150 History of Mechanical Inventions 



lus of zinc, half an ounce of grain or block tin, one ounce of regulus of 

 antimony, and two ounces of regulus of arsenic. 



4. Mr. Mackintosh's process for rendering impervious to water and air 

 all kinds of Cloths ; also Leather and Paper, Sfc. 

 This very valuable process, which we owe to the ingenuity of our 

 countryman Mr. Charles Mackintosh, consists in joining the surfaces 

 of two pieces of cloth by a flexible varnish, made of caoutchouc dis- 

 solved in the naptha obtained from the distillation of coal. The caout- 

 chouc, after being cut into thin shreds, is steeped in the varnish com- 

 posed of twelve ounces of caoutchouc to one wine glass full of the oil. 

 Heat may be applied, and the thick varnish must be strained through a 

 sieve of wire or horse-hair. The cloth is stretched on a frame, and 

 then covered by means of a brush with a coat of the elastic varnish. 

 When the varnish has become sticky, another piece of similar cloth, si- 

 milarly varnished, is laid upon the first, the surfaces being placed face to 

 face ; and, to promote the adhesion, they are pressed between a pair of 

 plain rollers, and then dried in a warm room. This cloth, of which we 

 have now several very fine specimens before us, besides being used for 

 outer garments to keep off rain, will be found highly useful for various 

 purposes in the arts and sciences. 



5. M. M. Farrimann and Thilly's Process for rendering Leather, 

 Canvass, Linen, 8$c. Water Proof. 



To 100 lbs. of the best linseed oil add l| lb. of sugar of lead, (acetate of 

 lead,) 1^ lb. of coloured amber, l| lb. of white lead, and 1£ lb. of pumice 

 stone, very finely powdered. When the solid substances are well ground 

 and mixed, they are to be boiled in the oil for ten hours over a moderate 

 fire, to prevent the oil from burning. The varnish thus made ought to 

 have such a consistence, that when mixed with a third part of its weight 

 of pipe clay, it is as thick as treacle. After settling for eight days, it is 

 then passed through a lawn sieve. In a solution of strong and clear 

 glue, as much pipe clay is to be ground as amounts in weight to the 

 tenth part of the oil employed, and mixed to the consistence of oint- 

 ment, adding the varnish by degrees, and stirring it with a wooden spa- 

 tula. When this varnish has become perfectly fluid by repeated stirring, 

 the requisite tint is given, by adding a fourth part of the colour ground 

 in oil. 



The composition is applied to each side of the linen, when stretched on 

 a wooden frame, with a spatula three inches broad and nine long. The 

 same composition is used for leather and skins ; but a smooth and bril- 

 lian t surface is given to them by the following varnish : Fi ve pounds of the 

 oil varnish, and an equal weight of well-clarified resin, are boiled, till the 

 resin is absorbed. Two pounds of oil of turpentine, having the required 

 colour ground with it, is then to be added, when passed through a lawn 

 sieve. This varnish is then to be applied with a brush. When the 

 ▼arnish is perfectly dry, it is rubbed even with a pumice stone and wa- 



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