424 Mr. H. Pealing on an Anomalous 



o 



a paper millimetre-scale fastened on it in the direction o£ its 

 length, and also with a pin-vice through its centre to grip 

 the steel strip. Two equal weights were then placed on the 

 platform at equal distances (say Rj) from tho axis of sus- 

 pension and Tj the time of a hundred swings noted. These 

 two weights were then placed at a distance R 2 from the axis 

 of suspension and T 2 observed. This was done for a number 

 of weights varying from 100 grams to 1000 grams. When 

 the results were plotted as a graph it was found that T^ — T 2 2 

 was accurately proportional to the weight supported, showing 

 conclusively that the restoring couple per unit angle did not 

 depend upon the weight supported. It will be noticed that 

 the method of experimenting eliminates the effect of the 

 platform and of the finite size of the weights. As the steel 

 strip is much broader than the phosphor-bronze strip, the 

 experiment clearly negatives the view that in the phosphor- 

 bronze strip we have any bifilar property. 



2. Most of the specimens examined had small kinks in 

 them, though some seemed to the eye to be perfectly smooth. 

 Now the presence of a kink means that the strip is both bent 

 and twisted at that point. The bending and twisting will 

 have an effect upon the times of swing of the rods, and of 

 these that of the twist will be the greater. As more weight 

 is added the twist of the strip w r ill be increased, hence the 

 effect of the kink will be greater the greater the load 

 supported. The effect of the twist will be to shorten the time 

 of swing, and so the time of swing for the heavy loads will be 

 shorter than it ought to be, and the restoring couple will 

 appear to be bigger for the heavy loads than for the light 

 loads. That is, a twist in the strip will produce an effect of 

 the nature of the one we are investigating. Experiments 

 with the strips did not support this view. Some of the strips 

 were smooth and free from kinks to begin with, but showed 

 the effect just as distinctly as those which had kinks, and 

 when they had kinks made in them either by design or 

 accident, no difference in behaviour was noted. The effect 

 of a twist was tested in a more definite manner by an expe- 

 riment on the same steel strip described above. The strip 

 was deformed in such a way that it received a twist of about 

 180° but still hung perpendicularly. The time of swing was 

 altered by only a small amount : but when T^— T 2 2 was 

 plotted as ordinate and the weight supported as abscissa? a 

 straight line was obtained as before. It was concluded that 

 the effect of kinks was negligible. 



3. It also occurred to me that as well as overstrains such 

 as kinks, the strips may have overstrains in them owing to 

 the method of manufacture, although the strips may be of 



