The people in Brittany were experienced shipbuilders and mariners, who traded with Britain. Cornwall, the southwest tip of Britain, was rich in tin, an essential component of bronze, and it was there that Pytheas next headed. His report described the size and roughly triangular shape of Britain, suggesting that he must have sailed around the island.

While Pytheas’ exact route is a matter of conjecture, he may well have sailed between Britain and Ireland, landing on the Isle of Man, the latitude of which corresponds to his second measurement of the sun’s angle. The third measurement may have been taken on Lewis in the Outer Hebrides, off the west coast of Scotland. From there, he likely continued north to the Orkney Islands, north of the Scottish mainland, for his account, quoted by Pliny the Elder, reports that they were composed of 40 islands.

Presumably, Pytheas returned to Britain following much the same route by which he had left and then completed his circumnavigation of that island. Whether he further explored the northern European coast before returning to the Mediterranean, we do not know. In any case, Pliny the Elder quotes Pytheas as an authority on the amber-producing regions. Ancient sources of this precious material lay in Jutland, part of modern Denmark, and on the southern shore of the Baltic Sea. Of course, Pytheas could have learned of these areas when visiting any port in eastern Britain, and as far as we know, he made no claim to have visited them himself.