Processes in the Useful Arts. 345 



and copper, yet great care and experience are necessary to its production. 

 The following is the exact method given by the patentees. 



Take equal quantities of zinc and copper, and melt them at the lowest 

 temperature at which copper will fuse. Having mixed them perfectly by 

 stirring, add zinc in small portions till the alloy in the crucible assumes 

 a yellow colour like brass, then continue adding the zinc till the colour 

 changes to a purple or violet, and becomes perfectly white, which is the 

 colour necessary to its perfection. It may then be cast into ingots, or in- 

 to any required form, and Yvhen cold, it will have the appearance of an al- 

 loy of fine gold and copper. 



The great art in making the alloy consists in working with the lowest 

 temperature, for if the temperature is too great the zinc will fly off in 

 fumes, and the product will be spelter or hard solder. From this cause it 

 is difficult to make the alloy preserve its character when remelted. The 

 alloy consists of a hundred parts of copper, and of from fifty-two to fifty- 

 five parts of zinc. 



\. Account of a Patent Substitute fur Leather. Invented by Mr Thomas 



Hancock. 



In a former patent, Mr Hancock proposed to form a substitute for 

 leather, by depositing caoutchouc in a fluid state upon loose fibres of 

 wool, cotton, or flax, felted or matted together. In the present patent, 

 he uses a woven cloth, made of wool, cotton, or flax. When this cloth is 

 stretched upon a flat surface, the composition to be presently described is 

 spread over it. Above the composition, a uniform layer of wadding, made 

 of cotton, flax, wool, silk, or hair, is to be laid, and the whole pressed be- 

 tween a pair of rollers, in order to force the fluid composition among the 

 fibres. It is then to be dried at a temperature not exceeding 80° or 90° 

 of Fahrenheit. 



Mr Hancock has given us the two following compositions, to be used 

 according to circumstances. 



First composition. — Dissolve two pounds of caoutchouc in one gallon of 

 oil of turpentine and highly rectified coal tar. Add six ounces of black 

 resin, two pounds of strong glue size, and one pound of yellow ochre, 

 whitening, or powdered pumice. 



Second composition. — Dissolve 14 lb. of caoutchouc as before, and having 

 melted and mixed one pound of glue size and resin in a steam bath, add 

 the dissolved caoutchouc to it, stirring while mixing them. The whole 

 must then be strained through a sieve. 



The first of the above compositions must be used when a cheap and stiff 

 substance is required, and the proportions may be one-third part whiten- 

 ing or glue ; but when a strong and pliant substance is wanted, the se- 

 cond composition, in which the caoutchouc predominates, is to be preferred. 



A substance like leather may be formed by joining together several 

 thicknesses before they are dry. When leather for the soles of shoes is re- 

 quired, Mr Hancock proposes to use, as the groundwork, wool and cotton 

 in equal quantities. For pipes, straps, &c. he proposes chopped hemp and 



