CEMENTS. 



water, and make it into rolls. This cement is 

 useful for cementing hoops on glasses, or any other 

 mounting of electrical apparatus. 



A Cement for Glass-Grinders. 



Take pitch, and boil it ; add to it sifted-wood 

 ashes, and keep stirring it all the while, until you 

 have it of a proper temper : the addition of a 

 little tallow may be added, as you find necessary. 



Another, for small work. To four ounces of 

 resin add one-fourth of an ounce of bees-wax, and 

 four ounces of whiting, made previously red hot 

 and melt them together. The whiting should be 

 put in while hot, that it may not have time to im- 

 bibe moisture from the atmosphere. 



Shell-lac is a very strong cement for holding 

 metals, glass, or precious stones, while cutting, 

 turning, or grinding them. The metal, &c. should 

 be warmed, to melt it. For fastening ruby cylin- 

 ders in watches, and similar delicate purposes, shell- 

 lac is excellent. 



To solder or cement broken Glass. 



Broken glass may be soldered or cemented in 

 such a manner as to be as strong as ever, by inter- 

 posing between the parts, glass ground up like a 

 pigment, but of easier fusion than the pieces to be 

 joined, and then exposing them to such a heat as 

 will fuse the cementing ingredient, and make tfre 

 pieces agglutinate without being themselves fused. 



A glass for the purpose of cementing broken 

 pieces of flint glass, may be made by fusing some of 

 the same kind of glass previously reduced to 



