Monthly Archives: March 2014
52.WHAT IS AMBER?
In ancient times, amber was thought to have magical powers. The ancient Greeks and Romans believed it could protect people against sorcerers and disease, so they wore it. The reason amber was believed to have these mysterious powers was its ability to become electrified. When a piece of amber is rubbed briskly, a charge of electricity is produced. This makes amber attract light articles, such as bits of paper. The Greek name for amber was elektron, and this is the origin of our word “electricity.”
51.WHAT ARE CRYSTALS?
Perhaps you think of a crystal as a rare and beautiful mineral or gem. You are partly right. Emeralds and diamonds are crystals. But not an crystals are rare and beautiful. Each tiny particle of salt and sugar is also a crystal! Many of the common substances around us are crystals.
A crystal is the solid form of a substance. It has a definite shape and a definite number of faces because of the arrangement of its atoms. All crystals of the same substance have the same shape, though they may differ in size.
50.WHAT ARE BACTERIA?
Man’s relationship to bacteria is a very interesting one. We all know that many bacteria are harmful. Diseases such as typhoid fever, cholera, diphtheria, pneumonia, and all infections that occur in open wounds are each caused by a particular kind of bacteria. So man wages war on these bacteria.
Yet, without the action of other types of bacteria, life would be impossible on earth! In fact, man actually cultivates certain bacteria because he needs and uses them.
