‹‹‹ Vitr. 10.6.2 | Table of Contents | Vitr. 10.6.4 ›››
3To these rules or slips others are attached, also smeared with liquid pitch, and to these still others, till the thickness of the whole be equal to one eighth part of the length. On the slips or rules planks are fastened all round, saturated with pitch, and bound with iron hoops, that the water may not injure them. The ends of the shaft are also strengthened with iron nails and hoops, and have iron pivots inserted into them. On the right and left of the screw are beams, with a cross piece at top and bottom, each of which is provided with an iron gudgeon, for the pivots of the shaft to turn in, and then, by the treading of men, the screw is made to revolve.
3Other withes are fastened on the line of the first, and on these still others, all smeared with liquid pitch, and built up until the total diameter is equal to one eighth of the length. These are covered and surrounded with boards, fastened on to protect the spiral. Then these boards are soaked with pitch, and bound together with strips of iron, so that they may not be separated by the pressure of the water. The ends of the shaft are covered with iron. To the right and left of the screw are beams, with crosspieces fastening them together at both ends. In these crosspieces are holes sheathed with iron, and into them pivots are introduced, and thus the screw is turned by the treading of men.