a sufficient supply of steam. The strong draft created by the blast 

 of the four cylinders would keep a lively fire burning. The improved 

 boiler design is described in greater detail in Improvements: 



Figure 6, Plate II, [fig. 33] represents a form of boiler which admits of any 

 desired length, whilst it gives, at the same time, an increased fire surface. 

 The general internal construction of the boiler is shown by a vertical 

 section through the fire-box. The fire-box is separated from an expanding 

 chamber by a water-bridge, which compels the flame to pass through a 

 contracted space before entering the expanding chamber, where the gas- 

 eous products of combustion are ignited previously to entering the flue- 

 tubes. By this device, coal or coke can be used without injury to the flues. 

 The water line is marked at 0,0. The flues occupy the entire circle of 

 the body of the boiler, thus giving an increase of heating surface. The 

 top of the body of the boiler is made slanting at an angle somewhat 

 greater than that of the greatest elevation to be overcome. This is done 

 for the purpose of giving free passage into the steam chamber to the 

 steam evolved at the forward end of the boiler, when ascending a gradi- 

 ent. If the body of the boiler were made cylindrical, the steam would 

 rise to the forward end, forcing the water from it into the dome, until 

 the water in the cylindrical part had come to a level with the point P, 

 at the dome end ; thus exposing the forward ends of some of the upper 

 rows of flues to injury from excessive heat. By confining the water line 

 to the diameter of the steam chamber, or dome, the variations of the 

 level of its surface, from the elevations or declivities of the road, are 

 very slight. ^^ 



The Sellers boiler, with the exception of the water leg and the 

 circulating courses, is modeled very closely on the Bury boiler. 

 Sellers had, of course, become familiar with this type of boiler 

 and its hemispherical dome when building locomotives for the 

 Philadelphia and Columbia Railroad in 1836. At that time it 

 was the most popular design among U.S. builders, but by the early 

 1850's it had gone out of favor, ironically at the very time Sellers 

 obtained his boiler patent. It is interesting to note, however, that 

 the Lima Locomotive Works revived this general scheme in the 

 iBBo's by applying it to Shay-geared locomotives. Called a "boot" 

 or "T" boiler, it was used because Shay engines operated on 

 industrial lines with steep grades, and the large dome, as Sellers 



Pp. 1 1-12. 



73 



