As Venice enriched his vision of colour, Rome stimulated him to paint new subjects suggested by ancient history and mythology. He knew little of Roman history or classical literature, yet enough to kindle his imagination; witness his 'Rise and Fall of the Carthaginian Empire' in the National Gallery. In these the figures are of no importance. The pictures still are landscapes, but freed from the necessity of being like any particular place. In work such as this, Turner had but one predecessor, the French Claude Lorraine. While the Dutchmen of the seventeenth century were painting their own country beautifully, Claude was living in Rome, creating imaginary landscapes. He called his pictures by the names of Scriptural incidents, and placed figures in the foreground as small and unessential as those of Turner. These classical landscapes, with their palaces and great flights of steps leading down to some river's edge, and the sea in the distance covered with boats carrying fantastic sails, never for a moment make the impression of reality. But they are beautiful compositions, designed to please the eye and stimulate the fancy, and are even attractive by virtue of their novel aloofness from the actual world. Turner set himself to rival Claude in his ideal landscapes, founded upon the stories of the ancient world. In his picture of 'Dido building Carthage,' he painted imaginary palaces, rivers, and stately ships, in the same cool colouring as Claude, and bequeathed his picture to the National Gallery, on condition that it should hang for ever between two pictures by Claude to challenge their superiority. Opinions are divided as to the rank of Turner's 'Carthage,' so when you go to the National Gallery, you must look at them both and prepare to form a preference. Turner was incited to this rivalry with Claude by the popularity that painter enjoyed among English collectors of the day, who were less eager to buy Turner's great oil-paintings than those of his predecessor. Incidentally this rivalry was the origin of the great series of etchings executed by or for him, known as _The Book of Studies (Liber Studiorum)_. This book was suggested by Claude's _Libri di Verita_, six volumes of his own drawings (of pictures he himself had painted and sold) made in order to identify his own, and detect spurious, productions. But Turner's book was designed to show his power in the whole range of landscape art. The drawings were carefully finished productions, work by which he was willing to be judged, and many of them he etched with his own hands. His favourite haunts, the abbeys of Scotland and Yorkshire, the harbours of Kent, the mountains of Switzerland, the lochs of Scotland, and the River Wye, he chose as illustrating his best power over architecture, sea, mountain, and river. He repeated several of the same subjects later in oils, such as the pearly hazy 'Norham Castle' in the Tate Gallery.