He is principally known for his study of the Hindustani language, which led to it being adopted as the lingua franca of northern India (including present-day Pakistan) by British colonists and indigenous people. He compiled and authored "An English-Hindustani Dictionary", "A Grammar of the Hindoostanee Language", "The Oriental Linguist", and many more. His lexicon of Hindustani was published in Arabic script, Nāgarī script, and in Roman transliteration. He is also known for his role in the foundation of University College London and for endowing the Gilchrist Educational Trust.