[2][3] In 1840, he was sent to Lebanon by the American Board of Commissioners for Foreign Missions as a medical missionary for the Dutch Reformed Church, and he was stationed at Beirut, Abeih, Sidon, and Mount Tabor.

After completing the translation in 1865, he went to New York to supervise its printing, also teaching Hebrew for two years at Union Theological Seminary and studying ophthalmology.

He also taught astronomy in its literary section, directed its observatory and meteorological station as well as the mission press, and edited its weekly journal al-Nashran.

He wrote Arabic textbooks on chemistry, internal medicine, physical diagnosis, and astronomy, publishing some of them at his own expense, and he helped Yaqūb Ṣarrūf and Fāris Nimr to establish the popular science magazine Al-Muqtaṭaf.

[citation needed] Often called al-Hakim during his lifetime, Van Dyck had a large medical practice in addition to his academic duties.