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Rh manufacturing industries caused a greater demand for foodstuffs and raw materials and induced the repeal of her corn laws. The great Irish potato famine, the rebellions in Continental Europe and the Crimean War increased European dependence upon the United States for food supplies.

At the same time the Eastern states were rapidly developing the manufacturing industries and using a larger food supply. The Pre-emption Law of 1841 stimulated immigration and furnished an easy means for the political refugees from Europe to obtain homes. The immigration from 1840 to 1850 was almost three times as great as in the previous ten years, and the twenty year period, from 1840 to 1860, added more than 4,300,000 immigrants to the population.

By far the most important factor in this transformation was the invention of farm machinery. Manning patented the mowing machine in 1831. Hussey patented a grain reaper in 1833, and McCormick patented a similar machine in 1834. Threshers came into use sometime in the thirties and were combined with the fanning mill before 1850. John Deere made the first steel plow in 1837. The corn planter and the two-horse cultivator came into use during this period, and by 1860 portable steam engines were being used to run the threshers.

The invention of the reaper was one of the greatest events in the history of modern industry and is really deserving of a chapter by itself. Yet it is doubtful if it effected a greater saving in labor than did the corn planter and cultivator when it is considered that corn is our principal crop.