Gilchrist began a systematic study of Hindustani, and from this work he created his first dictionary. In 1785 he requested a year's leave from duty to continue these studies. This leave was eventually granted in 1787 and Gilchrist never returned to the Medical Service. He spent 12 years living at various places, including Patna, Faizabad, Lucknow, Delhi, and Ghazipur. He travelled extensively to work with native speakers and also to garner material. In Ghazipur, to help finance his work, he also engaged in the production of indigo, sugar and opium – an enterprise which was initially successful but eventually failed.