_a._ By analysis:--
1. Silica, 62·8%; potassa, 22·1%; lime, 15·5%; alumina (with traces of
oxide of iron and manganese), 2·6%. Crown-glass of Bohemia, according to
Dumas. Very beautiful.
2. Silica, 72·5%; soda, 17·75%; lime, 9·75%. English crown-glass;
excellent quality, but not so white as the last.
_b._ Materials used:--
1. Finest white siliceous sand, 64%; purified potashes (dry), 23%; lime,
12%; white arsenic, 3/4%; oxide of manganese, 1/4%. Said to be used in
Bohemia.
2. (Schweigger.) Pure sand, 57%; dry sulphate of soda, 28-1/2%; quicklime,
11-1/2%; powdered charcoal, 3 or 4%. Corresponds to _a_, 2, _above_
(nearly).
3. Pure sand, 40%; soda ash, 24%; lime, 5%; white 'cullet,' 31%, Rather
superior to the last.
CRYSTAL, CRYSTAL GLASS. The 'crystal glass' of England is flint glass' of
superior quality; that of Bohemia is noticed under TABLE GLASS.