By degrees the bones of wild animals become scarce, and those of ox and sheep common, showing that the pastoral stage had been reached; and the goat, pig, and horse were added to the list of domestic animals--the dog being included from the first, and the horse only at a later period. Agriculture follows next in order, and considerable proficiency was attained, barley and wheat being staple articles of food, and apples, pears, and other fruit being stored for winter consumption. Flax also was grown, and the arts of spinning and weaving were introduced, so that clothing, instead of being confined to skins, was made of coarse linen and woollen stuffs. The most important advance, however, in the arts of civilization is afforded by the introduction of metals. These begin to appear about the middle of the neolithic period, at first very sparingly, and in a few districts such as Spain, Upper Italy, and Hungary, where native copper was found and was hammered into shapes modelled on the old stone implements; but as a general rule, and in all the later settlements, bronze, in new and improved shapes, supersedes stone and copper. For the most part these bronze implements seem to have been obtained by foreign commerce from the Phoenicians, Etruscans, and other nations bordering on the Mediterranean, though in some cases they were cast on the spot from native or imported ores. The existence of bronze, however, must go back to a far greater antiquity than the time when the neolithic people of Europe obtained their first supplies from Phoenician traders. Bronze, as we have seen in a former chapter, is an alloy of two metals, copper and tin, and the hardest and most serviceable alloy is only to be obtained by mixing the two in a certain definite proportion. Now it is to be noted, that nearly all the prehistoric bronze found in Europe is an alloy in this definite proportion. Clearly all this bronze, or the art of making it, must have originated from some common centre. All this, however, is very conjectural, and all that can be concluded from it is, that any indications as to the antiquity of man derived from the bronze age as known to us in Europe, hardly carry us back to dates as remote as those furnished by the monuments of Egypt and Chaldæa. Indeed, there are no facts certainly known to us from remains of the bronze age in Europe that imply a greater antiquity than 1500 or possibly 2000 years B.C., a date at which bronze had undoubtedly been already known in Egypt and the East for many centuries.