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A beam is selected, the thickness of which 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 and 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. The 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, draw perfectly straight lines 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. When these lines have been correctly drawn, a slender rope made of twisted twigs or stems is taken, smeared with pitch, and fastened at the first point of intersection. It is then carried across at an oblique angle to the succeeding intersections of longitudinal lines and circles, and as it advances, passing each of the points in due order and winding round. It is fastened at each intersection; withdrawing from the first to the eighth point, it reaches and is fastened to the line to which its first part was fastened. It makes as much progress in its longitudinal advance to the eighth point as in its oblique advance over eight points. In the same manner, bands make up the eight divisions of the diameter, fastened at an oblique angle at the intersections on the entire longitudinal and peripheral surface and make spiral channels. Other ropes are fastened on the line of the first, one atop the other and smeared with 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. These boards are soaked with pitch and bound together with strips of rope so that they will not be separated by the pressure of the water. The ends of the shaft are covered with a hardening pitch. To the right and left of the screw are beams, with crosspieces fastening them together at both ends. In these crosspieces are holes slathered with waterproof grease or animal fat and pivots placed within so that the screw may turned by being walked on. The screw should be set at angle, which should be determined by those using it as river banks and other surfaces vary as does water depth. It should also be noted that, while plausible, use of such tools is usually impractical. This type of system isn't without merit, however, and may become necessary to remove water from mines and flooded lower caverns. Sources: http://www.proequipment.com/product_brochures/b_pump_rotoscrew.htm http://www.sdrb.irisnet.be/databases/enven/sdrbe_art_index_114.htm http://www.mcs.drexel.edu/~crorres/Archimedes/Screw/conveyor/conveyor.html |