"The furnace thus being established, the wood was withdrawn which had formed the cone, if, indeed, any had been used, and at the hole made at the base of the crucible a clod of fire-clay some inches in height was placed, so as to form a dam, and to confine in the crucible the molten or soft metal; the scoriæ, being of a lighter nature and floating at the top, made their escape over the top of the dam. As the latter were not very liquid, their issue was promoted by means of pokers or wooden poles, perhaps damped, with which also the metal was stirred in the crucible. "In neither of these two kinds of furnaces do we find any trace of bellows, and a more or less strong draught must have been procured through the opening made for the escape of the scoriæ, according to the elevation of the dome of the furnace. The limestones which have been found in certain furnaces were probably employed with a view of increasing the draught; they doubtless belonged to the upper part of the furnace, where they had been fixed so as to add height to the orifice. This rudimentary plan must have been likewise used in the earliest crucibles. The mode of obtaining a draught which we have just pointed out is indicated most plainly by the scorification of the walls of the furnace on the side opposite to the air-passage; this side has evidently experienced a more intense heat, whilst on the other the walls are much less affected by the fire, and in some cases pieces of the mineral still remain in a pasty or semi-molten state, just as they were when the work of the furnace ceased.... "The absence of any machine in the shape of bellows in the ancient metal works of the Jura appears all the more remarkable as these implements were known both to the Greeks and Romans; hence we may at least infer, not only that these nations did not introduce the art of iron-working into the Jura, but that it must have existed at a much earlier period. It must also be remarked that the openings in the furnaces are not placed in the direction of the winds prevailing in the country--a plan which might have increased the draught--but are made quite at hazard, just as the nature of the spot rendered the construction of the furnace more easy.