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SOLUTIONS

1000 – 1499-BLAST FURNACE - 1300s. "It was not possible to make molten iron, which could be cast, until after the introduction of the blast furnace in the 1300s."
BUOY - 1000s. "The first recorded evidence of the use of buoys dates from about the 11th century, when European trade (as opposed to local trade) began to expand, mainly under the dominance of the Hanseatic League which took a keen and vigilant attitude in matters affecting the safety of ships. As early as 1066 buoys guided ships through the channels of the River Weser..."

HANDGUN - around 1128. "The gun did not appear until the twelfth century A.D. For this three things were needed: a metal barrel, gunpowder with a high nitrate content, and a projectile that neatly filled the barrel so that the powder charge could exert its full propellant effect. Until very recently it was believed that the first Chinese gun ... dated to A.D. 1290. Continuing exploration of the Buddhist caves of western China has now revealed a remarkable temple at Ta-tsu in Szechuan Province, containing evidence that revolutionizes the history of the gun. Among the many reliefs in the cave are two showing gunpowder weapons. One depicts a small demon with two horns cradling a handgun while a second devil holds a grenade. The date of this extraordinary find, according to the inscriptions in the caves, is A.D. 1128." [James, Peter and Nick Thorpe. Ancient Inventions, 1994.MOVABLE TYPE - around 1045. "This seminal invention is specifically attributed to an experienced Chinese block printer named Bi Sheng. According to contemporary accounts, about 1045 he conceived the idea of making each character in clay, which was then fired to make it hard."

SPECTACLES - around 1280. "Lenses placed close to the eyes were first certainly used towards the end of the 13th century. Nothing is known of the inventor, or of the date or place of the discovery, as it was the work of an illiterate artisan, but Edwarard Rosen fixes the period of the discovery to the five years after 1280. The inventor was probably a glazier, who made ornaments and glass discs for windows." STAINED GLASS - 1100s. "Colored glass, soon to become the glory of the great Gothic cathedrals, was not used in Europe until the 12th century."

1500 – 1699:BAROMETER - 1643. "For reasons not then understood by mining engineers, suction pumps could not raise water above a height of 9 meters (30 feet). In 1643, Galileo's assistant Torricelli discovered why this should be: the pressure of the atmosphere is equal to that of a column of water of that height and that is the limit of water it can support. Using mercury, a liquid 13 1/2 times denser than water, Torricelli noted that a column 76 centimeters (roughly 30 inches) high could be supported. He predicted, and subsequent experiments proved, that with increasing altitude the atmospheric pressure would diminish and the length of the column would be correspondingly shorter; thus was born the barometer."MICROSCOPE - around 1590. "The microscope was invented ... in about 1590, by Zacharias Jansen, a spectacle-maker. It was a relatively crude device, using ... a concave and a convex lens, and there is no evidence that Jansen made any significant observations with it.