De Re Metallica, Translated from the First Latin Edition of 1556

by Georg Agricola

The ashes which pass through the sieve are of the same use as they were at first, for, indeed, from these and pulverised bones they make the cupels. Finally, when much of it has accumulated, the yellow pompholyx adhering to the walls of the furnace, and likewise to those rings of the dome near the apertures, is cleared away.

Then boards are laid upon the lower small cross-beam, and at a height of two palms above these there is a small square iron axle, the sides of which are two digits wide; both ends of it are round and turn in bronze or iron bearings, one of these bearings being fastened in the crane-post, the other in the upright timber. About each end of the small axle is a wooden disc, of three palms and a digit radius and one palm thick, covered on the rim with an iron band; these two discs are distant two palms and as many digits from each other, and are joined with five rundles; these rundles are two and a half digits thick and are placed three digits apart. Thus a drum is made, which is a palm and a digit distant from the upright timber, but further from the crane-post, namely, a palm and three digits. At a height of a foot and a palm above this little axle is a second small square iron axle, the thickness of which is three digits; this one, like the first one, turns in bronze or iron bearings. Around it is a toothed wheel, composed of two discs a foot three palms in diameter, a palm and two digits thick; on the rim of this there are twenty-three teeth, a palm wide and two digits thick; they protrude a palm from the wheel and are three digits apart. And around this same axle, at a distance of two palms and as many digits toward the upright timber, is another disc of the same diameter as the wheel and a palm thick; this turns in a hollowed-out place in the upright timber. Between this disc and the disc of the toothed wheel another drum is made, having likewise five rundles. There is, in addition to this second axle, at a height of a cubit above it, a small wooden axle, the journals of which are of iron; the ends are bound round with iron rings so that the journals may remain firmly fixed, and the journals, like the little iron axles, turn in bronze or iron bearings. This third axle is at a distance of about a cubit from the upper small cross-beam; it has, near the upright timber, a toothed wheel two and a half feet in diameter, on the rim of which are twenty-seven teeth; the other part of this axle, near the crane-post, is covered with iron plates, lest it should be worn away by the chain which winds around it. The end link of the chain is fixed in an iron pin driven into the little axle; this chain passes out of the frame and turns over a little pulley set between the beams of the crane-arm.

Above the frame, at a height of a foot and a palm, is the crane-arm. This consists of two beams fifteen feet long, three palms wide, and two thick, mortised into the crane-post, and they protrude a cubit from the back of the crane-post and are fastened together. Moreover, they are fastened by means of a wooden pin which penetrates through them and the crane-post; this pin has at the one end a broad head, and at the other a hole, through which is driven an iron bolt, so that the beams may be tightly bound into the crane-post. The beams of the crane-arm are supported and stayed by means of two oblique beams, six feet and two palms long, and likewise two palms wide and thick; these are mortised into the crane-post at their lower ends, and their upper ends are mortised into the beams of the crane-arm at a point about four feet from the crane-post, and they are fastened with iron nails. At the back of the upper end of these oblique beams, toward the crane-post, is an iron staple, fastened into the lower sides of the beams of the crane-arm, in order that it may hold them fast and bind them. The outer end of each beam of the crane-arm is set in a rectangular iron plate, and between these are three rectangular iron plates, fixed in such a manner that the beams of the crane-arm can neither move away from, nor toward, each other. The upper sides of these crane-arm beams are covered with iron plates for a length of six feet, so that a trolley can move on it.

The body of the trolley is made of wood from the Ostrya or any other hard tree, and is a cubit long, a foot wide, and three palms thick; on both edges of it the lower side is cut out to a height and width of a palm, so that the remainder may move backward and forward between the two beams of the crane-arm; at the front, in the middle part, it is cut out to a width of two palms and as many digits, that a bronze pulley, around a small iron axle, may turn in it. Near the corners of the trolley are four holes, in which as many small wheels travel on the beams of the crane-arm. Since this trolley, when it travels backward and forward, gives out a sound somewhat similar to the barking of a dog, we have given it this name[38]. It is propelled forward by means of a crank, and is drawn back by means of a chain. There is an iron hook whose ring turns round an iron pin fastened to the right side of the trolley, which hook is held by a sort of clavis, which is fixed in the right beam of the crane-arm.

At the end of the crane-post is a bronze pulley, the iron axle of which is fastened in the beams of the crane-arm, and over which the chain passes as it comes from the frame, and then, penetrating through the hollow in the top of the trolley, it reaches to the little bronze pulley of the trolley, and passing over this it hangs down. A hook on its end engages a ring, in which are fixed the top links of three chains, each six feet long, which pass through the three iron rings fastened in the holes of the claves which are fixed into the middle iron band of the dome, of which I have spoken.

Therefore when the master wishes to lift the dome by means of the crane, the assistant fits over the lower small iron axle an iron crank, which projects from the upright beam a palm and two digits; the end of the little axle is rectangular, and one and a half digits wide and one digit thick; it is set into a similar rectangular hole in the crank, which is two digits long and a little more than a digit wide. The crank is semi-circular, and one foot three palms and two digits long, as many digits wide, and one digit thick. Its handle is straight and round, and three palms long, and one and a half digits thick. There is a hole in the end of the little axle, through which an iron pin is driven so that the crank may not come off. The crane having four drums, two of which are rundle-drums and two toothed-wheels, is more easily moved than another having two drums, one of which has rundles and the other teeth.

Many, however, use only a simple contrivance, the pivots of whose crane-post turn in the same manner, the one in an iron socket, the other in a ring. There is a crane-arm on the crane-post, which is supported by an oblique beam; to the head of the crane-arm a strong iron ring is fixed, which engages a second iron ring. In this iron ring a strong wooden lever-bar is fastened firmly, the head of which is bound by a third iron ring, from which hangs an iron hook, which engages the rings at the ends of the chains from the dome. At the other end of the lever-bar is another chain, which, when it is pulled down, raises the opposite end of the bar and thus the dome; and when it is relaxed the dome is lowered.