6There is a machine, on the principle of the screw, which raises water with considerable power, but not so high as the wheel. It is contrived as follows. A beam is procured whose thickness, in inches, is equal to its length in feet; this is rounded. Its ends, circular, are then divided by compasses, on their circumference, into four or eight parts, by diameters drawn thereon. These lines must be so drawn, that when the beam is placed in an horizontal direction, they may respectively and horizontally correspond with each other. The whole length of the beam must be divided into spaces equal to one eighth part of the circumference thereof. Thus the circular and longitudinal divisions will be equal, and the latter intersecting lines drawn from one end to the other, will be marked by points.
6There is also the method of the screw, which raises a great quantity of water, but does not carry it as high as does the wheel. The method of constructing it is as follows. A beam is selected, the thickness of which in digits is equivalent to its length in feet. This is made perfectly round. The ends are to be divided off on their circumference with the compass into eight parts, by quadrants and octants, and let the lines be so placed that, if the beam is laid in a horizontal position, the lines on the two ends may perfectly correspond with each other, and intervals of the size of one eighth part of the circumference of the beam may be laid off on the length of it. Then, placing the beam in a horizontal position, let perfectly straight lines be drawn from one end to the other. So the intervals will be equal in the directions both of the periphery and of the length. Where the lines are drawn along the length, the cutting circles will make intersections, and definite points at the intersections.