ART / Drawn, hung and newly quartered: The Chatsworth collection reveals a lot about drawing, and a good deal about the Second Duke of Devonshire too

The British Museum puts on some of the best exhibitions of drawing in the world, and its new show, 'Old Master Drawings from Chatsworth', is full of wonderful things. Sheets by Leonardo, Titian, Rembrandt and Rubens, for a start; and many more drawings by masters whose names are less resonant but belong to the first rank of Renaissance and Baroque artists: Ghirlandaio, Andrea del Sarto, Guido Reni, Guercino, Poussin, Holbein and Durer.

The drawings were bought in the first half of the 18th century by the First, Second and Third Dukes of Devonshire. The Second Duke was the most assiduous of these collectors. Most of the 2,000 drawings at Chatsworth were his purchases. He spent money like a king, but was also a considerable connoisseur and a man of learning. The 200 drawings at the British

Museum give a glimpse of aristocratic taste that was both magnificent and discriminating.

He could have commissioned painted ceilings and golden ballrooms but this duke relished art that was kept in his library. One serviceable definition of a drawing is that it's a work that you look at from about the same distance as you read a book, and I imagine old Devonshire like a bookman, closing the door behind him, taking out his treasures, poring over them, searching for those flourishes of pen and crayon that give the most intense and rarefied pleasure.

So we can do today. Michael Jaffe, who has selected and catalogued the exhibition, writes of 'noble passages' in a Titian drawing, pointing especially to the distant mountains and sky hatched in with perhaps a couple of hundred movements of the pen. He's right. One of the miracles of drawing is the way that it can reveal temperament. In this mysterious yet calm invention, a horse leaping out of a pond pursued by a swimming serpent, we sense not just the subject (which remains unexplained) but the intellect of the artist who gave it creation.

Or, to take a more disturbing example, think of the Duke taking out his drawings by Leonardo da Vinci. If he was a true lover of art, which I think he must have been, he would not have done so very often, nor for long. Here is Leonardo's study for his lost painting Leda and the Swan. The great bird nuzzles the naked woman. At her feet minute putti emerge from shells. It's a horrible insight into the mind of a great but flawed man, a genius who wished to control nature yet could not come to terms with the human nature that had occasioned his birth. His celebrated caricatures, four of which are on display, show similar horror of life. It is not altogether natural that a person obsessed with ideal beauty should also brood on ideal ugliness. So it was with Leonardo. No one has ever managed to explain this, but we turn our eyes from Leonardo while we gaze long on Titian.

I suppose it is true that the greatest old masters produced the greatest drawings. None the less we ought not to be overawed by drawings just because of their rarity and because they are attributed to famous names. But the Chatsworth exhibition is so stimulating because the major artists really don't disappoint, Leonardo being a special case. The Carracis and Domenichino are particularly elevated. And, by contrast, the weaker old masters are revealed. A view of a Venetian procession that has traditionally been given to Giovanni Bellini is reattributed by Jaffe to his brother Gentile. This seems just, given the relative strengths of the two artists and the quality of the drawing.

The Devonshires were mostly interested in Italian drawing but the exhibition also contains fine work from the French and Northern European schools. It is good to see Jacques Callot and an exquisite pastoral by Watteau. The Claudes are exquisite, Rubens characteristically noble, Holbein the Younger solid and sensitive. Rembrandt - who once owned this exhibition's Titian - stands apart. All his drawings are of the highest order, but I would single out the little picture of a cottage and a tree, done in brown ink with a reed pen. At first it looks as modest as its subject. Longer examination reveals not only draughtsmanly pride but also the nobility that Jaffe finds in the Italian master.

British Museum (071-323 8525) to 9 Jan.