[Illustration: Places where tin is found in western Europe (marked with crosses), and routes of the tin-trade in ancient times (after L. Siret, 1908)]
It is unlikely that the Cassiterides were Cornwall, as has been commonly supposed, since this peninsula can with difficulty be regarded as a group of islands; moreover this would not agree with the descriptions which always mention them as separate from Britain, and usually farther south. The Scilly Isles, lying far out in the sea, where tin has never been worked to any great extent, and whose waters are dangerous to navigate, are out of the question. On the other hand, it may almost be regarded as certain that the Cassiterides are the same as the "Œstrymnides" (see below), and these must be looked for on the coast of Gaul. Furthermore tin is mentioned as "Celtic" by several Greek authorities; in the "Mirabiles auscultationes" of Aristotle or Pseudo-Aristotle [i. 834, A. 6] it is so called, and Ephorus (about 340 B.C.) speaks [in Scymnus of Chios] of Tartessus [i.e., Gadir], "the famous city," as "rich in alluvial tin from Celtica [Gaul], in gold, as also in copper."[25] It may further be mentioned that Mela referred to the Cassiterides[26] as "Celtican," which would mean that they belonged to the north-west coast of Spain, unless it is confused with Celtic; and in his description of the islands of Europe, going from south to north, he puts them immediately before "Sena," or the Île de Seine at the western extremity of Brittany, which means in any case that they would be to the south of that island. Everything points to the islands being situated on the south coast of Brittany, and there is much in favour of Louis Siret's assumption [1908] that they are the islands of Morbihan ("Les Îles du Morbraz"), west of the mouth of the Loire, exactly where "Penestin" is situated. This agrees very well, as we shall see later, with the description of Himilco's voyage to the Œstrymnides. The free alluvial deposits along the shore in this district, near the mouth of the Vilaine, still contain a good deal of tin, together with gold and other precious metals; but in those distant times they may have been very rich in tin, and as they lie on the very seashore they were naturally discovered early and became the most important source of tin until they were partly exhausted. In the meantime the rich tin deposits of Cornwall had begun to be utilised, and they became in turn the most important, while the Cassiterides were gradually forgotten.
