Since 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. I 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 therefore the research was enlarged so as to embrace the three forms of radiation.