When he was sixty-three he added Arabic to his other acquirements. It is not quite clear whether he had in view any purpose in connection with his professional work beyond the desire to know the originals of all the authorities quoted in his lectures. But, when he had sufficiently mastered the language to be able to read the Koran, he knew that he had two grounds for self-congratulation, and these were sufficiently characteristic. One was that he had his revenge on Gibbon, who had described so triumphantly the career of the Saracens and who yet had not known a word of their language. The other was that he was now able to pray in Arabic for the conversion of the Mohammedans. About the same time he began to learn Dutch. He assigned as one reason for this that he wanted to read Kuenen's works. But as the only one of these that he had was in his library already, having come to him from the effects of a deceased friend, it is possible that this was just an unconscious excuse on his part for indulging in the luxury of learning a new language--that he read Kuenen in order to learn Dutch, instead of learning Dutch in order to read Kuenen. However, his knowledge of the language enabled him to follow closely a movement which excited his interest in no common degree, viz. the secession of a large evangelical party from the rationalistic State Church of Holland, under Abraham Kuyper, the present Prime Minister of that country, and their organisation into a Free Presbyterian Church. Other languages at which he worked during this period were Spanish, of which he acquired the rudiments during his tour in California; and Dano-Norwegian, which he picked up during a month's residence at Christiania in 1877, and furbished for a meeting of the Evangelical Alliance at Copenhagen in 1884. All this time he was pursuing his Patristic and other historical studies with unflagging vigour, always writing new lectures, always maintaining his love of abstract knowledge and his eager desire to add to his already vast stores of learning. When, a year and a half before his death, a vacancy occurred in the Church History chair in the College, he stepped into the breach and delivered a course of lectures on the Fathers, which took his class by storm. "His manner," says one who heard these lectures, "was quite different in the Church History classroom from what it was in that of Systematic Theology. In the latter he taught like a man who felt wearied and old; but in the former he showed a surprising freshness and enthusiasm. It was delightful to see him in the Church History class forgetting age and care, and away back in spirit with Origen and his other old friends."