The duration and chronological position of this bronze-using period will have to be discussed hereafter, but I must at the outset reiterate what I said some eight or ten years ago, that in this county, at all events, it is impossible to fix any hard and fast limits for the close of the Stone Period, or for the beginning or end of the Bronze Period, or for the commencement of that of Iron. Though the succession of these three stages of civilisation may here be regarded as certain, the transition from one to the other in a country of such an extent as Britain—occupied, moreover, as it probably was, by several tribes of different descent, manners, and customs—must have required a long course of years to become general; and even in any particular district the change cannot have been sudden. There must of necessity have been a time when in each district the new phase of civilisation was being introduced, and the old conditions had not been entirely changed. So that, as I have elsewhere pointed out, the three stages of progress represented by the Stone, Bronze, and Iron Periods, like the three principal colours of the rainbow, overlap, intermingle, and shade off the one into the other, though their succession, so far as Britain and Western Europe are concerned, appears to be equally well defined with that of the prismatic colours. In thus speaking of a bronze-using period I by no means wish to exclude the possible use of copper unalloyed with tin. There is indeed every ground for believing that in some parts of the world the use of native copper must have continued for a lengthened period before it was discovered that the addition of a small proportion of tin not only rendered it more readily fusible, but added to its elasticity and hardness, and thus made it more serviceable for tools and weapons. Even after the advantages of the alloy over the purer metal were known, the local scarcity of tin may at times have caused so small a quantity of that metal to be employed, that the resulting mixture can hardly be regarded as bronze; or at times this dearth may have necessitated the use of copper alone, either native or as smelted from the ore.