History of chemistry
An important breakthrough in making sense of the list of known chemical elements (as well as in understanding the internal structure of atoms) was Dmitri Mendeleev's development of the first modern periodic table, or the periodic classification of the elements. Mendeleev, a Russian chemist, felt that there was some type of order to the elements and he spent more than thirteen years of his life collecting data and assembling the concept, initially with the idea of resolving some of the disorder in the field for his students. Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. Mendeleev's law allowed him to build up a systematic periodic table of all the 66 elements then known based on atomic mass, which he published in "Principles of Chemistry" in 1869. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties.
Tabula (game)
According to the "Etymologiae" by Isidore of Seville, tabula was first invented by a Greek soldier of the Trojan War named Alea. The earliest description of "τάβλι" (tavli) is in an epigram of Byzantine emperor Zeno (r. 474–475; 476–491), given by Agathias of Myrine (6th century AD), who describes a game in which Zeno goes from a strong position to a very weak one after an unfortunate dice roll. The rules of Tabula were reconstructed in the 19th century by Becq de Fouquières based upon this epigram. The game was played on a board nearly identical to a modern backgammon board with 24 points, 12 on each side. Two players had 15 pieces each, and moved them in opposing directions around the board, according to the roll of three dice. A piece resting alone in a space on the board was vulnerable to being hit. Hitting a blot, reentering a piece from the bar, and bearing off, all had the same rules as today. The only differences with modern backgammon were the use of an extra die (three rather than two) and the starting of all pieces off the board (with them entering in the same way that pieces on the bar enter in modern backgammon).