36o BOOK IX. 



thick, and nineteen feet and a palm long ; these are placed three feet distant 

 from one another. As the second wall is two feet higher than the first wall, 

 recesses are cut in the back of it two feet high, one foot wide, and a palm deep, 

 and in these recesses, as it were in mortises, are placed one end of each of 

 the beams. Into these ends are mortised the bottoms of just as many posts ; 

 these posts are twenty-four feet high, three palms wide and thick, and from 

 the tops of the posts the same number of rafters stretch downward to the 

 ends of the beams superimposed on the first wall ; the upper ends of the 

 rafters are mortised into the posts and the lower ends are mortised into the 

 ends of the beams laid on the first wall ; the rafters support the roof, 

 which consists of burnt tiles. Each separate rafter is propped up by a 

 separate timber, which is a cross-beam, and is joined to its post. Planks 

 close together are affixed to the posts above the furnaces ; these planks are 

 about two digits thick and a palm wide, and they, together with the wicker 

 work interposed between the timbers, are covered with lute so that there may 

 be no risk of fire to the timbers and wicker-work. In this practical manner 

 is constructed the back part of the works, which contains the bellows, their 

 frames, the mechanism for compressing the bellows, and the instrument for 

 distending them, of all of which I will speak hereafter. 



In front of the furnaces is constructed the third long waU and Hkewise 

 the fourth. Both are nine feet high, but of the same length and thickness as 

 the other two, the fourth being nine feet distant from the third ; the 

 third is twenty-one and a half feet from the second. At a distance of 

 twelve feet from the second wall, four posts seven and a half feet high, a cubit 

 wide and thick, are set upon rock laid underneath. Into the tops of the 

 posts the roof beam is mortised ; this roof beam is two feet and as many 

 palms longer than the distance between the second and the fifth transverse 

 walls, in order that its ends may rest on the transverse walls. If there should 

 not be so long a beam at hand, two are substituted for it. As the length of 

 the long beam is as above, and as the posts are equidistant, it is necessary 

 that the posts should be a distance of nine feet, one palm, two and two-fifths 

 digits from each other, and the end ones this distance from the transverse 

 walls. On this longitudinal beam and to the third and fourth walls are fixed 

 twelve secondary beams twenty-four feet long, one foot wide, three palms 

 thick, and distant from each other three feet, one palm, and two digits. In 

 these secondary beams, where they rest on the longitudinal beams, are mortised 

 the ends of the same number of rafters as there are posts which stand on the 

 second wall. The ends of the rafters do not reach to the tops of the posts, 

 but are two feet away from them, that through this opening, which is like 

 the open part of a forge, the furnaces can emit their fumes. In order that 

 the rafters should not fall down, they are supported partly by iron rods, 

 which extend from each rafter to the opposite post, and partly supported 

 by a few tie-beams, which in the same manner extend from some rafters to 

 the posts opposite, and give them stability. To these tie-beams, as weU as 

 to the rafters which face the posts, a number of boards, about two digits thick 

 and a palm wide, are fixed at a distance of a palm from each other, and are 



