Five young men of the Nasamonians started from Southern Libya, W.of the Soudan, and journeyed for many days west till they came to a grove of trees, when they were seized by a number of men of very small stature, and conducted through marshes to a great city of black men of the same size, through which a large river flowed.

This Herodotus identifies with the Nile, but, from the indication of the journey given by him, it would seem more probable that it was the Niger, and that the Nasamonians had visited Timbuctoo! Owing to this statement of Herodotus, it was for long thought that the Upper Nile flowed east and west.
After Herodotus, the date of whose history may be fixed at the easily remembered number of 444 B.C., a large increase of knowledge was obtained of the western part of Asia by the two expeditions of Xenophon and of Alexander, which brought the familiar knowledge of the Greeks as far as India.

But besides these military expeditions we have still extant several log-books of mariners, which might have added considerably to Greek geography.

One of these tells the tale of an expedition of the Carthaginian admiral named Hanno, down the western coast of Africa, as far as Sierra Leone, a voyage which was not afterwards undertaken for sixteen hundred years.
Hanno brought back from this voyage hairy skins, which, he stated, belonged to men and women whom he had captured, and who were known to the natives by the name of Gorillas.

Another log-book is that of a Greek named Scylax, who gives the sailing distances between nearly all ports on the Mediterranean and Black Seas, and the number of days required to pass from one to another.