The article focuses on two Dutch doctors – the Boate brothers, Arnold (1606-1653) and Gerard (1604-1650) – medical graduates of Leiden University who moved to London in 1630 to work as practising physicians. The brothers contributed to diverse forms of knowledge as part of the new science, including agriculture, anatomy, entomology, geography, industrial history, medicine, metallurgy, mineralogy and theology, but are known primarily for Gerard’s posthumously published ground-breaking book, Irelands Naturall History (1652) for which Arnold did the spadework. The Boates collaborated on some of the most important intellectual enterprises of the seventeenth century, and worked alongside the leading intellectuals of the period, including innovative Irish thinkers James Ussher and Robert Boyle, and Samuel Hartlib, mainspring of a major knowledge network. The Boates’ activities in Leiden, London, Dublin and Paris furnish a prototype for interdisciplinary engagement. The brothers were key members of multiple interlocking extra-institutional groupings. Active as part of a Baconian Office of Address and engaged both in the Hartlib Circle and the more shadowy Invisible College, they laboured in the seedbed of what would later become the Royal Society and the Dublin Philosophical Society. Irelands Naturall History is a model of the regional history that Francis Bacon saw as a vital branch of cosmography.