During his labour on this undertaking, which was completed in 1829, and through arduous study of character patterns, he became convinced of the superiority of the "natural" classification system devised by Antoine Laurent de Jussieu – a system that he believed reflected the great plan of nature as distinct from the "artificial" system of Linnaeus followed in the "Encyclopaedia of Plants". This conviction found expression in "A Synopsis of British Flora, arranged according to the Natural Order" (1829) and in "An Introduction to the Natural System of Botany" (1830).