480

BOOK X.

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

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

Therefore when the master wishes to lift the dome by means of thecrane, the assistant fits over the lower small iron axle an iron crank, whichprojects from the upright beam a palm and two digits ; the end of the littleaxle is rectangular, and one and a half digits wide and one digit thick ; it isset into a similar rectangular hole in the crank, which is two digits long and alittle more than a digit wide. The crank is semi-circular, and one foot threepalms and two digits long, as many digits wide, and one digit thick. Itshandle is straight and round, and three palms long, and one and a half digitsthick. There is a hole in the end of the little axle, through which an ironpin is driven so that the crank may not come off. The crane having fourdrums, two of which are rundle-drums and two toothed-wheels, is more easilymoved than another having two drums, one of which has rundles and theother teeth.

Many, however, use only a simple contrivance, the pivots of whosecrane-post turn in the same manner, the one in an iron socket, the other in aring. There is a crane-arm on the crane-post, which is supported by anoblique 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-baris fastened firmly, the head of which is bound by a third iron ring, from whichhangs an iron hook, which engages the rings at the ends of the chains fromthe dome. At the other end of the lever-bar is another chain, which, whenit is pulled down, raises the opposite end of the bar and thus the dome; andwhen it is relaxed the dome is lowered.

38 Agricola here refers to the German word used in this connection, i.e., hundt, a dog.