Then magnetize the first needle by stroking it with a bar magnet. When it is again rested on the glasses it will be found that the needle no longer balances, but dips downward. *Permanent Magnets* have a number of useful applications in the construction of scientific instruments, voltmeters, ammeters, telephone receivers, magnetos and a number of other devices. In order to secure a very powerful magnet for some purposes a number of steel bars are magnetized separately, and then riveted together. A magnet made in this way is called a compound magnet, and may have either a bar or a horse-shoe shape. Magnets are usually provided with a soft piece of iron called an armature or "keeper." The "keeper" is laid across the poles of the magnet when the latter is not in use and preserves its magnetism. A blow or a fall will disturb the magnetic arrangement of the molecules of a magnet and greatly weaken it. The most powerful magnet becomes absolutely demagnetized at a red heat, and remains so after cooling. Therefore if you wish to preserve the strength of a magnetic appliance or the efficiency of any electrical instrument provided with a magnet, do not allow it to receive rough usage. CHAPTER II STATIC ELECTRICITY If you take a glass rod and rub it with a piece of flannel or silk, it will be found to have acquired a property which it did not formerly possess: namely, the power of attracting to itself such light bodies as dust or bits of thread and paper. Hold such a rod over some small bits of paper and watch them jump up to meet it, just as if the glass rod were a magnet attracting small pieces of iron instead of paper. The agency at work to produce this mysterious power is called _electricity_, from the Greek word "Elektron," which means _amber_. Amber was the first substance found to possess this property. [Illustration: Fig. 17.—An Electrified Glass Rod will Attract Small Bits of Paper.] The use of amber begins with the dawn of civilization. Amber beads have been found in the royal tombs at Mycenae and at various places throughout Sardinia, dating from at least two thousand years before our era. Amber was used by the ancient world as a jewel and for decoration. The ancient Syrian woman used distaffs made of amber for spinning. As the spindle whirled around it often rubbed against the spinner’s garments and thus became _electrified_, as amber always does when it is rubbed. Then on nearing the ground it drew to itself the dust or bits of chaff or leaves lying there, or sometimes perhaps attracted the fringe of the clothing. The spinner easily saw this, because the bits of chaff which were thus attracted would become entangled in her thread unless she were careful. The amber spindle was, therefore, called the "harpaga" or "clutcher," for it seemed to seize such light bodies as if it had invisible talons, which not only grasped but held on. This was probably the first intelligent observation of an electrical effect.