Prehistoric archaeology affords abundant proofs that, in countries of Celtic speech, metal-working in bronze, iron, and gold reached a remarkably high pitch of perfection, and this is a clear indication that Celtic countries and districts which were on the line of trade routes, like the Rhone valley, had attained to a material civilisation of no mean character before the Roman conquest.

In Britain, too, the districts that were in touch with continental commerce had, as Caesar tells us, also developed in the same direction.

The religious counterpart of this development in civilisation is the growth in many parts of Gaul, as attested by Caesar and by many inscriptions and place-names, of the worship of gods identified with Mercury and Minerva, the deities of civilisation and commerce.

It is no accident that one of the districts most conspicuous for this worship was the territory of the Allobrogic confederation, where the commerce of the Rhone valley found its most remarkable development.

From this sketch of Celtic civilisation it will readily be seen how here as elsewhere the religious development of the Celts stood closely related to the development of their civilisation generally.