. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . they must be refined expressly. Ordinary flint glass is manufac-tured of 100 parts of white sand, 100 parts of minium, and 30 parts of very pure carbonate of density of this flint is about 3-5. A more refracting flint, but one slightly coloured yellow, ismade of 225 parts of white sand, 225 parts of minium, 52 parts of carbonate of potassa, 4 parts ofborax, 3 parts of nitre, 1 part of peroxide of manganese, 1 part of arsenious acid, and 89 parts
. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . they must be refined expressly. Ordinary flint glass is manufac-tured of 100 parts of white sand, 100 parts of minium, and 30 parts of very pure carbonate of density of this flint is about 3-5. A more refracting flint, but one slightly coloured yellow, ismade of 225 parts of white sand, 225 parts of minium, 52 parts of carbonate of potassa, 4 parts ofborax, 3 parts of nitre, 1 part of peroxide of manganese, 1 part of arsenious acid, and 89 partsof cullet of the preceding flint. The melting furnace. Fig. 3285, contains only one covered crucible or pot, into which themixtm-e is gradually introduced by small portions at a time, always waiting until the precedingcharge has become perfectly fluid. Eight or ten hours are required for the whole charge of a strong blast is then applied, and kept up for four hours, to render the mixture perfectly this is effected, a hollow cylinder a &, made of fire-clay, previously heated to redness, and GLASS MACHINEEY. 1685. which does not sink in the melted glass, on account of its greater lightness, is introduced into the pot. Into the cavity of this cylinder a curved iron bar f e is passed, the end of which is heated to redness. By resting this bar on an iron gallows k I, the clay cylinder may be moved in any diiection, so as to mix intimately the various parts of the liquid mass. The bubbles of air are thus driven out, and the whole rendered perfectly homogeneous. This operation must be frequently repeated, to make the glass as perfect as possible. The clay cylinder is then removed, and the furnace allowed to cool slowly for eight days. The pot is then taken out, and is broken after cooling, to retract the glass, on which small polished facets are cut, here and there, so as to judge of its quality in various - parts. This mass is then broken into pieces, and those that
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Keywords: ., bookcentury1800, bookdecade1870, bookidsp, booksubjectengineering
