By 1800, Brown was firmly established amongst Irish botanists, and was corresponding with a number of British and foreign botanists, including Withering, Dickson, James Edward Smith and José Correia da Serra. He had been nominated to the Linnean Society of London; had contributed to Dickson's "Fasciculi"; was acknowledged in a number of other works; and had had a species of algae, "Conferva brownii" (now "Aegagropila linnaei") named after him by Lewis Weston Dillwyn. He had also begun experimenting with microscopy. However, as an army surgeon stationed in Ireland there seemed little prospect of him attracting the notice of those who could offer him a career in botany.