A very beautiful gilding upon metals, and particularly upon silver, is effected by soaking clean linen rags in a solution of gold made by aqua regia (207). The rags are dried and burnt; and the ashes are carefully preserved. These ashes are used by taking a sound cork, moistening it with a little water, dipping it into the ashes, and then rubbing strongly a portion of them on the surface of the silver, which should be perfectly clean and bright. By this simple and economical process, it will be covered with an extremely thin coating of gold, the colour and brilliancy of which may be heightened by burnishing. The ornaments upon snuff─boxes, fans, and various kinds of trinkets, are merely thin plates of silver, gilded in this manner. The _edges of tea─cups_, and other similar articles, may be gilded, though not in a very durable manner, by applying a thin coat of amber varnish (224), and then placing leaf─gold upon it. When the varnish is dry, the gold is to be burnished. Gold, in a state of solution, is sometimes used for staining marble, ivory, ornamental feathers, and other articles, a purple─red colour, which cannot be effaced. By chemical processes an oxide (21) is obtained from this metal, which is employed for giving those beautiful shades of lilac, rose colour, red and purple, which we observe in glass and porcelain. A _gold powder for painting_ may be made by uniting one part of gold with eight parts of mercury (228), and afterwards evaporating the latter by heat. The article denominated _gold wire_ is generally silver wire gilded, very little wire being made entirely of gold. Its uses are chiefly for embroidery and filagree work. _Gold thread_ consists of flatted silver gilt wire, laid over a thread of yellow silk, by twisting it in a machine with iron bobbins. It is of this, and not of gold, that the article called _gold lace_ is made. The Chinese, instead of flatted wire, use slips of gilt paper, which they interweave in their stuffs, and twist upon silk threads. 228. _MERCURY, in its native state, is called quicksilver, and is found in small globules of shining, silvery appearance, scattered through different kinds of stones, clay, and ores. It is nearly fourteen times heavier than water._ _The principal ore of mercury, and that from which the metal is chiefly obtained, is_ cinnabar. _This is of red colour, and consists of mercury mineralized with sulphur. It is sometimes found in a massive state, sometimes in grains, and sometimes crystallized; and chiefly among rocks of the coal formation._