Meanwhile, as these events altered the life of the farmer, a burst of activity took place in invention and discovery. These activities had a delayed but considerable impact on farm methods and technology. The list of inventions and discoveries could hardly fit in this narrative, but this catalog of items reflects fairly well what men accomplished in the 19th century. The changes included such diverse elements as the invention of the cotton gin by Eli Whitney in 1793, the introduction of Mexican Upland cotton in 1805, the discovery of the cause of Texas fever in cattle in 1889, and the invention of the internal combustion tractor in 1892. These and many other achievements substantially changed the farm enterprise in two major directions: first, advances in technology allowed farmers to do more in less time; second, discoveries in science allowed farmers to increase the yield from the land. Farmers got more from each acre, plant, and animal. Farmers could use the savings in time brought by better implements and new machines to increase the amount of land farmed and the number of animals cared for. Presumably, the farmer could also use the saved time for greater leisure. In fact, however, they usually used the extra time for more work. In the 20th century they often used the saved time for outside employment. Farmers did this in the 19th century, but not so commonly as later. Greater man-hour efficiency gave the farmer more time to devote to managing his enterprise, to keeping records, and to studying his business. Technological efficiency also allowed farmers to use more land and more animals. The average size of farms steadily increased across the century. Furthermore, the new machines and the pure-bred livestock cost money which could be most profitable only if the farmer specialized in one, or at most two, types of enterprise. So the greater efficiency created by technology impelled farmers to greater specialization, and with specialization came even greater efficiency. Anyone who specializes will likely be more efficient because of the mastering of skills. He will also have a minimum of other cares to distract him. Of course, for the consumers, foreign or domestic, greater farming efficiencies resulted in abundant food at comparatively low cost.