CH. X ACTION OF A HORSE IN DRAUGHT l8l 



1 That Granite was most slippery when dry, and 

 ' safest when wet ; 



' That Wood was most slippery when damp, and 

 ' safest when dry ; 



1 That when the surface of the pavements was 

 ' generally dry, Granite was the most slippery, and 

 ' Wood the least slippery ; 



' That when the surface of the pavements was 

 ' damp in different degrees, Asphalt was the most 

 ' slippery, and Wood the least slippery ; 



' That when the surface of the pavements was 

 ' wet, Asphalt was the most slippery, and Granite 

 ' the least slippery ; 



' That on the whole, Wood was less slippery than 

 'either Asphalt or Granite.' 



There is nothing so nearly perfect, from a driving 

 point of view, as a macadam surface, giving sufficient 

 smoothness without being in the least slippery ; but 

 its drawbacks of dust, mud, and rapid wear have 

 nearly banished it from large cities. 



Action of a Horse in Draught. — If a man, 

 attached to a vehicle, throws his body into the posi- 

 tion shown in Fig. yy, he would fall forward were 

 he not supported by the strain on the line by which 

 he pulls. If his inclination is slight, he will merely 

 put a portion of his weight upon the line, and the 

 remainder will be supported by the ground through 

 his legs, but if he increases his inclination suffi- 



