File:Pacific service magazine (1918) (14782991452).jpg

Identifier: pacificservicema1019paci (find matches)
Title: Pacific service magazine
Year: 1912 (1910s)
Authors: Pacific Gas and Electric Company
Subjects: Pacific Gas and Electric Company Electric utilities Electrical engineering Public utilities
Publisher: San Francisco : Pacific Gas and Electric Company
Contributing Library: San Francisco Public Library
Digitizing Sponsor: San Francisco Public Library

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ryhad done, artificial means to condense thesteam. This was Newcomen, who in 1705with his assistant, Cawley, gave the steamengine the form as shown in Fig. 6. Steam was admitted from the boiler tothe cylinder, allowing the piston to beraised by heavy counterweight on theopposite side of the beam. Then thesteam valve was closed and a jet of coldwater allowed to enter the cylinder andcondense the steam. The piston was con-sequently forced down by the atmos-pheric pressure raising the pump rod onthe opposite end of the beam. The nextentry of steam expelled the condensatefrom the cylinder through an escapevalve, the piston being kept tight by alayer of water on its upper surface. Con-densation w^as at first effected by coolingthe outside of the cylinder, but the ac-cidental leakage of the packing waterpast the piston showed the advantage ofcondensing by a jet of injection waterand this plan took the place of surfacecondensation. The engine used steamwhose pressure was a little, if at all.
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Fig. 5 102 Pacific Service Magazine greater than that of the atmosphere.About 1711 Ne^vcomens engine beganto be introduced for pumping mines, andin 1713 a boy named Humphrey Potter,whose duty it was to open and close thevalves of an engine he attended, made theengine self-acting by causing the beamitself to open and close the valves bysuitable cords and catches. Potters rudedevice was simplified in 1718 by HenryBeighton, who suspended from the beama rod called the plug-tree, which workedthe valves by means of tappets. By 1725the engine was in common use in col-lieries, and it held its place without ma-terial change for about three-quarters ofa century. In 1763 James Watt, an instrumentmaker in Glasgow, while engaged by theuniversity in repairing a model of New-comens engine, was struck with the wasteof steam to which the alternate chillingand heating of the cylinder gave rise. He this in view he added to the engine a neworgan—an empty vessel separate from thecylinder into which the

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