After the gentlemen rejoined us came in the Duke and Duchess of Argyle, and Lord and Lady Blantyre. These ladies are the daughters of the Duchess of Sutherland. The Duchess of Argyle is of a slight and fairy-like figure, with flaxen hair and blue eyes, answering well enough to the description of Annot Lyle, in the Legend of Montrose. Lady Blantyre was somewhat taller, of fuller figure, with very brilliant bloom. Lord Blantyre is of the Stuart blood, a tall and slender young man, with very graceful manners. As to the Duke of Argyle, we found that the picture drawn of him by his countrymen in Scotland was every way correct. Though slight of figure, with fair complexion and blue eyes, his whole appearance is indicative of energy and vivacity. His talents and efficiency have made him a member of the British cabinet at a much earlier age than is usual; and he has distinguished himself not only in political life, but as a writer, having given to the world a work on Presbyterianism, embracing an analysis of the ecclesiastical history of Scotland since the reformation, which is spoken of as written with great ability, in a most candid and liberal spirit. The company soon formed themselves into little groups in different parts of the room. The Duchess of Sutherland, Lord Carlisle, and the Duke and Duchess of Argyle formed a circle, and turned the conversation upon American topics. The Duke of Argyle made many inquiries about our distinguished men; particularly of Emerson, Longfellow, and Hawthorne; also of Prescott, who appears to be a general favorite here. I felt at the moment that we never value our literary men so much as when placed in a circle of intelligent foreigners; it is particularly so with Americans, because we have nothing but our men and women to glory in--no court, no nobles, no castles, no cathedrals; except we produce distinguished specimens of humanity, we are nothing. The quietness of this evening circle, the charm of its kind hospitality, the evident air of sincerity and good will which pervaded every thing, made the evening pass most delightfully to me. I had never felt myself more at home even among the Quakers. Such a visit is a true rest and refreshment, a thousand times better than the most brilliant and glittering entertainment. At eleven o'clock, however, the carriage called, for our evening was drawing to its close; that of our friends, I suppose, was but just commencing, as London's liveliest hours are by gaslight, but we cannot learn the art of turning night into day. LETTER XV. May 4. MY DEAR S.:--