OBSIDIAN, a glassy volcanic rock of acid composition.
On this account the fibres of tussur or tussore silk tend to split up into fine fibrillae under the various preparatory processes in manufacturing, and its riband structure is the cause of the glassy lustre peculiar to the woven and finished fibres.
Wings of both pairs closely alike; firm and glassy in texture.
These crystallites (q.v.) show that the glassy rock has a tendency to crystallize which is inhibited only by the very viscous state of the glass and the rapidity with which it was cooled.
Katie sat on Kris.s couch, glassy-eyed while her own wound went untreated.
Rhyolitic lavas frequently are more or less vitreous, and when the glassy matter greatly predominates and the; crystals are few and inconspicuous the rock becomes an obsidian; the chemical composition is essentially the same as that of granite; the difference in the physical condition of the two rocks is due to the fact that one consolidated at the surface, rapidly and under low pressures, while the other cooled slowly at great depths and under such pressures that the escape of the steam and other gases it contained was greatly impeded.
The minute globular bodies have occasionally a sub-pearly lustre, and glassy rocks which possess this structure have been called perlites (q.v.).
Included in this group are some rocks which are more properly to be regarded as vitreous forms of trachyte than as glassy rhyolites (Iceland), but except by chemical analyses they cannot be separated.
The doc was grinning and glassy-eyed after his med-gun shot.
As cooling progresses the glassy rock contracts and strain phenomena appear in consequence.
These globular bodies are, in fact, merely the more coherent portions of a perlite; the rest of the rock falls down in a fine powder setting free the glassy spheres.
If a healthy spinal cord be hung up in spirit for a matter of six months or more, a glassy substance develops within it quite like true amyloid.
It melts at 160°, and on cooling solidifies to a glassy mass, which on standing gradually becomes opaque and crystalline.
It may be obtained as a glassy mass, indistinguishable from metaphosphoric acid, by heating phosphoric acid to 215°.
All the wings are of firm, glassy texture, and very complex in their neuration; a remarkable and unique feature is that a branch of the radius (the radial sector) crosses the median nervure, while, by the development of multitudinous cross-nervules, the wing-area becomes divided into an immense number of small areolets.
Since the Rev. William Ellis and a party of American missionaries first made the volcano known to the civilized ' Among the minqr phenomena of Hawaiian volcanoes are the delicate glassy fibres called Pele's hair by the Hawaiians, which are spun by the wind from the rising and falling drops of liquid lava, and blown over the edge or into the crevices of the crater.
The manufacture of porcelain was at the time attracting great attention in England, and while the factories at Bow, Chelsea, Worcester and Derby were introducing the artificial glassy porcelain, Cookworthy, following the accounts of Pere d'Entrecolles, spent many years in searching for English materials similar to those used by the Chinese.
Though glaze begins so early, the use of the glassy matter by itself does not occur till the XVIIIth Dynasty; the earlier reputed examples are of stone or frit.
In the Isle of Eigg, for example, the basalts had already been deeply eroded by river-action and into the river-course a current of glassy lava (pitch-stone) flowed.
Denudation has continued active ever since, and now, owing to greater hardness and consequent power of resistance, the glassy lava stands up as the prominent and picturesque ridge of the Scuir, while the basalts which formerly rose high above it have been worn down into terraced declivities that slope away from it to the sea.
Long and of glassy transparency, except in one or two spots which are dark brown.
The scorifier is taken from the muffle in a pair of tongs and the contents poured into a mould, the lead forming a button in the bottom while the slag floats on top. When cold, the contents of the mould are taken out and the lead button hammered into the form of a cube, the slag, which is glassy and brittle, separating readily from the metal, which is then ready for cupellation.
The glassy conchoidal fracture is a characteristic feature of the crystallized mineral.
In the hard wheats the outer glumes are keeled, sharply pointed, awned, and the seed is elongated and of hard glassy texture, somewhat translucent, and difficult to FIG.
The Polish wheat, rarely if ever cultivated in the United Kingdom, has very large lanceolate glumes, longer than the spikelet, and elongated glassy seeds.
Rosin varies in colour, according to the age of the tree whence the turpentine is drawn and the amount of heat applied in distillation, from an opaque almost pitchy black substance through grades of brown and yellow to an almost perfectly transparent colourless glassy mass.
By adding alcohol to the solution, the acid is precipitated as a white amorphous mass, which becomes glassy at ioo°.
In some processes of lead-smelting, where the minerals treated contain sand, the long calciner is provided with a melting bottom close to the fire-place, so that the desulphurized ore leaves the furnace as a glassy slag or silicate, which is subsequently reduced to the metallic state by fusion with fluxes in blast furnaces.
Standing on the smooth sandy beach at the east end of the pond, in a calm September afternoon, when a slight haze makes the opposite shore-line indistinct, I have seen whence came the expression, "the glassy surface of a lake."
The huntsmen assembled with their booty and their stories, and all came to look at the wolf, which, with her broad-browed head hanging down and the bitten stick between her jaws, gazed with great glassy eyes at this crowd of dogs and men surrounding her.
The French, excited by all that had happened, were talking loudly among themselves, but as they passed Dolokhov who gently switched his boots with his whip and watched them with cold glassy eyes that boded no good, they became silent.
It stands at the mouth of the Veveyse and commands fine views of the snowy mountains seen over the glassy surface of the lake.
Its specific gravity of 4.5 is about twice as great as that of salt and of many other colourless, transparent and glassy minerals not unlike barytes in general appearance.
Gelatin forms a white amorphous powder; the commercial product, however, generally forms glassy plates.
It is certain, however, that most obsidians are very acid or rhyolitic. The dark, semiopaque glassy forms of the basic igneous rocks are known as tachylytes.
In some species it is thin, semi-transparent and glassy, in others massive.
On boiling gelatinous silica with ammonium polytungstate and evaporating with the occasional addition of ammonia, ammonium silicodecitungstate is obtained as short rhombic prisms. On adding silver nitrate and decomposing the precipitated silver salt with hydrochloric acid, a solution is obtained which on evaporation in a vacuum gives the free acid as a glassy mass.
Over the ocean surface, as well as at various depths, float and swim innumerable Hyperiidea - the wonderful Phronima, glass-like in its glassy barrel hollowed out of some Tunicate; the Cystisoma, 4 or 5 in.