SCIENCE AND INDUSTRY. 
almost entirely dependent upon foreign supplies. It is true that one 
English firm—Messrs. Chance Bros., of Birmingham, had successfully 
produced optical glass since its intr oduction. This firm supplied about 10 
per cent. of the pre-war requirements, while the balance came from France 
(30 per cent.) and Germany (60 per cent.). At the factory of Duro- 
glass Ltd., London, two new Hermansen furnaces have been erected, 
and, with other furnaces and equipment, many kinds of chemical and 
resistant glassware are being produced. Such success has also been 
achieved by Chance Bros., that the output of optical glass is now in 
excess of what can be absorbed under favorable conditions. Man 
our gun-sights were exclusively German, e¢.g., dial-sight No. 7 (C. P. 
Goerz, Berlin). This has now been replaced by sights made by Ross 
Bros. and by Beck, the two firms producing over 20,000 to date, making 
as many as 250 a week. In a‘similar way, Aldis Bros. introduced a 
sight for aeroplane guns in 1916, and now 20,000 have been supplied. 
Both members of the firm are University graduates (“ Wranglers”), 
and amongst their achievements are the designing of all the electrical 
projection apparatus used in the Navy, and the 36-inch focus lens 
.(64 inches in diameter), used in such aerophoto work as that at Zee- 
brugge from over three miles high. Such has been the success in the 
production of chemical and scientifie glassware that the annual output 
is now valued at £600,000, and is still increasing. Before the war it 
was practically nil. 
In one field of research there must be co-operation between the glass 
and pottery manufacturers. Much of the success of the glass maker 
depends upon the quality of his melting pots. They must resist the 
corrosive action of the raw and molten material and the intensive heat of 
the furnace. Only the finest and purest of clays can be used in their 
preparation. Any impurities, such as small percentage of iron, may 
injuriously affect the colour or other properties of the metal. The 
urgent need on the part of the Optical Department of the Munitions 
Minister led to the formation of the Osmosis Company, to carry out the 
preparation. of an extremely fine and pure clay by an electrolytic 
method. The process was the result of at least two years’ experimental 
work, based on the discoveries of Count Schwerin. Just prior to the 
war the German company was about to introduce their process into 
England. The English methods, which represent a considerable ad- 
vance on the pre-war German treatment, render possible the recovery of 
a clay substance in a comparatively dry state which has an increased 
plasticity, which sinters at a temperature which might be even 300° 
lower than that of the clay before treatment, which shows a greater con- 
traction and has always a higher melting point. The practical applica- 
tion of this process must have an important bearing on both the pottery 
and glass industries. 
Numerous other researches have been initiated in connexion with 
the corrosion of pots, the temperature for burning, the effect of varia- 
tions in temperature—especially the melting point of the batch and the 
unequal melting of its constituents. This has led to further work in 
pyrometry—using all kinds of instruments—direct reading optical, re- 
cording, and radiation pyrometers. This is most important work, as a 
change of. even 50° in a temperature of 1,000° to 1,400° may cause 
serious trouble. The temperatures must be as accurately determined as 
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