CATALOG OF THE MECHANICAL COLLECTIONS 47 



the lower part of the small cylinder is opened to the same steam, so 

 that the pressure on either side of the small piston is balanced during 

 its upward stroke. The lower end of the large cylinder is always 

 connected to the condenser and during the upstroke of the large piston 

 the pressure is balanced by opening the upper end to the condenser 

 also. The proportions of the engine are selected so that "the force 

 transmitted to the crank during the first and second halves of its 

 semirevolution shall be alike although the steam be expanded more 

 than twenty times." 



The witnesses to the patent application for the above invention were 

 Peter Hogg and James B. Ward of the old Hogg & Delameter Iron 

 Works. 



ERICSSON STEAM ENGINE, 1858 



U.S.N.M. no. 251295; original patent model; transferred from the United States 

 Patent OflJce ; not illustrated. 



This model was submitted with the application for the patent issued 

 to John Ericsson, July 6, 1858, no. 20782. 



The purpose of this design was to obtain the maximum of compact- 

 ness and power in a horizontal engine so that it could be located 

 transversely and very low within a boat for driving the screw 

 propeller of the boat. 



The engine represented consists of two short-stroke, large-diame- 

 ter, horizontal, double-acting cylinders placed with their head ends 

 bolted together and located so that the propeller shaft is in the plane 

 in which the cylinders are joined together. The piston rods of the 

 two cylinders are connected by like combinations of rocker arm and 

 connecting rod to a single crank on the propeller shaft. 



SHLARBAUM OSCILLATING ENGINE, 1863 



U.S.N.M. no. 251293 ; original patent model ; transferred from the United States 

 Patent Office; not illustrated. 



This model was submitted with the application for the patent issued 

 to Herrmann Shlarbaum, New York, N. Y., September 1, 1863, 

 Patent no. 39756. 



This engine has a reciprocating piston working in a vertical cylin- 

 der oscillating on trunnions near the center of the cylinder. The 

 piston rod is directly connected to a crankshaft supported over the 

 cylinder in the same columns that carry the cylinder trunnions. The 

 feature of this engine is the manner of admitting steam to the cyl- 

 inder and controlling the exhaust by means of sliding surfaces lo- 

 cated on the sides of the cylinder at the lower end of the cylinder. 

 Admitting steam in this manner rather than through the trunnions 

 was supposed to reduce the trouble caused by baking the lubricating 

 oil on the trunnions. 



