To the last is credited the first introduction of covered crucibles to protect the molten glass from the products of burning coal.
"From molten metal to the tempered steel of a blade," Eden replied.
In such cases the molten rock cannot have been homogeneous, and as it flowed along the ground the different portions of it were drawn out into long parallel streaks.
A bottle mould rises and envelops the mass of molten glass.
The latter are made by dipping a small mass of molten colourless glass into an iron cup around the inner wall of which short lengths of white cane have been arranged at regular intervals.
The earth has an enormous molten core that contains vast amounts of energy.
If before this application of the molten glass the metallic leaf, whilst resting on the thin film of blown glass, was etched with a sharp point, patterns, emblems, inscriptions and pictures could be embedded and rendered permanent by the double coating of glass.
The examination of small test-pieces of the glass withdrawn from the crucible by means of an iron rod having shown that the molten mass is free from bubbles, the stirring process may be begun, the object of this manipulation being to render the glass as homogeneous as possible and to secure the absence of veins or striae in the product.
You may melt your metals and cast them into the most beautiful moulds you can; they will never excite me like the forms which this molten earth flows out into.
It is like molten glass cooled but not congealed, and the few motes in it are pure and beautiful like the imperfections in glass.
The heat is then raised in (relative) absence of air, when the two elements named unite into sulphur-dioxide, while a regulus of molten lead remains.
Imitations of natural stones were made by stirring together in a crucible glasses of different colours, or by incorporating fragments of differently coloured glasses into a mass of molten glass by rolling.
De Nehou's process of rolling molten glass poured on an iron table rendered the manufacture of very large plates possible.
Boron dissolves in molten aluminium, and on cooling, transparent, almost colourless crystals are obtained, possessing a lustre, hardness and refractivity near that of the diamond.
7 Vestiges of the Molten Globe (London, 1875).
Guinand, towards the end of the 18th century, by introducing the process of stirring the molten glass by means of a cylinder of fireclay.
In this way the crucible is gradually filled with a mass of molten glass, which is, however, [[Table I]].- Optical Properties.
Thus the dimensions of the largest glass tanks greatly exceed those of the largest steel furnaces; glass furnaces containing up to 250 tons of molten sible to work glass-tanks continuously for many months together; on the other hand, glass is not readily freed from foreign bodies that may become admixed with it, so that the absence of detachable particles is much more essential in glass than in steel melting.
All the earlier attempts in this direction failed on account of the difficulty of bringing the glass to the machines without introducing air-bells, which are always formed in molten glass when it is ladled or poured from one vessel into another.
A sufficient weight of molten glass to form a bottle is gathered and placed in a funnel-shaped vessel which serves as a measure, and gives access to the mould which shapes the outside of the neck.
The famous cameo glass was formed by covering a mass of molten glass with one or more coatings of a differently coloured glass.
As the molten metal is run in, the upward thrust on the outside mould, when the level has reached PP', is the weight of metal in the volume generated by the revolution of APQ; and this, by a theorem of Archimedes, has the same volume as the cone ORR', or rya, where y is the depth of metal, the horizontal sections being equal so long as y is less than the radius of the outside FIG.
GALVANIZED IRON, sheet iron having its surface covered with a thin coating of zinc. In spite of the name, galvanic action has often no part in the production of galvanized iron, which is prepared by dipping the iron, properly cleaned and pickled in acid, in a bath of molten zinc. The hotter the zinc the thinner the coating, but as a high temperature of the bath is attended with certain objections, it is a common practice to use a moderate temperature and clear off the excess of zinc by passing the plates between rollers.
The molten sulphur accumulates on the sole, whence it is from time to time run out into a square stone receptacle, from which it is ladled into damp poplar-wood moulds and so brought into the shape of truncated cones weighing 110 to 130 lb each.
Thereupon Ormazd will hold a judicium universale, in the form of a general ordeal, a great test of all mankind by fire and molten metal, and will judge strictly according to justice, punish the wicked, and assign to the good the hoped-for reward.
In Cumberland, Northumberland, Durham and latterly the United States, the reverberatory furnace is used only for roasting the ore, and the oxidized ore is then reduced by fusion in a low, square blastfurnace (a "Scottish hearth furnace") lined with cast iron, as is also the inclined sole-plate which is made to project beyond the furnace, the outside portion (the "work-stone") being provided with grooves guiding any molten metal that may be placed on the "stone" into a cast iron pot; the "tuyere" for the introduction of the wind was, in the earlier types, about half way down the furnace.
