Song dynasty: printing, compass, gunpowder

The Song dynasty loses the north, but its cities, trade and crafts grow as never before. Printing from carved woodblocks makes books affordable, and the artisan Bi Sheng devises movable type of baked clay. Seafarers begin to carry a magnetised needle in a bowl of water and steer by it, not only by the stars. The mixture of saltpetre, sulphur and charcoal, found by Daoists in their search for the elixir of immortality, goes into fire arrows and the first gunpowder tubes. Paper money appears, and Kaifeng and Hangzhou become teeming cities of trade.