The raw materials are selected with great care to assure chemical purity, but whereas in most glasses the only impurities to be dreaded are those that are either infusible or produce a colouring effect upon the glass, for optical purposes the admixture of other glass-forming bodies than those which are intended to be present must be avoided on account of their effect in modifying the optical constants of the glass.
The metal is chiefly used, as the oxide, for colouring glass and porcelain.
Since in all domesticated cats retaining the colouring of the wild species the soles of the hind-feet correspond in this particular with the Egyptian rather than with the European wild cat, the presumption is in favour of their descent from the former rather than from the latter.
Other Indian cats with a tawny or fulvous type of colouring are probably the more or less modified descendants of the jungle-cat.
Jaguarondi), a chestnut-coloured wild species; but information appears to be lacking with regard to the colouring of the domesticated breed.
Not only is the whole atmosphere Christian in colouring, but we actually find the Greek gods in the guise of Enoch, Elijah, &c., while Philip is a Christian martyr, and Alexander himself a great apostle, even a saint; quotations from the Bible are frequent.
Bartolommeo learned from the younger artist the rules of perspective, in which he was so skilled, while Raphael owes to the frate the improvement in his colouring and handling of drapery, which was noticeable in the works he produced after their meeting.
They are remarkable for skill in the massing of light and shade, richness and delicacy of colouring, and for the admirable style in which the drapery of the figures is handled, Bartolommeo having been the first to introduce and use the lay-figure with joints.
It is found in European streams, and is caught by anglers, being also a favourite in aquariums. The well-known and important industry of "Essence Orientale" and artificial pearls, carried on in France and Germany with the crystalline silvery colouring matter of the bleak, was introduced from China about the middle of the 17th century.
Rhodes was again famous for its pottery in medieval times; this was a lustre ware at first imitated from Persian, though it afterwards developed into an independent style of fine colouring and rich variety of design.
His colouring for the most part is unpleasing, partly owing to his violent treatment of skies with crude blues and orange, and his chiaroscuro usually is much exaggerated.
The bark, very dark externally, is an excellent tanning substance; the inner layers form the quercitron of commerce, used by dyers for communicating to fabrics various tints of yellow, and, with iron salts, yielding a series of brown and drab hues; the colouring property depends on a crystalline principle called quercitrin, of which it should contain about 8%.
An even more complete and minutely detailed view of the sacrificial system is no doubt obtained from the ceremonial manuals, the Kalpa-sutras; but it is just by the speculative discussions of the Brahmanasthe mystic significance and symbolical colouring with which they invest single rites - that we gain a real insight into the nature and gradual development of this truly stupendous system of ritual worship.
Chaptal for a cheap colouring matter, as bright as ultramarine and capable of standing the heat of the porcelain furnace.
He never changed, though he developed and perfected, the manner which he had adopted in Padua; his colouring, at first rather neutral and undecided, strengthened and matured.
The colouring of the steppe changes as if by magic, and only the silvery plumes of the steppe-grass (Stipa pennata) wave in the wind, tinting the steppe a bright yellow.
The general colouring, a faded brown, is somewhat dreary, but the mountain heights and promontories of the west display some grandeur of outline.
The mosaics of the 5th century, in the dome, are the earliest and perhaps the finest at Ravenna for their splendid decorative effect and rich colouring, and are less stiff and conventional than the later mosaics.
Classical forms, variety of treatment and freedom of colouring, while the processions are monotonous and inferior in execution, intended rather to produce a decorative effect than beauty of form.
The mosaics of the choir (547) are due to Justinian, and, though inferior in style, are remarkable for their splendour of colouring and the gorgeous dresses of the persons represented, and also for their historical interest, especially the scenes representing the emperor and the empress Theodora presenting offerings.
Thus its non-liability to freeze (when not absolutely anhydrous, which it practically never is when freely exposed to the air) and its nonvolatility at ordinary temperatures, combined with its power of always keeping fluid and not drying up and hardening, render it valuable as a lubricating agent for clockwork, watches, &c., as a substitute for water in wet gas-meters, and as an ingredient in cataplasms, plasters, modelling clay, pasty colouring matters, dyeing materials, moist colours for artists, and numerous other analogous substances which are required to be kept in a permanently soft condition.
