MECHANICS AND USEFUL ARTS. 133 



rail or ship, and be stored with perfect safety, and that it may 

 be "recovered" in small quantities on the very spot where it is 

 required for use, so as to avoid, in a great measure, the peril to 

 miners or others who have to handle it in their operations. 



Painting Zinc. — A difficulty is often experienced in causing oil 

 colors to adhere to sheet zinc. Boettger recommends the employ- 

 ment of a mordant, so to speak, of the following composition : 

 One part of chloride of copper, one of nitrate of copper, and one 

 of sal-ammoniac, are to be dissolved in G^t parts of water, to which 

 solution is to be added one part of commercial hydrochloric acid. 

 The sheets of zinc are to be brushed over with this liquid, which 

 gives them a deep black color; in the course of from 12 to 24 

 hours they become dry, and to their now dirty gray, surface a coat 

 of any oil color will firmly adhere. Some sheets of zinc prepared 

 in this way, and afterwards painted, have been found to entirely 

 withstand all the atmospheric changes of winter and summer. 



Very Durable Cement for Iron and Stone. — M. Pollack, of Baut- 

 zen, Saxony, states that, for a period of several years, he has 

 used, as a cement to fasten stone to stone, and iron to iron, a paste 

 made of pure oxide of lead, litharge, and glycerine in concen- 

 trated state. This mixture hardens rapidly, is insoluble in acids 

 (unless quite concentrated), and is not affected by heat. M. Pol- 

 lack has used it to fasten different portions of a fly-wheel with 

 great success ; while, when placed between stones, and once 

 hardened, it is easier to break the stone than the joint. 



'* Dingler's Journal " recommends as a lute for covering the 

 corks of vessels containing benzine or any of the light hydrocar- 

 bons or essential oils, a paste made of finely-ground litharge and 

 concentrated glycerine. The mixture is spread over the corks or 

 bungs, and soon hardens. It is insoluble in the said liquids, is 

 not acted upon by them, and is quite inexpensive, as the com- 

 monest kind of glycerine can be used. 



A writer in " Comptes Rendus " says that if articles made of 

 copper be immersed in molten sulphur having lamp-black in sus- 

 pension, they assume the appearance of bronze, and can be pol- 

 ished without losing that aspect. 



Treating Textile Fabrics. — M. Pierre Armand N"euman, of St. 

 Denis, Paris, treats textile fabrics with sulphuric acid, for the 

 purpose of rendering them impermeable. By this jn'ocess the 

 fibres on the surface of the fabric are partially dissolveil, and con- 

 verted into a glutinous substance, without the fibres in the body 

 of the fabric being destroyed. The fabric, after being passed 

 through the sulphuric acid, is quickly washed and rinsed in water, 

 to stop the action of the acid, and remove all traces of it, and it is 

 afterwards dried, when the part which has been acted on by the 

 acid, having impregnated and coated the fibres of the fabric, and 

 filled np the intcTsticcs between the warp and the weft, will con- 

 vert it into a parchment-like and impermeable material. 



Ej/ect of Steam Heat on Hay. — A correspondent from Ran cocas, 

 N. J., favors us with a specimen of hay-wrapping which had been 

 on a steam pipe fur 9 years; the pipe carrying steam at bb lbs. 

 The specimen is of a chocolate brown and very friable ; but it 



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