Goodyear found that he could vary this "vulcanized rubber" at will. By adding a little more sulfur he got a hard substance which, however, could be softened by heat so as to be molded into any form wanted. Out of this "hard rubber" "vulcanite" or "ebonite" were made combs, hairpins, penholders and the like, and it has not yet been superseded for some purposes by any of its recent rivals, the synthetic resins.
The new form of rubber made by the Germans, methyl rubber, is said to be a superior substitute for the hard variety but not satisfactory for the soft. The electrical resistance of the synthetic product is 20 per cent, higher than the natural, so it is excellent for insulation, but it is inferior in elasticity. In the latter part of the war the methyl rubber was manufactured at the rate of 165 tons a month.
The first pneumatic tires, known then as "patent aerial wheels," were invented by Robert William Thomson of London in 1846. On the following year a carriage equipped with them was seen in the streets of New York City. But the pneumatic tire did not come into use until after 1888, when an Irish horse-doctor, John Boyd Dunlop, of Belfast, tied a rubber tube around the wheels of his little son's velocipede. Within seven years after that a $25,000,000 corporation was manufacturing Dunlop tires. Later America took the lead in this business. In 1913 the United States exported $3,000,000 worth of tires and tubes. In 1917 the American exports rose to $13,000,000, not counting what went to the Allies. The number of pneumatic tires sold in 1917 is estimated at 18,000,000, which at an average cost of $25 would amount to $450,000,000.
No matter how much synthetic rubber may be manufactured or how many rubber trees are set out there is no danger of glutting the market, for as the price falls the uses of rubber become more numerous. One can think of a thousand ways in which rubber could be used if it were only cheap enough. In the form of pads and springs and tires it would do much to render traffic noiseless. Even the elevated railroad and the subway might be opened to conversation, and the city made habitable for mild voiced and gentle folk. It would make one's step sure, noiseless and springy, whether it was used individualistically as rubber heels or collectivistically as carpeting and paving. In roofing and siding and paint it would make our buildings warmer and more durable. It would reduce the cost and permit the extension of electrical appliances of almost all kinds. In short, there is hardly any other material whose abundance would contribute more to our comfort and convenience. Noise is an automatic alarm indicating lost motion and wasted energy. Silence is economy and resiliency is superior to resistance. A gumshoe outlasts a hobnailed sole and a rubber tube full of air is better than a steel tire.
IX
THE RIVAL SUGARS
The ancient Greeks, being an inquisitive and acquisitive people, were fond of collecting tales of strange lands. They did not care much whether the stories were true or not so long as they were interesting. Among the marvels that the Greeks heard from the Far East two of the strangest were that in India there were plants that bore wool without sheep and reeds that bore honey without bees. These incredible tales turned out to be true and in the course of time Europe began to get a little calico from Calicut and a kind of edible gravel that the Arabs who brought it called "sukkar." But of course only kings and queens could afford to dress in calico and have sugar prescribed for them when they were sick.
Fortunately, however, in the course of time the Arabs invaded Spain and forced upon the unwilling inhabitants of Europe such instrumentalities of higher civilization as arithmetic and algebra, soap and sugar. Later the Spaniards by an act of equally unwarranted and beneficent aggression carried the sugar cane to the Caribbean, where it thrived amazingly. The West Indies then became a rival of the East Indies as a treasure-house of tropical wealth and for several centuries the Spanish, Portuguese, Dutch, English, Danes and French fought like wildcats to gain possession of this little nest of islands and the routes leading thereunto.