118 HIGHWAY CONSTRUCTION 



(3) It must not be easily abraded. 



(4) It must be of uniform quality throughout, so that it may 

 wear evenly. 



(5) It must neither scale nor flake. 



(6) Its texture must be such that dust will not adhere to it. 



(7) It must be durable. 



Materials. The materials used for footpaths are as follows: 

 Stone, natural and artificial; wood; asphalt; brick; tar concrete; and 

 gravel. 



Of the natural stones, sandstone (bluestone) and granite are ex- 

 tensively employed. 



The bluestone, when well laid, forms an excellent paving material. 

 It is of compact texture, absorbs water to a very limited extent, and 

 hence soon dries after rain ; it has sufficient hardness to resist abrasion, 

 and wears well without becoming excessively slippery. 



Granite, although exceedingly durable, wears very slippery, and 

 its surface has to be frequently roughened. 



Slabs, of whatever stone, must be of equal thickness throughout 



their entire area; the 

 edges must be dressed 

 true to the square for the 

 whole thickness (edges 

 must not be left feather- 

 ed as shown in Fig. 70) ; and the slabs must be solidly bedded on the 

 foundation and the joints filled with cement-mortar. 



Badly set or faultily dressed flagstones are very unpleasant to 

 walk over, especially in rainy weather; the unevenness causes pedes- 

 trians to stumble, and rocking stones squirt dirty water over their 

 clothes. 



Wood has been largely used in the form of planks ; it is cheap in 

 first cost, but proves very expensive from the fact that it lasts but a 

 comparatively short time and requires constant repair to keep it 

 from becoming dangerous. 



Asphalt forms an excellent footway pavement; it is durable and 

 does not wear slippery. 



Brick. Brick of suitable quality, well and carefully laid on a 

 concrete foundation, makes an excellent footway pavement for resi- 



