Leather

   Of all the ancient industries that of the manufacture of leather is one of the most interesting on account of the convertibility of an easily descomposed substance into one which resists putrefaction. The manufacture of leather is as old as history itself. In China the manufacture and use of leather was known before the Christian era, and in Egypt leather has been found in mausoleums of the ancients, showing us that rations in the remote ages of the past were practised in the art and left slight traces of their high civilization to be admired today. The Persians and Babylonians passed the art over the Greeks and Romans and so down through the different medieval nations to us. The Amer¬ican Indians were also well versed in the art of making leather. Although their method of tanning was entirely different from that of the ancient races, the fact remains that they also discovered a way of treating the skins of animals in such a way as to prevent the putrefaction of animal tissues.

Water bath

Water Bath is a bath of fresh or salt water, as distinguished from a vapor bath. In chemistry, a copper vessel, having the upper cover perforated with circular openings from two to three inches in diameter. When in use it is nearly filled with water, which is kept boiling by means of a gas burner, and the metallic or porcelain basin containing the liquid intended to be evaporated is placed over the openings mentioned above.

Antibiotics in the 20th century

   Alexander Fleming discovered penicillin in 1928. Penicillin stopped the growth of disease-carrying bacteria. Thus it could help cure illnesses caused by these bacteria. In the years after Fleming's discovery, other substances were discovered to have similar effects. Streptomycin, which was discovered in 1944, attacked bacteria that could resist penicillin. All of these substances are called antibiotics, and after 1945 they transformed the fight against disease. They cured certain illnesses, such as tuberculosis, that previously could not be treated, and they made surgery safer from infections. Antibiotics were also used to improve the health of animals that are used for food. Although some bacteria came to resist antibiotics, these substances became essential in reducing sicknesses and providing more food.

Ships of the Vikings

   When the Europeans of the 9th century prayed to the Lord "From the wrath of the Norsemen . . . deliver us," they had good reason to pray. The Norsemen, or Vikings, as they are often called, sailed out of the harbors of Scandinavia in their swift longboats for some two centuries. Their purpose was to raid and rob the richer lands to the south and southeast.
   The Vikings were as good sailors as they were shipbuilders. Their drakkar was a longboat with a dragon on its prow and a large decorated single sail. Some 16 oarsmen sat on either side of the ship helping it to move through the waters from the coast of England as far south as Spain and Italy. The drakkar's "sister" ship was the snekkar, a somewhat larger boat with a snake as a figurehead on the prow.
   The Vikings' raids took them to the British Isles where they succeeded in settling forces at the mouth of the Thames River. From this and other bases they sent forces to raid London, Paris, and Dublin. They left a permanent memorial in France where the region of Normandy takes its name from the Normans, or Norsemen, raiders and settlers of old. More distant voyages took these hardy sailors to Iceland, Greenland, and, in about the year 1000, to North America. Halfway round the globe Viking traders could be found sailing south along the rivers of Russia to trade their fur and amber for the silver, spices, and brocades of the region.

The "Green Revolution"

   As a result of intensive research, scientists in the 1960's discovered ways of producing seeds that yielded much more rice and wheat than ever before. The new seeds were also improved by the use of better fertilizers and by advances in the techniques of irrigation.
   The ability to feed large numbers of people became increasingly critical as the world's population grew (currently stands at 7 billion). Unfortunately, most of the fastest-growing countries were also the poorest and the least able to feed themselves. In the 1980's, for example, Ethiopia was unable to cope with the long period of drought and famine that plagued the country, and millions of people starved to death.

Where is Ithaca (Odyssey) located?

Ithaca is one of the Ionian Islands, situated west of Greece and east of Cephalonia, from which it is separated by a narrow channel. Its area is about 38 square miles, the surface being mountainous and the coast steep and rocky. Vineyards and olive and other orchards cover the mountain sides. Fishing is carried on by the inhabitants, another industry being the production of olive oil. Its population is about 3,040 (2001).
Ithaca is supposed to be the site of the castle of Ulysses, the principal character in Homer's Odyssey. Excavations were made by Schliemann in 1869, which corroborated sites named by Homer.

Ulysses

Waterproof Materials

Waterproof Materials are any substances used to prevent infiltration of water or (inaccurately) other liquids. Typical waterproofing materials, all having commercial uses, are tar, oils, rubber, asbestos, asphalt, oil paints, aluminum hydroxide, metallic soaps, waxes, paraffin, resin, varnish, and cellophane.

