Another improvement consisted in making, at the bottom of the stone receptacle where the fuel and the ore were burnt together, a door composed of several bricks which could be readily moved. At the completion of each operation they drew out, through this door, the cake of iron, which could not be so conveniently extracted at the upper part of the furnace, on account of its height. The hammering, assisted by several heatings, finally cleared the iron, in the usual way, from all extraneous matter, consolidated it, and converted it into the state of bar-iron fit for the blacksmith's use, and for the fabrication of utensils and tools. These improved primitive furnaces are well-known to German miners under the name of _Stucköfen_ ("fragment-furnaces"). They are modified in different ways in different countries; and according to the arrangement of the furnace, and especially according to the nature of the ferruginous ores, certain methods or manipulations of the iron have been introduced, which are nowadays known under the names of the Swedish, German, Styrian, Carinthian, Corsican, and Catalan methods. The ancient furnaces for the extraction of iron may be combined under the name of _smelting-forges_ or _bloomeries_. The invention of siliceous fluxes as applied to the extraction of iron, and facilitating the production of a liquid scoria which could flow out in the form of a stream of fire, put the finishing stroke to the preparation of iron. The constructors next considerably increased the height of the stone crucible in which the fuel and the ore, now mingled with a siliceous flux, were placed, and the _blast furnace_, that is, the present system of the preparation of iron, soon came into existence. But, there may be reason to think, neither of these two kinds of furnaces belongs to the primitive ages of mankind which are the object of this work. In the iron epoch--that we are considering--the furnace without bellows was possibly the only one known; the iron was prepared in very small quantities at a time, and the meagre metallic cake, the result from each operation, had to be picked out from among the ashes drawn from the stone receptacle. Gold, as we have already said, was known to the men of the bronze epoch. Silver, on the contrary, did not come into use until the iron epoch. Another characteristic of the epoch we are now studying is the appearance of pottery made on the potter's wheel, and baked in an improved kind of furnace. Up to that time, pottery had been moulded by the hand, and merely burnt in the open air. In the iron epoch, the potter's wheel came into use, and articles of earthenware were manufactured on this wheel, and baked in an unexceptionable way in an oven especially constructed for the purpose.