"It is caoutchouc mixed with sulphur. Unless a small quantity of brimstone is added in the manufacture of overshoes, they become soft when exposed to heat and hardened when exposed to cold; but it was discovered that the sulphur will keep them from being affected by changes in temperature. When a large amount of sulphur is used, the India-rubber, becomes as hard as horn or wood, and this is the substance called vulcanite. Now the gum is imported in masses, to be wrought over by our skillful mechanics."