The appointment of the Professor to the Convenership of the Committee on the Mission to the Jews in 1856 marked a new era in its history, in respect both of the method of its operations and the field in which these have ever since been carried on. One of the results of the Crimean war, which had then but recently closed, was the opening of the Turkish empire for evangelistic enterprise; and it may be said that the Professor laid the foundations of the Mission in the Levant at the several stations occupied by the Church of Scotland, which are now known not only as places of great historic interest but as important centres of missionary activity in which the Church bears an honourable part. In the autumn of 1857 he undertook a journey to the East at the request of the Committee, and in the course of his travels there visited not only the principal Turkish cities on the coast, but Jerusalem and other places in Palestine and Syria, collecting information with a view to find openings for the planting of the Mission at suitable stations in addition to the two which had been already occupied. The report which he presented on his return led by degrees to a great expansion of the Mission, and several of his own students and others were through his influence induced to enter the service of the Committee. With many other claims on his attention, he ungrudgingly gave up a great part of his time to the administration of the affairs of the Mission, over which for nineteen years he continued to preside with great zeal and wisdom, pressing its claims on the members of the Church, and guiding and encouraging the missionaries by an intelligent and sympathetic interest in their arduous work. When in 1875 he retired from the Convenership, the General Assembly expressed its sense of the value of the distinguished services which he had rendered to the Church in this department of her work in the following terms: "The Assembly are satisfied that the present prosperity of the Jewish Mission, and the remarkable progress which it has made, has been mainly owing to the great labour, the learning, enthusiasm, and warm and intelligent Christian interest which Dr Mitchell has devoted during these years to the cause of Jewish conversion in connection with the Church of Scotland." After his retirement from the Convenership he but seldom attended the meetings of the Committee, for the reason, as he was once heard to say, that he did not wish to appear to hamper his successors; but he never ceased to take a deep interest in the Mission, and none rejoiced more than he in its growing prosperity.