Crystals of barytes may be transparent and colourless, or white and opaque, or of a yellow, brown, bluish or greenish colour.
Windows that can't be broken and can switch from opaque to clear.
In an engraved glass grating there is no opaque material present by which light could be absorbed, and the effect depends upon a difference of retardation in passing the alternate parts.
Another page informed her that the opaque green berries on the thorny vines were gooseberries.
When anhydrous it is a colourless opaque solid which melts at 310 °, and decomposes at about 110o°.
But the wind slides eastward over its opaque surface in vain, till it reaches the living surface beyond.
There are many shades of transparent blue and of opaque blue, yellow and green.
The luminous organs of these beetles consist of a specialized part of the fat-body, with an inner opaque and an outer transparent layer.
It contains about 20% of cinnamic acid in addition to 18 or even more of benzoic. (3) Palembang benzoin, an inferior variety, said to be obtained from Styrax benzoin in Sumatra, consists of greyish translucent resinous masses, containing small white opaque tears.
Solid caustic potash forms an opaque, white, stone-like mass of dense granular fracture; specific gravity 2'1.
The milk of the cow, which may be taken as typical of all others, and is indeed by far the most important and valuable of all, is, when newly drawn, an opaque white fluid, with a yellowish tinge, soft, bland and sweetish to the taste, and possessed of a faintly animal odour.
But, except perhaps in the case of very fine gratings, it is probable that the error thus caused is insignificant; for the incorrect estimation of the secondary waves will be limited to distances of a few wave-lengths only from the boundary of opaque and transparent parts.
The light stopped by the opaque parts of the grating, together with that distributed in the central image and lateral spectra, ought to make up the brightness that would be found in the central image, were all the apertures transparent.
The Romans had at their command, of transparent colours, blue, green, purple or amethystine, amber, brown and rose; of opaque colours, white, black, red, blue, yellow, green and orange.
The superimposed layer, which is sculptured, is generally opaque white.
Hull published accounts of an exact and extensive research, in which the principle had been fully and precisely confirmed as regards both transparent and opaque bodies.
They should be so erected as to present the smallest extent of opaque surface consistent with stability.
Carbonado or " black diamond," found in Bahia (also recently in Minas Geraes), is a black material with a minutely crystalline structure somewhat porous, opaque, resembling charcoal in appearance, devoid of cleavage, rather harder than diamond, but of less specific gravity; it sometimes displays a rude cubic crystalline form.
Long, elliptic-ovate, doubly toothed, pointed, numerously ribbed, hairy below and opaque, and not glossy as in the beech, have short stalks and when young are plaited.
When light proceeding from a small source falls upon an opaque object, a shadow is cast upon a screen situated behind the obstacle, and this shadow is found to be bordered by alternations of brightness and darkness, known as " diffraction bands."
They have a semi-opaque body with an "egg-shell" surface and are delicately tinted with colour.
It melts at 160°, and on cooling solidifies to a glassy mass, which on standing gradually becomes opaque and crystalline.
The nodules from the "blue earth" have to be freed from matrix and divested of their opaque crust, which can be done in revolving barrels containing sand and water.
It is an ironblack, opaque mineral, with metallic lustre; hardness about 6, sp. gr.
If the bead is coloured we may have present: cobalt, blue to violet; copper, green, blue on cooling; in the reducing flame, red when cold; chromium, green, unaltered in the reducing flame; iron, brownish-red, light-yellow or colourless on cooling; in the reducing flame, red while hot, yellow on cooling, greenish when cold; nickel, reddish to brownish-red, yellow to reddish-yellow or colourless on cooling, unaltered in the reducing flame; bismuth, yellowish-brown, light-yellow or colourless on cooling; in the reducing flame, almost colourless, blackish-grey when cold; silver, light yellowish to opal, somewhat opaque when cold; whitish-grey in the reducing flame; manganese, amethyst red, colourless in the reducing flame.
If now we suppose the aperture AB to be covered by a great number of opaque strips or bars of width d, separated by transparent intervals of width a, the condition of things in the directions just spoken of is not materially changed.
Fresnel commenced his researches with an examination of the fringes, external and internal, which accompany the shadow of a narrow opaque strip, such as a wire.
Some coarse kinds are opaque, resembling in this respect jasper, and some writers have sought to restrict the name "bloodstone" to green jasper, with red markings, thus making heliotrope a translucent and bloodstone an opaque stone, but, though convenient, such a distinction is not generally recognized.
It is opaque, except in exceedingly thin slices, such as made for microscopic investigation, which are imperfectly transparent, and of a dark brown colour by transmitted light.
The different kinds of mica vary from perfectly colourless and transparent - as in muscovite - through shades of yellow, green, red and brown to black and opaque - as in lepidomelane; the former have a pearly lustre and the latter a submetallic lustre on the cleavage surfaces.
By the aid of photography it is easy to prepare a plate, transparent where the zones of odd order fall, and opaque where those of even order fall.
