EDITORIAL. 
which to form and consolidate the boxes. With reference to the proposal 
recently before the Institute of Science and Industry for the establish- 
ment of a small and comparatively inexpensive paper-mill for experi- 
mental purposes, it may be mentioned that the above is just one of the 
problems for which its help would be inyaluable. 
FLUORSPAR FOR GLASS MANUFACTURE. 
An inquiry was recently made of the Institute as to the extent to 
which fluorspar is used in the manufacture of glass, and as to its 
commercial value. Fluorspar (calcium fluoride, calespar, or fluorite) 
has only a specialized use in glass manufacture. Fluorides produce 
opacity, and glass rendered opalescent by them does not transmit red 
light, but is pure milk white. Fluorspar, however, is not a constituent of 
the commoner kinds of glass, such as bottle glass and ordinary window 
glass, and consequently in Australia there is little or no demand for it 
for glass making, but it is used in practically all kinds of opal glass, 
milk glass, or alabaster glass. Soon after the commencement of the 
war, a special Glass Research Committee was appointed in Great 
Britain to investigate the manufacture of certain glasses made only in 
Germany and Austria, and its work was so satisfactory that not only 
were the constituents and the processes of manufacture of these parti- 
cular kinds discovered, but an improvement in quality was effected, and 
the knowledge obtained given to the British industry. Only two 
formule out of twelve or fourteen published contain fluorspar. They are 
what are known as formula No. 2 and formula No. 4:— 
Sorr Grass Tusine. 
(No. 2.) 
Sand ~ =a) .. 67.0 per cent. 
Alumina 53 58 a 8.3 per cent. 
Sodium carbonate .. .. 29.0 per cent. 
Cale. carbonate at .. 9.6 per cent. 
Cale. fluoride A, .. 1.6 per cent. 
Comsustion Tusrna. 
(No. 4.) - 
Sand Sp 68.2 per cent. 
Alumina 6.2 per cent. 
Soda carbonate 5.5 per cent. 
Cale. carbonate 13.0 per cent. 
Cale. fluoride 1.0 per cent. 
Ba. carbonate 8.8 per cent: 
Pot. nitrate .. 4.3 per cent. 
Boric anhydride 5.5 per cent. 
Pure, clear pieces of natural crystal fluorspar are also used in the 
manufacture of the highest grade microscope objectives and other 
lenses. The lenses are ground from the natural crystal and enclosed 
between glass lenses to protect them from injury. 
39% 
