110 BULLETIN 173, U. S. NATIONAL MUSEUM 



"When used the tubes and header were contained in a sheet-iron 

 shell that supported the grates and formed the ashpit, the furnace, 

 and the stack. The shell is not with the specimen. 



The safety valve used with the boiler is exhibited separately in 

 the Museum and is described below under "Steam-boiler Accessories.'* 

 It bears the same U.S.N.M. number. 



CRAWFORD BOILER FURNACE, 1850 



U.S.N.M. no. 309208; original patent model; transferred from the United States 

 Patent Office ; not illustrated. 



This model formed part of the application for the patent issued to 

 Benjamin Crawford, of Allegheny, Pa., January 29, 1850, no. 7051 ; 

 reissued December 2, 1862, no. 135. 



The model represents a wide, internally fired, return tubular boiler 

 (western river type) equipped with an air heater using the hot flue 

 gases and exhaust steam from the engine, a forced draft produced by 

 steam jets in the ash-pit, rotary steam jets for increasing turbulence 

 above the fire, and induced draft produced by rotary steam jets in 

 the stacks. 



Air for combustion is drawn through tubes in a cylindrical shell 

 into which the exhaust from the engine opens. After passing through 

 this heater the air travels through ducts that are let into the breech- 

 ing and is further heated by the hot flue gases. Steam jets dis- 

 charged through the air pipes toward the ashpit induce the flow of 

 air to the ashpit. The steam jets, which produce turbulence over 

 the fire and induce draft in the stacks, issue from nozzles formed of 

 short pipe one end of which is straight and fits over the end of the 

 steam pipe, the other end twisted so that the steam is discharged at an 

 angle to the axis of the pipe, the reaction causing the nozzle to 

 whirl. 



WIEGAND STEAM BOILER, 1867 



U.S.N.M. no. 309209 : original patent model ; transferred from the United States 

 Patent Office; not illustrated. 



This model was submitted with application for the patent issued 

 to S. Lloyd Wiegand, of Philadelphia, Pa,, August 6, 1867, no. 

 67621. 



This model is of a boiler having water tubes made up of large 

 tubes closed at the ends with smaller tubes suspended within the 

 large tubes to provide circulation of steam and water upward in 

 the smaller tubes and of the cooler water downward in the annular 

 spaces between the larger and smaller tubes. The inventor suggests 

 the use of tubes of different metals to produce a galvanic action 

 for the purpose of j^reventing deposits of scale within the tubes. 



