56 ANNUAL OF SCIENTIFIC DISCOVERY- 



tures, and particularly for all kinds of pavements, for which its 

 great hardness renders it particularly suitable. Wiien very lar.o-e 

 blocks are required, it is preferable to make them hollow, and, 

 after they have been baked or burnt, they may be filled with con- 

 crete, rubble, etc., to make them solid. Any kind of furnace in 

 whicii the requisite heat can be generated will answer for dissolv- 

 ing the granite, and baking or vitrifying the blocks or bricks. — 

 Scientific American. 



The following is the process of Mr. G. A. Frear, of Chicago : — 



** The nature of my invention consists in the use of an aqueous 

 solution of gum-sheliac, or its equivalent, in cementing together 

 particles of silex, alumina, calcium, or other mineral substances, to 

 produce, artificially, a hard and durable stone, stucco, cement, or 

 j)aint, for useful or ornamental purposes. 



" My shellac solution is best obtained by boiling the gum-shel- 

 lac of commerce in water previously made alkaline by the addition 

 of any suitable alkaline salt in proper proportion. The propor- 

 tion of shellac, alkali, and water mav, and necessarily will, vary 

 with the strength and qualit}' of the solution required in producing 

 various descriptions of stones, cements, etc. 



"In the manuficture of artificial stones for building purposes, I 

 use a solution obtained by first dissolving from 2 to 4 ounces sal- 

 eratus, potash, soda, or other equivalent alkali, in about 1 gallon 

 of pure boiling water, and then adding thereto 1 pound of gum- 

 shellac, boiling the mixture until the gum is entirely dissolved. 



'* A firm and durable stone, impervious to moisture, is produced 

 by dampening a mixture of about 1 part of lime or cement and -i 

 parts of sand or other silicious material (with or without gravel or 

 other ingredients) with my aqueous solution of shellac, and then 

 firmly compressing the composition into moulds of any desired 

 form, either by suitable machinery or by hand, with mallets or 

 tamping rods. 



"The blocks or other articles thus produced will rapidh' harden 

 "when removed from the moulds, and in a few days are ready for 

 building purposes. I prefer to obtain the compression of the ma- 

 terial by percussion rather than by simple pressure. 



" To i^roduce a more perfect finish, I contemplate washing the 

 surface or face of the artificial stone thus manufactured, 5 or 6 

 davs after moulding the same, with a weak solution of shellac dis- 

 solved in alcohol, ether, or spirits of turpentine (say about 1 pound 

 of shellac in 1 gallon of the spirits). 



"Instead of using a mixture of lime or cement and sand, to 

 produce an artificial stone, I contemplate moistening simple sand, 

 clay, lime, chalk, or other earthy or mineral substance, as well as 

 anj'' combinations thereof, with my aqueous shellac solution, and 

 the moulding the same, by percussion into suitable blocks or other 

 devices, so that an endless variety may be obtained therein at 

 pleasure. 



"To produce a mastic or stucco, I add so much of ray shellac 

 solution to lime, sand, clay, or any earthy or silicious material, 

 or to mixtures thereof, that the material or mixture shall be re- 

 duced by the solution to a pasty consistency, which can be readily 



