420 
The Amethystine Colouration produced in Glass by 
Ultra-violet and X-Ray Radiation. 
The amethystine colouration of bottles from the Far 
North of South Australia, where they have been exposed to 
sunlight, has upon several occasions been brought to the notice 
of the Society. . 
In these cases, the colouration was presumably caused by 
solar ultra-violet radiation. The tabled exhibit showed a 
similar colouration produced in glass owing to bombardment 
by X-rays produced by the “Coolidge” Electron type of X-ray 
tube. 
In the walls of the “Coolidge” tube itself, the colouration 
is very beautifully shown, unless masked by a deposit of 
tungsten, caused by volatilization at the focal spot, due to 
excessive energy imputs. In the old gas tubes, it was similarly 
masked, where present, owing to the deposit of tiny particles 
of platinum torn from the target by the bombardment of 
cathode rays. 
eference was made to various work relative to the 
subject, including that of Dr. M. Luckiesh, of the Nela 
or 
in the case of sodium glass, produced by exposure to solar 
upon the application of heat. There appears to be no agree- 
ment as to whether the manganese is present as in solution, 
or in the colloidal form. qur 
e effect when brought about by solar radiation 1$ 
supposedly due entirely to the ultra-violet rays. In manganese 
glass used in connection with electric lighting, the colour has 
only been observed where the electric source of light is very 
rich in ultra-violet rays, such as in a powerful arc 
P 
n, in 
of the similarity of effects on the manganese constituents of 
: Why the effect apparently ceases so abruptly when ins 
wave lengths pass from the ultra-violet to the visible radiation 
1s a point also worthy of investigation. 
pm mum . R. RIDDLE. 
-o Evening Meeting, August 14, 1919. 
