Figure 34. — The Original Patent Model for Sellers' 1850 

 patent, now in the collections of the U.S. National Museum. 

 The main and side rods which connected the outside cyl- 

 inders to the driving wheels were not incorporated in the 

 model because they were not considered necessary to 

 illustrate any part of the invention. (Smithsonian photo 

 46884-A.) 



It was at this point that Sellers began to write Improvements, the 

 pamphlet referred to previously. He planned to distribute it among 

 interested railway men, not only to promote the invention but also 

 to illustrate certain improvements he had made in the design since 

 the first patent. The pamphlet has 26 pages of text and 4 plates, 

 and was undoubtedly one of the most elaborate and well-written 

 prospectuses in its field prepared during that period. 



With his new design Sellers wished to silence the most common 

 criticisms of the center-rail engine, namely the use of gears and the 

 inadvisable attachment of the auxiliary cylinders to the upper part 

 of the smokebox. The weakness of this arrangement is obvious: 

 the cylmders would eventually come loose from the thin sheet-iron 



71 



