HIGHWAY CONSTRUCTION 85 



displaced by the introduction of rectangular blocks of granite. Blocks 

 of comparatively large dimensions were at first employed. They were 

 from 6 to 8 inches in width on the surface, from 10 to 20 inches in 

 length, with a depth of 9 inches. They were merely placed in rows 

 on the subsoil, perfunctorily rammed, the joints filled with sand, and 

 the street thrown open to traffic. The unequal settlement of the 

 blocks, the insufficiency of the foothold, arid the difficulty of cleansing 

 the street, led to the gradual development of the latest type of stone- 

 block pavement, which consists of narrow, rectangular blocks of 

 granite, properly proportioned, laid on an unyielding and impervious 

 foundation, with the joints between the blocks filled with an imper- 

 meable cement. 



Experience has proved beyond doubt that this latter type of 

 pavement is the most enduring ar d economical for roadways subjected 

 to heavy and constant traffic. Its advantages are many, while its 

 defects are few. 



Advantages. 



(1) Adaptability to all grades. 



(2) Suits all classes of traffic. 



(3) Exceedingly durable. 



(4) Foothold, fair. 



(5) Requires but little repair. 



(6) Yields but little dust or mud. 



(7) Facility for cleansing, fair. 

 Defects. 



(1) Under certain conditions of the atmosphere, the surface of 

 the pavement becomes greasy and slippery. 



(2) The incessant din and clatter occasioned by the movement 

 of traffic is an intolerable nuisance; it is claimed by many physicians 

 that the noise injuriously affects the nerves and health of persons who 

 are obliged to live or do business in the vicinity of streets so paved. 



(3) Horses constantly employed upon it soon suffer from the 

 continual jarring produced in their legs and hoofs, and quickly wear 

 out. 



(4) The discomfort of persons riding over the pavement is very 

 great, because of the continual jolting to which they are subjected. 



(5) If stones of an unsuitable quality are used for example, 



