PHILOSOPHICAL TRANSACTIONS. 
T. The Preparation of Eye-preserving Glass for Spectacles. 
By Sir William Crookes, O.Mf F.R.S. 
Eeeeived October 24,—Eead November 13, 1913. 
Singe March, 1909 —in connection with the Glass Workers’ Cataract Committee of 
the Royal Society-—I have been experimenting on the effect of adding various metallic 
oxides to the constituents of glass in order to cut off the invisible rays at the ultra¬ 
violet and the infra-red ends of the spectrum. The work has been done chiefly in my 
own laboratory. L have been aided by Mr. Harry Powell, of the Whitefriars Glass 
Works, who prepared several pots of coloured glass from my formulae on a much 
larger scale than could be made outside a glass works. From these glasses cylinders 
and sheets were made. 
The main object of this research is to prepare a glass which will cut off those rays 
from highly heated molten glass, which damage the eyes of workmen, without 
obscuring too much light or materially affecting the colours of objects seen through 
the glass when fashioned into spectacles, but the work necessitated an examination of 
the screening properties of glass plates for ultra-violet and luminous light, and there¬ 
fore the research was enlarged so as to embrace the three forms of radiation. 
Radiation from Molten Glass. 
In order to ascertain what rays are given off from molten glass I spent some time 
at the Glass Bottle Works off Messrs. Nuttall and Co., St. Helens, and took many 
photographs of the spectra of the radiations. 
Photo-spectrographic and other examinations were made of the radiation emitted 
from the molten glass under working conditions. Full details of the experiments and 
results are given in this paper. 
At the time I visited Messrs. Nuttall’s works light green bottle-glass was being 
made; the mixture is composed of silica, sodium sulphate, and calcium carbonate or 
sulphate. The materials are melted in a large fire-brick tank, heated by a flaming 
mixture of gas and air playing on the surface. The gas is made some distance from 
the furnace in a “ producer.” Gas and air are conducted by separate channels to the 
upper part of the tank, where they mix and burn, the flame reverberating from the 
arched roof and heating the glass mixture to the requisite degree. 
VOL. CCXIV.-A 509, B Published separately, February o, 1914. 
