Crystals are prismatic, acicular or scaly in habit; they have a perfect cleavage parallel to the brachypinacoid (M in the figure).
The crystals of prismatic habit represented in figs.
In the Fucaceae, on the other hand, there is a single prismatic apical cell situated at the bottom of a groove at the growing apex of the thallus, which cuts off cells from its sides to add to the peripheral, and from its base to add to the central permanent cells.
In some Pteridophyte stems the apical eel is wedge-shaped, in others prismatic; in the latter case segment~
Of the seven lines he saw, he regarded the five most prominent as the natural boundaries or dividing lines of the pure simple colours of the prismatic spectrum, which he supposed to have four primary divisions.
The formula expressing the optical power of prismatic spectroscopes may readily be investigated upon the principles of the wave theory.
Later, in his article " Chromatics " in the supplement to the 5th edition of this encyclopaedia, he shows that the colours " lose the mixed character of periodical colours, and resemble much more the ordinary prismatic spectrum, with intervals completely dark interposed," and explains it by the consideration that any phasedifference which may arise at neighbouring striae is multiplied in proportion to the total number of striae.
In order to minimize the heating action of the light, it might be submitted to a preliminary prismatic analysis before it reaches the slit of the spectrometer, after the manner of Helmholtz.
5 and 6), which took the form of simple, incised lines, or bands of shallow oval or hexagonal hollows, was more suited to the material than the deep prismatic cutting of comparatively recent times.
Owing to the sacrifice of form to prismatic brilliance, cut-glass gradually lost its artistic value.
In the Silesian process the distillation is conducted in specially constructed muffles of a prismatic shape arched above, which are arranged in two parallel rows within a low-vaulted furnace, similar to the pots in a glass furnace.
Titanium monoxide, TiO, is obtained as black prismatic crystals by heating the dioxide in the electric furnace, or with magnesium powder.
- Zooecia, long and coherent, prismatic or cylindrical, with terminal orifices, their wall thin and simple in structure proximally, thickened and complicated distally.
Nataloin, 2C17H1807ï¿½H20, forms bright yellow scales, melting at 212°-222°; barbaloin, C 17 H 18 0 7, forms yellow prismatic crystals.
When heated in a current of hydrogen it sublimes in the form of brilliant prismatic crystals.
There is generally a tendency in coals towards cleaving into cubical or prismatic blocks, but sometimes the cohesion between the particles is so feeble that the mass breaks up into dust when struck.
The crystals are orthorhombic, with angles similar to those of marcasite; they are often prismatic in habit, and the prism M is usually terminated by the deeply striated faces of an obtuse dome r.
The sulphydrate or hydrosulphide, Ca(SH)2, is obtained as colourless, prismatic crystals of the composition Ca(SH) 2.6H 2 O, by passing sulphuretted hydrogen into milk of lime.
The simplest way of showing dispersion is to refract a narrow beam of sunlight through a prism of glass or prismatic vessel containing water or other clear liquid.
The sodium vapour in the middle is very dense on the heated side, the density diminishing rapidly towards the upper part of the tube, so that, although not prismatic in form, it refracts like a prism owing to the variation in density.
In 1835, in a paper on "The Prismatic Decomposition of Electrical Light," he proved that sparks from different metals give distinctive spectra, which afforded a ready means of discriminating between them.
In the shell of Lamellibranchs three distinct layers can be distinguished: an external chitinous, non-calcified layer, the periostracum; a middle layer composed of calcareous prisms perpendicular to the surface, the prismatic layer; and an internal layer composed of laminae parallel to the surface, the nacreous layer.
The periostracum is produced by the extreme edge of the mantle border, the prismatic layer by the part of the border within the edge.
Thus the growth of the shell in extent is due to additions to the prismatic layer at the edge, its growth in thickness to new layers of nacre deposited on its inner surface.
The upper incisors have persistent pulps, and are curved longitudinally, forming a semicircle as in rodents; they are, however, not flattened from before backwards as in that order, but prismatic, with an antero-external, an anterointernal and a posterior surface, the first two only being covered with enamel; their tips are consequently not chisel-shaped, but sharp-pointed.
At Acireale the lava has assumed the prismatic or columnar form in a striking manner; at the rock of Aci it is in parts spheroidal.
The solid variety prepared by Staedel forms colourless, prismatic crystals which melt at -2° C.; it is decomposed with explosive violence by platinum sponge, and traces of manganese dioxide.
The phenomenon absolutely corresponds to that of fusion and solidification, only that it generally takes place less quickly; consequently we may have prismatic sulphur at ordinary temperature for some time, as well as rhombic sulphur at loo°.
° prismatic < - sulphur," indicating that there is equilibrium at the so-called "transition-point," 95.4°, and opposite change below and above.
Reicher proved with sulphur: aT /aP = AvT/q, v being the change in volume which accompanies the change from rhombic to prismatic sulphur, and q the heat absorbed.
Both formula and experiment proved that an increase of pressure of one atmosphere elevated the transition point for about o 04° The same laws apply to cases of more complicated nature, and one of them, which deserves to be pursued further, is the mutual transformation of cyanuric acid, C 3 H 3 N 3 O 3, cyanic acid, Chno, and cyamelide (Chno).; the first corresponding to prismatic sulphur, stable at higher temperatures, the last to rhombic, the equilibrium-symbol being: cyamelide 1 .?
White arsenic exists in two crystalline forms (octahedral and prismatic) and one amorphous form; the octahedral form is produced by the rapid cooling of arsenic vapour, or by cooling a warm saturated solution in water, or by crystallization from hydrochloric acid, and also by the gradual transition of the amorphous variety, this last phenomenon being attended by the evolution of heat.
The prismatic variety of the oxide can be obtained by crystallization from a saturated boiling solution in potassium hydroxide, or by the crystallization of a solution of silver arsenite in nitric acid.
They are in fact suspended in a state of vapour between our eyes and the photosphere, the dazzling prismatic radiance of which they, to a minute extent, intercept, thus writing their signatures on the coloured scroll of dispersed sunshine.
In 1862 he published a memoir, Intorno alle strie degli spettri stellari, which indicated the feasibility of a physical classification of the stars; and on the 5th of August 1864 discovered the gaseous composition of comets by submitting to prismatic analysis the light of one then visible.
It is a straw-coloured solid, which by fusion under pressure gives prismatic crystals.
The habit of the crystals may be rhombohedral, pyramidal or tabular, rarely prismatic. In fig.
It is a white powder, almost insoluble in water, and when volatilized, condenses in two crystalline forms, either octahedral or prismatic. It is insoluble in sulphuric and nitric acids, but is readily soluble in hydrochloric and tartaric acids and in solutions of the caustic alkalies.
BORAX (sodium pyroborate or sodium biborate), Na2B407, a substance which appears in commerce under two forms, namely "common" or prismatic borax, Na 2 B 4 O 7.10H 2 O, and "jewellers'" or octahedral borax, Na 2 B 4 O 7.5H 2 O.
The crystals of octahedral borax fuse more easily than those of the prismatic form and are less liable to split when heated, so that they are preferable for soldering or fluxing.
It forms dark blue prismatic crystals containing 3, 4, or 6 molecules of water according to the temperature of crystallization.
Prop. 3) "that all refracting substances diverged the prismatic colours in a constant proportion to their mean refraction"; and he drew the natural conclusion "that refraction could not be produced without colour," and therefore "that no improvement could be expected from the refracting telescope" (Treatise on Optics, p. 112).