204 Mr. H. Pealing on an Anomalous Variation of 



thin phosphor-bronze strips ; and to obtain further informa- 

 tion about the effect of annealing the strips. In the experi- 

 ments I made with strips 0*0043 cm. thick I showed that 

 the discrepancy, which amounted in the case of one strip 

 examined to 200 per cent., was entirely removed by annealing 

 it. The simplest way of explaining this result is that the 

 rigidity is constant over the range of the experiments when 

 annealed, and that there is no bifllar action. The width of 

 the strip was printed by mistake 0'48 cm. The value stated 

 should have been 0*048 cm. In the case of strips 0*001 cm. 

 thick I was never able entirely to remove the discrepancy, 

 and this I attributed to imperfect annealing, but offered no 

 proof for that statement. That is to say, the experiments 

 did not definitely decide that there was no bifllar action in 

 the very thin strips. 



Experiments with Phosphor Bronze Strips. 



The dynamical method was used to determine the rigidity 

 of the strips of which relative values only were obtained. 

 One end of the strip used was soldered to a piece of brass 

 which was rigidly held in a torsion head, and the other was 

 soldered to a light copper stirrup which supported in a 

 horizontal position circular brass rods whose weights varied 

 from *3 grin, to 45 grm., and whose lengths were about 9 cm. 

 The whole was enclosed in a glass cover. When a rod of 

 given weight had been placed in the stirrup, the time of a 

 convenient number of swings was observed. From this, 

 relative values of the restoring couple per unit angle of 

 displacement could be calculated. 



It was found that the initial behaviour of the strips was 

 entirely different in amount, and partly also in the kind of 

 variation, from what had been observed before. 



The table gives the results obtained with four strips the 

 dimensions of each of which were 25 x 0"024 x 00012 cm. 

 They were supplied to me through the kindness of Professor 

 Wilberforce, of Liverpool University. The thickness given 

 of the strips is approximate only. The strips were perfectly 

 smooth and free from kinks. They were manufactured by 

 Messrs. Johnson and Matthey. Strips I., II., and III. were 

 consecutive lengths of strip off a new bobbin of material, 

 while one metre of strip separated when on the bobbin 

 the end of the third strip from the beginning of the 

 fourth. 



