48o BOOK X. 



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 pahns and as many digits, that a bronze puUey, around a small iron 

 axle, may turn in it. Near the comers of the trolley are four holes, in which 

 as many small wheels travel on the beams of the crane-arm. Since this 

 troUey, when it travels backward and forward, gives out a sound somewhat 

 similar to the barking of a dog, we have given it this name^^. 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 puUey, 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 puUey 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 

 Uttle more than a digit wide. The crank is semi-circular, and one foot three 

 pahns 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 httle 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 

 obhque 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 puUed down, raises the opposite end of the bar and thus the dome; and 

 when it is relaxed the dome is lowered. 



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



