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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.
Woolworth Avenue, Detroit Michigan, Laying Concrete Foundation.
The asphalt blocks are made of asphaltic cement and pulverized rock in the form of large bricks. The materials are thoroughly incorporated together and pressed out while hot in a sort of brick-machine
