0.001118 of a gramme per second.

An ohm shall be the resistance offered by a column of mercury at the temperature of melting ice 14.4521 grammes in mass, of a constant cross-sectional area, and of a length of 106.3 centimetres. It is recommended that material standards of this value, constructed in solid metal, should be preserved under the care of the several governments, as standards of comparison, and that they should from time to time be verified by comparison with the mercury standard defined above; also that for the purpose of replacing the standard, if lost, destroyed, or damaged, and for ordinary use, a limited number of copies should be constructed which should be periodically compared with the standard ohm.

A volt shall be the product of this ampere and this ohm..

A watt shall be the product of the square of this ampere and this ohm.

The other units such as the coulomb, the farad, and the joule, shall be taken as derivatives in terms of this ampere and this ohm.

In order to create as little confusion as possible by the introduction of this set of units which are to become the universal standards, and in order to distinguish them readily from the true theoretical, or abstract units defined in terms of the absolute units, it is recommended to call the former simply "amperes," "ohms," "volts," etc., or more specifically "standard amperes," "standard ohms," etc., and to call the theoretical units "true amperes," "true ohms," etc. The latter term has already come

into use in this sense.

The unit of resistance known as the B. A. unit, shall be taken as equal to 0.9866 of this ohm.

The electro-motive force of a Clark cell at 15o C., prepared in accordance with the specification recommended in the recent report to the British Board of Trade (see Appendix III.), shall be taken as not different from 1.434 of these volts by more than one part in one thousand. The coefficient of temperature shall be taken as....

.?

The standard candle shall be taken as equal to the light from a lamp like that known as the Hefner-Alteneck standard amyl acetate lamp, which is to be defined by its dimensions and the height of the flame, the dimensions being such that the light shall be equal to that of the "bougie-decimale," the practical unit adopted at the Paris Congress of 1889, which is equal to onetwentieth of the absolute platinum standard adopted in 1884.

It has also been suggested that a universal wire gauge be defined and adopted. Desirable as this may at first seem, your committee recommends that no action be taken by the Congress in this matter, as it is not likely that any one scale would ever be universally adopted by manufacturers, even if defined and adopted by a Congress. The universal introduction of the metric system and the designation of wires by their diameters in millimetres, is thought to be the only satisfactory solution of this question for international work.

NOTATION AND SYMBOLS.

5. Adopting an international system of notation and conventional symbols, for designating different quantities.