H2 HIGHWAY CONSTRUCTION 



(7) It suits all classes of traffic. 



(8) There is neither vibration nor concussion in traveling over it. 



(9) It is expeditiously laid, thereby causing little inconvenience 

 to traffic. 



(10) Openings to gain access to underground pipes are easily 



made. 



(11) It is durable. 



(12) It is easily repaired. 



Defects of Asphalt Pavement. These are as follows: 



(1) It is slippery under certain conditions of the atmosphere. 

 The American asphalts are much less so than the European, on account 

 of their granular texture derived from the sand. The difference is 

 very noticeable; the European are as smooth as glass, while the Ameri- 

 can resemble fine sandpaper. 



(2) It will not stand constant moisture, and will disintegrate if 

 excessively sprinkled. 



(3) Under extreme heat it is liable to become so soft that it will 

 roll or creep under traffic and present a wavy surface; and under ex- 

 treme cold there is danger that the surface will crack and become 

 friable. 



(4) It is not adapted to grades steeper than 2\ per cent, although 

 it is in use on grades up to 7.30 per cent. 



(5) Repairs must be quickly made, for the material has little 

 coherence, and if, from irregular settlement of foundation or local vio- 

 lence, a break occurs, the passing wheels rapidly shear off the sides of 

 the hole, and it soon assumes formidable dimensions. 



The strewing of sand upon asphalt renders it less slippery ; but in 

 addition to the interference of the traffic while this is being done, there 

 are further objections namely, the possible injury by the sand cutting 

 into the asphalt, the expense of labor and materials, and the mud 

 formed, which has afterwards to be removed. 



Although pure asphaltum is absolutely impervious and insoluble 

 in either fresh or salt water, yet asphalt pavements in the continued 

 presence of water are quickly disintegrated. Ordinary rain or daily 

 sprinkling does not injure them when they are allowed to become per- 

 fectly dry again. The damage is most apparent in gutters and adja- 

 cent to overflowing drinking fountains. This defect has long been 

 recognized; and various measures have been taken to overcome it, or 



