梦溪笔谈
There were many famous inventors and early scientists in the Song Dynasty period. The statesman Shen Kuo is best known for his book known as the "Dream Pool Essays" (1088 AD). In it, he wrote of use for a drydock to repair boats, the navigational magnetic compass, and the discovery of the concept of true north (with magnetic declination towards the North Pole). Shen Kuo also devised a geological theory for land formation, or geomorphology, and theorized that there was climate change in geological regions over an enormous span of time.