One often speaks of a ring as being 14-carat gold, or of 22- or 18-carat watch cases or jewelry, but do all of us know just what we mean by 14, 18 or 22 carat?
Gold is divided into twenty-four parts—that is, pure gold is said to contain twenty-four carats—the carat being just a measurement term. A ring or watch case marked 14K or 18K means that fourteen or eighteen parts of it are pure gold, the balance of the twenty-four carats being some sort of alloy, copper being generally used. If articles of jewelry were made of pure gold they would not wear well, as gold is a very soft metal, and it is, therefore, necessary to mix the gold with some harder substance.
What is an Electro-Magnet?
An electro-magnet is a piece of iron temporarily converted into a magnet by means of a current of electricity sent through a wire which is coiled around it. The wire is usually covered with silk, cotton, gutta percha or some other insulator, to prevent the current from leaping across, and compel it to travel through the whole length of the wire.
The more pure and soft the iron is, the stronger will its magnetism be while it lasts, and the more completely will it disappear when the current stops. Steel is less affected than soft iron for the time, but remains permanently magnetized after the current ceases. Electro-magnets are usually much more powerful than other magnets of the same size.
The iron which is magnetized by the current passing around it is called the core. It is frequently straight, the wire being wound upon it like thread upon a reel; but very frequently it has the shape of a U or horseshoe, the wire being coiled round the two ends and the bend of the U left uncovered.
The Story in a Pin[25]
A pin, so common and so cheap today, was once so expensive that only the wealthy could afford even a few. The term pin-money dates from that time and originally came from the allowance a husband gave his wife to purchase pins.