Its solvent power is also utilized in the production of various colouring fluids, where the colouring matter would not dissolve in water alone; thus aniline violet, the tinctorial constituents of madder, and various allied colouring matters dissolve in glycerin, forming liquids which remain coloured even when diluted with water, the colouring matters being either retained in suspension or dissolved by the glycerin present in the diluted fluid.
In it were depicted with a marvellous fidelity, and thorough appreciation of form and colouring (despite a certain conventional 1 Ornithologia, from the Greek opvia-, crude form of dpvcs, a bird, and -aoyia, allied to X6yos, commonly Englished a discourse.
Moreover, both in drawing and in colouring there is frequently much that is untrue to nature, so that it has not uncommonly happened for them to fail in the chief object of all zoological plates, that of affording sure means of recognizing specimens on comparison.
Still the colouring is pretty well done, and experience has proved that generally speaking there is not much difficulty in recognizing the species represented.
Instead of the present boat, with its heavy black cabin and absence of colouring, the older forms had an awning of rich stuffs or gold embroideries, supported on a light arched framework open at both ends; this is the gondola still seen in Carpaccio's and Gentile Bellini's pictures (c. 150o).
New amalgams and methods of colouring have been discovered, and fresh forms have been diligently studied.
The careless gathering of dead leaves and twigs, and the soiling of the cotton by earth or by the natural colouring matter from the bolls, injure the quality.
Now, however, the mottled soaps, blue and grey, are produced by working colouring matter, ultramarine for blue, and manganese dioxide for grey, into the soap in the frame, and mottling is very far from being a certificate of excellence of quality.
The soap is now milled in the form of ribbons with the perfume and colouring matter, and the resulting strips are welded into bars by forcing through a heated nozzle.
Thus, in the treatise known as Physica et Mystica and falsely ascribed to Democritus (such false attributions are a constant feature of the literature of alchemy), various receipts are given for colouring and gilding metals, but the conception of transmutation does not occur.
The general nature of the colouring ingredients employed, and the colour effects produced by them, have already been mentioned.
This colouring power is due to the presence of polychlorite, a substance whose chemical formula appears to be C4 8 1-160018, and which may be obtained by treating saffron with ether, and afterwards exhausting with water.
This crocin is a red colouring matter, and it is surmised that the red colour of the stigmas is due to this reaction taking place in nature.
The explanation of animal (and vegetable) mechanism, colouring, habits, &c., as advantageous to the species or to its ancestors, are only gradually being carried further.
The colouring of ordinary ethnographical maps is necessarily somewhat misleading.
Maria Nuova at Gubbio (1404), extremely well preserved, with bright colouring and fine details.
The coral is generally reddish, but the colouring ranges from light yellow to chocolate-brown.
The "foxy red" colouring of the typical race of north-western Europe is too well known to require description.
The one-sided specialization and the peculiar metallic colouring of the lateral tail feathers mark them as the extreme terms of a degenerative series, whilst the symmetry, likeness of constituent parts inter se, and absence of specialized pigment, as well as the fact that they differ little from any average feather of birds in general, mark the contour feather as primitively simple, and as the starting-point from which the highly elaborated eye-painted tail feather has gradually evolved.
In regard to the first it is noteworthy that house-mice isolated on a small sandbank near Dublin have developed a special colouring of their own; also that distinct local varieties, M.
When heated to above 200 it turns brown and produces caramel, a substance possessing a bitter taste, and used, in its aqueous solution or otherwise, under various trade names, for colouring confectionery, spirits, &c. The specific rotation of the plane of polarized light by glucose solutions is characteristic. The specific rotation of a freshly prepared solution is 105°, but this value gradually diminishes to 52.5°, 24 hours sufficing for the transition in the cold, and a few minutes when the solution is boiled.