June 1, 1864.] THE TECHNOLOGIST. 



COMPRESSED ASPHALTE. 525 



over a period of ten years, compressed asphalte now took a place as a 

 powerful rival to ordinary stone paving and macadam. 



The asphalte employed for the works already executed in Paris is a 

 pure carbonate of lime, naturally impregnated with from six to ten per 

 cent, of bitumen. The rock is quarried in regular beds, four to seven 

 yards thick, at Seyssel (Ain), Val de Travers (canton de Neufchatel), 

 and in^several other places in the Jura. At a temperature equivalent 

 to that "of boiling water, the bitumen softens so much that the stone 

 crumbles to powder ; if now this powder, while still hot, be powerfully 

 compressed, it will form masses possessing, when cold, an amount of 

 hardness equal to that of the unquarried rock, and it is this peculiar 

 property which has been somewhat recently applied on an extended 

 scale to the formation of roadways in Paris. 



M. Malo stated that the crude asphalte is first broken by mechanical 

 means into small pieces, then reduced to powder, and subsequently 

 placed in large iron cauldrons, wherein it is heated to about 140 degrees 

 cent. While thus hot it is carried quickly, in suitable ladles, to the 

 locality where it is to be employed. The proper curved form which the 

 finished road is intended to assume has been previously imparted to a 

 bed of concrete (Beton) on which the hot asphalte, in powder be it ob- 

 served — for pressure is needed to make it agglomerate — is spread, and 

 carefully rammed, with heated cast iron rammers, into a solid sheet, so 

 to speak. Three heavy rollers are then passed successively over the 

 gradually hardening roadway. The first weighs about five hundred- 

 weight, the second one ton, and the third roller about two tons five 

 hundred-weight. By this means the stratum of asphalte is reduced to 

 a uniform thickness, fixed in Paris at four centimetres. Two or three 

 hours after the passage of the last roller the material has become so 

 far cooled and consolidated that traffic can be freely resumed on its 

 surface. 



In 1850, one year after the discovery of this process, M. Darcy, In- 

 spector-General of Eoads, proposed its application to a portion of the 

 Boulevards ; but it was not until 1854 that the first piece of compressed 

 asphalte pavement was put down in the Rue Bergere, under the super- 

 intendence of MM. Homberg, chief engineer, and Vaudry, engineer in 

 ordinary in the municipal service. In 1854, we find that about 700 or 

 800 metres only of the new roadway were in existence. In 1858 the 

 area had increased to 8,000 metres, and now it is more than 100,000 

 metres, without including many large courtyards, for which the new 

 pavement has been selected, less for the sake of solidity than for the 

 absence of noise, which follows on its use. As in all other new things, 

 M. Malo stated that many mistakes were made at first, many mishaps 

 met with, and difficulties overcome. We will mention a few of the 

 more important. 



The first essential was obviously to discover a good method of pre- 

 paring the material. After months of labour and care this object seemed 



