SILVER FISH SILVERING. 



265 



with which they h'ave been explored. In Peru, 

 the annual produce of this metal was formerly as 

 great as 250,000; the major part of which was 

 furnished by the mines of Tasco, of Chota, and of 

 Huantajaya. Chile affords 33,750 per annum. 

 Buenos Ayres contains the celebrated mines of 

 Potosi, discovered in 1545, and which have pro- 

 duce'], according to the estimate of Humboldt, 

 from the time of their discovery, the enormous 

 amount of 258,750,000. These mines have 

 diminished in value of late, though they still rank 

 next to those of Guanaxuato. The celebrated 

 mines of Konigsberg, in Norway, once so rich in 

 native silver, have now become in a great measure 

 exhausted. They are estimated to have produced 

 above 4,500,000 since they were opened in 1623. 

 The most important silver mines of Europe at 

 present, are those of Saxony, Hungary, and the 

 Hartz. The annual produce of Saxony is about 

 56,250 ; while those of the Hartz and of Hungary 

 are each about the same. Within the last twenty 

 years there has been a great increase in the produce 

 of silver from the Russian mines. According to a 

 communication from baron Humboldt, made since 

 his return from Asia, to the editor of Poffendorf's 

 Annalen, it appears that the annual produce of the 

 mines of precious metals of Europe and Asiatic 

 Russia amounts to 25,500 marcs of gold, and 

 292,000 marcs of silver; of which 76,500 of silver 

 and 22,000 of gold are supplied from the Russian 

 empire. The value of all this silver is about 

 529,425. The present annual produce of all the 

 silver mines in the world is probably within 

 4,500,000. 



SILVER FISH. See Gold Fish. 



SILVER TREE (leucadendron argenteum} ; so 

 called from the appearance of the leaves, which 

 are lanceolate and silky. It is a large evergreen 

 shrub, with handsome foliage, a native of the cape 

 of Good Hope, together with the other species of 

 the genus, and is a favourite in green-houses. It 

 belongs to the proteacece, the most remarkable 

 family of plants in the southern hemisphere, and 

 one which contributes largely to give peculiar 

 features to the vegetation of that portion of the 

 globe. More than four hundred species of these 

 plants are known, which are arranged in numerous 

 genera. They are usually shrubs or small trees, 

 but some attain large dimensions: the leaves are 

 simple, entire, or serrated, in most species flat, 

 but sometimes cylindrical or thread-shaped; the 

 flowers are sometimes distinct, upon solitary foot- 

 stalks, or in clusters, spikes, or corymbs, with 

 bractece at the base; sometimes they are sessile, 

 situated upon a common receptacle, surrounded 

 with a many-leaved involucre, or are disposed in 

 scaly cones; the colour is green, yellow, or red: 

 in short, the remarkable differences in the habit, j 

 foliage, and flowers of these plants have given rise j 

 to the name of the order. The greater proportion j 

 of these plants inhabit New Holland, where they j 

 adorn large tracts of country; they are nume- 1 

 rous, likewise, at the cape of Good Hope, but a 

 few species only are found in the southern parts of 

 South America. They are generally favourite 

 green-house plants, and are not delicate with 

 respect to cold ; but their culture, in other respects, 

 requires many precautions. 



SILVERING. The application of silver leaf is 

 made in the same way as that of gold, for which 

 see Gilding. Copper may be silvered over, by 

 rubbing it with the following powder: Two 



drachms of tartar, the same quantity of common 

 salt, and half a drachm of alum, are mixed with 

 fifteen or twenty grains of silver, precipitated from 

 nitric acid by copper. The surface of the copper 

 becomes white when rubbed with this powder, 

 which may afterwards be brushed off and polished 

 with leather. A cheap silvering is prepared as fol- 

 lows: Half an ounce of silver that has been pre- 

 cipitated from aquafortis by the addition of copper, 

 common salt, and muriate of ammonia, of each two 

 ounces, and one drachm of corrosive muriate of 

 mercury, are triturated together, and made into a 

 paste with water; with this, copper utensils of 

 every kind, that have been previously boiled with 

 tartar and alum, are rubbed, after which they are 

 made red-hot, and then polished. The intention 

 of this process appears to be little more than to 

 apply the silver in a state of minute division to the 

 clean surface of the copper, and afterwards to fix 

 it there by fusion; and, accordingly, this silvering 

 may be effected by using the argentine precipitate, 

 here mentioned, with borax or mercury, and causing 

 it to adhere by fusion. The dial-plates of clocks, 

 the scales of barometers, and other similar articles, 

 are silvered by rubbing upon them a mixture of 

 muriate of silver, sea salt, and tartar, and after- 

 wards carefully washing off the saline matter with 

 water. In this operation, the silver is precipitated 

 from the muriatic acid, which unites with part of 

 the coppery surface. It is not durable, but may be 

 improved by heating the article, and repeating the 

 operation till the covering seems sufficiently thick. 

 The silvering of pins is effected by boiling them 

 with tin filings and tartar. Holton mirrors or 

 globes are silvered by an amalgam, consisting of 

 one part by weight of bismuth, half a part of lead, 

 the same quantity of pure tin, and two parts of 

 mercury. The solid metals are to be first mixed 

 together by fusion, and the mercury added when 

 the mixture is almost cold. A very gentle heat is 

 sufficient to fuse this amalgam. In this state it is 

 poured into a clean glass globe, intended to be 

 silvered, by means of a paper funnel, which reaches 

 to the bottom. At a certain temperature it will 

 stick to the glass, which by a proper motion may 

 thus be silvered completely, and the superfluous 

 amalgam poured out. The appearance of these 

 toys is varied by using glass of different colours, 

 such as yellow, blue, or green. To silver looking- 

 glasses, the following articles are necessary: first, 

 a square marble table, or smooth stone, well 

 polished, and ground extremely true, with a frame 

 round it, or a grove cut in its edges, to keep the 

 superfluous mercury from running off; secondly, 

 lead weights covered with cloth, to keep them 

 from scratching the glass, from one pound weight 

 to twelve pounds each, according to the size of the 

 glass laid down ; thirdly, rolls of tin-foil ; fourthly, 

 mercury. The artist then proceeds as follows : 

 the tin-foil is cut a little larger than the glass, and 

 laid flat upon the stone, and with a straight piece 

 of hard wood, about three inches long, stroked 

 every way, that there may be no creases or wrinkles 

 in it : a little mercury is then dropped upon it, and 

 with a piece of cotton wool, or hare's foot, it is 

 spread all over the foil; then, the marble slab 

 being kept nearly level with the horizon, the mer- 

 cury is poured all over the foil, which is covered 

 with a fine paper; two weights are placed near its 

 lower end, to keep the glass steady, while the 

 artist draws the paper from between the silver-foil 

 and the glass. This must be done with great care, 



