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POPULAR SCIENCE MONTHLY 



are laid the dry surface of concrete is swept clean and strewn with dry, 

 clean sand, upon which the bricks are laid and pounded to the proper 

 contour. The joints are filled either with sand or bituminous grout. 

 In the latter case the pavement is impervious to water and the surface 

 makes a very clean and excellent street. 



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The asphalt blocks are made of asphaltic cement and pulverized 

 rock in the form of large bricks. The materials are thoroughly incor- 

 porated together and pressed out while hot in a sort of brick-machine 



