What did Thomas Jefferson do as a scientist?
It's true that Thomas Jefferson contributed some new knowledge directly to science and technology. But his main scientific contribution was as a statesman of science. For half a century in public office and in private life, he led the growth of American optimism about science, technology, and the future. Jefferson wished he could be a scientist all the time. When he was leaving the presidency in early 1809, he wrote, "Nature intended me for the tranquil pursuits of science, by rendering them my supreme delight." In fact, do you know what Jefferson did during the week in 1797 when he became vice president of the United States? He presented a formal research paper on paleontology to his scientific colleagues in the American Philosophical Society! Paleontology is the study of fossils. It helps us understand all the Earth's forms of life.
Jefferson also helped invent modern agricultural science and technology. He believed agriculture was the most important science. By himself, he re-engineered the plow according to scientific principles that came from Sir Isaac Newton, the inventor of mathematical physics. Re-inventing the plow may sound boring. But ask yourself: In Jefferson's time, what technological devices were more important than the plow?
Jefferson also invented methods for excavating archeological sites. If you go to Jamestown today to watch researchers dig to discover how things really looked in the time of Pocahontas, you'll see them using methods first devised by Thomas Jefferson.
Jefferson also recognized good scientific work by others, and he made sure that the world knew about it. When he received some excellent mathematical work from Benjamin Banneker, America's first black man of science, he sent it to Europe's greatest scientists. For people who wanted to learn about science, Jefferson sometimes recommended a special book called Conversations on Chemistry, by a woman named Jane Marcet. The book presents a scientific conversation between a lady teacher and some young girls. Later it became one of America's most important science textbooks, even though women were not yet recognized as science-minded (including by Jefferson himself).
Much of what we now call "science" was known as "philosophy" in Jefferson's time. When the American Philosophical Society made Jefferson its president, he called it "the most flattering incident" of his life, even though he had also just been elected vice president of the United States. Jefferson remained president of the American Philosophical Society for nearly two decades, including during his two terms as president of the United States. This meant he was America's political leader and its scientific leader too. In the modern age, we usually think that we have become very scientific. But what would we think if the president of our National Academy of Sciences also became president of our country? That would be much like the situation 200 years ago, when Jefferson was president. (In the last century, we had no scientists as president. But we did have two engineers. Can you name them? I've placed their names at the bottom.)
This answer to your question barely begins to show how much Thomas Jefferson did for science and technology. If you want to read more, here's the name of a good book: Thomas Jefferson: Statesman of Science, by Silvio Bedini. You might also want to visit the University of Virginia mathematics department's web site on Jefferson and mathematics.
(Those two engineer-presidents were Herbert Hoover and Jimmy Carter. Theodore Roosevelt was actually quite science-minded too.)
Steven T. Corneliussen, Special Assistant for Science Communication, Accelerator Division (Other answers by Steven T. Corneliussen)