Through the pacific intercourse of commerce, bronze weapons and implements began to find their way, about 2000 B.C. or earlier, from Central and Southern Europe into Gaul, and thence into Britain.  In Britain the Bronze Age begins at about 1500 or 1400 B.C., and it is thought by some archaeologists that bronze was worked at this period by the aid of native tin in Britain itself.  There are indications, however, that the introduction of bronze into Britain was not by way of commerce alone.  About the beginning of the Bronze period are found evidences in this island of a race of different type from that of neolithic man, being characterised by a round skull and a powerful build, and by general indications of a martial bearing.  The remains of this race are usually found in round barrows.

This race, which certainly used bronze weapons, is generally believed to have been the first wave that reached Britain of Aryan conquerors of Celtic speech from the nearest part of the continent, where it must have arrived some time previously, probably along the Rhine valley.  As the type of Celtic speech that has penetrated farthest to the west is that known as the Goidelic or Irish, it has not unreasonably been thought that this must have been the type that arrived in Britain first.  There are indications, too, that it was this type that penetrated furthest into the west of Gaul.  Its most marked characteristic is its preservation of the pronunciation of U as ‘oo’ and of QU, while the ‘Brythonic’ or Welsh variety changed U to a sound pronounced like the French ‘u’ or the German ‘u’ and also QU to P. There is a similar line of cleavage in the Italic languages, where Latin corresponds to Goidelic, and Oscan and Umbrian to Brythonic.  Transalpine Gaul was probably invaded by Aryan-speaking Celts from more than one direction, and the infiltration and invasion of new-comers, when it had once begun, was doubtless continuous through these various channels.  There are cogent reasons for thinking that ultimately the dominant type of Celtic speech over the greater part of Gaul came to be that of the P rather than the QU type, owing to the influx from the East and Northeast of an overflow from the Rhine valley of tribes speaking that dialect; a dialect which, by force of conquest and culture, tended to spread farther and farther West.  Into Britain, too, as time went on, the P type of Celtic was carried, and has survived in Welsh and Cornish, the remnants of the tongue of ancient Britain.  We know, too, from the name Eporedia (Yvrea), that this dialect of Celtic must have spread into Cisalpine Gaul.  The latter district may have received its first Celtic invaders direct from the Danube valley, as M. Alexandre Bertrand held, but it would be rash to assume that all its invaders came from that direction.  In connection, however, with the history of Celtic religion it is not the spread of the varying types of Celtic dialect that is important, but the changes in the civilisation of Gaul and Britain, which reacted on religious ideas or which introduced new factors into the religious development of these lands.