516 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



considerable heat, such as the valves and packing for steam- 

 engines, washers for pipe-joints, etc. This consists in mixing 

 the rubber or its compounds with carbon, in the form of 

 lamp-black, soot, or ground charcoal, in the proportion of four 

 parts of carbon to one of rubber, the proportions varying 

 with the nature of the article to be manufactured, and with 

 the quality of the rubber; the better this is, the greater being 

 the quantity of carbon that may be mixed with it. For wa- 

 ter-proofing fabrics, such as tarpaulins for covering wagons, 

 three to four parts of carbon to one of rubber will be found 

 most suitable ; while as packing for steam-engines and pipes, 

 where great heat is to be resisted, from five to six parts of 

 carbon to one of rubber will yield a compound best adapted 

 to the purpose. The mixture of the two is accomplished by 

 the employment of rollers provided with spiral cutters, into 

 and between which the rubber is fed by a hopper, which also 

 supplies the carbon during the process, the rollers being very 

 powerful and fixed in strong bearings. The process requires 

 that the rollers be heated by steam, and that the temperature 

 be maintained at about 250 Fahr. The rubber will be thus 

 cut, torn, and masticated in combination with the dry carbon, 

 and discharged from the delivering end of the machine in a 

 hot, plastic, homogeneous mass, whence it may be recon-veyed 

 to the feeding end for a second and more complete treatment 

 if necessary. It may then be applied directly to the surface 

 of a textile fabric, without the use of any additional expensive 

 material, by the agency of heated rollers, which cause the 

 mixture to be incorporated in the interstices of the fabric. 

 If, however, the object be to secure a coating only, a com- 

 pound of rubber is first applied, and upon this the carbon 

 mixture is rolled. 



The great advantage of using cloth treated with this rub- 

 ber for washers and steam machinery is its complete resist- 

 ance to heat. Ordinary rubber flanges thus exposed become 

 hardened into vulcanite, and rapidly lose all their value. 

 Tarpaulins and water-proof sheets remain durable and pliant, 

 neither cracking nor hardening in cold, nor being injuriously 

 affected by heat. The inventor is the same Mr. Mackintosh 

 whose name is so familiar in connection with water-proofing 

 compounds. 18 A, April 24, 1874, 140. 



