BOOK IX.

367

Then twelve short posts are erected, whose lower ends are mortised intothe sill that is near the back of the furnace wall; these posts are two feethigh, exclusive of the tenons, and are three palms and the same number ofdigits wide, and two palms thick. A slot one and a half palms wide is cutthrough them, beginning two palms from the bottom and extending for aheight of three palms. All the posts are not placed at the same intervals, thefirst being at a distance of three feet five digits from the second, and likewisethe third from the fourth, but the second is two feet one palm and threedigits from the third ; the intervals between the other posts are arranged inthe same manner, equal and unequal, of which each four pertain to twofurnaces. The upper ends of these posts are mortised into a transversebeam which is twelve feet, two palms, and three digits long, and projectsfive digits beyond the first post and to the same distance beyond the fourth ;it is two palms and the same number of digits wide, and two palms thick.Since each separate transverse beam supports four bellows, it is necessary tohave three of them.

Behind the twelve short posts the same number of higher posts areerected, of which each has the middle part of the lower end cut out, so thatits two resulting lower ends are mortised into the back sill; these posts,exclusive of the tenons, are twelve feet and two palms high, and are five palmswide and two palms thick. They are cut out from the bottom upward, theslot being four feet and five digits high and six digits wide. The upper ends ofthese posts are mortised into a long beam imposed upon them ; this longbeam is placed close under the timbers which extend from the wall at theback of the furnace to the first long wall; the beam is three palms wideand two palms thick, and forty-three feet long. If such a long one isnot at hand, two or three may be substituted for it, which when joined togethermake up that length. These higher posts are not placed at equal distances,but the first is at a distance of two feet three palms one digit from the second,and the third is at the same distance from the fourth ; while the second is at adistance of one foot three palms and the same number of digits from thethird, and in the same manner the rest of the posts are arranged at equaland unequal intervals. Moreover, there is in every post, where it faces theshorter post, a mortise at a foot and a digit above the slot; in these mortisesof the four posts is tenoned a timber which itself has four mortises. Tenonsare enclosed in mortises in order that they may be better joined, and theyare transfixed with wooden pins. This timber is thirteen feet three palmsone digit long, and it projects beyond the first post a distance of two palmsand two digits, and to the same number of palms and digits beyond thefourth post. It is two palms and as many digits wide, and also two palms

thick. As there are twelve posts it is necessary to have three timbers of thiskind.

On each of these timbers, and on each of the cross-beams which are laidupon the shorter posts, are placed four planks, each nine feet long, two palmsthree digits wide, and two palms one digit thick. The first plank is five feetone palm one digit distant from the second, at the front as well as at the back,