THE BOULEVARDS. 



135 



enougli to require some slight exertion of the operator to 

 make it level. This operation done^ a small quantity of 

 fine gravel mnst be spread over the asphalte while hot^ and 

 slightly beaten down to penetrate in it. This gives a 

 greater hardness and solidity to the footway, and insures 

 its lasting for a very long time. 



The roads before spoken of are made of the powdered 

 and not liquid asphalte. The sm-face of the roadway must 

 be beaten down very hard, and covered with a thickness of 

 about three inches of concrete, well beaten down and dry. 

 If the dryness is very necessary in the making of a pave- 

 ment, this condition is of a greater importance for the road, 

 as, if the powder were spread on a wet surface, the steam 

 caused by the heat would produce a great number of little 

 fissures, the elasticity would be destroyed, and the road 

 would be useless after a few months^ use. The concrete well 

 dried, the powder (hot) must be spread about three inches 

 thick ; and then well levelled and beaten. The sides must 

 be done first, and pressed down with a rectangular iron 

 pestle eight or nine inches in length and two or two and 

 a half inches in width. When the sides are done, proceed 

 with the middle. The pestles used in pressing it are made 

 of cast-iron, circular, and about eight inches in diameter. 

 The pestles of either form are heated and used quite hot, so 

 as to compress the asphalte into a hard smooth mass. 



When the crust of asphalte is brought to the thickness 

 required, and is sufficiently smoothed and beaten hard, they 

 spread with a sieve a little quantity of very fine powder to 

 fill all the unevenness, and again smooth the whole with a 

 flat piece of hot iron. The compression is completed by the 

 employment of two cast-iron rollers, one of 40001b. weight 

 and the other of 30001b. Sometimes three of these rollers 

 are employed, the intermediate one being about 15001b. or 

 16001b. in weight. This rolling is not always necessary, and 

 in many cases the beating down with pestles is sufficient. 

 The roads thus made, completely noiseless and lasting a long 

 time, have been adopted with the greatest success by the city 

 of Paris, and are supplanting the paving stones, macadamiz- 

 ing, and other pavements, in narrow streets where there is 



