Jefferson claimed to have taught himself Spanish during his nineteen-day journey to France, using only a grammar guide and a copy of "Don Quixote". Linguistics played a significant role in how Jefferson modeled and expressed political and philosophical ideas. He believed that the study of ancient languages was essential in understanding the roots of modern language. He collected and understood a number of American Indian vocabularies and instructed Lewis and Clark to record and collect various Indian languages during their Expedition. When Jefferson removed from Washington after his presidency, he packed 50 Native American vocabulary lists in a chest and transported them on a river boat back to Monticello along with the rest of his possessions. Somewhere along the journey, a thief stole the heavy chest, thinking it was full of valuables, but its contents were dumped into the James River when the thief discovered it was only filled with papers. Subsequently, 30 years of collecting were lost, with only a few fragments rescued from the muddy banks of the river.