[supplement To Report Of The Sub-committee On Provisional Programme For The International Electrical Congress Of 1893.] APPENDIX I. Brief Summary Of The Units, Terms, Symbols And Definitions Adopted By Previous Electrical Congresses. The Paris Congress of 1881 adopted, on September 21st, 1881, the following: The fundamental units: centimetre, mass of a gramme and the second, for electrical measurements. The practical units, ohm and volt, defined in terms of the absolute units. The ampere defined by the volt and the ohm. The coulomb defined by the ampere and the second. The farad defined by the coulomb and the volt. It also resolved that the ohm be represented by a column of mercury of one square millimetre cross-section at 0° C, and of such a length, to be determined by an international commission, that its resistance be equal to the ohm. The Paris Conference of 1884 adopted, on May 3d, 1884, the following: The legal ohm of 106 centimetres. The ampere defined in terms of the absolute units. The volt defined by this ampere and the legal ohm. The unit of light defined as the quantity of light emitted perpendicularly from a square centimetre of platinum at the temperature of its solidification.1 At the Philadelphia Conference, in 1884, it was proposed to adopt the " watt." but, from the official records, thi6 term does not appear to have been formally adopted. The Paris Congress of 1S89 adopted, on August 31, 1889, the following: The joule defined in terms of the absolute units, and in terms of the ampere, ohm and second. The watt in terms of the absolute units, and also in terms of the joule and second. The bougiedecimale2 defined as the twentieth part of the absolute standard 1. The name "violle," sometimes applied to this standard of light, was not adopted by this Conference, but came into use subsequently. It does not appear to have been formally adopted by any international congress. Tl is standard is equal to about 2.08 carcels, or, approximately, to~20 English candles. 2. The bougie-decimale is a close approximation to the English standard candle, as also to one-tenth part of a carcel. of light adopted by the conference of 1884. The quadrant as the practical unit of induction, defined in centimetres. This congress also defined the following terms:—The period of an alternating current is the duration of one complete oscillation. The frequency is the number of periods per second. The mean intensity of an alternating current is defined by the relation C rT Cmean ~ } C d t. o The effective intensity is the square root of the mean square of the intensity of the current. The effective E. M. F. is the square root of the mean square of the E. M. F. The apparent resistance is the factor by which the effective intensity must be multiplied to give the effective E. M. F. The positive pole of an accumulator is the one which is connected to the positive pole of a dynamo during the charge, and is the positive pole during the discharge. The term interurban is to apply to all telephonic communication between two subscribers or public stations belonging to different groups. The metallic circuit was adopted for urban telephone circuits and for interurban lines. The Frankfort Congress of 1891 adopted, on September 12, 1891, the following: Physical quantities shall be represented in italics. Units shall be represented in Roman type. Physical constants and angles shall be represented by Greek letters. The practical electrical units shall be represented by their initial letters in Roman capitals as follows:—Ampere by A, coulomb by C, farad by F, volt by V, joule by J, ohm by O, watt by W. The proposition made by Mr. Hospitalier,1 to establish an international system of notation, abbreviations and symbols was referred to a committee, to report at the next congress. 1. See Appendix IV. APPENDIX II. The following is taken from the Report of the Committee of the American Institute of Electrical Engineers, on "Unite and Standards.". List Of New Units Practically Needed For Convenience In Dealing With Magnetic Circuits. 1st. Magneto-Motive Farce, and Difference of Magnetic Potential. Simple Definition.—The analogue in a magnetic circuit of voltage in an electric circuit. Strict definition.—The magneto-motive force in a magnetic circuit is 4/T multiplied by the flow of current linked with that circuit. The magneto-motive force between two points connected by a line, is the line integral of magnetic force along that line. Electro magnetic dimensional formula, L* M^ T_i. The absolute unit of M. M. F. is j- X unit current of one turn. The practical unit is r- X ampere of one turn, or one-tenth of the absolute unit—i.e.,0.0706 ampere-turn gives the unit. The prefix kilo would perhaps be occasionally used for practical applications. 2d. Magnetic Flux. Simple definition.—Total number of lines of force or total field. Strict Definition.—The magnetic flux through a surface bounded by a closed curve, is the surface integral of magnetic induction taken over the bounded surface, and when produced by a current is also equal to the line integral of the vector potential of the current taken round the boundary. The uniform and unit time rate of change in flux through a closed magnetic circuit, establishes unit electro-motive force in the circuit. -A -. * ~l Electro-magnetic dimensional formula, L M T . The absolute unit is one c. G. e. line of induction. The practical unit is 10" c. G. S. lines. Fluxes range in present practical work from 100 to 100,000,000 c. G. s. lines, and the working units would perhaps prefix milli- and micro-. 3d. Magnetic Intensity, or induction density. Simple Definition.— Flux per sq. cm. Strict Definition.—The induction density at a point within an element of surface is the surface differential of the flux at that point. Electro-magnetic dimensional formula, L M T . Absolute unit, one o. o. 8 line per sq centimetre. Practical unit, 10' o. o. s. lines per sq. cm. In practice, excluding the earth's field, intensities range from 10<) to 20,"0U lines per sq. cm., and the working unit would perhaps have the prefix milli- or micro-. 4th. Magnetic Reluctance. Definition.—Unit reluctance in a magnetic circuit permits unit magnetic flux to traverse it under the action of unit magneto motive force. —i Dimensional formula, L M° T°. The practical unit is 10-9 the absolute unit. Reluctances vary in present practical work from 100,000 to 100,<'00,000 of these practical units, so that the working unit would perhaps employ the prefix mega-. A. E. Kennelly, Chairman. APPENDIX III. The following specifications are those contained in the recent report of the British Board of Trade Committee on Electrical Standards: The Silver Voltameter. In the following specification, the term silver voltameter means the arrangement of apparatus by means of which an electric current is passed through a solution of nitrate of silver in water. The silver voltameter measures the total electrical quantity which has passed during the time of the experiment, and by noting this time, the time-average of the current, or if the current has been kept constant, the current itself can be deduced. In employing the silver voltameter to measure currents of about one ampere, the following arrangements should be adopted :—The cathode on which the silver is to be deposited should take the form of a platinum bowl, not less than 10 cm. in diameter, and from 4 cm. to 5 cm. in depth. The anode should be a plate of pure silver, some 30 square cm. in area, and two or three millimetres in thickness. This is supported horizontally in the liquid near the top of the solution, by a platinum wire passed through holes in the plate at opposite corners. To prevent the disintegrated silver which is formed on the anode from falling onto the cathode, the anode should be wrapped around with pure filter paper, secured at the back with sealing wax. The liquid should consist of a neutral solution of pure silver nitrate, containing about 15 parts, by weight of the nitrate, to 85 parts of water. The resistance of the voliameter changes somewhat as the current passes. To prevent these changes having too great an effect on the current, some resistance besides that of the voltmeter should be inserted in the circuit. The total metallic resistance of the circuit should not be less than 10 ohms. Method of Making Measurement.—The platinum bowl is washed with nitric acid and distilled water, dried by heat, and then left to cool in a desiccator. When thoroughly dry, it is weighed carefully. It is nearly tilled with the solution, and connected to the rest of the circuit by being placed on a clean copper support, to which a binding-screw is attached. This copper support must be insulated. The anode is then immersed in the solution, so as to be well covered by it, and supported in that position ; the connections to the rest of the circuit are made. Contact is made at the key, noting the time of contact. The current is allowed to pass for not less than half an hour, and the time at which contact is broken is observed. Care must be taken that the clock used, is keeping correct time during this interval. The solution is now removed from the bowl, and the deposit is washed with distilled water, and |