46 BULLETIN 173, U. S. NATIONAL MUSEUM 



the exhaust pipe opens. The escape pipe is also connected with the 

 condenser, which, when open, allows the steam to escape without 

 condensing. 



LIGHTHALL HALF-BEAM MARINE ENGINE, 1849 



U.S.N.M. no. 308641 ; original patent model ; transferred from the United States 

 Patent OflBce; not illustrated. 



This model was submitted with the application for the patent 

 issued to William A. Lighthall, of Albany, N. Y., October 23,' 1849, 

 no. 6811. 



The model shows a combination of a horizontal cylinder with a 

 vertical beam to which the engine's force is applied between the ful- 

 crum and the connecting rod to the engine crank. It permits locat- 

 ing the propelling machinery of a side-wheel steamboat low within 

 the hull. 



The model is a panel representing a horizontal cylinder with piston 

 rod connecting to a short beam pivoted at a point below the level of 

 the cylinder. From a short distance above the point at which the 

 piston force is applied to the beam a long connecting rod connects to 

 the crank on the engine shaft located above the cylinder and at the 

 middle of its length. The location of the condenser below the 

 cylinder and the location of the air pump and the manner of operat- 

 ing it are shown by the model. 



JOHN ERICSSON STEAM ENGINE, 1849 



U.S.N.M. no. 251299 ; original patent model ; transferred from the United States 

 Patent Office; not illustrated. 



This model formed part of the application for the patent issued 

 November 6, 1849, no. 6844. 



The invention illustrated in this model is an engine in which the 

 resistance applied to the piston rod by the load on the engine decreases 

 in the exact ratio of the decreasing pressure of the steam as it 

 expands in the cylinder of the engine. It is intended to apply the 

 irregular pressure on the piston in such a manner that a continuous 

 power will be transmitted to the crank. 



The engine consists of one small and one large diameter vertical 

 cylinder from each of which a piston rod extends upward to the end 

 of a rocking beam. The other end of each beam is connected to a 

 throw of a horizontal crankshaft, the two throws of which are 180° 

 apart. Steam is admitted to the upper end of the small cylinder, 

 when that piston is at the top of its stroke, and acts directly upon 

 the piston for part of the downstroke. The steam is then cut off and 

 expanded to the end of the stroke, when the expanded steam is passed 

 to the upper end of the large cylinder, where it expands further as 

 that piston moves down to the end of the stroke. At the same time 