Tar is used for caulking wooden boats and for waterproofing ropes, roofs, tarpaulins, and roads. Asbestos is likewise used for roofs, and asphalt has similar uses for roads. Asphalt varnishes are also used for protecting iron from weathering. Oils are used both as film in protecting machinery from water vapor and in impregnating fab¬rica, as raincoat cloth, instrument cases, and oiled shoes. Oils are also the solvent in most paints and bind the particles of pigment into a thin, resistant layer. Rubber may be used in sheet form as a cover, but it is usually vulcanized to a fabric, which gives the rubber durability, or it is deposited by electro-chemical means into the pores of the fabric. Any water-insoluble substance may be used in place of rubber, in such connection, providing it can be conveniently precipitated. Such substances are aluminium hydroxide, metallic soaps, waxe», paraffin, resin, asphalt, tar, and varnish. To make fabrics impervious to water and at the same time to allow for ventilation, recourse is had to waterproofing the yarn and then weaving the fabric out of this yarn. An important addition to the family of waterproof materials is cellophane, a cellulose product from which umbrellas, wrappings and raincoats are made.
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Suite (music)

   A suite, or partita, is the earliest type of musical composition containing a series of discrete sections, or movements. The suite was developed in the 16th century as a series of dance tunes, usually composed in one key.
   These tunes were so arranged as to present strong contrasts between slow and fast tempos and dignified and gay moods. The four basic movements of the classical suite are: the allemande (Fr., "German"), a quiet dance in moderate tempo, composed in common time; the courante (French, "running"), a lively dance, often complex in its rhythms; the sarabande, a stately dance of Spanish origin in triple time, rich in harmonic embellishment; and the jig or gigue, a rapid and lively dance, also in triple time. A prelude, not derived from any dance form, was later customarily included at the beginning of the suite, and one or more additional dance forms, such as the minuet, gavotte, bourrée, chaconne, and passacaglia, were also sometimes inserted, generally between the saraband and gigue. The classical suite reached its perfection in the examples by the German composer Johann Sebastian Bach. In the 18th and 19th centuries the classical suite gradually merged with and was superseded by the sonata. Modern compositions called suites are only loosely related to the original form; they are primarily symphonic works, characterized by considerable freedom of structure and tonality, and cast either in abstract forms or in greatly modified dance forms.

Laser applications

   In 1960 a device called a laser was invented. It could store energy and release it all at once in an intense beam of light. This beam remained straight, narrow, and very concentrated, even after it had traveled millions of miles. Its uses were extraordinarily varied—a perfect example of the combination of scientific discovery and engineering applications. Lasers were used in surgery to weld damaged tissue in the eye, to burn away skin growths, and to repair decayed parts of teeth. They were used to measure distances. A mirror placed on the moon by the Americans who landed there allowed scientists to calculate the distance to the moon more accurately than ever before.

   Lasers helped engineers make tunnels and pipelines straight. They enabled manufacturers to cut precisely into hard substances, such as diamonds. Lasers also transmitted radio, television, and telephone signals. They made it possible to show three-dimensional pictures on a television or film screen. Thus one invention had effects in dozens of activities.

Jackstones game

Jackstones (also called jacks, fivestones, jackrocks, onesies, knucklebones, or snobs) is a game played by one or more persons with from one to five small pebbles or bits of iron. Regular iron jackstones have six knobbed prongs. The game may be played in several ways. There is tossing and catching in all of them. The five stones may be held in the palm of the hand and thrown up together and caught on the back of íhe hand. The jack may be tossed up and caught alternately on the palm and the back of the hand, the player counting five for each successful catch. The player who reaches the highest score wins. Sometimes four stones are laid on the ground. The player losses the jack and catches it, picking up a stone from the ground each time, while the jack is in the air. This method may be varied by holding the four stones in the hand and laying one on the ground between each toss and catch. Sometimes the jackstones are laid in a pile. The player arranges them in a figure, as the four corners of a square or in a straight line, this between tosses.

