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magnificent windows of Gothic cathedrals, with their gorgeous colors, produced by combinations of metals in the molten state. The false precious stones made in Paris with so much perfection from heavy strass-glass are colored with metallic oxides in as lasting a manner as the genuine stones.
The first precious stone reproduced, not only in its appearance, but its real nature, and in all its component parts, is the lapis-lazuli, the sapphire of the ancients, not to be confounded with the sapphire of our modern jewelers. This untransparent stone, of a magnificent azure-blue color, was most highly prized by the ancient Hindoos, Assyrians, Persians, Jews, Egyptians, Greeks, etc.; and this irrefragably refutes the erroneous theory of some archæologists that the ancients were unable to distinguish the blue color. When pulverized, this stone furnishes the surpassingly beautiful ultramarine color with which the artists of the middle ages delighted to paint the mantle or gown of the Virgin Mary, although they had to pay the most extravagant prices for the pigment, which they always charged in the bills of those who had ordered a sacred picture from them. Some fifty or sixty years ago, Gmelin, the German chemist, discovered that this most beautiful of blue colors could be artificially produced by heating argillaceous earth with soda, sulphur, and carbon; and now that Guimet, the French chemist, has practically introduced this process, Europe manufactures annually about 100,000,000 pounds of this pigment, most of which is produced in Germany.
At a very early period chemists devoted their attention to the artificial reproduction of rubies and sapphires, which, as we have said before, consist of nothing but crystallized argillaceous earth, colored by minute particles of metals. Several decades ago, the chemist Gaudin succeeded in obtaining small ruby pellets from pure argillaceous earth, precipitated from dissolved alum and moistened with chromate of potash. The color of these rubies, according to the quantity of chromate which they contained, was either that of a rose or bordering on purple. The pellets were so hard that they easily cut glass, garnets, and topazes; but they were not crystals, and their transparency was by no means perfect. Similar experiments were made by the chemists De Bray, Sainte-Claire Deville, Caron, Sénarmont, Ebelmann, and others. It was long acknowledged that a crystallization of argillaceous or beryl earth had to be obtained, and to that end it was necessary to reduce them with the requisite quantities of the coloring metallic combinations into a state of fiery liquefaction. Boric acid was selected for that purpose, because when heated it slowly evaporates. It appears as vapor in volcanic countries, and is especially obtained in Tuscany. The belief that this fiery means of reduction had played in Nature a part in the formation of precious stones was perfectly justifiable; and so boric acid was placed in comparatively large quantities with argillaceous or beryl earth in open platinum crucibles, which were subjected to a long-con
tinued heat in porcelain furnaces. In fact, as soon as the larger portion of the boric acid has evaporated, there are evolved from the fiery, liquid mass small rubies, sapphires, or emeralds. This was discovered some twenty years ago, but the crystals were too small to make the process a remunerative one.
Far more satisfactory were the results of Frémy's recent experiments. They are based upon a different principle, namely, that of separating the argillaceous earth slowly from its usual combination with silicic acid, as it is found in Nature everywhere, by bringing to bear upon
it a substance of stronger affinity for the acid. In consequence, small crystals of argillaceous earth are formed in the fiery, liquid “mother-liquor," which, in the course of further separation, grow slowly. In the glass-factories of M. Feil, quantities of this “motherliquor" of precious stones, weighing from twenty-five to fifty pounds, were easily kept in a fiery, liquid state for two and three weeks, and in this way very favorable results were obtained. The most advantageous process turned out to be the separation of the argillaceous earth from the silicic acid by means of oxide of lead, for which purpose a mixture of equal parts of pure porcelain-clay and red-lead was placed in a large crucible of fire-proof clay and exposed for weeks to an intense red heat. Usually, the lead also extracts the silicic acid which the walls of the crucible contain, and eats holes through them. Hence, to avoid losses, the precious-stone crucible should be placed in another.
After several weeks of patient waiting, vividly recalling the expectant watching of the old alchemists at their crucibles in which the philosopher's stone was to be created, the crucible is taken out and cooled. After destroying the crucible, the contents are found to consist of two strata, above a glassy one, consisting principally of silicate of lead, and below a crystalline one, containing the most beautiful crystals of argillaceous earth in round clusters. If nothing but argillaceous earth and red-lead has been placed in the crucible, these crystals are as colorless as glass. They will cut glass and rock-crystal, nay, even the very hard topaz; in short, they are precious corundums or diamond-spar, so called because, next to the diamond and crystalline boron, it is the hardest of all stones.
Now rubies, sapphires, and Oriental emeralds, are nothing but colored corundums, and the former two can be easily obtained by the addition of the requisite quantities of the coloring metallic combinations. When there was added to the mixture of argillaceous earth and red-lead two or three per cent. of bichromate of potash, the crystals showed the beautiful rose-color of the ruby; when only a small quantity of that salt was used, and simultaneously a still smaller quantity of oxide of cobalt was added, sapphires were obtained. The precious stones thus produced, as a rule, are covered with a firm crust of silicate of lead, which is best removed chemically by melting it with oxide of lead or potash, or by means of hydrate of fluor-spar. Among a number of pounds of
such crystals of argillaceous earth which the inventors submitted to the Academy, there were numerous pieces that could not be distinguished at all from natural rubies and sapphires. They possessed their crystalline shape, their weight, hardness, color, and adamantine lustre, although the latter was not altogether faultless.
How completely the imitation of Nature has succeeded, may be inferred from a peculiarity which the artificial rubies have in common with the natural ones : both, upon being heated, lose their rose-color, and do not recover it until they are cooled again. The diamond-cutters who were requested to grind these artificial rubies found them not only as hard as the natural ones, but in many instances even harder; they were not long in blunting their best tools made of the hardest steel. For the use of watch-makers they are, perhaps, better than the natural stones.
