Percival's favorite topics, when evening came and we rested from our stony labors, were the modern languages and the philosophy of universal grammar. They seemed to have filled the niches in his heart, from which he had banished, or tried to banish, the Muses. The subtile refinements of Bopp were a perpetual luxury to him; he derived language from language as easily as word from word; and, once started in the intricacies of the Russian or the Basque, there was no predicting the end of the discourse. Thus were thrown away, upon a solitary listener, midnight lectures which would have done honor to the class-rooms of Berlin or the Sorbonne. In looking at such an instance of intellectual pleasure and acumen, as connected in no small degree with the study of foreign languages, one cannot avoid associating together the unsolved mystery of that discrepancy of tongues prevailing in different countries with the disagreeing _floras_ and _faunas_ of the same regions,--each diversity bearing alike the unmistakable marks of Omnipotent design for the happiness and improvement of man. The perfection of his memory was amazing. During the year following the survey, when we had frequent occasion to compare recollections, I observed that no circumstance of our labors was shadowy or incomplete in his memory. He could refer to every trifling incident of the tour, recall every road and path that we had followed, every field and ledge that we had examined, particularize the day of the week on which we had dined or supped at such a tavern, and mention the name of the landlord. I asked him how he was able to remember such minutiae. He replied, that it was his custom, on going to bed, to call up, in the darkness and stillness, all the incidents of the day's experience, in their proper order, and cause them to move before him like a diorama through a spiritual morning, noon, and evening. "It has often appeared to me," he said, "that in this purely mental process I see objects more distinctly than I behold them in the reality." But his memory doubtless gained an immense additional advantage from his habitual seclusion, from his unconcern with the distracting customs of society, and, most of all, from the imperturbable abstraction under which he studied and observed. With him there was no blending of collateral subjects, no permitted intrusion of things irrelevant or trivial, so that the channels of his thoughts were always single, deep, and traceable. It was a mental straightforwardness and conscientiousness, as rare, perhaps, as moral rectitude itself.