Aristotle and Theophrastus in early times, Gesner in the sixteenth century, Ray, Grew, Malpighi and Willughby in the seventeenth century, had been the writers of the principal textbooks on zoölogy. Buffon (1707-1785) and Linnæus (1707-1778) were the founders of modern natural history in the eighteenth century. Buffon described species, while Linnæus classified them. Linnæus named _Homo sapiens_ as a distinct species in the order of primates which includes apes, lemurs, and bats, and fixed man's place in nature. The medical sciences were revolutionized by the researches of Edward Jenner. He applied the scientific methods of the chemists, mathematicians, and astronomers to medicine and through accurate observation, skillful experimentation, careful generalization, and thorough verification, founded preventive medicine. His discovery of vaccination as a preventive for smallpox, communicated to the Royal Society in a very interesting paper in 1798, was the pioneer of the many brilliant advances of our day. The Freiberg School of Mines, the Woolwich Observatory, the School of Civil Engineering in Paris (1747), the Universities of Göttingen (1737), Bonn (1777), Brussels (1781), Yale (1701) and Princeton (1746) were founded in this century. Modern industrialism began in the final part of this century. The invention of the steam engine by Watt resulted in giving the greatest impulse to material civilization the world ever experienced. This invention was the direct result of the experimental work of Boyle, Newton, Black, Cavendish, Davy, Priestley, and Lavoisier. It illustrates how the scientific discoveries of one generation furnish the data for the advancement of knowledge by the next generation and how a single invention may change the whole aspect of life, giving employment for vast numbers of people, developing settlement in foreign lands, starting new industries, and extending the fields of commerce. The history of the development of the steam engine from the results of a few basic physical researches by British scientists forms one of the grandest stories in the history of science. The new aspect assumed by the world as a result of the great scientific discoveries and the increases in industry and commerce which followed them seemed strange to the people who were unused to rapid progress. There was a disturbed feeling akin to fear abroad while the new ideas were being popularized and disseminated throughout the world. The movement in favor of enlightenment was strongest in France because of the social, political, and religious oppression of the people. It ended in the French Revolution, which strengthened the respect for reason and human rights throughout the world. CHAPTER X PHYSICAL SCIENCES IN THE NINETEENTH CENTURY