The metal is dimorphous: by cooling molten tin at ordinary air temperature tetragonal crystals are obtained, while by cooling at a temperature just below the melting point rhombic forms are produced, When exposed for a sufficient time to very low temperatures (to - 39° C. for 14 hours), tin becomes so brittle that it falls into a grey powder, termed the grey modification, under a pestle; it indeed sometimes crumbles into powder spontaneously.
They are next steeped in a bath, first of molten ferruginous, then of pure tin.
The leg is formed and a small lump of molten glass is attached to its extremity to form the foot.
Cane is produced from a solid mass of molten glass, tube from a mass hollowed by blowing.
Touches of colour may be added to vessels in course of manufacture by means of seals of molten glass, applied like sealing-wax; or by causing vessels to wrap themselves round with threads or coils of coloured glass.
When the first ball or " gathering 'T has cooled sufficiently, the whole is again dipped into the molten glass and a further layer adheres to the pipe-end, thus forming a larger ball.
In an American process the glass is drawn direct from the molten mass in the tank in a cylindrical form by means of an iron ring previously immersed in the glass, and is kept in shape by means of special devices for cooling it rapidly as it leaves the molten bath.
The funnel is removed, and the plunger, neck-mould and the mass of molten glass attached to the neck are inverted.
Compressed air admitted through the plunger forces the molten glass to take the form of the bottle mould and completes the bottle.
The process consisted in spreading the leaf on a thin film of blown glass and pressing molten glass on to the leaf so that the molten glass cohered with the film of glass through the pores of the metallic leaf.
Its specific gravity is about 9; it is sparingly soluble in water, but readily dissolves in acids and molten alkalis.
A vase decorated with these simple or complex canes is produced by embedding short lengths of the cane on the surface of a mass of molten glass and blowing and fashioning the mass into the required shape.
If the section of the finished tube is to be a triangle, with the enamel and bore at the base, the molten mass is pressed into a V-shaped mould before it is pulled out.
Molten glass is spread upon a large iron plate of the required shape and dimensions.
His silver eyes were molten, his rugged jaw line shaded by two days. growth.
The retorts are charged with molten sulphur from an upper reservoir, which is kept at the requisite temperature by means of the lost heat of the retort fires.
The common monoclinic variety is obtained by allowing a crust to form over molten sulphur by partially cooling it, and then breaking the crust and pouring off the still liquid portion, whereupon the interior of the vessel will be found coated with long needles of this variety.
The character of molten sulphur has been mainly elucidated by the researches of A.
18), of stone pillars to the Canaanite Baal, of the Asherah-pole, molten images and the worship of other gods than Yahweh (Ex.
Molten tin is then poured in, a little powdered salammoniac added, and the tin spread over the inside with a bunch of tow.
It has been also suggested that the word might mean a "molten image" from the sense of "pour."
De la Bastie's process of " toughening " glass consisted in dipping glass, raised to a temperature slightly below the melting-point, into molten tallow.
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.
An effort at a more direct mechanical process is embodied in the inventions of Foucault which are at present being developed in Germany and Belgium; in this process the glass is drawn from the molten bath in the shape of flat sheets, by the aid of a bar of iron, previously immersed in the glass, the glass receiving its form by being drawn through slots in large fire-bricks, and being kept in shape by rapid chilling produced by the action of air-blasts.
As soon as a blowing iron is in connexion with an air jet, the sections of the mould close upon the molten glass, and the compressed air forces the glass to take the form of the mould.
Threads of coloured molten glass were spirally coiled round the body, and, whilst still viscid, were dragged into zigzags with a metal hook.
The duty on flint-glass was imposed on the molten glass in the crucibles and on the unfinished goods.
Most metals when molten are capable of dissolving at least small proportions of carbon, which, in general, leads to a deterioration in metallicity, except in the case of iron, which by the addition of small percentages of carbon gains in elasticity and tensile strength with little loss of plasticity.
For this purpose a cylinder of fireclay, provided with a square axial hole at the upper end, is heated in a small subsidiary furnace and is then introduced into the molten glass.
The mere act of coiling an exact weight of molten glass round the end of a rod 4 ft.