104 T^he Public Gardens and Parks of Paris. 



and very hard ; put on the top about one or two inches of beton 

 (mortar composed of quickUme, sand, and gravel mixed together), 

 and cover the whole half an inch thick with mortar. If the surface 

 be not a solid one, the thickness of the heton should be three or 

 four inches. The surface must be very dry, or the success of the 

 operation may not be perfect. 



During the last few years the preparation of the asphalte has 

 been much improved. Some years ago, when a pavement was 

 to be made with asphalte, a great nuisance was experienced by 

 the public during the operation. The matter was liquefied on the 

 spot, and produced a nasty smell and smoke, disagreeable and in- 

 jurious ; but now some of these inconveniences have been done 

 away with by a new system, and asphalte is now laid down in the 

 most expeditious manner. It is prepared first in out-of-the-way 

 places devoted to the purpose, and the matter, ready for use and 

 liquefied, may be transported from these places to any parts of 

 the town without the least inconvenience in a semi-cylindrical 

 boiler, closed by iron doors, and moved about on iron wheels as 

 freely as a common cart. Under the boiler is a fireplace, and the 

 blaze, after having heated the two sides of the boiler, passes out by 

 a chimney placed at the back of the machine. Means to keep the 

 matter in motion, and prevent its burning by adhering to the sides 

 of the boiler, are secured by a simple mechanism easily worked with 

 the hand. These carriage boilers, full of liquid asphalte, are driven 

 from place to place with the greatest facility. The boiler is emptied 

 by the means of a pipe fixed to its bottom, and the matter is col- 

 lected in a pail, and spread on the surface to the thickness of three- 

 quarters of an inch. If the surface is not perfectly dry, the drying 

 must be accelerated with hot ashes, which are to be taken away 

 afterwards, or with a little spreading of quicklime in powder. These 

 operations are indispensable, as if the asphalte were laid on before 

 the surface is dry, the heat of the asphalte would dispel in steam 

 the water underneath, and that steam would produce blisters in the 

 asphalte, which would crack under the pressure of the feet, and 

 endanger the success of the operation. The operators place on the 



