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Synopsis.-This paper was prepared under instructions from condenser method of determining linear velocities, and the severail thLe Committee on Instruments and Measurements, with a view to inductive methods used in ballistics are treated. forming a basis for the Committee's work in connection with elec-.Measurement of Work: No fine distinction is made between trical measutrements as applied outside of the strictly electrical field. work force and energy: and the standard methods of measuringThe system of classification used is in accordance wvith the natutre of electrical energy with the wattnmeter are omitted, as being outside the the quantity under measurenment, rather than wvith the principle in-scope of the paper. Six types of electrical transmission and absorpvolved; and the subject is treated under nine headings. tion dynamometers are described, and a reference made to recent Measurement of Temperature: There are recogntized two prin-tests, in which the characteristics of a steam locomotive were detercipal methods of electrically measuring temperature; th.e thermo-mined by causing it to pu,ll an electric locomotive, measurement electric circuit, and the effect of temperature upon the resistance of being performed upon the regenerated current of the latter. The many conducting materials. Outlines are izven of the elementary Gilson device for determining over-all efficiency of a powver plant, applications of these, and a number of practical instrutments em-by balancing in an instrument two electrical forces, one representing bodying one or the other of the principles are described. Reference the fuel input, and the other the electrical output is briefly treated. is made to several types of calorimneters em.bodying electrical methods The Measurement of Radiant Energy: Many measurements of temperature measuremnent, and to hygrometers or humridity of radiant energy are mzade by determining the heat generated when meters, in wvhich the principle of the thermocouple has been applied. that energy impinges upon a surface; and these would strictly come A brief description is also given of the optical pyrometer.under the head of temperature measurement. It is realized that it Measurement of Stress, Strain or Small Changes in Physical is difficult to apply the term "non-electrical" or "non-magnetic"Dimensions: General reference is made to the changes which to any radiant phenomenon: and this section of the paper confines take place in both the electrical and mnagnetic characteristics of itself to a bare mention of a number of the best known photoelectric materials when exposed to mechanical stresses, with particular at-cells, used principally in photometry and closely allied work. tention given to resistance e-ffects. Several applications of the carChemical Measurement: The Electrical determination of bon pile in strain determination are mentioned. Recent develop-concentration of the hydrogen ion is treated in some detail. The ments in the use of the piezo-electric effect of certain crystals are de-various electrical a...

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