PREHISTORIC RELICS.--Within the last half century, in various countries of Europe, and in other countries, also, which have been, earlier or later, seats of civilization, there have been found numerous relics of uncivilized races, which, at periods far remote, must have inhabited the same ground. Many of these antiquities are met with in connection with remains of fossil elephants, hyenas, bears, etc.,--with animals which no longer live in the regions referred to, and some of which have become wholly extinct. Dwelling-places of these far-distant peoples--such as caves and rock-shelters, and the remains of the lake-habitations that were built on piles, in Switzerland and elsewhere--sepulchers, camps, and forts, and an immense number of implements and ornaments of stone and metal, have been examined. The most ancient of these monuments carry us as far back as the era called by geologists the _Quaternary_ or _Drift_ period. THE THREE STAGES.--But there are marked distinctions in the relative age of the various relics referred to. They indicate different degrees of knowledge and skill; and this proof of a succession of peoples, or of stages of development, is confirmed by geological evidence. The prehistoric time is divided into _the Stone Age_, _the Age of Bronze_, and _the Age of Iron_, according as the implements in use were of one or another of these materials. But the Stone Age includes an _earlier_ and a _later_ sub-division. In the first and most ancient section, the weapons and utensils, mostly of flint, were very rude in their manufacture. This was the _Paleolithic Age_, where there are no signs of habitations constructed by the hand, or of domesticated plants and animals. Men lived in caves, and their vestments were the skins of beasts. Yet, among their implements are found fragments of bone, horn, ivory, and stone, on which are carved in outline, often with much skill, representations of the reindeer, the bear, the ox, and of other animals. In the _Neolithic_ period, there was a decided advance. Implements are better made and polished. There were domestic animals and cultivated plants. The lake-dwellings in Switzerland were well contrived for shelter and defense. Every hut had its hearth. It is probable that most of them were furnished with a loom for weaving. Fragments of pottery are found, and flax was grown and made into cord, nettings, etc. Stalls were constructed near the huts for the ox, the goat, the horse, sheep, and pigs. The lake-dwellers cultivated wheat and barley. The _Bronze Age_, when implements were made of copper or of a mixture of copper and tin, exhibits proof of decided improvement in various directions; and the _Age of Iron_, a still more marked advance. In the Swiss remains referred to are distinct traces of a transition from the Stone Age to the Age of Bronze, and then to the Age of Iron. The kitchen-middens, or shell-mounds, of Denmark belong exclusively to the Neolithic period.