As in all uncultivated countries, the forests and prairies of Siberia become almost uninhabitable in summer because of the mosquitoes.
The dense population was due to the elaborate irrigation of the Babylonian plain which had originally reclaimed it from a pestiferous and uninhabitable swamp and had made it the most fertile country in the world.
On the Pacific coast there are a number of islands off the rocky shores of Lower California and in the Gulf of California - most of them barren and uninhabitable like the adjacent coast.
They are the termination of a stony plateau, containing several small oases, which southward joins the more arid and uninhabitable wastes of the Libyan Desert.
There is little of the world which is entirely uninhabited; still less permanently uninhabitable and unlikely to be required to support a population in the course of the expansion of the race beyond its present abodes.