■ CATALOG OP THE MECHANICAL COLLECTIONS 37 



JAMES RUMSEY'S STEAM ENGINE, 1787 



"A Short Treatise on the Application of Steam , . . Applied to 



Propel Boats or Vessels . . . Grist-mills, Saw-mills, etc." 



By James Rumsey (1787) 



U.S.N.M. no. 160398 ; original ; purchased from Thomas Rumsey ; not illustrated. 



This treatise (26 pp. ) , written by the author to set forth his claims 

 as the original inventor of the steamboat, is of interest here because it 

 describes one of the earliest steam engines (or steam pumps) built in 

 the United States. 



The engine described was a direct-connected atmospheric pumping 

 engine. A vertical steam cylinder 2l^ feet in length (diameter not 

 stated) was mounted upon and directly bolted to a pump cylinder of 

 the same diameter. The pump piston and the steam piston were 

 connected together by a "smooth bolt passing through the bottom 

 of the upper cylinder." Steam from the boiler was admitted to the 

 upper cylinder "under its piston which is then carried to the top of 

 the cylinder by the steam (at the same time, the piston of the lower 

 cylinder is brought up to its top, from its connection with the upper 

 piston, by the aforesaid bolt), they then shut the communication from 

 the boiler, and open another to discharge the steam for condensation ; 

 by this means the atmosphere acts upon the piston of the upper 

 cylinder, and its force is conveyed to the piston in the lower cylinder, 

 by the aforesaid connecting bolt, which forces the water, then in the 

 lower cylinder, through the trunk, with considerable velocity; the 

 reaction of which on the other end of the trunk, is the power that 

 propels the boat forward." 



It appears from this that the engine employed the pressure of the 

 steam for raising the piston and was equipped with a separate con- 

 denser. Affidavits included in the Treatise estimate the weight of 

 the machinery as 500 to 800 pounds, occupying a space less than that 

 required for "four flour barrels" or about "four feet by three feet", 

 that the fuel consumption was not more than 4 bushels of coal in 

 12 hours, and that the boat laden with 2 to 3 tons exclusive of the 

 machinery was driven at a speed of 3 to 4 miles an hour. 



A new type of boiler, which "Charles (Morrow) conceives to be 

 the most capital contrivance to make steam that can be invented, for 

 when the machine is not at work, the whistling of the steam may be 

 heard at least half a mile", held only 20 pints of water and made 

 "more steam than a five hundred gallon boiler in the common way." 

 This was probably a boiler of the flash type. 



