It cannot be said, either, that the American farmer studied the philosophy of agriculture. He owed his crops less to intelligent cultivation of the soil than to provident Nature in a new and untilled country. Both his methods and his implements were bad, and resulted in that land spoliation which has been the bane of American industry. "Agriculture in the South," said John Taylor, of Caroline, "does not consist so much in cultivating land as in killing it"; and the statement was scarcely less true when applied to the Northern farmer. The soil was rapidly exhausted by planting the same crop year after year, for it was easier to take up fresh land than to restore productivity to the old. Indeed, the comments of foreign travelers at the close of the century suggest doubts as to whether the American farmer understood the importance of rotating his crops and of fertilizing his fields. The farming implements in use showed little of that mechanical ingenuity which is now characteristic of the American people. The plough was still a clumsy affair with heavy beam and handles, and wooden mould-board. The scythe, the sickle, and the flail were the same as their forbears had used for centuries. The demand of Europe for the food products of the Northern and Middle States obscured for a time the importance of cotton as an article of export. In 1790, South Carolina and Georgia, then the only cotton-growing States, produced less than two million pounds of inferior quality, none of which was exported. A decade later thirty-five million pounds were raised, one half of which was exported; and Virginia, North Carolina, and Tennessee had begun the cultivation. This sudden development was due to the invention of the cotton gin by Eli Whitney, in 1793. This machine facilitated the separation of the seed from the fiber of the short-staple variety of cotton, which alone could be profitably cultivated in the uplands, and thus made possible a vast extension of the area of cotton culture. The cotton gin came at an opportune moment for the Southern planters, since rice and indigo were declining in importance as exports, and their gangs of African slaves were likely to become a burden. They could now cultivate cotton under an extensive system of agriculture with large immediate profits. Experience proved, however, that the system was extraordinarily wasteful, leading to a rapid exhaustion of the soil. This ever-recurring exhaustion of the soil and demand for new land was a potent cause of the incessant pressure of population into the virgin lands of the Southwest, in succeeding decades.