There is one serious argument which has been adduced in support of the view that Britain was in Celtic occupation during the Bronze Age. The existence of the word _kassiteros_, meaning "tin," is traced in the Greek language as far back as about 900 B.C. There seems very good reason for thinking that _kassiteros_ was a Celtic word adopted into Greek. From this it is argued that the metal itself came from the Celts to the Greeks, which seems reasonable enough. It is further argued that the Celts must accordingly have been in possession of the country which produced the metal, and that this country was Britain. The conclusion is that the Celts were in occupation of Britain earlier than 900 B.C. It seems to me, however, that the fact, granting it to be a fact, that the metal tin reached the Greeks bearing a Celtic name is by no means proof that it came from a country inhabited at the time by Celts. If you visit the Zoological Gardens in the Phœnix Park, you will be invited, before you reach the entrance, to purchase for the delectation of the monkeys a certain vegetable product, the name of which, upon inquiry, you will learn to be "pea-nuts." No one will be rash enough to deny that "pea-nuts" is an English word. I have not the least idea where pea-nuts grow, but I am quite certain that the fact of their being named "pea-nuts" is no proof that they grow in England or in any English-speaking country. It is very good proof, however, if proof were needed, that the trade in pea-nuts has passed through the hands of English-speaking people. If _kassiteros_ is a Celtic word, as I think it very probably is, it proves no more than that, when the Greeks learned this Celtic name for tin, the trade in tin passed towards them through the hands of a Celtic-speaking people. If it was British tin, which again is not improbable, I suggest that it came to Greece by an overland route through the Celtic region in Mid-Europe, probably along the Rhine and the Danube or to the head of the Adriatic. As a matter of fact, the Greek writer Poseidonios states that in his time British tin reached the Mediterranean by an overland route. "It is brought," he says, "on horses through the interior of the Celtic country to the people of Massilia and to the city called Narbon." There is, then, no evidence from archæology, history, or language, sufficient to establish even a moderate degree of probability for the theory of a Celtic occupation of Ireland or Britain during the Bronze Age. On the other hand, taking Coffey's approximate date of 350 B.C. as the beginning of the period of the general use of iron in Ireland, we shall, I think, find sufficient evidence to warrant the belief that the Celts reached Britain and Ireland about that time, and not earlier, at all events not considerably earlier than that time.