Influence of Grade on Draft. 



429 



more objectionable becomes any grade in tlie road. This 

 is why with all railroads the heavier their freight the more 

 they overhaul their tracks and lower the grade. 



FIG. 200. Apparatus for demonstrating the Influence of different grades 

 and of obstructions on the draft of wagons on roads. 



530. Experimental Demonstration of Influence of Grade on 

 Draft. In Fig. 209 the steel bar may be set so that it 

 represents any grade from one to twenty per cent., and 

 by setting the road-bed at these different grades the spring 

 balance shows the force necessary to sustain the load in 

 the several cases. If the load with the carriage is made 

 equal to 60 Ibs. then the scales will read .6, 1.2, 1.8, 2.4, 

 etc., up to 12 Ibs. for the*20 per cent grade. If now the 



