article for Painting). Institutions of learning in the south were also renowned, including the Zongmingguan (Imperial Nanjing University), where the famed Zu Chongzhi (mentioned above) had studied. Zu Chongzhi devised the new Daming Calendar in 465, calculated one year as 365.24281481 days (which is very close to 365.24219878 days as we know today), and calculated the number of overlaps between sun and moon as 27.21223 (which is very close to 27.21222 as we know today). Using this number he successfully predicted 4 eclipses during a period of 23 years (from 436 to 459). Although multiple-story towers such as guard towers and residential apartments existed in previous periods, during this period the distinct Chinese pagoda tower (for storing Buddhist scriptures) evolved from the stupa, the latter originating from Buddhist traditions of protecting sutras in ancient India. Demographic changes It was during the Northern and Southern dynasties period that the earliest recorded migration of ethnic Han to southern China (below the Yangtze River) took place. This sinicisation helped to develop the region from its previous state of being inhabited by isolated communities separated by vast uncolonized wilderness and other non-Han ethnic groups. During this period, the south went from being nearly a frontier to being on a path to the thriving, urbanized, sinicized region that it became in later centuries. In his book Buddhism in Chinese History, Arthur F. Wright points out this fact by stating: "When we speak of the area of the Yangtze valley and below in the period of disunion, we must banish from our minds the picture of the densely populated, intensively cultivated South China of recent centuries. When the aristocrats of the remnants of the Chin [Jin] ruling house fled to the Nanking [Nanjing] area early in the 4th century, the south contained perhaps a tenth of the population of China. There were centers of Chinese culture and administration, but around most of these lay vast uncolonized areas into which Chinese settlers were slow to move". Maps See also Military history of the Northern and Southern dynasties Timeline of the Northern and Southern dynasties Northern and southern China Chinese sovereign List of tributaries of Imperial China Buddhism in China Empress Dowager Hu (Northern Wei) Yan Zhitui Jinping Commandery Notes References Further reading Miller, Roy Andrew (1959): Accounts of Western Nations in the History of the Northern Chou Dynasty. University of California Press. Wright, Arthur F. (1959). Buddhism