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THE POPULAR SCIENCE MONTHLY. 



catch rigged with a cord from the beam overhead which performed 

 the work for him. 



The hoy, thus making the operation of the valve-gear automatic, 

 increased the speed of the engine to fifteen or sixteen strokes a min- 

 ute, and gave it a regularity and 

 certainty of action that could only 

 be obtained by such an adjust- 

 ment of its valves. 



This ingenious young mechanic 

 afterward became a skillful work- 

 man, and an excellent engineer, 

 and went abroad on the Conti- 

 nent, where he erected several fine 

 engines. 



26. Potter's rude valve - gear 

 was soon improved by Henry 

 Beighton, and the new device was 

 applied to an engine which that 

 talented engineer erected at New- 

 castle-on-Tyne in 1718, in which 

 engine he substituted substantial 

 materials for Potter's unmechani- 

 cal arrangement of cords, as seen 

 in Fig. 12. 



In this sketch, r is a plug-tree, plug-rod, or plug-frame, as it is 

 variously called, suspended from the great beam with which it rises 

 and falls, bringing the pins p and k, at the proper moment, in contact 

 with the handles h k and nnof the valves, moving them in the 

 proper direction and to the proper extent. A lever safety-valve is 

 here used, at the suggestion (it is said) of Desaguliers. 



The piston was packed with leather or with rope, and lubricated 

 with tallow. 



27. Further improvements were effected in the Newcomen engine 

 by several engineers, and particularly by Smeaton, and it soon came 

 into quite extensive use in all of the mining districts of Great Britain, 

 and it also became generally known upon the Continent of Europe. 



Its greater economy of fuel as compared with the Savery engine 

 in its best form, its greater safety a consequence of the low steam- 

 pressure adopted and its greater working capacity, gave it such 

 manifest superiority that its adoption took place quite rapidly, and 

 it continued in general use in some districts where fuel was cheap 

 up to a very recent date. Some of these engines are even now in 

 existence. 



From about 1758 to the time of the introduction of the "Watt en- 

 gine, this was the machine in almost universal use for raising large 

 quantities of water. 



Fig. 13. Beighton's Valve-Gear, a. d. 1718. 



