‹‹‹ Vitr. 10.2.7 | Table of Contents | Vitr. 10.2.9 ›››
8There is another species of machine, ingenious in respect of its contrivance, and of ready application in practice; but it should not be used except by experienced persons. A pole or log of timber is raised, and kept in its situation by means of four guy ropes in opposite directions. Under the place where the guy ropes at top are made fast to the pole, two cheeks are fixed, above which the block is tied with ropes. Under the block, a piece of timber about two feet long, six inches wide, and four inches thick, is placed. The blocks have three ranks of pulleys latitudinally, so that it is necessary to conduct three leading ropes from the upper part of the machine; these are brought down to the lower block, and are passed through its upper pulleys from the side next the pole. They then are carried to the upper block, passing from the outer sides of the lower pulleys to the inner sides of the lower pulleys of the upper block.
8There is also another kind of machine, ingenious enough and easy to use with speed, but only experts can work with it. It consists of a single timber, which is set up and held in place by stays on four sides. Two cheeks are nailed on below the stays, a block is fastened by ropes above the cheeks, and a straight piece of wood about two feet long, six digits wide, and four digits thick, is put under the block. The blocks used have each three rows of sheaves side by side. Hence three traction ropes are fastened at the top of the machine. Then they are brought to the block at the bottom, and passed from the inside round the sheaves that are nearest the top of it. Then they are brought back to the upper block, and passed inwards from outside round the sheaves nearest the bottom.