Rigidity of Phosphor Bronze in Strips. 



205 



Tension in 

 grains weight. 



Torsional rigidity (relative values) for strips 

 numbered I., II., III., & IV. 



I. 



II. 



II,. 



III. 



IV. 



•58 



885 



541 



1430 



366 



764 



•91 



778 



814 



1500 



244 



930 



1-26 



556 



907 



1503 



431 



1053 



29 



401 



754 



1497 



662 



1536 



G-6 



340 



519 



1431 



540 



1792 



14-0 



625 



392 



1469 



705 



1970 



25-0 



1162 



356 



1472 



906 



2100 



31-3 



1612 



635 



1451 





2182 



450 



... 



1093 



1587 



1712 





The first column gives the tension to which the strip was 

 subjected in grams weight. The figures under the columns 

 headed I., II., III., and IV. give the relative values o£ the 

 torsional rigidity of strips I., II. III., and IV. when first 

 set up. The figures under II A. give the relative values 

 of the torsional rigidity obtained when strip II. was 

 annealed. 



Remarks on the Initial Behaviour of the Strips ; and 

 on their use as Galvanometer Suspensions. 



In contradistinction to the behaviour of strips O004 cm. 

 thick, the rigidity for a given tension was found to vary 

 during the time a set of readings were being taken. Ex- 

 amining this matter a little more closely, it is seen that there 

 is no real difference. In the case of the thicker strips it 

 was found that the behaviour of the strips altered in the 

 course of a few days, although nothing more had been done 

 to them further than putting them under tension and making 

 vibration experiments with them. Now in the case of the 

 thinner strips, the time of ten swings for the heavier rods 

 was often as much as forty-two minutes. In this time, much 

 may happen to alter in a permanent manner the behaviour 

 of the strips. The alteration in time of swing was, however, 

 not very great; and when the time of any particular experi- 

 ment with a given rod was reduced to ten minutes or less, 

 very little alteration was observed. This was the case 

 whether the experiments with the smaller tensions were 



