1. J. A. Ewing,Magnetic Induction in Iron and Other Metals(The “Electrician” Printing and Publishing Company, London, 1900), third edition, p. 198.
2. See reference 1, p. 233.
3. For a discussion of conventional methods see Hetenyi,Handbook of Experimental Stress Analysis(John Wiley and Sons, Inc., New York, 1950).
4. In spite of the balanced arrangement, a rather large eccentricity effect remains. This makes dynamic measurements unfeasible unless some means is used to circumvent its effect on the galvanometer. We adopted the simple expedient of using a galvanometer with a sufficiently long period so that it did not respond to these rapid fluctuations.
5. The mechanical vibration which is present when the lathe is running probably tends to reduce this mechanical hysteresis effect. Also, dynamically it is difficult to insure that the torque is increased or decreased regularly.