The next was the Bronze period, distinguished by the introduction and general use of a metal composed of copper and tin, requiring a comparatively low degree of temperature to smelt it, and render it capable of being fashioned into weapons, tools, and implements; to make which, however, indicated a great advance in experience, sagacity, and skill in the manipulation of metals.

With tools of bronze, to which considerable hardness could be given, trees were felled, stones hewn, houses and ships built, and agriculture practised with comparative facility.

Last of all came the Iron period, when the art of smelting and working that most difficult but widely diffused of the minerals was discovered; from which point the progress made in all the arts of life has been of the most remarkable character.
Although Mr.Wright rejects this classification as empirical, because the periods are not capable of being clearly defined, and all the three kinds of implements are found to have been in use at or about the same time,[2] there is, nevertheless, reason to believe that it is, on the whole, well founded.

It is doubtless true that implements of stone continued in use long after those of bronze and iron had been invented, arising most probably from the dearness and scarcity of articles of metal; but when the art of smelting and working in iron and steel had sufficiently advanced, the use of stone, and afterwards of bronze tools and weapons, altogether ceased.
The views of M.Worsaae, and the other Continental antiquarians who follow his classification, have indeed received remarkable confirmation of late years, by the discoveries which have been made in the beds of most of the Swiss lakes.[3] It appears that a subsidence took place in the waters of the Lake of Zurich in the year 1854, laying bare considerable portions of its bed.

The adjoining proprietors proceeded to enclose the new land, and began by erecting permanent dykes to prevent the return of the waters.