When white men first came to South America and explored the Amazon River and adjoining territory, they saw native Indians at home, and had many surprises regarding the life they lead. They noticed a game played with a large ball of dark substance, that bounded high when it struck the ground. It was natural for the strangers to examine the ball, and try to find out what it was made of. The Indians called it by a name that sounded like "ca-chook." The substance was not rigid, but flexible; could be kneaded out of shape, but returned to its round form when pressure was released. The Indians said it was the dried juice of a tree, but for some time the curious explorers had no idea what trees produced it. Some one of them, handling a bit of the strange substance, — possibly writing a letter describing it — dis covered that it takes out pencil marks. He was probably delighted to discover this useful property of the bouncing ball. He called it "rubber," and this name has always stuck, and no other sub stance has been found so good for pencil erasers, to this day.
We can imagine the interest roused in Europe by the specimens of rubber that reached there from America. Explorers in the Amazon territory, and other tropical regions, found that the natives had rubber in their possession. Not long before our Revolution, a party of Frenchmen saw natives tapping trees and gathering the flow of juice. This was the first discovery by white men of trees that yield rubber. They learned how the juice was converted into rubber, in the districts now forming the countries of Brazil and Guiana.
What real good is there in a substance that can be pressed out of shape, but returns when pressure is removed? That is capable of being stretched and of flying back to its original length? At first the new product seemed more interesting than useful. The growing European demand for the rubber stimulated the Indians to go on gathering "wild rubber." The vast number of uses to which rubber is put to-day make it seem a necessity of life. We smile at the grave scientist of the eighteenth century who gave out as his judgment that the new sub stance would attain some popularity as an eraser of pencil marks, but, as for him, bread crumbs were very satisfactory for that purpose. Not
long afterward, Samuel Piat discovered a process of waterproofing cloth by treating it with India rubber dissolved in turpentine. Our raincoats take their names from a Mr. MacIntosh who im proved upon the original patent. Then came the invention of Goodyear, who, by the addition of sulphur, hardened rubber, and adapted it to many uses.
In one form and another, we can count a dozen rubber articles in daily use by us, and not one could be made to serve the purpose so well if made by any other material. No known substance has the elasticity of rubber, and springs back to its original shape when tension is released. No substitute for the indispensible rubber band is likely to appear.
The modern rubber industry is built, however, upon the process of vulcanization, which hardens and darkens the crude caoutchouc, reducing its elasticity, in various degrees, according to the proportion of sulphur added, and the thoroughness of their union. Vulcanite is the name given to the product. It is not so sticky as pure rubber, it resists ordinary solvents, and changes of tempera ture. It is adulterated with pigments and other mineral substances. The colored "rubber goods" in the druggist's window illustrate vulcanite in modern everyday conveniences of the household. Thirty to 70 to per cent. of the weight of rubber tires of vehicles is mineral substance. The rubber plate of false teeth is largely coloring matter.
Ebonite is the hardest form of vulcanite, black, brittle, shiny. We buy it in combs, photographic trays, and in the insulation of electric apparatus.
The invention of rubber tires for vehicles has given the rubber market a tremendous lift within recent years. Automobiles consume the greater part of the supply, and need more than the market can furnish. The price keeps step with the de mand. The cultivation of rubber in plantations has been started, in order that rubber production may be put on a scientific basis, and the yield increased.