Australia and California are the gold lands. It is found principally in three situations: in sands which have been washed from the mountains, in little pockets in the rocks, and in veins of quartz. From the first it is separated by simply washing away the lighter materials, from the last situation it is procured by quarrying the rock, crushing it with stamping machines, then washing with water to remove the pulverized quartz, and gathering up the powdered gold with quicksilver. The mercury is removed by vaporizing. Gold is nineteen times heavier than water, extremely ductile, and the most malleable of all substances. Silver is abundant in the mountains of the west. It is usually found in the form of black sulphide (Ag₂S) or horn-silver (AgCl). When unpolished it is perfectly white, and is called dead or frosted silver. All are familiar with the properties of this attractive metal. Just now its producers in Colorado seem to fear its displacement from its important position in the coinage of the country. In nitrate of silver (AgNO₃) we have a material that perpetuates the faces of our friends, many a goodly landscape, and marvelous picture.
MAGNET GATHERING IRON FILINGS.—A MAGNET WILL ALSO ATTRACT NICKEL FILINGS.
Platinum stands at the extreme limit of the elementary world in point of weight, being twenty-one and fifty-three hundredths times heavier than water. Russia has almost a monopoly of the production of this metal. It is about the value of gold, and to the chemist is of immense importance, on account of its high point of fusibility, which is over 4,000°. It is so ductile that it can be drawn out into wire so fine as to be invisible to the naked eye. This microscopic wire is used for centering the field of view in the finest telescopes.
EARTH’S CRUST AND CENTER.
Our earth is called “terra firma;” it is regarded as the very embodiment of stability, but every waving outline, every hill and mountain peak, not less than the rumbling of the earthquake, and the bursting forth of volcanic fires, indicate that it has been, and may again be, the scene of mighty disturbances. Indeed, upon reflection, one wonders that we can live on it at all. The temperature of the earth increases one degree for every fifty feet as we approach the center. At this rate, at the depth of fifty miles the heat would be sufficient, according to Humboldt,[11] to melt the hardest rocks. Fifty miles is one one-hundred and sixtieth of the earth’s diameter. It thus appears that if we should have a globe three feet in diameter full of molten liquid, surrounded by a covering of infusible material one eighth of an inch in thickness, that film of solid matter would represent the earth’s crust. Think of it!
A “LEAD TREE.”
Ex.—Place in a glass a dilute solution of acetate of lead; suspend in it a strip of zinc. Some of the lead will be precipitated in crystals upon the zinc. This is caused by the zinc taking a portion of the acetic acid, and thus forming a new compound called zinc acetate, thereby liberating some of the lead.
Besides, that awful, fiery sea within is subject to tides, currents and convulsions that constantly threaten to disrupt and destroy this crust. It is supposed that masses of water percolate through cracks and fissures until they reach the internal fires and are suddenly converted into steam at an enormously high temperature, which gives it such tremendous expansive force as to shake the globe itself. This action, combined with the violent explosion of gases, creates the sublime and dreadful phenomena of