CATALOGUE OF THE MECHANICAL ENGINEERING COLLECTION. 85 



sisted in employing, in addition to the usual large driving wheels, a 

 set of small drivers operated by an additional pair of engines. By 

 this arrangement when the engine reached moderate grades the 

 steam could be shifted from the engines of the large drivers to those 

 of the small drivers. The difference in the diameter of the two sets, 

 it was believed, would enable the pistons that operate the small 

 drivers to work off all the steam generated in the boiler and to exert 

 the required force to draw the train upgrade, although with reduced 

 speed. When ascending grades of greater inclination, both sets of 

 engines and drivers could be brought into play, and thus the locomo- 



FIG. 40. — NICOLLS GRADE LOCOMOTIVE, 1848. 



tive was adapted to all circumstances and rendered effective over 

 the whole length of road without waste of power. 



Cat. No. 251,270 U.S.N.M. 



Model of Locomotive Invented by A. Cathcart in 1849. TJ. S. Patent No. 

 6818. Transferred from United States Patent Office. 



The object of this invention was to enable a locomotive to draw 

 cars up inclined planes without the use of stationary power. It con- 

 sists in attaching auxiliary cylinders to the locomotive, which act 

 upon a wheel considerably smaller than the ordinary driving wheels. 

 This wheel is toothed and is connected with an intermediate driving 

 wheel, which can be raised or lowered through a circular arc in which 

 the axis of the small wheel is the center. This latter wheel is in turn 

 lowered and gauges in a rack located between the rails. 



Cat. No. 251,272 U.S.N.M. 