Plastics, the first synthetic substances

   The first synthetic substances—substances that do not occur in nature—were developed by chemists in laboratories in the 1800's. A few of these sub¬stances began to have wide applications. For example, celluloid was used to make movie films, and bakelite was used for electrical equipment. It was not until after 1945, however, that these substances, called plastics, began to appear in every area of life. By the mid-1960's, for example, there was more synthetic rubber than natural rubber in the world.
   Plastics became an essential part of daily existence. They were used to equip and furnish kitchens. They changed the way buildings were constructed and affected the manufacture of objects from toys to cars. They completely altered the appearance as well as the manufacture of most of the things people use every day, from tooth-brushes to telephones. Synthetic fibers were woven into easy-care fabrics for clothing, upholstery, and many other uses.
   Many plastics were made from oil products. The production of plastics, therefore, depended on the unpredictable nature of international oil prices. Nevertheless, plastics continued to be essential to modern life in the 21th century.

The Frogs (Aristophanes)

The Frogs representation

   THE FROGS is a satire by the Greek dramatist Aristophanes. The play was awarded first prize when presented at the Lenaean festival of 405 B.C. and still retains popularity, although generally considered one of his less skillful plays. Written shortly after the death of Euripides, the drama portrays the patron god of tragedy, Dionysus, as determined to go down into Hades and bring the tragic playwright back to earth. While the chorus of frogs, from which the comedy takes its name, sings lyrics of the rain and marshes, the god is ferried across the river by Charon to the door of Pluto. A contest ensues between Euripides and Aeschylus to discover which is the better playwright, and the god decides in favor of the latter. This part of the play seems inconsistent with what has gone before, and has led to the suggestion that the original Frogs was hastily revised at the death of Euripides. At any rate, Dionysus abandons his earlier plan, and it is Aeschylus he brings back to earth.

Jack Straws game

   Jack Straws is a familiar parlor game. It is played with straws or with strips of bamboo, wood, ivory, bone, or the like. The straws are tumbled in a confused heap on a table. The players take turns. The first withdraws straws, one at a time, as long as he can do so without joggling the heap or moving any other straw. The right to play then passes to the next. The player who has the most straws at the conclusion of the game wins.
   The pieces may be withdrawn with the finger or angled for with a hook provided for the purpose.

The beginnings of Space exploration

Space Shuttle

   Engineers had experimented with rockets, which could fly at enormous speeds, in the 1930's and 1940's. Finally, in 1957, Soviet engineers devel¬oped one that could fly fast enough to break out of the earth's gravitational pull. The Soviet rocket placed a small artificial satellite, called Sputnik, into orbit around the earth. In 1959 the Soviets crashed a rocket into the moon. In 1961 they built one with enough power to put a person in orbit around the earth. The United States responded with its own huge program for space exploration. In 1969 this effort succeeded in transporting two American astronauts to the moon.
   The main results of space exploration in the 1970's came from unmanned spacecraft. Orbiting satellites transmitted television, telephone, and radio signals around the earth, vastly improving communication. Orbiting cameras transformed weather forecasting. The American Voyager spacecraft provided important new information about the makeup of other planets.
   A new phase of space exploration began with the launch of the first space shuttle, Columbia, in 1981. By 1986 reusable shuttles, which contained elements of both the traditional space capsule and the airplane, had completed two dozen successful missions. Early that year, however, the explosion of the shuttle Challenger and the lost of its crew temporarily halted the human explo¬ration of space.

History of postal service

Postal History

Post stamp

Although letters have been stamped only since 1847, there has been mail service in the United States since 1639. Stage coaches, the Pony Express, and trains carried mail during various times in our history. Today most mail is sent by airplane.
In Europe carrier service goes back to the Roman Empire. The magnificent Roman roads were used to get messages from the provinces to the capital. The English postal service has been operating since the 1600's, when it took over the routes of the royal mail.
Over 2,000 years earlier the Greek historian Herodotus described the Persian mail service of Cyrus the Great, saying, "There is no mortal thing faster than these messengers." Marco Polo encountered a series of postal stations in China around 1300 a.d. At the same time the Aztecs in Mexico had relay stations and runners to carry the news between villages.
Mail has been getting through for a long time. Perhaps in the next century it will travel to the Moon.

Ivanhoe (novel)

   Ivanhoe is a novel by Sir Walter Scott. It was written about 1819, when the famous "Wizard of the North" was at his best, and appeared in print the following year. The tale combines romance and adventure. The scene is laid in England in the days of Richard I. The plot is one of the green-wood, archery, Saxon outlawry, Norman oppression, tournament, castle storming, and orderly battle. Gurth, the swineherd; Wamba, the jester; Brian de Bois-Guilbert, the knight templar; Locksley, the green-coated outlaw; Friar Tuck, the fat monk; sturdy Cedric, the Saxon; haughty Front de Boeuf; Richard Coeur de Lion, disguised as the Black Knight, are leading characters. Ivanhoe, the discredited Saxon son, is the hero; but Rebecca, a Jewish maiden, is the noblest of all. Ivanhoe is Scott's most famous novel.

