of the Indus to the Arabian Gulf.  Later on, a Greek sailor, Hippalus, found out that by using the monsoons at the appropriate times, he could sail direct from Arabia to India without laboriously coasting along the shores of Persia and Beluchistan, and in consequence the Greeks gave his name to the monsoon.  For information about India itself, the Greeks were, for a long time, dependent upon the account of Megasthenes, an ambassador sent by Seleucus, one of Alexander’s generals, to the Indian king of the Punjab.

While knowledge was thus gained of the East, additional information was obtained about the north of Europe by the travels of one PYTHEAS, a native of Marseilles, who flourished about the time of Alexander the Great (333 B.C.), and he is especially interesting to us as having been the first civilised person who can be identified as having visited Britain.  He seems to have coasted along the Bay of Biscay, to have spent some time in England,—­which he reckoned as 40,000 stadia (4000 miles) in circumference,—­and he appears also to have coasted along Belgium and Holland, as far as the mouth of the Elbe.  Pytheas is, however, chiefly known in the history of geography as having referred to the island of Thule, which he described as the most northerly point of the inhabited earth, beyond which the sea became thickened, and of a jelly-like consistency.  He does not profess to have visited Thule, and his account probably refers to the existence of drift ice near the Shetlands.

All this new information was gathered together, and made accessible to the Greek reading world, by ERATOSTHENES, librarian of Alexandria (240-196 B.C.), who was practically the founder of scientific geography.  He was the first to attempt any accurate measurement of the size of the earth, and of its inhabited portion.  By his time the scientific men of Greece had become quite aware of the fact that the earth was a globe, though they considered that it was fixed in space at the centre of the universe.  Guesses had even been made at the size of this globe, Aristotle fixing its circumference at 400,000 stadia (or 40,000 miles), but Eratosthenes attempted a more accurate measurement.  He compared the length of the shadow thrown by the sun at Alexandria and at Syene, near the first cataract of the Nile, which he assumed to be on the same meridian of longitude, and to be at about 5000 stadia (500 miles) distance.  From the difference in the length of the shadows he deduced that this distance represented one-fiftieth of the circumference of the earth, which would accordingly be about 250,000 stadia, or 25,000 geographical miles.  As the actual circumference is 24,899 English miles, this was a very near approximation, considering the rough means Eratosthenes had at his disposal.