At other parts of the field the effect is the same, in accordance with the principle known as Babinet's, whether the imaginary screen in front of the object-glass is generally transparent but studded with a number of opaque circular disks, or is generally opaque but perforated with corresponding apertures.
We conclude that, with a grating composed of transparent and opaque parts, the utmost light obtainable in any one spectrum is in the first, and there amounts to I/wr 2, or about 6, and that for this purpose W a and d must be equal.
Among the revisions may be adduced some addition to our knowledge of dyspepsia, attained by analytic investigations into the contents of the stomach at various stages of digestion, and by examining the passage of opaque substances through the primae vine by the Rntgen rays.
Beckerite, a rare amber in earthy-brown nodules, almost opaque, said to be related in properties to gutta-percha.
BALANOGLOSSUS, the general name given to certain peculiar, opaque, worm-like animals which live an obscure life under stones, and burrow in the sand from between tide-marks down to the abyssal regions of the sea.
The least wind raises clouds of fine dust, which fill the air, render it so opaque as to obscure the noonday sun, and make respiration difficult.
We have now to consider the amplitude due to a single element, which we may conveniently regard as composed of a transparent part a bounded by two opaque parts of width id.
Babinet, the brightness of a lateral spectrum is not affected by an interchange of the transparent and opaque parts of the grating.
The usual process was to gather, first, a small quantity of opaque white glass; to coat this with a thick layer of translucent blue glass; and, finally, to cover the blue glass with a coating of the white glass.
It forms colourless transparent crystals, soluble in one and a half parts of cold water and in eight parts of alcohol, which on exposure to ordinary air become opaque through absorption of carbonic acid, which forms a crust of basic carbonate.
Africanum, and like opaque bdellium lacks the white streaks which are characteristic of myrrh and bissa bol, both are acrid, but have scarcely any bitterness or aroma.
Graphite is black and opaque, whilst diamond is colourless and transparent; it is one of the softest (H= I) of minerals, and diamond the hardest of all; it is a good conductor of electricity, whilst diamond is a bad conductor.
An important character, and one by which the mineral may always be recognized, is the perfect cubical cleavage, on which the lustre is brilliant and metallic. The colour of the mineral and of its streak is lead-grey; it is opaque; the hardness is 2 2 and the specific gravity 7.5.
This result, which, accepting the possibility of having an absolutely opaque enclosure of uniform temperature, was clearly proved by Balfour Stewart for the total radiation, was further extended by Kirchhoff, who applied it (though not with mathematical rigidity as is sometimes supposed) to the separate wave-lengths.
When chemically pure, which is rarely the case, blende is colourless and transparent; usually, however, the mineral is yellow, brown or black, and often opaque, the depth of colour and degree of transparency depending on the amount of iron present.
Glessite, a nearly opaque brown resin, with numerous microscopic cavities and dusty enclosures, named from glesum, an old name for amber.
If the grating be composed of alternate transparent and opaque parts, the question may be treated by means of the general integrals (§ 3) by merely limiting the integration to the transparent parts of the aperture.
With the exception of the heavier flint (lead) glasses, these can be produced so as to be free both from noticeable colour and from such defects as bubbles, opaque inclusions or " striae," but extreme care in the choice of all the raw materials and in all the manipulations is required to ensure this result.
One variety is that in which transparent brown glass is so mixed with opaque white and blue as to resemble onyx.
With the experience thus gained in manipulating the vacuum, the achievement of thoroughly verifying the pressure of radiation on both opaque and transparent bodies, in accordance with Clerk Maxwell's formula, has been effected (Physical Review, 1901, and later papers) by E.
The substance of the fungus is dry and opaque with a peculiar smell suggesting ripe apricots or plums. The flesh is whitish tinged with yellow.
It resembled a studio apartment with a real bed and dresser, a restroom cordoned off by opaque curtains in one corner, a small study where he kept his war docs, a kitchenette, rugs, and a small living area.
A b c is fixed at the top of a small tent furnished with opaque curtains so as to prevent the diffused daylight from overpowering the image on the paper, and in the darkened tent the images of external objects are seen very distinctly.
The ground of these cameo glasses is most commonly transparent blue, but sometimes opaque blue, purple or dark brown.
All the other examples have the lower portion covered in like manner by a network of circles standing nearly a quarter of an inch from the body of the cup. An example connected with the specimens just described is the cup belonging to Baron Lionel de Rothschild; though externally of an opaque greenish colour, it is by transmitted light of a deep red.
Roman glass beads are always drawn out, and nicked off hot, with striation Iengthways; except the large opaque variegated beads which are coiled.
The pitchstone of the Scuir of Eigg is at its margins characterized by a dull semi-opaque matrix which seems to be the result of secondary devitrification.
Although the matter can be fully treated only upon the basis of a dynamical theory, it is proper to point out at once that there is an element of assumption in the application of Huygens's principle to the calculation of the effects produced by opaque screens of limited extent.
In any large collection of fragments it would be easy to find eight or ten varieties of opaque blue, ranging from lapis lazuli to turquoise or to lavender and six or seven of opaque green.