Dirk van Miert: Introduction Gerhard Holk: The First Anthropologist of America: Petrus Martyr de Angleria (1457–1526) and his Epistolary Reports De orbe novo decades octo Candice Delisle: ‘The Spices of Our Art’. Medical Observation in Conrad Gessner’s Letters Florike Egmond: Observing Nature. The Correspondence Network of Carolus Clusius (1526–1609) William Stenhouse: Monumental Letters in the Late Renaissance Dirk van Miert: Philology and Empiricism: Observation and Description in the Correspondence of Joseph Scaliger (1540–1609) Adam Mosley: Reading the Heavens: Observation and Interpretation of Astronomical Phenomena in Learned Letters circa 1600 Peter N. Miller: Mapping Peiresc’s Mediterranean: Geography and Astronomy, 1610–36 Erik-Jan Bos and Theo Verbeek: Conceiving the Invisible. The Role of Observation and Experiment in Descartes’s Correspondence, 1630–50 Elizabethanne Boran: ‘A Cloud of Witnesses’: Scientific Observation in the Correspondence of Jame Ussher (1581–1656) Iordan Avramov: Men of Science as Objects of Observation in the Correspondence of Henry Oldenburg, 1641–77 Dirk van Miert: Concluding Observations on Communicating Observations