What is a sundial?

   Sundial is an instrument for measuring time by means of the motion of the sun's shadow. Before clocks and watches became common it was in general use as a timekeeper. The art of constructing sundials to suit any place and situation was an important branch of mathematical study.
   A sundial consists of two parts: the stile, or gnomon, usually the edge of a plate of metal, made parallel to the earth's axis, and pointing toward the pole; and the dial plane, on which are marked the several hours of the day, their halves, quarters, etc. Sundials receive various names, according to the positions they are constructed to occupy. When the sundial is level it is called a horizontal sundial; when perpendicular to that plane, a vertical sundial An equinoctial sundial is one whose plane is parallel to the equator. There are others. the south sundial, north sundial, east sundial, west sundial, polar sundial, and declining sundial.

The hopscotch game

Hopscotch court

   Hopscotch is an old game for children, played today in almost all countries of the world. Different forms of the game have developed in different countries. The players need good bal¬ance in order to play well.
   In the United States, children play hopscotch on a marked surface, which is a sort of court. The players mark out a diagram, usually of 10 squares, on the ground or pavement. Each player has a small piece of wood or stone called a puck. In one form of the game, each player in turn tosses his puck into the first square. Then, he hops on one foot into the first square, kicks the puck back over the base line, and hops back out of the square. Then, he tosses the puck into the second square, hops into the first square, then into the second square. There, he kicks the puck back over the base line, then hops back through the first square and out. He then tosses the puck into the third square and continues until he has moved through all the squares, or until he misses. A player misses when he loses his balance, steps on a line, or drops his puck on a line or in a wrong square. When he misses, he loses his turn and must wait until the other players have had their turns. The first player to move his puck through all the squares wins. In England, players jump on both legs, holding the puck between their feet. The hopscotch court is shaped like a snail. In other forms, a puck is not used.

Elephant ivory

Ivory bracelet

   Ivory is the smooth creamy-white material that makes up the tusks of an elephant. The tusks of other large mammals, such as the hippopotamus and the walrus, are also sometimes called ivory. Ivory is very porous, and each pore contains a waxy substance that helps produce a high polish. Since prehistoric times, ivory has been carved and modeled into decorative and useful objects. Billiard balls, piano keys, chess sets, and buttons are frequently made of ivory.
   In commerce, ivory is classified as hard or soft. Hard ivory is brittle and difficult to cut. It is obtained mostly from Asian elephants. Soft ivory, which is obtained chiefly from African elephants, is easier to cut than hard ivory. It does not readily crack, and it can withstand changes in temperature better than hard ivory can. A single elephant tusk may grow as long as 10 feet and weigh as much as 265 pounds. Such a tusk may yield a slab of ivory 2½ feet long, 6 inches wide, and ¾ inches thick.
   The material commonly called vegetable ivory is actually the hard bony seed of the ivory palm (Phytelephas macrocarpa), a tree native to South America. It is used as a substitute for true ivory in buttons, chess pieces, and other articles.

The Louvre's Golden Forgery

    For seven years a priceless gold tiara held a prominent place in the Louvre. It had been found on the site of the town of Olbia, in southern Russia, and was inscribed in Greek: "The Senate and People of Olbia to the Great Invincible Saitaphernes." The Louvre paid 200,000 francs (about $40,000) for the tiara—and it went on display on April 1, 1896. It was in a remarkable state of preservation for an object believed to be 2,200 years old. And so it should have been—it had been made only a few months earlier.
    In 1895 Schapschelle Hochmann, a Rumanian wheat dealer, commissioned a goldsmith, Israel Rouchomovsky, to make a gold tiara in antique style. Hochmann paid Rouchomovsky 2,000 rubles (about $10,000) for the work, took the tiara, and carefully battered it to simulate age.
    The tiara might still be on display had not a Montmartre painter, known as Elina, falsely claimed to have created it. A friend of Roucho¬movsky who had seen the goldsmith fashioning the tiara would not allow an unknown artist to steal the glory, so he exposed the fraud.