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IV. A Determination of the Electromotive Force of the Weston Normal Cell in 
Semi-absolute Volts. 
By A. Norman Shaw, M.Sc., 1851 Exhibitioner, and King Research Fellow, 
McGill University, Montreal. 
With a Preface by Prof. H. L. Callendar, F.R.S. 
Communicated by Prof. H. L. Callendar, F.R.S. 
Received November 1,—Read December 11, 1913. 
[Plates 1-2.] 
Contents. 
Page 
Preface by Prof. H. L. Callendar, F.R.S .148 
I. Introduction.150 
II. The theory of the Weber electrodynamometer.151 
(a) The expression for the magnetic couple acting on the suspended system when 
currents are flowing in the coils.151 
(■ b) The expression for the current flowing through the suspended coils.154 
III. The dimensions of the fixed coils.154 
(a) The mean radius.154 
(b) The mean distance between the planes.156 
IY. The ratio of the radii of the fixed and the suspended coils. The dimensions of the 
suspended coils.158 
(a) The method.158 
( b) The theory of the method.159 
when the magnets are undeflected . 161 
(d) The determination of x, the mean distance between the centres of symmetry of the 
large and the small coils.168 
(e) The determination of 6, the mean distance between the planes of the small coils . . 169 
(/) The calculation of the mean radius of the small coils... . . . 169 
V. The calculation of the dynamometer constants.170 
VI. The bifilar suspensions and the determination of their directive force.171 
(a) The suspensions and the theory of the method.171 
(b) The cylindricity of the weights. ...172 
(c) The linear measurements.173 
(c) The determination of the ratio of the currents 
VOL. CCXIY.—A 512. 
u 2 
Published separately, May 12, 1914. 
