It was not until Whetstone succeeded Z. H. Mann as chief de- 

 signer, according to Coleman Sellers, that the products of Niles 

 reflected any important improvements. i^s Sellers claimed that 

 Whetstone experimented with a plate frame but gave it up for the 

 more familiar and flexible bar frame. This so-called plate frame 

 was undoubtedly either a slab bar frame or a composite type, 

 often called a riveted frame, built up of two rails about 5 inches 

 wide and % ii^ch thick between which the pedestals were fastened. 

 There is some evidence, as will soon be pointed out, that a true 

 plate frame, so common in the British locomotive, was used. 



Although it is possible that Whetstone was inspired by the Camel 

 engines built by Winans, there is reason to believe that some true 

 slab frames were used on Niles engines. The slab frame was fabri- 

 cated in the same manner as the conventional bar frame, but a 

 single, thin, deep-throated bar was used in place of top and bottom 

 rails to connect the pedestals. However, slab frames were little 

 used in this country except by Breeze, Kneeland & Company of 

 the New York Locomotive Works, Jersey City, New Jersey. Evi- 

 dence that Niles used this type of frame is found in Coleman Sellers' 

 journal for February 4, 1854, in which he speaks of the locomotive 

 Mercury of the Springfield, Mount Vernon, and Pittsburg Railroad 

 as having a "slab rail frame." 



More evidence of Niles & Company's interest in plate frames is a 

 rough sketch (fig. 43) of a curious 4-wheel locomotive included in 

 the papers of Coleman Sellers at the American Philosophical 

 Society. The only identification other than dimensions is the word 

 "Niles" on the side of the valve chest. It is probably a study draw- 

 ing inspired by the compensating lev'er engine devised by Alba F. 

 Smith of the Cumberland Valley Railroad. A lengthy report on 

 one of these machines, built by Seth Wilmarth at his Union Works, 

 Boston, Massachusetts, for that road, appeared in the Railroad 

 Advocate on October 27, 1855. Judging from the number of com- 

 ments on Niles & Company found in its columns, it is not unlikely 

 that Sellers and Whetstone were regular readers of the Advocate 

 and were prompted by Wilmarth's report to prepare the sketch 

 shown here. Notice that the feedwater pump, attached to the 



^^* Sinclair, Development of the Locomotive Engine, p. 361. 



105 



