156 WIDTH OF TIRE CH. X 



the width is not important, but when only a thin 

 layer on top is hard, and the under part soft, 

 the wide tire injures the road much less than the 

 narrow one. The somewhat obsolete cobble-stone 

 pavement of eastern American cities is generally 

 laid upon an insufficient layer of gravel, on un- 

 drained soil, which, in wet weather or when the 

 frost is coming out of the ground, is soft, and the 

 stones, being round, and touching each other only 

 at points, become unstable, and the narrow tires 

 of heavily loaded carts soon displace them and ruin 

 the pavement. 



Under these circumstances, city ordinances which 

 encourage the use of wide tires are eminently 

 proper, and since it seems to be clearly shown that 

 if the width does not diminish the traction, it does 

 not increase it (provided the wheel is nearly ver- 

 tical and therefore cylindrical), wide tires cause no 

 injury to the interests of the carter. The shocks 

 and jerks felt by the horse in pulling a cart through 

 ruts and over little holes must be vastly more 

 fatiouino- to the animal than the simple traction, 

 and these shocks are much reduced by a wide tire 

 which spans many inequalities into which a narrow 

 one will drop. 



Among late experiments on ' Draught' are those 

 made by Mr H. J. Waters, of The College of 

 Agriculture and the Mechanic Arts, of Missouri, 

 reported in The Engineering Record of March 12, 

 1898. Tires of 1)4 and 6 inches in width were 



