A. Box B. Lower part of Box. C. Upper part of same. D. Clamps E. Pipes below the box. F. Column pipe fixed above the box. G. Iron axel. H. Piston- rods I. Washers to protect the bearings. K. Leathers L. Eyes in the axel. M. Rods whose ends are weighed wi

Rare woodcut from De Re Metallica printed in 1560, which was the the most famous study on all aspects of mining and metallurgy, and one of the first technological books of modern times.

The fourth kind is not a simple pump but a duplex one. It is made as follows. A rectangular block of beechwood, five feet long, two and a half feet wide, and one and a half feet thick, is cut in two and hollowed out wide and deep enough so that an iron axle with cranks can revolve in it. The axle is placed between the two halves of this box, and the first part of the axle, which is in contact with the wood, is round and the straight end forms a journal. Then the axle is bent down the depth of a foot and again bent so as to continue straight, and at this point a round piston-rod hangs from it; next it is bent up as far as it was bent down; then it continues a little way straight again, and then it is bent up a foot and again continues straight, at which point a second round piston-rod is hung from it; afterward it is bent down the same distance as it was bent up the last time; the other end of it, which also acts as a journal, is straight. This part which protrudes through the wood is protected by two iron washers in the shape of discs, to which are fastened two leather washers of the same shape and size, in order to prevent the water which is drawn into the box from gushing out. These discs are around the axle; one of them is inside the box and the other outside. Beyond this, the end of the axle is square and has two eyes, in which are fixed two iron rods, and to their ends are weighted lumps of lead, so that the axle may have a :greater propensity to revolve; this axle can easily be turned when its end has been mortised in a crank. The upper part of the box is the shallower one, and the lower part the deeper; the upper part is bored out once straight down through the middle, the diameter of the opening being the same as the outside diameter of the column pipe; the lower box has, side by side, two apertures also bored straight down; these are for two pipes, the space of whose openings therefore is twice as great as that of the upper part; this lower part of the box is placed upon the two pipes, which are fitted into it at their upper ends, and the lower ends of these pipes penetrate into trunks which stand in the sump. These trunks have perforations through which the water flows into them. The iron axle is placed in the inside of the box, then the two iron piston-rods which hang from it are let down through the two pipes to the depth of a foot. Each piston has a screw at its lower end which holds a thick iron plate, shaped like a disc and full of openings, covered with a leather, and similarly to the other pump it has a round valve in a little box. Then the upper part of the box is placed upon the lower one and properly fitted to it on every side, and where they join they are bound by wide thick iron plates, and held with small wide iron wedges, which are driven in and are fastened with clamps. The first length of column pipe is fixed into the upper part of the box, and another length of pipe extends it, and a third again extends this one, and so on, another extending on another, until the uppermost one reaches the drain of the tunnel. When the crank worker turns the axle, the pistons in turn draw the water through their discs; since this is done quickly, and since the area of openings of the two pipes over which the box is set, is twice as large as the opening of the column pipe which rises from the box, and since the pistons do not lift the water far up, the impetus of the water from the lower pipes forces it to rise and flow out of the column pipe into the drain of the tunnel. Since a wooden box frequently cracks open, it is better to make it of lead or copper or brass.

From Book VI