388 Messrs. Holborn and Austin on Disintegration of 
was about 56°, the corresponding refractive index being 
1°48. 
An attempt was made to determine whether the granu- 
lation gave rise to elliptical polarization, the abnormal value 
of the refractive index suggesting the properties of the 
surface-films, which play such an important part in the theory 
of elliptical polarization. No decisive results were obtained, 
for though the phenomenon was found, it seemed impossible 
to eliminate the compcnent reflected from the collodion- 
glass surface, which, as I have shown, may, by interference 
with the component reflected from the air-collodion surface, 
give rise to an elliptical vibration. 
The interferometer failed to show any change in the 
refractive index as the result of frilling, which indicates that 
the effect is confined to the surface. A film deposited on 
glass of such thickness as to produce a shift of half a fringe 
width (sodium light) was frilled by moisture, one half being 
protected by a glass plate. No shift was found at the line of 
demarcation, as would have been the case if the refractive 
index of the film had been raised from 1:48 to 1:96 throughout 
its entire thickness. 
It is my plan to make a further study of the apparent 
effect of the granulation on the refractive index of the surface, 
by the method of total reflexion. 




XLVI. Disintegration of the Platinum Metals in Different 
Gases*. By L. Hotporn and L. W. Austiy+. 
HE disintegration of the platinum metals at high tempera- 
tures appears to be primarily due to their high melting- 
points. The phenomenon which has been observed in many 
connexions in the case of platinum also occurs with rhodium, 
palladium, and in a still greater degree with iridium. Ob- 
servations on the disintegration of these metals in air have 
been carried out by one of the authors?. The metals were 
used in the form of strips 3mm. wide which were heated 
electrically. The “ black temperature,’ S, was measured by 
means of the optical pyrometer §, the temperature Celsius, ¢, 
* This article in somewhat different form was presented to the Berlin 
Academy. Svtz. Ber. der Berl. Akad. p. 245 (1903). 
+ Communicated by the Authors. 
t L. Holborn and F. Henning, Srtz. Ber. p. 938 (1902). 
§ L. Holborn and F. Kurlbaum, Srtz. Ber. p. 712 (1901). 
