It is generally in the form of plates, many of them huge, all clumsily thick, and frequently of a dingy, ill-vitrified yellow on the back.
There is, however, another quarter to which vitrified or encaustic ware may be ascribed, in so far at least as regards improved methods and more important results.
As we pass to the later works of English potters, we become conscious of the difficulty of following our usual plan of dividing them into pottery, stone-ware with vitrified fracture, and porcelain.
Earthen-ware with vitrified fracture may be either glazed or in biscuit.
This ware, distinguished, as we have seen, by its vitrified fracture, although long known in the East, does not appear in Europe until between the thirteenth and fifteenth centuries.
When these large vitrified masses either struck against one another in the air, or fell on the ground, vivid sparks of fire proceeded from them, which communicated to every thing that was combustible.
The walls of Vitrified Forts are of about half the thickness of unvitrified, and appear to belong to the Late Celtic Age.
The operation called smearing, consists in giving an external lustre to the unglazed semi-vitrified ware.
Lime-marl has been found to answer well for making the body of the hearth-sole, as it absorbs the vitrified litharge freely, without combining with it.
This is a kind of semi-vitrified ware, called dry bodies, which is not susceptible of receiving a superficial glaze.
Bar iron made entirely from ore without admixture of cinder, or vitrified oxide, is always reckoned worth 10s.
When that is removed the metal becomes more homogeneous, having no crystalline carbon present to counteract its transition into pure iron; much of the silica and manganese are also vitrified together, and run off in the finery cinder.
The first consists of a fusible earthy mixture, along with an infusible, which when combined are susceptible of becoming semi-vitrified and translucent in the kiln.
The materials of every kind of glass are vitrified in pots made of a pure refractory clay; the best kind of which is a species of shale or slate clay dug out of the coal-formation near Stourbridge.
The oxides thus produced, are dissolved and carried down into the porous cupel in a liquid state, by the vitrified oxide of lead.
These tears proceed usually from small portions of semi-vitrified matter which fall from the vault of the furnace, and from their density occupy the bottom of the cuvettes.
Portland cement clinker, however produced, is a hard, rock-like substance of semi-vitrified appearance and very dark colour.
The Chinese, accustomed from a very early period to fire their pottery to a high temperature, produced vitrified stonewares before any other nation.
The dross, or recrement, of a metal; also, vitrified cinders.
The sand, which occupies the interior parts of the earth, is a vitrified matter; and the layers of clay, by which its surface is covered, are nothing but the same sand having been decomposed by the operation of the waters.
It was remarked, with respect to vitrified pigments, that colour depends on cohesion.
In vitrified and crystallised compounds, colour depends on cohesion: sufficiently separate the particles, and the colour more or less disappears.
There are only two colours which cannot yet be obtained; these are opaque vermilion and lemon yellow in a vitrified state.
Ready-made tanks are to be had of steel, concrete, or vitrified tile.
The so-called "Vitrified Forts" of Scotland which have been the subject of so many ingenious and baseless theories, form another interesting class of native works.
To attempt to assign a date for these primitive forts or vitrified sites would be manifest folly, but even to apportion them to one or more of those less definite periods is difficult.
Nevertheless it is worthy of some note, that although upwards of seventy years have elapsed since Mr. Williams published his account of vitrified forts, no single example, so far as I am aware, has been discovered south of the Tweed.
But neither the interest nor the importance of this inquiry is exhausted when we have established the undesigned origin of vitrified sites.
An open ditch is, however, far better replaced by vitrified tile, six inches in diameter, which entirely prevents surface pollution, and which costs only about ten cents a running foot.
The house-drain, or the pipe which carries the wastes from the house to the point of final disposal, is generally made of vitrified tile, and in ordinary practice is five inches inside diameter.
If vitrified pipe is used, the joints must be made with the greatest care, and every precaution taken to prevent leakage.
This is the site of one of the celebrated vitrified forts, concerning the creation of which there has been so much learned discussion.
In the vitrified forts of a few parts of Europe, we find data that the Humes and Gibbons have disregarded.
But some of the vitrified forts are not upon tops of hills: some are very inconspicuous: their walls too are vitrifiedin streaks.
The vitrified forts surrounding England, but not in England.
So archaeologists, in their medieval dread of excommunication, have tried to explain vitrified forts in terms of terrestrial experience.
The vitrified forts of Scotland, Ireland, Brittany, and Bohemia.
The fire, by melting the matter, produced a vitrified crust, and the basis of all the matter which composes the globe is glass, of which sand and gravel are only fragments.
They were vitrified when the globe received its form, which necessarily supposes that the matter was in fusion.
It is better therefore to use tinned vessels for mixing the preservative with the butter, and to pack it either in wooden casks, or in jars of the Vauxhall ware, which being vitrified throughout, require no inside glazing.
It is better therefore to use tinned vessels for mixing the preservative with the butter, and to pack it either in wooden vessels, or in stone jars which are vitrified throughout, and do not require any inside glazing.
It is better therefore to use tinned vessels for mixing the preservative with the butter, and to pack it either in wooden vessels, or in jars of the Vauxhall ware, which being vitrified throughout, do not require an inside glazing.
We also passed large surfaces of white rock, which were sprinkled all over with dark, hollow balls, of a vitrified substance.
Evidence of volcanic action appeared along the canyon in the form of vitrified fragments and occasional masses of lava resembling rock.
It is remarkable that the ancient legends of Cuchullin and the sons of Uisneach connect them with those remarkable structures termed vitrified forts.
Two vitrified forts in the neighbourhood of Lochness are called Dundeardhuil.
Dun Scathaig, Dun mhic Uisneachan, and Dundheardhuil, are all vitrified forts, and the latter is a common name for them.
Vitrified brick are made from clay of such a character that when heated to the required temperature they will fuse into a glassy texture.
Sometimes the absorption test is specified for paving brick, but it is rarely a vitrified brick that will pass the rattler tests which fails to pass a reasonable absorption test.
If the brick is not properly burned it will be only partly vitrified and therefore not of maximum durability.
When both the tire and the road surface strongly resist distortion (as steel tires on vitrified brick paving), the resistance to translation is low but the factor of impact is likely to be introduced.
The other parts of the summit are covered by huge fragments of brickwork, tumbled confusedly together; and what is most extraordinary is that they are partly converted into a solidvitrified mass.
The immense masses of vitrified brick which are seen on the top of the mound appear to have marked its summit since the time of its destruction.
Minton, their last production in this class being a Parian combining the red colour of the terra cotta, with the advantages of a vitrified porcelain.
Under this agency the particles enter into combination, and if the process is carried far enough, the ware may become partially vitrified and acquire a certain amount of transparency.
The least will belong to ware pressed with stiff clay gently fired; the greatest, to that cast with liquid slip and brought to the vitrified state.
The ivory figures, too, have been inlaid and filled up with vitrified material.
These are the hard materials to be vitrified by the fluxes, which are carbonate or oxide of lead, boracic acid or borax, potash or soda, carbonate of lime or barytes.
For the hard porcelain, the glaze is made from felspar containing a variable quantity of quartz, or, as in Germany, from quartz vitrified by an addition of gypsum, the melting of which in both cases requires a very high temperature.
