The gyroscope toy

   A toy gyroscope spins like a top. In fact, this toy is often called a gyrotop. The chief parts of the gyrotop are a wheel which is weighted around the rim and a rod, or axle, that goes through the center of the wheel. In spinning a gyrotop, a string is first wrapped around the axle. Then the string is pulled suddenly as the end of the axle is rested on something solid. Once a gyrotop starts spinning it does not change its position until it runs down. Its axle keeps on pointing in the same direction. It can remain in amazing positions as it spins. The whirling of the heavy wheel keeps it from falling.
   Not all gyroscopes are toys. Some are used in boats as compasses. Some are used to keep boats and airplanes on a straight course. A gyroscope used in this way is called a gyropilot. One nickname for a gyropilot is "metal Mike." In fighting at sea during a war gyroscopes are used to guide torpedoes. On some ships enormous gyroscopes are used to help keep the ships on an even keel so that passengers will not be seasick.
   Only toy gyroscopes are set to spinning by the pulling of a string. As a rule other gyroscopes are set in motion and kept spinning with electricity.

The ginkgo tree

   In America the ginkgo is often called the maidenhair tree. Its leaves are fan-shaped. Although the ginkgo is a distant relative of the pines and firs, it is not an evergreen. Its leaves turn yellow and fall off in the autumn.
   The fruit of the ginkgo has an unpleasant smell. But the seed inside is good to eat.
   This tree has lived on the earth for a very long time. The ginkgo trees we have now are almost exactly like their ancestors of ten million years ago.
   Once the ginkgo had many close relatives. But they all disappeared. The ginkgo, too, would probably have disappeared if the Chinese and Japanese had not planted ginkgo trees in their temple gardens. They thought of these trees as sacred.
   Ginkgoes are found in many cities. They are well liked partly because they have few insect enemies.

The ginseng plant

   The plant we call ginseng grows wild in China and in the eastern part of the United States. It is also cultivated in the United States, China, and Japan.
   Ginseng has pretty red berries in the fall, but the plant is not raised for them. It is raised for its roots. They bring high prices in China. So far as anyone knows, the roots are of little real use. But for hundreds of years the Chinese have thought that the roots would cure many kinds of sickness. There are Chinese stories which tell how wild animals protect this wonderful plant. There are other Chinese stories which tell that the plant travels underground to escape its enemies.
   Probably the shape of the ginseng roots gave the Chinese the idea that they would be good medicine. "Ginseng" means "likeness of men." Wild roots bring higher prices than cultivated ones because they are more likely to be shaped like men. Cultivated roots look very much like parsnips.

Gourami fish

   Gourami is a fish belonging to the family Osphromenidae, celebrated for its fine flavor. Its original home is the rivers and streams of the East Indian Archipelago. The gourami, Osphromenus olfax, has an oblong, oval body of a greenish brown color, banded by dark, vertical stripes in the immature fish. Though generally about two feet in length, it sometimes attains a length of six feet. The average weight is 12 or 14 pounds. The gourami builds a nest of grass and roots attached to aquatic plants and is assiduous in the care of its young. It is omnivorous in diet and extremely tenacious of life. Attempts have been made to introduce this fish into France but they have not been very successful. It is a highly valued article of food in the East Indies.

Charles Gounod

   Charles Francois Gounod, 1818-93, French composer, was born in Paris. His father was a painter, his mother a pianist, and from her he received his first musical instruction. He entered the Paris Conservatoire in 1836 where his teachers were Halévy, Paer, and Lesueur, all operatic composers. He was awarded the Prix de Rome in 1839, as a result of which his interest in the music of the church developed, and the stage was set for the lifelong struggle in Gounod's soul between the sacred and the secular, the mystical and the worldly, a struggle apparent in much of his creative work. Returning to Paris via Austria and Germany, he became organist of the chapel of the "Missions Etrangeres," wrote considerable religious music, and even considered entering the priesthood. However, about 1850 he was commissioned to compose an opera, Sapho. Several others followed before he achieved a real success in 1859 with Faust, upon which his fame still chiefly rests. Herein is the struggle between the flesh and the spirit set forth with especial clarity. La reine de Saba, Mireille, Romeo et Juliette and others followed at intervals, during which time Gounod was also producing masses, oratorios, and other sacred music. Among these are Messe de Sainte Cecile, Messe du Sacre Coeur, The Redemption and Mars et vita. Though praised by Saint-Saens, this music, according to most critics, tends toward monotony and heaviness.
   Among the many honors bestowed upon him, Gounod was made a member of the Institute de France in 1866 and grand officer of the Legion of Honor in 1880. He continued to compose until his death at St. Cloud, though he was content in his later work to use methods he had used repeatedly before. His music is sweet and melodious, often for too extended a period without the relief of contrast and dramatic intensity.

What is liquefied gas?

   All gases may be changed into liquids by the combined effects of lowering their temperature and allowing them to expand from a sufficiently high pressure.
   Before air is liquefied it must first be freed from dust, moisture, and carbon dioxide which, at the low temperatures used, would solidify and thus obstruct the expansion valves. The remaining gas is compressed and allowed to expand in a series of three or four cycles, the pressure becoming successively greater. The cooling effect of the final expansion becomes great enough to lower the temperature to —191 °C., at which point the gas begins to change into a liquid. Liquid air thus made may be separated into oxygen and nitrogen by fractional distillation, nitrogen (bp — 195.8 °C.) boiling off first and leaving liquid oxygen (bp —182.9 °C.). Both oxygen and nitrogen are prepared commercially in this way. Liquid air may also be used to produce high vacua, to maintain very low temperatures and to dry and purify gases.
   Liquid air is considerably richer in oxygen content than is gaseous air. It is a nonconductor of electricity, supports the combustion of fuels immersed in it, and has a pale blue color. A coil of lead wire immersed in liquid air becomes elastic, due to the low temperature. Liquid oxygen is strongly magnetic. It is used with fuels to propel ROCKETS and rocket bombs.
   Hydrogen (bp -252.7 °C.) and helium (bp -269 °C.) are the gases most difficult to liquefy. The former yields the lightest known liquid, its specific gravity being only 0.07. Many gases are liquefied before being marketed because liquids are easier to handle and occupy less space than gases. Chlorine, ammonia, sulfur dioxide, and carbon dioxide are among the commercial gases sold in liquid form.
   Hydrocarbon gases from oil wells, as well as those produced in the cracking of petroleum, may be liquefied and sold in steel cylinders, for heating and lighting to residents who do not have access to natural or manufactured gas.
   Other liquefied hydrocarbon gases, such as ACETYLENE, are important industrial fuels. The vaporization of some liquefied gases, such as ammonia, sulfur dioxide, METHYL CHLORIDE, and FREON, produces the cooling effect used in many refrigerators.

What is Genetics?

   GENETICS is the biological science that deals with inheritance and variation among living organisms. In the reproduction of plants and animals it is obvious, even to the casual observer, that parents and offspring tend to resemble each other in many respects. For example, when a particular species of plant reproduces, it gives rise to other plants with the same general characteristics; the same holds true for the various species of animals. Even in human beings certain traits can be traced through families. This transmission of traits from one generation to another, and consequently the resemblance between closely related organisms, is called heredity.
   Although there may be many hereditary resemblances between individuals, no two individuals are ever exactly alike. All organisms, particularly higher animals, show some differences or variations. These may be due to the definite manner in which traits are distributed to the offspring, to environmental factors, such as temperature, light, moisture, food supply, etc., or to many other causes. Genetics, then, is that branch of the biological sciences that is concerned with the mechanisms of heredity and variation and with the relationship between the two phenomena.