David Bailie Warden (1778-1845) emigrated to the United States from Ireland as a young man and became a respected member of the cultural, scientific, and diplomatic circles of his adopted nation. His writings on and interest in politics, literature, medicine, chemistry, natural science, and education resulted in lively correspondence with many leaders in these fields -- among them Jefferson, Gallatin, Baron Alexander von Humboldt, Joseph Gay-Lussac, Washington Irving, and Alexander Dallas Bache. These letters and manuscripts are published here for the first time.