But jewelers, too, are certain, sooner or later, to derive a great deal of benefit from these discoveries. The rubies hitherto obtained, although very beautiful, did not equal the first-class natural stones; but they are only the first productions of a new process, and it is decidedly creditable to the inventors that they immediately divulged their method without trying to mystify the public. Now others, too, may follow up this new branch of a promising alchemy. Perhaps more time should be given to the crystals for their formation, for Nature had a great deal of time for such productions, and it was owing to this fact, perhaps, that it achieved such glorious triumphs. There can be no doubt but that, at some future time, these crystals of argillaceous earth will be colored also green, yellow, and purple, and that thus the precious stones, which were hitherto distinguished as Oriental emeralds, topazes, and amethysts, from inferior stones of the same name, will be produced. The addition "Oriental,” in this connection, has no geographical meaning, and was applied by jewelers to the harder and better classes of emeralds, topazes, and amethysts. Perhaps these Oriental stones will be cheaper at an early day than the inferior ones, and the middle classes may wear as brilliant stones as princesses do
Diamonds, too, were the objects of similar processes, that is, by trying to bring about a slow separation of carbon from its combinations. However, Chemistry has to admit here that it cannot demonstrate, with any degree of accuracy, how Nature really produced the diamond. Some think that it could only have been formed at an enormously high temperature ; others consider its
slow formation in a cold condition more probable; nay, there are scientists who regard it as the production of some organic agency, because there are frequently discerned in them green, cellular formations resembling certain algæ. In view of the rapid progress of synthetic chemistry, it might, perhaps, be as well for the diamond to maintain even in the eyes of chemists its time-honored
“adamas "—that is, the indomitable one. For what should the
“fine lady” wear in the future if the prince of precious stones should follow the example of those standing closest to its throne, and allow itself to be reproduced for a few shillings?
THE TEREDO AND ITS DEPREDATIONS.
By Dr. E. H. VON BAUMHAUER,
COMMISSIONER TO THE CENTENNIAL EXHIBITION FROM HOLLAND.
hermaphrodites, Quatrefages has taught us that they are of both sexes and that the ratio of males to females is about one to twenty. The females are oviparous. The eggs are expelled by the branchial siphon: Quatrefages found them in that siphon and in the branchial canal itself. The mode of fecundation is, however, unknown; it is supposed that, in that act, two different teredos project their siphons and bring them in contact.
As regards the metamorphoses which the eggs undergo, either in the branchial tubes or in the water, nothing has been added to what was made known through the researches of Quatrefages in 1849. That naturalist has taught us that the eggs pass through the series of modifications, from the starting-point, which one meets with in the examination of all animals—i. e., the formation of the germinative area and of the vesicle of Purkinje, the disappearance of this and the breaking up of the vitellus. The eggs undergo their development in the branchial cavity of the mother; the embryos resemble very small, rounded animalcula of vesicular form, and are provided with vibratile cilia, by the aid of which they have regular movements, and probably are expelled from the branchial cavity into the siphon. In a third phase of development the bivalve shell is formed, the foot appears on the outside, the vibratile cilia form a sort of crown, and the embryo thus possesses the faculty of locomotion as well by creeping as by swimming. The development of the eggs takes place from time to time, and especially in the month of June, although even as late as the 29th of July Harting found eggs in all the teredos which he opened. The development of the eggs progresses very rapidly; in four days they pass out of the embryonic state, fully equipped for living in wood. Toward the end of June, Kater observed them in large numbers on the surface of wood, and by the 15th of July he found them in the interior in the form of perfectly-developed teredos. Even in the month of December, but no later, he saw young teredos enter into pieces of wood placed by
1 Extract from the “ Archives of Holland," vol. i., translated by Edward R. Andrews.
design in the water; at that time they were from eight to fourteen days old, and, although very small, they resembled in every respect older teredos.
Teredos penetrate wood naturally by very small openings in a direction perpendicular to the surface (Figs. 12 and 15, C); then they generally turn about in order to follow the direction of the woody fibres,
usually upward, but sometimes downward. Although they do not enter into the earth or mud, one generally finds the first traces immediately above the line of the mud in which piles are driven; it is at this point that piles destroyed by the teredo generally break off.
When the teredos are lodged in a
piece of wood, one recognizes them by D very small holes on the surface, and the
extremely delicate tubes which project from them (Fig. 12, e, d). These are the siphons, only one of which shows at first, the other appearing later. These siphons are generally kept outside the wood in the water, but the slightest touch causes the animal to retract them. One of them is shorter and larger than the other, but they both seem to serve for the expulsion of the fæces, which largely consist of particles of wood reduced to a very fine powder. It is known that the teredo does not perforate wood for nourishment, but only to procure a suitable abode ; the woody substance, detached in the boring, passes through the intestinal canal, and then is expelled in the form of a
very fine white substance by one of FIG. 12.-Wood exposed from November, 1874, to September, 1876, in crib at Pier
the siphons, generally, according to No. 1, New York, North River, twenty
M. Vrolik, by the shorter, but some
times by the longer. The long siphon appears to serve principally for the introduction of food, which consists of infusoria, diatoms, and other inferior animalcula, which the sea-water brings with it into the siphons. It is nevertheless still uncertain whether the matters expelled through the longer siphon come directly from the intestinal tube, or if they are first introduced from outside with the inflowing water to be expelled again after a short sojourn inside.
The teredo requires for respiration a clear, pure water. It has often