“It is impossible for the emotions, arising from the sublime, to be felt beyond what they are here: so beautiful an arch, so elevated, so light, and springing, as it were, up to heaven, the rapture of the Spectator is really indescribable!”

Jefferson comments on Natural Bridge in western Virginia, which he considers one of the most remarkable sights in the state and indeed the world. Here Jefferson advocates for the beauty of his home state in terms that reflect the Romantic aesthetics of the “sublime.” The passage shows Jefferson going beyond practical facts to deal with aesthetic concerns.

“But all the manna of heaven would never raise the Mouse to the bulk of the Mammoth.”

This quote comes amid Jefferson’s refuting a claim by the French author de Buffon that animals and people in America have “degenerated” and grown smaller and less vigorous. Jefferson argues that since all animals receive nourishment from the same source and have within them fixed principles of growth and dimension, they will not differ from one area of the globe to another. Jefferson is eager to defend biological life in America from the attack of a European naturalist.

“Nature has hidden from us her modus agendi. Our only appeal on such questions is to experience.”

Jefferson states a principle of scientific inquiry, that we must rely on empirical observations to form conclusions about the workings (or modus agendi) of nature because those workings are otherwise indiscernible. He is again refuting Buffon’s thesis, in particular the idea that heat is favorable and moisture unfavorable to animal growth.