Early Tools and Machines Already in early cultures men aimed at the expansion of their physical power in order to facilitate work processes. In prehistoric times first tools made of stone were developed and some thousand years later followed by the invention of simple mechanical devices and machines such as the wheel, the lever and the pulley. Next came the construction of powered machines. Waterwheels, windmills and simple steam-driven devices did no longer require human strength to be operated. In China for example trip-hammers powered by flowing water and waterwheels were already used some 2,000 years ago. Besides tools and machines, which helped to extend men's physical power also devices to support mental faculties, especially in the field of mathematics, were invented. As soon as 3000 BC the abacus was developed in Babylonia. By using a system of sliding beads arranged on a rack early merchants could make computations, which helped them keep track of their trading transactions. Also, early "industrial-robot devices" were developed as soon as 250 BC. The clepsydra, or water clock, which improved upon the hourglass by employing a siphon principle to automatically recycle itself, was constructed by a Greek inventor and physicist, Ctesibius of Alexandria.

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