Pytheas’s probable routes
We do not know what previous knowledge Pytheas may have had about the regions visited by him; but it is probable that he had heard of the tin country through the merchants who brought the tin overland through Gaul and down the Rhone to Massalia. In a similar way he had certainly also heard of the amber country. Besides this, he may have been acquainted with the trading voyages of the Phœnicians and Carthaginians along the west coast of Europe, and with the voyage of Himilco. Although it is true that the Phœnician sailors tried to keep the secret of their routes from their dangerous rivals the Greeks and Massalians, they cannot have been altogether successful in the long run, whether their intercourse was hostile or friendly; a few sailor prisoners would have been enough to bring the information.
The voyage northward
When Pytheas sailed out through the Pillars of Hercules he soon arrived, in passing the Sacred Promontory (Cape St. Vincent), at the limit of the world as known to the Greeks. He sailed northward along the west and north coast of Iberia (Portugal and Spain). He made observations of the tides, that remarkable phenomenon to a man from the Mediterranean, and their cause, and was the first Greek to connect them with the moon. He proceeded farther north, and found that the north-western part of Celtica (Gaul) formed a peninsula, Cabæum (Brittany), where the Ostimians lived. He supposed that it extended farther west than Cape Finisterre; but errors of that sort are easily understood at a time when no means existed of determining longitude.
Britain
Farther north he came to Brettanice (Britain), which he appears to have circumnavigated. The Sicilian historian Diodorus, an elder contemporary of Strabo, says [v. 21]: “Britain is triangular in form like Sicily; but the sides are not of equal length; the nearest promontory is Kantion [Kent], and according to what is reported it is 100 stadia distant (from the continent). The second promontory is Belerion [Cornwall], which is said to be four days’ sail from the continent. The third lies towards the sea [i.e., towards the north] and is called Orkan.[44] Of the three sides the one which runs parallel to Europe is the shortest, 7500 stadia; the second, which extends from the place of crossing [Kent] to the point [i.e., Orkan], is 15,000 stadia; but the last is 20,000 stadia, so that the circumference amounts to 42,500 stadia.”
These statements must originally have been due to Pytheas, even though Diodorus has taken them at second hand (perhaps from Timæus). But Pytheas cannot very well have acquired such an idea of the shape of the island without having sailed round it. It is true that the estimate attributed to him of the island’s circumference is more than double the reality,[45] a discrepancy which is adduced by Strabo as a proof that Pytheas was a liar;[46] but neither Strabo nor Diodorus was acquainted with his own description, and there are many indications that the exaggeration cannot be attributed to himself, but to a later writer, probably Timæus. Pytheas in his work can only have stated how many days he took to sail along the coasts, and his day’s sail in those unknown waters was certainly a short one. But the uncritical Timæus, who was moreover a historian and not a geographer, may, according to the custom of his time, have converted Pytheas’s day’s journeys into stadia at the usual equation of 1000 stadia (about 100 geographical miles) for one day’s sailing.[47] Timæus served to a great extent as the authority for later authors who have mentioned Pytheas, and it is probably through him that the erroneous information as to the circumference of Britain reached Polybius, Strabo, Diodorus, Pliny, and Solinus. In this way geographical explorers may easily have gross errors attributed to them, when their original observations are lost.
Astronomical measurements in Britain
From statements of Hipparchus, preserved by Strabo [ii. 71, 74, 75, 115, 125, 134], we may conclude that Pytheas obtained astronomical data at various spots in Britain and Orkan. Hipparchus has made use of these in his tables of climate, and he was able from them to point out that the longest day in the most northern part of Britain was of eighteen equinoctial hours,[48] and in an inhabited country, which according to Pytheas lay farther north than Britain, the longest day was of nineteen equinoctial hours. If the length of day is fixed in round numbers of hours, a longest day of eighteen hours fits the northernmost part of Scotland,[49] while the country still farther north with a longest day of nineteen hours agrees exactly with Shetland.[50] These data are important, as they show that Pytheas must have been in the most northerly parts of the British Isles, and reached Shetland.[51]
Thule