BOOK X.

477

that the one fits in a mortise in the middle of the other, and the other likewisefits in the mortise of the first, thus making a kind of a cross ; these sills arethree feet long and one foot wide and thick. The crane-post is round at itsupper end and is cut down to a depth of three palms, and turns in a bandfastened at each end to a roof-beam, from which springs the inclined chimneywall. To the crane-post is affixed a frame, which is made in this way : first, at aheight of a cubit from the bottom, is mortised into the crane-post a smallcross-beam, a cubit and three digits long, except its tenons, and two palms inwidth and thickness. Then again, at a height of five feet above it, is anothersmall cross-beam of equal length, width, and thickness, mortised into thecrane-post. The other ends of these two small cross-beams are mortisedinto an upright timber, six feet three palms long, and three-quarters wideand thick ; the mortise is transfixed by wooden pegs. Above, at a height ofthree palms from the lower small cross-beam, are two bars, one foot one palmlong, not including the tenons, a palm three digits wide, and a palm thick,which are mortised in the other sides of the crane-post. In the same manner,under the upper small cross-beam are two bars of the same size. Also in theupright timber there are mortised the same number of bars, of the same lengthas the preceding, but three digits thick, a palm two digits wide, the twolower ones being above the lower small cross-beam. From the uprighttimber near the upper small cross-beam, which at its other end is mortisedinto the crane-post, are two mortised bars. On the outside of this frame,boards are fixed to the small cross-beams, but the front and back parts of theframe have doors, whose hinges are fastened to the boards which are fixedto the bars that are mortised to the sides of the crane-post.

Then boards are laid upon the lower small cross-beam, and at a heightof two palms above these there is a small square iron axle, the sides of whichare two digits wide ; both ends of it are round and turn in bronze or ironbearings, one of these bearings being fastened in the crane-post, the other inthe upright timber. About each end of the small axle is a wooden disc, of threepalms and a digit radius and one palm thick, covered on the rim with an ironband; these two discs are distant two palms and as many digits from each

“ and lead. It is considered better in quality the nearer it approaches to a golden colour‘ and the less lead there is in it; it is also friable and moderately heavy. When it is boiled“ with oil it becomes liver-coloured, adheres to the gold and silver furnaces, and in this state' h is called metallica." From these two passages it would seem that molybdaena, a varietyof litharge, might quite well be hearth-lead. Further (in xxxiv, 47), he says: “ The metalwhich flows liquid at the first melting in the furnace is called stannum, at the second melt-ing is silver, that which remains in the furnace is galena.” If we still maintain that molybdaenais hearth-lead, and galena is its equivalent, then this passage becomes clear enough, thesecond melting being cupellation. The difficulty with Pliny, however, arises from thepassage (xxxm, 31), where, speaking of silver ore, he says: “ It is impossible to melt itexcept with lead ore, called galena, which is generally found next to silver veins.”Agricola ( Bermannus, p. 427, &c.), devotes a great deal of inconclusive discussion to anattempt to reconcile this conflict of Pliny, and also that of Dioscorides. The probableexplanation of this conflict arises in the resemblance of cupellation furnace bottoms to leadcarbonates, and the native molybdaena of Dioscorides; and some of those referred to by Plinymay be this sort of lead ores. In fact, in one or two places in Book IX, Agricola appearso use the term in this sense himself. After Agricola’s time the term molybdaenum was appliedo substances resembling lead, such as graphite, and what we now know as molybdenite (Mo S2).borne time in the latter part of the 18th century, an element being separated from the latter, itwas dubbed molybdenum, and confusion was five times confounded.

33