The source had long been known but not exploited. Early in the eighteenth century, a pump had come into use in which expanding steam raised a piston in a cylinder, and atmospheric pressure brought it down again when the steam condensed inside the cylinder to form a vacuum. This “atmospheric engine,” invented by Thomas Savery and vastly improved by his partner, Thomas Newcomen, embodied revolutionary principles, but it was so slow and wasteful of fuel that it could not be employed outside the coal mines for which it had been designed. In the 1760s, James Watt perfected a separate condenser for the steam, so that the cylinder did not have to be cooled at every stroke; then he devised a way to make the piston turn a wheel and thus convert reciprocating (back and forth) motion into rotary motion. He thereby transformed an inefficient pump of limited use into a steam engine of a thousand uses. The final step came when steam was introduced into the cylinder to drive the piston backward as well as forward, thereby increasing the speed of the engine and cutting its fuel consumption.
资源长时间为人所知，但是还没有被开采。18世纪早期，一个活塞被使用（展开的蒸汽推动一个活塞进入圆柱体时使用），并且（当蒸汽在圆柱内浓缩，圆柱将要形成一个真空时）气压带着这个活塞下降。蒸汽机遵循革命性的理论，但是蒸汽机过于慢和浪费能源，以至于（在煤矿之外）不能工作。
reciprocating 往复的
rotary 旋转的
cylinder 圆柱
Stroke 一击
5. According to paragraph 2，the atmospheric engine was slow because
○it had been designed to be used in coal mines----错误，不是in，而是outside
○the cylinder had to cool between each stroke
○it made use of expanding steam to raise the piston in its cylinder---错误，针对wasteful of fuel
○it could be operated only when a large supply of fuel was available-----错误，针对wasteful of fuel
