The 12th Planet Read Online Free PDF Page B

could not have come about, the Sumerians should also be credited with the invention of printing. Millennia before Johann Gutenberg "invented" printing by using movable type, Sumerian scribes used ready-made "type" of the various pictographic signs, which they used as we now use rubber stamps to impress the desired sequence of signs in the wet clay.
     
    They also invented the forerunner of our rotary presses-the cylinder seal. Made of extremely hard stone, it was a small cylinder into which the message or design had been engraved in reverse; whenever the seal was rolled on the wet clay, the imprint created a "positive" impression on the clay. The seal also enabled one to assure the authenticity of documents; a new impression could be made at once to compare it with the old impression on the document. (Fig. 12)
     
    Many Sumerian and Mesopotamian written records concerned themselves not necessarily with the divine or spiritual but with such daily tasks as recording crops, measuring fields, and calculating prices. Indeed, no high civilization would have been possible without a parallel advanced system of mathematics.
     
    The Sumerian system, called sexagesimal, combined a mundane 10 with a "celestial" 6 to obtain the base figure 60. This system is in some respects superior to our present one; in any case, it is unquestionably superior to later Greek and Roman systems. It enabled the Sumerians to divide into fractions and multiply into the millions, to calculate roots or raise numbers several powers. This was not only the first-known mathematical system but also one that gave us the "place" concept: Just as, in the decimal system, 2 can be 2 or 20 or 200, depending on the digit's place, so could a Sumerian 2 mean 2 or 120 (2 X 60), and so on, depending on the "place." (Fig. 13)
     
    The 360-degree circle, the foot and its 12 inches, and the "dozen" as a unit are but a few examples of the vestiges of Sumerian mathematics still evident in our daily life. Their concomitant achievements in astronomy, the establishment of a calendar, and similar mathematical-celestial feats will receive much closer study in coming chapters.
     
    Just as our own economic and social system—our books, court and tax records, commercial contracts, marriage certificates, and so on—depends on paper, Sumerian/Mesopotamian life depended on clay. Temples, courts, and trading houses had their scribes ready with tablets of wet clay on which to inscribe decisions, agreements, letters, or calculate prices, wages, the area of a field, or the number of bricks required in a construction.
     
    Clay was also a crucial raw material for the manufacture of utensils for daily use and containers for storage and transportation of goods. It was also used to make bricks—another Sumerian "first," which made possible the building of houses for the people, palaces for the kings, and imposing temples for the gods.
     
    The Sumerians are credited with two technological breakthroughs that made it possible to combine lightness with tensile strength for all clay products: reinforcing and firing. Modern architects have discovered that reinforced concrete, an extremely strong building material, can be created by pouring cement into molds containing iron rods; long ago, the Sumerians gave their bricks great strength by mixing the wet clay with chopped reeds or straw. They also knew that clay products could be given tensile strength and durability by firing them in a kiln. The world's first high-rise buildings and archways, as well as durable ceramic wares, were made possible by these technological breakthroughs.
     
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    The invention of the kiln—a furnace in which intense but controllable temperatures could be attained without the risk of contaminating products with dust or ashes—made possible an even greater technological advance: the Age of Metals.
     
    It has been assumed that man discovered that he could hammer "soft stones"—naturally occurring nuggets of gold as