From the historical point of view the invention of the cotton-gin was tremendous in its influence. This machine multiplied by many times the demand in the South for slave labor and made slaves far more profitable. One writer has said of Whitney: "He was, through his invention, probably one of the most potent agencies for the extension of slavery and the terrible struggle that marked the first half-century of our nation's existence. While he was quietly sleeping in his grave, the very earth was shaken with the tread of contending armies that he had done more than any other one man to call forth to battle; for there is little doubt that but for the invention of the cotton-gin slavery would not have lived out the century of the Revolution." Macaulay says: "What Peter the Great did to make Russia dominant, Eli Whitney's invention of the cotton-gin has more than equaled in its relation to the power and progress of the United States." In the light of the wonderful, widespread material growth and prosperity that have come to the whole of our country in recent years, Macaulay's statement is overdrawn. But as matters were when it was written by the great Englishman, it was probably true. Whitney achieved much success as the inventor of improved methods of manufacturing firearms. He was the first to conceive the plan of making the different parts of firearms by machinery, so that any part of a weapon would fit any other like weapon equally well. This principle has made possible the production of cheap watches, clocks, and sewing machines. He died in New Haven, Connecticut, January 8, 1825. CHAPTER X ANÆSTHETICS If those inventions and discoveries out of which have come widespread safety, happiness, or prosperity to mankind are to be considered great, then Dr. Morton's discovery of anæsthetics and its application to surgery is entitled to a high place among the world's discoveries and inventions. The pain that has been destroyed, the lives that have been saved, the sorrow that has been averted, give their testimony to the value of this discovery to humanity. An anæsthetic is administered to produce temporary insensibility to pain. At least something of anæsthetics was known to the ancients. Homer mentions nepenthe, a potion which was said to make persons forget their pains and sorrows. The word appears occasionally in literature. In "Evangeline" Longfellow refers to it in this line: "Crown us with asphodel flowers, that are wet with the dews of nepenthe." Virgil and other classical writers mention a mythical river Lethe which was supposed to surround Hades. Souls passing over to the happy fields of Elysium first drank from this river, whose waters caused them to forget their sorrows. Milton speaks of the mythical stream in the following passage from "Paradise Lost:" "Far off from these a slow and silent stream, Lethe, the river of oblivion, rolls her watery labyrinth."