"When the rubber is thick enough it is cut off and is ready for market. Instead of a paddle he sometimes uses a mould of clay; formerly they made moulds resembling the human foot, and thus fashioned the rubber shoes that were worn in America forty or fifty years ago. Fantastic figures were traced on the shoes with the end of a hot wire, and the mould was generally soaked in water till it fell to pieces, and the clay could be washed out. The modern processes of working rubber have driven these shoes from the market, and very few of them are made at present. "A good day's work for one man is six pounds of rubber. Another way of hardening the gum is to place it in a kettle and suspend it over a small fire, taking care not to burn the material. When it is sufficiently reduced, and is still warm and plastic, it is shaped into balls or bricks, weighing several pounds each; the buyers prefer to have it dried on the paddle, as the natives occasionally commit frauds by putting sand or lumps of clay inside the masses while shaping them. The deception can only be detected by cutting carefully through the mass, and dividing it into small pieces. Frank suggests that the natives have probably heard of some of the tricks attributed to Connecticut Yankees, but I think he must be mistaken. "The rubber of the Amazon valley is considered the best in the world, and the amount of the product is rapidly increasing. I am told it is not far from six thousand tons a year, and will be increased to ten thousand tons as soon as the means of transportation from Bolivia are made more practicable. This does not include the rubber sent from the northern part of the continent, from the country not drained by the Amazon. "We call this substance 'India-rubber,' because it was first brought from the Indies, but, properly speaking, the name does not belong to it at the present day. The greater part of the rubber of commerce is from South America, which produces more than all other countries together." "And why is it called _rubber_?" Frank asked. "Because," replied Fred, "it was first used in England for rubbing out pencil-marks. It was imported into England for that purpose about the end of the last century, and was greatly esteemed by artists, who paid high prices for it; it was popularly called 'lead-eater,' and in some parts of England it is yet known by that name. It was not until 1820 that its use extended much beyond the erasure of pencil-marks; its first important use was in the manufacture of water-proof clothing, and about the same time it was employed for the formation of flexible tubes, and for other purposes.