508 Mr. G. T. Beilby. Phosphorescence caused ~by [Jem. 25, 



which had been observed in metals and other solids when they are 

 flowed by mechanical movement.* The falling off of the phosphor- 

 esence under the long continued action of the rays suggested a failure 

 in elasticity or elastic response analogous to that which is known in 

 metals as "elastic fatigue," while the colour changes appear to be 

 of the same nature as those observed in the crystalline and amorphous 

 phases of the metals, f 



10. When a small fragment of a yellow crystal is bruised on a 

 glass plate by the rounded end of an agate pestle, the bright yellow 

 colour is changed to deep red-brown wherever the pressure has acted 

 so as to cause flow. This colour change is remarkably sharp and 

 distinct. By rolling the pestle firmly over the smaller crystalline 

 specks these are completely flowed into transparent patches with 

 smooth rounded outlines. The colour of the thinnest patches is 

 obviously more intense, as well as much redder, than that of the 

 original crystal, while the thicker patches are of a very intense red- 

 brown by transmitted light. The colour of the flowed patches by 

 reflected light is complementary to that by transmitted light, being 

 green. The crystalline structure of the yellow salt is to all appearance 

 completely replaced by the vitreous granular structure of the amorphous 

 phase. 



11. A small quantity of the amorphous platino-cyanide was prepared 

 by bruising and flowing the yellow crystals on a glass plate. With 

 each portion the operation was repeated several times, that is to say, 

 the flowed patches on the plate were scraped oft', broken up and 

 again rolled with the pestle. In this way, a fairly complete con- 

 version into the amorphous form was obtained. The final product 

 consisted partly of brown powder and partly of deep brown scales 

 with a greenish sheen. The phosphoresence in the /3 rays was reduced 

 to 2/100 of its value, and it appeared as a dull red glow in which an 

 occasional speck of bright green indicated the presence of minute 

 portions of the untransformed crystalline phase. 



12. In my earlier observations on the phase changes A r^. CJ it 



was shown that while the transformation C A takes place by 



mechanical movement of the molecules over each other, as in a liquid, 



the reverse transformation A * C takes place only when a definite 



transition temperature or stability point is reached. The low 

 temperature at which platino-cyanide loses its water of crystallisation 

 presented a difficulty in attempting to bring about the transformation 



A C by heat, but an' encouraging result was obtained on quickly 



raising a small portion of the amorphous salt to 85, for the dark 

 brown scales immediately assumed the bright greenish yellow of the 



* ' Phil. Mag.,' vol. 8, 1904, pp. 258276. 

 f Ibid., also ' Eoy. Soc. Proc.,' vol. 72, pp. 218235. 

 Loc. tit. 



