The regular 17-sided polygon (heptadecagon) can be constructed with the help of a compass and a ruler.

Ditches continued to be employed as the sole defensive measure at many sites even after wall building began to emerge. For example, an immense ditch varying between 15 and 20 meters in width and marked by depths of 2.5 to 3.8 meters has recently been discovered in Hubei near Sui-chou.

The polyglacial concept (that is, the existence of many glacial periods and climate cyclicity) became accepted.

GTFI of my house.