Fulminating silver requires the utmost care. It should never be put into phials, nor should it be in any way handled so as to produce much friction. It is the most dangerous preparation that is known. The mere touch of a hard substance will sometimes explode it; and its very preparation is so hazardous that this ought never to be attempted without a mask upon the face with strong glass eyes. The following are three pleasing experiments with preparations of silver: 1. Mix or amalgamate together four parts of silver leaf with two parts of mercury (228) and dissolve this in diluted aqua fortis. To the solution add as much water as will be equal to thirty times the weight of the metals employed. Pour a portion of the above mixture into a phial, and place at the bottom a small piece of silver. After it has stood awhile, little filaments of silver will be seen to shoot up from it somewhat in the form of a shrub. This apparent vegetation is popularly called the _tree of Diana_. 2. A production nearly similar may be obtained by adding a little quicksilver to a solution of nitrat of silver in water. 3. Drop upon a clean plate of copper a small quantity of solution of lunar caustic, or nitrat of silver. In a short time a metallic vegetation will be perceptible, branching out in pleasing forms, and in various directions. 230. _COPPER is a red or orange─coloured metal, about nine times heavier than water. It is the most sonorous of all metals, and, except iron, the most elastic._ _It is found under a great variety of forms, sometimes in masses of pure metal, but, more frequently, in combination with other substances, particularly sulphur._ There are valuable copper mines in every quarter of the world; and the use of copper is probably of greater antiquity than that of any other metal. It is mentioned in the Old Testament; and, at a very early period, domestic utensils and instruments of war were made of bronze, or a compound of copper and tin. Even during the Trojan war, as we learn from Homer, the combatants had no other armour than what was made of bronze. The Greek and Roman sculptors are said to have executed fine works of art in porphyry, granite, and other hard minerals, by means of copper instruments; whence historians have been induced to believe that the ancients possessed the secret of rendering this metal as hard as steel: some of them even imagined that they had the means of converting it into steel.