office than the rubber band, the rubber ruler, the pencil eraser, or the fountain pen? But these are only a few of the personal and indoor uses and applications. Rubber belting for machinery, fire engine and garden hose, steam engine packing, car springs, covers for carriages and the big guns of the navy, life preservers, billiard table cushions, and chemical and surgical apparatus in endless variety. The electrical world is almost entirely dependent upon it for the insulation of our ocean cables and electric light wires, for battery cups, and the insulating mountings of all electrical apparatus. The pneumatic bicycle tire could not exist without rubber, and the modern application of it to this use alone amounts to nearly four million pounds annually. Every automobile carriage takes twenty-five pounds of rubber for each tire, or 100 pounds altogether. This great and growing industry, together with the now common use of rubber tires on horse-drawn vehicles, raises the sum total of rubber employed in the arts to an enormous figure. That the sap of an uncultivated tree in a swampy, tropical, and malarial forest, thousands of miles from civilization, should cut so great a figure in the necessities of modern life, seems strange and unaccountable on any basis of probabilities. It is only another illustration of the possibilities of the patient and persistent work of the inventor. Charles Goodyear took this nearly worthless material, and made of it, as Parton said in 1865--“not a new material merely, but a new class of materials, applicable to a thousand divers uses. It was still India rubber, but its surface would not adhere, nor would it harden at any degree of cold, nor soften at any degree of heat. It was a cloth impervious to water; it was a paper that would not tear; it was a parchment that would not crease; it was leather which neither rain nor sun would injure; it was ebony that could be run into a mould; it was ivory that could be worked like wax; it was wood that never cracked, shrunk nor decayed. It was metal, ‘elastic metal,’ as Daniel Webster termed it, that could be wound round the finger, or tied into a knot, and which preserved its elasticity like steel. Trifling variations in the ingredients, in the proportion and in the heating, made it either pliable as kid, tougher than ox hide, as elastic as whalebone, or as rigid as flint.” CHAPTER XVIII. CHEMISTRY. ITS EVOLUTION AS A SCIENCE--THE COAL TAR PRODUCTS--FERMENTING AND BREWING--GLUCOSE, GUN COTTON AND NITRO-GLYCERINE--ELECTRO-CHEMISTRY --FERTILIZERS AND COMMERCIAL PRODUCTS--NEW ELEMENTS OF THE NINETEENTH CENTURY.