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An Encyclopedia of the History of Technology part 99

An Encyclopedia of the History of Technology part 99. This one of a kind encyclopedia presents the entire field of technology from rudimentary agricultural tools to communication satellites in this first of its kind reference source. Following an introduction that discusses basic tools, devices, and mechanisms, the chapters are grouped into five parts that provide detailed information on materials, power and engineering, transportation, communication and calculation, and technology and society, revealing how different technologies have together evolved to produce enormous changes in the course of history | PART FIVE TECHNOLOGY AND SOCIETY oil-pressure systems for automobile braking and many other powertransmission applications. Another form of power-transmission which has made a contribution to public services has been compressed air. Pneumatic devices in the shape of bellows have been familiar to craftsmen from antiquity but little general use was made of them until the twentieth century when they became very valuable tools in the construction industry and in mining and in various forms of machine tool. They have also provided an essential part of the modern jet engine in aircraft and they have become familiar to motorists the world over as a means of inflating pneumatic tyres. They have been particularly valuable in deep-mining processes because they do not cause pollution of the air supply and they minimize the danger of accidents from sparking or short-circuiting. The facility for transmitting power over long distances through flexible hosing has made pneumatic power convenient for many heavy but portable tools such as the drills used in constructional work. With a compressor coupled to a small diesel engine air-powered drills have become a familiar feature of modern roadworks As with hydraulic systems the compressed medium is used to drive a piston or a ram which can then deliver a reciprocating action or which can be readily converted to rotary movement. It is less suited than hydraulic power to large-scale applications and has not been popular for municipal public services but a system of underground compressed air pipes was installed in Paris in the 1880s carrying power to pneumatic devices in various parts of the city. WASTE DISPOSAL Modern life generates many forms of waste and important public services are devoted to disposing of them. The water-borne removal of organic waste has already been considered because this is so closely related to the provision of a constant supply of fresh water. Other forms of waste removal can be more episodic. Thus industrial