- Arched Bridge
An innovation transforms architecture.
The exact date and location of the initial historic transition from simpler bridges to arch-supported types is now lost to us. The development and use of the arched bridge has been attributed variously to the Indus Valley Civilization of around 2500 B.C.E.; the Mesopotamians, Egyptians, Sumerians, and Chinese; and the Etruscans and Romans, who built most of the surviving early arch-based architecture in Europe.
Early arches were corbeled, not really an arch as we understand the term today. A corbel is a projecting, stone supporting piece. It is a simple example of a cantilever. Such an arch is constructed by progressively Corbeling from the two sides with horizontal Joints until they meet at a midpoint. At the top, where the two sides meet, a capstone is placed.
The Romans, aided by their invention of a cement material to bind stone together, refined the techniques of arch construction. Arch-based Roman bridges and aqueducts may be seen today throughout many cities in Europe and the Middle East.
The basic arch design proper can be likened to a beam curved to format semicircle and prevented from straightening and spreading by strong abutments at either end. Traditionally, the shape of a stone arch is made from wedge-shaped blocks, carefully cut to fit perfectly together.
Known as "voussoirs” , these blocks gradually take the curve of the arch from a central, vertical keystone down to the outermost, horizontal footers. The weight of the bridge users pushes downward onto the keystone, and it's wedge shape transfers that energy outward onto the voussoirs, thereby spreading the forces sideways and around the arch instead of straight downward. The development of the arch enabled longer and stronger bridges to be made.
SEE ALSO: FIRED BRICK, PLASTER, SUSPENSION BRIDGE, TRUSS BRIDGE, CANTILEVER BRIDGE, REINFORCED CONCRETE
- Archives Screw
The Archimedes screw was first mentioned in the writings of Athenaeus of Naucratis in 200 B.C.E. He described the use o d screw mechanism to extract bilgewater from a ship named Syracusia, and attributed its invention to Archimedes.
Archimedes (c. 287-212 B.C.E.) himself lived in Syracuse, Sicily, and was devoted to the exploration of mathematics and science. The polymath is thought to have spent time studying in Egypt, and the screw named for him is used in the Nile delta to this day, more than 2,000 years later, as a means to raise water from rivers for irrigation purposes.
The Archimedes screw consists of a helix within a hollow tube, the lower end of which is placed in a fluid. The screw is then rotated and the fluid is lifted up through the spiral chamber to the top of the tube.In ancient times this tool was applied throughout the Mediterranean for irrigation. It was especially used by the Romans in their water supply systems, and as a means of extracting water from their mines in Spain.
Technology took a backward step in the Dark Ages,but the Archimedes screw reappeared in the fourteenth century as a means of supplying public fountains with water. It was then largely superseded by reciprocating pumps, but came into its own in the 1600s for the reclamation of land from the sea, particularly in the Netherlands. Powered by windmills, they raised water from low-lying land up into canals.
The Archimedes screw is still used for drainage and flood control today, but also has many modern applications in oil pumping, sewage treatment,agriculture, and even cardiac medicine.
SEE ALSO: IRRIGATION, SEWAGE SYSTEM, SCREW, LEVER, COMPOUND PULLEY, WINDMILL