Polytechnic Association. 817 



February 23, 1872. 



Prof. S. D. Tillman in the chair ; Robert Weir, Esq., Secretary. 



High Pressure Steam Engines. 

 The Chairman — Before taking up the paper advertised for this 

 evening, a word or two upon the steam-engine may not be out of 

 place. I think it was to Emerson an Englishman said, some years 

 ago, while advocating an international copyright law: "If you do 

 not give us a copyright on our works, we shall, at any rate, educate 

 your children." They have done it, on one subject at least, for their 

 histories of great inventions and discoveries have been widely circu- 

 lated in this country. English books are filed with statements which 

 we know are not altogether true with regard to the origin and improve- 

 ment of the steam-engine. The high pressure steam-engine, which 

 is moved by heat alone, is an American invention. The low pressure 

 or condensing engine is a European invention. It originated with 

 Dr. Denis Papin, a French physician, in the year 1690. He used the 

 pressure of the atmosphere to move the piston of a cylinder, within 

 which was a vacuum resulting from the condensation of steam on the 

 application of cold water to the outside of the cylinder. When the 

 steam condensed, the pressure of the atmosphere brought down the 

 piston. That was the first step in the invention of the condensing 

 steam-engine. Other improvements of Papin were embraced in the 

 first steam and atmospheric pumping engine, made by Newcomen 

 and Savery, which was used in draining mines more than fifty years 

 before Watt's invention. His improvement consisted in keeping the 

 steam cylinder hot, by condensing the steam in another vessel. The 

 rose jet, by which was forced in fine streams into the cylinder, for 

 the purpose of condensing the steam, had been invented long before ; 

 so that the second cylinder introduced by Watt contained only the 

 jet and piston, which were old devices. The steam cylinder was 

 thus no longer exposed to the cooling effects of the condensing water. 

 This was, of course, a great advance. Up to this time, 1770, and 

 through nearly the whole of Watt's career, the steam engine had 

 only been used for pumping water. The greatest improvement of 

 the steam-engine in England was the invention of a boy named Hum- 

 phrey Potter, who in 1715 made the machine self-acting. He was 

 employed to move the valves by hand ; finding that this was done 

 when the walking beam reached its highest and lowest points, he 

 [Inst.] 52 



