BOOK VI.

198

direction. The axle is square and is thirty-five feet long and two feet thickand wide. Beyond the wheel, at a distance of six feet, the axle has four hubs,one foot wide and thick, each one of which is four feet distant from the next;to these hubs are fixed by iron nails as many pieces of wood as are necessaryto cover the hubs, and, in order that the wood pieces may fit tight, they arebroader on the outside and narrower on the inside ; in this way a drum ismade, around which is wound a chain to whose ends are hooked leather bags.The reason why a drum of this kind is made, is that the axle may be kept ingood condition, because this drum when it becomes worn away by use canbe repaired easily. Further along the axle, not far from the end, is anotherdrum one foot broad, projecting two feet on all sides around the axle. Andto this, when occasion demands, a brake is applied forcibly and holds backthe machine ; this kind of brake I have explained before. Near the axle,in place of a hopper, there is a floor with a considerable slope, having infront of the shaft a width of fifteen feet and the same at the back ; at eachside of it there is a stout post carrying an iron chain which has a large hook.Five men operate this machine ; one lets down the doors which close thereservoir gates, or by drawing down the levers, opens the water-races; thisman, who is the director of this machine, stands in a hanging cage beside thereservoir. When one bag has been drawn out nearly as far as the slopingfloor, he closes the water gate in order that the wheel may be stopped ; whenthe bag has been emptied he opens the other water gate, in order that theother set of buckets may receive the water and drive the wheel in the oppositedirection. If he cannot close the water-gate quickly enough, and the watercontinues to flow, he calls out to his comrade and bids him raise the brakeupon the drum and stop the wheel. Two men alternately empty the bags,one standing on that part of the floor which is in front of the shaft,and the other on that part which is at the back. When the bag has beennearly drawn up—of which fact a certain link of the chain gives warning—theman who stands on the one part of the floor, catches a large iron hook in onelink of the chain, and pulls out all the subsequent part of the chain towardthe floor, where the bag is emptied by the other man. The object of thishook is to prevent the chain, by its own weight, from pulling down theother empty bag, and thus pulling the whole chain from its axle anddropping it down the shaft. His comrade in the work, seeing that the bagfilled with water has been nearly drawn out, calls to the director of themachine and bids him close the water of the tower so that there will be timeto empty the bag ; this being emptied, the director of the machine first ofall slightly opens the other water-gate of the tower to allow the end of thechain, together with the empty bag, to be started into the shaft again, andthen opens entirely the water-gates. When that part of the chain whichhas been pulled on to the floor has been wound up again, and has been letdown over the shaft from the drum, he takes out the large hook which wasfastened into a link of the chain. The fifth man stands in a sort of cross-cutbeside the sump, that he may not be hurt, if it should happen that a link