Redirected from Pytheas of Massilia
The start of Pytheas's voyage is already a mystery. In those days, the Carthaginians had closed the Straits of Gibraltar for all ships from other nations. Some historians therefore believe that he travelled overland to the mouth of the Loire or the Garonne. Others believe that to avoid the Carthaginian blockade, he may have stuck close to land and sailed only at night. In northern Spain, he studied the tides, and may have discovered that they are caused by the Moon. His discovery was known to Posidonius.
Pytheas travelled to Cornwall, important because it was the main source of tin, and studied the production and processing of tin. He circumnavigated Britain, and found that tides could be very high there.
Pytheas heard of an island six days sailing to the north of Britain, called Thule, and visited it. We do not know where Thule was, but probably it was (part of) the Norwegian coast, although Iceland, the Shetland Islands and Faeroe Islands have also been identified as such by historians. Pytheas says that Thule was an agricultural country, and that it produced honey. He said he was shown the place where the sun went to sleep, and he noted that the night in Thule was only two to three hours.
According to Pytheas, he inhabitants of Thule ate fruits and drank milk, and they made a drink out of grain and honey. Unlike the people from southern Europe, they had barns, and threshed their grain there rather than outside.
One day further north the congealed sea began, he claimed. As Strabo says (as quoted in Chevallier 1984):
The term used for "marine lung" actually means jellyfish, and modern scientists believe that Pytheas here tried to describe the formation of pancake ice[?] at the edge of the drift ice[?], where sea, slush, and ice mix, surrounded by fog.
After completing his survey of Britain, Pytheas travelled to the Shallows on the continental North Sea coast. He may also have visited the Baltic Sea, but he did visit an island which was a source of amber, probably Helgoland.
Nothing is known about his return voyage. He may have returned whichever way he came, but also by land, along the Rhine and Rhône rivers. He wrote a report on his voyage, but that has not been left for modern historians. We have to do with the remarks of others. Among them Strabo, who (unjustly) called Pytheas a liar. Pytheas also determined the exact location of the North Pole in the sky.
Originally copied from  (http://www.win.tue.nl/~engels/discovery/pytheas) (with permission)