TI. Absolute Measurements of a Resistance by a Method based on that of Lorenz. 
By F. E. Smith, A.R.C.Sc. 
(.From the National Physical Laboratory .) 
Communicated by R. T. Glazebrook, MA ., F . B . S . 
Received October 27,-—Read December 11, 1913. 
Principal Contents. 
Page 
Historical note on the absolute measurement of resistance.28 
Introductory. 33 
Method of Lorenz...35 
General description of instrument.38 
Motor and fly-wheel. 40 
Rotating discs and their supports.40 
Rotating conducting wires... . 41 
Contact brushes and their lubrication.42 
Coil supports. 46 
Lubrication of bearings. 46 
Regulation of speed. 47 
Recording the speed.47 
Magnetic tests.49 
Construction and measurement of coils.51 
Diameters of coils. 53 
Axial lengths and pitch... . 61 
Erecting and adjusting the instrument.64 
Insulation tests ..65 
Effective diametral distance of segments.66 
Measurement of distance between the coils.68 
Calculation of mutual inductance.70 
Correction for conicality ..76 
Correction for variation in pitch. 79 
Effect of iron of motor.81 
Arrangement of circuits ..83 
Standard resistances used. 86 
Setting of coils to be co-axial.87 
Determination of resistance in absolute measure. 93 
Probable errors.99 
Conclusions.107 
YOL. CCXIV.-A 510. E 2 Published separately, March 19, 1914. 
