More than half of this enormous crop is still exported in spite of the great demand at home. Cotton became and has continued to be the greatest single export of the United States. In ordinary years its value is greater than the combined value of the three next largest exports. It is on cotton that the United States has depended for the payment of its trade balance to Europe. Other momentous results followed on the invention of the cotton gin. In 1793 slavery seemed a dying institution, North and South. Conditions of soil and climate made slavery unprofitable in the North. On many of the indigo, rice, and tobacco plantations in the South there were more slaves than could be profitably employed, and many planters were thinking of emancipating their slaves, when along came this simple but wonderful machine and with it the vision of great riches in cotton; for while slaves could not earn their keep separating the cotton from its seeds by hand, they could earn enormous profits in the fields, once the difficulty of extracting the seeds was solved. Slaves were no longer a liability but an asset. The price of "field hands" rose, and continued to rise. If the worn-out lands of the seaboard no longer afforded opportunity for profitable employment, the rich new lands of the Southwest called for laborers, and yet more laborers. Taking slaves with them, younger sons pushed out into the wilderness, became possessed of great tracts of fertile land, and built up larger plantations than those upon which they had been born. Cotton became King of the South. The supposed economic necessity of slave labor led great men to defend slavery, and politics in the South became largely the defense of slavery against the aggression, real or fancied, of the free North. The rift between the sections became a chasm. Then came the War of Secession. Though Miller was dead, Whitney carried on the fight for his rights in Georgia. His difficulties were increased by a patent which the Government at Philadelphia issued in May, 1796, to Hogden Holmes, a mechanic of Augusta, for an improvement in the cotton gin. The Holmes machines were soon in common use, and it was against the users of these that many of the suits for infringement were brought. Suit after suit ran its course in the Georgia courts, without a single decision in the inventor's favor. At length, however, in December, 1806, the validity of Whitney's patent was finally determined by decision of the United States Circuit Court in Georgia. Whitney asked for a perpetual injunction against the Holmes machine, and the court, finding that his invention was basic, granted him all that he asked.