The 18th century saw the sudden emergence of Birmingham at the forefront of worldwide developments in science, technology, medicine, philosophy and natural history as part of the cultural transformation now known as the Midlands Enlightenment. By the second half of the century the town's leading thinkers – particularly members of the Lunar Society of Birmingham such as Joseph Priestley, James Keir, Matthew Boulton, James Watt, William Withering and Erasmus Darwin – had become widely influential participants in the Republic of Letters, the free circulation of ideas and information among the developing pan-European and trans-Atlantic intellectual elite. The Lunar Society was "the most important private scientific association in eighteenth-century England" and the Midlands Enlightenment "dominated the English experience of enlightenment", but also maintained close links with other major centres of the Age of Enlightenment, particularly the universities of the Scottish Enlightenment, the Royal Society in London, and scientists, philosophers and academicians in France, Sweden, Saxony, Russia and America.