BOOK IX.

361

covered with lute so that they do not catch fire. In the secondary beams,where they are laid on the fourth wall, are mortised the lower ends of thesame number of rafters as those in a set of rafters 5 opposite them. Fromthe third long wall these rafters are joined and tied to the ends of the oppositerafters, so that they may not slip, and besides they are strengthened withsubstructures which are made of cross and oblique timbers. The rafterssupport the roof.

The four long walls : A —First. B —Second. C —Third. D —Fourth. Theseven transverse walls : E —First. F —Second. G —Third. H —Fourth.

I—Fifth. K—Sixth. L —Seventh, or middle.

In this manner the front part of the building is made, and is divided intothree parts ; the first part is twelve feet wide and is under the hood, whichconsists of two walls, one vertical and one inclined. The second part is thesame number of feet wide and is for the reception of the ore to be smelted,the fluxes, the charcoal, and other things which are needed by the smelter.The third part is nine feet wide and contains two separate rooms of equalsize, in one of which is the assay furnace, while the other contains the metalto be melted in the cupellation furnaces. It is thus necessary that in the

5 This set of rafters appears to start from the longitudinal beam.