153 



ON DRAUGHT. 



tion of 

 will be 



railway ; and fig. 41 represents an end 

 view of the rail with a pair of wheels. The 

 ground is afterwards filled up nearly to 

 the level of the bars, leaving only about 

 one inch of their upper edge exposed : 

 upon this the wheels run. The wheels are 

 generally of cast iron, about three feet in 

 diameter, and slightly conical, with an edge 

 or flange inside to guide them in the centre 

 of the rails. This brief description is suffi- 

 cient to give a general idea of the construc- 

 railways, which is all that is necessary for our present purpose. It 

 easily conceived that hard, cast-iron wheels, running upon smooth 



JE^.41 



K 



edges of iron in this manner, can meet with but little resistance, except 

 those arising from friction at the axle. Accordingly, we find, upon a well- 

 constructed railway, in good order, that the resistance does not exceed, in 

 any sensible degree, that which must arise from this cause. It has been 

 found that a force of traction of 1 lb. will put in motion a weight of 180, 

 200, and even, in some cases, 250 lbs. : so that a horse exerting an effort of 

 only 12.5 lbs., would drag on a level 10 tons. This is about ten times 

 the average effect of his work upon a good common road, and, as it arises 

 entirely from the hardness and smoothness of the road, we cannot conclude 

 our observations by a more striking and unanswerable argument than this, 

 in proof of the immense advantages and saving of expense which would 

 result from greater attention to the state of the roads. 



