Beyond these regions he could only depend upon the rough indications and guesses of untutored merchants.

But it is worth while referring to his method of determining latitude, as it was followed up by most succeeding geographers.

Between the equator and the most northerly point known to him, he divides up the earth into horizontal strips, called by him "climates," and determined by the average length of the longest day in each.

This is a very rough method of determining latitude, but it was probably, in most cases, all that Ptolemy had to depend upon, since the measurement of angles would be a rare accomplishment even in modern times, and would only exist among a few mathematicians and astronomers in Ptolemy's days.

With him the history of geographical knowledge and discovery in the ancient world closes.
In this chapter I have roughly given the names and exploits of the Greek men of science, who summed up in a series of systematic records the knowledge obtained by merchants, by soldiers, and by travellers of the extent of the world known to the ancients.