ASPHALT, MASTIC. 37 



Artificial Marble. — Boulsson's patent is only for liardening 

 plaster casts, by immersing tliem in a solution of alum, after 

 being previously heated to about 84° for several hours. Eis- 

 ner observes, from his experiments, that previous heating is 

 ■wholly unnecessary. 



Indurated Plaster. — Objects in plaster of Paris may be 

 rendered like marble by coating them, one or more times, as 

 may be necessary, with a liquid prepared as follows : 2 pts. of 

 stearine and 2 pts. of Yenitian soap are mixed with 20 to 30 

 pts. of cold solution of caustic potassa ; and after a half-hours' 

 ebullition, 1 pt. of pearlash is added, and the heat continued 

 for a few minutes. Cold ley in sufficient quantity to produce 

 perfect fluidity is then stirred in, and the liquid set aside for 

 several days under cover. (Archiv. der Pharm. Ivi.) 



Artificial Silicious Stone. — Siemen's patent, taken out for 

 this purpose, in Bavaria, in 1845 (Kunst u. Gewerbebl. 1847), 

 makes silicious stone in the following manner : 100ft) of caus- 

 tic soda in solution is evaporated to 80 quarts, and 1ft) silica 

 added for every quart. The solution is effected under a pressure 

 of 4-5 atmospheres. This solution, mixed with quartz sand, 

 hardens to a stone which strikes fire with steel. For building- 

 stone, millstones, &c. 1 pt. of the solution is mixed with 2 

 volumes of fine silica, and to the whole are added 10-15 pts. 

 sand of different degrees of fineness, and sometimes 5-6 pts. 

 coarse sand or gravel in addition. When the stones are air- 

 dried, they are kept for several days in an apartment heated 

 to 104°. They become quite hard in 5-6 days. 



Asphalt^ Elastic. — Asphalt pavements and floors have been 

 successfully tried ; roofs of an asphalt mastic have also been 

 tried, and it is also proposed to employ it as a covering for 

 bridges, roads, &c. (Lond. Journ. xxxvi.) The materials 

 usually added to asphalt softened by heat are ground asphalt 

 rock, limestone, sand, &c. Being put on a pavement or floor, 

 in the softened state, the surface may be highly ornamented 

 by inserting pieces or pebbles of various stones of difi"erent 

 colors, producing designs in mosaic work, which, when well 

 done, are said to be very durable. The experiment of such 

 D 



