830 VETEEINAEY HYGIENE 



Eoads. — The condition of roads has its hygienic aspect ; 

 a good road reduces traction, and good roads, whether in 

 town or country, are expensive to make, and need frequent 

 repair. No good road can exist unless the part be properly 

 drained, but for this purpose undue curvature should be 

 avoided, as affording no level surface to work on. 



On reference to the table (p. 775) the force of traction 

 employed on different kinds of road may be seen. 



The least destructive roads for horses are those where a 

 gradual rise and fall occurs ; roads on a dead level have 

 always been observed to wear out horses quicker than those 

 which are gently undulating, and the explanation is that 

 on the dead level there is a uniform and constant strain 

 which is relieved on the undulating road. 



Experiments have been made to determine the com- 

 parative safety of certain pavements used in cities, and the 

 following results were obtained in London : 



A horse will travel 132 miles on granite pavement without falling. 

 „ „ 191 „ asphalt „ „ 



„ „ 446 „ improved wood pavement without 



falling. 



A dry granite pavement is very slippery ; a horse will 

 only travel 78 miles on dry granite without falling as against 

 587 miles on wet. 



On the other hand, both wood and asphalt are safer in 

 the dry condition : 



On dry wood a horse will travel 646 miles without falling. 



„ damp „ „ 193 „ 



On dry asphalt a horse will travel 228 miles without falling. 



„ damp „ „ 125 



Both wet wood and asphalt are safer than ' damp,' 

 doubtless for the reason that the greasy coating gets 

 washed off. 



Wooden pavement is less slippery than either asphalt 

 or granite. 



Springs.— 'Evev J effort should be made to reduce as far 

 as possible the force of traction, and some of the methods 



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