418 Mr. H. Pealing on an Anomalous 



of an atom so much, that it is unlikely that the parent and the 

 resultant products would differ in no way chemically. 



Experiments have been made to separate uranium 1 from 

 uranium 2 by depositing; the oxide on electrodes at different 

 potentials. The results have been negative. This agrees 

 with the previous work of Boltwood, and of Soddy, on the 

 same problem. 



Summary . 



The existence of uranium 2 cannot be shown chemically. 

 Uranium 1 cannot be separated or concentrated from 

 uranium 2 by diffusion. If uranium 2 really exists, a fact 

 rendered very probable by the experiments of Geiger and 

 Nuttall, it is not only very similar chemically to uranium 1, 

 but has also the same valency. 



Physical Laboratories, 



The University, Manchester. 



November 1912. 



XLII. On an Anomalous Variation of the Rigidity of Phosphor 

 Bronze. ByH. Pealing, M. Seriate Oliver Lodge Fellow, 

 University of Liverpool *. 



PHOSPHOR-BRONZE strip is used in many delicate 

 physical instruments, and has largely displaced silk 

 tibre for the suspension of light magnetic and electric 

 systems such as are needed in a vibration electrometer and 

 in quadrant electrometers. The strips are very strong, will 

 stand a good deal of rough usage, are readily manufactured, 

 are very uniform in cross-section, and the ratio of the breadth 

 to the thickness is considerable. The last property is parti- 

 cularly useful when the strips are used in a vibrating mag- 

 netometer, where great strength is needed and a very feeble 

 resistance to twisting wanted. De St. Venant calculated 

 that a given couple will produce in a strip whose cross- 

 section is a very elongated ellipse having semiaxes of length 



a 

 a and 6, -^ times the twist it produces in a circular wire of 



lb L 



the same cross-sectional area and length, and a similar 

 relationship holds for a strip of rectangular cross-section. As 

 a set off against these advantages the strips have one very 

 serious disadvantage which does not appear to have been 

 noticed before, viz. the restoring couple per unit angle of 

 twist varies considerably with the load which is supported, 



* Communicated by Prof. L. R. Wilberforce. 



