512 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



is detached from the glass, and may "be made of any desired 

 thickness by a backing of coarse cement, and strengthened by 

 the occasional interpolation of an intermediate backing of 

 fibrous material, such as canvas, etc. The surface is after- 

 ward shaped and polished, so as to bring out the marbling ; 

 and a further process of enameling on this surface is some- 

 times gone through with, so as to secure special resistance to 

 wear or exposure in the open air. This material has already 

 been applied extensively in decorative work, such as columns, 

 pilasters, cornices, statuary, etc. 3 A, Janitary 8, 1872, 485. 



BUILDING-STONE OF SLAG, COAL ASHES, ETC. 



The advantage of the manufacture of the so-called "vol- 

 canic stone" out of ashes, slag, etc., lies not only in the util- 

 ization of waste material, but in economizino; the valuable 

 land near works generally covered by these substances. 

 Althou2;h this refuse has been used as a substitute for sand in 

 mortar, a suitable cement that would withstand the weather, 

 and at the same time impart strength to these mortar masses, 

 was still needed to convert them into building-stone. By 

 the use of hydraulic lime, and other cementing materials, 

 N. Schroeder, of Kreuznach, has succeeded in forming brick 

 out of this refuse, of which large dwellings have been built, 

 arches in churches, and cellars put up (some of twenty feet 

 span), etc. ; and it is claimed by Schroeder that there is no 

 better nor cheaper material for ice-cellars, wells, etc. ; and 

 that it is especially adapted to laboratories and powder-mag- 

 azines. 8 C, January IG, 1873, 1 



IMITATION OF MARBLE. 



Imitations of marble are in great demand for ornamenta- 

 tion, and many diiferent compounds are used for the purpose. 

 Mr. Pichler, a gilder in Vienna, from his own experience, 

 recommends the following composition as being simj^le and 

 satisfactory : Into one pound of best joiners' glue, boiled 

 rather thick, half a pound of rosin (colophonium) is to be 

 slowly stirred. (Instead of the rosin, the same quantity of 

 Venetian turpentine may be used.) Into this plastic mass is 

 worked a mixture of powdered chalk of any mineral color of 

 the desired shade, and after the addition of a little olive-oil, 

 it is ready for moulding. It is sometimes convenient to have 



