On the great art of music Diderot has said little that is worth attending to. Bemetzrieder, a German musician, who taught Diderot's daughter to play on the clavecin, wrote an elementary book called Lessons on the Clavecin and Principles of Harmony. This is pronounced by the modern teachers to be not less than contemptible. Diderot, however, with his usual boundless good nature, took the trouble to set the book in a series of dialogues, in which teacher, pupil, and a philosopher deal in all kinds of elaborate amenities, and pay one another many compliments. It reminds one of the old Hebrew grammar which is couched in the form of Conversations with a Duchess--"Your Grace having kindly condescended to approve of the plan that I have sketched. All this your Grace probably knows already, but your Grace has probably never attempted," and so forth. The unwise things that men of letters have written from a good-natured wish to help their friends, are not so numerous that we need be afraid of extending to them a good-natured pardon. The beauty of Diderot's Salons is remarkable enough to cover a multitude of sins in other arts. There are few other compositions in European literature which show so well how criticism of art itself may become a fine art. CHAPTER IV. ST. PETERSBURG AND THE HAGUE. "What would you say of the owner of an immense palace, who should spend all his life in going up from the cellars to the attics, and going down from attics to cellar, instead of sitting quietly in the midst of his family? That is the image of the traveller." Yet Diderot, whose words these are, resolved at the age of sixty to undertake no less formidable a journey than to the remote capital on the shores of the Neva. It had come into his head, or perhaps others had put it into his head, that he owed a visit to his imperial benefactress whose bounty had rendered life easier to him. He had recently made the acquaintance of two Russian personages of consideration. One of them was the Princess Dashkow, who was believed to have taken a prominent part in that confused conspiracy of 1762, which ended in the murder of Peter III. by Alexis Orloff, and the elevation of Catherine II. to the throne. Her services at that critical moment had not prevented her disgrace, if indeed they were not its cause, and in 1770 the Princess set out on her travels. Horace Walpole has described the curiosity of the London world to see the Muscovite Alecto, the accomplice of the northern Athaliah, the amazon who had taken part in a revolution when she was only nineteen. In England she made a pleasant impression, in spite of eyes of "a very Catiline fierceness." She was equally delighted with England, and when she went on from London to Paris, she took very little trouble to make friends in the capital of the rival nation. Diderot seems to have been her only intimate. The Princess (1770) called nearly every afternoon at