It is chiefly used as a pigment and in the manufacture of flint glass.
For the practical measurement of field intensity du Bois has used plates of the densest Jena flint glass.
If, as in common flint-glass spectroscopes, there is only one dispersing substance, f Sy ds = Sµ.s, where s is simply the thickness traversed by the ray.
The crucibles or pots used for the production of optical glass very closely resemble those used in the manufacture of flint glass for other purposes; they are " covered " and the molten materials are thus protected from the action of the furnace gases by the interposition of a wall of fireclay, but as crucibles for optical glass are used for only one fusion and are then broken up, they are not made so thick and heavy as those used in flint-glass making, since the latter remain in the furnace for many weeks.
There were 88 glass 88 It is probable that the flint-glass of that date was very different from the flint-glass of to-day.
