River

Pencil The pencil is a drawing instrument with a lead, usually made of graphite and clay, encapsulated in a cylinder of wood, paper or plastic. H (from hard = hard) and B (from black = black) are distinguished, and separate with a number to specify the hardness. The Italians invented the wooden one in the 18th century. From there, millions of units were manufactured in all countries of the world. Today 18 billion pencils are manufactured per year, that is, 50 million a day or 500 per second. A curiosity: If we draw a straight line with an «HB» pencil until we finish the graphite, it will have a length of 56 km.