ELASTIC GUMS 283 



of the rubbery curd has set. Then he dips the paddle into 

 the creamy hquid again, and repeats the operation till suc- 

 cessive layers form a cake of consideral^le thickness. The 

 cake is then cut from the paddle, and hung up to dry until 

 firm enough to pack for transportation. Crude rubber 

 comes into the market also in the form of sheets, balls, or 

 masses of various shapes; and is often mixed with a con- 

 siderable quantity of clay, bark, and other impurities. 



Rubber was first made known to Europe in the report of 

 Columbus' second voyage, where the statement occurs that 

 the Indians were found playing with elastic balls which 

 bounced better than the "wind balls " of Castile. It was not, 

 however, till after the middle of the 18th century that this 

 elastic material came much into use. For many years it was 

 scarcely more than a curiosity, serving in a practical way for 

 little else than to rub out pencil marks. From this circum- 

 stance it gained the name "rubber" and was called "india- 

 rubber" because of its importation from the West Indies. 

 Caoutchouc did not come from Asia till much later. 



As the unique properties of rubber — its unequaled elas- 

 ticity combined with its great imperviousness to moisture — 

 became more fully realized, effort was made to bring it into 

 wide use. Thus, it was manufactured into elastic w^ebbing, 

 overshoes, waterproof garments, and various impervious 

 fabrics. Such goods became popular for a while, but their 

 use was much restricted by the fact that the best rubber ob- 

 tainable was apt to harden and crack in cold weather, and to 

 soften or grow stickj^ in summer. Moreover, it was found that 

 unprotected surfaces of pure rubber adhere; and that articles 

 made of it were often worthless after a few months keeping, 

 and were ruined by contact with oils. Much futile effort was 

 expended to remedy these defects. Finally in 1844, Charles 

 Goodyear, an American, announced his discovery that mixing 

 a little sulphur with caoutchouc, and subjecting it to con- 

 siderable heat, produces a substance that is even more elas- 

 tic than pure rubber, is unchanged by any temperature be- 

 tween — 20° and + 180°C., is less affected by oils or other 

 solvents of the unchanged caoutchouc, does not become 

 adhesive, and keeps well. This process of combining sulphur 



