270 GOODYEAR ON GUM-ELASTIC. 



GAS BAGS. 



DIRECTIONS FOR MENDING AIR-WORK. 



When any article of air-work is damaged, the place where 

 the air escapes may often be detected by applying it to the face 

 or ear. When the article is fully inflated, a surer way is to 

 wet it upon the outside, or immerse it in water, when, on 

 being pressed with the hand, the leak will commonly be found 

 by the bubble which is caused. A more searching trial is, to 

 fill the article wholly or in part with water, and press it. The 

 escape of air must be very slow, and the leak of little or no con- 

 sequence, not to be found in this way. 



When found, a few drops of gun cotton varnish, or what is 

 called collodion, applied to the spot, will often effectually stop a 

 small leak. A larger leak may sometimes be stopped with a few 

 drops of hot sealing-wax, or shoemakers' wax. The above are 

 recommended only as expedients where the vulcanizing cement 

 is not conveniently to be found. If the rent is large, it should 

 first be drawn up with a needle and thread, and the vulcanizing 

 cement applied in two or three alternate coats, each of which 

 dry in an ordinary temperature of a warm room in from fifteen 

 to twenty minutes ; the part which is coated with the cement 

 should afterwards be exposed to the rays of the sun for about 



